Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Tue Dec 24 2024

.SYNOPSIS...

The remnants of a frontal boundary to the north northwest of the
region will continue to promote isolated to scattered showers
during the morning hours across the region. A unusual event of
Saharan dust embedded in the trade winds will arrive later today,
promoting hazy skies through Christmas Day. Marine and coastal
conditions will gradually deteriorate today, as pulses of a
northeasterly swell arrives into the area. For beachgoers, there
is a high risk of life-threatening rip currents along the northern
and eastern exposed beaches of Puerto Rico. Please refer to the
marine and beach forecast sections for more information.

&&

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

Relatively tropical flow is continuing just south of a cold frontal
boundary lying about 140 miles northwest of Aguadilla. This moist
and somewhat unstable air has been and will continue to produce
showers. It is also bringing in some Saharan dust with a narrow band
becoming quite significant with respect to its optical thickness.
Visibilities during this episode will likely drop below 10 miles and
possibly as low as 5 miles at times tonight and early Christmas
morning.

As high pressure west of the area at 700 mb just north of 20 north
continues to bring a cooler (and cleaner) air mass closer to the
local area, temperatures will gradually cool and showers will slowly
diminish through the end of the short term. East northeast flow will
also continue through the period at the surface allowing showers to
push onshore during the night and early morning hours, but also
causing showers and isolated thunderstorms over the southwest
portion of Puerto Rico. The U.S. Virgin Islands will continue to see
showers around and sometimes over them, but moderate to fresh flow
will keep accumulations from growing significantly. The push from
the north will cause the highest dust densities to move south of the
area beginning Wednesday.

Low pressure is seen along the northern coasts of Colombia. High
pressure will dig into the western Atlantic just north of the
forecast area today, but as its parent retreats northeast the ridge
it leaves in its wake will weaken. By Thursday, a ridge over the
tropical Atlantic at the surface will be instrumental in keeping low
level flow east northeast over the area.

At upper levels, a ridge extends from the southeast over the local
area. During the short-term period it shifts westward and flow at
upper levels shift from west southwest as the are today to west
northwest on Thursday.

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

Variable weather conditions are anticipated over the long-term
period, with a transition from a relatively wet into a dry and
stable weather pattern. Moisture associated with a frontal boundary
lingering north of the region will continue to promote showery
weather conditions over the weekend. At the same time, a strong
surface high pressure building in the western Atlantic and a surface
low in the central Atlantic will promote a north northeast wind flow
for most of the period. As the surface high pressure migrates
towards the central Atlantic, winds will become more from a
northerly component and pushing the frontal boundary over the local
islands. The latest precipitable water content analysis (PWAT)
guidance has values between 1.64 to 1.85 inches. Under this pattern,
the US Virgin Islands and northeastern Puerto Rico will observe
isolated to scattered showers in the morning hours. Then, followed
by afternoon rainfall over the southwestern quadrant of Puerto Rico.
By Monday into Tuesday, weather conditions are expected to dry out
as a cooler and dry airmass filters into the region. Tropical winter
temperatures will return into the islands, promoting lows in the 50s
and low 60s in the Cordillera Central and from the upper 60s to mid
70s along the coastal municipalities.

&&

.AVIATION...
(06Z TAFS)

Mainly VFR conds are expected to prevail across across all
terminals. However, dvlpg SHRA and TSRA are expected aft 24/16Z in
southwestern and interior PR so that brief MVFR conds and mtn
obscurations are expected there. Winds will be ENE 10-15 kt with sea
breeze influences that will yield hir gusts of 15-20 kts . Max winds
are WSW 50-60 kts btwn FL390-440.

&&

.MARINE...

A building surface high pressure over the Western Atlantic will
yield moderate to locally fresh east to northeast winds, creating
choppy conditions for small craft. Today, pulses of a northeasterly
swell will create hazardous marine conditions across the Atlantic
waters. In the meantime, the remnants of an old frontal will continue
to generate scattered showers and isolated thunderstorm. Later today,
a Saharan Air Layer embedded in the trade winds will arrive, leading
to hazy conditions.

&&

.BEACH FORECAST...

A high risk of rip currents is in effect for all the northern and
eastern exposed beaches of Puerto Rico due to the arrival of
pulses of a northeasterly swell and a increase in winds. There is
am moderate risk of rip currents along the beaches of western
Puerto Rico, Vieques, Culebra and the US Virgin Islands. For the
rest of the area, the risk of rip currents remains low. For more
information please refer to the local coastal and surf zone
products(CWFSJU/SRFSJU).

&&

.CLIMATE...

Warm water, being on the warm side of the front and onshore flow
damming up the land breeze early in the evening kept low
temperatures up again over Puerto Rico. San Juan broke its warm
minimum record of 77 degrees today when it was only able to cool to
78 degrees. No records were broken yesterday in the U.S. Virgin
Islands, although their lows were close.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
427 AM AST Wed Dec 25 2024

.SYNOPSIS...

Showers and isolated thunderstorms are expected for Christmas Day
across portions of the islands. An old frontal boundary north of
the region will continue to promote showery weather conditions
through the weekend under light to moderate northeasterly winds. A
strong pulse of Saharan dust has reached the region, promoting
hazy skies and reduced visibilities. Marine and coastal conditions
will continue deteriorated due to breezy conditions and a pulse
of northeasterly swell across the Atlantic waters and the Mona
Channel.

&&

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

Clear to partly cloudy skies prevailed during the early morning
hours across Puerto Rico and the U.S. Virgin Islands. Quick passing
showers were noted along the northern and eastern sections of the
islands. The Doppler radar estimated between 0.25-0.50 inches of
rain with this activity. Minimum temperatures were from upper 60s to
low 70s across the higher elevations to the mid and upper 70s across
the lower elevations. The wind was from the northeast around 10 mph
with land breeze variations.

An old frontal boundary north of the region will continue to bring
shallow moisture content through the short-term period under light
to moderate east to northeast winds. At mid-levels, an atypical
Saharan Air Layer with suspended Saharan dust will continue to
promote hazy skies across the islands today. Although drier air
aloft will be present across the area, the 500 mb temps are forecast
to remain around minus 7/7.5 degrees C and PWAT content should
fluctuate between 1.6-1.8 inches. This will aid in the development
of locally induced afternoon showers with possible isolated
thunderstorms over the SW quadrant of PR each afternoon. Meanwhile,
colder air moving over warmer waters under the ENE winds will bring
passing showers across the USVI and northern/eastern sections of PR
during the nighttime and early morning hours thru the period.

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

The latest model guidances continues to suggest a very dry and
cooler pattern for most of the long-term period. Moisture associated
with a cold front north of the region is anticipated to cross the
islands by Saturday into Sunday. As the front moves over the region,
isolated to scattered showers are likely mostly over the
northeastern municipalities of Puerto Rico and the US Virgin
Islands during the morning hours. Then, in the afternoon hours
the southern and southwestern portions of Puerto Rico will observe
the development of more shower activity over the area. A drop in
precipitable water content is expected by Monday with values
around 1.35 inches. Therefore, limited shower activity and stable
weather conditions are anticipated for the New Year's
festivities. At the surface levels a building strong high
pressure moving-off the eastern coast of the Continental United
States and a strong low in the central Atlantic will promote a
moderate to locally fresh wind flow from the north across the
region. As both of the systems builds up over the waters, cooler
and dry air will filter into the region promoting temperatures to
drop during the overnight hours.

&&

.AVIATION...

(06Z TAFS)

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. However, trade wind SHRA could persist
through 25/13z across the USVI and eastern PR terminals, causing
brief MVFR cigs. Also, SHRA/TSRA expected to develop near TJPS btw
25/17z-21z. Mtn tops obscd expected along the Cordillera. HZ due to
Saharan dust will continue but VSBY should remain P6SM. Winds mostly
ENE at 10-15 kt with stronger gusts at times.

&&

.MARINE...

A building surface high pressure over the Western Atlantic will
yield moderate to locally fresh east to northeast winds, creating
choppy conditions for small craft. Confused seas will create
hazardous marine conditions across the Atlantic waters. In the
meantime, the remnants of an old frontal will continue to generate
scattered showers and isolated thunderstorm. Saharan dust will
maintain hazy skies for the next several weeks.

&&

.BEACH FORECAST...

Strong winds will continue to enhance the risk of life-
threatening rip currents along the north coast of Puerto Rico.
Elsewhere, the risk is moderate.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
447 AM AST Thu Dec 26 2024

.SYNOPSIS...

A weak Saharan Air Layer with minor dust concentrations continues
across the area today. The remnants of an old front north of the
region will continue to bring on and off showers for the next
couple of days. Temperatures will cool down a little by the end of
the week and early next week. Hazardous seas across the Atlantic
waters and life-threatening rip currents are expected late in the
weekend due to the arrival of a northerly swell.


&&

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

Fair weather conditions prevailed overnight, with few passing
showers in the eastern portions of Puerto Rico and the local
waters. Radar rainfall estimates were up to 0.05 inches.
Temperatures dropped to the low and mid 70s in the coastal and
urban areas while the interior sections reported temperatures in
the low 60s.

Satellite-derived products show Precipitable Water (PWAT) values
around seasonal values across the region. As the atypical Saharan
dust concentrations decrease, model guidance suggests an increase in
moisture content at both low and mid-level layers due to the
remnants of a frontal boundary. PWAT values are expected to
fluctuate from 1.7 to 1.9 inches each day during the forecast
period, above the climatological normal. Additionally, 500 mb
temperatures will range from -6 to -8 Celsius, near below
normals. An easterly wind flow will prevail today, and in
combination with the available moisture and local effects, shower
activity is anticipated in windward sections of the local islands
during the morning hours and moderate to heavy showers with
isolated thunderstorms in the interior and western sections of
Puerto Rico, including the San Juan Metropolitan Area. Rainfall
accumulations will promote ponding of water in roadways and poorly
drained areas, with isolated urban and small stream flooding.

The wind flow is expected to turn from the NNE by late Friday due
to the influence of a high pressure exiting eastern CONUS. This
will promote a cooler trend with temperatures reaching below-
normal values.


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

The latest model guidance indicates a dry and cooler weather pattern
for most of the long-term period. However, shallow moisture content
associated with the passage of a cold front during the weekend is expected
to linger over the islands on Sunday. As the front passes over the area,
isolated to scattered showers are likely, primarily affecting the northeastern
municipalities of Puerto Rico and the U.S. Virgin Islands during the
morning. In the afternoon hours, shower activity is anticipated
in the southern and southwestern sections of Puerto Rico.

A surface high pressure over the western Atlantic responsible of pushing
the front across the area, and a broad surface low developing in the
central Atlantic, will promote moderate winds from the north-northeast
through midweek. As these systems strengthen over the waters, cooler
and drier air will move into the area, resulting in lower temperatures
during the overnight hours. A decrease in precipitable water content
is forecasted from Monday onwards, with values around 1.25-1.45 inches,
just below climatology. Consequently, limited shower activity and stable
weather conditions are expected for the New Year's festivities. However,
cooler air under northerly winds may bring occasional passing showers
along portions of north- northeastern Puerto Rico and the USVI
during the nighttime.


&&

.AVIATION...

(06Z TAFS)

Mainly VFR conds are expected at all terminals with VCSH thru fcst
period. SHRA anticipated at JSJ and possible TSRA at JBQ btw
17-22z that may cause brief MVFR conds. East winds at 5-12 kts
will prevail today, shifting from the NNE by late Friday.


&&

.MARINE...

A building surface high pressure over the Western Atlantic will
yield gentle to moderate east to northeast winds. Increasing winds
and a northerly swell from a surface low over the central Atlantic
arriving this weekend will deteriorate seas once again, and Small
Craft Advisory conditions are expected across the Atlantic waters.
In the meantime, patches of moisture carried by the winds will lead
to passing showers across the waters, with possible isolated
thunderstorms over the western waters of Puerto Rico during the
afternoons.


&&

.BEACH FORECAST...

A moderate risk of rip currents is expected to prevail across most
north and east facing beaches of Puerto Rico, and across most
beaches of the U.S. Virgin Islands through early Saturday. Life-
threatening rip currents are expected once again across the north
facing beaches of Puerto Rico from Fajardo to Rincon, and Culebra on
Sunday and early next week due to a long period northerly swell. A
low risk of rip currents is expected across the southern protected
beaches of Puerto Rico.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
442 AM AST Fri Dec 27 2024

.SYNOPSIS...

A building surface high over the western Atlantic will promote
moderate northeasterly winds across the region for the next few
days. These winds will push the remnants of an old frontal
boundary across the islands. An upper-level jet just north of the
region will promote favorable conditions aloft that will enhance
shower and possible thunderstorm activity through Saturday. Cooler
temperatures are expected from Sunday onwards. Hazardous seas
across the Atlantic waters and life-threatening rip currents are
expected to return on Sunday into early next week due to the
arrival of a northerly swell.


&&

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

Overnight, most of the rainfall activity stayed over the Atlantic
and Caribbean waters, as well as passages. Nonetheless, some showers
filtered across eastern Puerto Rico, Vieques, and Culebra, leaving
around 0.10 to 0.30 inches of rain. The rest of Puerto Rico, Saint
Thomas, Saint John, and Saint Croix experienced calm weather
conditions with little to no rain. The temperatures along the urban
and coastal areas remained in the 70s, while in the
mountainous/rural areas, they remained in the 60s throughout the
night.

The latest model guidance suggests an upper-level jet interacting
with a trade wind perturbation and enhancing periods of rainfall
activity throughout the day. However, we forecast the heaviest
activity taking place this afternoon and evening, leading to a
slight to moderate chance of observing flooding rains across
portions of the islands. The jet maximum of approximately 50 to 60
knots will be moving across the region today into Sunday. The time-
height series model suggests enough moisture extending from the
surface to the mid-levels as well as the upper level. At this time,
the forecast leans towards Friday(today) being the wettest day of
the short term period. From Saturday onwards, we anticipate the
introduction of a drier airmass and an advective tropical-winter
weather pattern (sunshine/mostly clear skies and clouds with
occasional showers embedded in the easterly winds) dominating PR and
the USVI across the windward sections of PR and the USVI each day.
Showers will then spread into the interior and western sections of
PR during the afternoon. Therefore, we cannot rule out water ponding
due to moderate to locally heavy rains in areas where these showers
become frequent. The wind flow will gradually become from the north-
northeast later today due to the influence of a high pressure
exiting the eastern coast of the United States. This weather pattern
will promote a cooler trend, with temperatures reaching below-normal
values.

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

A surface high pressure over the western Atlantic and a broad
surface low developing in the central Atlantic, will promote
moderate winds from the northeast through the workweek. As these
systems strengthen over the waters, cooler and drier air will move
into the area, resulting in lower temperatures during the
overnight hours. A decrease in precipitable water (PWAT) content
is forecasted from Monday onwards, with values fluctuating in
general between 1.25 and 1.45 inches, just below climatology.
Consequently, limited shower activity and stable weather
conditions are expected for the New Year's festivities. However,
cooler air under northeasterly winds moving over warmer coastal
waters may bring occasional passing showers along portions of
north central and northeastern Puerto Rico and the USVI during the
nighttime and early morning hours.


&&

.AVIATION...

(06Z TAFS)

All Tafs sites will experience mainly VFR conds with VCSH thru fcst
period. SHRA anticipated at JSJ and possible TSRA at JBQ btw 16-22z
that may cause brief MVFR conds. Winds will gradually shift from the
ENE to NNE at 5-12 kts today.


&&

.MARINE...

A building surface high pressure over the Western Atlantic will
yield gentle to moderate east to northeast winds. Increasing winds
and a northerly swell generated by a surface low over the central
Atlantic will arrive this weekend and deteriorate marine and
coastal conditions once again. Small Craft Advisory conditions
are anticipated across the Atlantic waters.

The remnants of a frontal boundary pushed by the northeasterly
winds and favorable environmental conditions will lead to scattered
showers and possible isolated thunderstorms over the local waters
today and on Saturday.


&&

.BEACH FORECAST...

A moderate risk of rip currents is expected to prevail across most
north and east facing beaches of Puerto Rico, and across most
beaches of the U.S. Virgin Islands through early Saturday. Life-
threatening rip currents are expected once again across the north
facing beaches of Puerto Rico from Fajardo to Rincon, and Culebra on
Sunday and early next week due to a northerly swell. A low risk
of rip currents is expected across the southern protected beaches
of Puerto Rico.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
330 AM AST Sat Dec 28 2024

.SYNOPSIS...

The remnants of an old frontal boundary will continue to push
showers across the islands through the morning and afternoon
hours. A weak front is expected to move over the islands on
Sunday. Therefore, cooler temperatures and drier conditions are
expected from Sunday onwards. Hazardous seas across the Atlantic
waters and life-threatening rip currents are expected stating
tonight due to the arrival of a northerly swell.

&&

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

The remnants of an old frontal boundary pushed through the islands
during the night and early morning hours. The Doppler radar
estimated between 2 and 3 inches of rain in St. Thomas and between 1
and 2 inches in St. Croix and along the northern coastal
municipalities of Puerto Rico. Minimum temperatures were in the low
to mid-70s across the lower elevations to the mid and upper 60s
across the higher elevations.

For the rest of the day, moderate to fresh northeast steering winds
will continue to push southwards into the Caribbean Sea, the
fragmented cloudiness and shower activity from the old front.
Therefore, variably cloudy skies with periods of light to moderate
rainfall will generally continue across the islands through the
morning hours. A drier air mass between 700-500 mb over the Atlantic
under northerly winds should gradually filter from this evening
onwards through the rest of the short-term period. However, at lower
levels, a weak front is expected to make its way tonight with FROPA
by Sunday morning. In response to this weather scenario, the
precipitable water content will drop significantly, from nearly 2
inches early this morning to 1 inch by 12z on Sunday. Fair weather
conditions should prevail on Sunday and Monday, with much cooler
temperatures during the day and night.

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

A strong surface high pressure migrating from the western to central
Atlantic and a broad surface low in the central Atlantic will
continue to promote a northeasterly wind flow through the weekend.
With the forecast on track, cooler and drier air will filter into
the region as both of the aforementioned systems strengthens over
the Atlantic. With the entrance of the cooler airmass, a drop in
low temperatures is expected during the overnight hours. The
latest model guidance are in agreement with a decrease in
precipitable water content (PWAT) through most of the week, with
values ranging between 0.75 to 1.15 inches. Therefore, limited
shower activity is expected across the islands, especially for
the New Year's festivities. Nonetheless, for the rest of the
period occasional passing showers over northeastern Puerto Rico
and the US Virgin Islands cannot be ruled out due to the
combination of cooler temperatures and warmer waters surrounding
our region. Overall, minimum temperatures will range from the
upper 50s to low 60s in the higher elevations, to the mid 60s to
low 70s in the coastal and urban areas.

&&

.AVIATION...
(06Z TAFS)

Mostly -SHRA expected to continue thru the morning hours across the
area terminals. Mtn tops obscd and BKN/OVC lyrs expected fm FL030-
FL060. Conditions will improve gradually from the northern terminals
to the southern terminals of the islands after 28/16z, but overall
VFR conds expected. Winds from the NE increasing at 12-16 kt with
stronger gusts aft sunrise.

&&

.MARINE...

A building surface high pressure over the Western Atlantic will
continue to yield gentle to moderate east to northeast winds. Expect
an increase in winds today, and a northerly swell arriving between
late tonight into early Sunday that will deteriorate marine
conditions once again. In the meantime, the remnants of a frontal
boundary carried by the trade winds and favorable environmental
conditions will lead to scattered showers and isolated thunderstorms
over the waters.

&&

.BEACH FORECAST...

A moderate risk of rip currents is expected to prevail across most
north and east facing beaches of Puerto Rico, Vieques, Culebra
and the beaches of the U.S. Virgin Islands through tonight. Life-
threatening rip currents are expected once again across the north
facing beaches of Puerto Rico from Fajardo to Rincon from tonight
into early next week due to the arrival of a northerly swell. A
low risk of rip currents is expected across the southern protected
beaches of Puerto Rico.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
524 AM AST Sun Dec 29 2024

.SYNOPSIS...

A surface high pressure over the western Atlantic and a surface
low over the central Atlantic will promote moderate northeasterly
winds across the region for the next few days. Cooler temperatures
are expected to continue for most of the forecast period. Hazardous
seas are expected across the Atlantic waters and passages, as well
as life-threatening rip currents due to the arrival of a northerly
swell through at least early in the week.


&&

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

Fair weather and cool temperatures prevailed in the late night
hours. Temperatures across the urban and coastal areas remain in the
70s with localized areas dropping to the upper 60s. At the interior,
temperatures remained in the low 60s and upper 50s.

Current satellite-derived products show Precipitable Water (PWAT)
values below climatological normals due to a drier air mass in the
mid to high levels reaching the local islands. Based on the latest
model guidance, PWAT values shall remain between 1.0 to 2.0 inches.
This will promote more stable conditions, inhibiting convection
activity. However, a weak frontal boundary moving across the region
and patches of moisture will promote isolated passing showers across
windward sections early in the morning and southwestern Puerto Rico
in the afternoon each day. With the northeasterly windflow and 925
mb temperatures below normal, cooler and seasonal temperatures
should persist for the rest of the short-term period, including New
Year's Eve.


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

The surface high over the central Atlantic is expected to sink
southwards and hold through most of the long term period just
north/northeast of the Leeward Islands. This will continue to
promote northeasterly winds and a cool advective weather pattern
each day. A frontal system is forecast to push further eastward
and weaken the high during the weekend. This will allow winds to
veer from the southeast as a pre-frontal trough develops over the
northeastern Caribbean. Therefore, warmer temperatures and a
noticeable increase in shower activity is anticipated during this
period.

In the meantime, cooler temperatures and mainly fair weather
conditions should prevail across the islands through the end of
the workweek as PWAT remains below normal levels between
1.20-1.40 inches. Nonetheless, for the rest of the period
occasional passing showers over northeastern Puerto Rico and the
US Virgin Islands cannot be ruled out due to the combination of
cooler air moving over warmer waters.


&&

.AVIATION...

(06Z TAFs)

Mainly VFR conditions for all terminals for the fcst prd.
NE winds btw 10-15 kt with gusts around 20 kt for north-facing
terminals by 29/17z. VCSH is expected btw 16-22z for TJSJ, TJBQ,
and TISX due to a weak front and patches of moisture.


&&

.MARINE...

A surface high pressure over the Western Atlantic and a surface low
over the central Atlantic will promote moderate northeast winds for
the next few days. A northerly swell will continue to build seas up
to 8 feet across the Atlantic waters and passages through at least
Monday.


&&

.BEACH FORECAST...

There is a High Rip Current Risk in effect for the north facing
beaches of Puerto Rico, from Rincon to Fajardo, and Culebra due
to a northerly swell. A moderate rip current risk will be present
for the north facing beaches Vieques and the USVI. As the swell
continues to fill across the Atlantic waters and passages, the
high risk of rip currents will spread to these areas later tonight
and last through at least late Monday night. A low risk of rip
currents is expected across the southern protected beaches of
Puerto Rico.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
450 AM AST Mon Dec 30 2024

.SYNOPSIS...

A surface high-pressure migrating from the Western to Central
Atlantic will promote a seasonal advective weather pattern with
pleasant tropical winter temperatures and occasional showers
across the windward sections each day. The trade winds will bring
occasional showery weather, especially across the windward
sections of north and east PR and the US Virgin Islands during the
New Year's Eve. Pulses of northeasterly swells producing
dangerous breaking waves will create life- threatening rip
currents along the north and east-facing beaches of the US Virgin
Islands and Puerto Rico throughout the day. There is a slight to
moderate chance that instability and rain activity will increase
by next weekend due to another cold front and a polar trough that
could move near the Northeast Caribbean.

&&

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

The weather conditions remained calm without rain activity, mainly
across the leeward areas. However, showery weather was observed
across the windward locations of north and northeastern Puerto
Rico, the US Virgin Islands and the local Atlantic waters.
Minimum temperatures again dropped below normal, as some stations
in lower terrains reported temperatures in the low to mid 70s with
localized areas reaching the upper 60s. In the higher terrains,
temperatures dropped to the low 60s, reaching the upper 50s early
in the night.

A seasonal and mostly stable pattern is expected to prevail in the
short-term period. A surface high pressure in the Western
Atlantic, interacting with a surface low over the Central
Atlantic will promote northeasterly winds and an advective
pattern. Model guidance keeps suggesting PWAT values below
climatological normal as drier air in the mid-levels filters into
the region. However, patches of low-level moisture will promote
passing showers, mostly for the eastern portions of Puerto Rico,
Vieques, Culebra, and the U.S. Virgin Islands during the morning
and mostly likely on New Year's Eve. Shower activity is also
expected in southwestern Puerto Rico each day in the afternoon.
The northeasterly wind flow and below-normal 925 mb temperatures
will continue bringing fresher temperatures during the day and
night.

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

A subtropical surface high pressure will continue to promote
trade winds, pushing a cooler air mass and thus cooling local
temperatures. Meanwhile, pockets of moisture embedded in the
trades will occasionally bring quick passing showers.

A frontal boundary will move out of the Eastern U.S. around
Wednesday, gradually moving eastward behind the surface high
pressure system. By next weekend, it will approach the Northeast
Caribbean, bringing additional moisture to the area. There is a
slight chance of a pre-frontal trough developing near the local
islands. Along with the front, a mid to upper-level trough will
pass near the islands, increasing local instability. Given this
weather pattern, we can anticipate an increase in shower activity,
along with a slight to moderate chance of isolated to scattered
thunderstorms from Saturday afternoon into Sunday, if this pattern
persists.

The global models differ slightly on whether the front will cross
the islands by next week, promoting an extension in the typical
winter cooler temperatures. Therefore, we will examine this
possibility more closely as time passes.

&&

.AVIATION...
(06Z TAFs)

Mostly VFR conditions for all terminals, with TEMPO 3007/10 for TJSJ
and TISX due -RA reducing CIG/VIS. Light to moderate NE winds
will prevail for the fcst prd with patches of shallow moisture
promoting -SHRA and VCSH btw 16/22z. VCSH for TJBQ and TJPS
around 18z. Brief periods of MVFR conditions can be expected
across JSJ/IST/ISX due to +SHRA/SHRA and BKN/OVC between
FL025/FL050. Winds will turn calm-light/VRB aft 30/23z.

&&

.MARINE...

A surface high pressure over the Western Atlantic and a surface low
over the central Atlantic will promote moderate northeast winds for
the next few days. A northerly swell will continue to build seas up
to 8 feet, occasionally higher, across the Atlantic waters and
passages through at least tonight. As a result, a Small Craft
Advisory is in effect for this locations.

Another front will move from the eastern US into the western
Atlantic by Wednesday. From midweek onward, it will move eastward,
approaching the northeast Caribbean by the weekend.

&&

.BEACH FORECAST...

Pulses of northeasterly swells are moving across the Atlantic
Offshore Waters and Caribbean Passages, producing dangerous
breaking waves along the north and east-facing beaches in PR and
the US Virgin Islands. Therefore, we expect life-threatening rip
currents along this locations, where we have in effect a High
Surf Advisory and High Risk of Rip Currents through at least this
evening. For additional information, please refer to the Coastal
Hazard Message (CFWSJU) and Surf Zone Forecast (SRFSJU).

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
452 AM AST Wed Jan 1 2025

.SYNOPSIS...

The winter advective pattern will promote pleasant temperatures
with occasional passing showers throughout the beginning of 2025.
Shower activity will affect mainly PR and the USVI's windward
locations. By next weekend, instability and rainfall activity will
increase slightly to moderately due to the potential approach of
another cold front with a pre-frontal trough near the Northeast
Caribbean. Another long-period northeasterly swell will
deteriorate the marine and coastal conditions by the weekend and
early next week. Next week's weather will be tight to the final
position of the cold front that will linger near the Northeast
Caribbean.

&&

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

A showery beginning of the year was observed as patches of moisture
moved across the region. This pattern prevailed all night just
before New Year's, with stations in eastern Puerto Rico reporting
accumulations up to 0.25 inches and the station in Culebra observed
approximately 0.33 inches. Temperatures remained slightly higher
than yesterday, as stations in urban and coastal areas reported low
to mid 70s while the interior remained in the low to mid 60s with
localized areas dropping to low 50s.

The current radar loop and VAD Wind Profile show NE winds bringing a
few passing showers across the local waters and windward sections.
Satellite-derived products show Precipitable Water (PWAT) values
between 1.1 - 1.4 inches as expected by model guidance. The high
surface pressure in the Western Atlantic and the low surface
pressure in the Center Atlantic will keep promoting NE to ENE
winds as the high pressure builds in the Central Atlantic making
way for a frontal system just east of CONUS moving southeastward
near Hispaniola. Patches of moisture will move across the local
islands today and tomorrow, increasing from below normal to
seasonal PWAT values. The advective pattern will prevail, with mix
in clouds and periods of passing showers in the morning and
during the night hours for northern and eastern Puerto Rico,
Vieques, Culebra, and the U.S. Virgin Islands. Shallow convection
in the afternoon is anticipated in southwestern Puerto Rico,
increasing risk of flooding. Rainfall accumulations are likely to
promote ponding of water in roadways, urban, and poorly drained
areas.

More stable conditions are expected on Friday as model solutions
agree that a mass of drier air will reach the local islands.
However, moisture content will gradually increase in the night. The
fresher temperatures will continue across the region for the second
part of the workweek into the weekend.

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

A cold front will drift slowly eastward near the Northeast
Caribbean, inducing a pre-frontal trough near or over PR/USVI
around Saturday afternoon into Sunday. At the same time, the trade
winds will promote moisture pooling and pleasant temperatures.
Along with the front, a mid-to upper-level trough will near the
islands, increasing local instability over the weekend and next
week. Given this weather pattern, we can anticipate an increase in
shower activity and a slight to moderate chance of isolated to
scattered thunderstorms. Still, the global models show some
discrepancy in the amount of precipitation that our region will
experience.

The GFS model indicates that the frontal boundary may linger north
of near the islands, influenced by one high pressure system over
the Central Atlantic and another surface high trailing behind the
front. In contrast, the ECMWF model suggests frontal passage
(FROPA) late Sunday night or early Monday morning. These
scenarios suggest two possible outcomes for early next week:
showery conditions per the GFS or drier, windy and cooler
conditions, according to the ECMWF. We will continue to monitor
and assess this potential as the forecast evolves.

Pulses of a long period northeasterly swell will create life-
threatening rip currents due to dangerous breaking waves along the
exposed north and east-facing beaches in PR and the USVI from
Friday to Sunday. The hazardous coastal conditions could extent
from Monday onward as another north-to-northwest long period swell
arrives from the Atlantic Ocean.

&&

.AVIATION...
(06Z TAFs)

Mostly VFR conds for all terminals in NYD. FU and -RA
will prev for TJSJ btw 04-08z. Expect NE-ENE winds at 5-12 kt with
sea breeze variations through the day. Patches of moisture will
promote SHRA and VCSH for most TAF sites btw 01/12-01/22z,
resulting in BKN-OVC CIGs and reduced VIS.

&&

.MARINE...

Moderate northeast winds in place for early this week under a surface
high pressure in the Western Atlantic and surface low over the
Central Atlantic. Another front from the eastern US coast will move
into the western Atlantic by midweek, approaching the northeast
Caribbean by the weekend. Another long- period northerly swell will
promote hazardous seas by the end of this week through the
weekend.

&&

.BEACH FORECAST...

Pulses of a fading northeasterly swell, moving across the Atlantic
waters and Caribbean passages, will promote a moderate risk of rip
currents along the north and east-facing beaches of PR/USVI,
including Culebra. Meanwhile, the southern protected beaches of PR
remain under a low risk of rip currents.

Coastal conditions will deteriorate again around Friday through
the weekend with the arrival of another long-period northerly
swell.

&&

.CLIMATE...

The year 2024 will end as the warmest year on record for the San
Juan Area climate site. These records date back to 1898.
Additionally, December 2024 will end as the second warmest December
on record as well, for the San Juan Area site, and also for Henry E.
Rohlsen in Saint Croix.

For the San Juan Area site, it will end also as the eight wettest on
record, with 78.93 inches collected.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
358 AM AST Thu Jan 2 2025

.SYNOPSIS...

The citizens and visitors of Puerto Rico and the U.S. Virgin
Islands should experience limited shower activity and pleasant
temperatures for the next few days. By next weekend,conditions
will become more wet and unstable with the potential approach of
another cold front with a pre- frontal trough near the region.
Marine and coastal conditions are expected to deteriorate by late
Friday and early next week due to the arrival of another long-
period northeasterly swell.

&&

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

Overnight, a slot of dry air limited rain activity to the
surrounding waters, and PR and the USVI observed pleasant
temperatures with clear skies. The winds were from the northeast,
and low temperatures were in the low 70s along the coast to the low
60s or even the 50s across mountains and valleys.

A surface high pressure north of the islands moving into the Central
Atlantic will promote a northeasterly wind flow through at least
Friday. The wind flow will maintain pleasant temperature across PR
and the USVI, with the arrival of pockets of moisture at times. This
moisture embedded in the trades will result in occasional quick
passing showers, mainly across the windward locations. The interior
and western sections of PR will see some showers in the afternoon,
especially today. On Friday, moisture below normal will limit rain
activity, leaving a mix of clouds and sunshine or clear skies.

A cold front behind the surface high pressure will approach the
Northeast Caribbean around Saturday afternoon, inducing a pre-
frontal trough and pooling above-normal moisture over PR and the
USVI. GFS suggests steep lapse rate at low-levels, which, combined
with local effects, could promote widespread rains. Under this
weather pattern, we can anticipate a migration to a wet and
unsettled pattern with scattered to widespread showers and a slight
chance of isolated to scattered thunderstorms, especially from
Saturday afternoon into Sunday. Urban and small stream flooding
can be observed with the most intense rain activity.

&&

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

At this time, both the Global Forecast System (GFS) and European
Centre for Medium-Range Weather Forecasts (ECMWF) models agree on a
cold front moving across the Northeastern Caribbean inducing a pre-
frontal trough near Puerto Rico and the U.S. Virgin Islands,
particularly on Sunday. The latest guidance suggest precipitable
water values above the 75th percentile or above normal values for
this time of the year, with values ranging around 1.5 to 2.0
inches. Also, the Galvez-Davison Index (GDI)suggest thunderstorm
activity across the islands through Sunday afternoon. The surface
moisture is forecast to lift and reach the 500 to 700 mb through
the beginning of the workweek. This increase in precipitable water
values and instability leans towards having an active weather day
with an increase in shower activity and a slight to moderate
chance for isolated to scattered thunderstorms by the end of the
weekend, possibly extending towards the beginning of the
workweek. Therefore, urban and small stream flooding can be seen
with the heaviest rainfall activity.

Weather conditions should slightly improve by Tuesday into
Wednesday with cooler temperatures and somewhat drier air.
However, the wet pattern will return by Thursday when another cold
front approaches the region.

&&

.AVIATION...
(06z TAF)

VFR conds will prevail today under a northeast wind flow. Expect
calm to light and VRB winds thru 02/13z, then winds will range
between 10-15 kt with higher gusts and sea breezes. A patch of
clouds will bring SHRA/-SHRA across JSJ/IST/ISX btwn 02/10-18z, and
we cannot rule out brief periods of MVFR conds. SHRA will develop
into PR's interior and southwest sections btwn 02/15-22z, which
could impact the JPS's vicinity.

&&

.MARINE...

Moderate northeasterly winds will continue to prevail this week
under the influence of a surface high pressure moving into the
Central Atlantic and surface low over the Eastern Atlantic. Another
front from the eastern US coast will approach the northeast Caribbean
by the weekend. Another long period northerly swell will promote
hazardous seas by the end of this week through the weekend.

&&

.BEACH FORECAST...

Pulses of a fading northeasterly swell, moving across the Atlantic
waters and Caribbean passages, will promote a moderate risk of rip
currents along the north and east-facing beaches of PR/USVI,
including Culebra. Meanwhile, the southern protected beaches of PR
remain under a low risk of rip currents.

Coastal conditions will deteriorate again by Friday night through
the weekend with the arrival of another long-period northerly
swell.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
352 AM AST Fri Jan 3 2025

.SYNOPSIS...

The citizens and visitors of Puerto Rico and the U.S. Virgin
Islands should experience mostly calm weather conditions today as
a drier airmass filters across the islands. Expect a change in
weather conditions on Saturday, when a cold front and the induced
pre frontal trough brings an increase in moisture through at
least late Sunday.

&&

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

The majority of the islands observed mostly clear skies, with some
clouds moving overnight. Nighttime cooling promoted low temperatures
in the low 70s along the coast to the low 60s or even the 50s across
the mountains and valleys. Under a northeasterly wind flow, a few
showers arrived over the windward sections of PR, the Virgin
Islands, and the regional waters.

A dry air mass with a ridge aloft will promote a stable weather
pattern with little or no rain activity. The surface high pressure
across the Central Atlantic will promote a northeast wind flow,
continuing the pleasant temperatures. Therefore, expect a mix of
sunshine and clouds with one or two quick showers, mainly across the
windward sections in PR and the US Virgin Islands.

The interaction between a cold front approaching from the west and
the surface high pressure across the Central Atlantic will result in
shower activity across the local waters and windward sections of PR
and the USVI late tonight into early Saturday morning. As the front
approaches the region, it will induce a pre-frontal trough pooling
near to above normal moisture over the islands on Saturday
afternoons and Sundays. This weather pattern will result in an
unsettled weather pattern with scattered to numerous showers and a
slight to moderate chance of observing isolated to scattered
thunderstorms. Therefore, expect a slight to moderate risk of
flooding rains during that time. From Sunday evening onward,
conditions will improve with the arrival of a drier air mass and the
establishment of a ridge aloft.

&&

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

The latest weather forecasts suggest that precipitable water values
will gradually decrease from above-normal levels to around normal by
Monday. We expect that the available moisture will remain confined
below 700mb, meaning any rainfall that develops is unlikely to grow
significantly in vertical depth. This reduces the likelihood of
heavy rainfall or intense thunderstorms.

As Three Kings Day approaches, it is worth noting that it is
unlikely the development of significant disruptive weather events
during the celebrations. On the morning of January 6th, both
residents and visitors in Puerto Rico and the U.S. Virgin Islands
can expect some passing showers, primarily driven by residual
moisture from a recent cold front and the associated pre-frontal
trough that passed close to the region. Cooler temperatures are also
expected as a result of the cold front's passage. However,
conditions are anticipated to improve gradually throughout the day.
Light, intermittent showers may still occur, consistent with the
typical tropical winter weather pattern and the available moisture
across the area.

Overall, we expect this weather pattern, characterized by sporadic
showers and slightly cooler temperatures, to persist across the
islands during the long term. The forecast suggests that Puerto Rico
and the U.S. Virgin Islands will continue to experience relatively
calm conditions with brief episodes of light precipitation, which is
typical during winter in this tropical climate.

&&

.AVIATION...
(06Z TAFS)

VFR conditions will prevail today under a northeast wind flow.
Expect calm to light and VRB winds through 02/13z, then winds will
range between 10 and 15 kt with higher gusts and sea breezes. Local
effects will promote cloud development and SHRA/-SHRA across the
interior and western sections around 03/16-22z.

&&

.MARINE...

Moderate east to northeasterly winds will continue to prevail this
week under the influence of a surface high pressure moving into the
Central Atlantic and surface low over the Eastern Atlantic. A cold
front will approach the northeast Caribbean during the weekend. A
long period northeast swell will spread across the Atlantic waters
and passages from today onwards. A larger northwest swell will
arrive later on Sunday and linger through early next week. Hazardous
seas are expected from Saturday through Tuesday.

&&

.BEACH FORECAST...

A long-period northeasterly swell will gradually spread across
the local waters on today. This swell will increase the risk of
life-threatening rip currents for the northern and eastern exposed
beaches of Puerto Rico, Culebra and St. Croix. In addition,
another long- period northwesterly swell will arrive late Sunday
into early next week.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
423 AM AST Sat Jan 4 2025

.KEY MESSAGES...

* Unsettled and wet conditions (increased shower activity) will
continue through Sunday, with isolated thunderstorms possible,
potentially leading to localized flooding impacts.
* Northerly swells and strengthening northeasterly winds will create
choppy to hazardous seas for small craft over the Holiday weekend.
* Life-threatening rip currents will continue through at least
early next week across the northern and eastern exposed
beaches.


&&

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

Overnight, relatively calm weather conditions prevailed across the
islands, particularly over the western half of Puerto Rico. In
contrast, the eastern half, as well as Vieques and Culebra,
experienced passing showers throughout the night, with rainfall
accumulations around a quarter of an inch to half an inch over
northeastern Puerto Rico and portions of the San Juan metropolitan
area. Surface weather observations indicated temperatures in the
70s in coastal and urban areas, while mountainous and rural areas
experienced temperatures in the 60s. Northeasterly winds were
present at speeds of around 5 to 10 mph.

The latest model guidance continues to suggest a building surface
high-pressure over the southwestern Atlantic. This weather feature
is expected to push a frontal boundary toward the region. As it
approaches from the west, it will induce a pre-frontal trough,
increasing moisture levels and precipitable water (PW) content to
approximately two standard deviations during the weekend. PW is
foreseen to peak on Sunday, reaching up to 2 inches. As noted in
previous discussions, instability will gradually increase today,
peaking on Sunday, as indicated by cooler 500 mb temperatures and
rising Galvez-Davidson Index values. This shift in the weather
pattern will lead to scattered to numerous showers in the mornings,
especially across northern and northeastern Puerto Rico, Vieques,
Culebra, and the U.S. Virgin Islands, along with a slight to
moderate chance of isolated thunderstorms. Additional activity is
also expected in the west-central and southwestern sections of
Puerto Rico as the day progresses. Consequently, there will be a
limited to localized elevated risk of flooding due to the potential
for ponding water on roadways, poorly drained areas, and urban and
small stream flooding.

Weather conditions are expected to gradually improve from Sunday
night onward as seasonal PWAT values return with the arrival of a
slightly drier air mass and the establishment of a ridge aloft. It
is worth noting that as the Three Kings Day approaches, it is
unlikely that significant disruptive weather events will occur
during the celebrations. On the morning of January 6th, both
residents and visitors in Puerto Rico and the U.S. Virgin Islands
can expect brief showers, primarily driven by residual moisture from
a recent cold front and the associated pre-frontal trough that
affected the region.

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

Overall, fair weather conditions will prevail over the long-term
period. The precipitable water content will fluctuate between normal
and below-normal levels (1.0-1.5 inches), with upper-level highs
building over the southeastern Caribbean. Two weak cold fronts are
forecast to reach the local area at the end of the workweek and late
Sunday, with associated upper-level troughs passing mainly north of
the area, providing only slight instability over the islands.
However, by midweek, as the surface high over the central Atlantic
moves further east and the pressure gradient relaxes over the
eastern Caribbean, a pre-frontal trough should develop mainly east
of the Leeward Islands, causing winds briefly to acquire an east to
southeasterly direction and become light to calm early in the
period. Moisture advection should favor showers over the USVI, but
minor rainfall amounts are expected with this activity. Moderate to
fresh NE to NNE winds will return by Thursday and Friday as the
front approaches the local area.

A similar weather pattern is expected during the weekend, as the
pressure gradient relaxes again on Saturday before the arrival of
the next front on Sunday. Pleasant temperatures will continue during
the forecast period, especially during clear nights with calm winds
and after the frontal passages.


&&

.AVIATION...
(06Z TAFS)

A frontal boundary over the Atlantic wtrs will continue sink
southwards across the local area. Increasing SHRA expected across
TJSJ, TJBQ, and the USVI terminals thru the rest of the morning
hours, with SHRA affecting TJPS after 04/16Z. This could result in
brief MVFR conditions with SCT-BKN ceilings btw FL025-050. Winds
will remain from the east-northeast at 6-12 kt, with higher gusts
and sea breeze influences, becoming more NNE-N and increasing aft
04/21z. SHRA and possible -TSRA expected across the Atlantic
waters and northern terminals of the islands during the
evening/nighttime.


&&

.MARINE...

Moderate east to northeasterly winds will prevail through this
morning as the surface high weakens over the central Atlantic and a
cold front with associated shearline approaches the area from the
northwest later this weekend. This will promote moderate to fresh
northeasterly winds through at least Monday. A long-period northeast
swell will continue to spread across the Atlantic waters and
passages through the rest of the weekend. A larger northwest swell
will arrive on Sunday and linger through early next week. The
combination of the swells with increasing winds will promote Small
Craft Advisory conditions due to hazardous seas across the local
waters through at least Tuesday.

Please refer to the latest Coastal Waters Forecast (CWFSJU) and
Marine Weather Message (MWWSJU) for additional information.


&&

.BEACH FORECAST...

A long-period northeasterly swell will continue to spread across the
local waters through the weekend. This swell will increase the risk
of life-threatening rip currents with rough surf conditions along
the northern exposed beaches of the islands. In addition, a larger
long-period northwesterly swell will arrive on Sunday and linger
through early next week, causing large breaking waves that will lead
to High Surf Advisory conditions, minor beach erosion, and life-
threatening rip currents, particularly along the Atlantic coastline
of Puerto Rico from Rincon to Fajardo, and Culebra. Across the U.S.
Virgin Islands, life-threatening rip currents will prevail across
all northern exposed beaches due to the long period swells.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
439 AM AST Sun Jan 5 2025

.SYNOPSIS...

Hazardous marine and coastal conditions will prevail for today
into Monday across the local waters and northern exposed beaches
of Puerto Rico, Culebra and the U.S. Virgin Islands. An increase
in cloudiness and moisture for today into tomorrow, will enhance
frequent light to moderate showers across the islands from the
rest of the morning into the night hours. Rainfall accumulations
can result in some pon ding of water in roadways and some low-
lying areas across northeastern sections of PR. By midweek, the
proximity of the frontal boundary will result in a variable
pattern, just before drier air moving in by Thursday.

&&

.SHORT TERM...Sunday through Tuesday...

During the overnight hours, scattered showers have been moving
through the northern and eastern sectors of Puerto Rico. Based on
radar estimates, the maximum rainfall accumulations range between
0.30 to 0.60 inches. In contrast, the USVI experienced calm
conditions. Northeasterly winds have persisted between 10 to 15 mph
with higher gusts. Pleasant temperatures prevailed across the area,
with surface observations recording minimum temperatures in the low
to mid 70s along the coast and in urban areas, while temperatures in
the mountains were mostly in the low 60s.

Expect marginally unstable, wetter, and breezy conditions today as
the synoptic pattern remains largely unchanged. A surface high-
pressure system will continue to establish itself over the
southwestern Atlantic while pushing an old frontal boundary toward
the region, causing moisture to pool across the area. According to
the latest model guidance, Precipitable Water (PWAT) values will
peak today, reaching up to 2 inches, which is two standard
deviations above normal for this time of year. We anticipate
scattered to numerous showers moving from the Atlantic waters
inland, primarily across northern municipalities. As a result, there
will be a limited to elevated risk of flooding due to the
possibility of ponding water on roadways and poorly drained areas,
as well as urban and small stream flooding, particularly across the
northern half of Puerto Rico.

From late tonight into Monday, PWAT values will return to seasonal
levels with the arrival of a slightly drier air mass and the
reestablishment of a ridge aloft. While trade wind showers and
limited afternoon development cannot be ruled out, no significant
impacts are expected through the remainder of the period. Pleasant
temperatures are anticipated over the coming days. Winds will remain
breezy from the northeast through at least Monday afternoon, then
become lighter and shift from the east Monday afternoon into Tuesday.


.LONG TERM...Wednesday through Friday...

On Wednesday and Thursday, a pre-frontal trough will influence
weather conditions across Puerto Rico and the U.S. Virgin Islands.
Variable winds dominating the region pushing patches of fragmented
moisture with precipitable water values of approximately 1.42
inches. This setup will favor the development of isolated to
scattered showers, with activity concentrated over coastal and
interior areas during the afternoon and evening hours. While
widespread rainfall is not anticipated, localized moderate rain
could result in brief ponding of water on roads, particularly in
urban or low-lying areas. By Friday, the FROPA will lead to a wind
shift from the north, signaling the arrival of a drier and cooler
air mass. This transition will bring a significant reduction in
atmospheric moisture, resulting in mostly dry conditions across
the region. The frontal passage will also create more stable
weather, limiting shower activity and offering relief from the
wetter conditions experienced earlier in the week.

Looking ahead to the weekend, a building high-pressure will
dominate the weather pattern. Winds will gradually shift to the
east-southeast (E-SE), bringing a return to typical trade wind
conditions. With this setup, isolated to occasional passing
showers are expected, mainly over windward areas during the night
and early morning hours. The overall rainfall coverage will remain
limited, with daytime hours predominantly with stable weather
conditions.

&&

.AVIATION...
(06Z TAFs)

Elevated moisture levels will continue to support SHRA across the
region today, primarily affecting TAF sites in northern Puerto Rico,
such as TJSJ and TJBQ. This pattern is expected to persist over the
next 24 hours and may lead to intermittent MVFR conditions.
Northeasterly winds are forecasted at 10 to 15 knots, with gusts
reaching 20 to 24 knots or higher at times.

&&

.MARINE...

Pulses of northerly swells and increased winds across the region
will result in confused seas today into the upcoming workweek. As
a result, hazardous marine conditions are expected across all the
local waters. Mariners can expect seas between 8 to 9 feet with 15
to 20 knots winds. Marine conditions will improve by late Monday
into Tuesday when winds diminish, becoming more light to moderate
from the east-northeast.

&&

.BEACH FORECAST...

Recent bouy data at San Juan PR shows that registered seas are up
to 6 feet and winds up to 17 knots for a period of 15 seconds.
These current conditions result in large breaking waves up to 10
feet across northern coastal areas of Puerto Rico, Culebra, and
the U.S. Virgin Islands. Therefore, hazardous coastal conditions
will persist across most exposed beaches for the rest of the
weekend into Monday. Residents and beachgoers are urge to remain
out of water today and tomorrow.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
523 AM AST Tue Jan 7 2025

.SYNOPSIS...

Isolated afternoon showers are expected over the western interior
of Puerto Rico this afternoon. A long period northerly swell will
continue to result in hazardous marine and coastal conditions
along all the northern coastal sides of the islands at least until
today. Variable conditions are anticipated over the next few
days, but the end of the week, the proximity of a frontal boundary
will enhance more frequent showers and northernly winds resulting
in fresh temperatures across the islands. After the front, expect
stable weather conditions during the weekend.

&&

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

Stable conditions prevailed across Puerto Rico and the U.S. Virgin
Islands due to a drier air mass dominating the region. Surface winds
prevailed from the east at 10 knots. Isolated showers were observed
over Caribbean waters and some eastern sections of Vieques.
Temperatures remained near seasonal normals, with the upper 70s to
lower 80s across coastal areas and much fresher in the mountains.

For today, synoptic conditions will remain influenced by a surface
high-pressure system anchored over the Central Atlantic. This
feature will sustain an east-northeast low-level flow, advecting
a relatively drier air mass into the region, as evidenced by
satellite-derived precipitable water values around 0.92 inches.
Diurnal heating and orographic lifting will lead to the
development of isolated afternoon convection over the western
interior of Puerto Rico, where weak sea breeze convergence is
anticipated. At 925 mb, model guidance indicates temperatures will
begin a warming trend today, with values increasing above
climatological norms as the wind flow veers to a southeasterly
component, enhancing warm air advection.

By Wednesday into Thursday, the approach of a pre-frontal trough
associated with a weak frontal boundary north of the region will
enhance a more showery pattern. Surface winds will weaken and become
more variable, allowing the presence of shallow patches of moisture.
This pattern will increase low-level convergence and frequent
showers, particularly during the overnight and early morning hours.
Widespread rainfall is not expected, with accumulations remaining
light and localized.

&&

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

The long-term period will be primarily characterized by stable
weather conditions. By Friday, winds are forecast to shift from
the north as a frontal system and its associated moisture move
southward through the area, bringing scattered showers throughout
the day. After the front passes late Friday, moisture levels will
gradually decrease. On Saturday, a much drier air mass and breezy
northerly winds, following the front's passage, will dominate the
region, leading to cooler and more stable weather throughout the
forecast period. Winds will slightly weaken from Sunday into the
beginning of the week, gradually veering more northeasterly.

Overall, the combination of limited moisture and the presence of a
mid-level ridge will create a trade wind cap inversion and drier
air aloft. These factors will suppress significant cloud
development and convective activity, ensuring stable weather
throughout the long-term period. As a result, expect mostly sunny
skies and minimal rainfall during the days.

&&

.AVIATION...
(06Z TAFS)

VFR conditions will prevail across all TAF sites during the
period. Winds will continue from the E at 10 knots, becoming more
from the E-SE at 01/15Z. VCSH is possible across TJBQ at around
07/20Z, lowering the ceiling and briefly affecting the VIS over the
mountains. Winds will diminish again around 08/00Z.

&&

.MARINE...

A surface high pressure moving into the central Atlantic will result
in moderate east-to-northeast winds through midday today. Winds are
then expected to weaken from this afternoon into the coming days. A
long-period northerly swell will continue to spread across the
Atlantic waters and passages, promoting hazardous seas for small
craft through at least the early afternoon hours today. Increasing
northerly winds are anticipated by the end of the week into the
weekend due to a frontal boundary.

&&

.BEACH FORECAST...

Life-threatening rip currents will continue across all north-
facing beaches of the islands through at least tonight due to the
lingering northerly swell. A moderate risk of rip currents is
expected to return tomorrow across the northern beaches of the
islands. Another long-period northerly swell will increase the
risk of life-threatening rip currents once again during the
upcoming weekend.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
518 AM AST Wed Jan 8 2025

.SYNOPSIS...

Today, an increase in moisture from the Caribbean accompanied by
light winds will lead to frequent passing showers during the
morning and additional showers development during the afternoon
hours over interior and northwestern Puerto Rico. The proximity of
a frontal boundary will promote more frequent showers and
northerly winds by the end of the week, resulting in fresh
temperatures across the islands. A stable weather pattern will
prevail through the weekend into early next week with drier
airmass dominating behind the front. A fading long-period
northerly swell and additional pulses will continue to result in
hazardous marine and coastal conditions across the Atlantic Waters
and the exposed north-facing beaches today and Thursday. Another
northerly swell will further deteriorate marine and coastal
conditions from Friday onward.

&&

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

During the overnight hours into the early morning, stable
atmospheric conditions prevailed across the region. However, some
passing showers affected the northern sections of Puerto Rico and
the Caribbean Waters. Winds persisted from the east at 10 knots or
less, maintaining calm conditions. Overnight temperatures were in
the low 80s across coastal areas, with slightly cooler readings
observed in the mountainous regions.

For today, an interesting weather pattern is unfolding as a
weakening surface high-pressure system becomes influenced by a pre-
frontal trough associated with an approaching frontal boundary to
the north of the region. This setup will result in light east-
southeast winds dominating much of the day. GOES-derived imagery
indicates an increase in moisture from the Caribbean, with
precipitable water (PWAT) values near 1.5 inches. This moisture
surge is expected to linger throughout the day, leading to frequent
passing showers in the morning and additional convective development
during the afternoon hours, particularly over interior and
northwestern Puerto Rico.

Looking ahead to Thursday and Friday, weather conditions will be
increasingly influenced by the pre-frontal trough moving into the
region. This feature will weaken the pressure gradient, resulting in
lighter and more variable winds. Pockets of moisture will persist
across the area, with the best potential for showers focusing over
the interior sections due to the lack of significant steering flow.
By Friday, global model guidance continues to support the passage of
the frontal boundary (FROPA). This pattern will introduce northerly
winds and much drier air, significantly improving overall weather
conditions and colder temperatures for the upcoming weekend.

&&

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

The long-term period will primarily be characterized by stable
weather conditions. On Saturday, a much drier air mass behind the
front will dominate the forecast area, leading to slightly cooler
and more stable weather throughout the period. With a surface
high-pressure system located to the north, winds will shift to
the northeast on Saturday and gradually weaken from Sunday into
the beginning of the week.

Overall, the combination of limited moisture and the presence of a
mid-level ridge, which creates a trade wind cap inversion, will
prevent significant rainfall. If any rain occurs, it will likely
be during the mornings in northern or eastern areas of Puerto
Rico. As a result, expect mostly sunny skies and minimal rainfall
during the day, providing favorable conditions for outdoor
activities. According to the latest model guidance, a weak front
will approach the region by midweek, slightly increasing northerly
to northeasterly winds and the probability of precipitation.
Pleasant temperatures are expected to prevail, daytime highs
should peak in the low to mid 80s along the coast and urban areas,
and in the low to mid-70s in the mountainous regions. Minimum
temperatures in the 70s and 60s across the same areas,
respectively.

&&

.AVIATION...
(06Z TAFs)

VFR conditions will persist for all the TAF sites during the
period. Winds will continue from the E-SE at 10 knots or less, with
sea breeze variation and some gusty winds near strong showers. VCSh
to -RA is forecast today across the interior, and that would result
in lower ceiling and VIS affecting some lower flight levels.

&&

.MARINE...

A cold front extending from the Western Caribbean into the Western
Atlantic will move southeastward, approaching the region around mid-
week. As the frontal boundary with its associated pre-frontal trough
approaches the islands, expect light to moderate winds from the
east-southeast today and Thursday. Behind the front, winds will turn
moderate to locally fresh from the north between late Thursday and
Friday, then return from the northeast by Saturday. A fading long-
period northerly swell is still spreading across the Atlantic waters
this morning and another pulse is expected tomorrow. By the end of
the week into the weekend, building seas are anticipated as a stronger
northerly swell spread across the local waters and passages.

&&

.BEACH FORECAST...

Beachgoers, breaking waves around 5 to 7 feet continues to create
life-threatening rip currents across the northern exposed
beaches of Puerto Rico, including Culebra, St. Thomas and St.
John in the U.S. Virgin Islands at least through this afternoon.
We encourage residents and visitors to monitor the forecast as
another pulse will likely continue to promote life-threatening rip
currents along the same areas and the risk will need to be
extended. By the end of the week into the weekend, a stronger
northerly swell spread across the local waters and passages
maintaining hazardous coastal conditions. The risk should remain
from low to moderate along southern protected beaches.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
450 AM AST Thu Jan 9 2025

.SYNOPSIS...

The arrival of a pre-frontal trough, followed by a frontal passage
(FROPA) on Friday, will enhance shower activity across the
region. Stable conditions are anticipated for the weekend and will
likely extend into early next week. At the same time, pulses of
northerly swells will continue to affect local waters and passages
through the end of the week, with stronger swells expected over
the weekend, further deteriorating marine and coastal conditions.
As a result, the threat of hazardous seas for small craft and
life- threatening rip currents for beachgoers will persist. A
cooling trend is also expected over the weekend and early next
week. For the latest updates on marine conditions, rip currents,
and other hazards, stay informed through our social media channels
and consult the Experimental Graphical Hazard Weather Outlook:
https://www.weather.gov/erh/ghwo?wfo=sju.

&&

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

Partly cloudy skies prevailed overnight, with showers over the
waters of the Caribbean just off the southern coast of Puerto Rico.
To the north, a line of showers developed and managed to move
inland, leaving nearly half an inch of rain between Quebradillas and
Camuy, according to radar estimates. Temperatures remained in the
70s in the coastal and urban regions, while the mountainous and
rural areas experienced cooler conditions in the 60s. Throughout the
night, variable and light winds persisted, generally ranging from 5
to 10 mph.

The synoptic pattern remains largely unchanged, and variable weather
conditions are expected to continue through the end of the week as a
pre-frontal trough approaches the area and lingers today. A frontal
passage (FROPA) is anticipated on Friday. Based on the latest model
guidance, precipitable water (PWAT) values will range from 1.3 to
1.5 inches, which are considered seasonal for this time of year.
Winds are expected to remain very light, with a surface col likely
near or over the forecast area today. As a result, very slow-moving
showers are anticipated, particularly after 2 p.m.. The latest
guidance suggests that up to half an inch of rain is possible across
the interior and southern Puerto Rico, while the U.S. Virgin Islands
should not experience much activity today. This will result in
limited risk of observing ponding of water in roads and poorly
drained areas.

Late tonight into Friday, an increase in wind speed and a shift in
wind direction from the north are expected as the front moves
through the area. After the FROPA, moisture content will notably
decrease, and a cool advective pattern will develop. PWAT values are
expected to drop to around 0.9 to 1.0 inch. By Saturday, as the
surface high-pressure system moves north and then northeast of
the region, winds will shift to the northeast on Saturday and then
to the east to east-northeast on Saturday night while weakening.
Meanwhile, a mid-level ridge will dominate. As a result, expect
mostly sunny skies, creating favorable conditions for outdoor
activities. In terms of temperatures, these factors will lead to
pleasant conditions across the islands, particularly on Friday and
Saturday, as reflected in the 925 mb temperatures, which are
forecast to drop to below-normal values.

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

Ideal weather conditions for outdoor activities will continue through
early next week. Northeasterly winds, influenced by a moderate
surface high pressure system moving eastward across the western-
central Atlantic, will continue to steer a drier-than- normal air
mass into the region. A mid-level ridge lingering over the
northern Caribbean will enhance atmospheric stability, with a
strong trade wind cap inversion and dry air entrainment persisting
through late Tuesday night. This pattern will maintain relatively
low precipitable water (PWAT) values between 0.9 and 1.2 inches,
suppressing rainfall activity and supporting primarily sunny and
clear skies.

By Wednesday, the ridge will drift westward toward the western
Caribbean, leading to a slight weakening of the trade wind cap
inversion, coinciding with a frontal boundary and pre-frontal
trough approach. This front will temporarily increase moisture,
with PWAT values rising to normal levels, around 1.4–1.5 inches.
Light to moderate rains are anticipated during the frontal passage
on Wednesday into Wednesday night; however, no significant
flooding impacts are expected. By late Wednesday night, drier air
will return following the frontal passage. With the
reestablishment of the mid-level ridge, moisture levels are
expected to drop back to below normal.

Winds will transition from light east to east-northeast on Sunday
to moderate northeast trades on Monday and Tuesday. With the
frontal passage, winds will shift to a northerly direction and
strengthen, leading to breezy to locally windy conditions by
midweek. A cooling trend is expected to prevail across the region,
as suggested by model- estimated 925 mb temperatures, with the
most noticeable cooling occurring late Wednesday night.


&&

.AVIATION...
(06z TAFs)

VFR conditions are expected to prevail across all terminals through
most of the period, but some SHRA are expected this afternoon,
mainly in TJPS. Intermittent periods of MVFR conditions are
anticipated. Winds are expected to remain light and variable aft
09/14z as a frontal boundary approaches from the northwest and a col
remain near or over the forecast area. Winds are forecast to
increase and become more northerly late tonight into Friday as a
frontal boundary push through the area. PROB30s have been added to
TJSJ and TJBQ for now due to the possibility to observe an increase
in showers after 10/03Z.


&&

.MARINE...

An approaching frontal boundary and associated pre-frontal trough
will yield light to locally moderate east-to-southeast winds
today. As the front crosses the local islands, winds will
gradually increase and turn from the north tonight into Friday and
from the northeast during the weekend. A fading long-period
northerly swell is still spreading across the Atlantic waters, and
another pulse is expected today. By the end of the week into the
weekend, building seas are anticipated as a stronger northerly
swell spreads across the local waters and passages.


&&

.BEACH FORECAST...

Rough and hazardous seas, driven by pulses of northerly swells,
will produce life-threatening rip current conditions along the
northern beaches of the U.S. Virgin Islands, Culebra, and Puerto
Rico today. As additional northerly swells move through the
region, these dangerous conditions are expected to persist through
the weekend and may extend to other surf zone areas. Furthermore,
stronger northerly swells could lead to large breaking waves,
warranting High Surf Advisories over the weekend. For more
information, please refer to the Coastal Hazard Message (CWFSJU)
and the Surf Zone Forecast (SRFSJU).

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
445 AM AST Sat Jan 11 2025

.SYNOPSIS...

Today's primary hazards arise from ongoing northerly swell action,
leading to hazardous seas for small craft, as well as life-
threatening rip currents and dangerous swimming conditions for
beachgoers along north-facing beaches. Minor coastal flooding is
also possible, threatening properties and structures near the
waterfront and shoreline. Meanwhile, stable weather with mostly
clear skies and limited rains is expected over the next few days,
followed by a wetter pattern beginning Tuesday and a cooling trend
into next week. Stay informed on marine conditions and hazards
through our social media channels and the Experimental Graphical
Hazard Weather Outlook: https://www.weather.gov/erh/ghwo?wfo=sju.

&&

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

During the night, partly cloudy skies prevailed, and no rain was
observed across the islands. The prevailing winds, as anticipated,
came from the north at speeds of 5 to 10 mph. Surface stations
recorded temperatures in the upper 60s to 70s in coastal and urban
areas, while the mountainous and rural regions experienced cooler
conditions, with temperatures in the low 60s at the time of writing
this discussion.

The short-term forecast remains on track, with the weekend expected
to feature mostly stable weather conditions and pleasant
temperatures. A surface high-pressure system, currently centered
near the Bahamas, will continue moving eastward across the Atlantic
and position itself north of our region today. As a result, the
winds will gradually shift from the northeast and become lighter
compared to yesterday.

Latest model guidance shows moisture levels well below normal for
this time of year. Precipitable water (PWAT) values are expected to
reach their lowest today, around 0.70 to 0.90 inches. For the
remainder of the short-term period, PWAT values are forecast to stay
in the 0.9 to 1.1 inch range through Monday. Additionally, a mid to
upper level ridge will dominate and enhance atmospheric stability,
with a strong trade wind inversion and a deep layer of dry air
persisting over our region. As a result, mostly sunny skies or a few
clouds are expected, providing ideal conditions for outdoor
activities through early next week. Model guidance suggests the
possibility of a shower or two this afternoon across west-central
Puerto Rico. If that materializes, it should be very light and
brief, with no significant accumulations.

In the wake of yesterday’s front passage and the drier airmass,
temperatures will remain pleasant across the islands throughout
the forecast period. The 925 mb temperatures are expected to dip
to below-normal values today and Sunday. The mountainous areas of
Puerto Rico are forecast to experience minimum temperatures
ranging from the mid to upper 50s. Coastal areas in Puerto Rico
and nearby islands may see temperatures in the low 70s or upper
60s tonight and over the coming nights. Daytime highs are expected
to reach the 80s in coastal and lower elevations, while the
mountains will see highs in the 70s.

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

Model guidance continues to indicate a transition to a wetter
pattern starting Tuesday, with the passage of a frontal boundary
and its associated pre-frontal trough. A steady moisture flow
from northeasterly winds is expected on Wednesday and Thursday,
followed by a more substantial influx of moisture originating from
the Gulf of Mexico and driven by a developing surface high
crossing into the southwestern Atlantic. However, the latest
guidance suggests lower-than-expected precipitable water (PWAT)
values, with peaks around 1.3 inches on Tuesday and 1.5 inches on
Thursday. These reduced moisture levels may respond to persistent
mid-level ridging and the associated trade wind cap inversion over
the northern Caribbean, inhibiting deep moisture from rising
above the 800 mbar layer, contrary to earlier expectations.

Increased shower activity is still anticipated throughout the
forecast period, with the most significant rainfall occurring as
moisture levels reach their peak. Potential flooding impacts are
possible from Thursday into Friday. A cooling trend is also
expected across the region, as indicated by model-estimated 925 mb
temperatures, with the most pronounced cooling occurring on
Wednesday. This cooling may be associated with the persistence of
northeasterly winds throughout the forecast period.

Confidence in this weather scenario is high early in the forecast
period. While discrepancies remain between global models regarding
the timing of peak moisture periods, confidence has increased for
the expected conditions during the second half of next week. Stay
tuned for updates as the forecast continues to evolve.


&&

.AVIATION...
(06Z TAFs)

VFR conditions are expected to prevail across all terminals through
the forecast period. Expect NE winds today at around 10 knots,
becoming lighter and somewhat variable late tonight.


&&

.MARINE...

A surface high-pressure moving eastward across the western
Atlantic will promote light to moderate east to northeast over the
next few days. Pulses of a long-period northerly swell will
combine with wind driven seas, maintaining hazardous marine
conditions for small craft through the weekend.


&&

.BEACH FORECAST...

A long-period northerly swell continues to move across the local
Atlantic waters and Caribbean passages, generating larger breaking
waves along the northerly exposed beaches of Puerto Rico, Vieques,
Culebra, and the U.S. Virgin Islands. Breaking wave heights are
expected to reach 13 to 15 feet, with occasional higher sets.
These conditions will result in life-threatening rip currents and
hazardous swimming conditions, with the potential for localized
beach erosion through the weekend. For more information, refer to
the Coastal Hazard Message (CWFSJU) and the Surf Zone Forecast
(SRFSJU).

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
444 AM AST Sun Jan 12 2025

.SYNOPSIS...

Long period northerly swells will continue to promote hazardous
marine and coastal conditions across exposed coastlines. The
Coastal Flood Advisory is now in effect through noon AST today,
while the High Surf Advisory is in effect through 6 PM AST this
evening and the High Risk of Rip Currents is in effect through
late tonight. Small Craft Advisories are also in effect for the
Atlantic Waters and Passages with most of them expiring this
evening as swells gradually subside today. Mainly fair weather
conditions will continue, before the arrival of a moisture band
associated with an old frontal boundary, on Tuesday.

&&

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

Radar and satellite imagery showed mostly clear skies overnight,
with minimal shower activity across the region. A few pockets of low-
level clouds passed over the islands but had little impact. Data
also suggested that fog developed in the higher elevations of the
Cordillera Central after midnight. Winds remained light to calm and
variable, including along coastal areas, where land breezes
dominated. Surface observing stations reported overnight lows
ranging from the upper 50s in the higher elevations of the
Cordillera Central to the mid-70s across northeastern Puerto Rico
and the local islands.

A mid-level ridge centered over Hispaniola will maintain stable
conditions across the region through Monday, with a strong trade
wind cap and drier air entrainment suppressing significant shower
activity. Precipitable water values will remain below normal, below
an inch, limiting moisture availability. Winds today will be light
from the east to northeast, gradually increasing and shifting to
north-northeast by Monday as a developing surface high-pressure
system moves over the southwestern Atlantic. By late Monday, breezy
conditions may begin to develop along the region.

By Tuesday, the ridge's influence will weaken slightly, and the
trade wind inversion will lift modestly as the mid-level ridge moves
farther west. This coincides with the arrival of a moisture band
associated with an old frontal boundary. Precipitable water values
will rise to around 1.5 inches, resulting in an increase in trade
wind showers, mainly affecting the U.S. Virgin Islands, Vieques,
Culebra, and northern Puerto Rico. Limited afternoon showers may
develop over the interior and southern Puerto Rico. North-northeast
winds will continue to strengthen, bringing breezy conditions along
coastal areas and aiding in moisture transport. By Tuesday night,
the mid-level ridge will drift eastward over the region, and
moisture levels will drop, bringing drier and more stable conditions.

Temperatures will continue their cooling trend, with overnight lows
in the 50s in higher elevations and valleys and 70s along the coast.
Daytime highs will reach the mid-80s. For updates on excessive
rainfall, winds, and other hazard risks in the coming days, please
visit the Experimental Graphical Hazard Weather Outlook at
https://www.weather.gov/erh/ghwo?wfo=sju.

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

Current model guidance has a frontal boundary already south and
well east of the islands to start the long term period with
northeasterly steering flow reaching the islands. On Wednesday,
gradually increasing precipitable water (PWAT) values is forecast,
however they will still remain at below normal to low end normal
values, around 1.2 in, with only slightly more humid patches
possible. A similar pattern is forecast on Thursday and early
Friday. Persistent mid-level ridging and a trade wind inversion
will continue to keep most available moisture below 800 mb through
this period. Northeasterly winds will also promote a cooler
temperatures across the islands, with model-estimated 925 mb
temperatures at below normal to normal values. Highs can reach the
low to mid 80s (locally higher) across lower elevation areas of
the islands. Lows can reach the mid 50s to mid 60s across higher
elevations of Puerto Rico, and from the upper 60s to mid 70s
across lower elevations of the islands. Patchy fog can also be
present during the overnight to early morning hours across sectors
of interior Puerto Rico.

With steering flow gaining a more easterly component, current model
guidance has remnants of the frontal boundary reaching the islands
from the east later on Friday and into Saturday, promoting above
normal, 1.5 in, precipitable water values and increased shower
activity. Potential flooding impacts are possible during these days.
Discrepancies between global models is present during the end of
the workweek and into the weekend, but potential flooding impacts
continue to be possible during these days as available moisture
increases and shower activity is steered into the area.

&&

.AVIATION...

(06Z TAFS)

VFR conditions with mostly clear skies will prevail. Minimal
SHRA/cloud cover will focus along the Cordillera Central/southern
PR, with limited to no operational impacts. Winds light/variable
overnight, increasing to E-NE at 8-10 knots with sea breeze
variations after 12/14Z, weakening again after 12/22Z.

&&

.MARINE...

A surface high-pressure moving eastward across the western Atlantic
will promote light to moderate east to northeast winds over the next
few days. Pulses of a long-period northerly swell will maintain
hazardous marine conditions for small craft today, as swells
gradually subside. Additional pulses of northerly swells are expected
by midweek.

For more information, please refer to the latest Coastal Waters
Forecast (CWFSJU & CWFSPN) & Marine Weather Message (MWWSJU).

&&

.BEACH FORECAST...

A long-period northerly swell continues to deteriorate nearshore
waters and coastal areas today, promoting breakers up to 15 feet
through noon, as it slowly subsides. A Coastal Flood Advisory is
now in effect through noon AST today for the beaches of northern
Puerto Rico, from Aguadilla to Rincon. A High Surf Advisory is in
effect through 6 PM AST this evening for the aforementioned areas
as well as the beaches of Aguadilla, Rincon, Vieques, Culebra and
the northern USVI. A High Risk of Rip Currents is in effect
through late tonight for the aforementioned areas as well as SW
Puerto Rico and St. Croix.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
454 AM AST Mon Jan 13 2025

.SYNOPSIS...

While current long-period northerly swells are subsiding,
additional pulses are expected by tomorrow and will once again
deteriorate marine and coastal conditions throughout the second
half of the week. On the other hand overall generally fair weather
an cooler than normal temperatures are forecast for today. Tomorrow,
the remnants of an old frontal boundary to bring light to
moderate rains steered by northeasterly winds to the U.S. Virgin
Islands, Vieques, Culebra, and northern/eastern Puerto Rico in the
morning and early afternoon, tapering off by evening. Remnants of
past frontal boundaries are also forecast to move into the local
islands late Friday and into Saturday.

&&

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

Radar and satellite imagery indicated mostly clear skies overnight,
with a few patches of low-level clouds moving across the region and
fog developing in the higher elevations of the interior after
midnight, likely affecting parts of highway PR-52 between Salinas
and Cayey. Although the broader wind flow remained from the
northeast, winds over land were light to calm and variable, with
land breezes dominating in coastal areas. Surface observations
showed overnight temperatures ranging from the mid-50s in the higher
elevations of the Cordillera Central to the lower 70s in coastal
areas and local islands.

A mid-level ridge drifting over the northern Caribbean will maintain
stable conditions throughout the period. Fair weather conditions are
expected today, with light to moderate northeast winds and minimal
to no shower activity. PWAT values will remain below normal, under
an inch. By Tuesday, the ridge's influence briefly weakens,
coinciding with the remnants of an old frontal boundary to bring
light to moderate rains from trade wind showers to the U.S. Virgin
Islands, Vieques, Culebra, and northern/eastern Puerto Rico in the
morning and early afternoon, tapering off by evening. Rainfall
totals will be around a quarter inch, with improving conditions
after sunset. Northeast to north-northeast winds will strengthen
late Tuesday, becoming breezy.

The ridge will stretch back into the northeastern Caribbean by
Wednesday, while another surface high will yield increased trade
winds and wetter conditions. Trade wind showers will affect windward
areas, particularly at nighttime, with rainfall totals ranging from
a quarter to half an inch. Breezy to windy conditions will persist
throughout the day. Overall, temperatures will generally remain
cooler-than-normal, with overnight lows in the 50s in higher
elevations and 70s along the coast and daytime highs in the mid-80s.
For more details, visit the Experimental Graphical Hazard Weather
Outlook at https://www.weather.gov/erh/ghwo?wfo=sju.

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

A surface high moving towards the western Atlantic will help
promote northeasterly steering flow to start the long term period.
Gradually increasing precipitable water (PWAT) values is
forecast, however they will still remain at below normal to low
end normal values before Friday, around 1.2 in to 1.3 in, with
only slightly more humid patches possible. Persistent mid-level
ridging and a trade wind inversion will continue to keep most
available moisture below 800 mb through most of the period.
Northeasterly winds will also promote a cooler temperatures across
the islands, with model- estimated 925 mb temperatures at below
normal to normal values. Maximum temperatures can reach the low to
mid 80s (locally higher) across lower elevation areas of the
islands. Minimum temperatures can reach the mid 50s to mid 60s
across higher elevations of Puerto Rico, and from the upper 60s to
mid 70s across lower elevations of the islands. Patchy fog can
also be present during the overnight to early morning hours across
sectors of interior Puerto Rico. With steering flow gaining a
more easterly component, remnants of past frontal boundaries are
forecast to move into the local islands from the east late Friday
and into Saturday, promoting above normal, 1.5 to 1.9 in,
precipitable water values and increased shower activity. Moisture
in this value will persist into the end of the long term period.
Limited flooding impacts continue to be possible during these days
as available moisture increases and shower activity is steered
into the area.

&&

.AVIATION...

(06Z TAFS)

VFR conditions with mostly clear to partly cloudy skies
will prevail. Increased cloud cover will focus along the Cordillera
Central and southern PR after 13/16Z, with minimal to no operational
impacts. Winds will be light to calm and variable overnight,
shifting from the NE and increasing to 10-12 knots with sea breeze
variations after 13/14Z, weakening after 12/23Z.

&&

.MARINE...

A surface high-pressure moving eastward across the western Atlantic
will promote light to moderate northeast winds over the next few
days. While current long-period northerly swells are subsiding,
additional pulses are expected by Tuesday and will once again
deteriorate marine conditions up to Small Craft Advisory criteria as
they spread across the Atlantic waters and local passages during the
second half of the workweek.

&&

.BEACH FORECAST...

While current long-period northerly swells are subsiding,
additional pulses are expected tomorrow, maintaining deteriorated
coastal condtions. A High Risk of Rip Currents will be in effect
today throughout the workweek for the beaches of northern Puerto
Rico, from Rincon to Fajardo, Culebra, St. Thomas and St. John. A
High Risk of Rip Currents is also forecast for St. Croix by
tomorrow night and last throughout the workweek. A High Surf
Advisory will possibly be issued for some exposed areas as we
approach the middle of the workweek.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
508 AM AST Tue Jan 14 2025

.SYNOPSIS...

Increased cloud coverage and some showers are expected today as a
weak old frontal boundary crosses the islands. However, only minor
shower activity is anticipated, with no flooding threat expected.
Hazardous seas and life-threatening rip currents will persist
through at least Thursday.
&&

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

It was a fair evening and overnight for the local islands, with no
precipitation over the islands detected by radar. Northeasterly
winds did steer patches of low level clouds over several inland
areas, and patchy fog was detected over areas of interior PR. Winds
over land were light to calm and variable, with land breezes in
coastal areas, except over several areas of Culebra, St. Thomas and
St. John where northeasterly flow was around 15 mph with higher
gusts. Surface observations showed overnight temperatures ranging
from the mid-50s in the higher elevations of the Cordillera Central
to the lower 70s in coastal areas and local islands. Lows were in
the mid 50s to mid 60s across higher elevations of Puerto Rico, and
in the upper 60s to mid 70s across lower elevations of the islands.

During the late overnight hours, the doppler radar detected isolated
showers over the offshore Atlantic Waters moving towards the local
islands. These are related to a weak frontal boundary approaching
the region that extends from a low pressure around 2500 mi NE of San
Juan. A surface high-pressure moving eastward across the SW Atlantic
will also continue to promote increasing NNE to NE flow. The mid
level ridge that has been affecting our area recently will weaken.
Current satelite derived precipitable water (PWAT) values indicate
up to 1.35 in (at normal values) with this boundary. Model guidance
has these PWAT values and related light to moderate shower activity
to reach the northern sectors in the morning and early afternoon,
and finally being south of the islands by the evening. This will
bring a moderate increase in shower activity, thus the potential for
flooding is very limited and conditions will further improve after
sunset. PWAT values will slightly decrease early Wednesday before
increasing to normal PWAT values through Thursday. NE winds,
becoming breezy, will also be present especially late tonight
through the short term period due to a surface high over the western
Atlantic. Passing showers will reach windward areas at times.
Persistent mid-level ridging and a trade wind inversion will
continue to keep most available moisture below 800 mb through the
short term period. Northeasterly winds will also promote slightly
below normal temperatures across the islands, with model-estimated
925 mb temperatures at below normal to normal values. Highs can
reach the low to mid 80s (locally higher) across lower elevations of
the islands. Lows can again reach the mid 50s to mid 60s across
higher elevations of Puerto Rico, and from the upper 60s to mid 70s
across lower elevations of the islands. Patchy fog can also be
present during the overnight to early morning hours across interior
Puerto Rico.

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

The low to mid-level ridge is expected to shift east-northeast of
the northern Leewards early in the cycle, allowing the trade wind
cap to relax over the weekend. At the same time, the remnants of a
frontal system south of the forecast area will move northwestward
over the local islands, increasing moisture convergence across the
northeastern Caribbean. Precipitable water values are expected to
increase to near-normal levels on Friday and above-normal levels
through the weekend.

The combination of increased vertical mixing and enhanced moisture
content will support shallow convection across the region. During
the morning hours of the weekend, showery weather could affect
windward coastal areas of the islands, while local effects and sea
breeze convergence may promote showers across the interior and
western portions of Puerto Rico in the afternoon. Warmer-than-normal
temperatures are also expected during this period as an east-
southeast wind flow develops, particularly on Sunday.

By Monday, the 500 mb ridge is forecast to move over the islands,
promoting drier air intrusion and stable conditions once again.
However, model guidance suggests the development of a mid-to upper-
level cut-off low on the southern edge of the ridge, which could
approach the area by Tuesday. Nonetheless, forecast confidence
remains low, as its location continues to vary with each model
cycle.


&&

.AVIATION...
(06Z TAFS)

Mainly VFR conditions are expected to prevail. Increased cloud cover
related to a frontal boundary will move in by around 14/10-15Z. NE
winds at 9-15 kts with higher gusts at 15-20 kts will also be
present. SHRA will move over the stations at times, from 14/10Z.
Very brief periods of reduced visibilities and low ceilings could be
anticipated. SRHA can concentrate along the Cordillera Central and
southern PR at around 14/17Z, continuing to move southwards after.


&&

.MARINE...

Breezy conditions are expected to develop by this evening across the
regional waters, with winds peaking between 15-20 knots and higher
gusts. Additionally, another long-period northerly swell will spread
across the Atlantic waters and portions of the local passages. This
will result in hazardous seas of 7-9 feet and choppy conditions due
to wind-driven seas. Consequently, a Small Craft Advisory (MWWSJU)
is in effect through at least Thursday afternoon.

&&

.BEACH FORECAST...

There is a high risk of rip currents across the northwestern,
northern, and eastern exposed beaches of Puerto Rico, Culebra, and
the northern U.S. Virgin Islands. As a result, a Rip Current
Statement is in effect. Life-threatening rip currents are expected
to persist through at least Thursday due to the combination of wind-
driven seas and pulses of a northerly swell. A High Surf Advisory
may be necessary during the peak of the northerly swell. For more
information, please refer to the SRFSJU and CFWSJU text products.

[cycloneye]

Area Forecast Discussion...DELAYED
National Weather Service San Juan PR
540 AM AST Wed Jan 15 2025

.SYNOPSIS...

The remnants of a set of frontal boundaries could promote increased
shower activity by this weekend. Hazardous marine and life-
threatening rip current conditions will continue.

&&

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

Fair weather was observed last night over region, except light
showers across the metro area before sunrise. Breezy northeasterly
winds steered patches of low level clouds and patchy fog was
detected over areas of interior PR. Stations reported lows ranging
from the 60s across higher elevations of Puerto Rico to the 70s
across lower elevations of the islands.

Current satellite derived precipitable water (PWAT) values were
between 1.05 to 1.15 in over the islands, below normal values for
this time of the year. A more humid airmass is also moving over
the Anegada Passage, south and east of St. Croix. Patches of
moisture with PWAT values around 1.4 in, at normal values, will
move into the eastern region tonight through Thursday, increasing
the chances of shallow passing showers during the overnight and
morning hours. Up to breezy NE winds will continue through
tomorrow as a surface high builds over the western Atlantic while
a ridge aloft will keep available moisture below 800 mb.

Tomorrow, highs can reach the low to mid 80s (locally higher,
especially over the SW quadrant of PR) across lower elevations of
the islands. Lows can decrease into the 60s across higher
elevations of Puerto Rico, and from the upper 60s to mid 70s
across lower elevations of the islands. Patchy fog can also be
present during the overnight to early morning hours across
interior Puerto Rico. As the low and mid level high moves eastward
over the Atlantic, steering flow will become more east-
northeasterly. As winds gain a more easterly component to end the
period, temperatures will slightly increase on Friday. Available
columnar moisture will start to climb towards 700mb on Friday
night. This coincides with frontal remnants south of the area that
will move over the islands. By Friday night and into the long
term period more showery weather is forecast for the eastern
region as these remnants move in. PWAT values are forecast to
increase to 1.5 to 1.7 in.

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

The long-term weather outlook remains unchanged, with minor
adjustments to the timing of moist and dry intervals. The weekend
will begin with increased moisture as remnants of a set of frontal
boundaries converge over the northern Caribbean. Indicators of low-
to mid-level moisture content, such as precipitable water, 700-500
mb, and 850-700 mb humidity, are expected to rise above the
climatological normals.

At upper-levels, a weak shortwave trough will cross the forecast
area on Sunday, reducing 250 mb height fields and bringing some cold
air advection aloft. The 500 mb temperatures will drop as low as -7
to -8C, which could lead to slightly steeper lapse rates. However,
mid-level ridging in the vicinity may still promote dry air
intrusion and stability over the northeastern Caribbean. Despite
this, environmental conditions will be conducive to at least shallow
convective activity.

The pressure gradient in the area will tighten, promoting breezy wind
conditions. Northeast winds on Saturday will gradually shift to east-
southeast by Sunday. Therefore, by early Saturday morning, expect a
cool advective pattern, bringing showery weather to northeastern
coastal areas of the islands, including the San Juan metro area. In
the afternoon, sea breeze convergence and local effects will trigger
shower activity across the interior and western portions of Puerto
Rico.

A similar pattern is expected on Sunday but under an east-southeast
steering wind flow. A limited flooding threat is anticipated
throughout the weekend, primarily across eastern and northeastern
Puerto Rico. Temperatures will also vary with wind and cloud
cover, with warmer-than-normal conditions likely this weekend,
particularly on Sunday, due to the influence of the east-southeast
wind flow.

The remainder of the long-term forecast features a seasonal weather
pattern as the mid-level ridge reestablishes itself over the region.
Shower activity will largely depend on patches of moisture moving
through the area. Precipitable water values are expected to
fluctuate between 1.0 and 1.6 inches. Consequently, anticipate a
mix of fair weather associated with dryer air and isolated to
scattered showers accompanying these moisture patches. However,
significant rainfall accumulations are not expected with any shower
activity.


&&

.AVIATION...
(06Z TAFS)

Mainly VFR conditions are expected to prevail. NE winds up to 15-20
kts with higher gusts up to around 25 kts will also be present.
Light and brief SHRA will move over the windward stations at times.


&&

.MARINE...

High pressure building across western Atlantic will support moderate
to fresh northeasterly trades through the workweek. Pulses of a
long- period northerly swell will continue to reach the regional
waters today. The combination of wind-driven seas and the long-period
northerly swell will maintain hazardous marine conditions across the
Atlantic waters and local passages for the next few days.

&&

.BEACH FORECAST...

Large breaking waves will result in localized beach/dune
structure erosion and dangerous swimming conditions. For more
information, please refer to the latest Coastal Hazard Message
(CFWSJU) and Surf Zone Forecast (SRFSJU).

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