Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
453 AM AST Sun Apr 27 2025

.SYNOPSIS...

An unsettled weather pattern is expected to continue through
midweek. A high rip current risk is in effect for the northern
exposed beaches of Puerto Rico, from Aguadilla to Fajardo and
Culebra through at least late tonight.

&&

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

Radar and satellite imagery showed cloudy skies across the islands
during the overnight period. Some showers moved into eastern
municipalities, with the highest rainfall accumulations reported in
Fajardo, ranging from around 1.0 to 2.0 inches as of 4 AM AST, based
on radar estimates. Numerous showers and thunderstorms persisted
through the night across the Caribbean waters. Surface weather
stations registered light winds, mainly from the east. Overnight
temperatures ranged from the lower 60s in the mountains to the mid-
70s across urban and coastal areas of Puerto Rico and the U.S.
Virgin Islands.

The forecast remains generally on track. A wet and unstable weather
pattern is expected to continue through the forecast period across
Puerto Rico and the U.S. Virgin Islands, bringing periods of heavy
showers and thunderstorms enhanced by the presence of a deep-layer
trough and above-normal moisture. Based on the latest model
guidance, moisture content is expected to peak today between 2.0 and
2.1 inches, which is above climatological levels for this time of
year. Although mid-level clouds may slightly limit convective
development, the available moisture and prevailing instability will
still favor afternoon thunderstorms, especially over interior and
northwestern Puerto Rico, as winds are expected to shift from the
east to southeast during the day. Soils remain saturated from recent
heavy rainfall, so the flood risk will stay elevated, similar to
yesterday, as soils and rivers may respond quickly. Potential
impacts today include lightning, strong winds, heavy rainfall,
landslides, and river flooding. Isolated flash flooding cannot be
ruled out.

In the coming days, the wet pattern is anticipated to continue under
the prevailing influence of the trough. Although moisture content
will slightly decrease, it will remain in the above-normal to
average range maintain the wet pattern, with strongest activity
mainly during the afternoons. Winds will turn more form the east to
north east from Monday night onward shifting the afternoon
concentration of showers and thunderstorms a little more to the
southeast of the main island. Residents and visitors are encouraged
to stay weather-aware and monitor official forecast updates,
especially due to the ongoing flood risk, which remains the primary
hazard.

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

A wet and unstable weather pattern will persist through the early
part of the long-term forecast. A surface high-pressure system over
the western Atlantic and a surface low over the central Atlantic
will induce east-northeast winds across the CWA. These northeast
winds will promote low-level convergence over the region,
particularly on Wednesday and Thursday, when the surface low will be
closest to the northeast. Precipitable water content is expected to
remain between 1.7 and above 1.9 inches. These values exceed the
75th and 90th percentiles of the climatological normal, indicating a
continuation of well-above-normal moisture levels for this time of
year.

In terms of instability, the surface low is being induced by an
upper-level cut-off low. These features will lead to a further drop
in 250 mb height fields, cooler 500 mb temperatures, and steeper
lapse rates, sustaining unstable weather conditions capable of
generating deep convective activity. The likelihood of convection
will be highest during the afternoon hours, as high moisture content
and instability combine with surface heating and local effects.

Soils are expected to remain somewhat saturated by Wednesday due to
rains from previous days, with rivers still experiencing elevated
streamflows. Consequently, the flood risk will remain elevated
through at least Thursday, particularly during the afternoon hours.
Quick river rises, river flooding, and landslides are also possible,
primarily across Puerto Rico. In the U.S. Virgin Islands, minor
flooding with brief periods of excessive runoff is possible each day
of the week. Some ridging aloft will bring somewhat more stable
weather conditions by the end of the workweek into the weekend.
Nevertheless, enough low-level moisture could combine with diurnal
heating and local effects during the afternoon to promote convective
activity in localized areas.


&&

.AVIATION...
(06Z TAFs)

VFR conds across most western TAF sites this morning. -SHRA/VCTS
across TJSJ and likely USVI TAF sites may result in intermittent MVFR
conds and reduced VIS trough the morning hours. SHRA are expected to
develop after 15 to 16Z across the Cordillera Central, spreading
toward the west/northwest. Mtn top obsc likely through 27/23z. Winds
will prevail btwn 5-10 kt with higher gust within t-storms. Mainly
from the ESE with sea breeze variations today, becoming from the E
tonight.

&&

.MARINE...

Light to moderate east to southeast winds will prevail through at
least tonight, backing from the northeast winds early this week. A
deep layer trough will continue to promote an unstable weather
pattern across the local waters. Thus, showers and thunderstorms are
expected to persist, producing localized hazardous marine
conditions. This unstable and wet pattern will prevail through at
least midweek. A long-period northeasterly swell is spreading across
the Atlantic waters. Therefore, small craft should exercise caution.


&&

.BEACH FORECAST...

Nearshore buoy 41053 is already detecting 13-14s pulses of the weak
northerly swell. As a result, a Rip Current Statement continues in
effect for the northern beaches of Puerto Rico, from Aguadilla to
Fajardo, as well as the beaches of Culebra.

For more information, please refer to the latest Coastal Hazard
Message (CFWSJU) and Surf Zone Forecast (SRFSJU).

Residents and visitors in affected regions should heed warnings,
avoid swimming in these waters, and stay informed about updates from
local authorities.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
509 AM AST Mon Apr 28 2025

.SYNOPSIS...

An unsettled weather pattern is expected to continue through at
least Thursday due to a series of troughs and abundant moisture.
The likelihood of urban and small stream flooding due to strong
showers and thunderstorms, as well as mudslides and rapid river
rises, will remain high along with a chance of isolated flash
flooding as well. A high rip current risk remains in effect for
the northern exposed beaches of Puerto Rico, from Aguadilla to
Fajardo and Culebra through this afternoon.

&&

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

Shower and thunderstorm activity that had been impacting the
municipalities of Arecibo and Barceloneta ended close to midnight,
leaving nearly 8 inches of rain in the northeasternmost tip of the
Arecibo municipality, with other areas receiving 4 to 6 inches. The
rest of the night was much calmer compared to the afternoon and
evening hours, with moderate showers occasionally moving over St.
Thomas. Minimum temperatures were mostly in the low to mid-70s
across coastal areas of the islands and in the mid to upper 60s in
the highest mountains and valleys of Puerto Rico.

Current satellite imagery and GLM data show that the most active
part of a deep-layered trough is located north of Puerto Rico, over
the offshore Atlantic waters, where the trough is exhibiting the
strongest low-level convergence and upper-level divergence. GOES-19
Precipitable Water satellite data continues to show well above
normal moisture over the region, particularly upstream of the local
islands. Therefore, during the rest of the morning hours, showers
and isolated thunderstorms are expected over the regional waters,
with some showers occasionally moving over windward coastal areas.

Winds will begin shifting today from southeasterly to easterly, and
then to a more northeasterly direction by Wednesday, as a surface
high pressure over the western Atlantic gradually pushes a frontal
boundary associated with the upper-level trough closer to the CWA.
The combination of above-normal moisture, instability aloft, diurnal
heating, and orographically driven convection will lead to another
active afternoon, with thunderstorms first developing over interior
Puerto Rico. The steering wind flow is expected to remain light
throughout most of the short-term forecast period. As a result, slow-
moving thunderstorms will initially cluster over the Cordillera
Central and may later move toward coastal areas as outflow
boundaries generate new convective cells. A similar weather pattern
is expected on Tuesday.

However, Wednesday appears to be the wettest and most active day, as
the aforementioned trough deepens and develops into a cutoff low,
closing off by the end of the forecast period, particularly by
Wednesday night. Widespread thunderstorm activity may develop, and
if it occurs during the evening and night hours, another round of
heavy showers and thunderstorms could impact the eastern third of
Puerto Rico, including Vieques, Culebra, and the U.S. Virgin
Islands. As a reminder, soils are already saturated, and streamflows
are running well above normal due to heavy rains over the past
several days. Therefore, urban and river flooding is likely to
continue, along with the potential for flash flooding and landslides
in flood-prone areas and steep terrain, respectively. Continue to
monitor the forecast as this unstable weather pattern persists
across the region.

&&

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

The long-term forecast continues on track, with a variable and
unsettled pattern ahead. The interaction between a high surface
pressure in the Western Atlantic and a surface low induced by an
upper-level trough will promote light NE-E winds through the period.
Global model ensembles agree that Thursday will be the wettest
day of the forecast period, suggesting above normal Precipitable
Water (PWAT) values (around 1.75 inches). Colder 500 mb
temperatures (-8 to -9 Celsius) and jet dynamics around 250 mb
with speed near 70 knots will bring ventilation and instability
aloft, supporting deep convection activity. As the mid to upper
level trough migrates eastward, drier air will filter into the
region, inhibiting deep convection activity. Additionally,
temperatures in the 500 mb layer should increase to seasonal
values (around -7 Celsius). Although global model ensembles tend
to a "drier" pattern this weekend, there's still enough low to mid
level moisture available for afternoon convection. With the
expected weather conditions, soils saturated, local effects, and
diurnal heating, the potential of flooding will remain limited to
elevated through this period, with showers during the morning
along windward sections and afternoon convection over interior and
western/southwestern Puerto Rico each day. Rainfall accumulations
will most likely promote ponding of water in roadways and poorly
drained areas, as well as urban and small stream flooding.

With the NE-E wind flow dominating the period, 925 mb temperatures
should remain near below normals.

&&

.AVIATION...

(06Z TAFs)

Expect -RA/VCTS posbl at TJSJ/TISX/TIST through 13z. Areas of SHRA
and SCT TSRA this aftn could produce tempo
MVFR/IFR conds and mtn obsc, particularly ovr TJBQ/TJSJ aft 28/17z.
VCTS/SHRA at TJPS for the most part. Despite this pattern, expect
mostly VFR conditions across all terminals through the forecast
period. E winds reaching speeds of up to 8-12 knots, accompanied by
higher gusts and sea breeze variations aft 28/13z.

&&

.MARINE...

Light to moderate east to southeast winds will prevail today and
tomorrow, turning from the northeast by Tuesday night. A deep layer
trough will continue to promote an unstable weather pattern across
the local waters. Showers and thunderstorms are expected to persist,
producing localized hazardous marine conditions, small craft should
exercise caution.

&&

.BEACH FORECAST...

Latest buoy observations show wave periods between 13 - 14
seconds, suggesting that pulses of the northeasterly swell
continue spreading across the local waters. Therefore, the high
risk of rip currents was extended through this afternoon for the
beaches of northern Puerto Rico, from Aguadilla to Fajardo, and
Culebra. As the swell dissipates across the local waters tonight,
a moderate risk of rip currents will prevail for the next few days
for the beaches in northern Puerto Rico, Culebra, and possibly
St. Thomas and St. John in the U.S. Virgin Islands.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Tue Apr 29 2025

.SYNOPSIS...

The unsettled weather pattern will continue through Thursday due
to a series of troughs and abundant moisture. With saturated
soils and elevated river and stream flows, persistent moderate or
heavy rain will elevate flooding risk, including minor flooding,
flash flooding, river flooding, and landslides in steep terrain.
An improvement of the weather conditions is expected this weekend.

&&

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

Variably cloudy skies prevailed during the night and early morning
hours as showers drifted over land areas from coastal waters of PR
and the USVI. The Doppler radar estimated between a quarter to half
an inch of rain with the heaviest showers along portions of northern
and eastern PR, as well in the northern USVI. Minimum temperatures
were from the mid to upper 60s across the higher elevations of PR to
the mid-70s across coastal areas. The wind was light and variable.

A wet weather pattern will continue through the short-term period as
abundant moisture remains over the region under the influence of
deep layered trough over the western Atlantic that extends into the
northeastern Caribbean. Furthermore, a mid-to upper level cut-off
low is expected to develop northeast of the region by late Wednesday
and linger through Thursday. This will further enhance instability
aloft and trigger stronger thunderstorms with heavy rainfall each
afternoon over PR. For the USVI, this period will also be wettest
one. At the surface, weak steering winds will continue today and the
sea breeze influences will cause showers to drift mainly along the
mountain ranges of PR once again. Urban and small stream flooding,
as well as localized flash flooding, river flooding, and mudslides
in areas of steep terrain are expected.

Winds will acquire a northeasterly component and gradually increase
from tonight onwards as a high pressure builds over the western
Atlantic. This will also push a front or remnants of the frontal
boundary currently near 25N closer to the area by the end of the
forecast period, promoting further pooling of low-level moisture.
Taking into consideration the expected wet pattern and the already
saturated soils, a Flash Flood Watch could be issued for the second
part of the short-term period as the potential for flash flooding
and mudslides continues to increase. Residents and visitors are
urged to stay tuned for the latest forecast updates.

&&

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

Deeper convection activity will be reduced this weekend,
transitioning to a wetter and unstable pattern by the beginning of
the workweek. The induced low mentioned in the last discussion is
still expected to develop in the Central Atlantic, along with a
surface high pressure in the Western Atlantic. Based on the latest
model guidance, the surface high should strengthen and migrate
eastward, pushing the low pressure more to the south, promoting
winds with a southerly component. A transition to a "drier" pattern
is still expected by Saturday due to ridging aloft. However, low
to mid level moisture content will remain high. In terms of
instability, upper- level dynamics with 250 mb wind speeds around
70 knots are still expected, which could bring ventilation aloft.
Although temperatures in the 500 mb layer should increase to
seasonal values, instability will be present. Taking that into
consideration, the conditions will be favorable for deep
convection activity. Overall, light to moderate showers will move
occasionally along windward sections each day. The combination of
above-normal moisture, light 0 - 3 km winds, local effects, and
diurnal heating will enhance afternoon convection each day of the
forecast, mainly over the interior and northern/northwestern
portions of Puerto Rico. Due to saturated soils and elevated river
and stream flows, the potential of flooding will increase,
isolated urban and small stream flooding are likely. Model
guidance is projecting a wetter scenario for Tuesday, with another
mid to high-level trough approaching the Caribbean. At the
moment, there's a medium chance of looking above climatological
normal moisture content, elevating the potential of flooding to
elevated.

If winds with the southerly component prevail, temperatures may
increase to near above climatological normals. However, the risk
of heat should remain low for the rest of the period.

&&

.AVIATION...

(06Z TAFs)

Mainly VFR conditions and VCSH in general expected across all
terminals through the period. However, SHRA/TSRA is expected to
develop over the interior of PR btw 29/16-22z, causing mostly VCTS
across all PR terminals and tempo MVFR conds at TJPS. Weak sea
breezes will dominate btw 29/13-20z, with a NE component becoming
the dominant wind direction aft 29/22z.


&&

.MARINE...

Light to moderate easterly winds will continue today, turning from
the northeast tonight. A deep layer trough will continue to promote
an unstable weather pattern across the local waters. Showers and
thunderstorms are expected to persist, producing localized hazardous
marine conditions, small craft should exercise caution.

&&

.BEACH FORECAST...

Latest buoy observations show pulses of a fading long-period
northeasterly swell, but wave heights remain between 2 - 3 feet.
No significant marine events are expected for the next few days.
Therefore, the risk of rip current will remain moderate for the
beaches in northern Puerto Rico, Culebra, and possibly St. Thomas
and St. John in the U.S. Virgin Islands by the end of the
workweek.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
501 AM AST Wed Apr 30 2025

.SYNOPSIS...

The wet and unstable weather pattern will continue through at least
Thursday evening due to a series of troughs and abundant moisture.
Soil saturation and soaring rivers will promote an elevated to
significant flooding threat, including minor flooding, flash
flooding, river flooding, and landslides in steep terrain. Although
an improvement of weather conditions is anticipated by this
weekend, abundant moisture will trigger showers and thunderstorms
in the afternoon.

&&

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

Showers will continue to increase this morning across the U.S.
Virgin Islands and eastern Puerto Rico through the rest of the
morning hours. Ponding of water on roads and in poor drainage areas
is expected with this shower activity. Some showers could grow into
thunderstorms before noon across the mountain ranges of PR and last
through the evening hours. Due to already saturated soils and above
normal streamflows from previous days heavy rainfall, quick river
rises, mudslides, and flash flooding is likely with these
thunderstorms.

The wet weather pattern will continue through the rest of the short-
term period as abundant moisture content(PWAT above 2.00 inches)
lingers over the region. Later today, a cut off low is expected to
develop just northeast of the Leeward Islands from a mid-to upper
level trough over the central Atlantic. Global guidance suggest that
another but weak low reflected at the mid-levels will develop near
Cuba and Hispaniola on Thursday. These features will further enhance
instability across the northeastern Caribbean with colder than
normal 500 mb temperatures around -9C, and as they slowly drift
eastward a 75-80 kt jet segment will meander over the islands
through Friday. Therefore, thunderstorms over the next few days
could produce frequent lightning, small hail, and strong gusty winds
as well as further supporting long lasting rainfall activity over
the islands. Residents and visitors are urge to monitor the weather
conditions and remain vigilant to take necessary action to protect
life and property from the expected flooding impacts.

For more information please refer to the latest updates from the
Hydrologic Outlook(ESFSJU).

https://forecast.weather.gov/wwamap/wwa ... wa=SJU&wwa
=hydrologic%20outlook

&&

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

The long-term forecast suffered some changes. Winds on Saturday
will remain from the northeast, and will shift from the southeast
due to a surface high pressure building in the Western Atlantic
and the induced low in the Central Atlantic moving southward. The
latest model ensemble members are shifting to a wetter scenario
this weekend, with PWAT values above climatological normal (1.8 -
2.0 inches). The 500 mb temperatures should remain colder (-7 to
-8 Celsius), and the latest model guidance keeps suggesting that
the upper dynamics will remain stronger with winds in the 250 mb
layer around 70 knots, providing ventilation aloft. Additionally,
the Galvez-Davison Index (GDI) also displays the potential of
isolated thunderstorms mainly in the afternoons. Although model
guidance keeps suggesting drier air filtering in the upper levels
due to ridging, above-normal low to mid-level moisture content in
the region will trigger shower and thunderstorm activity in the
afternoons along interior Puerto Rico, moving into northern/western
Puerto Rico in the early evenings. Due to the heavy rainfall,
saturated soils, and soaring rivers, the risk of flooding will
remain limited, with mostly ponding of water in roadways, urban,
and poorly drained areas, along urban and small stream flooding.

Another mid to upper-level trough should move north of the
Caribbean, and induce a surface low. The interaction of this low and
a surface high pressure in the Central Atlantic could promote
southerly winds throughout the period. With this pattern, winds
may pool well above-normal moisture content into the region by
late Tuesday, with PWAT values around 2.0 - 2.2 inches for the
rest of the forecast period. The best moisture content might stay
in the east side of the CWA, impacting eastern sections of Puerto
Rico, Vieques, Culebra, and the U.S. Virgin Islands. However,
deeper afternoon convection should develop over interior Puerto
Rico, elevating once again the flooding potential.

With the southerly component in the winds and abundant moisture,
is likely to observe near above-normal temperatures during this
period. However, the heat risk will remain low for the rest of the
forecast period.

&&

.AVIATION...

(06Z TAFs)

Mainly VFR early in the fcst period. However, SHRA increasing from
the Atlantic and eastern waters of the islands will move at times
across the USVI/Eastern PR terminals thru the morning hours. This
can lead to brief MVFR cigs. SHRA/TSRA will develop btw 30/15z-23z
over the mountains and drift mainly southward under 8-14 kt ENE
winds. Therefore, expect mtn tops obscd across PR and tempo MVFR to
IFR conds mainly at TJPS. Elsewhere, -RA/VCTS expected thru the
evening hours.

&&

.MARINE...

A surface high pressure building in the Western Atlantic and a
deep layered trough will promote light to moderate east- northeast
to northeast winds for the next few days. Showers and thunderstorms
are expected to develop across the local waters, producing locally
higher winds and seas. Small craft should exercise caution and stay
weather alert.

&&

.BEACH FORECAST...

No significant swell events is anticipated for the next few days.
However, the moderate risk of rip currents will continue for the
beaches in northern Puerto Rico, and possibly for Culebra and the
northern USVI by tomorrow into the weekend.