Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
522 AM AST Sat Aug 9 2025

.KEY MESSAGES...

* An induced surface trough will likely bring showers across
eastern Puerto Rico and US Virgin Islands this morning, then
moderate to heavy showers with isolated thunderstorms across the
interior and western Puerto Rico by the afternoon.

* The US Virgin Islands will have daily showers and warm to hot
heat indices from mid-morning to afternoon each day.

* The warm-to-hot spell trend will persist throughout most of the
forecast period, especially during the peak of daily heating.

* Tropical moisture is expected to result in showers early next
week, followed by a Saharan Air Layer (SAL) expected to arrive
by Tuesday afternoon.

* The National Hurricane Center (NHC) is monitoring a tropical
wave with 30% chance of formation over the next seven days.
Residents and visitors are encouraged to stay well informed.

&&

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

A surface induced trough increased the frequency of passing showers
the islands during the overnight hours. Since midnight, radar
estimated accumulations over land indicate that northern and eastern
PR, Culebra, Vieques and the U.S. Virgin Islands were affected by
these showers. By 425 AM, St. John saw the highest, radar estimated
since midnight, accumulations of the USVI with around 0.22 in.
Canovanas saw the highest, radar estimated since midnight,
accumulations of PR with around 0.58 in. Accumulations of up to
around 0.9 inches fell over the waters just north of Toa Baja and
Dorado. Current satellite derived precipitable water (PWAT) values
indicate slightly below normal to normal moisture (around 1.70 to
1.75 in) over northeastern Puerto Rico, Culebra, St. Thomas and St.
John. ENE steering flow is forecast to gradually veer to become more
E to ESE today, and continue being ESE during the rest of the period.

Although PWAT values over 2 inches will be present during afternoon
convection, notable advective patches of moistures (with PWAT values
around 1.85 in) are forecast to arrive by tonight into early
tomorrow and on Monday. This moisture arriving on Monday can also
reach over 2 inches of PWAT. This is trailing moisture from Invest
96L, located over the central Atlantic. Although the system itself
will likely move well northeast of the islands, trailing moisture
associated with this system will reach the islands on Monday, with
the highest amounts arriving late Monday into the long term period.
Therefore, enhancing the potential to observe showers and isolated
thunderstorms across the U.S. Virgin Islands and Puerto Rico.

An upper low will continue over the region to end the week today,
moving away on Sunday, leaving ridging in the upper levels. In
general the diurnal pattern of morning and night passing showers
across windward areas of Puerto Rico and the US Virgin Islands, and
isolated to scattered afternoon convection, mainly over western
Puerto Rico, will continue, boosted today by the induced surface
trough and on Monday by trailing moisture from Invest 96L. Sea
breeze convergence, local effects, and diurnal heating will promote
shower and t-storm activity over the Cordillera Central to western
PR each afternoon with the risk of excessive rainfall being limited
to elevated. Convective activity can also develop downwind of El
Yunque, the USVI, Vieques and Culebra. Saharan Dust that will
continue over the islands during the period with generally low
concentrations.

Highs are forecast to still reach the upper 80s to low 90s over
urban and coastal areas of the islands, with heat indices surpassing
105°F. A Heat Advisory is once again in effect today from 10 AM to 5
PM AST for urban and coastal areas of Puerto Rico. A limited heat
threat is once again present today for the U.S. Virgin Islands,
Vieques and Culebra. Similar heat conditions are forecast for
tomorrow and Monday, with a limited to elevated heat risk. Lows will
be in the upper 70s and low 80s at coastal and urban areas, and the
upper 50s to low 70s at higher elevations. Patchy fog will also be
present during the overnight to early morning hours, mainly over
sectors of interior Puerto Rico.


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

Based on the latest model guidance, lingering tropical moisture
is expected to remain in the area through early Tuesday, with
precipitable water (PWAT) values ranging from 1.75 to 2 inches.
Although the main axis of the tropical wave, Invest 96L, is
forecast to move away over the open Atlantic waters on Monday,
trailing moisture will continue to enhance the potential for
showers and isolated thunderstorms across Puerto Rico and the U.S.
Virgin Islands.

Following this moisture, a moderate to high Saharan Air Layer
(SAL) is expected to arrive from Tuesday afternoon through at
least Wednesday. Under these conditions, shower activity will be
limited. However, with residual moisture, local effects, and
daytime heating, afternoon convection and isolated thunderstorms
are likely each day, particularly across the western
municipalities of Puerto Rico. The U.S. Virgin Islands can expect
daily showers, mainly during the overnight and morning hours,
followed by warm to hot daytime temperatures. The flood risk will
vary between limited and elevated.

Regarding temperatures, no significant changes are expected.
Temperatures at the 925 mb level will remain near or above
climatological normal throughout most of the period. Heat indices
are likely to exceed 100°F each day. Residents and visitors are
advised to stay hydrated, limit outdoor activities during peak
heat hours, and take necessary precautions to avoid heat-related
illnesses. Don’t forget to keep your pets hydrated as well.

Toward the end of the forecast period, uncertainty increases.
Model guidance suggests the possible approach of a system near the
region, but confidence remains low at this time. Forecasts will
continue to be updated daily. This potential system is currently a
tropical wave being monitored by the National Hurricane Center,
located near the west coast of Africa. Some slow development is
possible next week as it moves west-northwestward across the
eastern and central tropical Atlantic. It currently has a 30%
chance of formation over the next seven days. As it is still too
early to determine any impacts on our region, residents and
visitors are encouraged to stay well informed and monitor future
forecasts as we head into next week.

&&

.AVIATION...
(06Z TAFs)

Mainly VFR conditions during the period. Passing SHRA will continue
to move through the region, moving over the VCTY of TIST/TISX/TJSJ/
TJBQ during the morning hours (Isol VCTS possible due to an induced
trough moving over the area). E-ENE flow up to 13 to 18 kts with
higher gusts. SHRA/ISOL TSRA mainly near the vicinity of TJBQ/TJPS
and possibly TJSJ at around 09/17z to 09/22z. Winds gradually
becoming more E to ESE. Winds decreasing after 09/22Z.

&&

.MARINE...

Moderate to locally fresh easterly winds are mainly expected over
the next few days, resulting in seas of around 2 to 4 feet. A surface
trough will continue to enhance rain activity and maintain the
potential for thunderstorms today. Afternoon convection is expected
to develop daily across the coastal waters of western Puerto Rico and
into the Mona Passage. Invest 96L is forecast to move well northeast
of the northern U.S. Virgin Islands by early next week; however,
trailing tropical moisture will continue to bring periods of shower
activity across the regional waters. Additionally, a Saharan Air
Layer (SAL) is expected to arrive in the region by Tuesday afternoon,
leading to reduced visibilities.

&&

.BEACH FORECAST...

The low risk of rip currents continues today along all beaches in
Puerto Rico and the U.S. Virgin Islands. However, it's important
to note that even when the risk is low, life-threatening rip
currents can still occur near groins, jetties, reefs, and piers. A
moderate risk of life-threatening rip currents is expected to
return along the north- and east-facing beaches of Puerto Rico and
the U.S. Virgin Islands starting Sunday night and continuing
onward. Additionally, with heat indices expected to exceed 100
degrees across coastal areas, it's important to stay hydrated and
take necessary precautions to avoid heat-related illnesses.

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
511 AM AST Sun Aug 10 2025

.KEY MESSAGES...

* A seasonal pattern is forecast for the islands for the rest of
the short-term forecast, with afternoon convection each day.

* For the U.S. Virgin Islands, residents can expect mostly
passing showers during morning hours and temperatures that would
range between the upper 80s and the low 90s.

* Moderate to high concentrations of Saharan dust are expected to
arrive by Tuesday and warm and hot conditions will likely
persist across the islands.

* The NHC is monitoring a tropical wave that has a high chance
(70%) of formation over the next 7 days. Residents and visitors
are encouraged to stay informed and monitor future forecasts, as
updates are issued regularly.

&&

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

Since midnight, radar estimated accumulations over land indicate
that eastern PR, Vieques and the U.S. Virgin Islands were affected
by showers due to a surface disturbance. By 450 AM, Naguabo saw the
highest, radar estimated since midnight, accumulations by far with
around 1.25in. Although radar estimated accumulations since midnight
show up to around 0.02 in over the northern USVI, St. Croix saw
around 0.31 in. Current satellite derived precipitable water (PWAT)
values show from 1.55 inches over western PR to 1.70 in over eastern
PR and the USVI. E to ESE steering flow is forecast to continue
during the rest of the period, with mainly ESE flow being present
today.

Although PWAT values over 2 inches will be present during afternoon
convection, moisture trailing from Invest 96L over the central
Atlantic is forecast to arrive by Monday night and into Tuesday.
This moisture arriving on Monday can also reach over 2 inches of
PWAT. Although Invest 96L itself will likely move well northeast of
the islands, this trailing moisture associated with the system will
reach the islands and therefore, enhancing the potential to observe
showers and isolated thunderstorms across the U.S. Virgin Islands
and Puerto Rico. Although this moisture will continue through
Tuesday, Saharan Dust will also filter in during this period.
Current low Saharan Dust concentrations will continue over the
islands through the overnight hours of Monday into Tuesday. By
Tuesday morning (and into the long term forecast period) a Saharan
Air Layer (SAL) with (according to the latest model guidance)
moderate to high concentrations of Saharan Dust will move over the
region, promoting hazy skies and deteriorating air quality.

Surface disturbances will continue to reach the islands through most
of the period. An upper low will continue moving away from the
islands to our west today, leaving ridging in the upper levels. In
general the seasonal pattern of morning and night passing showers
across windward areas of Puerto Rico and the US Virgin Islands, and
isolated to scattered afternoon convection, mainly over interior to
western Puerto Rico, will continue, boosted by the surface
disturbances and then by trailing moisture from Invest 96L. Sea
breeze convergence, local effects, and diurnal heating will promote
shower and t-storm activity over the Cordillera Central to western
PR each afternoon (under ESE steering flow today) with the risk of
excessive rainfall being limited to elevated. Convective activity
can also develop downwind of El Yunque (towards the metro area), the
USVI, Vieques and Culebra. Outflow showers can also linger over land
through the evening hours.

Highs will reach the upper 80s to low 90s over urban and coastal
areas of the islands, with heat indices surpassing 105°F. A Heat
Advisory is once again in effect today from 10 AM to 5 PM AST for
urban and coastal areas of Puerto Rico. A limited heat threat will
persist today for the U.S. Virgin Islands, Vieques and Culebra.
Similar heat conditions are forecast for tomorrow and, possibly more
elevated on Tuesday, with a limited to elevated heat risk. Lows will
be in the upper 70s and low 80s at coastal and urban areas, and the
upper 50s to low 70s at higher elevations. Patchy fog will also be
present during the overnight to early morning hours, mainly over
sectors of interior Puerto Rico.


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

Around mid-week, the Saharan Air Layer (SAL), with moderate to
high concentrations of dust particles, is expected to persist
across the region, promoting hazy skies and poor air quality.
However, these conditions should gradually improve from Thursday
afternoon onward. Moisture content is expected to oscillate
between normal and above-normal levels, as trailing tropical
moisture occasionally moves in on Wednesday within the trade
winds. Under these conditions, variable weather is anticipated
most days of the forecast period, followed by afternoon convection
and isolated thunderstorms, fueled by residual moisture, local
effects, and daytime heating. Additionally, lower heights and
cooler temperatures at the 500 mb level are expected on Wednesday,
which may enhance thunderstorm development during the afternoon
hours, particularly across the western municipalities of Puerto
Rico. The U.S. Virgin Islands can expect daily showers, mainly
during the overnight and morning hours, followed by warm to hot
daytime temperatures.

Another ongoing concern will be the continued warm to hot
temperatures. Temperatures at the 925 mb level will remain near
or above climatological normal throughout most of the period. Heat
indices are likely to exceed 100°F each day. Residents and
visitors are advised to stay hydrated, limit outdoor activities
during peak heat hours, and take necessary precautions to avoid
heat-related illnesses. Don’t forget to keep your pets hydrated as
well.

Toward the end of the forecast period uncertainty increases, and
the forecast will depend on the development of Invest 97L, an area
currently being monitored by the National Hurricane Center. It
currently has a 70% chance of formation over the next seven days.
At this time, model guidance suggests it will move well northeast
of the region, though it could still trigger marine and coastal
hazards over the upcoming weekend. This potential system is
currently a broad area of low pressure associated with a tropical
wave and is producing a large area of disorganized showers and
thunderstorms just to the east and southeast of the Cabo Verde
Islands. Environmental conditions appear conducive for gradual
development, and a tropical depression is likely to form by the
middle to latter part of the upcoming week. As it is still too
early to determine any direct impacts on our region, residents and
visitors are encouraged to stay informed and monitor future
forecasts, as updates are issued regularly.

&&

.AVIATION...
(06Z TAFs)

Mainly VFR conditions during the period. SHRA will continue to move
over or in the VCTY of TIST/TISX/TJSJ during the morning hours (Isol
VCTS possible). ESE flow up to 13 to 18 kts with higher gusts.
Afternoon SHRA/ISOL TSRA mainly near the vicinity of TJBQ/TJPS,
downwind of TISX/TIST and possibly near TJSJ, due to El Yunque
Streamer, at around 10/17z to 19/22z. Winds decreasing after 10/22Z.

&&

.MARINE...

Moderate to locally fresh easterly winds are expected over the next
few days, resulting in seas of around 2 to 4 feet. Afternoon
convection is expected to develop each day across the coastal waters
of western Puerto Rico and into the Mona Passage. Early next week,
the Invest 96L is forecast to move well northeast of the the region,
but trailing tropical moisture will bring periods of shower activity
across the regional waters. By Tuesday into mid week, a Saharan Air
Layer is expected to arrive, leading to reduced visibilities.
Additionally, the Invest 97L, monitored by the National Hurricane
Center, is forecast to also move well northeast of the region, but it
could trigger some marine hazards by the upcoming weekend.

&&

.BEACH FORECAST...

A low risk of rip currents continues today along all beaches in
Puerto Rico and the U.S. Virgin Islands. However, it's important
to note that even when the risk is low, life-threatening rip
currents can still occur near groins, jetties, reefs, and piers.
Beginning tonight and continuing onward, the risk will increase to
moderate along north and east facing beaches of Puerto Rico and
Culebra, and occasionally along the U.S. Virgin Islands. Beachgoers
are advised to exercise caution and follow the recommendations of
local officials. Additionally, with heat indices expected to exceed
100°F across coastal areas, it is important to stay hydrated and
take necessary precautions to avoid heat-related illnesses. Looking
ahead to the upcoming weekend, Invest 97L should be monitored closely,
as it could potentially trigger marine and coastal hazards.

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
517 AM AST Mon Aug 11 2025

.KEY MESSAGES...

* Afternoon showers and isolated thunderstorms are expected
across the western interior to western Puerto Rico.

* For the U.S. Virgin Islands, warm day with passing showers
expected tonight.

* Moderate to high concentrations of Saharan dust are expected to
arrive tomorrow, Tuesday, with warm to hot conditions likely to
persist across coastal and urban areas. A Heat Advisory is in
effect once again today from 10 AM to 5 PM AST across urban and
coastal areas of Puerto Rico.

* The NHC is monitoring the Invest 97L, which has a high chance of
formation over the next 48 hours and the next 7 days (70% and
90%, respectively. Residents and visitors are encouraged to
stay informed and monitor future forecasts, as updates are
issued regularly.

&&

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

Current satellite derived precipitable water (PWAT) values show from
1.39 inches over western PR to 1.58 in over eastern PR, 1.65 in over
Vieques and Culebra, and 1.65 to 1.70 over the USVI. A patch of
relatively higher moisture is already over the USVI and making its
way towards PR during these early hours, under E to ESE steering
flow. PWAT values over 2 inches will be present during afternoon
convection and as a result of moisture trailing from Invest 96L over
the central Atlantic that is forecast to arrive by tonight, linger
on Tuesday, and gradually decrease on Wednesday. This moisture
arriving on Monday can also reach over 1.90 to 2 inches of PWAT.
Although Invest 96L itself will move well northeast of the
islands, this trailing moisture associated with the system will
reach the islands and therefore, enhancing the potential to
observe showers and isolated thunderstorms across the U.S. Virgin
Islands and Puerto Rico. Although this moisture will reach the
islands, Saharan Dust will also filter in during this period,
bringing some uncertainty to the forecast. By late Monday night
through Wednesday (and into the long term forecast period) a
Saharan Air Layer (SAL) with (according to the latest model
guidance) moderate to high concentrations of Saharan Dust will
move over the region, promoting hazy skies, reduced visibilities
and deteriorated air quality. Sensitive groups should take
precautions and monitor updates to the forecast.

With the upper level low that was present during the weekend, now
well west of the islands, ridging should persist in the upper
levels. An August diurnal pattern of morning and overnight passing
showers across windward areas of Puerto Rico and the US Virgin
Islands, and isolated to scattered afternoon convection, mainly over
interior to western Puerto Rico, will continue. This pattern can be
boosted by nearby surface disturbances and then by trailing moisture
from Invest 96L on Tuesday (when Galvez-Davidson Index values are
highest in the latest model run). Sea breeze convergence, local
effects, and diurnal heating will also promote shower and t-storm
activity over the Cordillera Central to western PR each afternoon
(under E to ESE steering flow through Tuesday, backing to become
more E to ENE on Wednesday) with the risk of excessive rainfall
being limited to elevated. Convective activity can also develop
downwind of El Yunque (towards the metro area), the USVI, Vieques
and Culebra. Outflow showers can also linger over land through the
evening hours, spreading towards other nearby areas.

Maximum temperatures will be in the upper 80s to low 90s over urban
and coastal areas of the islands, with heat indices surpassing
105°F. A Heat Advisory will be in effect from 10 AM to 5 PM AST
today for urban and coastal areas of Puerto Rico. A limited heat
threat will be present during those hours for the U.S. Virgin
Islands, Vieques and Culebra. Similar heat conditions, with a
limited to elevated heat risk, are forecast for Wednesday and,
possibly higher tomorrow. Lows will be in the upper 70s and low 80s
at coastal and urban areas, and the upper 50s to low 70s at higher
elevations. Patchy fog will also be present during the overnight to
early morning hours, mainly over sectors of interior Puerto Rico.


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

On Thursday, moderate to high concentrations of Saharan dust will
diminish, allowing for an improvement in air quality and
visibility. Model guidance indicates a patch of drier air mass,
with precipitable water (PWAT) values as low as one inch (below
the climatological normal) moving across the region, probably
reducing the potential for rainfall that day. By Friday, moisture
content will increase from seasonal to above seasonal levels.
Under these conditions, a typical summer weather pattern is
expected, with showers developing across eastern sectors in the
morning, followed by afternoon convection and isolated thunderstorms
fueled by available moisture, local effects, and daytime heating.
This activity could lead to ponding of water on roads and in poorly
drained areas, as well as flooding in urban zones and small streams.
Winds will begin to weaken due to a col region that will be
positioned over our area, resulting in slower- moving showers that
could lead to higher rainfall accumulations during the afternoon.

Heading into the weekend, weather models continue to show
discrepancies regarding various meteorological variables, making
the forecast more challenging at this time. The forecast will
largely depend on the development and path of Invest 97L, a well-
defined low-pressure area currently located over the eastern
portion of the Cabo Verde Islands. The system is being monitored
by the National Hurricane Center and currently has a high chance
of formation over the next 48 hours and the next seven days (70%
and 90%, respectively). At this time, model guidance suggests it
will track well northeast of the region, approximately 250 to 300
miles northeast of San Juan, though it could still affect us
indirectly by generating marine and coastal hazards over the
upcoming weekend, particularly across Atlantic waters and north-
facing beaches. Northerly winds are expected on Saturday. Then, as
the system moves away into the western Atlantic, winds will shift
to southerly on Sunday and Monday and remain light. PWAT values
will likely range from seasonal to above normal, as these
southerly winds transport trailing tropical moisture, potentially
increasing rain chances during the weekend into early next week.
At the moment, the flood risk ranges from limited to elevated.
Since it is still too early to determine any direct impacts on our
region, residents and visitors are encouraged to stay informed
and monitor future forecasts, as updates will be issued regularly.

&&

.AVIATION...
(06Z TAFs)

Mainly VFR conditions. Passing SHRA will continue to move in the
VCTY of TIST/TISX/TJSJ during the morning hours (Isol VCTS
possible). E to ESE steering flow up to around 12 to 18 kts with
higher gusts and sea breeze variations. Afternoon SHRA/ISOL TSRA in
the vicinity of TJBQ/TJPS and possibly near TJSJ, due to El Yunque
Streamer, at around 11/17z to 11/22z. Winds decreasing after 11/22Z.

&&

.MARINE...

Gentle to moderate easterly winds are expected over the next few days,
resulting in seas of around 2 to 4 feet, locally higher up to 5 feet.
Tropical moisture will bring periods of shower activity across the
regional waters and afternoon convection is expected to develop each
day across the coastal waters of western Puerto Rico and into the
Mona Passage. A Saharan Air Layer is expected to arrive tomorrow,
leading to reduced visibilities through at least Thursday morning.
Additionally, the Invest 97L, monitored by the National Hurricane
Center, is forecast to move northeast of the region by the upcoming
weekend and it could trigger some marine hazards. Stay informed and
monitor future forecasts.

&&

.BEACH FORECAST...

There is a moderate risk of life threatening rip currents along
the north and east facing beaches of Puerto Rico, Culebra, St.
Thomas and St. John today. A low risk of rip currents is present
elsewhere, however, it's important to note that even when the risk
is low, life-threatening rip currents can still occur near
groins, jetties, reefs, and piers. Beachgoers are advised to
exercise caution and follow the recommendations of local
officials. Additionally, with heat indices expected to exceed
100°F across coastal areas, it is important to stay hydrated and
take necessary precautions to avoid heat-related illnesses.
A moderate risk will likely persist through the week. Looking
ahead to the upcoming weekend, Invest 97L should be monitored
closely, as it could potentially trigger coastal hazards in our
region.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
528 AM AST Tue Aug 12 2025

.KEY MESSAGES...

* An Easterly perturbation will bring showers and thunderstorms across
the region today, creating an elevated risk of flooding,
especially during the afternoon.

* A Heat Advisory is in effect for Puerto Rico and the US Virgin
Islands as the day began warmer than normal, with plenty of
available moisture, and high expected maximum temperatures this
afternoon.

* Hazy skies due to moderate to high concentrations of suspended
Saharan Dust Particles will be observed from today through early
Thursday morning.

* The National Hurricane Center (NHC) trajectory forecast for
Erin put it off to the northeast, away from Puerto Rico and the
US Virgin Islands as early as Friday night and most likely
around Saturday morning.

* We urge residents and visitors of Puerto Rico and the US Virgin
Islands to closely monitor the progress of Hurricane Erin this
weekend, as the forecast is directly related to it.

&&

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

It was an overall quiet night across Puerto Rico and the U.S. Virgin
Islands. Satellite imagery showed clear to partly cloudy skies.
After 2 AM, scattered showers and a few thunderstorms began to move
across the Caribbean waters. Some showers reached the southeast
coast of Puerto Rico, with minimal accumulations based on radar
estimates. Overnight temperatures remained in the upper 70s to low
80s across urban and coastal areas of the islands, including the
USVI, while temperatures in the higher elevations of Puerto Rico
ranged from the upper 60s to low 70s.

Today, an easterly perturbation will result in increased shower and
thunderstorm activity across the forecast area, starting in the USVI
and eastern Puerto Rico and spreading westward throughout the day.
The latest model guidance shows precipitable water values ranging
from 1.5 to 2.0 inches associated with this perturbation.
Additionally, behind this moisture, a pulse of Saharan dust with
moderate to high concentrations is expected. Skies are forecast to
gradually become hazy today, with those conditions likely to persist
through at least Wednesday night or Thursday morning. This will lead
to poor air quality for individuals with asthma or allergies.

It is important to note that 500 mb temperatures are expected to
cool today, reaching down to -8.5°C. Combined with diurnal heating,
Saharan dust, local effects, and moisture associated with the
perturbation, there is an increased potential for strong
thunderstorms this afternoon across interior and western Puerto
Rico. This also increases the risk of flooding in urban areas,
roads, small streams, and washes. Given these conditions, expect a
variable weather pattern with hazy skies, warm temperatures, and
afternoon convection. Also, as the day began with higher-than-normal
temperatures, and with 925 mb temperatures above normal and moisture
followed by dust moving over the area today, a Heat Advisory is in
effect across all urban and coastal areas of Puerto Rico, Vieques,
Culebra, and the U.S. Virgin Islands. It is important to stay
hydrated and take necessary precautions to avoid heat-related
illnesses.

On Wednesday, hazy skies will prevail, and the potential for
afternoon showers and thunderstorms will continue across interior
and western Puerto Rico, mainly fueled by patches of moisture, upper-
level divergence, and an induced surface trough. The flood risk
remains limited at this time. By Thursday, moderate to high
concentrations of Saharan dust will diminish, leading to improved
air quality and visibility. Model guidance indicates a patch of
drier air, with precipitable water (PWAT) values as low as one inch,
below the climatological normal, moving across the region. This will
likely reduce the potential for rainfall and flooding on that day.

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

Model guidance suggests an area of subsidence arriving across the
region on Friday. As a result, we can expect the warm to hot
spell to extend into the long term for Puerto Rico and the US
Virgin Islands. Then, the available moisture, with local effects,
sea breeze, and the excessive heating will result in afternoon
convection across the interior and western locations of PR and
downwind from the US Virgin Islands. This area of subsidence will
be followed by an increase in moisture associated with a wind
surge and outer bands that are forecast to detach from Erin's
movement, which could increase the potential to observe squally
weather as early as late Friday night and most likely around
Saturday morning or afternoon. However, we urge residents and
visitors of Puerto Rico and the US Virgin Islands to closely
monitor the progress of Hurricane Erin this weekend, as the
forecast is directly related to it. It is too early to determine
what impacts, if any, Erin may bring to the US Virgin Islands and
Puerto Rico.

Regardless of the changes that Erin will experience in the next
few days, the PR and the USVI's local weather will be closely tied
to its evolution. The NHC Erin's forecast trajectory moves off to
the northeast away from the islands. That said, and assuming that
the NHC Erin's trajectory forecast materializes, the winds should
become out from the south to southwest, lifting plenty of
tropical moisture over the islands, extending the warm to hot
spell and at the same time the potential to observe strong
convection across portions of the northeast coast of PR, St Croix,
St Tomas and St John from Sunday to Monday. The winds should
return from the east by Tuesday, along with the typical weather
pattern. Currently, we have a high uncertainty in this forecast,
associated with the expected changes that we can anticipate for
Erin.

&&

.AVIATION...
(06Z TAFs)

Mostly VFR conditions are expected across TAF sites this morning.
Frequency of VCSH are expected to increase later this morning across
USVI sites and TJSJ. A significant area of suspended Saharan dust
particles will arrive over the islands today resulting in reduced
visibilities. VCTS are expected to develop aft 12/17Z, especially
affecting TJBQ and TJPS. Winds with an easterly component at around
10 to 15 kts with typical sea breeze variations and occasionally
higher gusts, mainly near thunderstorms. Winds below 10 kts after
12/23Z.

&&

.MARINE...
An easterly perturbation will bring an increase in showers and
thunderstorms with locally higher winds and seas near this activity
across the local waters today. After today's perturbation, the high
pressure will build over the Central Atlantic Ocean, promoting
moderate to locally fresh easterlies with moderate chops to choppy
seas. Erin, monitored by the National Hurricane Center, is forecast
to move off to the northeast of the Northeast Caribbean as early as
Friday night and most likely around Saturday morning. Based on this
trajectory forecast, marine conditions could deteriorate by the
upcoming weekend. We encourage mariners and visitors to monitor the
evolution of Erin actively.

&&

.BEACH FORECAST...

There is currently a moderate risk of rip currents across the
north and east-facing beaches in Puerto Rico and the US Virgin
Islands. Thunderstorms will develop across the local waters due to
an easterly perturbation and may approach some coastal areas.
Please exercise caution.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
522 AM AST Wed Aug 13 2025

.KEY MESSAGES...

* Another warm and hot day with hazy skies due to suspended
Sahara dust particles in Puerto Rico and the US Virgin Islands.

* Residents and visitors in PR and the USVI can expect the hot and
warm spell to persist throughout the workweek with a seasonal
hydrological pattern, consisting of quick passing showers across
the windward locations and strong afternoon convection over
western PR.

* The National Hurricane Center's trajectory forecast for Erin
indicates that it will move to the northeast, away from Puerto
Rico and the US Virgin Islands, with its external bands moving
as early as late Friday night or early Saturday morning, and
most likely around Saturday evening.

* We encourage everyone in Puerto Rico and the U.S. Virgin
Islands to keep an eye on Erin over the next few days, as the
intensity and track forecast will undergo changes, and our
weather conditions depend on its progress.

&&

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

Satellite imagery showed clear to partly cloudy skies overnight.
Some showers that moved across the Atlantic waters reached the north-
central to eastern coasts of Puerto Rico, with minimal accumulations
recorded based on radar estimates. Overnight temperatures remained
in the upper 70s to low 80s across urban and coastal areas of the
islands, including the U.S. Virgin Islands (USVI), while
temperatures in the higher elevations of Puerto Rico ranged from the
upper 60s to low 70s. Once again, as the day began with higher-than-
normal temperatures, 925 mb temperatures above average, and the
presence of dust particles in the area, a Heat Advisory is in effect
across all urban and coastal areas of Puerto Rico, Vieques, Culebra,
and the USVI. Heat indices are expected to meet or exceed advisory
criteria. It is important to stay hydrated and take necessary
precautions to avoid heat-related illnesses.

The short-term forecast will mostly feature a seasonal rain pattern,
with morning and nighttime passing showers over regional waters and
windward sections of Puerto Rico and the USVI. However, diurnal
heating and local effects will trigger daily scattered to locally
numerous afternoon showers and isolated thunderstorms across the
western interior and southwestern municipalities of Puerto Rico, as
winds will be blowing from the northeast from the surface up to 500
mb through Friday.

Today, even though moderate to high concentrations of Saharan dust
remain over the area and are expected to persist through at least
tomorrow morning, the latest model guidance shows precipitable water
(PWAT) values ranging from 1.5 to 1.8 inches. Combined with diurnal
heating and local effects, afternoon convection is expected to
develop as mentioned above. This also increases the risk of urban
and small stream flooding, especially across roads and low-lying
areas. The flood risk ranges from limited to elevated across the
southwestern quadrant of Puerto Rico during the afternoon hours.

Similar conditions are anticipated through Friday. However, tomorrow
(Thursday), model guidance indicates a patch of drier air, with PWAT
values as low as one inch—below climatological normals—moving across
the region. This will likely reduce rainfall and flooding potential,
resulting in more localized activity with lower accumulations.

.LONG TERM...Saturday through Wednesday

Based on the latest NHC's trajectory and intensity forecast for
Erin, its center should move off to the northeast of the Northeast
Caribbean around early Sunday morning. However, Erin's external
rain bands could arrive as early as Saturday morning and most
likely around Saturday evening. Our readers should be made aware
that the NHC track forecast has an average error of 150-215
statute miles at 4 and 5 days, so we expect future adjustments to
the forecast. Thus, we encourage everyone in Puerto Rico and the
U.S. Virgin Islands to keep an eye on Erin over the next few days,
as the intensity and track forecast will undergo changes, and our
weather conditions depend on its progress. That said, this
forecast will bring squally weather, especially for the US Virgin
Islands and the windward locations of PR, on Saturday.

As Erin follows the NHC track forecast, winds will shift from the
south to southwest around Sunday, pooling plenty of tropical
moisture over the islands, increasing the potential to observe
urban flooding, landslides, and river flooding, as well as
mudslides along steep terrains. The areas where the most active
weather will remain possible will be the US Virgin Islands, the
southeastern slopes, the northeast, and the northeast interior
portion of PR. Keep in mind this is tied to the final behavior of
Erin, so the level of uncertainty is still high. The unsettled
weather pattern could extend even into Monday or Tuesday due to
the southerly wind flow that Erin could promote over the region.
Additionally, this wind flow combined with the plenty of tropical
moisture will likely promote a warm to hot spell, especially
between mid-morning and the afternoon.

Model guidance suggests the arrival of another tropical wave as
the winds reestablish from the east late Tuesday night into
Wednesday.

&&

.AVIATION...
(06Z TAFs)

Mostly VFR conditions are expected this forecast period. A
significant area of suspended Saharan dust particles is over the
area reducing visibilities. Frequency of VCSH are expected to
increase later this morning across TJSJ and tonight across USVI TAF
sites. VCTS are expected to develop aft 13/17Z, especially affecting
TJPS. Winds with an easterly component at around 10 to 15 kts with
typical sea breeze variations and occasionally higher gusts, mainly
near thunderstorms. Light winds or below 10 kts after 13/23Z.

&&

.MARINE...

Moderate easterlies will promote moderate chops across the regional
waters through at least Friday. NHC's trajectory and intensity
forecast moves Erin off to the northeast of the Northeast Caribbean
by early Sunday morning. Based on this forecast, the external
bands of Erin could impact the region as early as early Saturday
morning and most likely around Saturday evening. Under this
weather pattern, marine conditions will deteriorate by the
upcoming weekend. We encourage mariners and visitors to monitor
the evolution of Erin actively.

&&

.BEACH FORECAST...

There is currently a moderate risk of rip currents across the
north and east-facing beaches in Puerto Rico and the US Virgin
Islands. Thunderstorms will develop across the local waters due
to an easterly perturbation and may approach some coastal areas.
Please exercise caution.

Erin's swell action could deteriorate marine and coastal
conditions, creating life-threatening rip currents for this
upcoming weekend.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
532 AM AST Thu Aug 14 2025

.KEY MESSAGES...

* A Heat Advisory is in effect for the urban and coastal areas of
Puerto Rico and the U.S. Virgin Islands from 10 AM AST this
morning through 5 PM AST this afternoon.

* For the U.S. Virgin Islands, light to moderate showers during
the morning hours, while convection activity will increase
flooding risk across interior and western sections of Puerto
Rico in the afternoon.

* An induced surface perturbation will bring frequent passing
showers across the U.S. Virgin Islands and windward sections of
Puerto Rico early Friday morning.

* Tropical Storm Erin is forecast to move near the islands by
Saturday. As a result, residents can expect hazardous marine
and coastal conditions from Saturday through Monday. Please
stay tuned for further weather updates on this tropical system.


&&

.SHORT TERM...Today through Saturday

A surge of moisture embedded in the trades produced scattered to
numerous showers across the regional waters of Puerto Rico and the
US Virgin Islands. This activity moved inland across the USVI and
windward locations of PR occasionally overnight. Winds were mainly
from the east to east-northeast at 10 mph or less, but with brief
gusty winds, and under land breeze fluctuation across the leeward
side of the islands. Additionally, and once again, we observed
another night with warmer-than-normal minimum temperatures.

Additional moisture embedded in the trades will bring another day
with occasional showers across the windward locations in the USVI
and PR. At the same time, this moisture will combine with the above-
normal maximum temperatures to result in another day with warm to
hot heat indices, especially across the urban coastal locations in
PR and the US Virgin Islands. As a result, a Heat Advisory is in
effect from 10 AM AST to 5 PM AST. This level of heat affects most
individuals sensitive to heat, especially those without effective
cooling and/or adequate hydration. By the afternoon, another round
of strong convection will result in flooding rains across the
interior and western locations of PR, and downwind from the USVI.
Western PR has an elevated risk of observing flooding rains today,
while the USVI has a limited risk of flooding rains.

On Friday, an induced surface perturbation will bring frequent
passing showers across the USVI and windward sections of PR early
Friday morning. However, the warm to hot spell will continue by mid-
morning into the afternoon, as the perturbation exits the region,
leaving its lingering moisture over us. The perturbation will be
followed by an area of subsidence ahead of Erin, which will limit
rain activity before the onset of the external bands of the system,
which are forecast to arrive as early as Saturday morning and most
likely around Saturday evening. This pattern will result in squally
weather, which could cause strong gusty winds (in some instances,
these squalls could bring tropical storm wind force) and occasional
periods of heavy rain.


&&


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

The long-term forecast remains on track, as the wet and unsettled
pattern is expected to continue. Based on the latest NHC's
trajectory and intensity forecast for Erin, its center should move
off to the northeast of the Northeast Caribbean around early
Sunday morning. However, if this forecast validates, Erin's
external rain bands could turn more frequent as Erin approaches
the islands from a distance. Nevertheless, the proximity of Erin
will shift from the south to the southwest around Sunday, pooling
plenty of tropical moisture over the islands through Monday.
Based on the latest model guidance, Precipitable Water values are
likely to exceed the 75th percentile (2.0 - 2.2 inches, with low
chance of reaching 2.4 inches), well above climatological normal.
Under a S-SW wind flow, it is likely to observe an advective
pattern during the morning hours, with showers and thunderstorms
affecting windward sections of the local islands, but the concern
remains high for the interior and northern portions of Puerto Rico
and the U.S. Virgin Islands. Due to continuous shower activity
and saturated soils, the potential to observe urban flooding,
landslides along steep terrains, and river flooding will increase.
We expect future adjustments to the forecast due to the existing
error associated with day 4 in the forecast. Thus, we encourage
everyone in Puerto Rico and the US Virgin Islands to keep an eye
on Erin over the next few days, as the intensity and track
forecast will undergo changes, and our weather forecast depend on
its progress. Stay tuned for further updates.

By Tuesday night, a surface high pressure over the Central
Atlantic should strengthen, promoting winds from the southeast.
Based on the deterministic guidance of the GFS and ECMWF, PWAT
will likely decrease to seasonal values (1.6 - 1.8 inches).
Nevertheless, model solutions currently agree that an upper-level
trough will likely approach the CWA by Wednesday morning,
increasing moisture content once again.

With a S-SE wind flow, abundant moisture, and above- normal 925
mb temperatures, the heat risk is likely to increase early next
week. The most likely scenario would be heat indexes across urban
and coastal areas reaching Heat Advisory or Heat Warning Criteria,
but this will depend on the behavior of Erin during that period.


&&


.AVIATION...

(06Z TAFs)

Expect VFR conditions through much of the forecast period.
Occasional SHRA will arrive across IST/ISX/JSJ throughout the day,
with SHRA/TSRA developing across the interior and western sections
of PR by this afternoon (14/16-23z). This TSRA could impact JBQ and
the VCTY of JPS. Expect E-ENE winds at around 10 kt through at least
14/13z, after that, they when will range between 15-20 kt with
higher gusts and sea breeze variations.


&&


.MARINE...

An induced easterly perturbation crossing the Lesser Antilles will
move across PR and the USVI tomorrow, increasing shower activity,
local winds, and seas mainly across the Caribbean Sea. The external
bands of Erin, producing squally weather, will arrive as early as
Saturday morning and most likely around Saturday evening, as Erin's
NHC trajectory forecast moves it off to the northeast away from
PR/USVI over the Atlantic Ocean throughout the weekend. Erin's
hazardous swell action will impact the Atlantic and Caribbean
Passages from Saturday evening through at least early next week.
Mariners and visitors are urged to closely monitor the evolution of
Erin.


&&


.BEACH FORECAST...

The risk of rip currents continues across the north and east-
facing beaches in Puerto Rico and St. Croix in the U.S. Virgin
Islands. Thunderstorms are expected to develop across the local
waters and may approach some coastal areas during the morning.
Additionally, showers and thunderstorms over interior and western
Puerto Rico could move over coastal areas as well. Beachgoers
must exercise cautions and stay weather alert.

IMPORTANT: Erin's swell action could deteriorate marine and
coastal conditions, creating life-threatening rip currents for
this upcoming weekend. Residents and visitors are urge to avoid
the coastal areas from Saturday afternoon trough Monday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
443 AM AST Fri Aug 15 2025

.KEY MESSAGES...

* Residents and visitors in Puerto Rico (PR) and the US Virgin
Islands (USVI) are encouraged to closely monitor the development
of Erin, as the National Hurricane Center (NHC) forecasts its
trajectory to move northeast of the islands across the Atlantic
Ocean.

* Additionally, wave actions associated with Erin will lead to
deteriorating marine and coastal conditions across the USVI and PR
from Saturday evening through at least early next week.

* The outer bands of Erin are expected to bring showers and
thunderstorms with gusty winds to the islands, starting as early
as late tonight or early Saturday morning, with the most
significant impacts likely occurring around Saturday evening.

* We anticipate rainfall totals of between 2 and 4 inches, with
isolated higher amounts possible, particularly across the
southern, southeastern, eastern interior, and northeastern areas
of Puerto Rico, as well as throughout the US Virgin Islands due to
Erin.


&&


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

An induced surface trough moved across the USVI and PR overnight,
producing showers and isolated thunderstorms. We observed between 1
and 2.5 inches of rain, mainly across the northern half of PR, while
the northern US Virgin Islands obtained less than a quarter of an
inch. Winds were primarily from the east to east-northeast at 10 mph
or less, but with strong gusty winds near the shower and
thunderstorm activity, while the leeward side of PR was under the
effects of the land breeze. Additionally, low temperatures were in
the low 80s and upper 70s along the coastal areas to the mid-60s in
the mountains.

The lingering moisture of the induced surface trough will slowly
exit the islands, promoting the formation of some showers across the
regional waters and the windward locations in the US Virgin Islands
and PR. Rain activity will diminish somewhat during the day, as an
area of subsidence in front of Erin moves from the east. However,
local effects and sea breezes will aid in the formation of showers
and thunderstorms across the interior and western PR this afternoon,
as well as downwind from the USVI. The strongest thunderstorms could
produce heavy rainfall, promoting an elevated flooding risk.

The external rain bands of Erin will move across the islands as
early as late tonight or early Saturday morning, affecting the
Atlantic Offshore Waters, Anegada Passage, the US Virgin Islands,
and the north and east of PR. These rain bands will arrive
occasionally, resulting in squally weather with thunderstorms, heavy
rain, and gusty winds (with speeds between 30 and 40 mph, or even
greater). The frequency of this activity will increase as Erin
approaches the islands by early Sunday morning.

Based on the latest NHC's trajectory and intensity forecast for
Erin, its center should move off to the northeast of the Northeast
Caribbean around early Sunday morning. The bright side is that model
consensus still agrees with this forecast. Thus, due to the
proximity of Erin, winds will shift from the south to southwest
around Sunday afternoon, pooling plenty of tropical moisture over
the islands, increasing the potential to observe urban flooding,
landslides along steep terrains, and river flooding.

Please be advised that we encourage everyone in Puerto Rico and the
US Virgin Islands to keep an eye on Erin over the next few days, as
our weather conditions depend on its progress.


&&


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

Some changes were introduced to the long-term forecast, increasing
uncertainty for the second part of the next workweek. The latest
probabilistic guidance of the GFS and ECMWF shows agreement of
Precipitable Water values remaining above the 75th percentile (2.0 -
2.2 inches), due to possible tropical moisture pooled by Tropical
Storm Erin. As mentioned in the previous discussion, the main areas
of concern are the interior and northern portion of Puerto Rico and
the U.S. Virgin Islands due to S-SE wind flow combined with diurnal
heating and local effects. Additionally, previous rainfall activity
and saturated soils could enhance the potential of urban flooding,
landslides, and river rises over the aforementioned areas. Once
again, the flooding risk will remain limited to elevated for most
portions of Puerto Rico and the U.S. Virgin Islands. Residents and
visitors should continue to monitor the system and stay tuned for
further updates.

Moisture content is expected to gradually decrease by Wednesday as
Erin migrates northeastward into the Western Caribbean based on the
latest NHC Advisory. A surface high pressure should settle just
northeast of the CWA and linger for the next few days, promoting
winds from the southeast. An upper-level trough should approach the
local area, increasing moisture content, cooling 500 mb temperatures
and increasing instability aloft. Nevertheless, there’s some
uncertainty introduced to the forecast, mainly for Friday, due to
another tropical wave approaching the Caribbean Basin, although
there are some discrepancies. The GFS 06z solution shows a potential
tropical cyclone moving across the Central Atlantic, turning north
before approaching the CWA , while the ECMWF 00z solution shows
this disturbance approaching the local area. Based on the
deterministic guidance, the grand ensemble shows a gradual
increase in moisture content, but there is high variability in
PWAT values during that time period. Since these conditions are
expected at the end of the forecast period, uncertainty remains
high, and changes to the forecast will continue for the next few
days.

If the wind flow remains with a southerly component, abundant
moisture content, and above climatological normal 925 mb
temperatures, the heat risk will likely continue limited to elevated
across urban and coastal areas of Puerto Rico and the U.S. Virgin
Islands during the long-term forecast. Tuesday and Wednesday are
likely to be the hottest days of the period, with heat indexes
meeting Heat Advisory Criteria.

&&

.AVIATION...

(06Z TAFs)

Expect VFR conds thru the fcst prd, with occasional showers
arriving across IST/ISX/JSJ throughout the day. SHRA/TSRA will
develop across the interior and W-PR, promoting mountain obsc in PR
btwn 15/16-23z, impacting JBQ and the VCTY of JPS. The External
bands of Erin will begin to impact the local flying area aft 15/23z,
slowly increasing in frequency throughout Saturday. Expect E-ENE
winds at around 10 kt through at least 15/13z, after that, they will
range between 15-20 kt with higher gusts and sea breeze.


&&


.MARINE...

An induced easterly perturbation exiting the local area will
continue producing showers and thunderstorms through midday,
increasing local winds, and seas mainly across the Caribbean waters.
The external bands of Erin, producing squally weather, should arrive
as early as tonight or early Saturday morning. Based on the National
Hurricane Center trajectory forecast, Erin should move off to the
northeast away from Puerto Rico and the U.S. Virgin Islands into the
Western Atlantic on Sunday. Erin is expected to produce hazardous
swell action that will impact the Atlantic and Caribbean passages
from Saturday evening through at least early next week. Mariners and
visitors are urged to closely monitor the evolution of Erin.


&&


.BEACH FORECAST...

No major changes were introduced to the beach forecast. Today, the
moderate risk is expected to continue over north and east-facing
beaches of Puerto Rico, Culebra, and St. Croix. Nevertheless, beach
conditions are expected to gradually deteriorate as Tropical Storm
Erin, expected to upgrade to Hurricane later today, moves closer
to the region this weekend. Erin's swell action could deteriorate
marine and coastal conditions, creating life-threatening rip
currents for this upcoming weekend. Residents and visitors are
urged to avoid the coastal areas from Saturday afternoon through
Monday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
502 AM AST Sat Aug 16 2025

.KEY MESSAGES...

* Erin has rapidly intensified into a Major Hurricane.

* A Flood Watch is in effect for the US Virgin Islands and Puerto
Rico due to the proximity of Hurricane Erin through at least
Monday.

* The external bands of Hurricane Erin will bring showers and
thunderstorms, producing periods of moderate to locally heavy rain
and gusty winds across the US Virgin Islands and Puerto Rico today.

* Winds will shift from the south to southwest late tonight into
tomorrow (Sunday), promoting an unsettled weather pattern, and
continuing the risk of urban, river, and flash flooding as well as
landslides across Puerto Rico and the US Virgin Islands Sunday and
Monday.

* Additionally, the wave actions associated with Erin will lead to
deteriorating marine and coastal conditions across the USVI and PR
from this evening through at least early next week.


&&


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

Hurricane Erin has rapidly intensified into a Major Hurricane early
this morning. The external bands of Erin began to move across the
Atlantic Waters and Anegada, then inland across the US Virgin
Islands and Puerto Rico overnight. We observed between 0.25 and 1
inch of rain, mainly across the northern sections of PR and the US
Virgin Islands. Winds were primarily from the north at 10 mph or
less, but with higher gusty winds associated with the external band,
while the leeward side of PR was under the effects of the land
breeze. Additionally, low temperatures were in the low 80s and upper
70s along the coastal areas to the mid-60s in the mountains.

The external rain bands of Erin will continue to move across the
islands throughout the day, affecting the Atlantic Offshore Waters,
Anegada Passage, the US Virgin Islands, and the north and east of
PR. These occasional rain bands will produce squally weather with
thunderstorms, heavy rain, and gusty winds (with speeds around 40
mph, or even greater). The frequency of this activity will increase
as Erin approaches the islands by late tonight into early Sunday
morning. Erin's closest approach should be around 155 statute miles
(mi) off to the north-northeast (NNE) of St John/St Thomas this
afternoon and around 172/176 mi off to the NNE of Culebra/Fajardo
this evening.

Marine and coastal conditions will rapidly deteriorate this evening
due to Erin's wave field. Hazardous breaking waves will result in
life-threatening rip currents and minor beach erosion from this
evening through at least early Monday afternoon along the north and
east-facing beaches in PR and the USVI.

Local winds will slowly shift from the south to southwest around
late tonight or Sunday and into Monday as Erin moves at a safe
distance and away from the USVI and PR. This wind flow will pool
plenty of tropical moisture, extending the risk of heavy rain
causing urban, river, and flash flooding, as well as landslides
along steep terrains. Thus, a Flood Watch is in effect for the USVI
and PR, through at least Monday. Storm rainfall totals will range
between 1 and 2 inches with isolated higher amounts up to 4 inches
across western PR, to 2 to 4 inches along the south and east
portions of PR and the USVI, with isolated higher amounts up to 6
inches.

Please note that we encourage everyone in Puerto Rico and the US
Virgin Islands to stay informed about community threats to minimize
weather impacts for themselves and their families.


&&


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

The long-term forecast remains on track, with variable conditions
for mid next week and high uncertainty by the end of the forecast
period. As Hurricane Erin continues its way into the Western
Atlantic, the wind flow is expected to remain with a southerly
component, pooling tropical moisture into the region. From the
latest model guidance, Precipitable Water (PWAT) values are likely
to remain seasonal to near-above-normal (1.70 - 1.90 inches). The
likeliest scenario would be an advective pattern with showers
affecting southern Puerto Rico and the U.S. Virgin Islands in the
morning, and afternoon convection across the interior and northern
portions of Puerto Rico. Nevertheless, previous rainfall activity
due to Hurricane Erin and saturated soils may enhance the flooding
risk across the area, particularly the interior and northern
portions of Puerto Rico. The flooding risk will remain limited to
elevated for the aforementioned areas, with a low chance of isolated
flash flooding.

The surface high pressure over the Central Atlantic should migrate
westward, promoting SE winds through Thursday. Global models
continue suggesting the arrival of an upper-level low by Wednesday,
remaining south of the CWA. The presence of this feature might
increase instability across the area, but a drier air mass filtering
into the region is likely. Due to the combination of diurnal
heating, local effects, and available low-level moisture, afternoon
convection could bring showers and isolated thunderstorms mainly
over western Puerto Rico. Rainfall accumulations are likely to
enhance ponding of water over roadways, urban areas, and poorly
drained areas, with a low chance of urban flooding.

As mentioned in the previous discussion, there was high variability
between the deterministic guidance of the GFS and the ECMWF due to
the potential of another disturbance, likely to become a tropical
cyclone, approaching the CWA. The latest guidance indicates an
increase in PWAT values to above-normal levels (mean around 2.0 -
2.2 inches), but there’s still high variability due to a lack of
consensus among models. Hence, citizens and visitors should continue
monitoring Hurricane Erin and wait a few days for models to reach an
agreement.

Due to a southerly component in the wind flow, warmer than normal
temperatures, and available moisture, heat indexes are very likely
to exceed 100 degrees Fahrenheit, and even meet Heat Advisory
Criteria. Hence, the heat risk will remain limited to elevated for
the urban and coastal areas of Puerto Rico and the U.S. Virgin
Islands, with a medium chance of elevated to significant risk on
Wednesday.


&&

.AVIATION...

(06Z TAFs)

SHRA/TSRA associated to Erin's external rainbands will gradually
increase in a N/NNE wind flow throughout the day. Brief MVFR to IFR
conds will remain possible, especially btwn 16/14-22z, across the
USVI and northern PR terminals. NNE-N winds should prevail btw 15-20
kt with gusts up to 40 kt. Winds will slowly shift from the WS-S-SSW
by late tonight. Gusts will be more prevalent within SHRA/TSRA.


&&


.MARINE...

The external bands of Erin, producing squally weather, will continue
moving across the local waters and passages. Based on the National
Hurricane Center track forecast, Erin should move off to the
northeast away from Puerto Rico and the U.S. Virgin Islands into the
Western Atlantic on Sunday. Erin is expected to produce hazardous
swell action that will impact the Atlantic and Caribbean passages
from Saturday evening through at least early next week. Mariners and
visitors are urged to closely monitor the evolution of Erin.


&&


.BEACH FORECAST...

Swell action from Erin will result in large breaking waves, creating
dangerous swimming conditions and potential minor beach erosion,
particularly along northern and eastern exposed beaches. As a
result, High Rip Current Risk and High Surf Advisories will be in
effect from 8 AM this morning through at least late Sunday night. In
addition, outer bands from Erin will bring periods of heavy showers,
frequent lightning, and gusty winds, making outdoor activities
potentially hazardous.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
326 AM AST Wed Aug 20 2025

.KEY MESSAGES...

* Another very hot day for Puerto Rico and the Virgin Islands.
Heat indices above 108 degrees are expected across most of the
territories.

* Saharan dust will increase in concentration today, first
reaching the Virgin Islands, and then spreading into Puerto
Rico. These concentrations will maintain hazy skies through
Thursday.

* Marine conditions will deteriorate by the end of the week as a
northerly swell arrives. Beaches will be hazardous along the
northern and western coast of Puerto Rico, as well as for St.
Thomas and St. John.

&&

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

Calm and quiet weather conditions prevailed overnight across Puerto
Rico and the U.S. Virgin Islands. Doppler radar observed just few
passing showers moving from the Caribbean waters into portions of
southern Puerto Rico, leaving minimal accumulations. Minimum
temperatures were seen in the range from the upper 70s to low 80s in
the lower elevations, to the low 70s in the mountains. These warm
minimum temperatures are expected to persist for the next few days
under a southeasterly wind flow.

A Saharan Air Layer (SAL) with moderate to locally high
concentrations of Saharan dust will continue to filter into the area
through at least early Thursday morning. The peak of the event is
expected a by this afternoon into the evening hours. Therefore, hazy
skies, reduced visibilities and deteriorated air quality are
anticipated throughout the day across the islands. Under the
aforementioned pattern, the shower activity will remain limited
across the islands. Nonetheless, afternoon convective activity is
still possible each day over portions of central and northwestern
Puerto Rico due to southeasterly winds, daytime heating and local
effects.

Hot temperatures will continue across Puerto Rico and the U.S.
Virgin Islands. The combination of southeasterly winds and
sufficient moisture will result in high temperatures and high heat
indices through next week. Once again, a Extreme Heat Warning has
been issued from 9 AM to 5 PM AST for the eastern interior and the
lower elevations of Puerto Rico. A Heat Advisory is also in effect
for Culebra, Vieques and the U.S. Virgin Islands from 9 AM to 5 PM
AST. Residents and visitors should plan accordingly if planning to
do outdoor activities under sun exposure for a prolonged time.

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

The latest guidance continue to suggest that the strong tropical
wave monitored by the National Hurricane Center should move to the
northeast of the local islands on Saturday. This wave will shift
the winds from the north, which plenty of moisture reaching Puerto
Rico and the Virgin Islands. Showers and thunderstorms are
expected to stream into the region, maintaining and elevated risk
of flooding, and a limited risk of lightning. As the wave lifts
into the western Atlantic, the trade winds will turn southeast as
the air mass dries. Some Saharan dust will reach the island by
early in the workweek. Temperatures will warm up too, with a high
likelihood of experiencing heat that impacts those sensible to
heat, especially without effective cooling or adequate hydration.

By Tuesday, and upper level trough and a reflection in the mid
and low levels will move in. However, at the surface, moisture
will be below normal. Nevertheless, some passing showers can be
seen in the vicinity of the Virgin Islands and eastern Puerto Rico
at times too. Then, by mid-week, the surface high pressure over
the central Atlantic will cause the trade winds to be oriented
from the south-southeast. Moisture will begin to lift from
the Caribbean Sea, once again increasing the potential for showers
and thunderstorms.

&&

.AVIATION...
(06Z TAFs)

Mainly VFR conds expected across all terminals during the next 24
hrs. HZ due to moderate to locally high concentrations of Saharan
dust will continue to filter into the area today reducing VIS across
all local terminals to 6SM thru 20/23Z. Southeasterly winds will
continue to prevail btw 12-16 kt, with higher gusts and sea breeze
variations.

&&

.MARINE...
Light to moderate southeasterly winds will continue through
midweek, becoming east-northeast from Thursday onward. A strong
tropical wave is expected to approach the eastern Caribbean on
Friday, increasing thunderstorm activity in general through Saturday.
A long period northerly swell from distant Hurricane Erin will
arrive late Friday and into the weekend, resulting in hazardous seas
for the Atlantic waters and passages.

&&

.BEACH FORECAST...

The rip current risk will be low to moderate today. However, by
the end of the week, a northerly swell will arrive, increasing the
risk to high for most beaches in northern Puerto Rico, and also in
the northern Virgin Islands. Dangerous breaking waves can be
expected as well for the weekend and early next week.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
349 AM AST Thu Aug 21 2025

.KEY MESSAGES...

* Another hot day is expected for Puerto Rico and the Virgin
Islands. This level of heat affects those sensitive to heat,
especially those without effective cooling or adequate
hydration.

* A strong tropical wave will increase the potential for showers
and thunderstorms late Friday and on Saturday. Across the Virgin
Islands, ponding of water in roads is anticipated with isolated
urban flooding. For Puerto Rico, urban and small stream flooding
are likely along the interior and northwest, with ponding of
water elsewhere.

* A northerly swell from distant Hurricane Erin will reach the
beaches of western and northern Puerto Rico, and the beaches of
St. Thomas and St. John late Friday and this weekend. Conditions
will be hazardous for beach goers and for small boats.


&&

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

Calm weather conditions prevailed overnight across the U.S. Virgin
Islands and Puerto Rico, with just few passing showers over the
Caribbean waters and local passages. Overnight temperatures reached
from the upper 70s to the low 80s across the lower elevations.
Meanwhile, lows remained in the low 70s along the higher elevations.

For today, a Saharan Air Layer (SAL) will continue to bring moderate
to locally high concetrations of Saharan dust into the islands.
Therefore, hazy skies, reduced visibilities and poor air quality
will continue to prevail today. A drier airmass with precipitable
water values (PWAT) below-than-normal (1.05 to 1.30 inches) will
continue to filter into the region today, limiting the development
of showers and thunderstorms through at least Friday.

From Friday onward, we will be transitioning from a dry and stable
environment into a much wetter and humid pattern due to the approach
of a vigorous tropical wave into the region. This tropical wave is
currently being monitored by the National Hurricane Center (NHC).
According to the latest forecast, this wave has a low formation
chance (30%) in the next 48 hours and a high formation chance (70%)
in the next seven days.

The moisture field associated with this wave will reach the islands
by Friday afternoon and it is expected to persist through early
Sunday. The latest model guidances suggest PWAT values up to 2.20
inches on Saturday, enhancing the potential to observe showers and
thunderstorms across the region. By Saturday morning, the U.S.
Virgin Islands will expect showers and isolated thunderstorms across
the area. Later in the afternoon, the activity will be focused over
the interior and norwestern portions of Puerto Rico. At this time,
residents and visitors are advised to continue monitoring the latest
weather updates as we move into the weekend as some of these showers
and thunderstorms could potentially lead to flooding.

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

As the tropical disturbance monitored by the National Hurricane
Center lifts well north of the islands, the trade winds will
remain from the southeast. At the upper level, a trough will
approach from the north. Even though the islands will not be in
the most favorable position of the trough, temperatures at mid
levels will cool down, which, along with diurnal heating, should
allow for the development of thunderstorms across the interior and
northwestern Puerto Rico. At the low levels, drier air will filter
in, possibly with some Saharan dust too. This dry air will
maintain mostly fair weather for the Virgin Islands, although a
few passing showers cannot be ruled out.

Early in the workweek, most moisture will be staying close to the
surface, while the upper level trough remains in the vicinity of
the islands. This period will not have too much rain, except for
the usual convection in western Puerto Rico during the afternoon
hours. By mid-week, the surface high over the central Atlantic,
and a long wave polar trough near the eastern coast of the United
States will make the winds to shift from the south-southeast. This
will lift moisture from the Caribbean into the islands. With a
southerly wind flow, we should expected higher than normal
temperatures, and also an increase in showers and thunderstorms.


&&

.AVIATION...
(06Z TAFs)

VFR conds expected across all terminals throughout the fcst period.
Calm wx with hazy skies due to moderate to locally high
concentrations of Saharan dust will prevail today, reducing VIS
across the local terminals. ESE winds will continue to prevail at 10-
15 kt, with higher gusts and sea breeze variations thru 21/23Z.

&&

.MARINE...
Light to moderate southeasterly winds will continue through midweek,
becoming east-northeast from Thursday onward. A strong tropical wave
is expected to approach the eastern Caribbean on Friday, increasing
thunderstorm activity in general through Saturday. A long period
northerly swell from distant Hurricane Erin will arrive late Friday
night and into the weekend, resulting in hazardous seas for the
Atlantic waters and passages.

&&

.BEACH FORECAST...
Moderate rip current risk will persist today and tomorrow across
the islands. Thunderstorms may develop in the afternoon along
western Puerto Rico. This storms could produce dangerous lightning
strikes, so be ready to seek shelter if you hear thunder.

Conditions will deteriorate by the weekend and early next week. A
northerly swell will arrive across the beaches of northern and
western Puerto Rico, and across Culebra, St. Thomas, St. John and
St. Croix as well. This will increase the risk of rip currents to
high, while dangerous breaking waves may develop too.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
443 AM AST Fri Aug 22 2025

.KEY MESSAGES...

* A Heat Advisory is in effect for 58 municipalities across Puerto
Rico today. There is limited heat risk extending to Vieques,
Culebra, and the US Virgin Islands.

* A vigorous tropical wave (Invest 90L) will approach the region
today, increasing moisture and the potential for showers and
thunderstorm development across the islands.

* For Puerto Rico, periods of showers and thunderstorms may cause
localized urban and small stream flooding, particularly across
northwestern, north central, and eastern Puerto Rico.

* For the U.S. Virgin Islands, passing showers and thunderstorms may
result in ponding of water on roads and isolated urban flooding.

* A northerly swell from distant Hurricane Erin will arrive later
today into the weekend, producing hazardous marine conditions,
dangerous rip currents, and the potential for localized beach
erosion, especially along north- and northwest-facing beaches.

&&

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

Overnight conditions were generally fair and quiet. Doppler radar
and satellite imagery detected isolated to scattered showers and mid-
to upper-level clouds across the region. Overnight lows ranged from
80–83°F across northeastern Puerto Rico, Vieques, Culebra, and the
US Virgin Islands, while higher elevations in the Cordillera Central
cooled to the 60s. With the approach of a tropical wave (Invest
99L), the low-level wind flow shifted from the northeast, although
winds over land remained light to calm and variable.

This morning, a weak mid-level ridge, lingering Saharan dust, and
pockets of drier air will dominate. Attention then turns to Invest
99L, which has a high probability of tropical cyclone formation
according to the 2 AM AST Tropical Weather Outlook. A tropical
depression is likely to form as the system tracks northwest and then
north, well northeast of the local islands. No direct impacts are
expected for Puerto Rico or the US Virgin Islands. However, 99L is
expected to influence local weather through the weekend. By Sunday,
as the system lifts north, a mid-level ridge will strengthen,
introducing drier air and a trade wind inversion.

Today will begin mostly quiet with hazy skies and intervals of
sunshine. As moisture from 90L spreads across the region, shower
and thunderstorm activity will increase. The risk of excessive
rainfall and lightning will rise this morning across the US Virgin
Islands, then expand into Vieques, Culebra, and eastern Puerto
Rico early this afternoon, reaching much of the island later in
the day. With east-northeasterly steering, the most intense
afternoon storms are expected across southern and southwestern
Puerto Rico, where urban and small stream flooding is likely and
localized flash flooding is possible. These hazards will persist
into tonight and Saturday as abundant tropical moisture persists
across the region, while precipitable water values increase to
2.2–2.3 inches, well above normal for this time of year. The focus
of activity will shift from the USVI and eastern Puerto Rico
tonight and Saturday morning to the interior and northern parts of
Puerto Rico on Saturday afternoon as winds veer east-southeast.
By Saturday night into Sunday, as 99L moves away, generally fair,
warm, and hazy conditions are expected to return.

While rainfall and flooding remain the primary concern through
Saturday, excessive heat will continue to pose risks each day.
Despite expected rain and breezy northeasterly winds, a Heat
Advisory is in effect for 58 municipalities across Puerto Rico
today, primarily in urban and coastal areas, with a limited heat
risk extending to Vieques, Culebra, and the US Virgin Islands.
Lightning hazards will remain a daily threat. By Sunday, expect
stronger easterly trade winds and moderate Saharan dust, reducing
visibility and air quality.

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

Weather conditions will start to improve next week, as moisture
associated with the tropical wave (Invest 90L) monitored by the
National Hurricane Center (NHC) continues to move north and away
from the region. The forecast continues on track with the
positioning of an upper-level trough north of the area by Monday,
however, the islands will not be under the most favorable side of
the trough. At the low levels, a drier air mass will filter into the
area along with a Saharan Air Layer (SAL) with low to moderate
concetrations of Saharan dust. Given the expected scenario, hazy
skies, reduced visibilities, poor air quality and limited showers
are anticipated through at least Tuesday. However, late afternoon
convective activity with showers and few isolated thunderstorms are
possible across the western municipalities of Puerto Rico each
afternoon.

By mid-week, winds will shift from the south southeast in response
to a strong surface high pressure in the central Atlantic and a long
wave polar trough exiting the eastern coast of the United States.
This will lift moisture associated with a tropical wave (Invest
99L) from the Caribbean Sea. Under this pattern, an increase in
showers are anticipated across Puerto Rico and the U.S. Virgin
Islands through the end of the workweek. The 925 mb temperatures
will remain above-normal climatological values for most of the
period. Highs will continue to reach the upper 80s to low 90s each
day along the coastal and urban areas of the islands. Heat
indices will rise up to the mid to upper 100s, due to the
available moisture and southerly winds. Residents and visitors are
advised to monitor the weather updates and plan accordingly if
having outdoor activities under sun exposure.

&&

.AVIATION...
(06Z TAFs)

VFR conditions will prevail until SHRA/TSRA associated with a
tropical wave develops, briefly reducing conditions to MVFR or IFR.
These impacts are most likely after 22/14Z across USVI terminals,
after 22/16Z at TJSJ, after 22/18Z at TJPS, and after 22/22Z at
TJBQ. Light and variable winds will increase to 10–15 kt with
occasional higher gusts after 22/13Z, then diminish to 8–12 kt after
22/22Z.

&&

.MARINE...

East-northeast to northeast winds will prevail across the islands
today. A strong tropical wave is expected to approach the northeastern
Caribbean today, increasing showers and thunderstorm activity across
the region through early Sunday. A long period northerly swell from
distant Hurricane Erin will arrive as early as this afternoon, resulting
in hazardous seas for the Atlantic waters and passages through early
next week.

&&

.BEACH FORECAST...

A high rip current risk is in effect for the north and east facing
beaches of Puerto Rico through at least Saturday night. However,
as the weekend progresses other beaches of Puerto Rico and the
US Virgin Islands will move from a moderate to a high risk due to
the arrival of a northerly swell associated with distant
Hurricane Erin located over the northern Atlantic. Large breaking
waves of 7 to 10 feet are expected from Saturday into early next
week, resulting in dangerous swimming conditions, life threatening
rip currents, and the potential for localized beach erosion.

Thunderstorms may develop this afternoon along southwestern
Puerto Rico, producing dangerous lightning strikes; be prepared to
seek shelter if thunder is heard. The frequency of showers and
thunderstorms will increase as a vigorous tropical wave (Invest
90L) approaches the area from today into late Saturday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
352 AM AST Sat Aug 23 2025

.KEY MESSAGES...

* Abundant tropical moisture from a passing tropical wave and a
approaching trough will result in showers and thunderstorms
across the islands. This activity may result in localized
flooding and frequent lightning.

* Marine conditions will continue to deteriorate today as swells
from distant former Tropical Cyclone Erin reaches the region,
promoting life- threatening rip currents, rough surf conditions,
and Small Craft Advisory conditions through early next week.

* Weather conditions will improve from Sunday onward with the
arrival of a drier airmass and a Saharan Air Layer. Limited
showers, hazy skies and reduced visibilities are expected
through mid-week.

* For the U.S. Virgin Islands, passing showers and isolated
thunderstorms are possible today, particularly during the
morning hours. Therefore, there is a limited risk of heat,
excessive rainfall and lightning today.


&&

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

Overnight, a tropical wave brought thunderstorms and cloudiness
mainly offshore, leaving minimal rainfall over land. Coastal low
temperatures stayed in the low 80s, likely a reflection of warmer-
than-normal sea surface temperatures (85–86°F) in the region, and
winds remained light and variable.

Hazardous weather is expected today across Puerto Rico and the US
Virgin Islands as abundant tropical moisture from a passing tropical
wave combines with favorable upper-level conditions from an
approaching trough. Precipitable water values will peak near 2.2
inches, while mid-level temperatures drop below -7°C, creating a
highly conducive environment for showers and thunderstorms. Activity
will continue this morning over the USVI, Vieques, and southeastern
Puerto Rico, followed by a more intense round later today, mainly
across the interior and northern Puerto Rico, including the San Juan
metro area. Southeasterly winds will steer storms capable of
producing heavy rainfall, frequent lightning, and strong wind gusts.
The most significant risk is expected in northwestern Puerto Rico,
where urban and small-stream flooding is likely, and localized flash
flooding is possible.

Conditions will change significantly from tonight into early next
week as a mid-level ridge builds and both systems move away,
bringing much drier, more stable, and sunnier weather. Moderate to
fresh easterly trade winds will develop, transporting a Saharan Air
Layer across the region. As a result, precipitable water values will
fall well below normal, mid-level temperatures will warm, and a
trade wind cap will form. These factors will lead to limited shower
activity, hazier skies, reduced visibility, and poorer air quality.

For today, the primary weather concerns will be flooding, lightning,
and excessive heat. In fact, a Heat Advisory is in effect for 58
municipalities in the urban and coastal areas of Puerto Rico, with a
limited heat risk for Vieques, Culebra, and the USVI. Looking ahead
to Sunday, the risks of heat and localized lightning will persist,
while a risk of strong, non-thunderstorm winds will develop along
exposed coastal areas. By Monday, the weather will further
stabilize, with the primary concerns narrowing to just the
persistent heat and the coastal wind risk.


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

A dry weather pattern is expected for most of the long-term period
with the arrival of drier airmass and a Saharan Air Layer into the
region with moderate concetrations of Saharan dust. From Tuesday
into Wednesday a tropical wave is expected to pass south of the
area, enhancing the potential for shower development across the
local Caribbean waters and western Puerto Rico.

A strong surface high pressure in the central Atlantic will promote
easterly winds through mid-week. Then winds will shift from the
south-southeast in response to a long wave polar trough exiting
the US east coast. From Wednesday into the end of the week,
tropical moisture will be lifted from the warm Caribbean waters.
The latest precipitable water guidance has values of 1.60 to 1.70
inches, suggesting the potential for typical summer showers and
isolated thunderstorms across the region, in particular over the
northern and northwestern municipalities of Puerto Rico. During
this period, the U.S. Virgin Islands can expect mainly fair
weather condition and passing showers from time to time.

Hot temperatures are expected each day across Puerto Rico and the
U.S. Virgin Islands. Above-than-normal temperatures will persist
with highs in the upper 80s to low 90s along the coastal and urban
areas of the islands, to the low 80s in the higher elevations.
Residents and visitors are advised to monitor the weather updates
and plan accordingly if having outdoor activities under sun
exposure this weekend.

&&

.AVIATION...
(06Z TAFs)

VFR conditions will likely give way to MVFR, and briefly to IFR, as
SHRA/TSRA associated with a passing tropical wave moved inland this
morning and develop over land later this afternoon. For PR
terminals, these impacts are possible throughout the entire forecast
period, while the threat will continue through 23/23Z for USVI
terminals. Light and variable winds increasing to 10-15 knots with
occasional stronger gusts after 23/13Z, before diminishing again
after 23/22Z.

&&

.MARINE...

A tropical wave moving south of the area and a will promote showers
and thunderstorms today, mainly across the Caribbean waters and
local passages under a east southeast wind flow. A long period
northerly swell from distant Hurricane Erin will spread across the
islands from now onward, resulting in hazardous seas for the Atlantic
waters and Caribbean passages through early next week.

&&

.BEACH FORECAST...

Long period swells from distant former Tropical Cyclone Erin will
gradually fill across the Atlantic coastlines of the islands for
the next few days. This will promote life-threatening rip currents
and rough surf conditions across the northern exposed beaches of
the islands through Tuesday.

A High Rip Current Risk is in effect for the northern, eastern and
western beaches of PR, Culebra and the northern U.S. Virgin
Islands. A High Surf Advisory is possible for Sunday, or later
today if conditions warrant.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
457 AM AST Sun Aug 24 2025

.KEY MESSAGES...

* The heat threat will continue today, with Extreme Heat Warnings in
effect for Puerto Rico’s coastal and urban areas, and Heat
Advisories for Vieques, Culebra, and the U.S. Virgin Islands.
Dangerous heat indices are expected; stay hydrated, avoid
prolonged sun exposure, and check on vulnerable individuals.

* Long-period northerly swells will maintain hazardous marine
conditions, high rip current risks, and large breaking waves
through early this week. High Surf Advisories and High Rip Current
Risk Statements remain in effect for Puerto Rico and the U.S.
Virgin Islands.

* Hazy skies and poor air quality from Saharan dust will prevail
today through at least early Tuesday. Isolated strong
thunderstorms may develop this afternoon across western Puerto
Rico, with localized flooding, lightning, and gusty winds possible.

* For the U.S. Virgin Islands, hot and hazy conditions will
prevail, with a Heat Advisory in effect.

&&

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

Overnight conditions remained mainly calm, with only isolated
showers detected over regional waters and no rainfall reported on
land. Winds were light and variable, allowing for possible patchy
fog across interior valleys. Temperatures stayed exceptionally warm,
with overnight lows in the low 80s across coastal Puerto Rico,
Vieques, Culebra, and the US Virgin Islands, driven by sea surface
temperatures of 85–87°F.

Today, the weather is expected to continue stabilizing as an upper-
level trough departs and a ridge of high pressure builds in.
However, lingering tropical moisture, Saharan dust, warm seas, and
an east-southeasterly breeze will continue to dominate the
conditions. These factors will bring intense heat, prompting an
Extreme Heat Warning for Puerto Rico’s coastal and urban areas, as
well as a Heat Advisory for Vieques, Culebra, and the US Virgin
Islands. Hazy skies, poor air quality, and breezy conditions are
also expected along exposed coasts. Isolated strong thunderstorms
may develop this afternoon over western Puerto Rico, producing
localized flooding, lightning, and gusty winds.

Tonight will remain mostly quiet but warm and hazy, setting the
stage for a very hot, dry, and stable Monday. Heat alerts will
likely continue, and air quality may worsen due to moderate to high
levels of Saharan dust. By Monday night into Tuesday, a tropical
wave (AL99) passing south of the area will slightly increase
moisture, raising the chance for localized afternoon showers and a
few thunderstorms. Winds will strengthen from the east before easing
later in the day. Heat and haze are expected to persist through
Tuesday.

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

A seasonal weather pattern is expected in the long-term forecast.
Low-level moisture content will fluctuate from below-normal to near-
normal levels, as patches of moisture embedded in the trades stream
across from time to time. Dynamics aloft will remain marginal for
the most part, with weak ridging alternating with periods of
troughiness throughout the forecast period. As a result, 500 mb
temperatures will remain near climatological normals, while 700–500
mb lapse rates could be slightly steeper toward the end of the
period.

At the surface, a high-pressure system over the central Atlantic
will promote easterly winds during the first part of the long-term
period, gradually shifting east-southeasterly toward the weekend.
This overall setup will maintain a seasonal weather pattern, with
occasional passing showers moving across windward coastal areas
during the night and morning hours. In the afternoons, showers and
thunderstorms are expected to develop over interior and
western/northwestern Puerto Rico as sufficient instability and low-
level moisture combine with diurnal heating and orographic lift.
Meanwhile, the southern coastal hills of Puerto Rico will likely
observe limited shower activity. In contrast, interior and
western/northwestern Puerto Rico may experience localized to
elevated flooding threats each afternoon, mainly resulting in urban
and small stream flooding, particularly in flood-prone areas.

In addition, the southeasterly winds will promote warm air advection
across the region. Model guidance suggests 925 mb temperatures and
1000–850 mb thickness values will remain well above normal through
the weekend. This pattern will support hot surface temperatures, and
when combined with sufficient low-level moisture, could result in
sweltering heat indices and an elevated heat threat for the period.
As a result, the issuance of Extreme Heat Warnings or Heat
Advisories cannot be ruled out. Residents and visitors are advised
to stay hydrated, avoid prolonged exposure to the sun during peak
hours, take frequent breaks if working outdoors, and check on
vulnerable populations such as the elderly, children, and those with
chronic health conditions.


&&

.AVIATION...
(06Z TAFs)

VFR conditions will prevail across all local terminals; however,
afternoon SHRA/TSRA may approach TJBQ and TJPS, particularly between
24/17-23Z, bringing a slight chance of MVFR conditions. Winds will
be light and variable early, increasing to 10-15 knots with
occasional stronger gusts after 24/13Z, before diminishing again to
5-10 knots after 24/22Z. Additionally, the arrival of a Saharan Air
Layer will result in reduced visibility throughout the day.

&&

.MARINE...
A long period northerly swell will continue to spread across the
islands through early this week, resulting in hazardous seas for the
Atlantic waters and local passages. Another tropical wave will move
into the Caribbean by late tonight, moving mainly to the south of the
USVI and PR through Tuesday. This will result in moderate to fresh
easterly winds and choppy to rough seas, particularly across the
Caribbean waters.

&&

.BEACH FORECAST...

Offshore buoys 41046 and 41043 continue to indicate a long-period
northerly swell that will persist across the Atlantic waters today
through early this week. Nearshore buoys are already detecting
swells with periods of 12–14 seconds. As a result, hazardous beach
conditions are expected, including a high risk of rip currents and
large breaking waves that could create dangerous swimming conditions
and minor beach erosion.

Accordingly, High Surf Advisories and High Rip Current Risk
Statements are in effect for Puerto Rico and the U.S. Virgin
Islands. For more details, please refer to CFWSJU and SRFSJU.
Beachgoers are strongly advised to exercise caution, avoid swimming
in high-risk beaches, and heed the advice of local lifeguards and
authorities.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
508 AM AST Mon Aug 25 2025

.KEY MESSAGES...

* Long-period northerly swells will peak today, maintaining
hazardous seas, high rip current risks, and dangerous surf
conditions. Hazardous marine and coastal conditions will persist
through at least Tuesday. High Surf Advisories, High Rip Current
Risk Statements, and Coastal Flood Advisories are in effect.

* Heat Advisories are in effect for Puerto Rico. While the heat
threat is lower than yesterday, dangerous heat indices are still
expected. Stay hydrated, limit prolonged outdoor exposure, and
check on vulnerable individuals.

* Saharan dust concentrations will gradually diminish today but will
remain at moderate to slightly high levels. Impacts on air quality
and visibility will persist through the day.

* For the U.S. Virgin Islands, Heat Advisories are in effect, with
hot and humid conditions expected alongside hazy skies from
Saharan dust.

&&

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

Overnight conditions remained mainly calm, with only isolated
showers detected over regional waters and no rainfall reported on
land. Winds were light and variable, allowing for possible patchy
fog across interior valleys. Temperatures stayed exceptionally warm,
with overnight lows in the low 80s across coastal Puerto Rico,
Vieques, Culebra, and the US Virgin Islands, driven by sea surface
temperatures of 85–87°F.

Today, the weather is expected to continue stabilizing as an upper-
level trough departs and a ridge of high pressure builds in.
However, lingering tropical moisture, Saharan dust, warm seas, and
an east-southeasterly breeze will continue to dominate the
conditions. These factors will bring intense heat, prompting an
Extreme Heat Warning for Puerto Rico’s coastal and urban areas, as
well as a Heat Advisory for Vieques, Culebra, and the US Virgin
Islands. Hazy skies, poor air quality, and breezy conditions are
also expected along exposed coasts. Isolated strong thunderstorms
may develop this afternoon over western Puerto Rico, producing
localized flooding, lightning, and gusty winds.

Tonight will remain mostly quiet but warm and hazy, setting the
stage for a very hot, dry, and stable Monday. Heat alerts will
likely continue, and air quality may worsen due to moderate to high
levels of Saharan dust. By Monday night into Tuesday, a tropical
wave (AL99) passing south of the area will slightly increase
moisture, raising the chance for localized afternoon showers and a
few thunderstorms. Winds will strengthen from the east before easing
later in the day. Heat and haze are expected to persist through
Tuesday.

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

The latest model guidance indicates a slightly wetter scenario for
the beginning of the long-term period. Columnar moisture is now
forecast to increase, with precipitable water values near or above
normal levels and 700-500 mb relative humidity well above normal for
this time of year. This enhanced moisture is tied to a weak, deep-
layered trough expected to cross the region from midweek through the
end of the workweek. As this feature exits the area, low-level
southerly flow will advect additional tropical moisture into the
northeastern Caribbean, reinforcing the wetter pattern.

Upper-level dynamics will also become more favorable, as 500 mb
temperatures are expected to drop into the -6.5 to -7 C range,
values within the lower quartile of climatological normals and
therefore supportive of convective development. The Galvez-Davison
Index reflects this by showing an increasing potential and spatial
coverage shower and thunderstorm activity, particularly on
Friday, when scattered shallow convection and isolated
thunderstorms appear more likely. As a result, the risk for
localized urban and small stream flooding will be elevated both
Thursday and Friday, with the northern half of Puerto Rico most
prone due to the persistent southerly wind flow.

For the remainder of the long-term period, conditions are expected
to transition back toward a more seasonal pattern. Sufficient low-
level moisture combined with marginal instability aloft should
sustain typical diurnal activity, with passing showers over windward
coastal areas during the nighttime and morning hours, and locally
induced afternoon convection across the interior and
western/northwestern Puerto Rico, aided by sea breeze convergence.

In addition, the prevailing southerly winds will promote significant
heat concerns toward the end of the workweek and into the weekend.
With 925 mb temperatures and 1000-850 mb thickness values remaining
above normal, hot surface temperatures combined with adequate low-
level moisture may result in elevated to significant heat stress.
Therefore, the issuance of Extreme Heat Warnings cannot be ruled out.


&&

.AVIATION...
(06Z TAFs)

VFR conditions will prevail across all local terminals; however,
afternoon SHRA/TSRA may approach TJBQ and TJPS, particularly between
24/17-23Z, bringing a slight chance of MVFR conditions. Winds will
be light and variable early, increasing to 10-15 knots with
occasional stronger gusts after 24/13Z, before diminishing again to
5-10 knots after 24/22Z. Additionally, the arrival of a Saharan Air
Layer will result in reduced visibility throughout the day.

&&

.MARINE...

A long period northerly swell will continue to spread across the
islands through at least Tuesday, resulting in hazardous seas for
the Atlantic waters and local passages. Another tropical wave will
continue to move over the Caribbean waters today, moving mainly to
the south of the USVI and PR through Tuesday. This will result in
moderate to fresh easterly winds and choppy to rough seas,
particularly across the Caribbean waters.

&&

.BEACH FORECAST...

Offshore buoy 41043 continues to report seas between 6–8 feet with
swell periods of 12–14 seconds, with a few observations even
reaching 16 seconds overnight. This long-period northerly swell will
continue to impact the northern coasts today, now expected to
promote larger breaking waves between 10–14 feet, with isolated
higher sets possible.

As a result, hazardous beach conditions will persist, including
dangerous swimming conditions, strong rip currents, and minor beach
erosion. Additionally, the stronger swell energy and larger breaking
waves could cause localized coastal flooding along portions of the
northern coastline of Puerto Rico, prompting the issuance of a
Coastal Flood Advisory. Yesterday, these hazardous conditions have
already led to multiple water-related incidents across local
beaches, underscoring the seriousness of the threat.

High Surf Advisories and High Rip Current Risk Statements remain in
effect for Puerto Rico and the U.S. Virgin Islands, while a Coastal
Flood Advisory is in effect for the northern coastline of Puerto
Rico. For more details, please refer to CFWSJU and SRFSJU.
Beachgoers are strongly urged to exercise extreme caution, avoid
swimming in high-risk areas, and heed the guidance of local
lifeguards and authorities.

[cycloneye]

Area Forecast Discussion...DELAYED
National Weather Service San Juan PR
518 AM AST Tue Aug 26 2025

.KEY MESSAGES...

* Northerly swells and winds continue to subside, but remain
sufficient to maintain hazardous marine and beach conditions.
High Surf Advisories, High Rip Current Risk Statements, and
Small Craft Advisories remain in effect today.

* A Heat Advisory is in effect for Puerto Rico today. The heat
threat will increase toward the end of the workweek as
southeasterly winds bring hotter temperatures and combine with
tropical moisture. Extreme Heat Warnings and/or additional Heat
Advisories are likely.

* For the U.S. Virgin Islands, the heat threat is limited today
but is expected to increase by the end of the workweek.
Hazardous marine and beach conditions will persist today.

&&

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

Overnight conditions were mainly calm, with isolated to scattered
showers moving across northern and eastern Puerto Rico, producing
localized rainfall totals of up to half an inch. The overall wind
flow was from the east to east-northeast, but light and variable
conditions near the surface favored the development of patchy fog
across interior valleys. Temperatures remained warm, with lows in
the low to mid-80s across coastal Puerto Rico, Vieques, Culebra, and
the US Virgin Islands, supported by elevated sea surface
temperatures of 85–87°F.

Moisture levels will remain near normal today due to lingering
moisture from departing tropical wave (AL99). As the system drifts
farther away, winds will gradually ease from fresh to moderate,
though wind hazards are still possible along exposed coastal areas
of Puerto Rico. Excessive heat remains a concern today, with a Heat
Advisory in effect for coastal and urban areas of Puerto Rico, and
limited heat risk for Vieques, Culebra, and the US Virgin Islands.
Exceptional warmth in the mid-levels will keep the atmosphere
somewhat hostile. However, the combination of intense heat and
available moisture will still support scattered to locally numerous
afternoon showers and isolated thunderstorms, mainly across western
Puerto Rico in the afternoon. These storms may move quickly under
the lingering steering flow but could still produce localized
flooding, lightning, and gusty winds across the far western portions
of the island. Additionally, locally drier and breezier conditions
may pose brief fire danger risks, particularly in fire-prone areas
of southern Puerto Rico, Vieques, and Saint Croix.

Tonight through Wednesday, winds will ease to a gentle to moderate
breeze, while moisture fluctuates between drier patches and brief
surges of values well above normal. As a mid- to upper-level trough
approaches, mid-level temperatures will cool to near normal,
creating a more favorable setup for showers and thunderstorms. While
occasional dry air may limit activity at times, slower storm motion
will increase the risk of localized flooding, lightning, and gusty
winds, primarily across western Puerto Rico, with some activity also
expected in the northeast and local islands. By Thursday, persistent
southeasterly flow will maintain a steady increase in moisture, with
mid-level temperatures dropping well below normal by evening and a
gentle breeze further enhancing the risk of slow-moving showers and
thunderstorms. Meanwhile, the prolonged warm spell will continue,
with heat risk gradually increasing under southeasterly flow.

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

Confidence continues to increase that Friday will be the most active
day of the long-term period. A departing tropical wave, combined
with southeasterly winds and trailing moisture, will interact with
weak troughing aloft. Early in the day, skies may feature fewer
clouds, allowing for rapid surface heating. Southeasterly flow will
support very hot conditions, with 925 mb temperatures forecast to
remain well above normal, even exceeding the 99th percentile for
this time of year. These conditions will likely prompt the issuance
of Extreme Heat Warnings and/or Heat Advisories.

The intense surface heating will act as fuel for afternoon
convection. Model guidance continues to indicate favorable upper-
level dynamics, with cold air advection helping 500 mb
temperatures drop into the -6 to -8 C range, the latter near the
10th percentile of climatological values. This cooling aloft will
steepen low- to mid-level lapse rates, supporting the development
of strong convection. The most intense thunderstorm activity is
expected across the interior and western to northwestern Puerto
Rico, enhanced by sea breeze convergence and orographic lift.
Streamers from El Yunque and the smaller islands may also impact
downwind locations, including the San Juan metro area. Hazards
will include frequent lightning, gusty winds, and periods of heavy
rainfall. Urban and small stream flooding is possible, with the
potential for localized flash flooding.

From Saturday into early next week, the pattern transitions back
toward a more typical seasonal regime. Heat concerns will persist,
though not as extreme as on Friday, and additional Heat Advisories
are still likely. In terms of rainfall, near-normal moisture and
marginal instability should sustain diurnally driven shower and
thunderstorm activity. Expect passing showers over windward coastal
areas during the nighttime and morning hours, followed by afternoon
convection across the interior and western/northwestern Puerto Rico,
enhanced by sea breeze convergence.

Overall, Friday remains the focal point for significant heat and
convective hazards, while the rest of the long-term period trends
closer to a seasonal weather pattern with localized afternoon
thunderstorms and continued heat concerns.


&&

.AVIATION...
(06Z TAFs)

VFR conditions will prevail at all local terminals. However,
afternoon SHRA/TSRA could develop near TJBQ between 26/17- 23Z,
with a slight chance of brief MVFR conditions. After 26/23Z,
increasing trade wind SHRA may also affect TJSJ and the USVI
terminals. Winds will be light and variable early this morning,
becoming 15–20 kts with occasional gusts up to 24–28 kts after
26/13Z, then gradually diminishing to 6–10 kts after 26/23Z.

&&

.MARINE...

A long period northerly swell will continue to spread across the
islands through at least today, resulting in hazardous seas for the
Atlantic waters and local passages. A tropical wave will continue to
exit the area as it moves over the Caribbean waters today. This will
result in moderate to fresh easterly winds and choppy to rough seas,
particularly across the Caribbean waters. Another tropical wave will
reach the Lesser Antilles on Wednesday, moving near the local
Caribbean waters around Thursday.

&&

.BEACH FORECAST...

Observations from both nearshore and offshore buoys indicate a
gradual decrease in northerly swell energy. However, these swells
will continue to impact the northern waters today, promoting large
breaking waves and resulting in the continuation of hazardous beach
conditions. Dangerous swimming conditions and minor beach erosion
are expected to persist, although the areal coverage of these
hazardous conditions will be less than yesterday.

A High Surf Advisory remains in effect for the northern coastline of
Puerto Rico and Culebra, while a High Rip Current Risk Statement
continues for the northern beaches of Puerto Rico, Culebra, and the
U.S. Virgin Islands.

Beachgoers are strongly advised to exercise extreme caution, avoid
swimming in high-risk areas, and heed the guidance of local
lifeguards and authorities. For the latest details and updates,
please refer to the Coastal Hazards Message (CFWSJU) and the Surf
Zone Forecast (SRFSJU).

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
509 AM AST Wed Aug 27 2025

.KEY MESSAGES...

* Life-threatening rip currents will prevail through at least
this afternoon.

* Southeasterly winds and increasing moisture content will increase
the heat threat on Thursday and Friday. Extreme Heat Warnings
and/or additional Heat Advisories are likely each day.

* A mid to upper level trough will reach the area today promoting
an increase ion shower activity.

&&

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

Isolated to scattered showers moved over the waters during the
overnight hours under an easterly steering flow. A few of them were
able to become t-storms, with the strongest one moving in the
vicinity of St. Thomas & St. John. Overall, radar estimated
accumulations since midnight were observed over north-central to
eastern PR, southeastern PR, St. Croix, St. John & St. Thomas. By
4:45 AM, the highest radar estimated accumulations over Puerto Rico
were in northern San Juan (0.30 in) and the highest radar estimated
accumulations over the USVI were over south-central St. John (0.2
in). Reported minimum temperatures were in the 60s to low 70s over
interior Puerto Rico (patchy fog was also detected by satellite over
interior Puerto Rico), and in the upper 70s to low 80s over lower
elevations of the islands.

Satellite derived precipitable water (PWAT) values indicate a patch
of moisture currently over St. Thomas & St. John with values around
2 inches, normal to above normal for this time of the year. This
patch of moisture will reach eastern Puerto Rico to start the
morning hours, leading to passing shower activity. Steering flow
however, will veer to become more east-southeasterly today (while
also becoming up to moderate) and through at least early Friday. A
limited to elevated heat risk will be present today, prompting the
issuance of a Heat Advisory. 925 mb temperatures are expected to be
above normal for this time of the year. This diurnal heating,
orographic effects and sea breeze convergence will once again
promote afternoon shower and t-storm activity, mainly over interior
to W-NW PR, as well as downwind of El Yunque (towards the metro
area) and the local islands. A mid to upper level trough will also
approach the area today, further promoting shower and thunderstorm
development. With decreased wind speeds, storm motion will also
decrease, further prompting a limited to elevated flooding risk.

On Thursday, southeasterly flow will continue, this will steer
moisture from a tropical wave, currently near 60W, towards the
islands. PWAT values are forecast to be around 2 inches for the
islands throughout most of the period. This constant moisture being
steered into the islands will also be accompanied by shower activity
during the overnight to morning hours. This increased moisture and
decreasing southeasterly flow will promote an elevated to possibly
significant heat risk over the islands. This diurnal heating, sea
breeze convergence, local effects, and near normal 500 mb
temperatures, will continue to promote afternoon convection on
Thursday and Friday over similar areas as Wednesday. The latest
Galvez-Davison Index (GDI) values indicate up to 30 to 40 GDI during
the afternoon hours on Wednesday and Thursday and up to 45 GDI on
Friday. Although steering flow is forecast to back and gradually
become more east-southeasterly to easterly on Friday, 925mb
temperature forecasts continue to indicate, just like on Thursday,
temperatures at 2 standard deviations above normal. This indicates
an elevated to possibly significant heat risk once again to end the
week. Elevated to significant heat risks prompt the issuance of Heat
Advisories and Extreme Heat Warnings, respectively. An elevated heat
risk affects most individuals sensitive to heat, especially those
without effective cooling and/or adequate hydration. A significant
heat risk affects anyone without effective colling and/or adequate
hydration.


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

The inherited forecast remains on track. From Saturday into early next
week, the pattern transitions back toward a more typical seasonal
weather pattern. Winds will gradually shift to a more consistent
easterly direction, carrying pockets of trade wind moisture across
the islands. Although the recent heat intensity will ease, heat
advisories remain possible throughout this period.

Moisture content is forecast to remain near climatological normals,
while only marginal instability is expected aloft. Overnight and
morning hours will favor passing trade wind showers moving in
across the U.S. Virgin Islands and the eastern half of Puerto
Rico. By the afternoon, stronger diurnal heating, sea breeze
interactions, and orographic influences will trigger additional
convection, primarily across the interior and western
municipalities of Puerto Rico. This afternoon activity could
generate brief heavy downpours, localized ponding of water, and
occasional lightning.

Through Monday and Tuesday, no significant large-scale disturbances
are anticipated, so the forecast confidence remains moderate to
high. The persistence of warm conditions and localized convective
activity will be the main themes.

Overall, the period will feature a return to a more seasonally typical
pattern of passing coastal showers at night and in the morning,
followed by scattered afternoon thunderstorms inland, with
continued but somewhat less extreme heat concerns.

&&

.AVIATION...
(06Z TAFs)

Mainly VFR conditions across the the terminals. -SHRA/SHRA will near
or reach the eastern terminals during the morning hours, while
moving mainly in the VCTY of TJPS. Winds will be light from the east
and variable, before increasing by 27/13Z to around 15 kts, with
higher gusts while also gradually veering to become more east-
southeast. Between 27/17-23Z, afternoon SHRA/TSRA will affect mainly
TJBQ and the VCTY of TJPS, convective activity form El Yunque can
also reach TJSJ at this time. Winds bcmg light and variable after
27/23Z.

&&

.MARINE...

A long period northerly swell will continue to spread across the
islands through at least today, resulting in hazardous seas for the
Atlantic waters and local passages. Another tropical wave will reach
the Lesser Antilles on Wednesday, moving near the local Caribbean
waters around Thursday.

&&

.BEACH FORECAST...

A lingering northerly swell will continue to promote life-
threatening rip currents across the north, eastern, and western
beaches of PR, Culebra, and Saint Thomas the islands through this
afternoon.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
531 AM AST Thu Aug 28 2025

.KEY MESSAGES...

* A tropical wave will continue to approach the islands increase
the moisture content through Friday.

* An Extreme Heat Warning will be in effect from 10 AM through 5
PM for the coastal and urban areas of Puerto Rico.

* A Heat Advisory will be in effect from 10 AM through 5 PM for
the US Virgin Islands, Vieques, and Culebra.

* Seas will continue to subside across the regional waters during
the next few days, and a low risk of rip currents is expected
during the weekend across all beaches of PR and the USVI.


&&

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

Radar estimated accumulations since midnight were observed over
eastern, eastern interior to north-central and southern Puerto Rico,
eastern Vieques, St. Croix and St. John. By 4:32 AM AST, the highest
radar estimated accumulations were 1.47 in over coastal Salinas and
around 1.20 in over Fajardo, Luquillo and Las Piedras. Around 0.01
inches was estimated by radar since midnight at isolated sectors of
St. John and St. Croix. Reported lows were in the mid 60s to low 70s
over interior Puerto Rico, and in the upper 70s to low 80s over
lower elevations of the islands.

Satellite derived precipitable water (PWAT) values indicate a patch
of moisture over the Atlantic Waters with values around 1.90 inches.
Moisture over the Caribbean waters from a weak tropical wave is also
present, with PWAT values around 1.90 to 2 in. Under southeasterly
steering flow, this moisture, along with showers and t-storms will
filter into our local area to start the morning hours. Steering flow
will gradually back to become more east-southeasterly during the
overnight hours into tomorrow, and possibly become more easterly on
Saturday. An elevated to significant heat risk will be present
today, prompting the issuance of a Heat Advisory (USVI, Vieques and
Culebra) and Excessive Heat Warning (lower elevation and urban areas
of PR) from 10 AM to 5 PM AST. 925 mb temperatures are expected to
be above normal (2 standard deviations) for this time of the year.
This diurnal heating, along with orographic effects, southeasterly
steering flow and sea breeze convergence will promote afternoon
shower and t-storm activity, mainly over interior to W-NW PR, N PR
as well as downwind of El Yunque and the local islands. A weak mid
to upper level trough is also present area today, further promoting
shower and thunderstorm development. Storm motion is also expected
to be relatively low, further prompting a limited to elevated
flooding risk.

On Friday, moisture from the wave will continue to filter into the
area with PWAT values around 1.90 to 2 inches through most of
Saturday. Shower activity will also be steered towards the islands
during the overnight to morning hours. Diurnal heating, sea breeze
convergence, local effects, and near to below normal 500 mb
temperatures, will continue to promote afternoon convection on
Friday, over similar areas as Thursday. More easterly flow can focus
convective activity over western PR on Saturday. 925mb temperature
forecasts continue to indicate values at 2 standard deviations above
normal each late morning to afternoon during the period. This
indicates an elevated to possibly significant heat risk once again
to end the week. Elevated to significant heat risks prompt the
issuance of Heat Advisories and Extreme Heat Warnings, respectively.
An elevated heat risk affects most individuals sensitive to heat,
especially those without effective cooling and/or adequate
hydration. A significant heat risk affects anyone without effective
cooling and/or adequate hydration.


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

From Sunday through midweek, the overall weather pattern will
resemble typical seasonal conditions. A steady easterly wind flow
will transport patches of trade wind moisture across the islands
from time to time. This will favor brief overnight and early
morning showers across the U.S. Virgin Islands and eastern Puerto
Rico, followed by afternoon convection over the interior and
western portions of Puerto Rico due to sea breeze convergence and
diurnal heating. Localized heavy downpours, occasional lightning,
and ponding of water will be possible with the afternoon activity.

By Thursday, a surface perturbation is forecast to approach the region,
enhancing available moisture and instability. This will increase
the potential for more widespread showers and thunderstorms.

Overall, the long-term forecast highlights a seasonally typical
pattern through midweek, transitioning to slightly wetter and
unstable conditions late in the period as the perturbation
approaches.

Heat advisories remain possible from Sunday through Thursday, as model
guidance indicates 925 mb temperature and humidity values ranging
from the 75th percentile to greater than two standard deviations
above normal during the period.

&&

.AVIATION...
(06Z TAFs)

Mainly VFR conditions across the the terminals. SHRA/TSRA will near
or reach TISX/TIST to start the day, and will continue to be steered
towards the islands. Winds will be light from the southeast, before
increasing by 28/13Z to around 16 kts, with higher gusts and sea
breeze variations. Between 28/17-23Z, afternoon SHRA/TSRA will
affect mainly TJBQ, convective activity form El Yunque can also
reach TJSJ at this time. Sfc winds bcmg light and variable after
28/23Z.

&&

.MARINE...

From today through Friday, the shower and isolated thunderstorm
activity could increase due to an approaching weak tropical wave near
the U.S. Virgin Islands.

&&

.BEACH FORECAST...

Moderate rip current risk along the western, northern, and
eastern Puerto Rico, and Culebra through tonight, while Saint
Croix will become low by this afternoon.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
530 AM AST Fri Aug 29 2025

.KEY MESSAGES...

* Above normal temperatures and heat indices will persist
throughout the weekend for the islands.

* lingering moisture from the recent tropical wave, combined with
the influence of a mid to upper- level trough will also help
promote afternoon showers and t-storms.

* An Extreme Heat Warning will be in effect from 10 AM through 5
PM for the coastal and urban areas of Puerto Rico. A Heat
Advisory will be in effect from 10 AM through 5 PM for the US
Virgin Islands, Vieques, and Culebra.

* A low risk of rip currents is expected today and during the
Labor Day weekend across all beaches of PR and the USVI.

&&

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

Calm conditions prevailed overnight across Puerto Rico and the US
Virgin Islands. However, a few showers with brief lightning
developed over eastern Puerto Rico, resulting in rainfall
accumulations of between 0.20 and 0.70 inches. The rest of Puerto
Rico and the US Virgin Islands remained dry. Minimum temperatures
ranged from the upper 70s to the low 80s in urban/coastal areas, and
from the upper 60s to the low 70s in mountainous/rural areas. Light
and variable winds prevailed through the night.

For today, heat concerns remain relatively high as model guidance
continues to show 925 mb temperatures running above normal. As a
result, Heat Advisories are in effect for Vieques, Culebra, and the
US Virgin Islands, while Extreme Heat Warnings have been issued for
urban and coastal areas of Puerto Rico from 10 AM to 5 PM. An
elevated heat risk (Heat Advisory) poses a concern for sensitive
individuals, particularly those lacking proper hydration or cooling.
A significant heat risk (Extreme Heat Warning) means that nearly
everyone, without adequate cooling and hydration, is vulnerable to
heat-related illness. Therefore, we urge visitors and citizens to
follow the Department of Health's recommendations to avoid being
significantly affected by the heat.

In addition to the heat, lingering moisture from the recent tropical
wave, combined with the influence of a mid to upper-level trough,
will keep precipitable water values elevated between 1.80 and 2.00
inches. Model guidance also indicates 500 mb temperatures between -6
and -8 °C, supporting instability and deep convective development.
As a result, showers and thunderstorms are expected to form during
the afternoon, mainly across northwestern Puerto Rico and possibly
the San Juan metro area. While these showers may provide brief
relief after 12 PM over the northwestern sections, conditions will
otherwise remain hot and humid.

Looking ahead to the weekend, winds are expected to shift more
easterly, with models suggesting a slight reduction in moisture,
which will lower precipitable water values to around 1.50–1.80
inches. Still, typical seasonal weather will prevail: passing
showers during the early morning hours, followed by afternoon
convection focused mainly across western Puerto Rico. Heat concerns
will persist, as models continue to show 925 mb temperatures ranging
from above normal to above two standard deviations. Combined with
periods of strong sunshine, this will sustain an elevated risk of
heat-related impacts. Conditions will be monitored closely, and
updates will be issued as necessary to keep residents and visitors
well-informed.

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

A seasonal diurnal pattern is forecast during the workweek to
start September, as patches of moisture are steered towards the
islands under east to east-southeast steering flow. Weak mid to
level troughiness can reach the area during the second half of the
workweek. Precipitable water values will be at normal values for
this time of the year, with afternoon convective activity reaching
values above 2 inches. Overnight passing showers will also
affect the eastern region. With 925 mb temperatures remaining
above normal, elevated to possibly significant, at times, heat
risk will remain during the workweek. Elevated to significant heat
risks prompt the issuance of Heat Advisories and Extreme Heat
Warnings, respectively. An elevated heat risk affects most
individuals sensitive to heat, especially those without effective
cooling and/or adequate hydration. A significant heat risk affects
anyone without effective cooling and/or adequate hydration. This
diurnal heating, along with orographic effects, east to east-
southeast steering flow and sea breeze convergence will promote
afternoon shower and t-storm activity, mainly over interior to
W-NW PR, as well as downwind of El Yunque and the local islands.
Localized heavy downpours, lightning, and flooding risks will be
possible with the afternoon activity. Per the 2 AM AST Tropical
Weather Outlook issued by the National Hurricane Center, a
tropical wave is forecast to emerge off the west coast of Africa
this Sunday and has a low (20%) formation chance through 7 days.

&&

.AVIATION...
(06Z TAFs)

VFR conditions across all TAF sites. Between 29/17-23Z, afternoon
SHRA/TSRA could prompt brief MVFR cond over TJBQ. Convective
activity from El Yunque can also reach TJSJ. SE winds will dominate
all sites, increasing in speed from 29/13Z to around 12 to 17 kts.
However, we anticipate occasional higher gusts, particularly during
the heaviest rainfall and due to variations in sea breezes. Sfc
winds will bcmg light after 23Z.

&&

.MARINE...

The trailing moisture from a past tropical wave, will promote
showers and posible isolated thunderstorms early today across the
local waters. Convective activity is forecast downwind of the islands
during the afternoon hours. Another weak tropical wave will enter
the Lesser Antilles by tomorrow, Saturday. Mariners can expect
moderate east to east- southeast winds and moderate chops across the
regional waters during the rest of this week and into early next
week.

&&

.BEACH FORECAST...

The risk of rip currents will remain low through the weekend, and
possibly extending through the next midweek. Even if the risk of
rip currents is low, 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
508 AM AST Sat Aug 30 2025

.KEY MESSAGES...

* The US Virgin Islands and Puerto Rico will observe a hot spell
throughout the rest of the Labor Day Weekend, with a moderate
to high chance of issuing an Extreme Heat Warning or Heat
Advisory each day.

* Today, an Extreme Heat Warning will be in effect from 10 AM
through 5 PM for the coastal and urban areas of Puerto Rico. A
Heat Advisory will also be in effect today from 10 AM through 5
PM for the US Virgin Islands, Vieques, and Culebra.

* A low risk of rip currents is expected today, during the rest of
the Labor Day weekend and possibly through midweek, across all
beaches of PR and the USVI.

* Strong afternoon thunderstorms will develop each day across
portions of PR and possibly downwind from the USVI.

&&

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

During the overnight hours, tranquil weather prevailed across Puerto
Rico and the U.S. Virgin Islands. However, after 2 AM, frequent
pockets of showers developed over the surrounding waters, with some
moving into the northern and northeastern municipalities of Puerto
Rico, as well as Vieques, Culebra, and the U.S. Virgin Islands.
Rainfall accumulations ranged from 0.10 to 0.40 inches. Winds
remained light, generally from the east-northeast, while
temperatures stayed in the mid-to-upper 70s along coastal areas and
in the 60s to low 70s across the mountainous areas.

As in previous days, today we anticipate a mix of sunshine and
periods of cloud cover. This will allow the ongoing hot spell to
persist across the islands. Elevated to significant heat risk levels
are forecast particularly in urban and coastal areas where Extreme
Heat Warnings are in effect for Puerto Rico from 10:00 AM to 5:00
PM. Heat Advisories are also in place for Vieques, Culebra, and the
U.S. Virgin Islands during the same time frame. These conditions
increase the likelihood of heat-related illnesses, particularly for
vulnerable populations. Residents and visitors are strongly advised
to stay well hydrated, wear light and loose-fitting clothing, avoid
strenuous outdoor activities during peak heating hours, and never
leave children or pets unattended in vehicles. By the afternoon,
showers and thunderstorms are likely to develop, mainly across the
interior, western, and southwestern sections of Puerto Rico, and
possibly over the San Juan metro area. This activity will be
supported by moisture associated with a tropical wave located to the
south of the region. Model guidance indicates precipitable water
values between 1.60 and 1.80 inches, along with mid-level
temperatures ranging from -8 to -7 degrees Celsius, which will
enhance instability. While these showers may provide brief relief,
hot and humid conditions will otherwise persist through the Labor
Day weekend. Updates will continue to be issued as necessary to
keep residents and visitors well-informed and safe during this
prolonged hot spell.

By the beginning of September, a seasonal diurnal pattern is
forecast with patches of moisture steered towards the islands and
the regular afternoon convection.

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

No major changes to the long term forecast, a seasonal diurnal
pattern is forecast during the long term period, as patches of
moisture are steered towards the islands under east to east-
southeast steering flow. Weak mid to level troughiness can reach
the area during the second half of the workweek. Precipitable
water (PWAT) values will be at normal values for this time of the
year, with afternoon convective activity reaching values above 2
inches. Current model guidance, suggest PWAT values reaching 2
inches on Saturday, when an easterly disturbance reaches the
islands. Overnight and morning passing showers will continue to
affect the eastern region. Diurnal heating, along with orographic
effects, east to east- southeast steering flow and sea breeze
convergence will promote afternoon showers and t-storm activity,
mainly over the interior to W-NW PR, as well as downwind of El
Yunque and the local islands. Localized heavy downpours,
lightning, and flooding risks will be possible with the afternoon
activity. Per the 2 AM AST Tropical Weather Outlook issued by the
National Hurricane Center, a tropical wave is forecast to emerge
off the west coast of Africa tomorrow, Sunday, and has a low
(30%) formation chance in the next 7 days. With 925 mb
temperatures remaining above normal, up to elevated to possibly
significant heat risk will remain during the workweek. Elevated to
significant heat risks prompt the issuance of Heat Advisories and
Extreme Heat Warnings, respectively. An elevated heat risk
affects most individuals sensitive to heat, especially those
without effective cooling and/or adequate hydration. A significant
heat risk affects anyone without effective cooling and/or
adequate hydration.

&&

.AVIATION...
(06Z TAFs)

All TAF sites should experience VFR conditions. However, SHRA/TSRA
associated with the afternoon convection is expected. This will
allow brief periods of MVFR cond from 30/17-23Z at TJBQ, TJPS, and
TJSJ. E winds will dominate all sites, increasing in speed from
30/13Z to around 3 to 15 kts. However, we anticipate occasional
higher gusts, with the heaviest rainfall. Sfc winds will bcmg light
after 23Z.

&&

.MARINE...

Moderate easterly winds will prevail over the next few days.
Conditions should remain favorable for small craft. However, strong
thunderstorms will continue to affect the coastal waters of western
Puerto Rico during the afternoon hours. A weak tropical wave will
enter the eastern Caribbean today, increasing the potential for
showers and thunderstorms.

&&

.BEACH FORECAST...

The risk of rip currents will remain low through the weekend, and
possibly extending through the next midweek. Even if the risk of
rip currents is low, life-threatening rip currents often occur in
the vicinity of groins, jetties, reefs, and piers.