Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
328 AM AST Mon Jan 5 2026

...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST...

.KEY MESSAGES...
Issued at 256 AM AST Mon Jan 5 2026

* An upper-level trough and frontal boundary will increase shower
and thunderstorm activity today.

* There is an elevated flood risk through Tuesday across Puerto
Rico, particularly during the afternoon and evening hours.

* Across the U.S. Virgin Islands, there is a limited flood risk
through Tuesday, followed by a drying trend for the remainder of
the week. A moderate risk of rip currents will prevail from
midweek onward.

* Life-threatening rip currents are expected on Wednesday and
Thursday along the northwest to northeast beaches of Puerto
Rico.

&&

.Short Term(Today through Wednesday)...
Issued at 256 AM AST Mon Jan 5 2026

Similar to last night, mostly fair conditions prevailed across the
CWA, with most of the shower activity remaining across local waters
and some moving over portions of eastern Puerto Rico, including
Vieques. Since winds weakened and became light and variable, showers
persisted longer. CWOP and RAW stations reported mid-to-upper 70s
across coastal and lower elevations, and low to mid-60s across
higher elevations. Temperatures should slightly drop near sunrise,
with localized areas dropping into the upper 50s.

The short-term remains on track, with few changes for the end of the
period. Current satellite-derived products show the deep-layered
trough inducing a surface trough north of Hispaniola, producing
scattered showers and thunderstorms. As the trough approaches the
local area, a resulting cold region should move across the region,
weakening surface winds and becoming light and variable. As the col
moves out of the local area, AGL winds will strengthen and veer from
the northeast. Confidence is increasing between model solutions, as
ensembles are tending towards wetter conditions due to low to mid-
level moisture above climatological normal (between 70 and 80 %) and
high chance of PWAT values above 1.6 inches, not typical for this
time of the year. The latest guidance continues to suggest favorable
dynamics for deep convection, as cooler-than-normal mid-level
temperatures (between -10 and -11 degrees Celsius), and strong upper-
level winds (around 80kt), could lead to forced ascent, cloud
growth, and ventilation. The advective pattern will be the main
driver of showers and isolated thunderstorms throughout the day,
with the highest chance of flooding tonight into early Tuesday,
moving across local waters and windward sections of the islands.
Afternoon convection over the mountain ranges and southern hills of
Puerto Rico is still very likely, if cloud cover allows it. Due to
weakening winds, showers and thunderstorms will very likely become
stationary, producing higher rainfall accumulations and increased
flood potential. Over the U.S. Virgin Islands, mostly ponding of
water over roads, urban, and poorly drained areas, while southern
and eastern Puerto Rico will experience higher accumulations leading
to urban and small stream flooding, with a low chance of flash
flooding. Given the expected conditions, the flood threat will
remain limited to elevated. The lightning risk will remain limited,
though scattered thunderstorms across the local Atlantic waters and
passages cannot be ruled out.

The drier airmass seems to be delayed, expected to filter by late
Tuesday night instead of the afternoon, based on the latest
deterministic guidance of the GFS and AIGFS. Additionally, the 00z
solutions show enhanced upper-level divergence across the CWA,
meaning the presence of "troughiness" and instability aloft. With
the lingering moisture, the chance remains medium to high for the
development of showers and thunderstorms on Tuesday afternoon,
particularly over portions of interior and southwestern Puerto Rico.
Due to the expected rainfall accumulations and previous shower
activity, the flood potential will increase over the aforementioned
areas, hence, the flood threat will remain limited to elevated. As
the trough migrates eastward, the subsidence side of the trough
should bring more stable conditions across the CWA on Wednesday.
With drier-than-normal conditions (PWATs between 1.0 and 1.2
inches), the probability of precipitation will remain low, bringing
mostly fair conditions across the islands. As winds remain from the
NE through most of the period, temperatures should remain
seasonal.

&&

.Long Term(Thursday through Monday)...
Issued at 256 AM AST Mon Jan 5 2026

A building surface high pressure over the western Atlantic will
promote moderate to locally fresh east to northeasterly trades
during the long term period. A weak induced surface trough northeast
of the region will bring a brief surge in moisture content late in
the workweek, while a drying trend is expected during the weekend.
At upper levels, a ridge from the southwestern Atlantic and a
developing TUTT-low from the central Atlantic will promote drier
air aloft and more stable conditions in general. Therefore,
showers that form through the period are not expected to produce
heavy rainfall or grow into thunderstorms. These showers will be
mainly driven by the increasing trades, favoring an advective
pattern at night, with showers moving briefly at times across the
USVI and along the east and north sections of PR. Shallow
afternoon convection is expected over the Cordillera and southern
sections of PR, but the flood risk will remain low as rainfall
accumulations are not expected to exceed an inch of rain per day.
A TUTT induced surface trough is expected to increase moisture
content from the northeast once again early next week.

&&

.AVIATION...
(06Z TAFS)
Issued at 256 AM AST Mon Jan 5 2026

VFR conds should prevail most of the time across all TAF sites,
though a sfc trof approaching the CWA will bring -TSRA/+TSRA that
will lead to VCTS for most terminals aft 05/13z. PROB30s for JPS,
IST, and ISX btwn 05/18-21z, and for JSJ btwn 06/03-06z due -TSRA
reducing CIGs/VIS and resulting in brf MVFR conds. Winds from the NE
will slgtly increase, btwn 6 - 10 kt, around 05/13-14z, becoming
light and VRB once again after 05/23z.

&&

.MARINE...
Issued at 256 AM AST Mon Jan 5 2026

A frontal boundary with an associated polar trough approaching
the local waters will promote light northerly to northeasterly
winds, and an increase in shower and thunderstorm activity
through at least Tuesday. A long period northerly swell is
expected to arrive by midweek, building seas up to 6 feet and
occasionally higher, particularly across the Atlantic waters and
the Caribbean Passages. Small craft operators should continue to
monitor forecasts for potential changes in marine conditions.

&&

.BEACH FORECAST...
Issued at 256 AM AST Mon Jan 5 2026

A long period northerly swell will cause rough surf and life-
threatening rip currents by midweek across the north-facing beaches
of Puerto Rico. Breaking waves could range between 6 and 8 feet,
and occasionally higher, particularly on Wednesday. Elsewhere, the
risk will be moderate, except along the southern beaches where
the risk will remain low throughout the week.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
444 AM AST Tue Jan 6 2026

...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST...

.KEY MESSAGES...
Issued at 405 AM AST Tue Jan 6 2026

* Northerly winds and shower activity will prevail today as a
front moves over the region.

* Weather conditions will improve by this evening after the frontal
passage, with drier, cooler air leading to below-normal minimum
temperatures early Wednesday morning.

* Life-threatening rip currents are expected on Wednesday and
Thursday along the northwest to northeast beaches of PR, with a
moderate risk for the north and east-facing beaches in the
USVI.

&&

.Short Term(Today through Thursday)...
Issued at 405 AM AST Tue Jan 6 2026

Shower and thunderstorm activity persisted yesterday afternoon and
overnight, with the highest rainfall accumulations over portions of
Puerto Rico and the U.S. Virgin Islands. Based on WSR-88D rainfall
estimates, these areas received between 1 and 2 inches, higher in
localized areas. Taking a look at the 24-hour precipitation reports
from CWOP, ASOS, and RAW stations across the CWA, the highest
accumulations in Puerto Rico were reported at Cayey and Guayama
(1.64 and 2.16 inches, respectively). Meanwhile, across the U.S.
Virgin Islands, a station near the Henry E. Rohlsen International
Airport reported 0.95 inches. Nevertheless, no flash flood reports
were received. Although cloud cover persisted during the night,
temperatures decreased as stations at lower elevations reported low
to mid-70s, while those at higher elevations reported 60s. With
winds with a northerly component and cloud cover diminishing,
temperatures will continue to decrease, with localized areas at
higher elevations reaching the upper 50s.

Some changes were introduced to the short term forecast, as the
unsettled conditions should continue today, Three Kings Day, and
gradually improve tomorrow and Thursday. Current satellite-derived
products show the frontal boundary associated with the polar trough
across the CWA, producing showers and isolated thunderstorms. In
terms of instability, today is the best chance of thunderstorm
development, as lingering upper-level divergence, cooler than normal
mid-level temperatures (around -10 degrees Celsius), and an upper-
level jet streak producing winds between 60 and 80 kt, allowing
cloud growth and ventilation. Based on the latest HIRES models, the
advective pattern is expected to continue today, with showers and
isolated thunderstorms moving over windward sections across the
islands. For the afternoon convection, the latest solutions suggest
less widespread shower and thunderstorm activity compared to
yesterday, localized over portions of southwestern Puerto Rico. As
surface winds will begin to increase and low to mid-level moisture
should gradually decrease (700 - 500 mb RH below 20%) throughout the
day, rainfall accumulations should remain limited, leading to
ponding of water over roadways and poorly drained areas, with a low
chance of urban and small stream flooding. Hence, the flooding risk
will now remain limited over northern, southwestern, and eastern
Puerto Rico and the U.S. Virgin Islands.

As the front moves away from the region, a surface high pressure
building in the western Atlantic will promote winds from the N-NE,
with a drier air mass filtering into the region. Based on the latest
model guidance, PWAT values are expected to plummet below
climatological normal values by late tonight (PWAT between 1.1 and
1.3 inches). Additionally, the CWA is expected to be under the
subsident side of the upper-level trough, bringing more stable
conditions aloft. Hence, shower activity should remain limited on
Wednesday. Moisture content will gradually increase to more typical
values (PWAT between 1.2 and 1.4 inches) as a surface trough lingers
northeast of the region, increasing the frequency of isolated
showers over windward sections. Nevertheless, conditions should be
unfavorable for the development of thunderstorm activity. Hence, the
flood and lightning threat is not expected for the rest of the
forecast period.

&&

.Long Term(Friday through Tuesday)...
Issued at 405 AM AST Tue Jan 6 2026

A surface high pressure moving from the western Atlantic into the
central Atlantic will promote moderate to locally fresh east to
northeasterly trades during the long term period. A weak induced
surface trough northeast of the region will bring at times patches
of low-level moisture over the islands, particularly on Friday and
Saturday. During the second half of the forecast period, at the
upper levels, a ridge over the southwestern Atlantic and a
developing TUTT-low from the north central Atlantic will promote
drier air aloft and more stable conditions in general. Therefore,
showers that form through the period are not expected to produce
heavy rainfall or grow into thunderstorms. These showers will be
mainly driven by the increasing northeasterly trades, favoring an
advective pattern at night, with showers moving at times across
the USVI and along the east and north sections of PR. Shallow
afternoon convection is expected over the Cordillera and the
southern sections of PR, but the flood risk will remain low as
rainfall accumulations are not expected to exceed an inch of rain
per day.

By early next week, global models now have the strong TUTT-low
and induced surface trough a little farther away of the islands.
This solution now suggest a drier weather trend than previously
expected, with the GFS indicating a minimum in precipitable water
content of 1.00-1.25 inches on Monday and Tuesday.

&&

.AVIATION...
(06Z TAFS)
Issued at 405 AM AST Tue Jan 6 2026

Mainly VFR conds expcd across all TAF sites, with VCTS and brf prds
of -RA for ISX and IST due nearby -TSRA/+TSRA throughout the day.
Winds from the N-NE will increase btwn 10 - 12 kt, with gusts up to
20 kt over IST aft 06/13-14z. PROB30s for JSJ and JPS today btwn 18 -
21z due -TSRA reducing CIGs/VIS and leading to tempo MVFR conds.
Winds will once again weaken and become light and VRB aft
06/22-23z.

&&

.MARINE...
Issued at 405 AM AST Tue Jan 6 2026

Light to moderate northerly winds will continue today as a frontal
boundary moves across the region. Showers and isolated thunderstorms
are expected to continue through most of the morning hours. A long
period northerly swell is expected to arrive on Wednesday, building
seas up to 6 feet, particularly across the Atlantic waters and Caribbean
Passages. A surface high pressure over the western Atlantic and weak
induced surface troughs northeast of the region will promote moderate
east to northeast trades for the rest of the period.

&&

.BEACH FORECAST...
Issued at 405 AM AST Tue Jan 6 2026

A long period northerly swell will cause rough surf and life-
threatening rip currents across the north-facing beaches of
Puerto Rico, particularly on Wednesday. Elsewhere, the risk of rip
currents will be moderate, except along the southern beaches of
the islands where the risk will remain low throughout the week.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
342 AM AST Wed Jan 7 2026

...New SHORT TERM, LONG TERM, AVIATION...

.KEY MESSAGES...
Issued at 330 AM AST Wed Jan 7 2026

* Life-threatening rip currents are expected today and Thursday
along the northwest to northeast beaches of Puerto Rico. A
moderate to risk will continue along the the north and east-
facing beaches of the U.S. Virgin Islands.

* Drier air behind the frontal boundary will continue to filter
into the area today, with few passing showers reaching Puerto
Rico and the Virgin Islands, mostly during the morning and
evening hours.

* Seasonal temperatures are anticipated throughout the week with
highs in the low to mid 80s along the lower elevations of the
islands, and the mid to upper 70s in the higher mountains.

&&

.Short Term(Today through Friday)...
Issued at 330 AM AST Wed Jan 7 2026

Life-threatening rip currents along the northern beaches will be the
main hazard today and tomorrow.

Partly cloudy skies were observed across the islands during the
overnight hours. Passing showers were noted along the northern and
eastern sections of the islands, with Doppler radar estimates of
half an inch of rain over Manati and San Juan. Minimum temperatures
were from the upper 60s to low 70s across the lower elevations of
the islands to the upper 50s and mid-60s across the higher
elevations of Puerto Rico. The wind was light with a northerly
component.

For the rest of the short-term period, a similar weather pattern is
expected as a surface trough east of the region and east to
northeasterly winds brings an influx of shallow moisture content
over the area. The overall precipitable water content is expected to
range between 1.20-1.40 inches, which goes from the 25th to the 50th
percentile for this time of the year. At the mid-and upper-levels, a
ridge is expected to slowly build from the southwestern Atlantic,
promoting drier air intrusion aloft. However, only slightly warmer
500mb temperatures (around minus 7/8C) are expected, which are still
within normal seasonal levels. In summary, showers are expected each
day, and under light to moderate east to northeasterly trades,
passing showers are expected at times along the northern and eastern
sections of the islands. Shallow afternoon convection is expected to
develop over portions of the Cordillera and SW PR each afternoon,
where rainfall accumulations up to an inch and locally higher are
possible, particularly on Thursday.

In term of temperatures, daily highs are expected to range from the
mid-to upper-80s along the southern coast of PR to the low and mid-
80s across the rest of the lower elevations of the islands. Due to
the expected showers and clouds at night, seasonal temperatures are
expected at night, with minimums ranging from the upper 50s across
the higher elevations of PR to the low 70s across coastal areas.

&&

.Long Term(Saturday through Wednesday)...
Issued at 330 AM AST Wed Jan 7 2026

A strong surface high-pressure system will shift from the western to
the central Atlantic during the first half of the long-term period,
maintaining moderate to locally fresh east-northeast winds through
midweek. The forecast remains on track as a weak surface-induced
trough brings patches of moisture into the region on Saturday;
however, precipitable water values will remain at normal to slightly
below climatological normals, ranging between 1.15 and 1.35 inches.
Despite these relatively dry conditions, the combination of east-
northeast flow, daytime heating, and local effects will likely
trigger afternoon showers across portions of southwestern Puerto
Rico, though rainfall accumulations should remain below 1.00 inch.

By Monday and continuing through midweek, upper-level dynamics will
shift as a ridge builds over the southwestern Atlantic and a
Tropical Upper Tropospheric Trough (TUTT) develops over the north-
central Atlantic. These features will promote drier air aloft and
generally more stable conditions. Consequently, shower activity
during this period will be driven primarily by the northeasterly
trade winds, favoring an advective pattern that brings passing
showers to the U.S. Virgin Islands and northern and eastern Puerto
Rico, particularly during the overnight and early morning hours.

&&

.AVIATION...
(06Z TAFS)
Issued at 330 AM AST Wed Jan 7 2026

Mainly VFR conditions expected to prevail across all terminals
during the next 24 hours. However, -SHRA embedded in the trades
could move at times in and around TJSJ/TIST. Also, iso/sct shra and
sct/bkn cigs btw FL030-FL060 are expected near TJPS btw 07/17z-21z.
NE winds up to 12 kt with sea breeze variations and higher gusts
expected aft 07/14z.

&&

.MARINE...
Issued at 330 AM AST Wed Jan 7 2026

A long-period northeasterly swell is expected to spread across the
Atlantic waters and local Caribbean passages, resulting in building
seas up to 6 feet. Small craft should exercise caution under these
conditions. A surface high pressure over the western Atlantic, along
with weak induced surface troughs northeast of the region, will
promote moderate east to northeast trade winds today through the
the rest of the week.


&&

.BEACH FORECAST...
Issued at 330 AM AST Wed Jan 7 2026

A long-period northerly swell will cause rough surf and life-
threatening rip currents across the north-facing beaches of Puerto
Rico today through at least Thursday. Elsewhere, the risk of rip
currents will be moderate, except along the southern beaches of
the islands where the risk will remain low throughout the week.