Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
339 AM AST Tue Sep 2 2025

.KEY MESSAGES...

* An increase in low-level moisture and warmer temperatures will
exacerbate heat indices in north-central areas and southern coastal
plains. Given the expected conditions, an extreme heat warning
is in effect from 10 AM to 5 PM AST today.

* For today, there is a elevated flood and lightning threat
along the northwestern Puerto Rico from 12 to 5 PM AST.

* For the upcoming weekend, a tropical wave, combined with an upper-
level trough, will increase the potential for showers and
thunderstorms, increasing the flood threat.

* For the U.S. Virgin Islands, variable weather conditions will
persist, with warm temperatures expected through the upcoming weekend.
The arrival of a tropical wave is anticipated to increase
shower frequency across the islands.

&&

.SHORT TERM...Today through Thursday...

Clear to partly cloudy skies prevailed across the islands during the
overnight hours. Scattered showers with isolated thunderstorms were
noted mainly over the northwestern waters of Puerto Rico, and the
Anegada Passage just before midnight. Showers are expected to move
over portions of the USVI and the eastern sections of PR through the
rest of the early morning hours. Minimum temperatures were from the
upper-70s to low 80s across the lower elevations of the islands to
the mid-60s and 70s across the higher elevations of Puerto Rico. The
wind was light with an easterly component.

A broad surface high pressure over the central Atlantic and front
across the northwestern Atlantic will continue to promote light to
moderate (10-15 kt) southerly steering winds through Wednesday.
These winds will bring a surge in low-level moisture from the
southeastern Caribbean today. Meanwhile, an upper-level low north of
the area will move southwest, just north of Hispaniola by Wednesday,
promoting colder 500 mb temperatures and increasing instability in
general, which will aid in the development of strong afternoon
thunderstorms each day. A tropical wave will cross the region late
on Thursday, bringing scattered showers and thunderstorms across the
regional waters and over portions of the islands late in the
forecast period.

At least through Wednesday, a similar weather pattern is expected,
with showers increasing in and around the U.S. Virgin Islands and
across the east/southeast sections of Puerto Rico during the morning
hours. This will then be followed by afternoon thunderstorm
development over portions of the interior and the northwestern
quadrant of PR, as well as downwind from el Yunque area and over
portions of the Cordillera. The main weather hazards will be urban
and small stream flooding, strong gusty winds, and lightning
strikes. In addition, the light southeasterly winds will continue to
promote hot temperatures across the lower elevations of the islands,
and heat advisory conditions are expected before the onset of
afternoon showers.

On Thursday, winds are expected to shift more from the east,
remaining around 15 kt as the weak tropical wave moves across the
region. The best moisture associated with the wave will arrive late
in the day. Therefore, fair weather conditions are expected during
the morning hours across the islands, with afternoon showers and
thunderstorm development over portions of the Cordillera and western
PR, and downwind of the islands.

.LONG TERM...Friday through Tuesday...

The long-term forecast remains on track. According to the latest
global model guidance for Friday, the islands will be mostly
dominated by a broad surface high pressure over the central
Atlantic. Under this pattern, sufficient cloudiness and moisture
will support a typical weather regime, with variable conditions in
the morning followed by afternoon convection. An increase in
showers and thunderstorms is forecast from late Friday into the
weekend, as an upper-level trough near 250 mb enhances instability
across the region. This feature, combined with abundant tropical
moisture from a tropical wave, will favor stronger convection with
frequent lightning, gusty winds, and periods of heavy rainfall.
Based on the Gálvez-Davison Index (GDI), there is a high chance of
widespread showers and thunderstorm activity each afternoon
through the weekend. This activity is expected to range from
moderate to intense, leading to urban and low-lying flooding.
Additionally, the threat of lightning will increase, particularly
across the western interior and the San Juan metro area. From
Monday to Tuesday, moisture will diminish and an upper-level ridge
will erode the instability over the region. As a result, a more
typical weather pattern is expected, with afternoon convection
across the islands.

The presence of moisture and 0–3 km winds will enhance the heat
threat across all coastal and urban areas during the long-term
period. These warmer conditions could exacerbate heat-related
illness symptoms associated with heat exhaustion. Residents and
visitors are urged to follow the recommendations issued by the
health department.


&&

.AVIATION...

(06z TAFs)

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hour. However, afternoon TSRA could develop near
TJBQ/TJSJ between 02/17-23Z, causing tempo MVFR to brief IFR
conditions. Elsewhere, mostly VCSH expected. Southeast winds
expected between 10-15 kt with sea breeze variations and higher
gusts aft 02/14z.

&&

.MARINE...

A surface high pressure over the central Atlantic will continue to
result in moderate to locally fresh east to southeasterly winds
across the local waters. Seas will remain up to 5 feet across the
Atlantic offshore waters and even lower across the coastal waters.
Localized hazardous marine conditions due to thunderstorms are
forecast from late Friday into Sunday as a tropical wave moves
into the local waters, resulting in an increase in cloudiness and
showers.

&&

.BEACH FORECAST...

There is a low risk of rip currents along all the coastal areas
of Puerto Rico, Culebra, Vieques and the U.S. Virgin Islands.
Therefore, coastal conditions are suitable for beachgoers and
visitors. Although conditions remain good stay alert to areas not
designated to beachgoers.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
358 AM AST Wed Sep 3 2025

.KEY MESSAGES...

* For today, another warm day is expected, with heat indices
reaching up to 111 degrees across coastal and urban areas, and
even higher in localized areas during the peak of the heat from
11 AM to 2 PM AST. Additionally, there is an elevated flooding
and lightning threat across western Puerto Rico due to the
afternoon convection.

* For the upcoming weekend, a tropical wave and an upper-level
trough will increase the potential for showers and
thunderstorms increasing the flood and lightning threat.

* For the U.S. Virgin Islands, variable weather conditions will
persist, with warm temperatures expected through the upcoming
weekend.

* There is a low risk of rip currents across the islands today.

&&

.SHORT TERM...Today through Friday...

Partly cloudy skies were observed across the east/southern sections
of Puerto Rico and the U.S. Virgin Islands during the overnight
hours. Passing showers where increasing over the regional waters
under light steering southeasterly winds. These showers are expected
to move over portions of the USVI and eastern sections of PR through
the rest of the early morning hours. Minimum temperatures were from
the upper-70s to low 80s across the lower elevations of the islands
to the mid-60s and mid-70s across the higher elevations of Puerto
Rico.

A surge in moisture will continue over the area today, triggering
showers and thunderstorms once again over the islands and across the
local waters. These thunderstorms can produce heavy rainfall, strong
gusty winds, and frequent cloud-to-ground lightning as an upper-
level low meanders just west of the area. Light to moderate
southeast winds will prevail under the influence of a surface high
pressure centered just southwest of the Azores and a frontal system
across the western Atlantic. Therefore, another hot day is expected
before the onset of afternoon showers, and a Heat Advisory will be
in effect from 10 AM to at least 5 PM, for all coastal
municipalities of Puerto Rico and the U.S. Virgin Islands.

For Thursday and Friday, the surface high pressure will continue to
build over the central Atlantic, and easterly trades will return
across the eastern Caribbean. A drier air mass ahead of a tropical
wave will move over the local area on Thursday, causing the
precipitable water (PWAT) content to drop from near 2.00 inches
today to around 1.60 inches by Thursday morning. Therefore, mostly
fair weather conditions are expected to prevail across the islands
in general; however, intense daytime heating, combined with the
available moisture content and local effects, will trigger shower
activity over western PR in the afternoon hours, where the flood
threat will remain elevated. Temperatures will remain a few degrees
above normal under mostly sunny skies during the late morning hours,
and the heat threat will continue across most coastal and urban
areas of the lower elevations of the islands. By Friday, shower and
thunderstorm activity will increase across the islands as the PWAT
recovers to near 2 inches again with the passage of the tropical
wave. Also, a weak Saharan Air Layer with minor concentrations of
Saharan dust will arrive late Friday, promoting hazy skies.

.LONG TERM...Saturday through Wednesday...

The long-term forecast remains on track, with the island mostly
dominated by a broad surface high pressure over the central
Atlantic for the first part of the period.At the surface, sufficient
cloudiness and moisture from an induced surface trough from an
upper level trough moving westward into the region. This weather
configuration will lead a typical weather pattern along the
islands with afternoon convection across the northern Puerto
Rico. On Sunday, winds will veer more from the east- southeast as
the surface high pressure shifts into the northwestern Atlantic,
while instability increases further as 500 mb temperatures drop to
-8 C, favoring more widespread thunderstorms due to the approach
of the upper level low along the northeast of the region. Based on
the Galvez- Davison Index (GDI), there is a high chance of
widespread showers and thunderstorm activity each afternoon
through the weekend, ranging from moderate to intense, with
frequent lightning, gusty winds, and periods of heavy rainfall
that could lead to urban and low- lying flooding. The threat of
lightning will be particularly elevated across the western
interior and the San Juan metro area.

From Monday to Tuesday, a deep layer of tropical moisture between
700 and 300 mb will place the islands under a wetter pattern,
increasing the frequency of showers. Combined with some
instability aloft and temperatures around -5 to -6 C at 500 mb,
this will favor rounds of showers across the islands. The pattern
would include frequent passing showers during the morning hours
along windward sections and a deep layer of cloudiness from late
morning into the afternoon, enhancing convective activity.
Additionally, the presence of deep moisture and southeasterly low-
level winds will continue to enhance the heat threat across
coastal and urban areas, potentially exacerbating heat-related
illness symptoms associated with heat exhaustion. For Wednesday,
discrepancies in global model solutions (GFS & ECMWF) remain due
to the uncertainty of the next tropical system, which currently
has a high chance of formation in the next seven days according to
the NHC. The GFS favors surface winds from the east-southeast,
while the European model (ECMWF) indicates a more easterly flow.
This pattern should become clearer as we approach the weekend;
however, for now, the forecast calls for active afternoon
convection along western Puerto Rico.

&&

.AVIATION...
(06z TAFs)

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hour. However, afternoon +SHRA/TSRA expected to
develop in and around TJBQ/TJSJ between 03/16-22Z, causing tempo
MVFR to brief IFR conditions. Elsewhere, mostly VCSH expected,
however, VCTS is expected at TJPS through the afternoon hours. East
to southeast winds will increase between 10 and 15 knots with sea
breeze variations and higher gusts after 03/13z.

&&

.MARINE...

A surface high pressure across the central Atlantic will continue
to promote moderate to locally fresh east to southeasterly winds
across the local waters today, with seas generally up to 4 feet,
calmer near the coast, and occasionally higher in and around
thunderstorms. Strong convection developing through this evening
will result in moderate chop, gusty winds, and localized hazardous
seas, reducing visibility in heavy rainfall. Conditions are
expected to deteriorate by late Friday night into the weekend as a
tropical wave increases the frequency of showers and
thunderstorms, leading to periods of locally hazardous marine
conditions, with small craft operators advised to exercise
caution.

&&

.BEACH FORECAST...

There is a low risk of rip currents along all coastal areas today
through the upcoming weekend. Coastal conditions will be generally
favorable for beachgoers and visitors. However, despite the good
conditions, caution is advised as other coastal hazards such as
lightning, especially during the afternoon hours, may pose a
threat.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
430 AM AST Thu Sep 4 2025

.KEY MESSAGES...

* Another warm day is expected today, with heat indices up to 111
degrees across coastal and urban areas, and potentially even
higher in localized areas during peak heating from 11 AM to 2
PM AST.

* Afternoon convection with thunderstorms will trigger an
elevated threat of flooding and a limited lightning threat
across northwestern Puerto Rico.

* An increase in moisture and instability will induce a wet and unstable
pattern from Friday into Monday, increasing the flood threat
and the lightning threat along the islands.

* For the U.S. Virgin Islands, variable weather conditions will
persist, with warm temperatures expected through the upcoming
weekend.

* There is a low risk of rip currents across the islands today
and into the upcoming weekend.

&&

.SHORT TERM...Today through Saturday...

Mostly clear to partly cloudy skies were observed across the islands
overnight. Passing showers where noted mainly over the regional
waters under light steering easterly winds, with a few reaching
portions of eastern PR, where the Doppler radar estimated around a
quarter of an inch of rain in Humacao and vicinity. Minimum
temperatures were from the mid-70s to low 80s across the lower
elevations of the islands to the low-60s and mid-70s across the
higher elevations of Puerto Rico.

A broad surface high pressure will continue to build over the
central Atlantic during the next few days, promoting moderate trade
winds through the forecast period. Embedded in this flow today is a
drier air mass with precipitable water (PWAT) values below
climatology, which will move across the region. However, shallow
moisture content trapped below 850mb will be sufficient to aid in
the development of afternoon showers and thunderstorms over western
PR. Across the USVI, passing showers could move at times,
particularly tonight through Friday morning, as shower activity is
expected to increase ahead of a tropical wave currently located east
of the Leeward Islands. Temperatures will remain similar to
yesterday, with daytime highs ranging from the upper 80s to low 90s
across most coastal areas. Heat indices will peak around 108°F,
mainly across western and northern PR. Regardless, due to plenty of
sunshine expected elsewhere, a Heat Advisory was issued for all
coastal municipalities in PR and the USVI.

The tropical wave is expected to cross the local area on Friday,
resulting in an increase in shower and thunderstorm activity through
the region. The PWAT is likely to recover at normal levels, around
2.00 inches, which is the high end of the 50th percentile. The main
hazards will be urban and small stream flooding, as well as gusty
winds and lightning strikes with the thunderstorms. Although hot
temperatures are still expected on Friday, the cloud cover and
showers could limit the heat threat in certain areas. A weak Saharan
Air Layer with minor concentrations of Saharan dust will arrive with
the wave passage, bringing hazy skies and affecting people sensitive
to these particles.

On Saturday, unstable conditions will continue across the region as
an upper-level low north of the area and associated trough combine
with lingering low-level moisture from the departing wave. The flood
threat will remain elevated, with possible isolated flash floods and
mudslides in areas of steep terrain, particularly across western PR.

.LONG TERM...Sunday through Thursday ...

The forecast for the first part of the long-term remains on track.
An upper-level low, just north of the region, will continue to
increase the instability aloft and induce colder temperatures at
500 Mb, ranging from -6 to -7°F. Meanwhile, at the surface, plenty
of tropical moisture will move with Precipitable water (PWAT)
ranging between 1.8 to 2.0 inches will move into the area,
increasing the potential for shower activity. As a result, the
islands will experience a showery pattern from morning hours
across the windward section of the islands, and widespread
activity across western Puerto Rico in the afternoon hours.
Especially across northwestern Puerto Rico, where there is a
potential for scattered thunderstorms as the Galvez-Davison Index
(GDI suggests. Instability will remain in place from Monday into
Wednesday as the upper-level low/trough extends from another area
over the Western Caribbean. This upper-level feature will induce a
surface trough, resulting in plenty of cloudiness and moisture
along the islands. At the surface, winds will predominate from the
east-southeast as a surface high-pressure system over the central
Atlantic dominates the area. This wind flow will push the sower
activity along the San Juan metro area and northwestern sections
of Puerto Rico.

For Thursday, the forecast remain with a lot of uncertainty due
to two different solutions from the global model guidances (GFS &
ECMWF). According to the latest data, there are some discrepancies
in the weather patterns along the islands and the surface winds
due to the approach of the next tropical system monitored by the
National Hurricane Center, with a high chance of formation in the
next seven days. According to the GFS and with consistency, the
tropical system will move northeast of the region, resulting in
mostly east-southeast winds across the islands. On the other hand,
the ECMWF, with different solutions from yesterday, located the
system slightly closer to the islands for the weekend. Although
the long-term forecast only includes the Thursday forecast,
residents and visitors are urged to check the tropical emergency
plans and stay tuned for further official information regarding
this tropical wave.

&&

.AVIATION...
(06z TAFs)

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hour. However, locally induced TSRA is expected
to develop in and around TJBQ between 04/16-22Z, causing tempo MVFR
to brief IFR conditions. Elsewhere, mostly VCSH expected. East winds
will increase between 10 and 15 knots with sea breeze variations and
higher gusts after 04/13z.


&&

.MARINE...

A surface high pressure across the central Atlantic and an induced
surface trough just northeast of the islands over the Atlantic
will continue to promote moderate to locally fresh east to
southeasterly winds across the local waters today, with seas
generally up to 5 feet. Afternoon showers will result in choppy
seas, gusty winds, and localized hazardous seas, reducing
visibility in heavy rainfall.

Weather conditions are expected to deteriorate by late Friday
night into the weekend as a wet and unstable weather pattern
increases the frequency of showers and thunderstorms, leading to
periods of locally hazardous marine conditions

&&

.BEACH FORECAST...

There is a low risk of rip currents along all coastal areas today
through the upcoming weekend. Coastal conditions will be generally
favorable for beachgoers and visitors. However, despite the good
conditions, caution is advised as other coastal hazards like
lightning, especially during the afternoon hours.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
424 AM AST Fri Sep 5 2025

.KEY MESSAGES...

* Another warm day is expected today, with heat indices climbing
up to 111 degrees across coastal and urban areas, and
potentially even higher in localized areas during peak heating.

* A tropical moisture with an induced surface trough will
increase the potential for shower activity along the islands
from Friday into the weekend.

* For the U.S. Virgin Islands, variable weather conditions will
persist, with warm temperatures expected through the upcoming weekend.
From Saturday into Sunday, a showery pattern is expected
mostly for the morning and evening hours across the islands;
however, no flooding threat is forecast.

* The National Hurricane Center is monitoring a tropical wave
(Invest 91L) with a high chance of formation in the next seven days.
For now, there is a lot of uncertainty in the outcome of the
forecast related to this tropical system; however, residents
and visitors should stay tuned for further updates from the
official sources.

&&

.SHORT TERM...Today through Sunday...

A tropical wave located across the Anegada Passage and Caribbean
waters will increase shower and thunderstorm activity today across
the islands. These showers could lead to minor flooding across
portions of the U.S. Virgin Islands during the later morning/early
afternoon hours. The flood threat across Puerto Rico will be
elevated, particularly across the eastern interior and western
sections of Puerto Rico during the afternoon hours. These
thunderstorms can produce brief gusty winds and cloud-to-ground
lightning strikes. A weak Saharan Air Layer with minor
concentrations of Saharan dust will arrive with the wave passage,
bringing hazy skies and reducing the air quality somewhat through at
least Saturday.

For the rest of the weekend, unstable conditions will persist across
the region as an upper-level low, located north of the area, and its
associated trough combine with lingering low-level moisture from the
departing wave. The flood threat will remain elevated, with possible
isolated flash floods and mudslides in areas of steep terrain,
particularly across western Puerto Rico. For the USVI, passing
showers will continue to move at times, with isolated thunderstorms
mainly developing over the regional waters.

Although cloudiness will increase during the day due to the expected
showers, the heat threat will remain elevated in general for all
lower elevations of the islands through the forecast period.
Particularly between the late morning and early afternoon hours, and
before the onset of afternoon showers. Heat advisories could be
issued each day.

.LONG TERM...Sunday through Thursday ...

The forecast for the first part of the long-term remains on track.
An upper-level low just north of the region will continue to
increase instability aloft and induce colder temperatures at 500
Mb, ranging from -6 to -7°C. Meanwhile, at the surface, plenty of
tropical moisture with Precipitable Water (PWAT) values ranging
between 1.8 to 2.0 inches will move into the area, increasing the
potential for shower activity. As a result, the islands will
experience a showery pattern from morning hours across the
windward section of the islands, and widespread activity across
western Puerto Rico in the afternoon hours, especially across
northwestern Puerto Rico, where there is a potential for scattered
thunderstorms as the Galvez-Davison Index (GDI) suggests. From
Wednesday into Thursday, instability will increase again as
another upper-level trough moves south of the region, favoring
colder temperatures near -7°C at 500 Mb. This feature, combined
with PWAT values near the 75th percentile, will support enhanced
cloudiness and frequent showers and thunderstorms across the
islands. At the surface, east-southeast winds driven by high
pressure over the central Atlantic will prevail, steering
additional convection toward the San Juan metro area and the
northwestern sections of Puerto Rico.

From late Thursday into Friday, the forecast becomes more
uncertain due to the approach of a tropical system track by the
National Hurricane Center, and with a high chance of formation
(90%) in the area. Differences remain in the global model guidance
(GFS and ECMWF), particularly in the position and the intensity
of the system. The latest GFS run suggests a more southerly track,
aligning with the ECMWF, which continues to place the system
closer to the islands and therefore capable of altering local
weather conditions. Given the length of the forecast period,
additional changes are still possible. For now, the most certain
course of action is for residents and visitors to review their
tropical emergency plans and remain tuned to official updates from
the National Hurricane Center.

&&

.AVIATION...

(06z TAFs)

A tropical wave will increase SHRA/TSRA across the local area today.
Tempo MVFR to brief IFR conditions are possible at TISX/TIST btw
05/12z-18z, and across the PR terminals btw 05/16z-06/00z. HZ due to
minor concentrations of Saharan dust expected after the wave
passage, but VSBY should remain P6SM. East winds will increase
between 12 and 16 knots with sea breeze variations and higher gusts
after 05/13z.

&&

.MARINE...

A surface high pressure across the central Atlantic, a tropical
wave, and an induced surface trough just northeast of the islands
over the Atlantic will continue to promote moderate to locally
fresh east-southeasterly winds across the local waters today, with
seas generally up to 5 feet. Conditions are expected to
deteriorate by late Friday night into the weekend as a wet and
unstable weather pattern increases the frequency of showers and
thunderstorms, leading to periods of locally hazardous marine
conditions, with small craft operators advised to exercise
caution.

&&

.BEACH FORECAST...

There is a low risk of rip currents along all coastal areas today
through the upcoming weekend. Coastal conditions will be generally
favorable for beachgoers and visitors. However, despite the good
conditions, caution is advised as other coastal hazards like
lightning, especially during the afternoon hours.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
516 AM AST Sat Sep 6 2025

.KEY MESSAGES...

* Unsettled conditions will continue for the rest of the weekend,
with the most active periods expected during the afternoons and
evenings across Puerto Rico and the U.S. Virgin Islands.

* For the U.S. Virgin Islands, warm to hot conditions will
continue through the next few days.

* The National Hurricane Center continues to monitor Invest 91 over
the Central Tropical Atlantic. Residents and visitors should
continue to closely monitor official updates in the coming days.

&&

.SHORT TERM...Today through Monday...

The departing tropical wave interacting with the mid to upper-level
trough promoted showers and thunderstorms across the regional
waters, with some of them moving inland across the US Virgin Islands
and the windward locations of PR. Winds were mainly from the east-
southeast at 5 to 10 mph, but locally higher in and near rain
activity. Minimum temperatures were warmer than normal overnight,
especially across the urban and coastal areas, from the upper-70s to
low 80s.

We expect another day with muggy heat indices between 100 and 111
degrees Fahrenheit across many urban and coastal sites in the US
Virgin Islands and Puerto Rico, due to the warmer-than-normal low
temperatures and the above-normal moisture content associated with
the departing tropical wave. However, the tropical wave trailing
moisture interacting with the lingering mid to upper-level trough
will promote another active afternoon, especially downwind from the
US Virgin Islands, Vieques, and Culebra. The activity will then form
downwind from El Yunque into the San Juan Metropolitan Area and
along the Cordillera Central, as well as to the north and west of
it. Thunderstorm activity will also promote gusty winds and frequent
lightning. The downpours will promote a slight to elevated flooding
risk across these locations, especially during the afternoon.

Residents and visitors are encourage to monitor the evolution of the
weather conditions, as a Heat Advisory might be required if the
expected rain activity and subsequent cloud cover do not form.

A trade wind perturbation will result in a showery Sunday across the
region. Showers will move across the local waters, moving inland
over the windward locations of the US Virgin Islands and Puerto Rico
overnight and early Sunday morning. Then, heat indices will reach
values around 110 degrees Fahrenheit again in the mid-morning and
afternoon. The excessive heating combined with sea breezes and local
effects will then promote strong afternoon convection along the
Cordillera Central and western PR, as well as across the southeast
coast and San Juan Metropolitan area. The activity is also expected
to be felt downwind from the US Virgin Islands, where ponding of
water could impact the west end. Moisture content will slowly erode
on Monday. However, the typical hydrological pattern involves AM
passing showers across the windward locations, followed by strong
afternoon convection across the western locations, due to various
factors, such as excessive heating.

&&

.LONG TERM...Tuesday through Friday...

Changes were introduced to the long-term forecast, with uncertainty
remaining high for the second part of the next workweek. Based on
satellite-derived products, ahead of Invest91L, there’s a dense
Saharan Air Layer (SAL) likely to approach the local islands by
Tuesday. From the latest model guidance, Precipitable Water (PWAT)
values should drop to well below climatological normal (around 1.5
inches). Additionally, relative humidity in the low and mid levels
should plummet to below normal as well, with 850 - 700 mb lapse rate
below the 10th percentile (< 5.0 C/km). Although the shower activity
may be triggered due to daytime heating and local effects, deep
convection should be limited. As for the Saharan Dust, low to
moderate concentrations may bring hazy skies, reduced visibility,
and deteriorated air quality.

The National Hurricane Center continues to monitor Invest 91L, but
from the latest Tropical Weather Outlooks (TWOAT), has lowered the
formation chance in the past 24 hours. In the 05/06z Tropical
Weather Outlook (TWOAT), Invest AL91 had a 60% formation chance
through 48 hours (medium) and 90% through 7 days (high). From the
latest TWOAT, the system has a 30% (low) chance in the next 48 hours
and 60% (medium) chance for the next 7 days due to a drier air mass
that is limiting shower and thunderstorm activity, unfavorable for
cyclonic development. Nevertheless, AL91 it's still likely to
upgrade to a tropical depression early to the middle part of next
week. According to the latest deterministic guidance, global
models continue to disagree and fail to reach a consensus on the
potential trajectory and intensity of the system. While the ECMWF
projects the system moving northeast of the region, GFS is
currently positioning the tropical wave south of the CWA.
Nevertheless, the grand ensemble maintains PWAT values above
climatological normal (2.0 - 2.2 inches), as moisture content
should gradually increase by late Tuesday. With plenty of tropical
moisture, the frequency of showers and thunderstorms will likely
increase across the islands, affecting mainly windward sections
during the morning. Taking into account SE winds, daytime heating,
and local effects, convection activity should develop over the
mountain ranges and northwestern portions of Puerto Rico.

At the moment, the flooding risk will remain limited to elevated
over the aforementioned areas, nevertheless, this may change over
the next few days as the weather pattern will depend mostly on the
development of Invest AL91. Interest in Puerto Rico and the U.S.
Virgin Islands should continue to monitor the progress of this
system.

&&

.AVIATION...

(06Z TAFs)

Mainly VFR conds are expected across al terminals during the fcst
period. However, tropical moisture will promote SHRA/TSRA across the
local area today. VCTS are likely across TJSJ/TJBQ/TIST/TISX thru
06/23Z (especially btwn 06/16-23z). Tempo MVFR to brief IFR conds
are possible across TJSJ/TJBQ aft 06/16Z. Expect calm to light and
VRB winds thru 06/13z, then from the E-ESE at 10-15 kt with sea
breeze variations thru 06/23Z. Then, becoming light and variable
thru 07/13Z.

&&

.MARINE...

The trailing moisture of a tropical wave moving into the central
Caribbean, interacting with a mid to upper level trough will promote
showers and thunderstorms across the regional waters today. The
surface high pressure across the Central Atlantic, promoting moderate
to locally fresh easterly winds will result in moderate chops to
choppy conditions this weekend into early next week. The National
Hurricane Center is monitoring Invest 91L over the central tropical
Atlantic. While a drier air mass is limiting the potential for
development, this system is likely to be near the Lesser Antilles by
the middle to latter part of next week. Mariners should remain
attentive to forecast updates in the coming days.

&&

.BEACH FORECAST...

No major changes were introduced to the beach forecast. Beaches
across the CWA continue under a low risk of rip currents, expected
to continue through early next week. Although the risk remains low,
isolated stronger rip currents may occur in the vicinity of groins,
jetties, reefs, and piers. Besides rip currents, beachgoers must
also stay aware of the weather conditions across the area,
particularly in the afternoons and evenings, due to shower and
thunderstorm activity that may approach the surf zone. Beachgoers
must leave the water and seek shelter if thunderstorms are close by.
The National Hurricane Center continues to monitor Invest AL91 over
the central tropical Atlantic. Although uncertainty remains high
regarding the trajectory and intensity of the system, interest
should continue to monitor the progress of this system.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
445 AM AST Sun Sep 7 2025

.KEY MESSAGES...

* An elevated risk of flooding will continue to prevail today
across much of Puerto Rico as a trade wind perturbation moves
across the forecast area.

* For the U.S. Virgin Islands, although passing showers and
thunderstorms may lead to ponding of water on roads today, the
main hazard is the heat risk with heat indices exceeding 100
degrees F.

* Across Puerto Rico and the U.S. Virgin Islands, the heat
indices may briefly meet or exceed 108°F today; nevertheless,
under easterly winds and cloudiness associated with the passing
perturbation, most of the time must remain below the Heat
Advisory Criteria.

&&

.SHORT TERM...Today through Tuesday...

An easterly perturbation interacting with a nearby mid to upper
level trough aided in showers and thunderstorms across the regional
waters, and some of them moved inland across the US Virgin Islands
and the north and east coastal sections of PR. Winds were mainly
from the east-southeast at 5 to 10 mph, but locally higher in and
near rain activity. Minimum temperatures finally dropped into the
mid- to upper 70s along the coastal areas, to the low to mid-60s in
the mountains and valleys.

The muggy heat indices will continue today, with maximum values
around 107°F or even higher, especially in locations without
sufficient cloud cover or rainfall activity. The proximity of a mid
to upper-level trough and an easterly perturbation will result in an
unstable weather pattern with showers and thunderstorms across the
US Virgin Islands and Puerto Rico today. Although the western and
interior portions of PR will observe little to no rain in the
morning, we anticipate the showers and thunderstorms now affecting
the Virgin Islands and east and north locations of PR moving further
inland into those locations from mid-morning onward. Therefore, the
principal hazards expected for today are thunderstorm activity and
flooding rains. Additionally, during the last few days, we have been
receiving reports of sudden mudslides and landslides across portions
of the interior of PR; thus, any persistent heavy rain across steep
terrains along the Cordillera Central could result in sudden
landslides. Please remain aware of your surroundings and understand
the risk for your community.

Above-normal tropical moisture will continue to move across the
region on Monday. This moisture, combined with the warmer-than-
normal sea surface temperatures, will aid in the formation of
scattered to numerous showers across the regional waters overnight
and early Monday morning. This activity will move inland across the
US Virgin Islands and the windward locations of PR occasionally. The
muggy heat indices will continue on Monday, and maximum heat indices
will remain in the mid-100s or near 110 degrees Fahrenheit in the
afternoon. The combination of the diurnal heating, the moisture
content, local effects, and sea breezes will give place to another
round with strong thunderstorms by Monday afternoon. However, a
relatively drier air mass could slowly decrease the coverage of the
most intense activity by Monday evening into Tuesday. This drier air
mass will arrive across the region with low concentrations of
Saharan dust particles. However, the typical hydrological pattern
involves AM passing showers across the windward locations, followed
by strong afternoon convection across the western locations, due to
various factors, such as excessive heating.

.LONG TERM...Wednesday through Sunday...

A weakening in the mid-level ridge pattern is expected early in
the cycle as trofiness develops northeast of the local islands.
However, by the end of the cycle, the mid-level ridging will
return. At lower levels, a surface high pressure will prevail
across the tropical Atlantic, promoting east- southeast winds.
Based on the latest grand ensemble, precipitable water is expected
to remain above 2.0 inches from Wednesday through Friday, with a
sharp decrease anticipated over the upcoming weekend as the
developing mid-level ridge erodes the available moisture. The
highest values of precipitable water early in the forecast cycle
coincide with the passage of a tropical wave (former Invest 91L)
currently located near the 40W.

Under this evolving pattern, the highest chance of showers and
thunderstorms is expected on Wednesday and Thursday, with a
transition on Friday and into the weekend. Having said this, the
intensity and coverage of showers and thunderstorms are expected
to decrease by the end of the workweek, resulting in a more
seasonal pattern with afternoon showers and thunderstorms
primarily focused on the western areas of Puerto Rico. As a
result, the flooding risk remains elevated throughout the forecast
period, decreasing somewhat by the upcoming weekend.

Maximum temperatures will continue to range in the upper 80s to
mid 90s with heat indices exceeding 100 degrees F under the
prevailing east southeast wind flow. Therefore, the heat risk
will remain elevated for much of the forecast cycle. Some
haziness is anticipated Wednesday and Thursday.

&&

.AVIATION...
(06Z TAFS)

Brief reductions in VIS/CIGs due to SHRA/TSRA are possible across
JSJ/IST/ISX through this afternoon, resulting in brief MVFR/IFR.
Then SHRA/TSRA will spread into the interior and W-PR btwn 07/15-
23z, affecting JPS/JBQ. Expect calm to light/VRB winds thru 07/13z.
Aft 07/13Z, winds will return from the ESE at 10-15 kt but locally
higher in and near TSRA. Streamer downwind from the USVI or El
Yunque could also affect ISX/IST and TJSJ, respectively.

&&

.MARINE...

A surface high pressure across the Central Atlantic will promote
moderate to locally fresh easterly winds, resulting in moderate chops
through the middle of the week. An easterly perturbation will
continue to promote showers and thunderstorms across the regional
waters today and tomorrow. Then, a tropical wave is expected to move
near the islands around Wednesday, increasing local winds and
potentially triggering showers and thunderstorms again.

&&

.BEACH FORECAST...

A low risk of rip currents will continue to prevail across all
shorelines. Nevertheless, isolated stronger rip currents may
occur in the vicinity of groins, jetties, reefs, and piers.
Beachgoers must also stay aware of the weather conditions across
the area, particularly in the afternoons and evenings, due to
thunderstorm activity that may approach the surf zone. Beachgoers
must leave the water and seek shelter if thunderstorms are close
by.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
436 AM AST Mon Sep 8 2025

.KEY MESSAGES...

* A trade wind perturbation will continue to promote showers and
thunderstorms across the regional waters, moving inland across
the US Virgin Islands and windward sections of PR, leading to
ponding of waters on roadways.

* Afternoon convection will promote strong thunderstorms and an
elevated risk of flooding across mainland PR.

* Warm temperatures will continue across urban and coastal
locations in the US Virgin Islands and Puerto Rico, worsening
between Tuesday and Thursday with the arrival of a drier air
mass carrying Saharan dust particles.

* A tropical wave is expected to increase the potential for
widespread showers and thunderstorms around Wednesday.

&&

.SHORT TERM...Today through Wednesday...

Skies have been variably cloudy with frequent passing showers across
the eastern third of Puerto Rico, Vieques, Culebra, and the US
Virgin Islands. Rainfall totals associated with these showers ranged
between 1 and 3 inches across east and southeast Puerto Rico. Winds
were mainly from the east-southeast at 5 to 10 mph, but higher in
showers. Minimum temperatures were in the mid- to upper 70s along
the coastal areas, to the low to mid-60s in the mountains and
valleys.

A mid-level ridge pattern is expected to strengthen across the
northeast Caribbean as a trough moves further west. Nevertheless,
this pattern is expected to be short-lived as a TUTT develops across
the central Atlantic into the northeast Caribbean by midweek. The
building ridge pattern will promote moisture erosion late today and
into Tuesday. However, precipitable water values are expected to
quickly rise on Tuesday night into Wednesday with the passage of a
tropical wave (formerly Invest 91L), currently located near 45W. At
lower levels, a surface high-pressure system across the central
Atlantic will continue to yield moderate east-southeast winds
through the forecast cycle.

Having said that, continue to expect passing showers and isolated
thunderstorms across eastern Puerto Rico and the outlying islands
early today, with the frequency decreasing by the afternoon and
early evening hours as a somewhat drier air mass moves over the
northeast Caribbean. Across western Puerto Rico, showers and
thunderstorms are expected to develop by midday, and prevailing
across the northwest quadrant through at least the late afternoon
hours. On Tuesday, showers and thunderstorms are expected over
Mayaguez and vicinity. The chance for showers and thunderstorms
likely to increase late Tuesday into Wednesday as the aforementioned
tropical wave reaches the eastern Caribbean. Saharan dust particles
are expected to accompany this tropical wave; resulting in hazy
skies Tuesday and Wednesday.

Under this evolving pattern the primary hazard today is an elevated
risk of flooding across much of Puerto Rico, followed by a limited
risk tomorrow. The heat risk will remain limited today increasing
Tuesday onwards.

.LONG TERM...Thursday through Monday...

A mid-to-upper-level trough will linger off to the northeast of
the USVI, near the Leeward Islands, inducing occasional easterly
perturbations that will arrive across our region from Thursday to
Saturday. Then, a mid-to-upper-level high-pressure system will
build from the northeast into our islands between Sunday and early
next week, strengthening the trade wind cap and promoting dry air
with subsidence aloft. What this weather pattern means to us,
residents and visitors of the USVI and PR, we can expect the
arrival of more frequent surges of moisture in the second part of
the week, followed by a more stable weather pattern on Sunday and
early next week. However, due to the excessive heating that has
been prevailing locally, strong afternoon convection will be
likely each day, especially across the western locations of PR,
and downwind from the USVI. Additionally, nighttime cool air
advection due to above-normal sea surface temperatures will result
in scattered to numerous showers, especially during the second
part of the week.

Additionally, model guidance suggests the arrival of a Saharan
Air Layer with low concentrations of suspended particles on
Wednesday and Thursday, and possibly Friday. This air mass will
play an essential role in terms of the amount of rain that we
might observe across Puerto Rico and the US Virgin Islands. On the
other hand, if concentrations are not high enough to inhibit rain
activity, we might observe periods with enhanced thunderstorm
activity due to the presence of suspended particles.

Maximum temperatures are projected to range from the upper 80s to
the mid-90s, with heat indices potentially exceeding 100 degrees
Fahrenheit, attributed to the existing east-southeast wind
patterns. Consequently, the risk associated with heat will remain
elevated throughout the forecast period, particularly between
Wednesday and Thursday, when warmer-than-normal overnight low
temperatures due to the haziness attributed to the SAL are
anticipated.

&&

.AVIATION...
(06Z TAFS)

Brief periods of MVFR conditions are possible at USVI TAF sites, as
well as TJSJ and TJPS in SHRA, early this morning. After 09/16Z,
TSRA/SHRA is expected to develop across north and northwest Puerto
Rico, leading to brief periods of MVFR conditions at TJSJ and TJBQ
through about 09/22Z. Sfc winds E 10-15 kt with sea breeze
variations and ocnl hir gusts.

&&

.MARINE...

A surface high pressure across the Central Atlantic will promote
moderate to locally fresh east to southeast winds, resulting in
moderate chops through the middle of the week. An easterly
perturbation will continue to promote showers and thunderstorms
across the regional waters today. Then, a tropical wave is
expected to move near the islands by Wednesday, increasing the
local winds and the potential for showers and thunderstorms.
Induced surface troughs will swing by the islands, pooling
additional moisture in the second part of the week.

&&

.BEACH FORECAST...

Beachgoers, please exercise caution across some of the north and
east-facing beaches in PR and St Croix, as the risk of rip
currents will become moderate through the middle of the week.

Additionally, thunderstorms could develop, especially in the
afternoon or overnight hours, so remember to seek shelter if you
hear thunder, either by going indoors or finding a safe place.

Marine guidance is suggesting the risk to turn low for the second
part of the week. Although the risk for rip currents is low, life-
threatening rip currents often occur in the vicinity of groins,
jetties, reefs, and piers—exercise caution.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
425 AM AST Tue Sep 9 2025

.KEY MESSAGES...

* Residents and visitors in the US Virgin Islands and Puerto Rico
can expect excessive heat that will affect most individuals
sensitive to heat, especially those without effective cooling
and/or adequate hydration, especially in all low-urban and
coastal areas.

* Shower and thunderstorm activity will increase after mid-
morning as an induced surface trough moves from the east into
the region, elevating the risk of flooding rain and frequent
lightning.

* We expect the enhancement of showers and thunderstorms across
the US Virgin Islands and Puerto Rico as a tropical wave arrives
late tonight into Wednesday.

* Warm to hot heat indices will persist across urban and coastal
locations in the US Virgin Islands and Puerto Rico, worsening
the second part of the workweek with the arrival of a Saharan
Air Layer.

&&

.SHORT TERM...Today through Thursday...

Fair weather conditions prevailed overnight across the local
islands, with minimal rainfall activity observed. Minimum
temperatures ranged from the mid- to upper 70s along the coastal
areas.

The short-term forecast remains on track. A mid-level ridge pattern
will erode by the end of the cycle as a TUTT establishes northeast
of the region. At lower levels, east-southeast winds are expected to
prevail as a surface high remains in place across the central
Atlantic. Additionally, an induced surface trough is expected to
move across the forecast area today, followed by the passage of a
tropical wave tomorrow. As the induced surface trough moves across
the northeast Caribbean later today, the moisture content is
expected to increase, exceeding 2.0 inches by the afternoon hours.
This will result in variable and showery weather across the U. S.
Virgin Islands and eastern Puerto Rico later today.

During the afternoon hours, the available moisture will combine with
diurnal heating and local effects to result in showers and
thunderstorms across central and northwest Puerto Rico. On
Wednesday, a somewhat wetter pattern is expected as the tropical
wave (formerly Invest 91L) moves across the local islands, resulting
in another round of showers and thunderstorms. Based on the latest
guidance, a more seasonal pattern is anticipated on Thursday, with
shower and thunderstorm activity mainly focused across the western
areas of Puerto Rico. As a result, the risk for flooding will remain
elevated mainly across Puerto Rico through at least Wednesday.

Under the east southeast wind flow, warm to hot temperatures are
expected to persist across Puerto Rico and the U.S. Virgin Islands
during the forecast period. Therefore, continue to expect heat index
values reaching or exceeding 108 degrees Fahrenheit each day along
the lower elevations and urban areas. Additionally, Saharan dust
particles are expected to be present across the local area,
resulting in hazy skies on Wednesday and Thursday.

.LONG TERM...Friday through Tuesday...

Model guidance continues to suggest the mid-to-upper-level trough
lingering off to the northeast of the USVI, near the Leeward
Islands, inducing occasional easterly perturbations that will
arrive across our region through at least Saturday. Then, a mid-
to-upper-level high-pressure system will build from the northeast
into our islands between Sunday and early next week, strengthening
the trade wind cap and promoting dry air with subsidence aloft.
Monday and Tuesday, tropical moisture from easterly perturbations
will be moving across the Northeast Caribbean, enhancing shower
and thunderstorm activity.

Residents and visitors of the USVI and PR should prepare for more
frequent surges of moisture arriving on Friday and Saturday. This
will be followed by a more stable weather pattern from Sunday to
Monday morning. After that, a tropical wave is expected to
increase shower and thunderstorm activity, particularly during the
afternoon and evening hours on Monday and Tuesday.

Some factors that could promote strong afternoon convection,
particularly in the western regions of Puerto Rico and downwind
from the US Virgin Islands, are the excessive heating that we are
forecasting, as well as the lingering Saharan Air Layer with low
to locally higher concentrations in the area (especially on
Friday). Additionally, the nighttime cool air advection over the
above-normal sea surface temperatures will lead to scattered to
numerous showers, especially during the latter part of the week.

Once again, warmer-than-normal maximum and minimum temperatures
could extend the potential to observe excessive heating each day,
with heat indices potentially exceeding 100 degrees Fahrenheit,
attributed to the existing east-southeast wind patterns.
Consequently, the risk associated with heat will remain elevated
throughout the forecast period.

&&

.AVIATION...
(06 TAFs)

Mostly VFR conditions are expected to prevail at all TAF sites early
in the morning. However, Aft 09/13z brief periods of MVFR conditions
will remain possible at the USVI TAF sites as well as JSJ and JBQ.
Sfc winds east to east southeast 10-15 kt with sea breeze variations
and higher gusts are expected.

&&

.MARINE...

A surface high pressure across the central Atlantic and a front over
the western Atlantic will promote light to moderate east to
southeast winds through the end of the week. An induced surface
trough will move across the region today, followed by a tropical
wave on Wednesday. Therefore, showers and thunderstorms will
increase across the regional waters through midweek. These
thunderstorms could bring squally weather and locally higher seas.

&&

.BEACH FORECAST...

An increasing risk of rip currents is expected today into Wednesday
along the north facing beaches of Puerto Rico and Saint Croix. Keep
in mind, life threatening rip currents are always possible in the
surf zone and in the vicinity of jetties, reefs and piers.
Additionally, beachgoers must also stay aware of the weather
conditions across the area, particularly in the afternoons and
evenings, due to thunderstorm activity that may approach the surf
zone. Beachgoers must leave the water and seek shelter if
thunderstorms are close by.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
449 AM AST Wed Sep 10 2025

.KEY MESSAGES...

* A Heat Advisory is in effect for the urban and coastal areas of
the US Virgin Islands and Puerto Rico, as well as the valleys of
the eastern interior.

* Strong thunderstorms will develop this afternoon mainly across
PR's northwest quadrant, elevating the risk of flooding rain and
frequent lightning.

* The US Virgin Islands can expect a mixture of sunshine and
clouds with little or no rain through the rest of the week.

* Warm to hot heat indices will persist across urban and coastal
locations in the US Virgin Islands and Puerto Rico, worsening
the second part of the workweek with the arrival of a Saharan
Air Layer.

* Beachgoers, there is a moderate risk of rip currents for the
exposed north and east-facing beaches of Puerto Rico and St
Croix.

&&

.SHORT TERM...Today through Friday...

Calm weather conditions prevailed overnight across the islands, with
few showers observed over the local waters. Minimum temperatures
were seen in the upper 70s to the low 80s in the coastal and urban
areas of the islands, and from the upper 60s to low 70s in the
mountains.

Today, warm temperatures in combination with moisture associated
with a weak tropical wave (former Invest 91L) will result in showers
and isolated thunderstorms across Puerto Rico and the U.S. Virgin
Islands. The latest precipitable water content guidance (PWAT) has
values between 1.80 to 2.05 inches, with the highest values between
mid-morning and late afternoon. The "El Yunque" streamer is expected
to develop too, affecting mostly the San Juan metropolitan area and
adjacent municipalities. Meanwhile, across the U.S. Virgin Islands
mainly fair weather will prevail with the potential to observe
showers from time to time, particularly during the morning hours.

By tonight into Thursday, after the wave departure, slightly drier
conditions will return into the area along with low to moderate
concentrations of Saharan dust particles. However, despite the
presence of the Saharan dust, convective activity is expected each
afternoon over portions of western and northwestern Puerto Rico. As
a result, there is a limited to elevated flooding risk across
portions of Puerto Rico through at least the weekend; whereas the
flooding risk for the U.S. Virgin Islands will remain low.

The 925 mb temperature will remain above-than-normal for the next
few days, which in turn suggest warmer than normal surface
temperatures. Additionally, the available tropical moisture
combined with the warmer trend will sustain an elevated heat
threat for the short- term forecast.

.LONG TERM...Saturday through Wednesday...

Model forecasts indicate that a mid-to-upper-level trough will
remain positioned to the northeast of the US Virgin Islands
(USVI), close to the Leeward Islands. This setup will generate
occasional easterly disturbances that will pass over our region
throughout the weekend. Subsequently, a mid-to-upper-level high-
pressure system is expected to build in from the northeast, likely
between Sunday and Monday. This development will enhance the
trade wind cap and introduce dry air with subsidence aloft.

Late Monday night into Tuesday, a tropical wave is predicted to
move into the Northeast Caribbean, which will increase moisture
levels and stimulate shower and thunderstorm activity.
Additionally, by the middle of next week, a mid-to-upper-level
trough will approach the area, interacting with the lingering
tropical moisture between Wednesday and Thursday.

Under the weather pattern explained above, residents and visitors
in the US Virgin Islands and Puerto Rico can expect excessive heat
that will affect most individuals sensitive to heat, especially
those without effective cooling and/or adequate hydration,
particularly in low-urban and coastal areas, each day through at
least Monday. However, the predominantly wind pattern will bring
occasional surges of moisture arriving on Saturday and early
Sunday. Then, by Sunday and Monday, a stable weather pattern and a
somewhat drier air mass will limit rain activity. Meanwhile,
strong afternoon convection will form each day across the interior
and western sections. The best chance to observe widespread
convective activity is between Tuesday and Thursday, associated
with Tuesday's tropical wave, followed by the lingering mid to
upper-level trough interacting with abundant tropical moisture on
Wednesday and Thursday.

&&

.AVIATION...
(06Z TAFs)

Mainly VFR conditions are expected to prevail at all TAF during the
fcst period. However, SHRA/TSRA may result in brief periods of MVFR
conds at TJSJ/TJBQ/TJPS aft 10/13Z. Mountain obsc and lower ceilings
are possible, especially with the heaviest rains. VCSH will remain
possible at the TIST/TISX thru 10/23Z. Winds will prevail from the
southeast 10-15 kt with sea breeze variations and higher gusts aft
10/14Z.

&&

.MARINE...

A surface high pressure across the central Atlantic and a front over
the western Atlantic will promote light to moderate east to southeast
winds through the end of the week. A weak tropical wave will move
near the region, enhancing showers and thunderstorms across the
regional waters today. These thunderstorms could bring squally
weather and locally higher seas.

&&

.BEACH FORECAST...

Attention beachgoers: Exercise caution on the exposed north- and
east-facing beaches in Puerto Rico and St. Croix, as there is a
moderate risk of rip currents today and tomorrow. Additionally,
thunderstorms may develop, particularly in the afternoon or
overnight. If you hear thunder, please seek shelter by going
indoors or finding a safe location.

Marine guidance indicates that the risk will decrease to low for
the weekend. Although the risk of rip currents is low, life-
threatening currents often occur near groins, jetties, reefs, and
piers—exercise caution. It might become moderate Monday and
Tuesday next week.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
250 AM AST Thu Sep 11 2025

.KEY MESSAGES...

* Very hot temperatures are expected to prevail in the upcoming days
across the local islands.

* Lots of sunshine, hot temperatures, and only a few passing
showers at times are expected across the U.S. Virgin Islands.

* Active afternoons are anticipated for the interior and western
Puerto Rico, where the risk of urban and small stream flooding is
elevated.

* Low to moderate concentrations of Saharan dust particles will
continue to result in hazy skies and reduced visibilities across
the region through at least Friday.

&&

.SHORT TERM...Today through Saturday...

A strong thunderstorm persisted most of the night over the Mona
Channel. Additionally, some light showers made it to the vicinity of
the Virgin Islands, while others reached eastern Puerto Rico.
Rainfall accumulations were not significant. Temperatures were on
the warm side for the south and east of Puerto Rico, and across the
Virgin Islands, mostly in the low 80s. Temperatures were cooler in
the mountains, mostly in the mid-60s and low 70s.

The islands in the U.S. Caribbean are in between two upper level
troughs, one to the northeast, and another now over southeastern
United States. In the middle, there is an upper level ridge. This
will act to weaken the trade winds, coming out of the SE at 10-12
kts today, and below 10 knots for Friday and Saturday. At the
surface, some Saharan dust lingers, with skies looking a bit hazy.
In general, the pattern looks seasonal in terms of moisture and
instability for the region, hence with strong diurnal heating,
another active afternoon is anticipated for the interior and western
Puerto Rico. Rainfall is not favored for eastern Puerto Rico or for
the Virgin Islands, where mostly sunny to partly cloudy skies should
prevail.

Tomorrow and on Saturday, with the upper level trough just northeast
of the region, some induced showers and thunderstorms are expected
to form over the Atlantic waters. Most of the activity should remain
over waters, but the trade winds should carry some of these showers
over the Virgin Islands, Vieques and Culebra. Flooding is not
expected, but some wet roads are likely at times. The main
difference is that with lighter winds, the rain that forms across
the Cordillera Central and western Puerto Rico should last longer,
and drift toward the coastal areas of northwestern and north-central
Puerto Rico. Also, it is likely that showers also stream from El
Yunque into portions of the San Juan metro area, where the risk for
urban and small stream flooding is elevated. Lightning and gusty
winds could also be threat within the thunderstorms. For the Virgin
Islands, some showers may also develop in the western coast of St.
Croix and St. Thomas, but the probability of precipitation is lower,
and these showers should not cause significant flooding problems,
although water surges in the drainage guts cannot be ruled out.

Last but not least, temperatures are expected to remain well above
normal through the weekend, with 925 mb values over two standard
deviation above the climatological mean. Therefore, heat indices
will impact anyone without effective cooling or adequate hydration.
The users should avoid strenuous activities outdoor, look for shade
when possible, and take plenty of breaks. Also, it is important to
look out for sensitive groups and also to keep in mind the impacts
the heat may have on pets as well.

.LONG TERM...Sunday through Thursday...

A wet pattern is on the way for the islands. An upper-level trough
northeast of the region will bring showers and thunderstorms on
Sunday. By Monday, a tropical wave will move over the islands,
bringing more activity across Puerto Rico and the U.S. Virgin
Islands.

The latest precipitable water content guidance (PWAT) indicates
values of 1.90 to 2.20 inches through late Monday. Following this, a
mass of drier air will quickly move in, bringing stable conditions
through the middle of the week. By late Tuesday and into Wednesday,
a second tropical wave will approach the U.S. Virgin Islands and
Puerto Rico. This wave, combined with moisture and instability from
a nearby upper-level trough, will result in periods of moderate to
heavy showers and thunderstorms across the region. The U.S. Virgin
Islands can expect showers and few isolated thunderstorms,
particularly during the morning hours. Then, afternoon convective
activity is expected across central and northwestern Puerto Rico
through the early evening hours. Under these conditions, there is
a limited to elevated risk for urban and small stream flooding,
as well as lightning across the islands.

The 925 mb temperature will remain above-than-normal throughout
the period. Highs will remain in the upper 80s to low 90s along
the coastal and urban areas of the islands, to the low 80s in the
higher elevations. Residents and visitors are advised to monitor
the weather conditions and plan accordingly if having outdoor
activities under sun exposure.

&&

.AVIATION...
(06Z TAFs)

Mainly VFR conditions expected to prevail through the forecast
period. SHRA will move at times across TJSJ and USVI terminals, but
impacts to operations are expected to be minimal, if any. After 17Z,
SHRA and TSRA are expected across the western Cordillera Central and
TJBQ. Periods of reduced VIS and low ceilings are anticipated. Winds
will be from the SE at 10-12 kts, with stronger gusts.

&&

.MARINE...

A surface high pressure across the central Atlantic and a front over
the western Atlantic will promote light to moderate east to southeast
winds through the end of the week. Moderate concentrations of Saharan
dust particles will be present in the area through today, slightly
decreasing visibilities.

&&

.BEACH FORECAST...

Beachgoers, there is a moderate risk of rip currents for the
northern and east-facing beaches of Puerto Rico and St. Croix this
afternoon, tonight, and Thursday. Additionally, isolated
thunderstorms may develop each afternoon. If you hear thunder,
please move to a safer place indoors.

The risk is expected to decrease to low by Friday and into the
weekend. Although the risk of rip currents will be low, life-
threatening currents can still occur near groins, jetties, reefs,
and piers, so exercise caution. The risk is expected to increase
to moderate again early next week.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
359 AM AST Fri Sep 12 2025

.KEY MESSAGES...

* Afternoon showers and thunderstorms are expected for central and
western Puerto Rico, due to the abundant moisture and diurnal
heating effects.

* For the U.S. Virgin Islands; warm temperatures and mainly fair
weather conditions will prevail today, under mostly sunny to
partly cloudy skies.

* Hot temperatures will persist during the next several days
across the region. A Heat Advisory is in effect from 10 AM to 4
PM AST for the urban and coastal areas of Puerto Rico, Vieques,
Culebra, and all of the U.S. Virgin Islands.

* There is a low risk of rip currents for all beaches of the local
islands.

&&

.SHORT TERM...Today through Sunday...

Mostly tranquil conditions were observed during the night hours
across the islands. Some showers managed to reach St. John and
southeastern Puerto Rico, but accumulations were not significant.
Skies were mostly clear, with some high clouds moving in.
Temperatures were just a tad cooler than yesterday, but still in the
low 80s in the Virgin Islands, and in the 70s in Puerto Rico.

A couple of troughs, one to the northeast, and one well northwest of
the islands will maintain the trade winds weaker for today and
Saturday. In general, the mornings will be mostly pleasant, with
passing showers reaching the Virgin Islands, Vieques and Culebra and
eastern Puerto Rico at times, although no significant rainfall
accumulation is anticipated. In the afternoon, near normal moisture
levels and strong diurnal heating will lead to another active
afternoon. Showers and thunderstorms are expected to develop along
the Cordillera Central, and with a weak steering flow, these showers
will then spread into the west and northwest of Puerto Rico, as well
as over portions of the San Juan metro area. Showers could also fire
up in the western portions of St. Croix, streaming toward the
Caribbean Sea. The highest risk of flooding is for the interior,
northwest, and the San Juan metro area, where urban and small stream
flooding could develop. Also, frequent lightning and gusty winds are
expected within the strongest thunderstorms.

Some drier air is expected early on Sunday, leading to fair weather
for most of the northeast Caribbean, but then a tropical wave will
approach the Virgin Islands, with a higher chance of showers in the
vicinity of Saint Croix in the afternoon hours. The moisture field
of the wave will spread westward, also increasing the frequency of
showers for the rest of the Virgin Islands and eastern Puerto Rico.
Winds will increase too, coming from the east southeast at speeds of
20 to 25 mph.

Temperatures at 925 mb are just a tad cooler than yesterday, but
still, well above normal heat indices will prevail. A Heat Advisory
is in effect for most of Puerto Rico and all of the Virgin Islands.
A Heat Advisory means that people sensible to heat will be affected,
especially those without effective cooling or adequate hydration.

.LONG TERM...Monday through Friday...

A tropical wave is forecast to move over Puerto Rico and the U.S.
Virgin Islands, bringing increased moisture and a high likelihood of
showers and thunderstorms. The latest precipitable water guidance
indicates normal to above-normal values (2.00 to 2.25 inches),
suggesting a wet pattern will persist through Tuesday. The U.S.
Virgin Islands should anticipate showers and isolated thunderstorms,
particularly from the morning into the afternoon. In Puerto Rico,
showers and isolated thunderstorms are expected over the eastern
municipalities during the morning, with afternoon convective
activity shifting to the western and northwestern municipalities due
to a combination of daytime heating and local effects.

This wet trend is expected to continue from Wednesday through the
rest of the week, as an upper-level trough located northeast of the
region moves southeast. A second tropical wave approaching the area
will combine with the available moisture from the upper-level-
trough, further enhancing the potential for additional showers and
thunderstorms across the islands. Therefore, the risk of excessive
rainfall leading to urban and small stream flooding remains
elevated. There is also a limited risk of frequent lightning
accompanying the strongest thunderstorms.

Despite the expected weather for the long-term period, the 925 mb
temperature is expected to remain above-normal at the beginning of
the week. However, as the week progresses, temperatures will become
slightly cooler due to the increased rainfall. Highs will generally
be in the mid to upper 80s along coastal and urban areas, and in the
upper 70s to low 80s in the higher elevations. Residents and
visitors are advised to monitor weather conditions and plan any
outdoor activities accordingly for the upcoming week.

&&

.AVIATION...
(06Z TAFs)

Mainly VFR conditions expected to prevail. SHRA will move in the
vicinity of the USVI terminals, but limited, if any, impacts to
operations are expected. After 17Z, another round of strong
convection is expected for the Cordillera Central, reaching TJSJ
and TJBQ at times. Periods of reduced VIS and low ceilings are
expected as well. Winds will be lighter, out of the ESE at 7-11
kts.

&&

.MARINE...

A surface high pressure across the central Atlantic and a front over
the western Atlantic will promote light to moderate east to southeast
winds through the weekend. Afternoon showers and thunderstorms are likely
each day, particularly over the northwestern coastal waters of
Puerto Rico and over the Mona Passage.

&&

.BEACH FORECAST...

A low risk of rip currents is expected to continue through the
weekend. However, even with a low risk, life- threatening rip
currents can still occur near groins, jetties, reefs, and piers,
so beachgoers are advised to exercise caution at all times. The
rip current risk is forecast to increase to moderate again by
early next week. Additional hazards include: isolated afternoon
thunderstorms and an elevated to significant heat risk. Remember:
if you hear thunder, seek shelter indoors immediately, and be sure
to stay well hydrated.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
337 AM AST Sun Sep 14 2025

.KEY MESSAGES...

* A couple of tropical waves will increase the frequency of
showers and thunderstorms through much of the workweek. This
will the risk of flooding elevated. Additional threats include
rapid river rises, landslides, and frequent lightning.

* The Virgin Islands will also see an increase in showers and
thunderstorms, with water surges along the drainage guts,
ponding of water on roadways, and occasional lightning and
landslides.

* Weather will likely improve later in the week and into next
weekend, but it will be very hot again for Puerto Rico and the
Virgin Islands. These heat indices will be affecting anyone
without effective cooling or adequate hydration.

* The risk of rip currents will be moderate for most of the
workweek. Also, there is a risk of lightning strikes each
afternoon across most of the local beaches in Puerto Rico and
the Virgin Islands.


&&

.SHORT TERM...Today through Tuesday...

Overnight, relatively calm weather conditions prevailed, with
isolated showers moving across local waters and passages. Some of
these showers reached parts of the U.S. Virgin Islands and eastern
Puerto Rico, resulting in minimal accumulations. Low temperatures
were in the upper 70s to low 80s in coastal and urban areas, and
from the upper 60s to low 70s in the mountains.

A tropical wave east of the U.S. Virgin Islands is forecast to move
over the local islands today. The associated moisture field will
begin to enter the area this morning, with precipitable water values
exceeding 1.90 inches and potentially reaching 2.30 inches later in
the afternoon. For the U.S. Virgin Islands, Vieques, and Culebra,
showers will gradually increase during the morning, with isolated
thunderstorms developing in the afternoon. In Puerto Rico, afternoon
convective activity is expected to produce heavy rainfall and
thunderstorms across central and western municipalities, spreading
toward the northwestern and northern parts of the island. Streamer
activity from "El Yunque" will also impact the San Juan metro area
and adjacent municipalities this afternoon. This activity could lead
to urban and small stream flooding, rapid river rises, water surges,
and landslides. The strongest thunderstorms are expected to bring
frequent lightning and gusty winds. With soils already saturated
from previous rainfall, the risk of flooding will remain from
limited to elevated across the area for the next few days. Residents
and visitors are advised to continue monitoring weather conditions
throughout the weekend and plan accordingly, especially in flood-
prone areas.

By Monday, an atmospheric disturbance will arrive, promoting another
round of unstable weather. This disturbance has precipitable water
values up to 2.35 inches, which will support another day of strong
showers and thunderstorms. Areas previously affected by heavy rain
may experience additional flooding and rapid river rises. The 925 mb
temperatures are expected to remain at or above-normal for the
period. Highs will be in the mid to upper 80s along coastal and
urban areas, and in the upper 70s to mid 80s in higher elevations.

.LONG TERM...Wednesday through Sunday...

A tropical wave crossing Puerto Rico and the Virgin Islands, along
with an upper level trough will maintain unsettled weather
conditions through Thursday. Precipitable water values are
expected to be at 2.0 to 2.25 inches, which is about one standard
deviation above normal for mid-September. These features will
maintain the probability of precipitation on the high side. Since
afternoons have been so active, soils are already saturated and
rivers are running high, especially along the interior and western
Puerto Rico. Therefore, it is very likely that urban and small
stream flooding will continue, each day. Also, rivers may reach
flood stage too, while landslides, lightning strikes and gusty
winds could also develop. Showers will also reach eastern Puerto
Rico at times, and although soils are not as saturated, impacts
should be similar. Across the Virgin Islands, periods of showers
and thunderstorms will cause water surge along guts and drainage
channels, with ponding of water on roadways and isolated urban
flood.

Moving into Friday and the weekend, the attention shifts toward
the system being monitored by the National Hurricane Center. So
far, the guidance shows this tropical wave developing and moving
toward the northwest before reaching the northeastern Caribbean.
As the system moves, it will push some drier air into the islands,
so weather conditions should improve, at least in terms of rain.
The thing is that although it will not be as wet, winds should
shift from the southeast, and 925 mb temperature values will soar,
going nearly two standard deviation above normal. As a result,
very hot temperatures will come back, with the likelihood of
experiencing Heat Advisory or Extreme Heat Warning conditions.
This level of heat will impact anyone without effective cooling or
adequate hydration.


&&

.AVIATION...
(06z)

Mainly VFR to brief MVFR conds across all terminals during the fcst
period. A tropical wave is expected to move into the area today
promoting VCSH/VCTS over TIST/TISX/TJSJ thru 14/23Z. SHRA/TSRA will
gradually increase over TJBQ/TJPS aft 14/17Z. Reduced VIS, mountain
obsc and low cigs expected thru 14/23Z. Sfc winds from the ESE at 10-
14 kts, with higher gusts and sea breeze variations aft 14/14Z.

&&

.MARINE...
A surface high-pressure located over the central and eastern Atlantic
is interacting with a frontal boundary in the Western Atlantic,
resulting in light to moderate east-southeasterly winds through
tomorrow. An approaching tropical wave will move over the U.S.
Virgin Islands and Puerto Rico today, increasing the likelihood of
showers and thunderstorms. After the tropical wave passes, local
winds will shift to moderate and occasionally fresh as the high-
pressure tightens the local pressure gradient. Another tropical wave
is expected to move through the area around Tuesday.

&&

.BEACH FORECAST...
The risk of life-threatening rip currents will increase to moderate
beginning Sunday and persist through most of the workweek, particularly
for northern and eastern exposed beaches of Puerto Rico and Saint
Croix in the U.S. Virgin Islands.

Even with a low risk, life-threatening rip currents can still occur
near groins, jetties, reefs, and piers, so beachgoers are advised to
exercise caution at all times.

Additionally, thunderstorms are likely during the afternoon hours,
producing dangerous lightning strikes; be prepared to seek shelter
if thunder is heard.

&&

.HYDROLOGY...

Active afternoons have maintain the soils saturated across most of
the interior and western half of Puerto Rico. These periods of
heavy rain has also maintain the rivers at above normal to much
above normal levels. These unsettled weather pattern is expected
to persist through much of the workweek, as moisture remains above
normal due to a couple of approaching tropical waves.

Since soils are saturated, much of the precipitation will quickly
become excessive runoff, causing urban or flash flooding, water
surges along rivers, rivers going above flood stage, and
landslides too.

The rivers across the eastern third of Puerto Rico are not as
full, but these rivers usually react much faster than the river in
the west, hence, periods of heavy rain will likely result in rapid
river rises as well.

For the Virgin Islands, periods of heavy rain will cause water
surges along drainage guts, and ponding of water on roadways.
Urban flooding could develop too, while landslides in areas of
steep terrain cannot be ruled out.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
505 AM AST Mon Sep 15 2025

.KEY MESSAGES...

* A trade wind perturbation today and a tropical wave combined
with a TUTT low expected around mid week, will increase the
frequency of showers and thunderstorms throughout much of the
workweek. As a result, the risk of flooding will remain
elevated. Additional hazards include rapid river rises,
landslides, and frequent lightning.

* The Virgin Islands will also experience an increase in showers
and thunderstorms, potentially leading to water surges in
drainage guts, ponding on roadways, occasional lightning, and
isolated landslides.

* Increasing heat risk is forecast again toward the end of the week
and into the weekend. A limited heat risk is expected today and
over the next few days.

* A moderate risk of rip currents is in effect for the northern
and eastern beaches of Puerto Rico, as well as Culebra and St.
Croix today. A low risk is expected in other areas. Similar
conditions are likely to continue through most of the workweek.

&&

.SHORT TERM...Today through Wednesday...

Conditions were mostly tranquil during the night hours across the
local islands. Some clouds reached southeastern Puerto Rico, but
otherwise, it was mostly clear. A few showers formed in the vicinity
of the Virgin Islands, reaching St. Croix late in the overnight
hours. A low level perturbation, located just to the east of the
Virgin Islands will cross the local area today. So far, the most
recent precipitable water satellite-derived product indicate values
around 2.2 inches, which is just over one standard deviation
above normal. Once the moisture field reaches Puerto Rico this
afternoon, it will combine with strong diurnal heating to produce
showers and thunderstorms. The activity will be occasional across
the Virgin Islands, where water surges along guts can be
anticipated. For the interior, east, west, and the San Juan metro
area in Puerto Rico, there is a risk of flooding, landslides,
water surges along rivers, gusty winds and lightning strikes. By
the evening hours, as the disturbance departs, showers will become
less frequent, but will still move occasionally across the east
of Puerto Rico and over the Virgin Islands.

On Tuesday, drier air will filter in, but only at the mid-levels.
Moisture at the surface will be enough for an additional round of
afternoon showers, mostly as streamers coming out of St. Croix, St.
Thomas and Culebra, and from El Yunque into the interior. Another
cluster of showers and thunderstorms is anticipated for western
Puerto Rico.

By Wednesday, a stronger tropical wave will approach the region,
along with an upper level low staying north of the island. Shower
and thunderstorm are expected to increase in coverage and intensity
than today, with a higher risk of flooding. It is worth mentioning
that even though the rain is not expected to cover all areas, or to
be raining all day, those areas that have received heavy rain in the
last couple of days will be especially prone to urban and river
flooding, as well as landslides in steep terrain. Flash flooding
cannot be ruled out either. Also, it is important to consider the
risk of gusty winds and lightning strikes within the thunderstorm.
The users should avoid flood prone areas, and seek shelter if
thunder is heard.


.LONG TERM...Thursday through Monday...

By Thursday, unsettled weather conditions are expected to prevail
due to the combined influence of a tropical wave and a TUTT low
moving across Puerto Rico and the Virgin Islands. Latest model
guidance suggests precipitable water (PWAT) values will remain
above normal for this time of year—ranging between 2.0 and 2.25
inches. These atmospheric features will maintain high rain chances
and enhance thunderstorm development, supported by 500 mb
temperatures near average for mid-September. As a result, urban
and small stream flooding is likely to persist daily, and some
rivers may reach flood stage. In the Virgin Islands, periods of
showers and thunderstorms are expected to cause water surges along
guts and drainage channels, ponding on roadways, and isolated
urban flooding. Additional hazards include landslides, frequent
lightning, and gusty winds.

By Friday, drier air is forecast to move into the region, decreasing
PWAT values to near normal levels, and dropping further to below
normal over the weekend and into early next week. Rainfall
activity will diminish, but localized afternoon convection,
particularly in northwestern Puerto Rico, will still be possible
due to local effects and diurnal heating. As cloud cover decreases
and rain subsides, winds will shift from the southeast, and 925 mb
temperatures are forecast to peak at nearly two standard deviations
above normal, especially on Friday and Saturday. This pattern
will elevate the heat risk across the region. Heat Advisories or
even Extreme Heat Warnings may be issued. Residents and visitors
are strongly advised to stay hydrated, avoid prolonged sun
exposure during peak heat hours, and take extra precautions,
particularly those without access to adequate cooling or hydration.
This forecast scenario assumes the current guidance remains
consistent for the tropical wave being monitored by the National
Hurricane Center, which currently has a 30% chance of formation in
the next 48 hours and an 80% chance over the next 7 days. If
development continues as expected, the system may track
northwestward toward the northeastern Caribbean. We will continue
to monitor this closely and provide updates throughout the
workweek.

&&

.AVIATION...
(06Z TAFs)

SHRA and TSRA will be on the increase today, reaching the USVI
terminals after 12Z. Brief periods of reduced VIS and low ceilings
is expected here. For the PR terminals, after 15Z, SHRA and TSRA
will cause mountain obscuration across the Cordillera Central, and
will likely result in longer periods of reduced VIS. Winds at FL050
will be at 15-23 kts, with stronger gusts.

&&

.MARINE...

A surface high pressure system located over the central and eastern
Atlantic, in combination with an approaching low-level perturbation,
will promote moderate to locally fresh east to southeasterly winds
today. Small craft are urged to exercise caution across the regional
waters. The trade wind perturbation that will cross the region
today, will also increase the likelihood of showers and thunderstorms
across the waters and local Caribbean passages. A stronger tropical
wave is expected to approach by midweek, enhancing shower
coverage.

&&

.BEACH FORECAST...

Today, there is a moderate risk of rip currents across the north and
east-facing beaches of Puerto Rico, Culebra, and St. Croix. Similar
conditions are expected to prevail most of the workweek so beachgoers
are advised to exercise caution at all times as a moderate risk
means life-threatherning rip current are possible in the surf
zone. A low risk should prevail elsewhere. Additional hazards
include afternoon thunderstorms. Remember: if you hear thunder,
seek shelter inside of a safer place immediately.

&&

.HYDROLOGY...

The disturbance that will move in today, and the tropical wave
coming in on Wednesday will maintain the risk of flooding elevated
for most of the area in Puerto Rico and the Virgin Islands. The
latest Root Soil Saturation product from PRAGWATER, and also from
the National Water Model shows saturated soils along the western
half of Puerto Rico, and also for the extreme east and southeast.
Also, the 7-day average streamflow from the USGS show that many
rivers are running near normal or well above normal. Therefore, it
is likely that any upcoming rain will quickly turn into runoff,
enhancing the risk of flooding, rapid river rises, and landslides.

For the Virgin Islands, periods of heavy rain will cause water
surges along drainage guts, and ponding of water on roadways.
Urban flooding could develop too, while landslides in areas of steep
terrain cannot be ruled out.

Although an elevated flood risk is shown everyday of the week, the
higher risk is on Wednesday and Thursday due to the above normal
moisture from the tropical wave and increased instability aloft from
an upper level low. Conditions will begin to improve by Friday.

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
501 AM AST Tue Sep 16 2025

.KEY MESSAGES...

* A departing perturbation will result in passing showers this
morning, followed by afternoon convection over the interior
and western to southwestern Puerto Rico.

* A tropical wave combined with an upper-level trough, will
increase the frequency of showers and thunderstorms particularly
Wednesday and Thursday. As a result, the risk of flooding will
remain elevated.

* The Virgin Islands will also experience an increase in showers
and thunderstorms, potentially leading to water surges in
drainage guts, ponding on roadways, occasional lightning, and
isolated landslides.

* A Heat Advisory is in effect today across coastal and urban
areas of Puerto Rico, as well as Vieques, Culebra and the
Virgin Islands. Increasing heat risk is forecast again toward
the end of the week and into the weekend.

* There is a moderate risk of rip currents across the northern
and eastern beaches of Puerto Rico, as well as Culebra and St.
Croix today. A low risk is expected in other areas.

&&

.SHORT TERM...Today through Thursday...

Showers and thunderstorms moved across the region overnight,
affecting the northeastern half of Puerto Rico, the U.S. Virgin
Islands, and the local islands, with some activity brushing the
northern coast. Radar shows peak rainfall near 1 inch in
southeastern Rio Grande and along the coast from Vega Baja to
Vega Alta. Overnight lows stayed warm in eastern Puerto Rico, the
U.S. Virgin Islands, and the local islands (80–82°F), while the
central interior cooled into the mid-60s. Winds were mostly light
and variable, with brief gusts near thunderstorms.

A departing tropical wave will leave enough moisture in place, and
marginal instability will continue to support showers and a few
thunderstorms this morning, mainly affecting windward areas. This
afternoon, heat and moisture will fuel stronger thunderstorms across
the western interior and western Puerto Rico. These storms may bring
heavy rainfall, localized flooding, lightning impacts, and gusty
winds. With soils already saturated from recent rains, the risk of
flash flooding and landslides in steep terrain is elevated.
Temperatures will remain very hot, with a Heat Advisory in effect
from 10 AM to 5 PM for coastal and urban areas of Puerto Rico,
Vieques, Culebra, and the U.S. Virgin Islands.

Another tropical wave will cross the eastern Caribbean tonight into
Wednesday, with abundant moisture lingering through Thursday. At the
same time, an upper-level trough will make the atmosphere more
favorable for thunderstorm development, especially Wednesday into
Thursday. Lighter winds midweek will cause showers and storms to
move more slowly, increasing the risk of flooding impacts across a
broader area. With plenty of heat and moisture in place, expect
active showers and thunderstorms, while clouds and rain may bring
occasional relief from the persistent dangerous heat.


.LONG TERM...Friday through Tuesday...

For Friday and Saturday, the upper-level trough will weaken,
allowing a weak mid-level high pressure to slightly dominate. The
latest model guidance suggests that precipitable water (PWAT)
values will remain within the normal range for this time of year,
ranging from 2.0 inches on Friday and decreasing to 1.5 inches by
Saturday. Expect afternoon showers and isolated thunderstorms
fueled by diurnal heating and local effects. As a result, urban
and small stream flooding is likely to persist each day, and some
rivers may reach flood stage. In the Virgin Islands, periods of
showers and thunderstorms are expected to cause water surges along
guts and drainage channels, ponding on roadways, and isolated
urban flooding. Additional hazards include landslides, frequent
lightning, and gusty winds.

This forecast scenario assumes that the current guidance remains
consistent regarding the tropical wave being monitored by the
National Hurricane Center, which currently has an 80% chance of
formation in the next 48 hours and a 90% chance over the next
seven days. If development continues as expected, the system may
track northwestward toward the northeastern Caribbean. We will
continue to monitor this closely and provide updates throughout
the workweek.

Sunday through Tuesday should be the more stable days of the
forecast period, with 500 mb temperatures warming to above normal,
around -5 to -4 degrees Celsius. Drier air is forecast to move
into the region, with below normal PWAT values persisting through
Tuesday (1.5 inches or lower). Rainfall activity will diminish,
but localized afternoon convection, particularly in the western
sectors of Puerto Rico, will still be possible due to local
effects and diurnal heating. Winds will be very light, so showers
will be very slow moving, and the flood risk will remain mostly
limited. By Tuesday night, another tropical wave is expected to
approach the area, further increasing moisture and bringing better
chances for rain onward.

In terms of temperatures, 925 mb values are forecast to peak at
nearly two standard deviations above normal from Friday into the
weekend. This pattern will elevate the heat risk across the
region. Heat Advisories or even Extreme Heat Warnings may be
issued. Residents and visitors are strongly advised to stay
hydrated, avoid prolonged sun exposure during peak heat hours,
and take extra precautions, particularly those without access to
adequate cooling or hydration.

&&

.AVIATION...
(06Z TAFs)

SHRA/TSRA are expected across the region over the next 48 hours,
bringing periods of MVFR to brief IFR conditions. Activity will
mainly affect TJSJ and USVI terminals through 16/16Z, shifting to
TJBQ and TJPS through 16/22Z, then returning to TJSJ and USVI
terminals after 16/22Z. Winds will be light to calm and variable
early, increasing to 15–20 kts with gusts up to 25–30 kts between
16/14-22Z, before diminishing again to light and variable after
16/22Z. Gusty winds are possible near SHRA/TSRA.

&&

.MARINE...

A surface high pressure system located over the central and eastern
Atlantic, in combination with a departing low-level perturbation,
will promote moderate to locally fresh east to northeasterly winds
today. Small craft are urged to exercise caution across the offshore
waters and local passages. Passing showers and isolated thunderstorms
will continue through the morning hours across most waters, followed
by stronger thunderstorms across the western waters of Puerto Rico
and the Mona Passage during the early afternoon hours. A stronger
tropical wave is expected to approach late tonight into Wednesday,
enhancing intensity and shower coverage.

&&

.BEACH FORECAST...

Today, there is a moderate risk of rip currents across the north and
east-facing beaches of Puerto Rico, Culebra, and St. Croix. Similar
conditions are expected to prevail most of the workweek so beachgoers
are advised to exercise caution at all times as a moderate risk means
life-threatherning rip current are possible in the surf zone. A low
risk should prevail elsewhere. Additional hazards include afternoon
thunderstorms. Remember, if you hear thunder, seek shelter inside
of a safer place immediately.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
517 AM AST Thu Sep 18 2025

.KEY MESSAGES...

* A departing tropical wave, in combination with an upper-level
trough, will continue to enhance shower and thunderstorm
activity today. As a result, the risk of flooding will remain
elevated across Puerto Rico. Additional hazards include rapid
river rises, landslides, and frequent lightning.

* Across the U.S. Virgin Islands, a showery pattern will persist
today, leading to a limited risk to observe flooding.

* A warming trend is expected to begin on Friday, bringing
increasing temperatures that may cause heat indices to reach
Heat Advisory criteria through at least early next week,
particularly in coastal and urban areas.

* A moderate risk of rip currents is in effect for the northern
and eastern beaches of Puerto Rico, as well as Culebra and St.
Croix today. Although Tropical Storm Gabrielle is forecast to
move well northeast of the region this weekend, swells generated
by the storm may lead to a slight deterioration in marine and
beach conditions.

&&

.SHORT TERM...Today through Saturday...

Persistent showers and thunderstorms, generated by a passing
tropical wave and a nearby upper-level trough, spread across much of
the region overnight. Radar estimates show peak rainfall near two
inches between Naguabo and Ceiba in eastern Puerto Rico, and across
eastern St. Croix. Several flood advisories were issued, but no
flooding impacts have been reported. However, the Rio Fajardo did
respond to the rainfall, briefly exceeding action flood stage.
Overnight lows finally dropped below 80°F across most areas,
except at exposed sites on St. John. Winds were light and variable
over land from the east-northeast, with brief gusts near the
stronger storms.

A departing tropical wave and a trough to the north will keep the
atmosphere very moist and unstable today, with PWAT values above 2.1
inches and weak winds to steer storms. Showers and thunderstorms
will affect Puerto Rico and the USVI through the day—beginning over
windward areas of eastern PR, the USVI, and nearby islands in the
morning, then spreading inland and focusing on the interior and west-
northwest PR by afternoon and evening. These slow-moving storms
could produce frequent lightning, gusty winds, and heavy rain
capable of flooding already saturated soils and urban areas. The
USVI will remain active as well, with less frequent and likely less
intense storms, but similar hazards possible throughout the day.
Since it is a weekday with school and work underway, allow extra
travel time and stay alert for flooded roads, poor drainage areas,
and dangerous lightning.

A very wet pattern will persist, with only a brief break Friday
night before another surge of tropical moisture arrives over the
weekend. With the upper trough still in place and winds weakening
below 10 mph, showers and thunderstorms will be slow-moving,
heightening the risk of flooding, localized flash flooding, and
landslides in saturated areas. Central Puerto Rico will see storms
each afternoon, with the most active zones shifting from the west
and northwest on Friday to the north on Saturday, while the USVI
trends drier. A southerly flow, perhaps influenced by Tropical Storm
Gabrielle tracking northwest well north of the region, will also
favor hot and humid conditions. Winds will ease from gentle tonight
to light on Friday and Saturday. As rain coverage decreases,
dangerous heat will become an additional concern.


.LONG TERM...Sunday through Thursday...

For the long-term period, as Tropical Storm Gabrielle moves well
northeast of the region, our area will be positioned in a col
region. As the pressure gradient weakens, very light east-
southeasterly winds are expected to persist on Sunday and continue
through at least Monday night. This flow will help maintain a
healthy moisture content across the area. According to the latest
model guidance, precipitable water values are forecast to
fluctuate between 1.80 and 2.20 inches from Sunday through
Tuesday, which is within the average to above-average range for
this time of year. In terms of temperature, forecast data
suggests that 925 mb temperatures will peak at nearly two standard
deviations above normal on Sunday and remain near the 75th
percentile into early next week. This pattern will increase the
risk of heat-related impacts across the region. Heat Advisories or
even Extreme Heat Warnings may be issued.

Under this scenario, expect morning showers across windward areas
of the islands, followed by afternoon showers and isolated
thunderstorms across the interior and western sectors of Puerto
Rico, fueled by diurnal heating and local effects. Urban and small
stream flooding is likely to persist each day, and some rivers
may reach flood stage. Saturated soils from recent rainfall
combined with light winds during this period will contribute to
slower-moving showers, which could lead to higher rainfall totals
and an increased risk of flooding. Additional hazards may include
landslides, frequent lightning, and gusty winds.

On Tuesday night, a wind surge is expected to approach the region,
bringing gusty winds along with increased moisture and a higher
chance of rainfall through the middle of the week. By Wednesday
and Thursday, one of the tropical waves currently being monitored
by the National Hurricane Center is expected to approach, further
enhancing a wetter pattern across the islands. We will continue to
monitor this evolving situation closely and provide updates as
necessary.

&&

.AVIATION...
(06Z TAFs)

Frequent, slow-moving SHRA/TSRA will affect the region over the next
24 hours, producing periods of MVFR and brief IFR conditions.
Activity will mainly impact TJSJ and USVI terminals through 18/16Z,
before expanding to most terminals for the remainder of the forecast
period. East-southeast trade winds will prevail today, starting
light to calm and variable at TAF sites this morning, then
increasing to 14–18 kt with higher gusts between 18/14–22Z, before
easing again to light and variable after 18/22Z. Gusty, erratic
winds are likely in and near SHRA/TSRA.

&&

.MARINE...

A surface high-pressure system over the central Atlantic will
promote gentle to locally moderate east to southeast winds today. For
the rest of the forecast period, light to gentle easterly to
southeasterly winds will prevail as the pressure gradient weakens. A
departing tropical wave will continue to result in frequent showers
and strong thunderstorms over the local waters today. Additionally,
swells generated by Tropical Storm Gabrielle, as it moves northeast
of the region, could slightly deteriorate marine conditions this
weekend across the Atlantic waters.

&&

.BEACH FORECAST...

A moderate risk of rip currents is in effect for the north and
east-facing beaches of Puerto Rico, Culebra, and St. Croix, with a
low risk elsewhere. While a brief improvement in conditions is
expected on Friday, the moderate risk will return Saturday and
persist into early next week, driven by swells from Tropical Storm
Gabrielle. Beachgoers should exercise caution at all times, as a
moderate risk indicates that life-threatening rip currents are
possible in the surf zone.

In addition, thunderstorms are a hazard for the beachgoers today.
Remember, if you hear thunder, seek shelter in a safe indoor
location immediately.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
506 AM AST Fri Sep 19 2025

.KEY MESSAGES...

* Abundant moisture and an induce surface trough will keep the
flood risk elevated today across north and northwest areas of
Puerto Rico, where strong afternoon thunderstorms are likely.

* Across the U.S. Virgin Islands, a showery pattern will persist
today.

* A warming trend is anticipated over the next few days. A Heat
Advisory is in effect today from 10 AM to 5 PM AST across urban
and coastal areas of Puerto Rico, Vieques, Culebra, and the
U.S. Virgin Islands.

* A moderate risk of rip currents persist along the northwestern
beaches of Puerto Rico, while a low risk elsewhere. Although
Tropical Storm Gabrielle is forecast to move well northeast of
the region this weekend, swells generated by the storm will
increase the potential for life-threatening rip currents across
the north and east facing beaches of the islands.

* A wet and unstable pattern is possible by the middle part of
next week onward.

&&

.SHORT TERM...Today through Sunday...

Persistent showers and thunderstorms, supported by a nearby upper-
level trough and an associated surface trough, developed overnight
across the Caribbean waters, Mona Passage, and the coastal waters of
eastern Puerto Rico and the U.S. Virgin Islands. Radar estimates
indicated significant rainfall offshore, with 1–2 inches observed
along southeastern coastal areas. A Flood Advisory was issued there,
as soils were already saturated from up to 4 inches of rain reported
during the past 24 hours. Meanwhile, cooler overnight lows finally
returned across all surface observing stations, dropping below 80°F.

Today, with less cloud cover and stronger heating, conditions will
favor increased locally induced showers and thunderstorms, supported
by well-above-normal PWAT values (~2.1 inches) and marginal
instability. Periods of moderate to heavy rainfall are likely this
morning across southern Puerto Rico, the U.S. Virgin Islands, and
nearby islands. With weak background winds under 10 knots, sea-
breeze and local effects will dominate, allowing afternoon storms to
first develop over the interior before spreading westward and
northward through outflows and weak southerly steering flow. These
slow-moving storms may bring frequent lightning, gusty winds, and
prolonged moderate to heavy rainfall leading to flooding, especially
in saturated and urban areas. The U.S. Virgin Islands will remain
less active overall, though similar hazards are possible. Meanwhile,
dangerous and potentially life-threatening heat will persist, with a
Heat Advisory in effect for urban and coastal areas.

A wet pattern will continue through Saturday evening, with typical
moisture lingering into Sunday. Clearer mornings over the next few
days will allow stronger heating, increasing dangerous heat risks
while also fueling afternoon storm development. Under weak winds,
showers and thunderstorms will form over the interior and spread
toward northern and western Puerto Rico as trade winds, outflows,
and sea breezes interact. By Saturday, southeasterly flow will shift
the strongest afternoon storms into the northwest, then farther west
by Sunday as winds turn more easterly. These slow-moving storms
could bring localized flooding, isolated flash floods, and
landslides. The U.S. Virgin Islands will remain comparatively drier,
but dangerous and potentially life-threatening heat will persist
across the region, with even higher values expected as southerly
winds enhance moisture transport.


.LONG TERM...Monday through Friday...

At the start of the upcoming workweek, light winds will prevail,
gradually shifting from southeasterly to easterly throughout the
day. This shift will be driven by a surface high-pressure system
dominating the Central Atlantic. Based on the latest model
guidance, Monday is expected to have the lowest precipitable water
content of the forecast period, with values ranging from slightly
below average to near seasonal levels. Additionally, drier air is
anticipated in the mid to upper levels of the atmosphere compared
to recent days. Temperature-wise, forecast data indicates that
925 mb temperatures will remain nearly two standard deviations
above normal on Monday, followed by a gradual cooling trend. Under
these conditions, expect morning showers over windward areas of
the islands, with afternoon showers and isolated strong
thunderstorms developing across interior and western Puerto Rico.
These will be driven by diurnal heating, available moisture, and
local effects.

By Tuesday, a transition to a wetter and more unstable pattern is
expected to evolve. An approaching wind surge will increase wind
speeds and moisture levels, leading to higher chances of rainfall
through the remainder of the forecast period. Model guidance
suggests a rapid rise in PWAT values, peaking around 2.0 to 2.25
inches, well above climatological norms for this time of year.
Around Wednesday into Thursday, a tropical wave currently being
monitored by the National Hurricane Center is forecast to approach
the region, further enhancing the wet pattern. As of now, the
wave is located just off the west coast of Africa, with a low
formation chance in the next 48 hours (near 0%) and a 20% chance
over the next 7 days. Aloft, some troughiness should be present
combined with low level southeasterly flow driven by the Atlantic
surface high pressure system. This will continue to advect
tropical moisture into the region through Friday maintaining the
wet pattern. Expect and elevated flood risk each day, likely
including rapid river rises and landslides. Current model guidance
suggests the system may develop after moving away from our area.
We will continue to monitor this evolving situation closely and
provide updates as necessary.

&&

.AVIATION...
(06Z TAFs)

Slow-moving SHRA/TSRA will affect the region over the next 24
hours, producing periods of MVFR and brief IFR conditions.
Activity will mainly impact TJSJ and USVI terminals, with
SHRA/TSRA also expected at TJPS and TJBQ between 19/17Z and
19/22Z. Winds will remain light, allowing sea-breeze circulations
to dominate, with speeds generally calm to 8–10 kt before easing
again to light/variable after 19/22Z. Gusty and erratic winds are
likely in and near SHRA/TSRA.

&&

.MARINE...

Gentle to light southeasterly winds will prevail today and through
the weekend. High moisture content and a weak induced trough will
continue to result in frequent showers and thunderstorms over the
local waters through tonight. A long period northeasterly swell
generated by Tropical Storm Gabrielle, currently moving over the
Central Atlantic, will reach the local waters and passages during
the weekend. However, seas are forecast to remain below Small Craft
Advisory criteria.

&&

.BEACH FORECAST...

Today, a moderate risk of rip currents persists along the
northwestern beaches of Puerto Rico, while a low risk is expected
elsewhere. However, even where the risk is low, life-threatening
rip currents can still occur, especially near groins, jetties,
reefs, and piers.

This brief improvement will not last long. The moderate risk is
expected to return tomorrow, Saturday, and continue into early
next week, driven by swells generated by Tropical Storm Gabrielle.
Beachgoers are urged to exercise caution at all times, as a
moderate risk means life-threatening rip currents are possible
within the surf zone.

Additional beach hazards today include strong afternoon thunderstorms,
especially along northwestern beaches, and elevated heat risk
during peak heat hours, typically from 10 AM to 5 PM. Stay well
hydrated, and remember, if you hear thunder, seek shelter in a
safe indoor location immediately.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
525 AM AST Sat Sep 20 2025

.KEY MESSAGES...

* The available moisture combined with the todays sunshine will
drive warmer temperatures and heat indices today.

* Extreme Heat Warning issued for Puerto Rico and a Heat Advisory for
Vieques, Culebra, Saint Thomas, Saint John, and Saint Croix.

* A variable weather pattern is expected for the US Virgin
Islands during the weekend, with shower activity during the
morning and early evening hours.

* Afternoon shower activity is expected each day across the
norther interior to northwest sections of the island, inducing
an elevated flood threat and a limited lightning threat.

&&

.SHORT TERM...Today through Sunday...

Overnight, showers and thunderstorms developed over the U.S. Virgin
Islands, Vieques, and Culebra, while mainland Puerto Rico stayed
mostly dry, aside from light rainfall after 8 PM from lingering
afternoon activity. Rainfall estimates reached up to 1 inch in St.
Thomas and around a quarter of an inch in Vieques and Culebra, with
only trace to light amounts observed across Puerto Rico.
Temperatures cooled into the 70s across most areas, dipping into the
lower 70s or below in higher elevations, with all observing stations
reporting lows under 80°F. Winds remained light to gentle from the
south over the waters, while over land they were light, calm, and
variable.

Expect a dangerous combination of hazards. With even less cloud
cover than yesterday, more sunshine will drive warmer temperatures.
A generally light to gentle southerly trade wind will further
support this warming trend while steering added tropical moisture
into the region. With precipitable water values remaining well above
normal (>2.1 inches), these factors are expected to lead to extreme
heat conditions. An Extreme Heat Warning is in effect for Puerto
Rico, with a Heat Advisory for the U.S. Virgin Islands, Vieques, and
Culebra. A lingering mid-to-upper level trough north of the region
remains the dominant feature, helping to maintain marginally
unstable conditions. As a result, the combination of extreme heat,
abundant moisture, and weak steering flow will favor the development
of slow-moving afternoon showers and thunderstorms, especially
across northern Puerto Rico, where the light southerly flow will
concentrate activity. These storms could be strong and will likely
bring the risk of frequent lightning, gusty winds, and localized
flooding from prolonged heavy downpours.

Dangerously hot conditions will persist through the period. On
Sunday, with less available moisture (lower PWAT), afternoon storms
will likely be fewer and less intense, though still capable of
producing frequent lightning and localized flooding. By Monday, a
more patchy wet/dry pattern is expected as subsidence from an
approaching tropical wave interacts with a weaker mid-level trough.
At the same time, cooling mid-level temperatures will create a more
favorable environment for deep convective development. If the timing
of these features aligns, conditions could support another round of
strong to severe thunderstorms Monday afternoon, despite only modest
moisture. Overnight periods will remain mostly quiet, with only
isolated showers and a stray thunderstorm over coastal waters and
eastern Puerto Rico.

.LONG TERM...Tuesday through Saturday...

The long-term forecast remains consistent with previous discussions.
Beginning Tuesday, conditions are forecast to transition into a
wetter and more unstable pattern. An approaching wind surge will
bring an increase in both wind speeds and moisture levels,
allowing for widespread rainfall. From Wednesday to Thursday, a
tropical wave currently being tracked by the National Hurricane
Center is forecast to move near the region, further enhancing the
potential for rainfall and thunderstorm activity across Puerto
Rico and the U.S. Virgin Islands. Currently, the wave is located
over the eastern Atlantic, with a low probability of development:
near 0% within the next 48 hours and 20% over the next 7 days.

A weak upper level troughing combined with low-level
southeasterly flow around the Atlantic high pressure will maintain
a steady influx of tropical moisture into the area through
Friday. This setup will support a prolonged period of unsettled
weather, with daily episodes of heavy rainfall. The latest model
guidance suggests precipitable water values of around 2.0 to 2.2
inches and mid- level temperatures near -7 to -8 °C, indicating a
high potential for deep convection with thunderstorms.

Given saturated soils from recent rains, the primary hazards include
landslides in vulnerable terrain, rapid river rises, and an
elevated risk of flash flooding. While current model trends
suggest any tropical development is more likely after the system
passes west of the area, the evolving situation will be monitored
closely. Updates will be provided as new data becomes available
from official resources such as the National Hurricane Center and
your local National Weather Service.

&&

.AVIATION...
(06Z TAF)

VFR will prevail at most Puerto Rico terminals this morning. Across
the U.S. Virgin Islands, slow-moving SHRA/TSRA will bring brief
periods of MVFR. After 20/16Z, SHRA/TSRA will shift into central and
northern Puerto Rico, with MVFR to brief IFR expected at TJSJ after
20/16Z and at TJBQ after 20/17Z. Thunderstorms will also spread into
the vicinity of TJPS. Winds will remain light, driven by sea-breeze
circulations at 8–10 kt, before becoming calm and variable after
20/22Z. Gusty, erratic winds are likely in and near SHRA/TSRA.

&&

.MARINE...

A surface high pressure, in combination with Tropical Storm
Gabrielle located about 550 miles east-northeast of the northern
Leeward Islands, will continue to result in a gentle to light
southeasterly wind flow across the local waters through the rest of
today into the weekend. As a result, seas will range from 2 to 6
feet across most of the waters. Localized hazardous marine
conditions are possible due to showers and thunderstorms that could
produce locally higher seas and gusty winds. A long-period
northeasterly swell generated by Tropical Storm Gabrielle, currently
moving over the central Atlantic, will reach the local waters and
passages during the weekend. However, seas are forecast to remain
with or below Small Craft Advisory criteria.

&&

.BEACH FORECAST...

A moderate rip current risk persists today along north and eastern
Puerto Rico, as well as Culebra and Saint Croix, while the rest
remain with a low risk, though dangerous currents remain possible
near piers, reefs, and jetties. This risk will increase again
from today into early next week as swells from Tropical Storm
Gabrielle arrive. Strong afternoon thunderstorms would trigger the
lightning threat along the northern coastal side.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
525 AM AST Sun Sep 21 2025

.KEY MESSAGES...

* An Extreme Heat Warning was issued for Puerto Rico and Heat
Advisory for Culebra, Vieques, Saint Thomas, Saint John, and
Saint Croix particularly in coastal and urban areas of the
islands from 10 AM through 4 PM.

* Afternoon thunderstorm activity is expected each day across the
northern interior to northwest sections of PR. These
thunderstorms will increase the risk of flooding and lightning
threat.

* Across the USVI, fair weather conditions are expected to prevail
in general with passing showers at times.

* The National Hurricane Center is monitoring a system in the
eastern tropical Atlantic and is expected to reach the islands
as a tropical wave by midweek.


&&

.SHORT TERM...Today through Tuesday...

Variable weather conditions have continued through the overnight and
early morning hours, influenced by a nearly stationary mid- to upper-
level trough positioned north-northeast of the region. Satellite and
radar imagery detected isolated showers and thunderstorms developing
mainly over the surrounding waters, with a few briefly brushing
northeastern Puerto Rico before dissipating quickly inland. This
pattern is expected to persist for the rest of the morning hours.

A deep layer of southeasterly winds, extending up to 700 mb, will
prevail today. As a result, 925 mb temperatures remain well above
normal for this time of year. Combined with abundant low-level
moisture, this will lead to dangerous heat index values across urban
and coastal sectors of the islands. Accordingly, an Extreme Heat
Warning is in effect for Puerto Rico, while a Heat Advisory has been
issued for Vieques, Culebra, and the USVI.This intense heating,
in combination with sea breeze convergence, orographic lift, and
troughiness aloft, will support another active round of afternoon
convection, especially across the interior and northwestern Puerto
Rico. Streamer activity downwind of El Yunque could also affect
the San Juan metro area. This will result in urban and small
stream flooding, quick river rises, and localized landslides.
Stronger thunderstorms may produce frequent lightning and gusty
wind conditions.

On Monday, a dry slot is expected to briefly cross the islands
during the morning hours. Suspended Saharan dust particulates will
accompany the arrival of this dry slot, promoting hazy skies. A wind
surge behind the dry slot will quickly follow, causing showers and
thunderstorms to move more rapidly during the afternoon. Although
rainfall accumulations may be somewhat limited due to the faster
storm motion compared to previous days, localized downpours remain
possible. Meanwhile, the mid- to upper-level trough will continue to
meander north of the CWA, maintaining sufficient instability aloft
to support convective development. By Tuesday, the mid- to upper-
level trough will still linger north of the region, sustaining
instability aloft. Winds will shift slightly more easterly, favoring
afternoon convection across the interior and western Puerto Rico.
Although the heat threat will remain, it should gradually subside as
the southerly component weakens.

By late Tuesday night, conditions are expected to change
significantly as the moisture field associated with a vigorous
tropical wave begins to approach from the east. This will increase
the frequency of showers and thunderstorms across the eastern
sections of the CWA. The National Hurricane Center is monitoring
this wave, which currently has a low chance of tropical development
over the next seven days. Therefore, weather conditions late Tuesday
night into midweek will be highly dependent on the evolution and
movement of this tropical wave as it nears the northeastern
Caribbean.

.LONG TERM...Wednesday through Sunday...

From Wednesday through Thursday, a tropical wave currently being
tracked by the National Hurricane Center will move across the
region, bringing an increase in showers and thunderstorm activity
across Puerto Rico and the U.S. Virgin Islands. As of now, the
system is located over the eastern Atlantic with a low probability
of development, with near 0% within 48 hours and around 30% over
the next 7 days. Additionally, a weak upper-level trough, combined
with southeasterly flow around the Atlantic ridge, will sustain a
steady influx of tropical moisture through early Friday. This
pattern supports a prolonged period of unsettled weather with
daily rounds of heavy rainfall and thunderstorms. Model guidance
suggests precipitable water values between 2.0 and 2.3 inches
(well above climatological normals), along with mid-level
temperatures of -7 to 8 degrees Celsius, enhancing the risk for
deep convection and potentially having limited to elevated risk of
flooding through Friday.

Given the prevailing wet pattern on previous days and the already
saturated soils, the main threats include flash flooding, rapid
river rises, and landslides in vulnerable terrain. While tropical
development appears more likely after the system passes east of
the region, the situation will be monitored closely with updates
from official sources such as the National Hurricane Center.

Temperatures are expected to gradually increase beginning Thursday.
Given the available moisture and prevailing conditions, a Heat
Advisory may be issued for Thursday, followed by a potential
Extreme Heat Warning on Friday. However, this will largely depend
on how the tropical wave evolves.

By Friday into Saturday, a gradual improvement in weather conditions
is expected as a drier air mass filters into the region, bringing
a temporary break in the unsettled pattern.

On Sunday, however, model guidance indicates that another tropical
wave may approach the region. While it is too early to determine
development potential, this system will need to be monitored
closely as it draws nearer.

&&

.AVIATION...
(06Z TAFS)

Isolated SHRA/TSRA will persist overnight mainly across coastal
waters. After 14Z, SHRA/TSRA development is expected across the
interior and NW PR, with impacts expected at TJBQ. A PROB30 for TSRA
has been included at TJBQ during the afternoon hours. MVFR conds,
brief IFR, and Mtn Obsc are possible in and near TSRA, with frequent
LTG and gusty winds. Streamer activity downwind of El Yunque could
also affect TJSJ after 17Z. Winds were light and variable overnight,
increasing after 14Z to 8-13 kts from ESE/SE with sea breeze
variations and higher gusts, bcmg light/VRB after 23Z. Stronger
gusts near SHRA/TSRA.

&&

.MARINE...

The long-period northeasterly swell generated by Tropical Storm
Gabrielle, moving over the central Atlantic, will continue to reach
the local waters and passages through tonight. However, seas are
forecast to remain below Small Craft Advisory criteria. Gentle to
light southeasterly winds will continue across the regional waters
through early Sunday, turning more easterly through the week, and
becoming light to moderate by Monday.

&&

.BEACH FORECAST...

There is a moderate risk of rip currents for the north and east-
facing beaches of Puerto Rico, Culebra, and Saint Croix through
tonight. Today, stronger rip currents are possible in isolated
areas due to a 3 to 4 ft long period northeasterly swell from
distant Tropical Storm Gabrielle.

Afternoon thunderstorms producing cloud to ground lightning are
expected each day, mainly across the north and western coastal
areas as well as the metro of PR. Remember, if you hear thunder,
seek shelter in a safe indoor location immediately.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
521 AM AST Mon Sep 22 2025

.KEY MESSAGES...

* Once again, Heat Advisory to Extreme Heat Warning conditions are
expected across the coastal and urban areas of PR and the USVI,
today. From tomorrow onward we anticipate a gradual decrease in
heat hazards as tropical waves approach the islands.

* Across the USVI, weather conditions are expected to prevail
generally with brief passing showers at times.

* Hazy skies are expected on Tuesday due to minor to moderate
concentrations of Saharan dust.

* A tropical wave with a low chance of formation into a tropical
system will bring an increase in shower and thunderstorm
activity by midweek.

&&

.SHORT TERM...Today through Wednesday...

During the overnight and early morning hours, weather conditions
remained similar to yesterday with showers and isolated
thunderstorms developing mainly over the eastern waters. Radar-
estimated rainfall reached up to half an inch across localized areas
of the USVI and eastern Puerto Rico. A similar pattern is expected
to persist through the morning, favoring the eastern third of the
CWA, while mostly clear skies dominate across western Puerto Rico.

Winds are gradually shifting to a more easterly direction today, but
warmer-than-normal conditions will persist. As a result, an Extreme
Heat Warning and a Heat Advisory are in effect for urban and coastal
areas of Puerto Rico, Vieques, Culebra, and the USVI. By this
afternoon, a slot of slightly drier air accompanied by suspended
Saharan dust will move across the region, bringing a brief period of
hazy skies. However, sufficiently low-level moisture combined with
intense daytime heating and sea breeze convergence will still lead
to shower and thunderstorm development across the interior and
western Puerto Rico. Stronger storms may produce frequent lightning,
gusty winds, and localized flooding.

By tonight into the morning hours, a more seasonal pattern will
dominate with a few passing showers over the waters moving inland at
times. However, by late Tuesday night and into midweek, conditions
will deteriorate significantly as a vigorous tropical wave moves
into the region. The National Hurricane Center continues to monitor
this feature, which currently has a low chance of tropical
development, but will nonetheless bring a very unstable and wet
pattern across the islands.

Precipitable water values are expected to surge between 2.25 and 2.5
inches, approaching maximum climatological values for this time of
year. Combined with strong instability, this will support numerous
showers and isolated to scattered thunderstorms capable of producing
heavy rainfall. Deterministic model guidance (both GFS and ECMWF)
indicates the wave will pass as an open wave or low, with its vort
max peaking close to or over the local region by Wednesday. The
Galvez-Davison Index for both models suggests the potential for
scattered to widespread heavy rain-producing thunderstorms.
Meanwhile, the ECMWF Extreme Forecast Index (EFI) shows ensemble
spread, highlighting uncertainty but signaling an elevated flooding
risk.

Importantly, this wave is also expected to carry embedded Saharan
dust, which could add additional uncertainty to the forecast. The
suspended particulates may limit convection at times or modulate
rainfall efficiency, particularly in areas where dry air briefly
mixes in. This interplay between abundant tropical moisture,
instability, and Saharan dust could lead to localized variability in
rainfall accumulations and storm intensity.

Rainfall accumulations are most likely to impact the USVI, Vieques,
Culebra, and southern and eastern Puerto Rico, though heavy rain
will be possible elsewhere. Impacts could include urban and small
stream flooding, localized flash flooding, quick river rises, and
landslides. In addition, stronger thunderstorms will bring the risk
of frequent lightning and gusty winds.

.LONG TERM...Thursday through Monday...

On Thursday, the tropical wave being monitored by the National
Hurricane Center will continue to move across the region, increasing
the frequency of showers and thunderstorm activity across Puerto
Rico and the U.S. Virgin Islands. The system is located over the
central tropical Atlantic with a low probability of development,
with near 10 percent within 48 hours and around 60 degrees over the
next 7 days. Additionally, a weak upper-level trough, combined with
southeasterly flow around the Atlantic ridge, will sustain a steady
influx of tropical moisture through early Friday. This pattern
supports a prolonged period of unsettled weather with daily rounds
of heavy rainfall and thunderstorms. Model guidance keep suggesting
precipitable water values between 2.0 and 2.3 inches or above normal
values for this time of the year, along with mid-level temperatures
of -6 to -8 degrees Celsius, enhancing the risk for deep convection
and potentially having limited to elevated risk of flooding through
Friday.

Given the expected wet pattern on previous days and the
already saturated soils, the main threats include flash flooding,
rapid river rises, and landslides in vulnerable terrain. Tropical
development appears more likely by mid to latter part of this week
as the system moves west-northwestward to northwestward across the
central Atlantic. Nevertheless, the weather feature will be
monitored closely with updates from official sources such as the
National Hurricane Center.

Later in the weekend a slight and gradual improvement in weather
conditions is expected as a drier air mass filters into the region,
bringing a temporary break in the unsettled pattern.

By the beginning of the workweek, model guidance indicates that
another tropical wave may approach the region. While it is too early
to determine development potential, this system will need to be
monitored closely as it draws nearer.

Temperatures are expected to gradually increase Friday into
Saturday. Given the available moisture and the fact that models
continues to show that winds will also become lighter an Extreme
Heat Warning could potentially be issued. However, this will largely
depend on how the tropical wave evolves and if indeed the
significant cloudiness moves out of the area by the end of the
workweek.

&&

.AVIATION...
(06Z TAFS)

Iso SHRA/TSRA will persist overnight mainly across coastal waters.
Aft 14Z, SHRA/TSRA dvlpmnt expected across the interior and W PR,
with VCTS at TJBQ as more E winds favor aftn convection in its
vicinity. Still, MVFR conds, brief IFR, and mtn obsc are psbl
in/near TSRA. HZ due to Saharan dust psbl this aftn and eve, but VIS
expected to remain P6SM. Winds were LGT/VRB overnight, bcmg E/ESE 8-
13 kts aft 14Z with sea breeze variations and higher gusts. Winds
bcmg LGT/VRB aft 23Z. Stronger gusts nr SHRA/TSRA.

&&

.MARINE...

A gradual increase in trades are expected today. A strong tropical
wave will bring squally weather across the regional waters from late
Tuesday through late Wednesday night. Increasing winds and choppy
seas are expected with the wave passage. Seas should remain at 4 feet
or less in general through the week. However, a fading northeasterly
swell will keep seas around 3 to 4 feet across the Atlantic
waters.

&&

.BEACH FORECAST...

A fading northeasterly swell will maintain a moderate risk of rip
currents along the northcentral to northwestern facing beaches of
Puerto Rico. The moderate risk will return along the entire
northern and easter coast of PR, Culebra, and Saint CRoix on
Tuesday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
503 AM AST Tue Sep 23 2025

.KEY MESSAGES...

* A vigorous tropical wave will affect the region late tonight
through Thursday, bringing widespread showers and thunderstorms.
Heavy rainfall could result in urban and small stream flooding,
flash flooding, and landslides.

* Trailing moisture from this system, along with another tropical
wave, will sustain an unsettled and wet pattern through the
weekend, maintaining an elevated flooding risk. Strong
thunderstorms may also produce frequent lightning and gusty winds.

* For the U.S. Virgin Islands, showers and thunderstorms will
bring periods of heavy rainfall and localized flooding through
the weekend.

* An elevated to significant heat threat will persist today and
Friday onwards, with southerly winds driving warmer-than-normal
temperatures and high humidity, resulting in dangerous heat
indices in urban and coastal areas.

&&

.SHORT TERM...Today through Thursday...

Overnight conditions were mostly calm inland under clear skies,
although brief showers occasionally moved across the San Juan area
with the east-northeasterly winds. After 1 AM, showers became more
frequent over the Atlantic and Caribbean waters, but accumulations
did not reach one inch. Low temperatures stayed in the mid to upper
70s across coastal and urban areas, while mountain and rural
locations dipped into the upper 60s to low 70s.

Another hot day is expected today, though heat indices are not
forecast to reach extreme heat warning criteria. The reason behind
it is that temperatures at 925 mb will stay below the above and two
standard deviations above normal for this time of year, and winds
will become more northeasterly ahead of an approaching tropical
wave. This wind shift will favor shower and thunderstorm development
mainly over central and western to southwestern Puerto Rico. The
latest model guidance indicates that precipitable water values will
gradually rise to above-normal values for this time of year, and 500
mb temperatures will also remain near -7 degrees Celsius.

From tonight into Thursday, the strong/robust tropical wave,
currently located between 60W and 70W, will move across the region.
While the National Hurricane Center gives this system only a low (10
percent) chance of developing into a tropical cyclone in the next 48
hours, it will still bring unsettled conditions. Squally weather,
periods of heavy rainfall, and isolated to scattered thunderstorms
are expected. Rainfall totals during this period are expected to
range from 2 to 4 inches, with isolated areas receiving up to 6
inches. The heaviest activity is anticipated to occur between
Wednesday and Thursday.

Due to the fact that recent rains have already left soils saturated
across the northern and western half of Puerto Rico, St. Thomas, and
western St. Croix the hazards and impacts associated with this event
will include urban and small stream flooding, flash flooding, rapid
river rises with some streams reaching flood stage, water surges,
and the potential for landslides in areas of steep terrain.

Residents and visitors are urged to stay informed and prepared for
periods of heavy rain and a prolonged risk of flooding through at
least Thursday. For additional details, please refer to the
hydrology section.

.LONG TERM...Friday through Tuesday...

The unsettled and wet pattern will persist into the weekend and
through early next week as the vigorous tropical wave lifts north of
the region, while another trailing wave approaches from the
southeast and also tracks north. This evolving setup will induce a
deep-layer southerly flow over the local area, favoring the
continuous transport of abundant tropical moisture across the
islands. Precipitable water values will generally remain elevated,
exceeding 2.0 inches through Monday, supporting frequent rounds of
showers and thunderstorms.

Given the saturated soils and elevated streamflows from the passage
of the tropical wave in previous days, even modest rainfall could
quickly lead to urban and small stream flooding. The risk of more
significant flooding, including flash flooding, rapid river rises,
and landslides in steep terrain, cannot be ruled out during this
period. Daily shower and thunderstorm activity will be driven by
strong instability, diurnal heating, and sea breeze convergence,
with the strongest storms capable of producing frequent lightning,
gusty winds, and locally heavy downpours. Through the weekend,
shower and thunderstorm activity will favor the southern and eastern
portions of Puerto Rico, Vieques, Culebra, and the U.S. Virgin
Islands during night and morning hours, while afternoon convection
develops across the interior and northwestern Puerto Rico. The
prevailing southerly flow may further enhance heavy rainfall-
producing storms along the northern slopes, particularly where
upslope convergence interacts with abundant moisture.

By Monday, the trailing wave will keep the atmosphere moist and
unstable, prolonging the flooding risk. While deterministic guidance
continues to highlight favorable conditions for heavy rainfall-
producing thunderstorms, Saharan dust may remain intermittently
embedded within the moisture plume. This could limit convection
locally or modulate rainfall rates, adding variability to
precipitation totals across the forecast area.
It is not until Tuesday that a drier air mass is expected to filter
into the region. Precipitable water values are forecast to drop from
near 2.2 inches to below 1.6 inches, signaling a gradual improvement
in conditions. Despite the drying trend, isolated convection may
linger, especially during the afternoon hours, but the overall
flooding risk should decrease compared to previous days.

In addition to the rainfall hazards, a daily heat threat will
persist through the forecast period. Deep-layer southerly winds will
continue to transport warmer-than-normal air, while excessive low-
level moisture will elevate heat indices to sweltering levels.
Extreme Heat Warnings and Heat Advisories are likely to be issued
for coastal and urban areas across Puerto Rico, Vieques, Culebra,
and the U.S. Virgin Islands.


&&

.AVIATION...
(06Z TAFs)

Mostly VFR conditions will prevail across all TAF sites.
However, after 23/17Z, VCTS are likely at TJPS as NE winds favor
afternoon convection in its vicinity. With this activity, periods of
MVFR are possible after 17Z. Winds will remain from the E-NE from
23/14 - 23/22Z at 6–13 kts and higher gusts near the heaviest RA and
TS. Winds will weaken again to light and variable after 23Z.
Nevertheless, after 23/22Z, a tropical wave will begin to reach the
TIST and TISX.

&&

.MARINE...

Major Hurricane Gabrielle is located well to the north over the
western Atlantic. An induced surface trough will maintain moderate
easterly winds across the region today. Tomorrow Wednesday, a
vigorous tropical wave will move into the islands, increasing the
potential for thunderstorms and leading to localized hazardous marine
conditions. These storms may produce frequent lightning over exposed
waters. In addition, an increase in surface winds is forecast from
Wednesday onward, particularly across the offshore Atlantic waters,
where small craft operators should exercise caution. Seas close to 7
feet over northeastern offshore Atlantic waters are possible were
winds will be highest.

&&

.BEACH FORECAST...

Moderate rip current risk will prevail at most beaches across Puerto
Rico, Vieques, Culebra, and the U.S. Virgin Islands through the
period. However, as a vigorous tropical wave approaches and moves
over the region tonight through Thursday, winds will increase over
the coastal waters, particularly along the Atlantic side. This will
result in choppy to rough seas and an elevated likelihood of rip
currents, especially across the northern and eastern exposed
beaches. Beachgoers should exercise caution and avoid swimming in
high-risk areas.

In addition, isolated to scattered thunderstorms are expected each
day. Thunderstorms near the coast can bring dangerous cloud-to-
ground lightning, gusty winds, and locally heavy rainfall that could
lead to sudden reductions in visibility. Remember: if thunder roars,
go indoors. Swimmers and boaters should immediately move to safety
when storms approach.

&&

.HYDROLOGY...

/From previous discussion issued at 126 PM AST Mon Sep 22 2025/

As a robust tropical wave approaches the islands, conditions will
become increasingly favorable for flooding across Puerto Rico and
the Virgin Islands. The heaviest rainfall is anticipated late on
Wednesday into early Thursday.

Some of the factors that will work in favor of the rainfall event
are that moisture content is expected to be above normal, and the
wave is expected to be well defined from the surface to the mid-
levels too. This will result in a period of increased showers, with
the heaviest activity focusing over the vicinity of the Virgin
Islands and the northern and eastern portions of Puerto Rico. So
far, rainfall accumulations are expected to range from 2 to 4
inches, with isolated amounts up to 6 inches for the period of
Tuesday-Thursday.

Previous rains across the islands have led to saturated soils along
the northern and western half of Puerto Rico, St. Thomas and western
St. Croix, according to the latest National Soil Moisture Analysis
from the National Water Model. Also, data from the Puerto Rico
Agricultural Water Management Program further suggest saturation
along most of western Puerto Rico and St. Croix. Most of the rivers
monitored by the US Geological Survey indicate that streams are
running near normal, with the exception of a couple of rivers in the
east-southeast that are running just below the 25% percentile. Areas
that are saturated or where river flows are above normal will react
quicker, as most of the rainfall will turn into excessive runoffs
and flows.

Hazards and impacts associated with this event are expected to be
urban and small stream flood, while isolated flash flooding cannot
be ruled out. Landslides in areas of steep terrain, water surges,
rapid river rises, and some streams reaching flood stage are also
expected.

Users that live or work near flood prone areas should monitor the
weather in the upcoming days, and stay tuned to any flood product
issued by this Weather Forecast Office.