Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
522 AM AST Mon Aug 26 2024

.SYNOPSIS...East to southeast flow will prevail across the area
with a tropical wave moving through on Tuesday, a drier Wednesday
and another surge of moisture on Thursday. Temperatures will be
above normal through at least Thursday although some relief is
expected on Tuesday due to the increased rainfall.


&&

.SHORT TERM...Today through Wednesday

The night remained relatively calm, with a few isolated showers
mostly across the waters. Overnight low temperatures ranged from the
upper 70s to low 80s in the lower elevations, while the higher
elevations saw temperatures in the upper 60s to mid-70s.

Today, precipitable water values will begin to increase to near-
normal levels as the leading edge of a tropical wave approaches from
the southeast. Expect a few isolated to scattered showers in the
morning over the waters, the USVI, and eastern Puerto Rico, followed
by thunderstorms in the afternoon across western and northwestern
Puerto Rico under a southeasterly wind flow. Scattered showers and
isolated thunderstorms are also forecast for eastern Puerto Rico
this afternoon, including the San Juan Metro area, as streamers may
develop downwind of smaller islands and mountainous features like El
Yunque. Heat indices will soar today as high moisture content
combines with high temperatures due to a southerly flow.

As the tropical wave continues to advance, moisture content will
rise to well above normal levels, increasing the potential for
shower activity. Conditions aloft will also become favorable for
convective development as cold air advection leads to cooler
temperatures at 500 mb and steep lapse rates between 700-500 mb. As
a result, widely scattered to locally numerous showers, with a few
thunderstorms, are expected at various times across the local waters
and islands. Given the expected wind flow, portions of eastern
Puerto Rico, the San Juan Metro, and the northwestern quadrant of
Puerto Rico are likely to experience the most persistent showers and
thunderstorms. Urban and small stream flooding could be a
significant concern in these areas on Tuesday. Additionally, due to
the increase in moisture, heat index values could rise to just over
105 degrees across north-central Puerto Rico by late morning into
early afternoon before the cloudiness and shower activity bring some
cooling in the afternoon.

Drier air and some Saharan dust may return on Wednesday, which could
slightly reduce the potential for showers and thunderstorms across
the local area. However, it won't completely eliminate the chances,
so scattered showers and isolated thunderstorms are still expected
on Wednesday afternoon. Otherwise, the general pattern will remain
typical, with most afternoon convection occurring across western
Puerto Rico.

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

The high pressure that nosed into the area from the northeast on
Tuesday, will be in the area on Thursday. An upper level trough
will move into the area and the southeast Caribbean, on Friday and
Saturday. Nevertheless the influence of high pressure aloft will
return to the area from a high to the northwest beginning next
week. After a narrow band of moisture passes through on Wednesday
night flow appears to be relatively homogenous and easterly under
the influence of high pressure at 700 mb in the mid Atlantic. A
weak trough with areas of enhanced moisture will move through on
Saturday with east southeast to southeast flow following. The
entire period will be characterized by normal to above normal
moisture with precipitable water values ranging from 1.75 to 2.25
inches and the best moisture of the week on Saturday (just behind
the peak late Wednesday). This will bring diurnally typical
weather to the area, with isolated thunderstorms each afternoon in
the west northwest portions of Puerto Rico and its interior and
scattered showers each night and early morning for the windward
side of eastern Puerto Rico. Limited shower activity is expected
for the U.S. Virgin Islands. Temperatures will remain somewhat
above normal with Thursday and Sunday the highest of the period by
a small margin.

&&

.AVIATION...
(06z TAFs)

Generally VFR conds expected. ISOLD TSRA may cause at least VCTS at
TJSJ and TJBQ after 26/17Z. Mtn top obscr due to aftn convection
over the interior sections of PR. SFC winds from the ESE at around
10-15 kts with sea breeze variations and a few gusts.

&&

.MARINE...Seas will remain benign through the period with 3 to 4
feet in the open waters and 2 or less feet in protected waters.
Swell still continues from the northeast.

&&

.BEACH FORECAST...A moderate risk of rip currents continues on the
north coast of Puerto Rico, fading by mid week, but Wednesday
should see a low risk for all beaches in the forecast area.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
501 AM AST Tue Aug 27 2024

.SYNOPSIS...

Variable weather conditions will prevail throughout the period, with
showers and thunderstorms affecting the interior and western Puerto
Rico each afternoon. Above-normal temperatures and high heat indices
will persist, posing a risk for those without effective cooling or
adequate hydration.

&&

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

Trade wind showers were increasing across the local waters during
the early morning hours. This surge in moisture content will aid
once again today in the development of showers and thunderstorms
across portions of the islands. Light easterly steering winds will
favor once again slow-moving storms over the interior and western
sections of PR, where the highest rainfall accumulations are
expected. The Doppler radar estimated between 2 and 4 inches of rain
across these areas on Monday, and similar amounts can be expected.
Urban and small stream flooding, as well as localized flash flooding
and mudslides in areas of steep terrain are likely to happen with
the heaviest showers.

Dewpoints in the low 80s and light winds will also cause higher than
normal heat indices across the lower elevations of most coastal
municipalities, and in St. Croix. Therefore, a Heat Advisory
(NPWSJU) was issued for portions of the islands. Please refer to the
latest NPWSJU for detailed information.

For Wednesday, a drier air mass will move from the east and across
the islands through midday, the precipitable water content is
expected to drop below normal values around 1 to 1.50 inches with
fair weather conditions prevailing through most of the day. However,
moisture picks up quickly before sunset as a tropical wave streams
across the local area, increasing PWAT values between 2-2.25 inches
through the night. Therefore, a late onset of afternoon showers with
isolated thunderstorms is still expected to develop downwind of the
USVI, and across the eastern interior and western PR. Also, a wind
surge and a weak Saharan Air Layer will accompany the wave passage,
and periods of hazy skies can be expected. On Thursday, moderate to
locally fresh trade winds with a slight ENE wind component from a
700 mb high near 28N are expected to promote passing showers with
light rainfall amounts across the USVI, and favor the development of
diurnally induced afternoon showers with iso thunderstorms over
west/southwest PR.

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

A low to mid-level ridge will anchor across the western Atlantic
during the long-term forecast period. The forecast area will remain
on the southern to southwestern edge of this ridge, resulting in
marginal instability aloft. However, a series of tropical waves and
surface perturbations will sustain moisture levels from normal to
above normal, particularly from this weekend onward, with
precipitable water fluctuating between 1.75 inches and nearly 2.20
inches at times. This weather setup will lead to variable conditions
across the region, with the development of showers and thunderstorms
highly dependent on the prevailing wind steering flow. Orographic
factors will also play a significant role, particularly in driving
diurnal convection, which could enhance storm activity in certain
areas.

As a result, localized weather patterns may vary, with some regions
experiencing more frequent and intense showers. Model guidance
suggests the highest rainfall accumulations are expected across
interior and western Puerto Rico. Therefore, a limited to elevated
flood threat is anticipated each day of the long-term forecast. With
frequent showers in some areas, quick river rises, river flooding,
and landslides are likely.

The National Hurricane Center (NHC) is monitoring an active area
across the central tropical Atlantic with a low probability of
tropical cyclone formation in the next seven days. While it's too
early to determine any potential impact on our forecast area, it’s
advisable to stay informed, especially as we enter the peak of
hurricane season.


&&

.AVIATION...
(06Z TAFS)

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. However, trade wind SHRA could move at
times across the USVI and eastern PR terminals throughout the day.
Afternoon SHRA/TSRA is expected to develop btw 27/18z-22z in the
vcty of TJSJ/TJPS/TJBQ. This may cause tempo MVFR conds and mtn tops
obscd. East winds expected at 8-15 kt with locally higher gusts and
sea breeze variations aft 27/14z.

&&

.MARINE...

Surface high pressure over the Atlantic and a weak surface trough
will promote moderate east winds through most of the work week.
Passing showers will move across the coastal waters, mainly during
the overnight and early morning hours, followed by afternoon shower
development mainly downwind of the local islands each afternoon, with
strongest activity moving over the Mona Passage. The coverage of
showers and thunderstorms across the local waters and passages are
forecast to increase by this afternoon.

&&

.BEACH FORECAST...

Rip current risk has continued to diminish with a moderate risk
of rip currents across the northern and northwestern coast of
Puerto Rico. Low risk elsewhere, however, life- threatening rip
currents often occur in the vicinity of groins, jetties, and
piers.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
340 AM AST Fri Aug 30 2024

.SYNOPSIS...

Expect showery weather today. By the afternoon, the activity will
focus on the western interior and far western sections of Puerto
Rico, where there will be a risk of excessive rainfall and
lightning. This diurnal pattern is expected to persist over the
weekend and into early next week until the passage of the next
tropical wave over the eastern Caribbean region. Currently, this
has a moderate formation chance. The anticipated heat level will
pose a risk to vulnerable individuals, especially those outdoors
without adequate cooling or hydration. Additionally, locally
choppy conditions for small craft and a moderate rip current risk
will persist over the next few days.

&&

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

Passing showers and isolated thunderstorms were observed during the
early morning hours across the Anegada Passage and the eastern
coastal waters of PR and the USVI. Minor rainfall amounts over land
areas were observed with this activity. Minimum temperatures were in
the low 80s across the lower elevations of the islands, and in the
low-to mid-70s across the higher elevations. The wind was from the
east at 10 mph or less.

For today, a small surge in moisture from the east combined with
daytime heating and the sea breeze convergence will aid in the
development of showers and thunderstorms over portions of the
interior and western PR. These thunderstorms could produce gusty
winds, and locally heavy rainfall that can lead to urban and small
stream flooding. Once again, hot temperatures and dewpoints in the
low 80s will cause excessive heat conditions across most coastal
areas of the islands, a Heat Advisory and Excessive Heat Warning
(NPWSJU) are in effect.

Winds are expected to shift from the east to southeast later in the
short-term period. However, similar weather condtions are expected
on Saturday and Sunday, as pockets of moisture will bring passing
showers across the windward areas of the islands during the night,
followed by diurnally induced afternoon showers and thunderstorms
over the interior and northwestern PR. Heat advisory conditions will
likely continue each day due to max temps in the low-to mid-90s with
dewpoints in the low 80s across most lower elevations of the
islands.

&&

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

At this time, there is some discrepancy between the models, which
is normal due to how far in time the system of interest is. The
Global Forecast System (GFS model) suggests that the now tropical
wave will move south of Puerto Rico and the U.S. Virgin Islands by
late Monday into Tuesday. Based on the GFS, the passage of this
wave to the south of us will increase the precipitable water
values to 1.8 to 2.0 inches (near normal), and most of the
moisture content will stay at the low levels of the atmosphere.
However, the European Center for Medium-Range Weather Forecasts
(ECMWF model) suggests that the system will move closer to the
forecast area by mid-week but as a well-developed low-pressure
system, allowing precipitable water values to increase to 2.00 and
2.30 inches (above normal values for this time of the year).
Despite the discrepancy between the well-known models, we suggest
people stay updated with the changes that may arise as we get
closer in time. That being said, the National Hurricane Center
continues to give this tropical wave over the central Tropical
Atlantic a 50 percent chance of development in the next 7 days. In
other words, this wave has a medium percent change in
development.

The current long-term forecast leans towards what the GFS is suggesting
by having the tropical wave move to the south and increasing the
precipitable water to normal and slightly above normal. Due to the
proximity of this wave, we anticipate an increase in shower and
thunderstorm activity across the islands on both days. Some of the
potential hazards of this weather event are urban and small-
stream flooding, as well as localized flash flooding, which can be
expected too.

On Thursday, expect to see a gradual change in weather conditions
as a mass of dry air will filter across the islands from the
east, reducing the precipitable water values to the 50th (near
normal )and 25th percentile (below normal). However, diurnally
induced afternoon showers and thunderstorms are expected to
develop over the interior and western sections of PR while passing
trade wind showers with lighter rainfall amounts are expected
across the USVI.

By the end of the workweek into the weekend, the latest model guidance
suggests the passage of another tropical wave. Nonetheless, it is
too early to determine the direct impact that this could have on
Puerto Rico and the U.S. Virgin Islands.

&&

.AVIATION...
(06Z TAFS)

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. However, SHRA and iso TSRA en route fm the
Leeward Islands may cause tempo MVFR conds at TIST/TISX thru 30/12z.
Diurnally induced afternoon SHRA/TSRA over western PR may cause
brief MVFR cigs at TJPS/TJBQ btw 30/18z-22z. East winds expected at
12-16 kt with locally higher gusts and sea breeze variations aft
30/14z.

&&

.MARINE...

Expect lighter winds through Saturday. Moderate to locally fresh
easterly winds will dominate over the next few days. Isolated to
scattered showers are expected across the local waters, with isolated
thunderstorms affecting the coastal waters of western Puerto Rico
each afternoon. Consequently, locally choppy conditions for small
craft are likely. The passage of the next tropical wave could further
deteriorate marine conditions by next week.


&&

.BEACH FORECAST...

Moderate rip current risk should prevail across northern and
eastern Puerto Rico, Culebra, Vieques, St. Thomas, and St. John
today.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
529 AM AST Sun Sep 1 2024

.SYNOPSIS...
We expect another day with a warmer-than-normal heat index (HI),
especially across the southern sections of PR and St Croix, where
Excessive Heat Warnings are in effect. Heat Advisories are in
effect for the rest of the coastal urban areas in PR and USVI. The
diurnal heating, sea breeze variations, and local effects will
result in strong afternoon convection over northwest PR. A wet
pattern may evolve from late Monday through early Wednesday due to
the passage of a tropical wave. Fragments of moisture will arrive
through the second part of the workweek, contributing to our
typical wet September weather pattern. A drier pattern could
develop by next weekend.

&&

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

Like previous nights, showery weather prevailed across eastern
Puerto Rico, Culebra, Vieques, and the U.S. Virgin Islands, with the
most frequent rainfall and highest concentrations mainly over the
Atlantic and Caribbean waters. Winds were generally light and out of
the east. The minimum temperatures overnight ranged in the low 80s
to upper 70s along the coast, while over the mountainous areas, they
were in the upper 60s to low 70s.

The driest day of the short-term period should be today, with
precipitable water values staying in the 25th percentile or below
normal values for this time of the year, as a dry air mass with
slight concentrations of Saharan Dust particles will filter across
the region. Despite the anticipated reduction in moisture content,
we forecast the frequent trade wind showers across the islands but
with the highest potential for rainfall and isolated thunderstorms,
taking place particularly across the western sections of Puerto Rico
in the afternoon. The latest model guidance suggest stable
conditions at the mid to upper leves of the atmosphere meaning that
any rainfall activity that does develop will not have enough chance
to grown in thee vertical. This weather pattern will maintain the
risk of localized excessive rainfall and lightning hazards today.

Besides the typical development of afternoon showers and
thunderstorms over the west, and the frequent passage of showers,
the main thread for today is the persistent excessive heat levels
across the islands. This warm weather pattern will be a risk to
vulnerable individuals, particularly those outdoors without adequate
cooling or hydration. As a result, a Heat Advisory was issued for
the northern, western, and southeastern coastal/urban areas of
Puerto Rico, Culebra, Saint Thomas, and Saint John, while an
Excessive Heat Warning was issued for the south central to
southwestern section of PR and Saint Croix were the rainfall
activity will be limited. Nonetheless, we encourage people to stay
updated on any changes in today's forecast.

At this time, late Sunday into Monday looks like the transitional
days into a wetter pattern. This gradual change in weather
conditions will be associated with the tropical wave that the
National Hurricane Center continues to monitor near the Lesser
Antilles and the Caribbean Sea. The latest Tropical Weather Outlook
keeps it in the medium range (40 percent change) for development in
the next 7 days. At this time, the forecast models maintain the bulk
of the moisture south of Puerto Rico and the U.S. Virgin Islands by
Tuesday. However, moisture and rainfall associated with this wave
will reach the islands Monday into Tuesday, being Tuesday the
wettest day of the period.

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

At this time, the weather forecast for Wednesday may be driven by
the trailing moisture of Tuesday's tropical wave exiting the
region. This may result in passing showers across the local waters
moving inland at times, followed by strong afternoon convection
mainly north and west of the Cordillera Central in Puerto Rico and
downwind from the US Virgin Islands.

The proximity of an upper-level trough northeast of the region
will enhance the arrival of fragmented moisture embedded in the
easterlies Thursday into Friday under the typical diurnal rain
pattern. Model guidance suggests that moisture may erode by next
weekend, limiting rain activity. However, due to the influence of
sea breezes, we expect one or two strong afternoon thunderstorms.

&&

.AVIATION...
(06Z TAFS)

VFR conditions should prevail across all terminals. However, SHRA
and iso TSRA en route fm the Atlantic and Leeward Islands may cause
tempo MVFR conds at TIST through 01/14z. Diurnally induced afternoon
SHRA/TSRA over western PR may cause brief MVFR at TJBQ and TJSJ btw
01/16z-22z. E winds expected at 6-18 kt with locally higher gusts
and sea breeze variations aft 01/14z.

&&

.MARINE...
Moderate to locally fresh easterly winds will dominate over the next
few days. Isolated to scattered showers are expected across the local
waters, with isolated thunderstorms affecting the coastal waters of
western Puerto Rico each afternoon. Consequently, locally choppy
conditions for small craft are likely. The passage of the next
tropical wave could further deteriorate marine conditions by
Monday night into Tuesday.

&&

.BEACH FORECAST...

Beachgoers can expect a low risk of rip currents along the west
and southern coasts of PR, Vieques, and northern USVI. However,
there is a moderate risk of rip currents along the north and east-
facing beaches of north and east PR, Culebra, and St Croix.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
502 AM AST Mon Sep 2 2024

.SYNOPSIS...

Unstable weather conditions are expected today across the islands
due to the arrival of a tropical wave. Heavy showers and
thunderstorms are anticipated with this wave, resulting in
localized flooding and mudslides across the higher elevations due
to saturated soils. After the wave passage, trailing moisture
will result in afternoon showers ans isolated thunderstorms across
the interior and western Puerto Rico each day. Hot and warm
temperatures will continue for the next several days.

&&

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

The leading edge of an approaching tropical wave favored the
formation of showers and thunderstorms across the local waters
overnight, and some of them moved inland mainly across the north,
east, and southeast coast of PR and the USVI. Ponding of water in
roads and poorly drained areas was observed due to occasional
moderate to locally heavy rain. Low temperatures ranged from the mid-
70s to low-80s along the coastal areas to the upper 60s to low-70s
along mountains and valleys. The winds were mainly from the east at
5 to 10 mph.

We anticipate a wet and unstable weather pattern across the islands
today and tomorrow due to the arrival of a tropical wave. This wave
will result in occasional showers and thunderstorms. Under this
weather pattern, residents and visitors can expect an elevated
chance to observe flooding due to periods of heavy rain due to
isolated scattered thunderstorms. This morning, the activity will
move from the regional waters into the USVI and the northeast,
north, east, and southeast PR, spreading then into the rest of
mainland PR by the afternoon. Additionally, the available moisture
combined with the diurnal heating will result in muggy, unpleasant
temperatures across the areas where showers do not form or move on.

On Tuesday, winds will become more east-southeast, pooling
additional moisture into the islands and extending the unsettled
weather pattern. The trailing moisture of Tuesday's tropical wave
exiting the region may drive Wednesday's weather forecast. This will
result in passing showers across the local waters, moving inland at
times, followed by strong afternoon convection mainly north and west
of the Cordillera Central in Puerto Rico and downwind from the US
Virgin Islands.


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

An upper-level trough in the proximity of the northeastern Caribbean
is expected to enhance unstable conditions across the region for the
first half of the long-term period. Patches of moisture embedded
with the trade winds are forecast to reach the local area from
Thursday into Saturday. This moisture in combination with local
effects and daytime heating, will help to produce heavy showers and
isolated thunderstorms across the interior and western portions of
Puerto Rico every afternoon. Then, during the overnight into the
morning hours shallow moisture will produce light passing showers
across the U.S. Virgin Islands and eastern Puerto Rico. Winds will
be from the east, and becoming from the southeast on Friday through
the rest of the period.

By the weekend, a similar weather pattern is expected with showers
and afternoon thunderstorms over western Puerto Rico and likely
downwind of el Yunque, producing the San Juan streamer each day.
With the expected activity, minor flooding is possible and saturated
soils could lead to mudslides in higher terrain. Hot conditions will
continue with elevated heat threat across the region. Maximum
temperatures could reach the upper 80s to low 90s along the coastal
and urban portions of the islands to the mid 80s in the higher
mountain elevations each day.

&&

.AVIATION...
(06Z TAFs)

Unsettled weather conditions due to an approaching tropical wave.
SHRA/TSRA will develop across the local flying area, and may impact
local terminals. Nmrs SHRA/TSRA are expected to dvlp ovr PR/USVI aft
02/14Z and may impact TJSJ/IST/ISX at that time sprdg wwd during the
day. Mtn obscurations will form along mainland PR from mid-morning
onward. TEMPOs are in place due to the possibility to observe MVFR
conds. Expect winds mainly from the E at 10 to 15 knots, with strong
gusty winds and sea breeze variations.

&&

.MARINE...

Moderate to locally fresh easterly winds will dominate over the next
few days. Isolated to scattered showers are expected across the local
waters, with isolated thunderstorms affecting the coastal waters of
western Puerto Rico each afternoon. Consequently, locally choppy
conditions for small craft are likely. The passage of a tropical
wave today could further deteriorate marine conditions by tonight
into Tuesday.


&&

.BEACH FORECAST...

The rip current risk will remain moderate for the north-facing
beaches of Puerto Rico, Culebra and eastern Saint Croix. Rip
current risk will increase by midweek as a strong tropical wave,
currently monitored by the National Hurricane Center, moves over
the Caribbean waters.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
447 AM AST Tue Sep 3 2024

.SYNOPSIS...

Unstable and wet weather conditions are expected today, once
again, across the region as trailing moisture associated to a
passing tropical wave continue to move over the islands. As a
result, showers and thunderstorms are expected across the
interior and western Puerto Rico in the afternoon. The development
of the "San Juan streamer" may result in additional shower
activity for the San Juan metro area today. Hot and warm
temperatures will continue for the next several days.

&&

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

A tropical wave crossing the islands promoted showers and
thunderstorms across the local waters, with some of them moving
inland, mainly across the windward sections of the USVI and PR.
Skies were from partly to mostly cloudy, and once again, low
temperatures ranged from the mid-70s to low-80s along the coastal
areas to the upper 60s to low-70s along mountains and valleys. The
winds were mainly from the east to east-southeast at 5 to 10 mph but
with stronger gusts near and around rain activity.

The unstable and wet pattern will continue today as the passing
tropical wave promotes the development of showers and thunderstorms
across the regional waters and the US Virgin Islands and PR. Soils
are saturated, and some rivers are running near to above normal,
creating favorable conditions to observe sudden landslides and river
flooding with today's persistent heavy rain. Therefore, we forecast
limited to elevated flooding threat for most of Puerto Rico and the
USVI. Today, winds will be mainly from the east-southeast, pooling
abundant tropical moisture over the islands, which, combined with
the diurnal maximum heating, will result in muggy, unpleasant
temperatures across the areas where showers do not form or move on.

The trailing moisture of today's tropical wave combined with
fragments of moisture from trade wind perturbations induced by the
proximity of a retrogressive upper-level trough will drive
Wednesday's weather forecast. This will result in the typical
diurnal rain pattern, with passing showers across the local waters,
moving inland at times, followed by strong afternoon convection
mainly along and west of the Cordillera Central in Puerto Rico and
downwind from the US Virgin Islands. The upper-level trough will
move further southward increasing instability and extending the
unsettled weather pattern into Thursday.


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

The proximity of a migrating upper-level trough across in the
northeastern Caribbean will continue to promote instability
across the local islands through much of the period. Fragments of
moisture will reach the islands from Friday through Sunday,
enhancing the potential for shower and thunderstorm development.
The latest Precipitable Water Content analysis (PWAT) suggest
values from 1.90 to 2.10 inches for the first half of the period.
Therefore, there is the potential to observe heavy shower activity
and possibly isolated thunderstorms mainly across the interior
and western region of Puerto Rico during the afternoon hours.
Southeast winds will prevail through Sunday. Then winds are
expected to become from the northeast as the next tropical wave
approaches the region on Monday.

The National Hurricane Center (NHC) is currently watching a tropical
wave located south of the Cape Verde islands with a medium formation
chance of 40% through the next seven days. There is a big
uncertainty with the future of this system as it moves slowly west-
northwestward or northwestward over the eastern tropical Atlantic
Ocean. However, some of the latest guidances move this system over
the open Atlantic and near the region by next week as a strong
tropical wave. Therefore, an increase in shower activity associated
to this wave will be observed by the beginning of the next
workweek. Please continue to monitor the latest NHC and WFO San
Juan forecast for future updates.

&&

.AVIATION...
(06Z TAFs)

The unsettled weather conditions continues due to a tropical wave.
SHRA/TSRA will develop across the local flying area, and may impact
local terminals. Nmrs SHRA/TSRA are expected to dvlp ovr PR/USVI aft
03/14z and may impact TJSJ/IST/ISX at that time sprdg wwd during the
day. Mtn obscurations will form along mainland PR from mid-morning
onward. Expect winds mainly from the E/ESE at 10 to 15 knots, with
strong gusty winds and sea breeze variations aft 03/13z.

&&

.MARINE...

Moderate to locally fresh easterly winds will dominate over the next
few days. Scattered thunderstorms affecting the coastal waters of
western Puerto Rico are expected each afternoon. The passage of a
tropical wave will continue to result in deteriorated marine
conditions through today. Locally choppy conditions for small craft
are expected.

&&

.BEACH FORECAST...

The rip current risk will remain moderate for the north, south and
eastern facing beaches of Puerto Rico, Culebra, Vieques and the
U.S. Virgin Islands. A moderate risk will continue through the end
of the workweek.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
429 AM AST Wed Sep 4 2024

.SYNOPSIS...

Another day with hot conditions across the islands. Above- normal
temperatures in combination with humidity will result in high
heat indices. Therefore, and Excessive Heat Warning and a Heat
Advisory will be in effect from this morning through late in the
afternoon across the urban and coastal areas of Puerto Rico and
Saint Croix. Afternoon showers and thunderstorms are expected,
once again, across the interior and western portions of Puerto
Rico.

&&

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

Local weather stations reported high humidity values, above-normal
low temperatures, and light and variable wind, mainly from the east,
under the land breeze fluctuations overnight. The GOES-E infrared
channel detected cloudy skies due to mid- to upper-level clouds
associated with a tropical wave south of Hispaniola and low-level
clouds due to trade wind showers. The Doppler Radar detected
scattered to numerous showers across the local waters, and some of
them moved across the US Virgin Islands and the eastern half of PR.

Today, expect another day with above-normal high temperatures and
humidity. These combined will result in dangerous heat indices
values that could cause heat-related illness, especially in the most
vulnerable communities. Therefore, an Excessive Heat Warning and a
Heat Advisory are in effect for the coastal urban areas in PR and St
Croix. Regardless of the muggy and hot heat indices, trade wind
perturbations will bring some showers across the local waters and
windward sections, followed by afternoon convection across portions
of PR and downwind from the USVI. The most intense thunderstorms
could result in an elevated risk of flooding, frequent lightning,
and strong gusty winds, especially across western PR during the
afternoon.

Instability will begin to increase later this evening into Thursday
as a retrograding TUTT moves from the Central Atlantic near the
USVIs, leaving the region in a favorable position for the
development of showers and thunderstorms. Therefore, there is a
moderate to high chance of scattered to numerous showers and
thunderstorms across the local waters on early Thursday morning, and
they may spread into the windward sections of the islands. Although
we can anticipate some breaks in the rain activity, by Thursday
afternoon, another round with periods of moderate to locally heavy
rain due to thunderstorms could form again. On Friday, we may have
another day with afternoon convection under the typical hydrological
cycle for the US Virgin Islands and Puerto Rico. The warm-to-hot
spell may also continue throughout the short-term period, and we
could expect muggy, unpleasant temperatures across the areas where
showers do not form during the diurnal heating peak.

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

A retrograding upper-level trough northeast of the region will
continue to dominate the local weather for the first few days of the
long-term period. Limited convective activity is anticipated on
Saturday and Sunday across the region. However, sufficient
moisture in combination with local effects and daytime heating
may result in showers and thunderstorms over the interior and
western Puerto Rico. The precipitable water content of 1.75 and
1.90 inches suggest relatively normal moisture values across the
islands. By Sunday night, a tropical wave that is currently being
monitored by the National Hurricane Center with a low formation
chance of 10% is forecast to reach the islands. Therefore,
enhancing the potential for showers and thunderstorms. Trailing
moisture associated to this wave will continue to produce
convective activity throughout the islands until the end of the
period. Hot and muggy conditions will also continue for the next
several days. Maximum temperatures could reach the upper 80s to
low 90s along the coastal and urban portions of the islands to the
mid 80s in the higher mountain elevations each day.


&&

.AVIATION...
(06Z TAFs)

Expect VFR conds during the fcst prd. However, if some SHRA/+SHRA
impacts the local terminals, they could create brief MVFR cond. The
chance to observe TSRA/+SHRA will increase by between 04/16z-22z and
late tonight 05/02z-10z. Most afternoon activity may remain along
and west of the Cordillera, but the overnight activity could affect
the northern terminals of PR and the USVI. Expect calm to light/var
winds thru 04/13, when the easterlies should return with speeds btwn
10-18 kt with stronger gusts and sea breeze.

&&

.MARINE...

Winds and seas will gradually continue to subside today. Nonetheless,
small craft operators should continue to exercise caution across most
marine zones. Moderate to locally fresh easterly winds will dominate
over the next few days. Thunderstorms affecting the coastal waters
of western Puerto Rico are expected each afternoon.

&&

.BEACH FORECAST...

The rip current risk will remain moderate for the north,
southeastern and eastern facing beaches of Puerto Rico, Culebra,
Vieques and St. Croix. A moderate risk will continue through the
end of the workweek, becoming low by Saturday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
509 AM AST Fri Sep 6 2024

.SYNOPSIS...

An upper-level trough approaching from the northeast will promote
shower and thunderstorm activity today through the weekend.
Additionally, a tropical wave will reach the forecast area this
weekend, further enhancing instability and increasing rainfall
during this wet period.

&&

.SHORT TERM...Friday through Sunday...


Tradewind showers were observed during the overnight hours over
eastern Puerto Rico and the U.S. Virgin Islands, leaving minimal
accumulations. However, showers and few isolated thunderstorms were
observed over the local Caribbean and Atlantic waters. Another warm
night was observed across the islands. Minimum temperatures were
seen in the upper 70s to low 80s along the coastal and urban sectors
of Puerto Rico, and in the low to mid 70s across the higher
elevations. Winds were mostly calm and variable at less than 5 mph.

Today, weather conditions will be similar to yesterday due to the
influence of a retrograding TUTT low located northeast of the Virgin
islands. Instability generated by this upper level system will
enhance the potential for strong convective activity across the
area. Areas of central, western, and northwestern Puerto Rico will
observe heavy showers and thunderstorms in the afternoon hours.
Periods of heavy rain may lead to urban flooding and quick river
rises. Soils across Puerto Rico are very saturated due to the
previous rain events. Therefore, the potential for mudslides remains
high. Across the San Juan metropolitan area, the "El Yunque
streamer" is expected to form later in the afternoon, resulting in
showers and isolated thunderstorms. This activity may result in
hazardous driving conditions due to urban flooding and low
visibility. Weather conditions are expected to gradually improve
before sunset.

On Saturday, a wind surge ahead of a tropical wave, will result in
an increase in moisture and showers across the region. By early
Sunday into the middle of the upcoming workweek, a tropical wave
will approach the islands bringing periods of showers and
thunderstorms. Therefore, the potential for excessive rainfall
remains elevated for the next several days.

Across the U.S. Virgin Islands, mainly fair weather conditions will
persist each day. Passing showers dragged by the tradewinds will
reach the islands and local waters every morning. Today, showers and
isolated thunderstorms may affect the region due to the proximity of
the TUTT low. As a result, ponding of water in roads and poorly
drainage areas is possible along with urban and small stream
flooding.

Hot conditions are likely to continue for the next several days with
with a elevated heat threat. Highs will reach the low to mid 90s
along the coastal and urban areas. For today, an Excessive Heat
Warning is in effect for Saint Croix, and a Heat Advisory is in
effect for the coastal urban areas of Puerto Rico. Residents and
visitors should take precautions to stay hydrated by drinking plenty
of water, wearing light and breathable clothing, and avoiding
prolonged exposure to the sun, especially during peak heat hours.

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

Troughing aloft will persist throughout much of the long-term
forecast period, with cold air advection promoting steep lapse rates
and favorable vorticity aloft, enhancing conditions for convective
activity. Abundant tropical moisture will be present, with
precipitable water content (PWAT) remaining well above 2.0 inches.
PWAT values will fluctuate between the 75th and 90th percentiles,
occasionally exceeding the 90th percentile compared to
climatological normals for this time of year. Additionally, the
Global Tropics Hazards Outlook from the Climate Prediction Center
(CPC) indicates a greater than 50% probability of above-average
rainfall across the northeastern Caribbean during this period.

As a result, expect variable weather conditions with active
afternoon, as unstable weather and tropical moisture combines with
surface heating and orographically driven convection. The most
favorable conditions for significant weather are expected by early
next week, leading to an elevated to significant flooding threat,
particularly over interior and western Puerto Rico. By the end of
the week, a weak mid-level ridge will begin to settle in, somewhat
reducing the instability aloft. Nevertheless, afternoon convection
across interior and western portions of Puerto Rico is still likely.

The National Hurricane Center (NHC) is monitoring an active area in
the central tropical Atlantic, with a low probability of tropical
cyclone formation over the next seven days. While it's too early to
assess any potential impact on our forecast area, it is advisable to
stay informed, especially as we are currently in the peak of
hurricane season.


&&

.AVIATION...
(06Z TAFs)

Expect mainly VFR conds during the fcst prd. Tradewind showers will
result in VCSH at TIST/TISX thru 06/14Z, with possible VCTS. The
proximity of an upper level trough will result in afternoon
SHRA/TSRA and may result in brief MVFR conds at TJSJ/TJBQ aft
06/17Z. Mtn top obscd and low cigs expected along the Cordillera
Central thru 06/22Z. Expect calm to light/var winds thru 06/14Z,
when the easterlies should return with speeds btwn 10-15 kt with
stronger gusts and sea breeze.

&&

.MARINE...

Weak pressure gradient will promote light to gentle easterly winds
today. Tonight, gentle to moderate easterly winds will return as the
surface high pressure across the Atlantic strengthens slightly and
persist over the next few days. An upper-level trough moving from
the northeast will promote shower and thunderstorm activity today and
tomorrow across the regional waters. A tropical wave will cross the
Lesser Antilles around Saturday, with its axis moving across the
local region on Sunday. Otherwise, thunderstorms will affect the
coastal waters of western Puerto Rico each afternoon.

&&

.BEACH FORECAST...

A moderate rip current risk will persist over north- and east-
facing beaches of Puerto Rico and St. Croix, persisting through
the weekend. It is important to note that life- threatening rip
currents are still possible in the surf zone of these beaches.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
448 AM AST Sat Sep 7 2024

.SYNOPSIS...

An upper-level trough will promote shower and thunderstorm
activity through the weekend, particularly across the waters,
interior, and western sectors of Puerto Rico, along with an
approaching tropical wave. This wave will cross the Lesser
Antilles today, with its axis later moving across the local region
tomorrow and Monday, further enhancing instability and increasing
rainfall activity. Above-normal heat indices are still expected
to persist across some sectors throughout the next several days.

&&

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

Showers and isolated thunderstorms were increasing from the Anegada
Passage into the coastal waters of eastern PR and the U.S. Virgin
Islands during the early morning hours. Observed rainfall amounts
were around an inch across northeastern PR, and around a quarter or
less across the USVI. Minimum temperatures were in the low 80s
across the lower elevations of the islands, and in the low to mid
70s across the higher elevations. The wind was from the east near 10
mph, but stronger gusts were observed with the showers.

An upper-level low just northeast of the region will continue to
slowly drift northwards through the weekend. This will provide
favorable conditions for thunderstorm development across the local
waters and the islands through the short-term period. In addition, a
tropical wave located just east of the Lesser Antilles will continue
to approach the area and interact with the upper-level low,
producing scattered to locally numerous showers and thunderstorms
from Sunday through Monday. Therefore, the risk for excessive
rainfall will remain elevated, mainly for PR. Saturated soils could
lead to localized flash flooding and mudslides, particularly across
small streams, creeks, and areas of steep terrain. Residents and
visitors should take caution or avoid outside activities during the
afternoon hours. Across the USVI, as showers increase in frequency,
minor flooding could be observed on roads and poor drainage areas.

Although showers are expected to increase, temperatures are still
forecast to reach Heat Advisory conditions across some coastal areas
of the islands due to dewpoints likely reaching the upper 70s to low
80s. High temperatures will reach the low 90s along the coastal and
urban areas of the lower elevations of the islands, before the onset
of diurnally induced afternoon showers.

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

The upper trough that was at or near the islands during the short
term period is forecast to persist through most of the long term
period increasing instability, although weakening past midweek. By
the end of the week, a weak mid-level ridge will somewhat reduce
instability aloft. Precipitable water (PWAT) values will continue
mainly above 2.1 inches for the period, above normal values for this
time of the year. East to east-southeast winds will aid in providing
moisture to the area. Expect variable weather conditions as local,
orographic and diurnal effects generates afternoon convective
activity, boosted by the disturbance aloft and available moisture.
At least through early next week, this convective activity will
increase the risk of flooding during the afternoon for sectors of
interior and western Puerto Rico. Lines of convection (showers and
thunderstorms) can also develop from the USVI, Vieques, Culebra, and
from mountains of Puerto Rico. Periods of passing overnight and
early morning showers are also forecast across windward sectors of
the islands. The Climate Prediction Center's (CPC) Global Tropics
Hazards Outlook indicates a greater than 50% probability of above-
average rainfall across the northeastern Caribbean during this
period. Model guidance indicates a slight increase in Saharan Dust
on Tuesday. With available moisture and east to east-southeast
winds, heat indices in coastal, urban and lower elevation areas can
reach above 108 degrees Fahrenheit. The National Hurricane Center
(NHC) is monitoring an area, currently, in the eastern to central
tropical Atlantic, with a low cyclonic formation chance through the
next seven days. While it's too early to assess any potential impact
on our forecast area, please continue to monitor future updates from
the NHC and form WFO San Juan.

&&

.AVIATION...

(06Z TAFS)

SHRA and -TSRA moving eastward will result in MVFR conds at times
across TIST/TISX/TJSJ thru 07/15z. Thereafter, SHRA/TSRA expected to
spread across the interior and western sections of PR, causing TEMPO
MVFR to brief IFR at TJBQ btw 07/18z-22z. Elsewhere, VCTS expected.
East winds expected at 10-15 kt with locally higher gusts and sea
breeze variations aft 07/14z.

&&

.MARINE...

A surface high pressure across the Atlantic will promote gentle to
moderate easterly winds over the next few days. An upper-level trough
moving from the northeast will promote shower and thunderstorm
activity across the regional waters along with an approaching
tropical wave. This wave will cross the Lesser Antilles today, with
its axis later moving across the local region tomorrow. Otherwise,
thunderstorms will affect the coastal waters of western Puerto Rico
each afternoon.

&&

.BEACH FORECAST...

A moderate rip current risk is present along the northern and
eastern-facing beaches of Puerto Rico and sectors of Culebra. Low
risk elsewhere. It is important to remember that life- threatening
rip currents are still possible in the surf zone of these
beaches.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
445 AM AST Sun Sep 8 2024

.SYNOPSIS...

A tropical upper tropospheric trough (TUTT) to our north and a
broad tropical wave moving in from the east will boost shower and
thunderstorm activity during the next few days. Southeasterly
winds and a high- moisture environment will also contribute to
excessive heat risks. The National Hurricane Center (NHC) is
monitoring an area, currently in the central tropical Atlantic,
with a medium cyclonic formation chance through the next seven
days.

&&

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

An overnight radar and satellite imagery analysis indicated areas
with isolated to scattered showers over the local waters, with
some moving over the Virgin Islands, Vieques, Culebra, and eastern
Puerto Rico. So far, the highest radar-estimated rainfall totals
of around half an inch have been observed in Humacao in eastern
Puerto Rico. Surface observing stations highlighted continuously
warm low temperatures around 80-82 degrees Fahrenheit across the
San Juan metropolitan area, eastern and southeastern Puerto Rico,
and the local islands. In contrast, higher elevations have
reported low temperatures in the upper 60s. Winds were mainly from
the east at 5-10 mph but light to calm and variable further
inland.

The short-term forecast highlights two main weather systems affecting
the region: a meandering tropical upper tropospheric trough
(TUTT) to the north and a broad tropical wave moving in from the
east. Instability from the TUTT will maintain favorable conditions
for thunderstorm development, as supported by the Galvez-Davidson
Index. Meanwhile, the tropical wave will bring abundant moisture,
with precipitable water (PWAT) levels surpassing 2.0 inches. This
combination will likely heighten the risk of excessive rainfall
and lightning over the next few days, with localized heavy rain
from more frequent showers and thunderstorms potentially
triggering flash flooding. This pattern will likely persist over
the next few days, with a higher risk forecast for Monday and
Tuesday, when cooler-than-normal 500 mb temperatures (as low as
-7°C) and well above-normal PWAT levels (around 2.4-2.5 inches)
are anticipated.

The forecast anticipates rainfall distribution following the typical
seasonal pattern, guided by steady east-southeast winds. Daytime
showers with isolated to scattered thunderstorms enhanced by
diurnal heating are expected mainly from late morning into the
afternoon across interior, western, and northern areas and
downwind from the Sierra de Luquillo and the local islands. At
night, strong thunderstorm activity will align with the structure
of the TUTT, primarily impacting the eastern half of the region,
including local waters and passages and portions of the Virgin
Islands, Vieques, Culebra, and eastern Puerto Rico.

Southeasterly winds and a high-moisture environment will contribute to
excessive heat risks, particularly in lower elevation and coastal
areas, even in areas that will likely experience periods of heavy
rainfall throughout the day. As a result, a Heat Advisory is in
effect today for most of these areas, excluding eastern Puerto
Rico, Vieques, and Culebra. For details on excessive heat or other
potential hazards in the coming days, please refer to the
Experimental Graphical Hazard Weather Outlook at
https://www.weather.gov/erh/ghwo?wfo=sju.

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

An upper level trough will be present northeast of the local islands
to start the period, before gradually weakening throughout the
workweek. By the end of the week, a mid-level ridge will reduce
instability aloft. Precipitable water (PWAT) values will continue
mainly above 2.1 inches for the start of the period, above normal
values for this time of the year. East to east-southeast winds will
aid in providing moisture to the area. Expect variable weather
conditions as local, orographic and diurnal effects generates
afternoon convective activity, increasing the risk of flooding
during the afternoon for sectors of interior and western Puerto
Rico. Lines of convection (showers and thunderstorms) can also
develop from the USVI, Vieques, Culebra, and from El Yunque. Periods
of passing overnight and early morning showers are also forecast
across windward sectors of the islands. With available moisture and
east to east-southeast winds, heat indices in coastal, urban and
lower elevation areas can reach above 108 degrees Fahrenheit. The
Climate Prediction Center's (CPC) Global Tropics Hazards Outlook
indicates a greater than 50% probability of above-average rainfall
across the northeastern Caribbean during the period. The National
Hurricane Center (NHC) is monitoring an area, currently in the
central tropical Atlantic, with a medium cyclonic formation chance
through the next seven days. While it's too early to assess any
potential impact on our forecast area, please continue to remain
vigilant and monitor future forecast updates from the NHC and from
WFO San Juan.

&&

.AVIATION...

(06Z TAFS)

Tropical wave will boost SHRA/TSRA development, bringing MVFR to
brief IFR conditions due to reduced visibility and BKN-OVC skies
below FL020-030. TJUA and USVI terminals may experience
operational impacts over the next 24 hours, with TJBQ and TJPS
affected between 08/17-22Z. Easterly winds at 5-10 knots with land
breeze variations, increasing to 10-20 knots after 08/14Z, with
sea breeze variations and stronger gusts, especially near TSRA.


&&

.MARINE...

A surface high pressure across the Atlantic will promote gentle to
moderate easterly winds over the next few days. An upper-level
trough to our north and a broad tropical wave moving in from the east
will boost shower and thunderstorm activity during the next few
days. Thunderstorms will affect the coastal waters of western Puerto
Rico each afternoon.

&&

.BEACH FORECAST...

A moderate rip current risk is present along the northern and
eastern-facing beaches of Puerto Rico and sectors of Culebra. Low
risk elsewhere, however, life-threatening rip currents often
occur in the vicinity of groins, jetties, reefs, and piers.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
457 AM AST Thu Sep 12 2024

.SYNOPSIS...

A variable and wet weather pattern will persist through the end
of the week. Abundant tropical moisture combined with a
southeasterly wind flow will contribute to higher heat indices and
increased afternoon shower activity each day. Heading into the
weekend, Invest 92L is expected to move across the region, further
enhancing cloud cover and increasing the potential for more
widespread shower activity.

&&

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

Skies were partly cloudy to variably cloudy overnight across the
region. Passing showers trailing a weak tropical wave which exited
the region on Wednesday, continued to affect the coastal waters
steered by the light to moderate east southeast trade wind flow.
Some of these showers continue to brush the windward side of the
islands from time to time, but no significant rainfall accumulations
were so far observed. Expect these conditions to persist into the
early morning hours. This will be followed by a gradually clearing
and sunny skies before another round of diurnally induced showers
begin to develop across parts of the islands and downwind during the
afternoon hours. Under the prevailing southeasterly wind flow expect
another hot and humid day with high temperatures in the upper 80s to
low 90s along the coastal and urban areas. Excessive maximum heat
indices are expected to be reached for much of the islands and
consequently a Heat Advisory will be in effect for all coastal and
urban areas of Puerto Rico, Culebra, and the USVI.

Recent satellite imagery and all model guidance suggest a
weakening/filling TUTT and this will be replaced by ridging in the
upper levels. This will lead to more stable conditions and
subsidence aloft. However with the prevailing low level southeast
wind flow along with good daytime heating and lift, expect some
enhanced afternoon shower development across portions of the
interior and west sections of Puerto Rico as well as down wind of
the adjacent islands including the USVI. Isolated thunderstorms with
period of locally heavy rains over some of these areas may lead to
minor urban and small stream flooding as well as ponding of water on
roads and poor drainage areas. Activity however is not expected to
be widespread and should be more localized. On Friday increasing
tropical moisture is still expected with the approach and passage of
from moisture remnants of AL94/tropical wave late Friday into
Saturday. Nonetheless, sufficient tropical moisture moving from the
Caribbean waters, daytime heating and local effects will induce
shower activity and isolated thunderstorms along the Cordillera
Central and western Puerto Rico each afternoon. The latest
Precipitable Water Content Analysis (PWAT) continue above-normal
moisture with values between 2.0 to 2.2 inches through Friday. Winds
will prevail from the east southeast today, then becoming more
southeasterly on Friday and Saturday.

The National Hurricane Center is currently watching a weak area of
low pressure/tropical wave (Invest 94L) with a low formation chance
of 10% within the next 48 hours and 7 days. This wave may reach the
local forecast area late Friday and Saturday increasing the
potential of strong showers and thunderstorm development across the
region. Residents and visitors should continue to monitor the
progress of this system as it moves towards the northeastern
Caribbean. Please refer to the latest Tropical Weather Outlook
(TWOAT) issued by National Hurricane Center for updated information.

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

A variable weather pattern is expected to persist over the long
term. A broad mid-to-upper-level ridge will enhance subsidence,
drier conditions aloft, and more stable atmospheric conditions.
While this will suppress significant convective development, a
deep layer of tropical moisture will remain in place, supported by
a southeasterly wind flow generated by a surface high-pressure
system over the central Atlantic. Global model guidance indicates
precipitable water values exceeding 2 inches associated with
Invest 92L, particularly from Sunday into early Monday. Despite
the overall stability of the aloft, this tropical moisture, the
local and diurnal effects will support localized convection,
especially for the interior and northwestern sections, including
the San Juan Metro area. Therefore, the forecast calls for a wet
pattern on Sunday, with widespread afternoon activity and isolated
to scattered thunderstorms, as The Galvez-Davison Index (GDI)
suggests. Given the already saturated soils and additional
rainfall, urban and small-stream flooding is likely in vulnerable
areas.

By Monday, a slightly drier air mass will begin to filter in as
the moisture associated with the disturbance shifts northwestward
and the surface ridge migrates farther into the western Atlantic.
This will lead to a drier and more variable weather pattern
characterized by warmer daytime temperatures. However, sufficient
diurnal heating combined with lingering low-level moisture will
continue to support afternoon convection, particularly across the
interior, where local convergence and the diurnal heating could
enhance shower activity.

&&

.AVIATION...
VFR conditions to prevail across the forecast area durg prd. SCT cld
lyrs nr FL025...FL045...FL090 with Wdly SCT SHRA/-SHRA ovr regional
waters and en route btw islands. VCSH psbl at TJSJ/TJPS/TIST/TISX
til 12/12z. FEW low clds and -SHRA maY cause brief Mtn Top obscr ovr
E interior of PR til 12/12z. SFC wnd will be clam to light and
variable bcmg fm the ESE btw 10-15 kts, with sea breeze variations
and ocnly hir gusts aft 12/14Z.

&&

.MARINE...
A surface high pressure over the northeastern Atlantic will hold
for the upcoming days, promoting gentle to moderate easterly winds
across the local waters. Seas should remain under 5 feet. However,
localized hazardous marine conditions are expected due to plenty
of tropical moisture across the CWA, leading to showers and thunderstorms.
Plenty of tropical moisture from the tropical wave Invest 92L
will bring active weather from late Friday into Sunday.


&&

.BEACH FORECAST...
A moderate risk of rip currents will continue for the northern
beaches of Puerto Rico through at least tomorrow. There is a
moderate risk of rip currents for eastern Puerto Rico, Culebra,
and St. Croix, as well. Low risk elsewhere. Isolated thunderstorms
with occasional lightning strikes are expected today across most
coastal areas of the islands.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
421 AM AST Fri Sep 13 2024

.SYNOPSIS...

A more unsettled weather pattern is expected today and into the
upcoming weekend with the arrival of the tropical disturbance
Invest 94L, which the National Hurricane Center is monitoring,
giving it a 20% chance of tropical development in the next two
days. As a result, the islands will experience periods of heavy
rainfall and thunderstorm activity. Although widespread shower
activity is forecast, southeasterly winds will enhance heat
indices, potentially reaching Heat Advisory criteria for most
coastal areas today. Therefore, a Heat Advisory is in effect from
10 AM to 5 PM.For more specific information please refeer to
weather.gov/sju.

&&

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

Partly cloudy to variably cloudy skies continued across much of the
region overnight except for western Puerto Rico and the Mona passage
where skies were mostly clear. Passing showers and isolated
thunderstorms were noted over the coastal waters especially between
eastern Puerto rico and the U.S. Virgin Islands. Some of this
activity reached the coastal areas of Puerto Rico and the U.S.
Virgin islands at times. Rainfall accumulations so far were between
a tenth of an inch to half an inch with the heaviest rains. Expect
these conditions to persist into the early morning hours. Thereafter
a gradual clearing and sunny skies can be expected before locally
and diurnally induced showers begin to develop once again across
parts of the interior and west to northwest sections of Puerto Rico
and downwind of the U.S. Virgin Islands during the afternoon hours.
With the dominant southeasterly low level wind flow today, expect
hot and humid conditions with high temperatures in the upper 80s to
low 90s along the coastal and urban areas. Excessive maximum heat
indices are expected to be reached for much of Puerto Rico, Culebra
and the U.S. Virgin islands. A Heat Advisory will therefore be
likely for much of the coastal and urban areas.

Recent model guidance and latest satellite imagery, all suggest a
building mid to upper level ridge across the northeast Caribbean
while the TUTT continued to weaken and shift west northwest of the
region inducing a fairly light south southeast upper level wind
flow. In the low levels, the broad Atlantic high pressure ridge
extending southwards to just northeast of the region and the low
pressure trough (remnants from AL94) now located just east of the
northern Leeward Islands will maintain a light to moderate southeast
wind flow across the region today and through the weekend. This
along with another day of good daytime heating and local effects
will enhanced afternoon and early evening convection especially
across portions of the interior and west sections of Puerto Rico as
well as areas downwind of the USVI. Periods of locally heavy rains
accompanying the enhanced afternoon shower and isolated
thunderstorms may lead to minor urban and small stream flooding as
well as ponding of water on roads and poor drainage areas.

During the rest of this afternoon and through Saturday, increasing
tropical moisture is forecast with the approach and passage of the
aforementioned trough (AL94) and a tropical wave. As a result there
will be increased potencial for shower and isolated thunderstorms
development with brief gusty winds through Saturday across the
coastal waters and over portions of the local islands. The abundant
moisture pooling and daytime heating along with local effects will
promote shower development with isolated to scattered thunderstorms
along the Cordillera Central and western Puerto Rico each afternoon
through the period. The latest Precipitable Water products (PWAT)
continued to suggest above-normal moisture values between 2.0 to 2.4
inches through Saturday and into early Sunday before diminishing the
less than 2.0 inches by late Sunday afternoon. Winds will prevail
from the southeast through the period with hot and humid conditions
forecast to persist along with above normal high temperatures
especially along the north coastal areas of Puerto Rico through the
upcoming weekend. These conditions will lead to elevated risk of
excessive heat conditions during the period for most of the coastal
and urban areas.

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

Ridging aloft will dominate most of the upcoming workweek,
resulting in drier air at upper levels and limited instability
across the region. At the surface, the prevailing feature is a
building surface high pressure over the central Atlantic,
interacting with the now Tropical Depression #7, which will be
positioned about a thousand miles east of the region, moving
northeastward with no direct impact on the islands. Under this
surface pattern, the islands should expect variable weather
conditions, with drier air, some Saharan Dust particles, and
shallow moisture pockets from time to time across the region.

By late Tuesday into Wednesday, model guidance suggests a
weakening of the surface ridge in response to a low-pressure
system over the western Atlantic, leading to backing winds across
the islands. As winds shift more from the east, tropical moisture
located just north of the CWA will settle over the islands,
increasing the water content and resulting in more frequent early
morning showers across the northern local waters, streaming into
the north-central sections.

From Wednesday onward, an upper low-pressure, reflected across
all the levels, will result in a surface convergence zone,
weakening the surface pressure gradient and leading to light to
gentle variable winds until late Thursday. Trapped moisture at
around 700 mb, combined with local effects, will enhance afternoon
convection each day. Since winds will be light, shower activity
typically associated with the sea breeze is not anticipated.
However, diurnal processes and the local effects will be
sufficient to produce slow-moving showers, leading to periods of
elevated flood threat across the interior sections.

&&

.AVIATION...
(06Z)
VFR conds at all terminals thru fcst prd. SCT SHRA/Isold TSRA will
affect the regional waters and areas en route btw PR and the USVI
terminals til 13/12Z. SCT ocnl BKN lyrs nr FL025...FL050...FL090,
with VCSH psbl at TJSJ/TJNR and VCTS at USVI terminals til 13/12Z.
Mtn top obscr ovr E interior of PR due to low clds/-SHRA. SFC wnds
calm to lgt/vrb, bcmg fm ESE 10-15 knots with sea breeze variations
and ocnly hir gusts aft 13/14Z. L/LVL wnds veering fm SE-SSE 5-15
kts blo FL150.

&&

.MARINE...
A surface high-pressure systemover the northeastern Atlantic will
dominate in the upcoming days, promoting gentle to moderate
easterly winds across the local waters. Seas are expected to
remain below 5 feet. However, localized hazardous marine
conditions are anticipated due to the presence of abundant
tropical moisture across the local waters, which will lead to
showers and thunderstorms. The Tropical wave Invest 94L will
increase tropical moisture today through Sunday, contributing to
unsettled weather conditions. Additionally, model guidance
indicates a weak pulse of swell generated by Tropical Depression 7
as it strengthens, expected to impact the region by midweek of
the upcoming week.


&&

.BEACH FORECAST...
Today, all the exposed local beaches of Puerto Rico and the U.S.
Virgin Islands are at low risk of rip currents, which will persist
until Monday. The Invest 94L will enhance thunderstorm activity,
resulting in localized lightning threats for the north and west
coastal areas until Sunday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
514 AM AST Sun Sep 15 2024

.SYNOPSIS...
A tropical wave with axis now crossing Puerto Rico will exit the
area later today. Showers and isolated thunderstorms will persist
across the coastal waters and local passages with some affecting
the south and east coastal areas of Puerto Rico during the rest
of the early morning. A drier airmass will move in from the east
and spread across the region by this afternoon. This should then
limit most of the afternoon convection to portions of central and
west to northwest Puerto Rico where localized active weather and
periods of heavy rains may be experienced. Hot and humid conditions
will continue into early next week with an elevated to significant
heat risk possible across portions of the islands. The prevailing
southeasterly winds will become more easterly by Monday as a surface
high pressure ridge will build north of the region.

&&

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

Clusters of strong showers developed across southeastern sections of
Puerto Rico, resulting in periods of heavy rain early this morning
over Ponce and Peñuelas. Another band of showers affected the
eastern portions of the island; however, Doppler radar did not
indicate significant rainfall accumulations in that region.
Overnight temperatures were slightly warmer than usual due to the
prevailing southeasterly wind flow, with minimum temperatures in the
low 80s across coastal areas, while cooler conditions were observed
in the higher elevations.

For the remainder of the period, ridging aloft will promote more
stable weather, characterized by drier air aloft and warmer mid-
level temperatures. A broad surface high pressure system will
continue to dominate the area, sustaining the southeasterly wind
flow over the islands. Satellite-derived GOES imagery indicates a
decent amount of tropical moisture with precipitable water (PWAT)
values near 2.0 inches for this morning and early afternoon.
Therefore, isolated to scattered showers are forecast, mainly
affecting the eastern sections of Puerto Rico.

By this afternoon and continuing into Monday, a drying trend is
expected as the southeasterly winds provided by the surface ridge
bring in a mass of air containing Saharan dust particles, as
suggested by the NASA Goddard Earth Observing System Model V5.
According to global model guidance, PWAT values will drop two
standard deviations below climatological normals, leading to stable
conditions with minimal instability. This will result in clear skies
and increased solar radiation, contributing to warmer days with
elevated heat indices, particularly across coastal and urban areas.
Forecast 925 mb temperature trends suggest a warming pattern through
at least Tuesday. Although Tuesday will remain warm, pockets of
shallow moisture will increase cloudiness, potentially triggering
afternoon convection and isolated showers.

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

An overall dry and stable weather pattern is forecast at least
through Wednesday with winds becoming more easterly and gradually
diminish. A slight increase in trade wind moisture is forecast by
Thursday and rest of the workweek as winds become more east
northeast and bands of shallow moisture is brought in across the
area from the central and northeast Atlantic. Thereafter the local
winds become light and variable with a northeasterly component as
the surface high pressure ridge relaxes north of the region. Recent
guidance continue to suggest a retrograding Tutt will deepen and
sinks southwards between Puerto Rico and the northern Leeward
islands by Friday into the weekend. This in turn will destabilize
the upper levels and favor better chance for early morning and
afternoon convection across the region over the weekend. Activity
however should be more localized and not widespread. However, good
daytime heating and local effects will support enhanced afternoon
convection in some areas across portions of central interior and
west sections of Puerto Rico each afternoon. Lesser activity is so
far forecast around the U.S.Virgin islands where mostly isolated
showers will be possible for the most part.

The prevailing surface features will be a building surface high
pressure over the west and southwest Atlantic, interacting with
what is now Tropical Storm Gordon. This is still forecast to move
well northeast of the region over the Central Atlantic and have
no direct impacts on the islands. Under this expected pattern, a
mix of sunshine and clouds and variable weather conditions are
forecast, with an overall drier airmass to remain in place, along
with some traces of suspended dust particulates. The occasional
passage of bands and shallow pockets of moisture from time to time
can be expected across the region. This will be sufficient to aid
in the development of nocturnal and diurnal convection each day.
This scenario along with the intense daytime heating will lead to
periods of enhanced afternoon convection in isolated areas especially
across portions of Puerto Rico each day.

For the most part, the winds are expected to be fairly light and
therefore any locally and diurnally induced afternoon activity will
will be sufficient to produce slow-moving showers and thunderstorm
with locally heavy rains. This may lead to periods of elevated flood
threat especially across the central and west to southwest sections
of Puerto Rico.

&&

.AVIATION...
(06Z)
VFR conditions will persist with vicinity showers (VCSH) expected
near TJSJ and TIST until 15/14Z. Winds will increase around
15/15Z, shifting more from the southeast (SE) with gusty
conditions and sea breeze variations. Thunderstorms (TSRA) and
showers (SHRA) are forecast across northwestern Puerto Rico,
particularly near TJBQ, which will result in lower ceilings and
reduced visibility (VIS) due to convective activity.

&&

.MARINE...
A weak surface high pressure pattern will remain in place across the
western Atlantic, while a tropical wave crosses the regional waters
today. This pattern will promote gentle to moderate southeasterly
winds with occasional passing showers and isolated thunderstorms with
brief gusty winds over the coastal waters and local passages. Overall
seas will range between 2 to 4 feet occasionally up to 5 feet over
the offshore Atlantic waters and passages and between 1 to 3 feet
elsewhere.

&&

.BEACH FORECAST...
Beachgoers can expect a low risk of rip currents along most of the
local beaches of the USVI and PR. Winds along the coastal areas will
be between 10 to 15 mph with sea breeze variations and occasionally
higher gusts during the afternoon hours.

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Tue Sep 17 2024

.SYNOPSIS...

A dry air mass continues to dominate the region and will allow
mostly stable conditions today. Hot conditions will prevail; an
Excessive Heat Warning has been issued for the urban and low-
elevation areas of northern and western Puerto Rico, as well as
for St. Croix. For the rest of the coastal areas, including
Vieques, Culebra, St. Thomas, and St. John, a Heat Advisory is in
effect, both from 10 AM to 5 PM AST. Easterly winds will dominate
from today through tomorrow, then winds will become light and more
variable in the latter half of the week. An upper level trough is
expected to bring favorable conditions for the development of
showers and isolated thunderstorms by the end of the week.

&&

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

A line of showers developed along the coast of northeast Puerto
Rico, reaching portions of the San Juan metro area during the
overnight hours. Other than that, only a few showers were observed
in the offshore Atlantic and Caribbean waters.

The islands are still covered by a pocket of dry air today, as is
evident in satellite imagery. There is a patch of moisture just to
the northeast of the region, but the moisture should stay away for
today. A surface to upper level ridge continues to linger today,
with a trade wind cap inversion around 850 mb. Above these levels,
the air mass is dry, and the available moisture is trapped closer to
the surface. In fact, the dewpoint depression for today is around 20
degree Celsius, an indicative of dry conditions. Rainfall activity
should be very limited, but showers should manage to form over
western Puerto Rico in the afternoon. This activity will be short-
lived, and accumulations are not expected to be too significant.

The main story for today, again, is the scorching heat across the
U.S. Caribbean territories. Temperatures at the 925 mb are above
normal, and with lows only dropping to the low 80s, and lots of
sunshine, it will feet very hot during noon and in the afternoon
hours.

On Wednesday, a small area of moisture will cross the islands from
north to south. Most of the activity should arrive in the overnight
or in the early morning hours, but the increase in moisture should
lead to stronger and more widespread showers over the interior and
western Puerto Rico in the afternoon. Isolated to scattered showers
are also expected to reach the Virgin Islands and eastern Puerto
Rico during this period.

On Thursday, the surface high weakens, and so will the winds. In
fact, the low level steering flow is expected to be from the east at
5 knots or less. Moisture levels are not going to be too high, but
with enough heating, showers are again expected for the interior and
west, drifting toward the south and southwestern Puerto Rico.

&&

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

Recent model guidance indicates that an upper-level trough will
deepen and move southward between Puerto Rico and the northern
Leeward Islands by Friday. This will help destabilize the upper
levels and increase the likelihood of early morning and afternoon
convection across the interior and western sectors of Puerto Rico.
Additionally, the latest satellite-derived precipitable water
values show an increase from mostly below normal to normal levels.
Therefore, while there won’t be enough moisture for widespread
rain, there will be enough to develop showers. Throughout this
period, winds are expected to remain very light and somewhat
variable. As a result, urban and small stream flooding may occur
due to locally and diurnally induced slow-moving showers and
thunderstorms with locally heavy rainfall, especially in the
central and western sections of Puerto Rico.

By the weekend, surface winds are expected to shift to a more south-
southeasterly direction and remain very light. The latest models
suggest that the area of convergence associated with the upper-
level trough will be over the region, which may help to limit rain
chances. However, daytime heating and local effects will continue
to enhance afternoon convection in some areas, particularly in
the interior, northwestern, and north-central Puerto Rico. In
contrast, the U.S. Virgin Islands is expected to experience mostly
isolated showers.

Hot conditions are likely to persist throughout this period, with
temperatures potentially reaching the upper 90s and heat indices
remaining elevated. Temperatures at 925 mb will remain well above
normal through the weekend. The combination of high temperatures
and moisture could create hazardous heat conditions, particularly
in urban and low-elevation areas. Therefore, it is very likely
that Heat Advisories and possibly Excessive Heat Warnings will be
issued daily for some areas. Residents and visitors should take
precautions to stay hydrated by drinking plenty of water, wearing
light and breathable clothing, and avoiding prolonged sun
exposure, especially during peak heat hours.

&&

.AVIATION...
(06Z TAFs)

Mainly VFR conditions expected to prevail through the forecast
period. Isolated SHRA will be possible in the vicinity of USVI and
TJSJ, but without significant impacts to operations. Winds will be
from the E at 12-16 kts, with stronger gusts.

&&

.MARINE...

A weak surface high-pressure system will promote gentle to moderate
easterly winds. By midweek, the winds are expected to become lighter
and more northeasterly. Today, very isolated showers are anticipated
over the local waters as drier air continues to settle in. A few
thunderstorms are possible off the western coast of Puerto Rico each
afternoon. Overall, seas will range from 3 to 5 feet, occasionally
reaching up to 6 feet across most local waters, with seas between 1
to 3 feet across most coastal waters over the next few days.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Wed Sep 18 2024

.SYNOPSIS...

The combination of moisture and local effects will result in
showers along the interior, east and west sectors of Puerto Rico,
as well across the U.S. Virgin Islands. A typical shower pattern
is expected over the next few days, heightened by the end of the
week due to increased instability and available moisture. Northeast
winds will help keep temperatures somewhat cooler today resulting
in a limited heat risk, but excessive heat levels in the coming
days will pose a risk to vulnerable individuals, especially those
outdoors without proper cooling or hydration.

&&

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

The most recent satellite-derived precipitable water imagery show a
patch of moisture approaching from the north. This has resulted in
showers and isolated thunderstorms brushing the northern coast of
Puerto Rico, Saint Thomas, Saint John, and Saint Croix.

A surface high pressure north of the Caribbean and a low pressure
system well northeast of the islands will maintain a northeast wind
flow today at around 10 knots. There is another trough leaving the
eastern coast of the United States that will work to weaken the wind
flow for the rest of the week, with speeds around 3-6 knots on
Thursday and Friday. Today, the patch of moisture will combine with
local effects to generate showers along the interior, east and west
of Puerto Rico, and over the Virgin Islands. This activity is
expected to taper off in the evening hours as a small area of dry
air filters in from the northeast.

Similar conditions are expected to repeat on Thursday, with another
patch of moisture reaching from the northeast. Thus, shower activity
will increase again in the night hours over the northern coast of
Puerto Rico and the Virgin Islands. The main difference will be that
with lighter winds anticipated, the afternoon activity could linger
longer over the Cordillera Central, then spreading toward the
coastal areas in the afternoon hours. Some minor urban flooding and
water surges along rivers can be anticipated.

On Friday, moisture lingers, but under light winds coming from the
south-southeast. Under this flow, temperatures will warm up once
again, with 925 mb values over two standard deviation above
climatology. Excessive heat conditions will be likely.

&&

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

Latest satellite-derived precipitable water values indicate a
patch of drier air moving into the area around next Saturday, with
PWAT values expected to range from 1.4 to 1.6 inches. Heights will
begin to increase as the axis of an upper-level trough moves away,
leaving the subsiding portion over our region, which will help
limit rain development a little. While there won’t be enough
moisture for widespread rainfall, local effects and diurnal
heating will still promote afternoon convection in some areas,
particularly in the interior, northwestern, and north-central
Puerto Rico. In contrast, the U.S. Virgin Islands are expected to
experience mostly isolated showers. Similar conditions are
anticipated to persist into Sunday.

By Monday and Tuesday, moisture will increase from the south,
resulting in better rain chances across the islands. During this
period, winds are expected to remain very light and somewhat
variable. As a result, urban and small stream flooding may occur
due to locally induced slow-moving showers and thunderstorms with
heavy rainfall, especially in the central and western sections of
Puerto Rico.

Hot conditions will likely dominate over the long-term period,
with potentially heat indices remaining elevated. Over the
weekend, guidance are suggesting that temperatures at 925 mb will
remain two standard deviations above normal. The combination of
high temperatures and humidity could create hazardous heat
conditions, particularly in urban and low-elevation areas of the
islands. Therefore, it is likely that Heat Advisories and Excessive
Heat Warnings will be issued. Residents and visitors are encouraged
to monitor the forecast, take precautions to stay hydrated by
drinking plenty of water, wearing light and breathable clothing,
and avoiding prolonged sun exposure, especially during peak heat
hours.

&&

.AVIATION...
(06Z TAFs)

Passing SHRA across TJSJ and the USVI terminals is expected to
continue through the forecast period, with brief periods of reduced
VIS and low ceilings. After 17Z, additional activity is expected to
develop in the Cordillera Central, causing mountain obscuration and
likely reaching TJPS. Winds will be from the ENE at 10-12 kts, with
stronger gusts from 14-22Z. Winds will slow down after 22z, out of
the ENE at 9 kts or less.

&&

.MARINE...

East-northeast winds will dominate, gradually becoming variable
and weakening from Thursday throughout the weekend. Showers are
expected to persist over the local Atlantic waters and Caribbean
passages this morning, with a chance of isolated thunderstorms off
the western coast of Puerto Rico each afternoon. Overall, seas
will range from 3 to 4 feet, occasionally reaching up to 6 feet in
some areas, while southern coastal regions will experience lower
seas in the coming days.

&&

.BEACH FORECAST...

Today, the risk of rip currents will remain moderate along the
northern beaches of Puerto Rico, while elsewhere it will be low.
Over the coming days, a moderate risk will persist along the
northern-facing beaches of Puerto Rico, with a return to moderate
risk for the rest of the islands by the end of the week into the
weekend. For a more detailed forecast, please consult the Surf
Zone Forecast for Puerto Rico and the U.S. Virgin Islands
(SRFSJU).

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
350 AM AST Thu Sep 19 2024

.SYNOPSIS...
Winds will weaken over the islands in the upcoming days,
with slow moving showers and thunderstorms developing each
afternoon. The risk for flooding will be elevated almost each
afternoon. Hot temperatures are also expected to persist across
the islands.

&&

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

Currently, radar and satellite imagery show calm, fair-weather
conditions across the islands, with light and variable winds.
Isolated showers across the local waters. Temperatures in coastal
and lower-elevation areas of Puerto Rico range from the upper 70s to
lower 80s, while higher elevations experience cooler temperatures in
the mid to upper 60s. In the U.S. Virgin Islands, temperatures are
currently in the upper 70s to lower 80s.

Today, a patch of moisture moving in from the northeast will rapidly
increase precipitable water values (PWAT) to above-normal levels,
reaching between 2.0 and 2.2 inches. Winds at the surface will have
a northeasterly component while becoming lighter, around 3 to 6
knots. This moisture will combine with local effects to generate
showers across the islands this afternoon. As a result, minor urban
and small stream flooding may occur due to locally and diurnally
induced slow-moving showers with heavy rainfall and thunderstorms,
especially across the Cordillera Central and western sections of
Puerto Rico. Similar conditions are expected to prevail on Friday.

Latest satellite-derived precipitable water values indicate a patch
of drier air moving into the area around next Saturday, with PWAT
values expected to range from 1.4 to 1.7 inches. Heights will begin
to increase as the axis of an upper-level trough moves away, leaving
a subsiding portion over our region. However, local effects and
diurnal heating will still promote afternoon convection in some
areas, particularly in the interior, northwestern, and north-central
Puerto Rico. The U.S. Virgin Islands are expected to experience
mostly isolated showers.

Northeast winds will help keep temperatures somewhat cooler today,
but warm to hot conditions will likely continue in the coming days,
with heat indices remaining elevated. Guidance shows temperatures at
925 mb two standard deviations above normal. Residents and visitors
should take precautions to stay hydrated by drinking plenty of
water, wearing light and breathable clothing, and avoiding prolonged
sun exposure, especially during peak heat hours.

As a summary, the increase in moisture and favorable conditions
aloft will lead to more showers and isolated thunderstorms today and
Friday, with a broader area likely experiencing limited to elevated
flooding and lightning risks. Better conditions are anticipated on
Saturday, but local effects and diurnal heating will still promote
afternoon convection in some areas. Warm to hot conditions will
likely continue in the coming days.

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

The pressure gradient will remain weaken late on the weekend and
early next week, with a low level steering flow coming from the
south-southwest of 1 to 4 knots. These light winds are due to a
series of trough over the western Atlantic. At the surface a small
pocket of moisture is expected to reach the islands. This will
act to fuel afternoon showers and thunderstorms along the
Cordillera Central and then spreading toward the coastal areas of
Puerto Rico. Some of this shower activity, although at a lesser
scale, are also expected for the Virgin Islands.

On Tuesday, the combination of a low pressure system developing
over the western Caribbean, and an upper level trough near the
Bahamas will escort an area of mid to upper level clouds into the
region. Conditions aloft will be favorable for showers and
thunderstorms too, so if enough sunshine filters in, another
active afternoon will be likely for the Cordillera Central, and
with the showers then drifting toward northeastern Puerto Rico and
the San Juan metro area. These showers will later move into the
vicinity of the Virgin Islands.

Late Tuesday and Wednesday, the trade wind will recover, gaining
an easterly component, and at 7 to 11 knots. The unsettle weather
pattern is expected to persist, as an upper level low develops
near the islands. The risk for flooding will be elevated all these
days. Temperatures will be high too, but the excessive risk will
be dependent on how deep and widespread the cloud coverage finally
materialize.

&&

.AVIATION...
(06Z TAFs)

Mainly VFR conditions are expected to prevail through the morning
forecast period, with VCSH likely across TJSJ and U.S. Virgin
Islands TAF sites. After 19/1700Z, additional activity is
anticipated to develop in the Cordillera Central, causing mountain
obscuration and likely affecting TJPS. Winds will be from the NE at
10 knots or less, becoming calm or light/variable after 19/2300Z.

&&

.MARINE...
East-northeast winds will dominate, gradually becoming variable and
weakening throughout the weekend. Showers are expected over the
Atlantic waters today, with a chance of isolated thunderstorms off
the south and west coast today.


&&

.BEACH FORECAST...
Low rip current risk is expected today for most of the local
beaches, but the risk will increase to moderate tonight and will
stay like that until Sunday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
402 AM AST Fri Sep 20 2024

.SYNOPSIS...
Light winds will persist through early next week. With light
winds, the afternoon showers and thunderstorms will linger,
increasing the potential for flooding and river rises, mostly for
the interior of Puerto Rico. The Virgin Islands and the coastal
areas in Puerto Rico will receive showers as well. Hot
temperatures will persist each day.

&&

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

Currently, radar and satellite imagery indicate calm and pleasant
weather across the forecast area, accompanied by light and variable
winds. Throughout the overnight period, some isolated showers have
moved over the local waters. Coastal and lower-elevation areas of
Puerto Rico are experiencing morning temperatures ranging from the
upper 70s to lower 80s, while higher elevations enjoy slightly
cooler conditions in the mid 60s to lower 70s. In the U.S. Virgin
Islands, temperatures are similarly in the upper 70s to lower 80s.

The unstable and wet weather pattern will persist in the short term.
The latest satellite-derived precipitable water values fluctuate
between 1.8 and 2.2 inches today, which is considered normal to
above normal. Conditions aloft will be favorable over the next few
days, maintaining instability for deep convection development, as a
TUTT (Tropical Upper Tropospheric Trough) lingers over the northeast
Caribbean. At the surface, light and variable winds will continue
throughout the short-term forecast.

For today, expect another day of showery activity during the morning
across the U.S. Virgin Islands and the eastern sectors of Puerto
Rico. This will be followed by enhanced shower activity due to
diurnal heating, leading to another round of showers and
thunderstorms, particularly across the Cordillera Central during the
early afternoon, spreading toward the coastal areas later in the
afternoon. Hazards include frequent lightning, gusty winds, and
urban and small stream flooding due to already saturated soils. On
Saturday and Sunday, shower activity is expected to be less intense
compared to today, but local effects and diurnal heating will still
promote afternoon convection, especially in the interior,
northwestern, and north-central Puerto Rico.

In addition, an elevated to significant heat risk will persist
through the weekend. Guidance indicates temperatures at 925 mb will
be two standard deviations above normal values, particularly on
Saturday. The combination of high temperatures and humidity could
create hazardous heat conditions. A Heat Advisory is in effect for
all coastal, urban, and low-elevation areas of Puerto Rico, as well
as for Vieques, Culebra, and the U.S. Virgin Islands. Residents and
visitors should monitor the forecast and take precautions to stay
hydrated by drinking plenty of water, wearing light and breathable
clothing, and avoiding prolonged sun exposure, especially during
peak heat hours.

In summary, moisture and favorable conditions aloft will lead to
additional showers and isolated thunderstorms today, with a broader
area likely experiencing limited to elevated flooding and lightning
risks. Local effects and diurnal heating will continue to promote
afternoon convection in some areas over the weekend. Hot conditions
are likely to persist in the coming days.

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

A deep-layered trough will continue to dig just north of the
Caribbean islands. This through will act to maintain a weak
steering flow, with speeds of 1 to 5 knots on Monday and Tuesday.
The through will gradually moves away by mid-week, with winds
gradually recovering speed, but only to around 10 knots. At the
surface, induced patches of moisture will move from time to time
through the period, although there are no particular day with a
great amount of low level moisture. This moisture will act to
generate some showers reaching the coastal areas of Puerto Rico
and the Virgin Islands each day. However, the strongest activity,
with thunderstorms, is expected each afternoon across the
Cordillera Central, with the activity then drifting toward the
coast. Since the winds will be so weak, it is difficult to
determine which area is going to be more affected, aside than the
interior that should receive the bulk of the activity each day.

As it has been the case in the past couple of weeks, above normal
temperatures will persist in the area, with the threat of
excessive heat each day. This heat will mainly impact those
without effective cooling or adequate hydration.

&&

.AVIATION...
(06Z TAFs)

Mainly VFR conditions are expected to prevail throughout the morning
forecast period, with visibility concerns likely at TJSJ and U.S.
Virgin Islands TAF sites. After 20/1700Z, additional activity is
anticipated to develop in the Cordillera Central, leading to
mountain obscuration that may affect TJPS. Winds will remain light
and variable, shifting to a southerly component at around 5 to 8
knots or less, becoming calm or light/variable after 20/2300Z.

&&

.MARINE...
A weak surface low pressure to the northeast of the region will
maintain weak and variable winds throughout early next week. Showers
and isolated thunderstorms will persist across the regional waters,
particularly off the western and southern coastal waters of Puerto
Rico each afternoon.


&&

.BEACH FORECAST...
The moderate rip current risk will persist for the northern coast
of Puerto Rico, Culebra, and some beaches in northwestern St. John
and eastern St. Croix.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
512 AM AST Sat Sep 21 2024

.SYNOPSIS...

Slightly drier conditions will prevail across the islands today.
A typical pattern of calm nights and mornings, followed by warm-
to- hot afternoons and evenings driven by diurnal heating and weak
steering winds, will prevail for the next few days. Excessive
heat will continue to pose a risk to vulnerable individuals,
particularly those outdoors without proper cooling or hydration.
Additionally, the moderate risk of rip currents will persist over
the next few days.

&&

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

Currently, radar and satellite imagery show some isolated showers
over the local waters. Most clouds and showers have dissipated over
land except for some tops that have blown south from earlier
thunderstorms over the Atlantic waters. Low temperatures this
morning are running from the mid 70s to the lower 80s in the lower
elevations and from the upper 60s to the mid 70s in the mid to upper
elevations. Winds have quieted down to 5 mph or less with many areas
becalmed.

The TPW product shows a drier strip of air crawling very slowly
northward. It has reached Ponce and Saint Croix and will spread
across Saint Thomas and some of Puerto Rico during the day. Lower
level winds are quite light with winds 10 kts or less below 25 kft.
This is due to high pressure over the Canary Islands being blocked
by a pair of low pressures between 25 and 30 north and between 40
and 60 west. Weak high pressure can be seen north of the Mona
Passage and across the local area. At mid levels a broad area of
high pressure extends across the tropical Atlantic. At upper levels
the TUTT low over the area tonight is edging east and will allow a
30 knot jet from the north northwest to push across the area Saturday
through Sunday. Low pressure will bring troughing to our area Monday
night, but its associated low will remain north of 30 north and will
just barely be able to impinge on the high pressure over the west
central Caribbean Sea. Flow at lower levels and specifically the
mean flow between 1000 and 700 mb will be southerly and will bring
the drier air to our south over the area and allow temperatures to
warm more than yesterday. For this reason Excessive Heat Warnings
for most of the lower elevations of Puerto Rico and Saint Croix have
been issued. Heat Advisories have been issued for the remaining
lower elevations including the interior valleys in eastern Puerto
Rico.

All of these warm-to-hot conditions will fade a little on Sunday
when better moisture arrives, and precipitable water values peak
around 7 PM AST each day of the short term period when showers and
thunderstorms grow over interior Puerto Rico. But warm to hot
conditions will persist through the short term and into the long-
term before meaningful relief occurs.

&&

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

The inherited forecast remains on track. According to the latest
model guidance, a deep-layered trough is expected to move just
north of the Caribbean islands until at least late Tuesday into
Wednesday. This weather feature will result in a weak steering
wind flow, with speeds ranging from 1 to 5 knots and gradually
recovering to around 10 knots after its passage. Tuesday is
expected to be a day with variable weather conditions, as the
trough will be closest to the islands allowing the surface
moisture to slightly filter across all levels of the atmosphere.
The 500 mb temperatures are expected to be around -7 to -8 degrees
Fahrenheit on Tuesday, which could lead to an increase in
instability and the potential for thunderstorm development
particularly during the afternoon hours. Despite the passage of
the trough, occasional patches of moisture are anticipated to move
across the forecast area throughout the period, resulting in
showers reaching the coastal areas of Puerto Rico and the Virgin
Islands each day. The strongest shower and thunderstorm activity
is expected each afternoon across the Cordillera Central, with the
activity then drifting toward the coast. Due to weak winds, it is
difficult to determine which area will be more affected, aside
from the interior, which should receive the bulk of the activity
each day. Towards the end of the workweek, a tropical wave will
reach the islands. We anticipate occasional ponding of water on
roads and poorly drained areas from Tuesday into Friday.
Temperature-wise, above-normal temperatures are expected to
persist over the region, with the threat of excessive heat each
day. This heat will mainly impact those without effective cooling,
adequate hydration, or prolonged exposure.

&&

.AVIATION...
(06Z TAFs)

Mainly VFR conditions ovr land. Aft 21/15Z Clds and SHRA to dvlp ovr
interior PR followed by SHRA/TSRA with mtn obscurations and
MVFR/IFR conds over interior and wrn PR aft 21/17Z till arnd 21/21Z.
TAF sites will have only brief unfavorable conds. Winds less than 10
kt with a few hir gusts in mostly sea breezes and nr TSRA till aft
21/22Z. SHRA/TSRA ovr land will dissipate btwn 21/21-23Z. High
density altitudes at TAF sites are expected today due to heat and
humidity.

&&

.MARINE...

A weak surface low pressure to the northeast of the region will
maintain weak and variable winds throughout early next week. Showers
and isolated thunderstorms will persist across the regional waters,
particularly off the western and southern coastal waters of Puerto
Rico each afternoon.

&&

.BEACH FORECAST...

The moderate rip current risk will persist for the northern and
eastern coast of Puerto Rico and Culebra. Elsewhere is low.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
504 AM AST Sun Sep 22 2024

.SYNOPSIS...

Expect the humidity water values to peak by the late afternoon
and early evening each day of the short term period when showers
and thunderstorms grow over interior Puerto Rico. A typical
pattern of calm nights and mornings, followed by warm- to-hot
afternoons and evenings driven by diurnal heating and weak
steering winds, will prevail in the coming days. Excessive heat
will continue to pose a risk to vulnerable individuals,
particularly those outdoors without proper cooling or hydration.
Additionally, the moderate risk of rip currents will persist
tonight.

&&

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

Currently, radar and satellite imagery show scattered showers over
the Atlantic waters and south of the forecast area and isolated
showers over the local Caribbean waters. Isolated thunderstorms
continued to pop off and then dissipate, but tops are not as high as
yesterday and the showers are not reaching the level where their
tops can blow off. Most clouds and showers have dissipated over
land. Low temperatures this morning are running from the mid 70s to
the lower 80s in the lower elevations and from the upper 60s to the
mid 70s in the mid to upper elevations. Winds have quieted down to 6
mph or less with many areas becalmed.

The TPW product showed a drier strip of air over the local Caribbean
waters. It continues to squelch showers over the area including
Ponce and Saint Croix. This strip is no longer making any northward
progress. Also there is a narrow band of much better moisture just
south of the forecast area that is allowing showers and
thunderstorms to fire off from time to time. Some moisture is also
seen over the Atlantic outer waters in the center of our forecast
area. Lower level winds are quite light with winds 10 kts or less
below 28 kft. This is due to high pressure over the Canary Islands
being blocked by a pair of weakening low pressures between 25 and 30
north and between 40 and 60 west. Weak high pressure can be seen
north of the Mona Passage and across the local area. At mid levels a
broad area of high pressure extends across the tropical Atlantic,
the U.S. Virgin Islands, Puerto Rico and over to Hispaniola. At
upper levels the TUTT low is found over and north of the Leeward
Islands and the 30 knot jet from the north northwest continues to
push across the area today and Monday while increasing to 50 knots
over the eastern Caribbean tonight. Low pressure will bring
troughing to our area Monday night, but its associated low will
remain north of 30 north and will just barely be able to impinge on
the high pressure over the west central Caribbean Sea. Flow at lower
levels and specifically the mean flow between 1000 and 700 mb has
been and will continue to be quite variable, which is one reason why
neither the dry band in our local Caribbean waters nor the band of
moisture just south of it have made no further northward progress.
This lack of winds and the continued moisture over the local islands
is part of the reason heat advisories have been issued for all lower
elevation locations. Some relief from the heat is expected in all
but coastal spaces as showers and thunderstorms, fueled by the
continued humidity, redevelop over the area.

All of these warm-to-hot conditions will hold on, and precipitable
fueled by the continued humidity water values peak late afternoon
and early evening each day of the short term period when showers and
thunderstorms grow over interior Puerto Rico. The GFS 1000-850 mb
thickness values are also seen to increase each day until Tuesday
when the highest value for the week reaches 1426 m.

&&

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

For the long term, we anticipate calm and warm weather conditions
with the development of showers and thunderstorm activity,
particularly in the afternoon hours.

On Wednesday, the steering wind flow will gradually recover to around
10-15 knots as the deep-layered trough continues to exit the
region. The latest model guidance suggests that all the available
moisture should remain below 700 mb through at least Thursday,
meaning that patches of moisture will move across the forecast
area from time to time, resulting in showers reaching the coastal
areas of Puerto Rico and the Virgin Islands each day. The
strongest shower and thunderstorm activity is expected each
afternoon across the Cordillera Central, with the activity then
drifting toward the coast. From Friday into the upcoming weekend,
we foresee that a tropical wave will move well south of Puerto
Rico and the U.S. Virgin Islands. However, we anticipate a slight
increase in moisture across the area, which could enhance shower
development. With the proximity of this tropical wave and the
everyday afternoon shower activity, we forecast occasional ponding
of water on roads and poorly drained areas through Saturday.

Temperature-wise, above-normal temperatures are expected to
persist over the region, with the threat of excessive heat each
day. This heat will mainly impact those without effective cooling,
adequate hydration, or prolonged exposure.

&&

.AVIATION...
(06Z TAFs)

Mainly VFR conditions ovr land. Aft 22/15Z clds and SHRA to dvlp ovr
interior PR followed by SHRA/TSRA with mtn obscurations and MVFR/IFR
conds over interior and wrn PR aft 22/17Z till arnd 22/21Z. TAF
sites will have only brief unfavorable conds. Winds less than 10 kt
with a few hir gusts in mostly sea breezes and nr TSRA till aft
22/22Z. SHRA/TSRA ovr land will dissipate btwn 22/21-23Z. High
density altitudes at TAF sites are expected today due to heat and
humidity.

&&

.MARINE...

A surface low pressure to the northeast of the region over the
Central Atlantic will maintain light and variable winds into the
early part of next week. Showers and isolated thunderstorms will
develop from time to time across the regional waters, particularly
off the western and southern coastal waters of Puerto Rico each
afternoon.

&&

.BEACH FORECAST...

The rip current risk will remain low across the islands through at
least Wednesday, when the moderate risk returns for the northern
coastal areas of Puerto Rico.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
518 AM AST Tue Sep 24 2024

.SYNOPSIS...Warm-to-hot conditions will continue today. Winds will
increase a little Wednesday through Friday when a tropical wave
will move through--mostly south of the area. Warm and moist
conditions will continue through the weekend followed by somewhat
drier conditions in the first few days of next week.

&&

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

Tonight, mostly fair weather conditions prevailed inland across
Puerto Rico and the U.S. Virgin Islands. However, some lightning
activity lit the sky, particularly along the northern, western, and
southern coastal areas of Puerto Rico and the U.S. Virgin Islands,
as some showers and isolated to scattered thunderstorms developed
over the Atlantic and Caribbean waters and the waters between the
U.S. Virgin Islands and the Mona Passage. The overnight temperatures
remained in the lower 70s in the higher terrain and in the upper
70s to lower 80s in the urban/coastal areas. Like previous days,
the winds were relatively light and variable across the islands.

The short-term forecast remains unchanged. According to the latest
model guidance, the upper-level trough will continue to move from
the western Atlantic and will position to the north of our forecast
area, enhancing the upward vertical motion and better moisture
content today. Therefore, showers and thunderstorms will increase in
coverage once again, particularly this afternoon. Weak steering
winds will also lead to higher rainfall accumulations over the same
areas, increasing the potential for flooding and mudslides in steep
terrain, mainly along the Cordillera Central. On Wednesday, winds
are expected to become slightly stronger, around 10 to 15 knots, as
the deep-level trough will be out of the area by then. As
mentioned in previous discussions, the U.S. Virgin Islands should
experience a similar weather pattern over the next few days, with
little to no rain. However, showers and thunderstorm development
are forecast over the waters near the USVI.

Temperatures will be in the upper 70s to lower 80s over the
higher terrain, and upper 80s to lower 90s will persist across the
lower elevations of the islands during the morning and early
afternoon hours. Therefore, excessive heat conditions can be
anticipated throughout the short-term period. Advisories and
warnings for heat have been issued again today.

&&

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

A band of moisture will move through early Friday morning followed
by a tropical wave--most of which will pass south of the forecast
area Friday night. Nevertheless some increase in rainfall is
expected, despite the fact that 500 mb temperatures will be warmer
than those of today and Wednesday. Precipitable water will be
found mostly between 1.95 and 2.05 inches even though the good
moisture is mostly supplied by the lower layers. While strong low
pressure systems will be found to the distant northwest, north
northeast and east, the flow across the local area on Thursday
will be easterly at 12 to 18 knots. The tropical wave will pass
through on Friday with oscillations in the flow over the weekend.
Finally on Monday and Tuesday flow at the surface becomes light
southerly. High pressure will again nose in from the east
northeast and conditions will dry out a little. Most days during
the long term period will still see afternoon convection over the
western and interior portions of Puerto Rico. On Monday and
Tuesday the showers and thunderstorms could also draw near to the
Greater San Juan and Bayamon Metropolitan areas.

At mid levels high pressure dominates the synoptic pattern while
in upper levels high pressure will remain to the northwest
although still quite influential in maintaining the dryness of the
mid to upper layers.

&&

.AVIATION...
(06Z TAFs)

Mostly VFR conditions at all TAF sites. Clds and SHRA are
expected to dvlp across the interior sections of PR aft 24/17Z,
followed by SHRA/TSRA with mtn obscurations and MVFR conds over
the interior through 24/22Z. TJSJ and TJBQ will experience brief
MVFR conds, particularly after 18Z. Winds less than 11 kt with a
few higher gusts along the coasts and near TSRA till 24/22Z.
TSRA will still be found offshore aft 24/22Z.

&&

.MARINE...A slight north to northeast swell will move into the
area on Wednesday and strengthen on Friday. Winds will increase
Wednesday through Friday, but gradually subside again on Monday
and Tuesday. Small craft advisories are not expected during the
next 7 to 10 days, but small craft will need to exercise caution
in some areas. Conditions will improve Monday and Tuesday of next
week.

&&

.BEACH FORECAST...We will see one more day where all beaches will
have a low risk of rip currents and then north and northeast
facing beaches will begin to have a moderate risk of rip currents.
Conditions improve again Monday night and Tuesday of next week.