Caribbean - Central America Weather

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cycloneye
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Re: Caribbean - Central America Weather

#21921 Postby cycloneye » Tue Sep 02, 2025 4:17 am

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.
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Re: Caribbean - Central America Weather

#21922 Postby cycloneye » Wed Sep 03, 2025 4:40 am

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.
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Re: Caribbean - Central America Weather

#21923 Postby cycloneye » Thu Sep 04, 2025 4:58 am

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.
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Re: Caribbean - Central America Weather

#21924 Postby cycloneye » Fri Sep 05, 2025 4:51 am

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.
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Re: Caribbean - Central America Weather

#21925 Postby cycloneye » Sat Sep 06, 2025 5:01 am

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.
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Re: Caribbean - Central America Weather

#21926 Postby cycloneye » Sun Sep 07, 2025 4:57 am

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.
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Re: Caribbean - Central America Weather

#21927 Postby cycloneye » Mon Sep 08, 2025 4:17 am

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.
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Re: Caribbean - Central America Weather

#21928 Postby cycloneye » Tue Sep 09, 2025 4:00 am

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.
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Re: Caribbean - Central America Weather

#21929 Postby cycloneye » Wed Sep 10, 2025 4:23 am

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.
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Re: Caribbean - Central America Weather

#21930 Postby cycloneye » Thu Sep 11, 2025 4:40 am

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.
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cycloneye
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Re: Caribbean - Central America Weather

#21931 Postby cycloneye » Fri Sep 12, 2025 4:00 am

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.
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