Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
526 AM AST Mon Nov 20 2023

.SYNOPSIS...
.A line of showers and thunderstorms associated with an elongated
area of low pressure over the east central Caribbean, will continue
to slowly drift eastward across the Mona passage towards the west
coastal areas of Puerto Rico through this morning. This moisture
field will merge with a frontal trough/shearline just northwest of
the region, then sink southwards across the region Tuesday. In the
meantime,surface high pressure will build across the west and
southwest Atlantic resulting in the light southerly winds to
gradually become more northerly and increasing from Tuesday onwards.
Consequently an increase in low level moisture is forecast beginning
later today into Tuesday followed by a drier airmass thereafter.

&&

.SHORT TERM...Today through Wednesday...
Overnight, mostly calm weather conditions prevailed across Puerto Rico
and the U.S. Virgin Islands. Most of the rainfall and thunderstorm activity
associated with the area of low pressure located over the Central Caribbean
remained over the Mona Passage. However, some showers filtered along
the western and southern sections of Puerto Rico, and a line of passing
showers also moved over eastern PR, so far leaving minimal rainfall
accumulations. Temperature- wise, they remained in the low 80s along
the coastal areas, while across the mountainous areas, they stayed
in the 70s degrees Fahrenheit.

Today, we will transition from mostly dry conditions to a gradually
wetter pattern as the subsidence side of the trough moves north of
the region. As the moisture associated with the low-pressure system
over the Central Caribbean continues to move across the island,
expect showers to develop across PR and the USVI, particularly during
the afternoon and evening hours. The latest model guidance continues
to suggest mid to upper-level ridging and Saharan dust particulates
across the forecast area. At this time, the dust aerosol optical
depths are not foreseen to surpass 0.05, meaning that the concentrations
will not be significant enough to be included in the forecast as a slight
to moderate dust event. However, we encourage people with respiratory
problems to follow the recommendations of health experts. Today,the
wind flow will gradually become light and remain from the south-southwest.

On Tuesday, winds will become more northerly as a high-pressure ridge
builds across the southwestern Atlantic. This wind shift will bring
the remnant moisture associated with the surface low- pressure system
and the frontal shearline that will sink southwards across the area.
As a result, increasing low-level moisture is forecasted by Tuesday.
Therefore, expect to have the best potential for shower and isolated
thunderstorm development across the islands and coastal waters during
this time. We can not rule out an increased chance for excessive rainfall
in isolated areas and, thus, the potential for urban and small stream
flooding, water ponding on roads, and poor drainage areas.

By mid-week, dry weather conditions will return. Therefore, expect to
see a transition from wet/unstable conditions to dry/stable weather.
On Wednesday, expect the wind flow to gradually turn northeasterly
and easterly as the frontal boundary dissipates to the north of the
forecast area.

&&

.LONG TERM...Wednesday through Sunday...
Overall for the long term, model guidance has been consistent in
suggesting a gradual drying trend and more seasonal weather
pattern through the period. As a result no significant changes and
only minor adjustments were made to the forecast. The latest
model guidance suggests Wednesday to be the transition day from a
fairly wet and marginally unstable pattern to gradual drying and
stable weather conditions. Thereafter, expect the wind flow to
gradually increase and become more northeasterly due to the
proximity of a dissipating frontal boundary and surface trough
northeast of the region and building surface high pressure ridge
across the west and southwest Atlantic on Thursday. By then, the
surface high pressure will shift into the central Atlantic, and
thus favor a more east to southeast winds through the weekend.

All in all, a gradual erosion of columnar moisture is expected for
the long term, with precipitable water values dropping below seasonal
normal thresholds (below 1.5 inches) as additional patches of dry
air will filter in across the forecast area resulting in limited
shower activity and convective development for most of the period.
The overall decrease in precipitable water values will therefore
continue to lower the likelihood of significant rainfall across
the islands and consequently and diminish the risk of widespread
rainfall and flooding by the latter part of the period and into
the weekend.

Mostly fair weather and stable condition aloft is expected due to
the presence of a dominant high pressure ridge aloft along the
the surface ridging across the west and central Atlantic. However,
occasional passing trade wind showers can be expected across the
coastal waters and portions of the north and east coastal areas of
Puerto Rico and the U.S. Virgin Islands, followed by a more
seasonal and typical isolated to scattered afternoon convection
mainly across western PR and downwind of the u.s. Virgin islands,
due to daytime heating and sea breeze variations.

&&

.AVIATION...
VFR conditions across all terminals. Hazy skies will persist due
to suspended Saharan dust particulates across the region, but no
restriction to flight VIS is anticipated. Showers may impact
western PR with SHRA/Isold TSRA public btw 20/15-22z. Brief MVFR
conditions are possible during the afternoon hours, particularly
over TJBQ. SFC wnd mainly fm S-SW at 10 kt or less, increasing
between 10-20 kts aft 20/14z.

&&

.MARINE...
The marine and coastal conditions will remain choppy and hazardous
mainly over the Atlantic waters,local passages and north and east
facing beaches respectively. Overall conditions are forecast to
gradually improve today. However, the risk of rip currents will
continue to high particularly along the northwest to north and
east coastlines of Puerto Rico and for Culebra and St Croix.
Please refer to the latest Coastal Waters Forecast (CWFSJU) and
the Coastal Hazard Message (CFWSJU) issued by WFO San Juan PR for
the latest information.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
406 AM AST Tue Nov 21 2023

.SYNOPSIS...
A mid to upper level high pressure ridge will continue to build across
the region today to promote overall dry and stable conditions aloft.
A weak surface trough and elongated area of low pressure with axis
now extending across eastern Puerto Rico and into the north central
Atlantic, will continue to lift north and east of the region, as
a broad surface high pressure ridge will build and spread across
the region from the west and southwest Atlantic. This pattern will
induce a light southerly wind flow into the early morning hours,
then gradually become more northerly during the afternoon hours
and the rest of the week, in response to the surface ridge building
north of the region. This overall pattern will favor a gradually
erosion of moisture and a drier trend with a more seasonal pattern
across the area through the rest of the week.

&&

.SHORT TERM...Today through Thursday...
Tonight, mostly cloudy skies prevailed across Puerto Rico and the
U.S. Virgin Islands. Throughout the night, showers filtered along
the northern and eastern sections of Puerto Rico as well as over
Vieques, Culebra, and the U.S. Virgin Islands. This rainfall
activity left less than 1 inch of rain around the islands. Most of
this rainfall activity stayed over the Virgin and Anegada
Passage. Temperature-wise, they remained in the 70s along the
coastal areas, while across the mountainous areas, they ranged in
the low 70s to upper 60 degrees Fahrenheit. Overnight, the wind
flow was mainly out of the west-southwest. However, some weather
stations started reporting slightly northerly components.

Today, expect winds to shift northerly as a surface ridge continues
to build across the west-southwestern Atlantic. This northerly wind
shift will continue to bring the remnant moisture associated with
the elongated surface low pressure and the frontal shearline that
will sink southwards across Puerto Rico and the U.S. Virgin Islands.
As a result, expect an increase in low-level moisture across the
forecast area and the best potential for showers and some isolated
thunderstorm development across the islands and coastal waters
today. As mid to upper-level high-pressure ridges keep building
across the region, expect conditions to become dry aloft. Therefore,
the chances for significant rainfall and thunderstorm activity to
develop become limited. At this time, we anticipate ponding water on
roadways and poorly drained areas, as well as possible flooding in
urban and small streams.

&&

.LONG TERM...Friday through Tuesday...
On Friday, a patch of moisture from an old frontal boundary is
forecast to be transported across the region in the prevailing
east northeast wind flow. As a result expect a slight increase in
trade wind moisture especially during the overnight and early
morning hours on Friday. This will be followed by afternoon
showers developing across parts of the east, central and west
interior. However, no significant rainfall accumulations or
widespread shower activity is anticipated as the dominant weather
feature will be surface high pressure ridge anchored across the
north central Atlantic and a dominant mid to upper level ridging
in place across the forecast area. Recent model guidance continued
to suggest an overall dry and stable pattern during the rest of
the period with more seasonal weather conditions and the typical
passing morning showers, followed by mostly fair weather skies
each day. Otherwise expect some passing evening and early morning
trade wind showers along with the typical isolated to scattered
afternoon showers over parts of the interior and west sections of
Puerto Rico, and mainly downwind of the U.S. Virgin Islands. So
far with the expected east to northeast wind flow to continue, the
forecast calls for seasonal and near normal overnight and daytime
temperatures for the rest of the long term period.

&&

.AVIATION...VFR conditions across all terminals. Showers may impact
TJSJ, TISX, TIST, and TJBQ with +SHRA btw 21/15-19z. Brief MVFR
conditions are possible during this time. +SHRA for TJPS btw 21/18-
20z. SFC wnd mainly fm N at 10 kt or less, increasing between 10-20
kts aft 21/14z.

&&

.MARINE...

Recent observations from the surrounding and offshore buoys
suggest that the long- period north-northeast swell continued to
gradually fade over the regional waters and passages. Based on
these observations, estimated 4-6 foot breakers will continue to
to impact the northern surf zones. Therefore, a moderate risk of
rip currents will continue for these areas. Marine conditions
will slowly improve today, but seas and rip current risk will
again increase once again by Wednesday onwards. For additional
details on the current marine and surf zone risks, refer to the
Coastal Hazard Message (CFWSJU) and Marine Weather Message
(MWWSJU) and the Coastal waters Forecast (CWFSJU).

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
447 AM AST Thu Nov 23 2023

.SYNOPSIS...
Issued at 440 AM AST Thu Nov 23 2023

Due to a north-northeast swell, life-threatening rip currents
along the north and east-facing beaches in Puerto Rico and the
U.S. Virgin Islands will extend into the Thanksgiving weekend.
Fragmented moisture from an old frontal boundary will promote
showery weather across the windward sections. Seasonal
temperatures will prevail through the next few days.

&&

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

High pressure at the surface is regenerating a cold front boundary
near or just north of Puerto Rico and the U.S. Virgin Islands. This
is bringing a band of moisture across the area that is causing the
persistent passing showers in the trade winds flow from the
relatively weak high pressure that stretches across most of the
southwestern and south central portion of the subtropics. A weak
high pressure at 700 mb just northeast of the northern leeward
islands is also causing convergence along its southwest periphery
that will continue to favor showers over the forecast area through
Saturday. And, for now at least, this moisture will grow deeper
through Saturday as the very dry air present in the sounding last
night from 10-20 kft moistens slightly. Scattered showers will
continue through the period even though precipitable water drops
briefly overnight tonight.

Flow at the surface will remain east southeast until Saturday and
will help warm the temperatures on the north coast and keep the
south coast from overheating, but the passage of the previous front
is going to keep temperatures close to the monthly normal.

&&

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

A mid-level high pressure will linger across the Northeast
Caribbean, making challenging the vertical development to favor
thunderstorm formation. Therefore, we did not include thunderstorm
activity throughout the period. The trade winds will promote the
arrival of fragmented moisture with clouds and showers across the
windward sections on Sunday. Model guidance suggested the arrival
of the remnants of an old frontal boundary that may cause showery
weather around late Sunday night or Monday. However, if the
guidance is correct, we may see a mixture of sunshine and clouds
with pleasant temperatures on Sunday.

The rest of the long term will be at the mercy of what the wind
brings or an advective pattern. The surface high pressure building
across the Atlantic Ocean will promote the pattern, pushing
fragmented moisture to the Northeast Caribbean creating occasional
showery weather due to shallow rain showers. Depending on the
amount of humidity that arrives, there will be rainier days than
others. Finally, temperatures will turn more seasonal during the
long term, too.

&&

.AVIATION...
(06Z TAFS)
Issued at 440 AM AST Thu Nov 23 2023

Sct SHRA will cont ovr Culebra, Vieques and the ern coast of PR.
Aft 23/14Z these SHRA will spread across the rest of interior PR,
but SHRA will only affect TAF sites briefly. Mtn obscurations with
MVFR conds in SHRA, otherwise VFR. Sfc winds SE 8- 16 kt with HIR
gusts in weak sea breeze influences. Maximum winds nw 40-50 kts
btwn FL365-470.

&&

.MARINE...
Issued at 440 AM AST Thu Nov 23 2023

A north-northeast swell and locally wind-generated waves will
create hazardous marine conditions across the nearshore and
offshore Atlantic Waters and Caribbean Passages through the
weekend. Mariners can expect a north-northeast swell with a wave
period between 11 and 12 seconds and a height between 6 and 8
feet, with occasional seas up to 9 feet. The wind will be out from
the east to east northeast at 10 to 20 knots with locally higher
gusts.

.SURF ZONE...

Beachgoers, the north and east-facing beaches are not safe due to
life-threatening rip currents. Therefore, we have a high risk of
rip currents from Rincon to Aguadilla and eastward to Fajardo and
Culebra throughout the weekend. The risk will be high for the
beaches with the same orientation at St Thomas and St John through
early Saturday morning; then, we forecast a moderate risk.
Meanwhile, the risk will become high for the eastern half of St
Croix by this evening, lasting throughout the weekend.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
524 AM AST Sat Nov 25 2023

...New SYNOPSIS, AVIATION, MARINE...

.SYNOPSIS...
Issued at 430 AM AST Sat Nov 25 2023

The remnants of an old cold front are bringing scattered showers
to the area, but mid and upper levels are relatively dry and will
hinder deep convection. East southeasterly flow will continue to
bring slightly above normal temperatures to most of the forecast
area with Saint Croix continuing to be the warmest.

&&

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

An area of enhanced moisture is currently over the north and east
part of the region with a pocket of drier air elsewhere. Current
satellite derived precipitable water (PWAT) values indicate 1.5 to
1.8 inches over the more humid area, contrasted by values of 1.2
to 1.4 over the dry pocket in southwest Puerto Rico. The more
humid area, is due to remnants of an old frontal boundary, and will
continue to filter across the islands today. PWAT values should
stay in the range of 1.5 to around 1.9 inches, normal values for
this time of the year. Although decreasing, moisture will linger
on Sunday before drier air filters in. Current model guidance
indicates overall below normal PWAT values on Monday with only
patches of moisture reaching the islands. In the mid-levels, a
ridge extending cross the northern Caribbean will promote
unfavorable conditions for strong shower activity and continue to
affect our area throughout the short term period. This feature will
continue to generate a trade wind cap inversion during the short
term period. For today, moisture should be restricted to mostly
below 750 mb. At surface level, a weak high pressure over the
western Atlantic will promote east to east-southeast low level
winds. Low level winds are forecast to become more easterly on
Sunday. Trade wind showers will continue to affect windward
sectors of the islands today, this activity can lead to ponding of
water over roadways and low lying areas. Shallow convection is
also possible each afternoon, due to sea breeze convergence and
local effects, mainly over interior to western/northwestern Puerto
Rico. As moisture decreases Sunday and Monday and with the mid-
level ridge still in place, rain chances will also decrease.
Minimum temperatures should be in the 60s to lower 70s across
higher elevations of Puerto Rico and in the mid to upper 70s
across lower elevations of the islands. Maximum temperatures
should be in the upper 70s to low 80s across higher elevations of
Puerto Rico and in the upper 80s to low 90s across lower
elevations of the islands.

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

High pressure will continue north northeast of the area at low
and mid levels. This will allow drier air to maintain its
influence over the area and diminish the strength of the shower
activity. High pressure at upper levels, never far to the west,
will move across the forecast area on Tuesday to amplify the
effect. Moisture out of the tropical Atlantic to our east will
begin to affect the area on Thursday with increasing showers that
will approach the area from the northeast Friday and Saturday.
Since lower layers of the atmosphere will remain moist through
the period, minor isolated to scattered showers in the trade wind
flow will not falter.

&&

.AVIATION...
(06Z TAFS)
Mainly VFR conditions across the terminals. Shower activity will
affect eastern terminals at times, particularly TJSJ/TIST/TISX.
Afternoon SHRA may also affect TJBQ. After 25/13Z, generally E-ESE
winds up to 15 kts with locally higher seabreeze variations and
gusts before decreasing after 25/22Z. Maximum winds NW 33 kt
around FL430.

&&

.MARINE...
Issued at 430 AM AST Sat Nov 25 2023

The strong low pressures in the Atlantic are moving away from the
area and the swell are diminishing. At the same winds will ease
somewhat to allow seas to subside through Wednesday. Small craft
advisory conditions are not anticipated for the next 10 days. A 3
foot swell from the north northwest will approach the area on
Friday. The risk of rip currents will continue through late
tonight, but rip current risk becomes moderate on Sunday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
519 AM AST Sun Nov 26 2023

...New SYNOPSIS, AVIATION, MARINE...

.SYNOPSIS...
Issued at 442 AM AST Sun Nov 26 2023

High pressure building into the western Atlantic will maintain
moderate occasionally fresh easterly trade wind flow. Generally
shallow moisture will bring scattered but persistent showers with
light to moderate rainfall. After the drier days of Monday through
Thursday, some moisture will return to the area. Temperatures
will cool slightly to near normal levels today and tomorrow.


&&

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

Current satellite derived precipitable water (PWAT) data indicates,
an area of enhanced moisture, the remnants of an old frontal
boundary, over our area and slowly moving westward under easterly
winds. Normal PWAT values can be observed over the region,
ranging from 1.5 to 1.8 inches. This moisture will linger
throughout the day while slowly filtering out of the area. Model
guidance indicates, an area of drier air, with PWAT values only up
to 1.4 inches filtering into the USVI by noon, and decreasing
thereafter. This drier air should reach western Puerto Rico late
tonight. Current model guidance indicates overall below normal
PWAT values tomorrow and Tuesday, with only patches of moisture
reaching the islands. A mid-level high pressure system across the
northern Caribbean will continue to dominate during the short term
period. This feature will promote unfavorable conditions for
strong shower activity. With this feature, most available moisture
will be restricted to below 800 mb with drier air aloft. At
surface level, a weak high pressure over the western Atlantic will
promote generally easterly winds. The bulk of a Saharan Air Layer
is expected to stay south of the local islands, over the
Caribbean Sea. An advective pattern will still dominate with trade
wind showers affecting windward sectors of the islands. Shallow
convection is also possible each afternoon, developing over
interior to western Puerto Rico due to sea breeze convergence and
local effects. With below normal PWAT values Monday and Tuesday, a
more limited variation of this pattern will prevail. Lows should
be in the lower 60s to lower 70s across higher elevations of
Puerto Rico and in the mid to upper 70s across lower elevations of
the islands. On the other hand, highs should be in the upper 70s
to low 80s across higher elevations of Puerto Rico and to low 90s
across lower elevations of the islands.

.LONG TERM...Tuesday through Saturday... from previous discussion
issued at 524 AM AST on Sat 25...

High pressure will continue north northeast of the area at low
and mid levels. This will allow drier air to maintain its
influence over the area and diminish the strength of the shower
activity. High pressure at upper levels, never far to the west,
will move across the forecast area on Tuesday to amplify the
effect. Moisture out of the tropical Atlantic to our east will
begin to affect the area on Thursday with increasing showers that
will approach the area from the northeast Friday and Saturday.
Since lower layers of the atmosphere will remain moist through
the period, minor isolated to scattered showers in the trade wind
flow will not falter.

&&

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

Surface high pressure will move off the eastern seaboard of the
United States on Wednesday. As it fills in the western Atlantic
it will also spread into the central Atlantic and build. This will
cause trade wind flow to increase Friday and Saturday. Patches of
moisture will also move into the area on Friday on east northeast
flow. So whereas Monday through Thursday were relatively dry,
moisture will increase considerably Friday and Saturday and remain
through the weekend, especially at lower levels. Instability will
also increase somewhat on Saturday such that isolated
thunderstorms cannot be ruled out. Flow at lower levels remains
east northeast or northeast during the period. Mid to upper levels
however will remain somewhat dry causing amounts to be generally
light to moderate.

At upper levels, high pressure will remain in the southwestern
Caribbean with mostly northwest to north flow over the local area.
This will also hinder deep convection and the production of heavy
rainfall.

&&

.AVIATION...
(06Z TAFS)
Issued at 442 AM AST Sun Nov 26 2023

Mainly VFR conditions across the terminals. Shower
activity will affect eastern terminals at times, particularly
TJSJ/TIST/TISX. Afternoon (26/16Z) SHRA may also affect TJPS/TJBQ
and produce mtn obscurations. After 26/13Z, generally E winds up
to 15 kts with locally higher in seabreeze variations and gusts
before decreasing after 26/22Z.

&&

.MARINE...
Issued at 442 AM AST Sun Nov 26 2023

Seas and swell will continue to subside until Thursday when small
craft conditions--mainly seas--will return to our northern waters.
Small craft will need to exercise caution in the outer Atlantic
waters today. The risk of rip currents will remain high only in
Culebra today and all beaches with northern exposures will have a
moderate risk of life threatening rip currents Monday and Tuesday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
510 AM AST Mon Nov 27 2023

.SYNOPSIS...

Current satellite derived precipitable water (PWAT) data shows a
dry air mass over our region with values of 1.0 to 1.3 inches. A
broad mid level ridge extending over the local area will keep most
of the moisture below 800mb. Overall fair weather conditions are
expected through at least midweek with only minor rainfall
accumulations. PWAT values are forecast to gradually increase to
normal values as we head into next weekend. A lingering but
slowly fading northeast swell will persist through early tomorrow
and help promote up to moderate risk of rip currents today,
particularly for the northern coastline of Puerto Rico, from
Rincon to Ceiba, as well as for most of the coastline of Vieques,
Culebra and the USVI.

&&

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

Minimum temperatures were between the low to mid 70s across the
lower elevations, and from the low to mid 60s across the higher
elevations. Low-level cloudiness with light showers were increasing
across the regional waters from the east, with a few moving over
portions of the U.S. Virgin Islands, leaving little rainfall
accumulations over land areas. Similar conditions are expected by
sunrise across the eastern sections of Puerto Rico.

A broad mid-level ridge extending over the local area from the
central Caribbean will promote fair weather conditions through the
rest of the short term period across the islands. The best moisture
content will remain below 800mb, while the mid and upper atmosphere
will remain unfavorable for the vertical development of afternoon
showers over the islands each day. Minor rainfall accumulations are
anticipated across the islands. The wind will prevail from the east
at 10 to 15 mph, with higher gusts and sea breeze variations along
coastal areas. Max temps should range from the mid to upper 80s in
general across the lower elevations of the islands to the mid 70s
across the higher elevations of Puerto Rico.

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

A surface high pressure system will build north of the islands,
while the mid-level ridge extending over the local area will
continue to affect us through most of the period. Current model
guidance suggest below normal precipitable water (PWAT) values to
start the period, with only patches of moisture reaching the
region at times. PWAT values are forecast to gradually increase to
normal values, and up to high end normal values, as moisture from
the tropical Atlantic filters into the area. This will promote
increasing shower activity from the east and northeast,
particularly on Friday onwards. Most available moisture should
remain below 800 mb, with drier air aloft. Passing showers will
continue to be a factor across windward sectors of the islands.
Diurnal and local effects will also help promote afternoon
convection across interior to sectors of the western half of
Puerto Rico.

&&

.AVIATION...
Mainly VFR conditions are expected across all terminals during
the next 24 hours. SCT-BKN cigs btw FL040-FL060 expected thru
early this morning across the USVI and eastern PR terminals.
Low-level winds E-ENE at 15-20 kt.

&&

.MARINE...
A surface high pressure building across the Atlantic will promote
moderate easterly winds. Seas up to 6 feet across sectors of the
offshore Atlantic Waters during the day. Seas up to 4-5 feet
across the rest of the local waters with the exception of the
nearshore southern and southwestern coastal waters, where seas
will be up to 3 ft. Tonight onwards, seas will be up to 5 ft,
before conditions deteriorate by the end of the workweek. A
lingering but slowly fading 4 ft northeast swell will persist
through early tomorrow.

This lingering NE swell will continue to promote up to moderate
risk of rip currents today, particularly for the northern
coastline of Puerto Rico, from Rincon to Ceiba, as well as for
most of the coastline of Vieques, Culebra and the USVI.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
508 AM AST Tue Nov 28 2023

.SYNOPSIS...
Current satellite derived precipitable water (PWAT) data shows a
dry air mass over our region with values of 0.95 to 1.45 inches.
Ridging at all levels will continue to promote fair weather
conditions across the local area through at least the rest of the
workweek. Therefore, little to no significant shower development
is anticipated. Moisture will recover to normal values during the
weekend. Near normal and seasonal temperatures will prevail.


&&

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

Minimum temperatures were between the low to mid 70s across the
lower elevations, and from the low to mid 60s across the higher
elevations. Light passing showers and low-level cloudiness were
observed across portions of the islands during the night hours.
Rainfall accumulations over land areas were just a few hundredths of
an inch, mainly over southeastern Puerto Rico. Sunny to partly
cloudy skies are expected to prevail across the region throughout
the day.

Ridging at all levels will continue to promote fair weather
conditions across the local area through the short term period.
Sinking drier air and relative warm 500 mb temperatures due to a
broad mid-level ridge over the central Caribbean should continue to
promote stable conditions today across the islands. The best
moisture content is trapped below 850 mb and it was mainly due to
the fragmented cloud layer around 5000 ft that moved over the
region from previous days. The precipitable water content is
expected to remain below normal levels, around 1.30 inches,
decreasing further to 1.10 inches by Wednesday morning. Therefore,
little to no significant shower development is anticipated. Moisture
recovers slightly on Thursday, but only isolated to scattered
showers are expected as the region remains under the influence of
the ridge.

&&

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

Current model guidance suggests below normal precipitable water
(PWAT) values on Friday, although with patches of moisture reaching
the region. By Saturday, moisture is forecast to increase to normal
values as moisture from the tropical Atlantic filters into the area.
This trend is forecast to continue through the rest of the period
with the exception of a dry patch on Sunday. A mid level ridge will
start over the northern Caribbean to start the period before
gradually moving westward and weakening during the weekend. At
surface level, a high pressure will build north of the islands over
the western Atlantic, gradually moving eastward through the period.
Most available moisture should remain below 800 mb, with drier air
aloft through most of the period, although slightly more humid air
aloft is present Friday and Saturday, as a nearby polar trough and a
lower level weak front approaches the region. As moisture increases
the chance of passing showers across windward sectors of the islands
will increase. Sea breeze convergence, diurnal heating and local
effects will also help promote afternoon convection across interior
to sectors of the western/southwestern half of Puerto Rico, under
east-northeast low level winds, during most of the period.

&&

.AVIATION...Mainly VFR conditions are expected across all
terminals during the next 24 hours. Winds from the east at 10-15
knots with sea breeze variations aft 28/14z.

&&

.MARINE...

A surface low with associated frontal boundary moving
northeastward across the Western Atlantic and a high pressure
ridge north of the region, will promote gentle to moderate
easterly winds across the Northeast Caribbean. Another surface
high pressure is forecast to build from the western to central
Atlantic, promoting moderate to locally fresh winds and choppy
seas by Thursday or Friday. Seas will be up to 5 ft before
conditions deteriorate by the end of the workweek. A lingering but
slowly fading NE swell will persist through today. Current
CARICOOS buoys report seas at 2-3 ft with San Juan's, Arecibo's
and Rincon's buoys reporting a 12-13s swell.

There is a moderate risk of rip currents for the northern coastline
of Puerto Rico, from Rincon to Ceiba, most of Culebra's coastline,
northwestern St. Thomas and easternmost St. Croix. Low risk
elsewhere.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
443 AM AST Wed Nov 29 2023

.SYNOPSIS...
A mid-to upper-level ridge over the Caribbean basin will continue
to promote fair weather conditions across the region through at
least Thursday. Drier mid-level air, warm 500 mb temps and stable
conditions will result in shallow layer cloud development and
occasional light showers during this time. An increase in moisture
and winds, as well as deteriorating marine conditions are
expected by Friday and into the weekend.

&&

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

Minimum temperatures were once again in general between the low to
mid 70s across the lower elevations, and from the low to mid 60s
across the higher elevations. Little to no rainfall was detected
over land areas through the early morning hours. Mostly sunny to
partly cloudy skies are expected to prevail across the islands
during today.

A mid-to upper-level ridge over the Caribbean basin will continue to
promote fair weather conditions across the region through at least
Thursday. Drier mid-level air, warm 500 mb temps, and overall stable
conditions are expected to inhibit shower development across Puerto
Rico and the U.S. Virgin Islands during the next few days. Shallow
layer cloud development and light showers are expected at times
through this period. By Friday, a wind surge is expected across the
area as a strong low-level ridge is expected to develop over the
western Atlantic, while an upper level trough and associated frontal
boundary brings an increase in moisture content from the Atlantic
waters. Therefore, isolated to scattered showers should increase on
Friday across the area.

&&

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

Little changes to the long term forecast. Current model suggest an
increase in moisture, to normal precipitable water (PWAT) values, to
start the weekend. According to current model guidance, the driest
period would be on Sunday evening to early Monday morning, as a dry
patch moves over the region, lowering PWAT values to below normal. A
mid level ridge will move westward and weaken to start the period,
strengthening again by the end of the period. At surface level, a
high pressure will be established north of the islands over the
western to central Atlantic, gradually moving eastward through the
period, and being more confined to the tropical Atlantic. Most
available moisture should remain below 800 mb. Slightly more humid
air aloft is present Friday and Saturday, as a nearby polar trough
and a lower level weak front approaches the region. For Sunday
onwards, drier air is forecast aloft. East-northeast winds are
forecast for the weekend, becoming more easterly to start the next
workweek. As moisture increases the chance of passing showers across
windward sectors of the islands will increase, as well as afternoon
convection, fueled by local effects. For the weekend, afternoon
convection should affect interior to western/southwestern Puerto
Rico, under east-northeast winds.

&&

.AVIATION...Mainly VFR conditions are expected across all terminals
during the next 24 hours. Winds from the east increasing after
29/14z between 10 and 15 knots with sea breeze variations.

&&

.MARINE...

CARICOOS buoys are currently reporting seas of 2-3 ft across
nearshore waters. A surface low with associated frontal boundary
moving northeastward across the Western Atlantic and a high
pressure ridge north of the region, will promote gentle to
moderate easterly winds across the Northeast Caribbean. Then,
another surface high pressure is forecast to build from the
western to central Atlantic, promoting moderate to locally fresh
winds and choppy seas around late Thursday or Friday. Seas will
be up to 5 ft before conditions deteriorate by the end of the
workweek due to the arrival of a northerly swell and increasing
trade winds.

There is a moderate risk of rip currents for the northern
coastline of Puerto Rico, from Rincon to Fajardo, and Culebra,
as well as for northwestern St. Thomas. Low risk elsewhere.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
513 AM AST Thu Nov 30 2023

.SYNOPSIS...
A surface high pressure will build across the central Atlantic
during the next few days. This will promote moderate to fresh
trades through at least Saturday. An increase in moisture and
winds, as well as deteriorating marine conditions are expected by
Friday and into the weekend. A weak trough should increase shower
activity by Monday.


&&

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

Mostly clear to partly cloudy skies skies with only few passing
early morning showers noted so far over the coastal waters and
along portions of the north and east coastal sections of Puerto
Rico. For the rest of the morning, periods of quick passing showers
may reach these areas as well as the coastal waters of the U.S.
Virgin Islands. However, no significant rainfall accumulations are
forecast. This will be followed by limited locally and diurnally
induced afternoon showers in isolated spots around the islands.
Recent model guidance along with satellite imagery and both TJSJ
(San Juan)and TNCM (St Maarten)30/00Z upper air sounding suggested
precipitable water values of 1.27 and 1.15 inches respectively.
Therefore an overall dry airmass will persist across the region.
Minimum temperatures so far were between the low to mid 70s along
the coastal areas, and in the low to mid 60s in the higher
elevations and valleys. Overall fair weather skies and breezy
conditions along the coastal areas can be expected in most areas
today.

For the rest of the period, a mid-to upper-level ridge will remain
anchored across the forecast area. The ridge will slightly erode by
Friday through Saturday, as an upper level trough will shift
eastward just north of the region before settling and become
elongated across the northern Leeward Islands on Saturday.
Meanwhile, an associated frontal boundary and moisture field will
gradually sink southwards towards the region and bring an increase
in moisture while being steered by the moderate to locally strong
east to northeast winds. The ridge aloft will aid in maintaining
stable and dry conditions aloft thus limiting convective
development.

Moisture transport is forecast to increase Friday through Saturday,
in response to the tightening of the local pressure gradient as the
surface high pressure builds across the west and central Atlantic,
resulting in an increase in the trade winds along with the expected
surge of moisture from the aforementioned frontal boundary. Some of
the shower activity will be enhanced by the elongated upper trough
just east of the region especially during the overnight and early
morning hours. This additional low level moisture will also support
the best chance for isolated to scattered shower activity during
late afternoon. The shower activity should be focused mainly over
parts of the interior and west to southwest sections of Puerto Rico.
Isolated showers may also affect the U.S. Virgin islands but most of
the shower activity if any should be fast moving and of short
duration. Ponding of water on roads and in poor drainage can be
expected with the periods of moderate to locally heavy rains.
Excessive rainfall risks are however not anticipated with this
activity. Local temperatures will be near the seasonal values with
mostly clear and cool nights except for the quick passing overnight
showers followed by sunny conditions during most of the day.

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

A TUTT-low is expected to develop over the eastern Caribbean early
in the workweek and the local area should remain on the subsidence
side of the low during the first part of the week. However, as the
upper level trough deepens over and to the east of the area, a
jet maxima of around 70 kt rounding the base of the trough will
move over the local area on Sunday. In response the 500 mb
temperature is expected to drop near minus 7.5 degrees Celsius,
providing some instability aloft. In addition, at lower levels,
the remnants of the frontal boundary will be pushed over the local
area by the broad surface high over the central Atlantic between
Sunday and Monday. Global models suggest that a weak surface
trough will move over the area during this period. Therefore,
shower activity should increase in coverage over the islands, but
flooding rains are not expected. Otherwise, fair weather
conditions should prevail from Tuesday onwards.


&&

.AVIATION...
VFR durg the prd. Mstly Isold SHRA ovr regional waters
and en route btw local islands with shallow cld lyrs nr FL025...
FL050. Prob30 due to VCSH/ISOLD SHRA mainly ovr eastern PR and
coastal waters en route to the USVI til 30/12Z. Wnd calm to
lgt/vrb...bcmg fm E-NE 12-18 kts with ocnl hir gusts and sea breeze
variations aft 30/14Z.

&&

.MARINE...
A cold front will continue north of the region during the next few
days. A broad surface high pressure building behind the front
will promote moderate to locally fresh trades across the regional
waters through at least Saturday. Wind-driven seas and a northerly
swell will promote hazardous seas around 7 feet across portions of
the Atlantic waters and passages during the weekend.

There is a moderate risk of rip currents for the northern coastline
of Puerto Rico, from Aguadilla to Fajardo, and Culebra, as well
as for eastern St. Croix. Elsewhere, there is a low risk today.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
513 AM AST Thu Nov 30 2023

.SYNOPSIS...
A surface high pressure will build across the central Atlantic
during the next few days. This will promote moderate to fresh
trades through at least Saturday. An increase in moisture and
winds, as well as deteriorating marine conditions are expected by
Friday and into the weekend. A weak trough should increase shower
activity by Monday.


&&

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

Mostly clear to partly cloudy skies skies with only few passing
early morning showers noted so far over the coastal waters and
along portions of the north and east coastal sections of Puerto
Rico. For the rest of the morning, periods of quick passing showers
may reach these areas as well as the coastal waters of the U.S.
Virgin Islands. However, no significant rainfall accumulations are
forecast. This will be followed by limited locally and diurnally
induced afternoon showers in isolated spots around the islands.
Recent model guidance along with satellite imagery and both TJSJ
(San Juan)and TNCM (St Maarten)30/00Z upper air sounding suggested
precipitable water values of 1.27 and 1.15 inches respectively.
Therefore an overall dry airmass will persist across the region.
Minimum temperatures so far were between the low to mid 70s along
the coastal areas, and in the low to mid 60s in the higher
elevations and valleys. Overall fair weather skies and breezy
conditions along the coastal areas can be expected in most areas
today.

For the rest of the period, a mid-to upper-level ridge will remain
anchored across the forecast area. The ridge will slightly erode by
Friday through Saturday, as an upper level trough will shift
eastward just north of the region before settling and become
elongated across the northern Leeward Islands on Saturday.
Meanwhile, an associated frontal boundary and moisture field will
gradually sink southwards towards the region and bring an increase
in moisture while being steered by the moderate to locally strong
east to northeast winds. The ridge aloft will aid in maintaining
stable and dry conditions aloft thus limiting convective
development.

Moisture transport is forecast to increase Friday through Saturday,
in response to the tightening of the local pressure gradient as the
surface high pressure builds across the west and central Atlantic,
resulting in an increase in the trade winds along with the expected
surge of moisture from the aforementioned frontal boundary. Some of
the shower activity will be enhanced by the elongated upper trough
just east of the region especially during the overnight and early
morning hours. This additional low level moisture will also support
the best chance for isolated to scattered shower activity during
late afternoon. The shower activity should be focused mainly over
parts of the interior and west to southwest sections of Puerto Rico.
Isolated showers may also affect the U.S. Virgin islands but most of
the shower activity if any should be fast moving and of short
duration. Ponding of water on roads and in poor drainage can be
expected with the periods of moderate to locally heavy rains.
Excessive rainfall risks are however not anticipated with this
activity. Local temperatures will be near the seasonal values with
mostly clear and cool nights except for the quick passing overnight
showers followed by sunny conditions during most of the day.

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

A TUTT-low is expected to develop over the eastern Caribbean early
in the workweek and the local area should remain on the subsidence
side of the low during the first part of the week. However, as the
upper level trough deepens over and to the east of the area, a
jet maxima of around 70 kt rounding the base of the trough will
move over the local area on Sunday. In response the 500 mb
temperature is expected to drop near minus 7.5 degrees Celsius,
providing some instability aloft. In addition, at lower levels,
the remnants of the frontal boundary will be pushed over the local
area by the broad surface high over the central Atlantic between
Sunday and Monday. Global models suggest that a weak surface
trough will move over the area during this period. Therefore,
shower activity should increase in coverage over the islands, but
flooding rains are not expected. Otherwise, fair weather
conditions should prevail from Tuesday onwards.


&&

.AVIATION...
VFR durg the prd. Mstly Isold SHRA ovr regional waters
and en route btw local islands with shallow cld lyrs nr FL025...
FL050. Prob30 due to VCSH/ISOLD SHRA mainly ovr eastern PR and
coastal waters en route to the USVI til 30/12Z. Wnd calm to
lgt/vrb...bcmg fm E-NE 12-18 kts with ocnl hir gusts and sea breeze
variations aft 30/14Z.

&&

.MARINE...
A cold front will continue north of the region during the next few
days. A broad surface high pressure building behind the front
will promote moderate to locally fresh trades across the regional
waters through at least Saturday. Wind-driven seas and a northerly
swell will promote hazardous seas around 7 feet across portions of
the Atlantic waters and passages during the weekend.

There is a moderate risk of rip currents for the northern coastline
of Puerto Rico, from Aguadilla to Fajardo, and Culebra, as well
as for eastern St. Croix. Elsewhere, there is a low risk today.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
508 AM AST Fri Dec 1 2023


.SYNOPSIS...
Issued at 450 AM AST Fri Dec 1 2023

Coastal and marine conditions will deteriorate today through the
weekend due to the combination of increasing winds and northerly
swells. Breezy wind conditions and showery weather expected
through the weekend, mostly over windward coastal areas of the
local islands.

&&

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

Minimum temperatures were between the mid to high 70s across the
lower elevations, and from the low to mid 60s across the higher
elevations of Puerto Rico. Passing showers were noted along the
northern and eastern sections of PR, as well across the U.S. Virgin
Islands through the night. Rainfall accumulations were less than a
tenth of an inch in general. Sunny to partly cloudy skies are
expected to prevail across the islands through the morning hours.
Breezy conditions are expected, and passing trade wind showers could
move at times across the islands throught the day.

A cold front just north of 22N will gradually sink southwards during
the next couple of days, and moisture advection will promote shower
activity across the region through the weekend. A broad surface high
pressure will continue to build behind the front through the period,
promoting east to northeast winds up to 20 mph with higher gusts at
times during the day. Drier air aloft will gradually erode as an
upper level trough over the Atlantic presses against a mid-to upper-
level ridge centered over the Caribbean basin.


&&

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

Model guidance suggests a Tropical Upper Tropospheric Trough (TUTT-
low) developing over the eastern Caribbean by Monday. As the upper-
level trough deepens on the eastern side of Puerto Rico and the U.S.
Virgin Islands, expect a weak surface-induced trough to move over
the area through the long-term period. Despite these features, the
mid-levels are expected to remain fairly dry with relative humidity
remaining below 40% for most of the workweek, although an increase
is expected by Friday. At low-levels, the latest model guidance
suggests precipitable water values remaining within the 25th and
75th percentile of the climatological normal, with highest amounts
expected by the end of the workweek. The Galvez-Davison Index
indicates that most of the activity during the long-term forecast
will remain mostly shallow. Therefore, expect alternating periods of
fair weather and showery weather depending on moisture content being
dragged by the easterly trades. Increasing frequency of showers
are anticipated by the end of the long-term period.

&&

.AVIATION...
(06Z TAFS)
Issued at 450 AM AST Fri Dec 1 2023

Mainly VFR conditions are expected across all terminals during
the next 24 hours. Quick trade wind showers should cause mostly
VCSH across the area terminals. Winds from the east to northeast
at 12-16 kt with higher gusts after 14z, and sea breeze variations
along the south/west coast of Puerto Rico.

&&

.MARINE...
Issued at 450 AM AST Fri Dec 1 2023

Recent observations from buoy 41043 indicates that the northerly
swell will reach the northern surf zone in the next few hours
promoting life-threatening rip currents. For that reason the High
Rip Current Risk is already in effect for these areas. Nevertheless,
the highest energy from the swell is expected to reach the local
beaches by this afternoon.

There is a Small Craft Advisory starting at 8 AM Saturday through
8 AM AST Sunday for the offshore Atlantic waters. However, it is
very likely that the Small Craft Advisory for the offshore
Atlantic waters will be extended through at least Monday. Continue
to monitor the marine forecast for further updates.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
418 AM AST Sat Dec 2 2023

.SYNOPSIS...

A surface high pressure over the Central Atlantic will continue
to promote moderate to fresh easterly winds today. An increased
moisture from an old frontal boundary will move in late today,
increasing the potential for shower activity across the region.
Hazardous marine conditions will persist for the rest of the
weekend, with seas up to 7 feet. Regardless of the stable weather
conditions and periods of no rain with clear skies, fragmented
moisture will result in occasional periods of clouds and showers.

&&

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

Mostly clear skies with little to no rain prevailed across the
U.S. Virgin Islands and Puerto Rico overnight. The thermometers
reported the coastal low temperatures in the mid-70s degrees
Fahrenheit and around the low 60s near mountains and valleys.
Surface winds were mainly from the east-northeast at 10 mph or
less.

An advective pattern will dominate the short-term period associated
with the surface high pressure across the Atlantic Ocean. Although
we expect plenty of periods of sunshine, the trade winds will bring
occasional passing showers, mainly across the windward sections in
Puerto Rico and the Virgin Islands. Limited afternoon convection
could occur along the Cordillera Central and over the southwest
quadrant today. The surface high pressure will push the remnants of
an old frontal boundary across the islands, increasing the frequency
of the passing showers late this afternoon into the evening and
early Sunday morning.

A tropical upper tropospheric trough (TUTT) will amplify from the
Central Atlantic into the eastern Lesser Antilles, pushing the mid-
high pressure eastward into the Western Caribbean and weakening the
upper-level ridge. Meanwhile, at the surface, the local effects and
sea breeze variations will promote the formation of afternoon
convection across the interior and southwest PR on Sunday, giving
place to ponding in periods of moderate to heavy rain.

The TUTT mentioned above will induce surface perturbations that
winds will advect into the region by Monday, creating the typical
December advective weather pattern across the U.S. Virgin Islands
and Puerto Rico. The amount of rain will be tied to the arrival of
patches embedded in the winds that may move inland. We forecast that
temperatures will range around the December-typical values for our
region.

&&

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

A seasonal weather pattern will persist for most of the long
term. Model guidance continues to suggest the development of a
Tropospheric Upper-Level Trough just east of the Leeward Islands
by the beginning of the upcoming workweek. Although the islands
will remain on the subsidence side of the TUTT, a weak induced
surface trough from the TUTT above will result in trapped moisture
at 800 mb. The shallow moisture embedded in the east-
southeasterly winds and the local effects will be enough to
increase the frequency of the passing showers across windward
sections on Tuesday into Thursday. By late Wednesday into
Thursday, the high surface pressure over the central Atlantic will
be the main feature, resulting in east-southeast wind, bringing
pulses of moisture. Global model guidance suggests a surface wind
variation due to the arrival of a pre-frontal trough moving
southward into the Caribbean for the last part of the long-term
period.

&&

.AVIATION...
VFR conditions will prevail today. Expect calm to light and variable
winds til 02/13z. Then, winds will be mainly from the E-ENE at 10-15
kt with stronger gusts mainly due to sea breeze variations. The wind
flow sometimes brings passing showers and may produce localized
brief lower visibilities. Clouds and mountain obscuration could
develop along the interior and southwest PR by the afternoon. The
frequency of SHRA will increase near JSJ/IST/ISX after 02/21z.

&&

.MARINE...

A broad surface high pressure building over the western Atlantic
will promote moderate to fresh easterly winds across the regional
waters. The combination of a northerly swell and the increasing
winds and northerly swells will maintain choppy to hazardous seas
across the offshore waters and local passages through at least
Sunday. Therefore, a Small Craft Advisory is in effect for the
offshore Atlantic waters from 8 AM AST today though at least 8 AM
on Sunday. Conditions will remain slightly hazardous on Monday
morning. For beachgoers, there is a high risk of rip currents
across the northern sections of Puerto Rico and Culebra on Sunday
morning

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
452 AM AST Sun Dec 3 2023

.SYNOPSIS...

A seasonal weather pattern will persist for most of the short term
with the influence of shallow patches of moisture and a high
surface pressure over the central Atlantic. Therefore, residents
can expect brief passing showers in the morning, followed by
localized afternoon showers over the interior and southwestern
quadrant. By Thursday into Friday, the islands can expect more
moisture associated with fragments of a frontal boundary moving in
pushed by the east-northeasterly winds. Seasonal temperatures are
forecast for the islands.

&&

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

A fragment of moisture pushed by the trade winds brought showers
across the windward sections along the northern and eastern sections
of Puerto Rico and the U.S. Virgin Islands overnight. Rainfall did
not produce flooding along these areas, while the rest of the region
observed mostly clear skies. The thermometers reported the coastal
low temperatures in the mid-70s degrees Fahrenheit and around the
low 60s near mountains and valleys. Surface winds were mainly from
the east-northeast at ten mph or less.

Under a trade wind pattern, the advection of fragmented moisture
will result in occasional rain showers, mainly across the windward
sections. At mid-levels, high pressure will create hostile dynamic
conditions for deep convection. Therefore, we expect the formation
of shallow afternoon convection due to local effects and sea breeze
limited to the southwest quadrant of Puerto Rico today. Regardless
of St Croix, where the maximum temperatures have been around the low
90s, the rest of the islands may observe the typical maximum
temperatures for December.

A tropical upper tropospheric trough (TUTT) amplifying east of the
Lesser Antilles will induce a series of surface perturbations that
the easterly winds will advect into the region, creating the typical
December advective weather pattern across the U.S. Virgin Islands
and Puerto Rico. The amount of rain will be tied to the arrival of
patches embedded in the winds that may move inland. We forecast that
temperatures will range around the December-typical values for our
region.

&&

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

The long-term remains on track. Model guidance continues to
suggest a surface high pressure dominating the local pattern
resulting in an easterly trade wind by Wednesday into early
Thursday. This wind flow will push a drier airmass across the area
on Wednesday, followed by a patch of moisture on Thursday. A pre-
frontal trough from a frontal boundary moving southeastward into
the Caribbean will enhance a relaxation in the pressure gradient,
turning winds more light and variables Thursday at least until
Friday. Light and variable surface winds are not forecast to last
long, as a broad building surface high pressure exiting the
Eastern Seaboard of the United States over the western Atlantic
and a frontal boundary tighten the pressure gradient late Friday.
The east-northeast wind and the moisture from the frontal boundary
will create an aggressive pattern across the areas. Therefore,
residents and visitors can expect periods of quick passing showers
across northern regions in the early morning and evening hours.
Although an increase in moisture will, a mid-level ridge will
provide stable and drier conditions aloft, limiting the life of
the showers.

&&

.AVIATION...
VFR conditions will prevail today. Winds will be mainly from the E-
ENE at 10 kt or less, after 03/13z will range mainly at 10-15 kt
with stronger gusts due to sea breeze variations. Clouds and
mountain obscuration could develop along the interior and southwest
PR by the afternoon (03/16-22z). The frequency of SHRA will increase
near JSJ/IST/ISX after 03/22z.
&&

.MARINE...

A broad surface high-pressure over the western into the central
Atlantic will continue to promote moderate easterly trade winds
across the regional waters for the rest of the weekend and into
the upcoming workweek. The mild winds and the northerly swells
will maintain choppy to hazardous seas for small craft, mainly
across the local offshore waters and passages through the weekend
into Monday evening. Therefore, there is a Small Craft Advisory
until Monday for the offshore Atlantic waters and the Anegada
Passage. Improving seas are forecast for Tuesday onwards. For
beachgoers, there is a high risk of rip currents across the
northern sections of Puerto Rico and the USVI today, diminishing
to moderate in the evening.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
435 AM AST Mon Dec 4 2023

.SYNOPSIS...
Issued at 429 AM AST Mon Dec 4 2023

A surface high pressure inducing an easterly wind flow will drive
the local weather conditions. Therefore, expect an advective
pattern with the arrival of occasional fragments of moisture with
clouds and showers. Regardless of it, expect periods of
sunshine/clear skies under a stable weather pattern throughout the
workweek. Moisture content may increase during the weekend. Life-
threatening rip currents will be possible, especially along the
north and east-facing beaches in Puerto Rico, Culebra, and the
U.S. Virgin Islands throughout the week; please exercise caution.

&&

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

Stable weather conditions prevailed across the local region in the
night hours. The Doppler Radar observed a few quick showers over
the offshore Caribbean Waters and some coastal areas of St. Croix,
with insignificant rainfall accumulations. Overnight temperatures
were in the low to mid 70s across the coastal areas and into the
low to mid 60s across the mountain areas.

For the rest of the period, stable conditions will persist as a mid
to upper level ridge remains in place, resulting in drier air aloft.
The weather pattern will be more interesting at the surface with the
influence of a broad surface high pressure over the Central
Atlantic, extending to the western Atlantic, resulting in an
easterly trade wind pattern for today into early Wednesday. Trapped
moisture at 800 MB from a previous surface perturbation from an
upper-level trough will move into the region, embedded in the wind
flow, resulting in an advective pattern. According to the PWAT-
derived Satellite Imagery, the best chance for rain activity will be
today into Tomorrow with an area of shallow moisture with
precipitable water values of 1.55 inches. By Wednesday, the latest
model guidance suggests the arrival of an area of drier airmass with
Precipitable Water remaining two standard deviations below the
climatological normals. Therefore, residents and visitors can
experiment with stable weather conditions with minimal rain activity
for most of the day until another pulse of shallow moisture arrives
at late night hours.

&&

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

A short wave trough moving to the north across the Atlantic Ocean
will weaken somewhat the mid-level ridge over the Northeast
Caribbean Thursday through Friday. While at the surface, a cold
front could approach from the northwest, pooling moisture over
Puerto Rico and the U.S. Virgin Islands late Thursday night into
Friday. The Total Precipitable Water (TPW) may increase by 1.5
inches or more during the second part of the workweek. Under this
weather pattern, the frequency of passing showers with periods of
moderate to locally heavy rain could be possible, especially
across the windward sections in Puerto Rico and the U.S. Virgin
Islands. The surface winds will prevail mainly from the east-
northeast to northeast through at least Saturday.

Model guidance suggests the mid-level ridge building, once again
during the weekend into next week. However, the moisture
associated with the frontal boundary, lingering north of the
islands, may result in showery weather, especially along the
windward sections and surrounding waters on Saturday. Moisture
content may erode by Sunday without ruling out the arrival of some
occasional quick passing showers.

Another cold front could be exiting the Eastern Seaboard around
Sunday, moving eastward and approaching the region by late Monday
night or Tuesday, which may increase rain activity early next
week. However, high uncertainty is associated with this forecast,
as this solution may change as we approach next week.

&&

.AVIATION...
(06Z TAFS)
Issued at 429 AM AST Mon Dec 4 2023

VFR conditions will prevail for most of the period across
all the TAF sites. Winds will persist VRB and light, increasing from
10- 14 knots by 04/15Z, with sea breeze variations in most
terminals. Due to the afternoon convection, SHRA is possible over
TJBQ near 04/18-04/22. Increasing in VCSH are expected TIST, TISX,
and TJSJ, from 04/22Z.

&&

.MARINE...
Issued at 429 AM AST Mon Dec 4 2023

A broad surface high pressure building over the western Atlantic
will promote moderate to fresh trade winds across the regional
waters. A low pressure and its associated frontal boundary will move
northeastward across the Western Atlantic. A northeasterly swell
generated by surface pressure systems across the Central Atlantic
will arrive from mid-week onward.

&&

.BEACH FORECAST...

Life-threatening rip currents will develop across the beaches
along the northeast coast of Puerto Rico and the eastern half of
St Croix today. The rest of the Atlantic Coastline in Puerto Rico,
Culebra, and the U.S. Virgin Islands has a moderate risk of rip
currents. This evening, the risk will also be high from Arecibo to
Carolina and Culebra.

Please exercise caution across the north and east-facing beaches
of the islands throughout the week as life-threatening rip
currents may develop. A northeasterly swell will arrive from mid-
week onward, affecting these beaches.

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
526 AM AST Thu Dec 7 2023

.SYNOPSIS...Anticipate generally stable weather conditions today,
characterized by mostly clear skies and limited shower activity
under a light breeze. A transition is likely from Friday into the
weekend as a building surface high pressure generates increased
wind speeds across the region and a cold front settles north of
the islands. While an enhanced frequency of showers moving into
windward areas from the local waters is likely with these
conditions, the remnants of a cold front will contribute to this
wet trend during the weekend into early next week. Starting on
Friday, hazardous seas for small craft and life-threatening rip
currents for beachgoers are anticipated due to the impact of
northwesterly swells and increasing winds.


&&

.SHORT TERM...Tonight through Friday...

A stable weather pattern is forecast over the next few days as a mid-
upper level ridge remains over the eastern Caribbean. This will
maintain dry and stable conditions aloft, while suppressing
convection. The presence of drier air today across the northeastern
Caribbean will also continue to limit shower development over the
islands and regional waters. An induced pre-frontal trough is
resulting in the weakening of the local pressure gradient and
trade wind flow today, allowing light winds to exist for most
areas with the exception of higher speeds across coastal areas due
to seabreeze enhancement. Under this expected pattern there will
be the potential for shower development mainly over the interior
and west-southwest sections of Puerto Rico.

Late tonight into Friday, a polar trough will move eastward
across the west Atlantic, with it's moisture field approaching the
northwestern corner of the region. By Friday the winds will begin
to prevail from the east-northeast, increasing in strength as a
surface high pressure builds across the western Atlantic. This
will result in a cooler advective pattern and better chance for
quick passing overnight and early morning showers that will
continue into Saturday. This acceleration of the trade winds will
also assist the advection of a moist airmass into eastern
Caribbean, with the northern boundary moving into the southern
half of the region. This will increase the rate of passing showers
on Saturday afternoon into the night across eastern Puerto Rico
and the USVI. However, due to stronger winds, showers should be
fast moving without any significant rainfall accumulations.

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

While there is a possibility of limited afternoon convective
development, a cool advective pattern, typically the primary
source of shower development during the local fall season, will
prevail. A dominant mid-level ridge will persist over the northern
Caribbean, sustaining a trade wind cap inversion and dry air
aloft, suppressing shower development. However, weak upper-level
troughs will briefly weaken the trade wind cap and facilitate the
influx of deep moisture into the region. Meanwhile, at the
surface, a subtropical surface high pressure system building over
the western-central Atlantic will maintain a tightened local
pressure across the Northeastern Caribbean and, thus, breezy to
locally windy conditions are likely across the forecast area.
These increased winds will frequently steer patches of shallow
moisture, including moisture related to the remnants of a cold
front and an easterly disturbance early in the forecast period.

According to model guidance, precipitable water values are
anticipated to remain within typical seasonal levels (between 1.2
and 1.6 inches). However, above-normal moisture levels (1.6 inches
or higher) are likely on Sunday into Monday and later in the
workweek, aligning with the timing of the remnants and easterly
disturbances and a weakened trade wind cap. These brief
transitions will be evident in the increased frequency of showers
moving inland from the waters, especially during nighttime over
eastern Puerto Rico and the U.S. Virgin Islands. Despite this,
hazard risks through the long-term forecast period should center
on winds-related threats, mainly across coastal areas and lower
elevations.


&&

.AVIATION...VFR conditions will prevail for all the TAF sites during
the period. Winds will remain light through the morning, increasing
from seabreeze by 06/14Z. Shallow afternoon convection may result
in RA, mainly over the interior of Puerto Rico resulting in a lower
ceiling over TJPS and TJBQ from 06/16 to 06/22Z. However, VFR
conditions will prevail.


&&

.MARINE...Recent observations from the CariCOOS buoy network near
Puerto Rico and the U.S. Virgin Islands have shown consistent
marine conditions with wave heights below 3 feet.

Marine conditions are forecast to deteriorate as a long-period
northwesterly swell and increasing winds impact the regional
waters starting Friday and continuing through the weekend. Seas
are anticipated to reach up to 8 feet, with occasional seas up to
10 feet, while winds will gradually reach 15-20 knots on Friday
and escalate to 20-25 knots with gusts up to 30 knots over the
weekend. Small Craft Advisories are currently in place for the
offshore Atlantic waters and coastal waters of northern Puerto
Rico. With hazardous conditions expected to expand across the
local waters, additional Small Craft Advisories will be required
from Friday evening onward. For more information on current marine
risks, refer to the Marine Weather Message (MWWSJU).


&&

.SURF ZONE...A moderate risk of rip currents remains for most
northern beaches of Puerto Rico and the eastern beaches of Saint
Croix today. However, deteriorating marine conditions will also
impact beach conditions, with breaking waves increasing to 6-7
feet, likely generating life-threatening rip current conditions
from Friday onward. If the forecasted conditions persist, a Rip
Current Statement will be issued later today, covering beaches
from Rincon eastward to Fajardo across northern Puerto Rico and
the beaches of Culebra, Vieques, and the U.S. Virgin Islands. For
details on current surf zone risks, refer to the Coastal Hazard
Message (CFWSJU).

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
506 AM AST Sat Dec 9 2023

.SYNOPSIS...A long-dominant period northwesterly to northerly
swell and fresh to strong winds, generated by a building surface
high pressure over the western-central Atlantic, will maintain
hazardous marine conditions and life-threatening swimming and rip
current conditions during the next few days. Small craft operators
and beachgoers, both residents and visitors alike, must remain
vigilant and steer clear of these hazardous and potentially life-
threatening conditions. As the anticipated steering flow will
likely increase shower frequency, impacting windward areas from
the local waters, the remnants of a cold front will add to this
wet trend during the weekend into early next week. More stable
conditions, with lower available moisture levels, are expected by
the latter part of next week.


&&

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

Variable weather conditions prevailed across the local region during
the night hours. The Doppler Radar observed isolated to moderate
showers over the offshore Caribbean Waters and inland areas with
insignificant rainfall accumulations. Overnight temperatures were in
the low to mid-70s across the coastal areas and into the low to mid-
60s across the mountain areas.

Satellite derived precipitable water (PWAT) values show an area of
moist air related to a low level trough moving westward over the
southeastern Caribbean Sea, that has been approaching the area
through the overnight hours, pushing PWAT to normal values. The bulk
of the moisture, and associated stronger shower activity, should
stay over the Caribbean Sea with only passing showers affecting
windward sections of the islands. Drier air with below normal PWAT
values around 1.1 inches will filter in from the northeast today as
the moist air mass south of the area continues moving westward.
Diurnally induced shower development is still forecast today, mainly
across central to west-southwest PR. Periods of late morning and
afternoon showers will also be possible in and around the USVI. PWAT
values are forecast to increase again as moisture from remnants of a
frontal boundary now north of the region move over the area from the
northeast during the early overnight hours on Sunday, pushing PWAT
values to normal and above normal values tomorrow and making it the
wettest day of the short term period. With shallow convective
instability and increasing winds, passing showers are forecast
mainly across north and east sections of the islands, particularly
Puerto Rico, during the overnight to morning hours on Sunday, and
possibly moving further inland. Current model guidance suggests that
moisture should linger but gradually decrease on Monday, promoting
more seasonal weather. At surface level, a building high over the
western Atlantic will also help promote breezy conditions, with up
to fresh to strong east to east-northeast winds through most of the
period. A mid-level ridge will continue to affect the area during
the period, limiting vertical development of convection.

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

The latest model guidance has not introduced significant changes,
except for variations in the timing of relatively dry and moist
patches streaming across the region. Although there is a chance of
limited afternoon convective development, the primary rain
contributor will result from showers developing due to a cool
advective pattern during the forecast period. A dominant mid-level
ridge will persist over the northern Caribbean throughout the
workweek into the upcoming weekend, sustaining a trade wind cap
inversion at around the 800-850 mph level and drier air aloft,
confining moisture to the lower levels and, thus, suppressing the
likelihood for deep convective or thunderstorm development.
Meanwhile, at the surface, a strong surface high pressure system
over the western-central Atlantic will maintain a tightened local
pressure across the Northeastern Caribbean and, thus, generating
breezy to locally windy conditions with winds up to 25 mph and
gusts up to 30-40 mph, mainly across coastal areas and lower
elevations.

In the expected weather scenario, with intermittent patches of
drier air and shallow moisture streaming across the region, expect
variations in moisture levels every 12 hours or so, but less
significant than previously suggested. According to model
guidance, precipitable water should generally remain within
typical seasonal moisture levels around 1.2-1.6 inches, except for
above-normal precipitable water values around 1.7 by late Tuesday
night and below-normal precipitable water values by Wednesday
evening into Thursday morning and Friday. During the highest
moisture periods, expect an increased frequency of showers moving
inland from the waters, especially during nighttime over eastern
Puerto Rico and the U.S. Virgin Islands, with limited afternoon
convective development, if any. Despite periods of increased
shower activity, hazard risks through the long-term forecast
period should center on winds-related threats.


&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals through the forecast period. Shower activity can affect
eastern terminals at times, particularly TJSJ/TIST/TISX/TJPS.
However the bulk of shower activity should remain over the
Anegada/Caribbean Waters today aft 09/14Z surface winds incr to 15-
20 kts from the ENE with sea breeze variations and higher gusts neat
25-30 kts.


&&

.MARINE...Recent observations from the CariCOOS buoy network near
Puerto Rico and the U.S. Virgin Islands have shown consistent
deteriorated and hazardous marine conditions with wave heights of
7-9 feet in buoys with Atlantic exposure. Elsewhere, wave heights
have remained around 4-6 feet.

Marine conditions will remain deteriorated and hazardous as
additional pulses of a long-dominant period northwesterly to
northerly swell and vigorous to fresh winds impact the regional
waters through the weekend into early next week. During the next
few days, seas will likely reach up to 10 feet, with occasional
seas up to 11 feet, while winds will gradually reach up to 25
knots with gusts up to 30 knots. Small Craft Advisories are
currently in place for most local waters, except for protected coastal
waters of southwestern Puerto Rico, where small craft operators
should exercise caution. For more information on current marine
risks, refer to the Marine Weather Message (MWWSJU).


&&

.SURF ZONE...Deteriorated marine conditions will also impact surf
zone and beach conditions, producing large breaking waves reaching
up to 13 feet. These conditions will likely result in high surf
and life-threatening swimming and rip current conditions today,
but these conditions could continue throughout the weekend and
into early next week. So far, a Rip Current Statement and a High
Surf Advisory are currently in effect for beaches extending from
Rincon and Aguada in the west to Fajardo in the northeast,
covering the northern coastline of Puerto Rico. Furthermore, a
High Risk of Rip Currents is also in effect for beaches in
southeastern Puerto Rico, Culebra, Vieques, and the U.S. Virgin
Islands. For details on current surf zone risks, refer to the
Coastal Hazard Message (CFWSJU).

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Sun Dec 10 2023

.SYNOPSIS...Ongoing hazard risks arise from the interaction of a
long-dominant period northerly swell with persistent fresh to
strong winds, generated by a strong surface high pressure over the
western-central Atlantic. This interaction will promote
deteriorated and hazardous marine conditions and life-threatening
swimming and rip current conditions throughout the workweek. Small
craft operators and beachgoers, both residents and visitors alike,
must remain vigilant and steer clear of these hazardous and
potentially life-threatening conditions. Although moisture from an
old cold front will be the source of today's shower activity, the
anticipated strong steering flow will likely continue to support a
frequent passing shower pattern during the next few days.


&&

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

Calm weather conditions prevailed through midnight. Then, the
remnants of an old frontal boundary brought clouds and showers
across the local waters and the windward sections in Puerto Rico and
the U.S. Virgin Islands. Overnight low temperatures were in the mid-
70s across the coastal areas and in the low-60s in mountains and
valleys.

A subtropical high pressure north of the islands will promote breezy
to locally windy easterlies across the local waters through Tuesday.
The easterlies will push the remnants of a frontal boundary across
the islands, increasing the Total Precipitable Water (PWAT) near to
above normal values. Under this weather pattern, showery and cloudy
weather will prevail today. However, we are not anticipating
significant flooding across the islands. These showers will produce
occasional periods of moderate to locally heavy rain, resulting in
ponding of water in poorly drained areas and roads. Monday's weather
pattern will be similar to today's, with the advection of some
clouds and showers but less rainfall.

Once again, we are at the mercy of the winds, but the moisture
content will continue to slowly erode late Monday night into Tuesday
and be replaced by a cooler air mass, resulting in pleasant
temperatures. The breezy easterlies will bring occasional passing
showers regardless of this air mass.

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

Except for variations in the timing of high and low moisture
periods, the latest model guidance has yet to introduce
significant changes. The most significant rains will result from
showers generated by cool advective processes across the local
waters and carried by the general steering flow, dominated by
east-to-east-northeast trade winds at 15-25 mph and occasionally
higher speeds, into windward areas during the forecast period.
These breezy to windy conditions will result from a persistent
strong surface high pressure system over the western-central
Atlantic, maintaining a tightened local pressure gradient across
the Northeastern Caribbean. Meanwhile, a dominant mid-level ridge
will also persist over the northern Caribbean, sustaining a trade
wind cap inversion at around the 800-850 mph level and drier air
aloft and confining moisture to the lower levels, thus suppressing
the likelihood for deep convective or thunderstorm development.
However, a weak upper-level trough will briefly weaken the trade
wind cap and facilitate the influx of deep moisture into the
region by the end of the workweek into the upcoming weekend.

In the expected weather scenario, with intermittent patches of
drier air and shallow moisture streaming across the region,
variations in moisture levels will be less chaotic. The latest
model guidance suggests precipitable water values falling to
below-normal thresholds or below 1.2 inches by mid-week, gradually
increasing to above-normal levels of about 1.6-1.7 inches on
Saturday. During the highest moisture periods, expect an increased
frequency of showers moving inland from the waters, especially
during nighttime over eastern Puerto Rico and the U.S. Virgin
Islands, with limited afternoon convective development, if any. Despite
periods of increased shower activity, hazard risks through the
long-term forecast period should still center around winds-related
threats.


&&

.AVIATION...SHRA/-SHRA will sometimes move across JSJ/IST/ISX
through at least 10/15z, reducing VIS between 4 and 6 SM. However,
VFR conditions will mainly prevail across the local flying area.
Winds will range principally from the east at 10 to 15 kt
overnight and gusty near SHRA. Winds will vary between 15 and 20
kt with gusts up to 30 kt after 10/12z.


&&

.MARINE...Recent observations from the CariCOOS buoy network near
Puerto Rico and the U.S. Virgin Islands have shown consistent
deteriorated and hazardous marine conditions with wave heights of
7-8 feet at 10-12 second periods in buoys with Atlantic exposure.
Elsewhere, wave heights have remained around 4-6 feet.

Marine conditions will remain deteriorated and hazardous as
additional pulses of a long-dominant period northwesterly to
northerly swell and vigorous to fresh winds impact the regional
waters through the weekend and continue until at least mid-week.
During the next few days, seas will likely reach 8-10 feet, with
occasional seas up to 11 feet, while winds will peak around 20-25
knots with gusts up to 30 knots. Small Craft Advisories are
currently in place for most local waters, except for protected
coastal waters of southwestern Puerto Rico, where small craft
operators should exercise caution. Seas will drop below small
craft advisory for some protected coastal waters on Monday, but
hazardous seas will continue throughout the workweek. For more
information on current marine risks, refer to the Marine Weather
Message (MWWSJU).


&&

.SURF ZONE...Deteriorated marine conditions will also impact surf
zone and beach conditions, producing large breaking waves reaching
up to 12 feet and occasionally higher. These conditions will
likely result in high surf and life-threatening swimming and rip
current conditions today. So far, a Rip Current Statement and a
High Surf Advisory are currently in effect for beaches extending
from Rincon and Aguada in the west to Fajardo in the northeast,
covering the northern coastline of Puerto Rico, and Culebra.
Furthermore, a High Risk of Rip Currents is also in effect for
beaches in southeastern Puerto Rico, Culebra, Vieques, and the
U.S. Virgin Islands. High surf conditions should cease this
evening, but the high rip current risk will continue throughout
the workweek. Refer to the Coastal Hazard Message (CFWSJU) for
details on surf zone hazard risks.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
446 AM AST Mon Dec 11 2023

.SYNOPSIS...
The remnants of an old frontal boundary will continue to bring
fragmented clouds and showers over the islands today. A strong
surface high over the central Atlantic will promote breezy
conditions during the next few days. Then, another surface high
building over the western Atlantic will further tighten the
pressure gradient over the area and strong east to northeast
trades will prevail through the workweek. A distant surface low
pressure over the central Atlantic is expected to develop by
midweek and swells associated to the low in combination with the
locally wind-driven seas will cause rough surf conditions with
life-threatening rip currents through the end of the week.


&&

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

The brisk easterly winds continued to bring patches of remnant
moisture from an old frontal boundary along with embedded quick
passing showers across the coastal waters and portions of the
islands during the overnight and early morning hours. Periods of
light to moderate showers with brief gusty winds were experienced
over portions of northeastern and eastern Puerto Rico as well as
over the coastal waters in and around the U.S. Virgin Islands from
time to time. Rainfall accumulations so far were between 0.25 to
0.50 inches with the heaviest rains. Some of the earlier heavier
rains caused minor ponding of water on roads and hazardous driving
condition in isolated areas as they passed by. Low temperatures
ranged from the mid to upper 70s along coastal areas and in the mid
to upper 60s in higher elevations and valleys. Winds became calm to
light and variable overnight.

For the rest of the day, variable skies is expected to prevail
during the early part of the morning, followed by a mix of sunshine
and clouds during the rest of the day. Breezy conditions will
persist, as the broad surface high pressure will remain anchored and
be reinforced across the central Atlantic throughout the period.
Consequently this will lead to the tightening of the local pressure
gradient resulting in breezy to windy conditions across the region.
This expected moderate to locally strong easterly wind flow will
bring occasional patches of shallow moisture across the islands and
coastal waters at least through tonight into Tuesday morning. In the
meantime a mid to upper ridge will continue to build and settle in
across the region during the rest of the period. Precipitable water
values will range between 1.45 to 1.7 inches through early Tuesday,
mainly due to shallow low level remnant moisture advection,
thereafter, a gradual erosion of moisture will favor precipitable
water values around an inch or slightly less by Wednesday.
The dry and stable condition aloft due to the mid to upper level
ridging will aid in inhibiting significant convective development
during the daytime but the intervals of passing showers will persist
into early Tuesday morning.

Recent model guidance and the overall weather pattern suggests a
gradual erosion of low level moisture transport, with the local
winds forecast to become more northeasterly and increase, as the
aforementioned high pressure ridge builds across the region
resulting in a gradual improvement and more seasonal weather pattern
with pleasant weather and cool seasonal temperatures by Tuesday and
through Wednesday. Breezy to windy conditions, are however forecast
to continue through the period due to the interaction of the
building high pressure ridge north of the region and an elongated
area of low pressure forecast to develop across the tropical
Atlantic well northeast of the region.

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

Similar conditions will continue on Thursday, and at least as of
today, it seems that it will be the driest day of the long term
period. Then on Friday into the weekend, a weak upper level
trough will press against the mid-to upper-level ridge and pooling
of moisture is expected across the northeastern Caribbean, with
trade wind perturbations reaching the local area at times from
the east. Then on Sunday and Monday, winds are forecast to
gradually turn more east to southeast as a broad surface low
pressure moves into the western Atlantic. This will continue to
promote pooling of moisture across the local area with
precipitable water content ranging between 1.75-2.00 inches from
Friday onwards. Therefore, expect a wetter pattern through the
long term period, with possible isolated thunderstorms on Friday
as 500 mb temps drop to around minus 6 degrees Celsius in response
to the upper level trough moving over the region.


&&

.AVIATION...
VFR conds at all TAF sites. However, Brief MVFR conditions psbl due
to low cig/ wdly SCT SHRA ovr regional waters and en route btw the
local islands. SCT ocnl Bkn lyrs nr FL025...FL050. VCSH at
TJSJ/TISX/TIST til 11/12Z. Mtn top obscr psbl ovr E interior of PR
due low cig/-SHRA. Low leve wind fm E-NE 15-25 kts BLO FL180...then
backing while incr w/ht ABV. SFC wnd light and variable to calm
bcmg fm E 15 to 20 knots and gusty winds to 25-30 knots psbl aft
11/14Z.


&&

.MARINE...
Hazardous seas due to a combination of wind-driven waves and
northerly swells will continue for the next several days across
most local waters. Therefore, Small Craft Advisories are in effect
through at least Friday afternoon, and will likely be extended
later this week. Easterly winds between 15 and 25 knots will
prevail through the workweek. Please refer to the latest Marine
Weather Message (MWWSJU) for more information.


&&

.SURF ZONE...
A High Rip Current Risk (CFWSJU) is in effect for all beaches
from northwestern to eastern Puerto Rico, including the beaches in
southeastern Puerto Rico, Culebra, Vieques, and all the U.S.
Virgin Islands. For more information and details please refer to
the latest Surf Zone Forecast (SRFSJU), and the Coastal Hazard
Message product (CFWSJU).

Life-threatening rip currents will prevail through the upcoming
weekend across most of the east and north facing beaches of the
islands.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
431 AM AST Tue Dec 12 2023


.SYNOPSIS...
Issued at 423 AM AST Tue Dec 12 2023

Another surface high building over the western Atlantic along with a
strengthening broad surface low pressure over the central Atlantic
will further tighten the pressure gradient over the area and strong
east-to-northeast trades will prevail through the workweek. Swells
associated with the low in combination with the locally wind-
driven seas will cause rough surf conditions with life-threatening
rip currents through the end of the week.

&&

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

Skies were mostly clear over west and southwest Puerto Rico and
to partly cloudy elsewhere. The brisk northeasterly winds
continued to steer occasional patches of trade wind moisture with
embedded quick passing showers across the coastal waters and
portions of the islands during the overnight and early morning
hours. Periods of light to moderate showers along with brief gusty
winds were experienced over portions of northeastern and eastern
Puerto Rico as well as over the coastal waters in and around the
U.S. Virgin Islands. Rainfall accumulations were less than 0.25
inches with the heaviest rains. Low temperatures ranged from the
mid to upper 70s along coastal areas and in the mid to upper 60s
in higher elevations and valleys. Winds were from the east
northeast 10 kts or less but with higher gusts accompanying
passing showers.

For the rest of the day, the dry and stable conditions aloft will
aid in inhibiting significant convective development, however
intervals of passing showers especially along the north and east
coastal areas will persist into the early morning hours. Expect a
mix of sunshine and clouds with periods of quick passing showers to
move in and out of the area steered by the prevailing east northeast
winds. An gradual drying trend is forecast into Wednesday with
precipitable water values ranging between 1.12 inches(St Martin TNCM
12/00z upper air sounding) and 1.37 inches (TJSJ 12/00Z). Breezy
conditions will persist, as the broad surface high pressure will
remain anchored and be reinforced across the central Atlantic. This
along with an developing area of low pressure across the east
central Atlantic will lead to the tightening of the local pressure
gradient, resulting in breezy to windy conditions for the remainder
of the period. The expected moderate to locally strong northeasterly
winds will bring occasional patches of shallow moisture across the
islands and coastal waters overnight into the early morning hours
each day.

In the upper levels a mid to upper ridge will continue to settle in
across the region through most of the period, before eroding late
Thursday onwards, as an upper trough and associated cold front is
forecast to enter the west and southwest Atlantic. Recent model
guidance suggests diminishing precipitable water values to around
one inch or less with an overall drier trend, except for the shallow
overnight and early morning advective moisture expected today
through Wednesday. Moisture content is to increase once again on
Thursday to between 1.50-1.75 inches as the trade winds increase
along with good advective moisture pooling. The driest period now
looks like today through Wednesday with a better chance for passing
showery conditions from early Thursday onwards.

Recent model guidance and the overall weather pattern suggests a
continued erosion of low level moisture. The local winds are
forecast to become more northeasterly and significantly increase
Wednesday into Thursday, as the aforementioned Atlantic high
pressure ridge builds across the region. This will result a more
stable and seasonal weather pattern with pleasant weather and cooler
temperatures through Wednesday. However the breezy to windy
conditions are still forecast for the latter part of the period.
This in turn will increase the advective weather pattern resulting
in more frequent passing late evening and morning showers. Some of
showers will develop and move farther inland along the north and
east coastal areas as well as over the interior and southwest
sections of Puerto Rico during the afternoon due to the increased
steering winds. By then, sustained winds between 18-25 mph will be
possible during the day with possible wind gusts to 35 to 40 mph or
slightly higher at times. As a result loose and unsecured small
objects may be blown around. Stay tuned!

&&

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

Above-normal moisture content will persist from Friday through the
weekend. The relative humidities at the 850-700 mb and 700-500 mb
layers will remain above 80% and 50%, respectively, during this
period. However, ridging aloft will limit deep convective
development over the northeastern Caribbean. While wind speeds
would have subsided somewhat by Friday, breezy conditions are
still expected to persist as winds gradually shift from east-
northeast on Friday to more east-southeast by late Sunday.
Therefore, anticipate more of an advective weather pattern as
moisture embedded in the trades promotes light to moderate showers
over windward coastal areas, particularly during late evenings
and morning hours.

Looking ahead, a strong deep-layered trough is expected to build
over the eastern U.S. and move over the western Atlantic by early
next week. This will slightly push the mid-level ridge to the east.
The associated surface shear line will approach from the northwest,
shifting winds more southeast to south-southeast for the remainder
of the long-term forecast. Precipitable water values will fluctuate
between near-normal to slightly above-normal levels. Meanwhile,
dynamics aloft may become slightly more conducive for convective
development as 500 mb temperatures drop to -5 to -6 degrees Celsius.
Therefore, we could observe an increase in shower and some
thunderstorm activity as the deep-layered trough and shear line
approach from the northwest. For now, the forecast confines
thunderstorm development mostly to the northwestern Atlantic waters
and Mona Passage. However, southerly wind flow could increase
surface temperatures, enhancing diurnal heating during peak hours of
the day. This could promote a few isolated thunderstorms over land
areas in the afternoon hours. Weak steering wind flow will also
increase rainfall accumulations over localized areas.

&&

.AVIATION...
(06Z TAFS)
Issued at 423 AM AST Tue Dec 12 2023

VFR conds at all TAF sites. Brief MVFR conditions psbl due to low
passing clouds with Isold to wdly SCT SHRA ovr regional waters and
en route btw the islands. SCT ocnl Bkn lyrs nr FL025...FL050. VCSH
at TJSJ/TISX/TIST til 12/13Z with mtn top obscr psbl ovr E interior
of PR due low cig/-SHRA. Low level wnds fm ENE 15-25 kts BLO
FL150...then backing bcmg fm N while incr w/ht ABV. SFC wnd mainly
fm E 10 kts or less bcmg fm E 15 to 20 knots with gusty winds to 25-
30 knots psbl aft 12/14Z.

&&

.MARINE...
Issued at 423 AM AST Tue Dec 12 2023

Hazardous seas due to a combination of wind-driven waves and weak
northerly swells will continue for the next several days across most
local waters. Therefore, Small Craft Advisories are in effect
through at least Friday afternoon, and will likely be extended later
this week. Easterly winds between 15 and 25 knots with higher
gusts will prevail through the workweek. Please refer to the
latest Marine Weather Message (MWWSJU) for more information.


&&

.SURF ZONE...
Issued at 423 AM AST Tue Dec 12 2023

Life-threatening rip currents will persist due to breaking waves
around 6 to 9 feet, and locally higher in certain surf zones. For
this reason, a High Risk of Rip Currents is in effect for all
beaches from northwestern to eastern Puerto Rico, including the
beaches in Culebra, Vieques, and all the U.S. Virgin Islands. For
more information and details please refer to the latest Surf Zone
Forecast (SRFSJU), and the Coastal Hazard Message product
(CFWSJU).

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
446 AM AST Wed Dec 13 2023


.SYNOPSIS...
Issued at 439 AM AST Wed Dec 13 2023

The interaction of a surface high-pressure north of the area and a
strong low-pressure system northeast of the Caribbean will
continue to promote windy conditions over the local area.
Therefore, a Wind Advisory remains in effect until Thursday with
winds peaking today. Sustained winds at 20 to 30 mph with frequent
gusts around 35 to 45 mph are expected. Outdoor unsecured objects
could blow around or be damaged. Extremely dangerous marine and
coastal conditions through at least this weekend.

&&

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

Skies were mostly clear over west and southwest Puerto Rico and
variably cloudy elsewhere and as passing clouds and light to
moderate showers reached the most of the islands from time to time.
The strong east northeast winds continued to steer patches of trade
wind moisture with embedded showers across the coastal waters and
inland mainly over the north and east sections of the islands. So
far the rainfall was of short duration with accumulations between
0.25-0.50 inches with the heaviest rains. Low temperatures ranged
from the mid to upper 70s along coastal areas and in the low to mid
60s in higher elevations and valleys. Surface winds were from the
east to northeast between 5 to 10 mph but with brief gusty winds
between 18-25 mph accompanied the passing showers.

The intervals of passing showers will continue to affect local
waters and mainly the north and east sections during the rest of the
morning hours. Expect a mixture of sunshine and clouds across the
region with breezy to windy conditions forecast through at least
Thursday. Showers are expected to move in and out of the area
steered by the strong east northeast winds, as the local pressure
gradient further tightens across the region due to the building high
pressure north of the region. Consequently strong sustained winds
winds between 20-25 mph is forecast along with frequent gusts
between 35 to 40 mph. As a result loose and unsecured small objects
may be blown around as well as hazardous driving conditions. For
this reason a wind advisory has been issued (NPWSJU) and will be in
effect at least until 9AM AST Thursday.

Afternoon clouds and shower development is expected to continue to
move inland and develop over portions of the interior and southwest
sections of Puerto Rico, as well as around the U.S. Virgin islands
and surrounding islands. However, as previously mentioned this
activity is expected to move quickly across the islands bringing
periods of sunshine and fair weather throughout the day. A similar
weather pattern is forecast for Thursday, with a mix of sunshine and
clouds and passing showers and pleasant near normal daytime and
overnight low temperatures. Breezy conditions are expected to
continue. By Friday, a wetter pattern is expected as the mid to
upper level ridge is to erode in response to a polar trough moving
across the west and southwest Atlantic. The east northeast wind flow
is also to become more easterly resulting in a return of remnant
trade wind low level moisture and convergence across the islands.
This along with the proximity of the mid to upper level trough will
aid in enhancing overnight and daytime shower activity while
increasing the chance for higher rainfall amounts, and the best
chance for ponding of water on road and poor drainage areas and
minor urban flooding in isolated areas. Widespread rainfall
accumulations are not anticipated at this time. The local trade
winds are also expected to relax across the region by Friday.



&&

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

The synoptic features influencing the long-term forecast have
remained relatively consistent, with the main alteration being the
timing of their effects. Above-normal moisture levels are expected
to persist on Saturday but are anticipated to decrease by Sunday,
remaining at near-normal levels. Ridging aloft will keep 500 mb
temperatures relatively warmer than the climatological normal with
250 mb height fields higher than usual. Consequently, the
atmospheric dynamics do not appear conducive for deep convective
development. However, despite this, there will be enough moisture
for shallow convective activity, leading to showery weather reaching
windward coastal sections during late evenings and morning hours,
especially on Saturday. Breezy wind conditions will continue, but
they are anticipated to be considerably less pronounced compared to
the short-term forecast.

The remainder of the long-term forecast will depend on a
strengthening area of low pressure that models continue to develop
over the south to southeast Gulf of Mexico. According to model
guidance, this robust low-pressure system is expected to move across
Florida by the upcoming weekend and then progress northward over the
western Atlantic. As this occurs, an elongated frontal boundary
associated with the low-pressure system is projected to envelop
the local area by early next week, with Tuesday anticipated to be
the wettest day in the long-term forecast.

This scenario will lead to southerly winds drawing abundant columnar
moisture, fostering increased moisture convergence across the
northeastern Caribbean. Additionally, atmospheric conditions aloft
appear to become conducive for deep convection. However, it's
crucial to note that the timing and positioning of these features
remain subject to change with varying models and each subsequent
model cycle, which have not been consistent in the last day or so.
Despite this inconsistency, there is an indication that the latter
portion of the long-term forecast, which corresponds to mid-week of
next week, will transition towards a more unsettled and wet
weather pattern.

&&

.AVIATION...
(06Z TAFS)
Issued at 439 AM AST Wed Dec 13 2023

VFR conds at all TAF sites. Brief MVFR conds psbl due to low passing
clouds with wdly SCT SHRA ovr regional waters and en route btw the
islands. SCT ocnl Bkn lyrs nr FL025...FL040. VCSH/-RA at TJSJ/TISX/
TIST and TJBQ til 12/13Z with mtn top obscr psbl ovr E interior of
PR due low cig/-RA. Low/lvl wnds fm ENE 25-30 kts BLO FL180...then
backing bcmg fm N and incr w/ht ABV. SFC wnd fm E-NE 5-10 kts bcmg
fm ENE 20 to 25 knots with gusty winds to 30-35 knots psbl aft
13/14Z.

&&

.MARINE...
Issued at 439 AM AST Wed Dec 13 2023

Nearshore Atlantic buoys are already observing seas of 7 to 8 feet
with wind speeds of 15 to 20 knots and higher gusts. This pattern is
expected to increase throughout the day with rough seas increasing
up to 12 feet and occasionally higher across Atlantic coastal
waters, and much higher for the offshore Atlantic waters. East to
east-northeast winds will also increase up to 25 knots with gusts up
to 45 knots. Therefore, Small Craft Advisories are in effect through
at least Saturday. Please refer to the latest Marine Weather Message
(MWWSJU) for more information.

&&

.SURF ZONE...
Issued at 439 AM AST Wed Dec 13 2023

Life-threatening rip currents due to rough surf and large breaking
waves. Nearshore buoys indicated that estimates of breaking waves
are already ranging between 9 to 11 feet. Therefore, a High Surf
Advisory is in effect for all surf zones across northern and eastern
Puerto Rico, Culebra, and northern USVI. High Risk of Rip Currents
are in effect for all other beaches, except southern and
southwestern Puerto Rico. For more information and details please
refer to the latest Surf Zone Forecast (SRFSJU), and the Coastal
Hazard Message product (CFWSJU).