Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
431 AM AST Wed Nov 18 2020

.SYNOPSIS...
An increase in shower activity is forecast for today as a surge of
moisture move into the area. Therefore, passing showers will
continue moving from the waters reaching eastern sections of
Puerto Rico and the U.S. Virgin Islands in the morning hours. Then
afternoon convection is expected over western and interior
sections of Puerto Rico. Urban and small streams flooding is
expected with the heaviest showers. Tranquil marine conditions are
expected with seas between 3 to 5 feet today.

&&

.SHORT TERM...Today through Friday

Tutt low east of the region extending over the Lesser Antilles will
continue to fill and lift further eastward, as the upper ridge
reinforces across the region today into early Thursday. Thereafter
and through Friday the ridge aloft is forecast to erode in response
to a broad polar trough developing and spreading across the west and
central Atlantic. An accompanying short wave trough is also forecast
to cross the region and provide better support and instability aloft
favoring enhanced afternoon convective development across the region
Thursday into Friday.

A fairly moist east to southeast wind flow and advective weather
pattern will persist through the forecast period. Low level moisture
trailing an easterly disturbance will continue through the morning
hours bringing periods of passing showers over the local waters and
east coastal sections of the islands. Diurnal heating and sea breeze
convergence will again support afternoon convection. Thereafter,
additional moisture accompanying a weak tropical wave will spread
across the region to maintain good pooling of moisture and low level
instability through Friday. Recent model guidance continued to
suggest that the layered precipitable water values will range
between 1.7 and 2.0 inches, with the highest moisture content late
Thursday into Friday.

The overall forecast is unchanged and still calls for periods of
overnight and early morning passing showers across the local waters
and mainly over the east sections of the islands each day. Good
pooling of tropical moisture along with diurnal heating and local
effects each afternoon will support convective development, with
potential for isolated thunderstorm development in some areas. Under
a general southeast steering flow today, the focus of the afternoon
convection should be along the central interior and northwestern
sections of the islands and just downwind. Streamer-like showers
with an isolated thunderstorm will remain possible in and around the
San Juan metro area. Winds are forecast to become more easterly on
Thursday and Friday so activity should be more over the west
interior sections of Puerto Rico and on the west end or downwind of
the U.S. Virgin Islands. The potential for minor urban and small
stream flooding as well as ponding of waters on roadways and in poor
drainage areas will therefore continue through the forecast period
each afternoon.

.LONG TERM...Saturday through Thursday

A unsettle weather patter is expected to prevail for the first
part of the long term period as a lingering tropical moisture
prevail over the region. According to the model guidance plenty
of tropical moisture will be present in the low and mid layers
increasing the potential for more widespread shower activity for
the weekend. In the upper levels, a building upper level trough
(TUTT) will sink into the south inducing a surface trough at our
north on Saturday . Generally speaking, a unsettle weather pattern
is expected on saturday through at least late Monday. Therefore,
urban and minor flooding is expected in the areas with the
heaviest showers.

On Tuesday, once again the GFS model guidance suggest cooler
temperatures at 500 mb increasing the potential for shower and
thunderstorm activity. The limiting factor for a more widespread
showers will be the lack of moisture over the area as a more drier
airmass filter into the region. Additionally, a building surface
high pressure will dominate the easterly wind flow over the
region. Nevertheless, afternoon convection still possible on
Tuesday due to the combination of diurnal heating and the local
effects. This activity will be focus over the interior and
western sections of Puerto Rico in the afternoon hours.On
Wednesday and thursday, a more fair weather pattern is expected as
less moisture with precipitable waters values around 1.5 inches
dominate the forecast area.


&&

.AVIATION...VFR conds expected thru the prd. SCT ocnl BKN lyrs nr
FL020...FL050 with SHRA ovr regional waters and en route btw local
islands til 18/13Z with brief Mtn Top obscr in SHRA/low cld lyrs ovr
Ern PR. Winds will be calm to light and variable bcmg E-SE 10-15
knots with sea breeze variations aft 18/14Z. SHRA/Isld TSRA psbl at
TJBQ/TJSJ/TIST/TISX fm 18/17z-18/22z with VCSH elsewhere. L/lvl wnds
fm ESE BLO FL150 then backing and incr w/ht ABV.

&&

.MARINE...

Mostly tranquil marine conditions are forecast for today with
seas between 3 to 5 feet and winds up to 15 knots across the
regional waters. A moderate easterly wind flow will dominate the
marine pattern until a northerly swell enter into the region on
Friday resulting in hazardous marine conditions. An increase in
shower and thunderstorms activity is expected for today over the
regional waters as a tropical moisture move into the area.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 76 86 77 / 50 30 30 40
STT 86 76 86 77 / 50 40 50 50

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
501 AM AST Thu Nov 19 2020

.SYNOPSIS...
A tropical wave with axis now between eastern Puerto Rico and the
U.S. Virgin Islands will aid in enhancing shower activity across
the regional waters during the rest of the early morning hours,
This along with a slight erosion of the upper level level ridge
will help to destabilize the upper levels and provide sufficient
support for the development of afternoon and early evening
convection in and around the islands for the next few days. Quick
passing showers can be expected to primarily affect to coastal
waters and east coastal sections of the islands, followed by
afternoon convection over parts of the interior and west section
of Puerto Rico and the west end of the USVI.

&&

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

According to the satellite imagery data, precipitable water values
over the forecast area are near normal between 1.8 to 2.0 inches.
This tropical moisture is product from the previous tropical wave
now located well at our west. Thereafter, later today another tropical
wave is forecast to move over the area increasing more the moisture
at least until Saturday afternoon. As the axis of the tropical wave
move into the area an increase in the coverage and intensity of the
showers are expected.

For today, as the axis of the tropical wave move into the region a
northeasterly component in the winds will push the shower activity
mostly over the southwestern quadrant of Puerto Rico in the afternoon
hours. On Friday, one time the axis of the aforementioned wave
move out of the region a change in winds is expected once again,
this time more from the east-southeast. This change in the winds
will focus the showers and thunderstorm activity over the northwestern
quadrant of Puerto Rico on Friday. Given the southeast component
in winds, afternoon convection is forecast over san Juan metro
area. Generally speaking, Friday is forecasted to be the most wet
day in the short term period. That said, urban and small stream
flooding could not be ruled out each day.

On Saturday, according to the model guidance lingering moisture
are expected to continue over the forecast area. In addition, a
upper level trough located well at north sinking to the southeast
will result instability in the upper level enhancing the potential
for shower activity. Therefore, another active day is expected
with scattered showers and isolated thunderstorms in the afternoon
hours due to the combination of the moisture with the local effects.
The limiting factor for the intensity and coverage of the showers
will be the content of moisture over the area.

.LONG TERM...Sunday through Friday...

The proximity of a mid to upper level trough and a induced low
level trough along with a fairly moist southeasterly wind flow
will maintain a a somewhat unsettled weather pattern across the
region from Sunday and at least into early Tuesday. A gradual
drying trend is forecast thereafter, as a high pressure ridge
builds aloft and a surface high will build and become reinforced
across the west and north central Atlantic. This pattern will help
to promote a prevailing east to northeast wind flow and a gradual
erosion of low level moisture.

For the first part of the period lingering tropical moisture and
the instability aloft will help to enhance early morning and
afternoon showers and isolated thunderstorms across the region.
Through Tuesday, the GFS model guidance continued to suggest cooler
temperatures at 500 mb, consequently favoring the potential for
enhanced shower and thunderstorm development in isolated areas.
In addition, under the dominant southeasterly wind flow the shower
activity and afternoon convection should be focused over parts of
the central interior and northwest to north sections of Puerto
Rico, and the west sections or just downwind of the U.S. Virgin
Islands. Recent model guidance continued to suggest high precipitable
water values between 1.70 to 2.0 inches for the early part of the
period, indicating sufficient tropical moisture availability in
the low and mid layers. This should maintain the potential for
shower development during the early part of the period. This
overall weather pattern will favor an unsettled weather pattern
at least until early Tuesday as previously mentioned. Therefore
the potential for minor urban and small stream flooding as well
as ponding of water on roadways an in poor drainage areas across
the islands will continue.

By Wednesday and into Friday...a building surface high pressure
along with mid to high pressure ridging aloft will promote stable
conditions aloft and a gradual erosion of low level moisture. As
the winds become more east northeast, a drier airmass will filter
in and less frequent overnight and early morning showers activity
can be expected. By then, more seasonal weather conditions are so
far forecast, with afternoon convection mainly due to the combination
of diurnal heating and local effects. The activity should then be
focused along the interior and west to southwest sections of Puerto
Rico. Elsewhere, pleasant conditions and a mostly fair weather
pattern is expected as less moisture as precipitable water values
drop to around 1.5 inches or so across the forecast area.

&&

.AVIATION...
Mostly VFR for all the TAF sites. Due to the passing showers,
expect VCSH for TJSJ, TIST, TISX, and TNCM now through 19/12z.
Tropical moisture accompanying a tropical wave will result in
SHRA and VCTS over TJBQ/TJMZ/TJPS fm 19/18Z-19/22Z. Winds will
continue VRB for most of the TAF sites, then increase and become
more east- southeast between 10-15 mph aft 19/14Z.

&&

.MARINE...

A tropical wave will continue to cross the regional waters bringing
periods of showers and possibly isolated thunderstorms to portions
of the local waters today. Seas will become choppy and hazardous
later tonight through Friday, as a long period swell will arrive
and spread across the local Atlantic waters. By then a small
craft advisory will be in effect for the offshore Atlantic waters.
Small craft operators should then exercise caution over the rest
of the Atlantic and local passages.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 76 86 75 / 40 40 50 30
STT 86 77 85 76 / 40 50 60 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
502 AM AST Fri Nov 20 2020

.SYNOPSIS...
Low to mid level moisture trailing a Tropical wave now exiting
the Mona passage will aid in the development of shower activity
across the regional water during the rest of the morning hours.
Passing showers will continue to reach parts of the north and east
coastal sections of the islands from time to time steered by the
prevailing easterly winds. Lingering pockets of moisture over the
islands will again favor locally and diurnally induced afternoon
convection mainly over parts of the interior and west sections of
Puerto Rico. Mostly fair weather skies is expected elsewhere and
over the U.S. Virgin islands but a few brief showers will be
possible on the west end and just downwind of the islands.

&&

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

At the low level an easterly wind flow will continue to push over
the region lingering moisture from the departing tropical wave now
approaching Hispanola. In the upper levels, a weak high pressure
will continue to dominate the region, while in the mid levels a
short wave trough will continue to move southwest and just north
of the region. This will increase the potential for shower
activity over the forecast area. According to the satellite
imagery data, precipitable water values over the forecast area are
nearing normal between 1.7 to 2.0 inches and a somewhat drier
airmass is expected to filter into the region.

For today, a more east to southeasterly wind flow is
expected.This wind flow will push the shower activity to the north
and northwestern quadrant of Puerto Rico in the afternoon hours.
Also, increase the potential for streamers development specially
over the northeastern sections of Puerto Rico reaching the San
Juan Metro area. Therefore, ponding of water over roadways and in
poor drainage area is expected, as well urban and small stream
flooding with the heaviest showers. There is a slight chance of
thunderstorms activity with the well organized convection today
and Saturday. On Sunday, the short wave trough will continue to
sink over the region, resulting in a weakening of the trade wind
inversion over the area. However, the combination of low level
moisture associated with a weakening surface trough, diurnal
heating and the local effects, afternoon convection is forecast to
occur over western and interior sections of Puerto Rico each day.
For the U.S. Virgin Islands, mostly fair weather conditions are
expected for through Sunday. However, passing showers will affect
the local islands in the morning and evening hours each day.

.LONG TERM...Monday through Saturday...

A mid to upper level trough will move north of the region through
through Tuesday as a high pressure ridge will build aloft. The
aforementioned surface trough will also continue to weaken across
the area through Tuesday as a high pressure ridge will build across
the north central Atlantic and gradually sink southwards across
the region. This overall scenario will result in an gradual drying
trend by the middle of next week, as the ridge builds aloft and a
surface high also strengthens and become reinforced across the
west and north central Atlantic. This pattern will help to promote
a prevailing east to northeast wind flow and a gradual erosion of
low level moisture.

That said, for the first part of the period lingering tropical
moisture and sufficient instability aloft will help to enhance
early morning and afternoon showers and isolated thunderstorms
across the region through Tuesday. In addition, under the dominant
east southeast wind flow, afternoon shower activity should be focused
over parts of the central interior and west to northwest sections
of Puerto Rico, and the west sections or just downwind of the U.S.
Virgin Islands. The potential for minor urban and small stream
flooding as well as ponding of water on roadways an in poor drainage
areas across the islands will therefore continue into Tuesday.

By Wednesday and through Saturday...the building surface high
pressure across the west and central Atlantic along with mid to
high pressure ridging will promote stable conditions and a gradual
erosion of low level moisture along with the strengthening of the
trade wind cap inversion. As the winds become more east northeast,
a drier airmass will filter in and spread across the region favoring
less frequent overnight and early morning showers activity. This
will result in a more seasonal weather pattern, with isolated to
scattered afternoon shower development convection mainly due to
daytime heating and local sea breeze convergence. The activity
should then be focused over the interior and west sections of
Puerto Rico. Elsewhere, mostly fair weather and overall sunny
skies should prevail for the latter part of the period as model
guidance suggests layered precipitable water values to drop to
around 1.5 inches across the forecast area due to limited moisture
advection.

&&

.AVIATION....Mainly VFR conditions expected. As lingering moisture
move over the region, shower and isolated thunderstorms are expected
across northwestern and San Juan metro area. SHRA and VCTS will be
required around TJBQ, TJSJ, and also TJMZ around 20/17Z to 20/22Z.
In the night hours, passing showers are expected over TIST, TISX,
and TJSJ. Winds will be VRB at least until 20/13Z, them becoming
more east-southeast between 10-15 mph with sea breeze variations
for most of the TAF sites.

&&

.MARINE...Across the regional waters, seas building to 6 to 8
feet are expected today and into the weekend due to the arrival
of a northerly swell which will spread across the Atlantic waters
and local passages. Seas of 4 to 6 feet are forecast for the rest
of the Caribbean waters. A Small craft advisory is in effect for
the outer Atlantic waters today and will go into effect for the
remainder of the Atlantic waters and passages later this evening.
Small craft operators should exercise caution elsewhere. Please
refer to the latest Coastal Waters Forecast (CWFSJU) and Marine
Weather Message (MWWSJU) for additional info and updates.

There is a moderate to high risk of rip currents for the northwestern
to northeastern beaches of Puerto Rico today. Please refer to the
latest Coastal Hazard Forecast (CFWSJU) for additional info and
updates.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 76 86 75 / 50 30 50 40
STT 85 76 85 75 / 50 40 50 50

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
508 AM AST Sat Nov 21 2020

.SYNOPSIS...
Mostly fair weather conditions are expected during the weekend.
A seasonal weather pattern will take place this week as a drier
air mass filters in across the region. However, low level
moisture combines with local effects to promote showers and
possible isolated thunderstorms in the afternoon hours over
interior and western sections of the islands. Seas will continue
to be choppy and hazardous through the weekend, due to a long
dominant period swell across the Atlantic waters and local
passages.


&&

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

A weak cut-off low in the western Atlantic across 30 degrees north
will be absorbed into the west southwest flow today and tomorrow.
High pressure will continue over South America and the Caribbean sea
with moderate westerly flow. At mid levels high pressure dominates
the eastern Caribbean and the central Atlantic. While at lower
levels, east southeast to southeast flow continues at lower levels
until Tuesday.

Precipitable water will fluctuate between 2.1 and 1.6 inches during
the period, with a dryish period mainly on Sunday. These
fluctuations will be mainly due to streaks of low-level moisture
that cross through the area in the southeasterly flow. On Tuesday,
the GFS keeps southeast flow at 850 mb until after 24/18Z, and at
this time the daily warm north coast temperatures appear to continue
and the afternoon showers and isolated thunderstorms maintained over
northwest Puerto Rico each afternoon. Also overnight and morning
showers will bring accumulations of one tenth to one half inch along
the slopes of southeast and east Puerto Rico with lesser amounts in
the islands to the east.

MOS guidance has been a little too cool especially in the San Juan
Metro area where southeast winds have allowed temperatures to run 2
to 3 degrees above the forecast. Therefore have added somewhat
warmer temperatures along the north coast and in the Greater San
Juan and Bayamon Metropolitan areas. Elsewhere showers and sea
breezes should keep temperatures in the low to mid 80s up to 1500
feet. Isolated temperatures of 90 degrees may be seen inland from
the coast of these areas before showers or sea breezes can bring
relief.

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

A gradual drying trend is forecast by mid week across the region.
The mid to upper level trough will continue to weaken over our north
as a high pressure establishes aloft. At the surface, a high
pressure ridge over the central Atlantic strengthens and sinks
southwards across the area, while a trough builds just east of
the Leeward Islands, causing the low level flow to flip and
become east northeast Tuesday afternoon.

Low-level moisture embedded in the trade winds will combine with
sufficient instability aloft to promote passing showers on Tuesday
morning. Afternoon convection will focus over interior and
northwestern Puerto Rico, resulting in shower and isolated
thunderstorm activity. This activity is expected to cause at least
ponding of water on roadways and low laying areas over parts that
will experience the most persistent rains.

Winds will shift more to the east northeast by Wednesday and
Thursday. A drier airmass will filter in across the region through
much of the rest of the long term period. This will limit shower
activity each morning. However, afternoon convection is expected
to develop mainly due to daytime heating and local sea breeze
convergence. The activity will focus over the interior and west
sections of Puerto Rico. Elsewhere, mostly fair weather conditions
should prevail.

&&

.AVIATION...

SHRA cont over the local waters with ocnl SHRA over ern
PR tapering off by 21/16Z. However SHRA will spread west ovr the
rest of interior PR aft 21/16Z with isold TSRA in NW PR till 21/21Z
accompanied by brief MVFR and mtn obscurations. Sfc winds ESE 10-15
mph with gusts to 25 kt psbl spcly arnd SHRA. Land breeze influences
will prevail til arnd 21/15Z, but some areas on the north coast of
PR may cont to have offshore flow. Max winds W-WNW 30-45 kt btwn
FL320-480 strongest at FL345.

&&

.MARINE...

Hazardous seas up to 8 feet expected to continue across much of
the local waters, associated with a northerly swell that is
pushing into the area. Winds will be up to 20 knots this weekend.
Thus, there are small craft advisories in effect. Choppy
conditions are likely elsewhere. At the local beaches,there is
a high risk of rip currents for the northern coast of PR, Culebra
and NW St Thomas. There is a low to moderate risk of rip currents
at most other local beaches.



&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 75 88 75 / 70 50 40 50
STT 85 76 85 76 / 60 60 40 60

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
456 AM AST Sun Nov 22 2020

.SYNOPSIS...

Near-normal moisture and a slight increase in the favorability of
the upper level dynamics will support a typical pattern of
afternoon convection and passing showers during the nights and
mornings through Tuesday. A more stable weather pattern will
return Wednesday when a high pressure ridge over the central
Atlantic stalls over the forecast area. Hazardous marine
conditions continue through Monday night for the offshore
Atlantic waters.

&&

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

At upper levels high pressure continues over the southern
Caribbean sea and the northern coasts of South America and high
pressure dominates the mid-levels over the local area and extends
northeast into the Atlantic.

At lower levels high pressure across the central Atlantic extends
south over the tropical Atlantic and the northeastern Caribbean,
while a weak low pressure is found over the Bahama Islands. This
low moves north and joins a front leaving the eastern United
States Monday and Tuesday. This maintains east southeast to
southeast low level flow through most of the period. When the
trough moves into the west central Atlantic low level flow will
become east northeast over the area. This will bring cooler air
beginning late Tuesday afternoon.

.LONG TERM...Wednesday through Monday...

The high pressure ridge over the central Atlantic will transport
drier air that will filter in across the region on Wednesday.
This relatively stable weather pattern will hold through much of
the long term period. The trough just east of the Leeward Islands
will promote a shift in winds now more to the east northeast. This
will result in pleasant temperatures across the islands with highs
generally in the mid 80s in the lower elevations.

Precipitable water values are forecast to be below normal.
However, isolated showers can not be ruled out each morning across
the eastern quadrant of Puerto Rico and U.S. Virgin Islands.
Also, the moisture confined in the low levels, local, and diurnal
effects could produce a few showers during the afternoons. Showers
that do develop will be short-lived and produce light rainfall
amounts. This activity will focus over the interior and west
sections of Puerto Rico.

Current model guidance suggest an increase in moisture content
by the beginning of the workweek. This will aid in the
development of showers across the islands. Thus, expect early
morning passing showers in and around the islands and then
afternoon convection for parts of interior and western Puerto
Rico.

&&

.AVIATION...VFR conds are expected to prevail at all TAF sites.
Brief MVFR CIGs due to SHRA are psbl at TNCM/TKPK before 22/16Z
and at TJBQ btwn 22/17-21Z with some mtn obscurations. Sfc winds
incrg to 10-15 kts with hir gusts near the coasts and near SHRA.
Winds will be ESE with sea breeze influences til arnd 22/22Z. Max
winds WNW 30-45 kt btwn FL345-520, strongest at FL465.

&&

.MARINE...

Seas are expected to gradually continue subsiding into Monday.
However, due to seas between 5 and 7 feet across the Atlantic
waters, the small craft advisory will remain in effect until
Monday night. Elsewhere, seas will be generally between 3 and 6
feet. Small craft should exercise caution. There is a high risk
of rip currents across the north coast of PR and northern Culebra,
while most other beaches of PR have a moderate risk. All beaches
of the USVI have a moderate risk of rip currents.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 87 76 / 50 50 40 30
STT 85 77 85 75 / 40 50 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
513 AM AST Mon Nov 23 2020

.SYNOPSIS...Drier air is moving toward the forecast area, but an
axis of very good moisture remains over Puerto Rico this morning.
Southeast surface flow will continue through Tuesday, but
afterwards flow will be east northeast into next week. Some
afternoon showers are expected each day, but diminishing
considerable by Friday.

&&

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

A relatively moist environment should persist through Tuesday. A
surface high pressure over the central Atlantic along with a frontal
trough well north of the region will promote an east southeast to
southeast windflow. Precipitable water estimated by the models
is near to just above normal values. Thus, passing showers are
expected to continue during the morning hours across portions of
eastern and southern Puerto Rico. Some rivers are running well
above base flow in southeast and east central Puerto Rico and
ponding of water in low lying areas is expected this morning. Somewhat
favorable dynamics aloft and moisture confined in the low levels
are expected to support locally induced afternoon convection over
interior and northwestern quadrant of Puerto Rico. Shower activity
cannot be ruled out downwind from El Yunque, and therefore the
San Juan metro area could also observe active weather during the
afternoon hours. Isolated showers are expected elsewhere. Rainfall
accumulations could be enough to cause minor urban flooding over
parts that will experience the heaviest and most persistent rains.
Southeast flow on tuesday morning will also bring some more
limited shower activity.

By Wednesday, a mid-to-upper level high pressure moves over the
region, enhancing a strong trade wind inversion and the erosion of
the available moisture. Thus, expect a drying and more stable
weather pattern. Surface winds will shift more to the east
northeast resulting in pleasant temperatures.

.LONG TERM...Thursday through Sunday...
A weak low pressure that has been developing north of the Bahama
Islands today, will be absorbed into a strong trough moving into
the Atlantic from the northern United States. That low will be
followed by a moderately strong high pressure that will push the
low into the central Atlantic. On Wednesday it will split into two
parts, one which will continue northeast and the other which will
move south southwest. Under the influence and enhanced by, a
developing mid to upper level low, that surface low will settle
to a position 860 miles northeast of Saint Thomas. This low
pressure juxtaposed with the surface high that will remain over
the western Atlantic Thursday through Sunday, will maintain
northeast to east northeast flow over the local area.

During this time available moisture will be decreasing through
the entire period today through Sunday. By Thursday moisture will
be confined to 700 mb and by Saturday to only 800 mb, with very
dry air above it all the way to the stratosphere. This will limit
afternoon convection especially Friday and over the weekend. Some
showers are expected along the windward slopes Thursday and
Sunday mainly during the overnight and early morning hours.

Owing to the east northeast flow, temperatures along the northeast
coast will moderate, while high temperatures along the southwest
coast and especially around Guanica will remain in the upper 80s
to near 90 degrees.

&&

.AVIATION...Mainly VFR conds expected for all terminals. Tempo
MVFR possible due to SHRA across TJSJ and TJPS. Passing showers
will lead to continuing VCSH/SHRA conditions through at least
23/11Z for TJPS and TJSJ. A round of afternoon convection is
expected today, and VCSH conditions are expected after 23/14Z at
TJSJ and 23/16Z at TJBQ. Sfc winds bcmg by 23/14Z ESE 8-12 knots.
Max winds WNW 35-45 kts btwn FL370-520 strongest at FL400.

&&

.MARINE...Seas are slowly diminishing across the area. However
seas are still running 7 to 8 feet at the outer buoy, 41043 in
easterly waves. This will hold the outer Atlantic waters at or
above 7 feet until tonight after midnight. Small craft will need
to exercise caution elsewhere in unprotected waters. The high rip
current risk will diminish to moderate this morning for all
beaches. Beaches south of Rincon on the west coast and a few
beaches in the Ponce area will have a low risk of rip currents
today.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 76 86 76 / 40 40 40 30
STT 85 75 86 75 / 20 30 20 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
503 AM AST Tue Nov 24 2020

.SYNOPSIS...A shearline will move through Puerto Rico and the U.S.
Virgin Islands today and tonight, bringing drier weather and
clearing skies. After showers and isolated thunderstorms in the
northwest today, flow will turn east northeasterly and conditions
will become sunnier with few showers Thursday through early next
week.

&&

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

A surge in low level moisture has reached the area and is expected
to enhance shower activity today. Southeasterly trade winds will
advect groups of showers from time to time over the southern and
eastern portions of Puerto Rico and the U. S. Virgin Islands during
the early morning hours. Then, winds will shift more to the east
northeast causing afternoon shower activity to focus mainly over
parts of center and western Puerto Rico. Somewhat favorable upper
level dynamics, with 500 MB temperatures reaching -7C degrees, could
aid in the development of isolated thunderstorm activity The main
threat for these areas will be urban and small stream flooding with
the heaviest and most persistent rains.

A drier trend is forecast thereafter, with precipitable water values
dropping to lees than 1.00 on Thursday. However, passing showers
moving from the waters into portions of northern and eastern
Puerto Rico, as well as the U.S. Virgin Islands cannot be ruled
out. Models are forecasting a northeast to east northeast flow
over the local area due to the low pressure together with the
surface high over the western Atlantic.

.LONG TERM...Friday through Monday...
A low pressure that cut-off from a passing long wave trough in
the central Atlantic at upper levels will enhance a low pressure
at mid and lower levels a few hundred miles west of the upper low
or about 630 miles north northeast of Saint Martin. This and high
pressure wedging into the western Atlantic from a high that moved
into the central Atlantic will cause northeasterly flow at lower
levels Friday and over the weekend. The boundary between the warm
moist air from the tropics and this air will sink into the central
part of the Caribbean such that cooler and drier air will
dominate for the duration of the long term period. In fact, the
GFS shows precipitable water values falling below 1.25 inches and
not recovering before Tuesday night. Although some showers in the
diurnal cycle typical for Puerto Rico may occur, they will be
isolated and shallow. Thunderstorms are very unlikely in this
environment and there should be a preponderance of sunshine each
day. Although the air will be cooler, sunshine will keep maximum
temperatures in the mid to upper 80s in the lower elevations of
both Puerto Rico and the U.S. Virgin Islands.

&&

.AVIATION...Mainly VFR conds expected for all terminals. Brief VCSH is possible,
but no major impact to operations and visibilities to the local
airports are expected. Isolated to Sct SHRA across the Caribbean
waters could move into southern PR and USVI from time to time
through the period, resulting in VCSH across TJPS/TIST/TISX. Winds
will continue from the ESE-SE up to 10 kts, but shifting to the ENE-
NE aft 24/14Z. Maximum winds WNW 35-50 kt btwn FL360-500
strongest at FL480.

&&

.MARINE...Easterly swell and moderate winds are making seas
choppy in the outer Atlantic waters and the Anegada Passage,
otherwise seas will continue to relax until Thursday. On Thursday
hazardous seas are expected to return to the outer Atlantic
waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 76 85 76 / 30 30 40 40
STT 85 75 86 75 / 20 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
504 AM AST Wed Nov 25 2020

.SYNOPSIS...Northeasterly flow will bring a cooling and drying
trend that will last through Monday. Rains in this flow will taper
off on Thursday. High pressure will continue at mid and upper
levels with weak waves passing through Sunday and Tuesday.

&&

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

Today is a transitional day to a drier weather pattern. The pre-
frontal trough will pull apart and move away from our region while a
high pressure coming from the U.S. east coast stalls over our area.
This will gradually promote stable conditions in general for the
next few days. Also, this will result in a northeast wind flow and
thus, pleasant temperatures can be observe over the islands.
Leftover moisture associated with the prefrontal trough will
continue to promote showery weather over coastal parts of northern
Puerto Rico and U.S. Virgin Islands through the morning hours. With
the northeasterly windflow and diurnal heating, showers are expected
to develop over parts of southwestern Puerto Rico in the afternoon
hours. However, rainfall accumulations are not expected to lead
urban and small stream flooding, but only ponding of water on
roadways and low laying areas that will experience the heaviest
rains. This activity is expected to diminish by sunset.

Mid to upper levels will be drier towards the end of the workweek.
This will result in limited shower activity over the islands. Any
shower activity is expected to be short-lived and produce light
rainfall amounts, if any.

.LONG TERM...Saturday through Tuesday...
High pressure over the southwestern Caribbean at upper levels
will hold west northwest flow over the area through the period.
Some weak shortwaves will move through Sunday and Tuesday. High
pressure at mid levels will continue over the Caribbean through
the period. At lower levels, troughing with a weak low pressure
650 miles northeast of Aguadilla, Puerto Rico on Saturday will
move to the east in response to a high pressure over Nova Scotia
and the western Atlantic. This will cause northeast flow near the
surface to become more easterly during the period. the transition
will mark the end of a 5 day cooling trend, but moisture will
delay its return until Tuesday and Wednesday. Temperatures will be
quite moderate on the north coast, but a little warmer than normal
on the south coast of Puerto Rico. With such shallow moisture in
the lower levels showers, if any, will be isolated Saturday
through Monday with scattered showers returning to the eastern
end of Puerto Rico on Tuesday in the moistening easterly flow.

&&

.AVIATION...SHRA activity across northern PR is resulting in -RA
across TJBQ and VCSH across TJSJ. TEMPO MVFR conditions at times
due to BKN ceilings and reduced visibilities over TJBQ through
25/10z. Light and variable winds overnight bcmg from the NE-ENE
up to 10 kts aft 25/14z. Max winds WNW 35-46 kt btwn FL380-510
strongest at FL480.

&&

.MARINE...Winds behind a front in the western Atlantic will
generate a northerly swell that is set to arrive late Wednesday
night and Thursday. Seas will peak Thursday night and then slowly
subside, with no small craft advisories remaining by Friday night.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 75 86 75 / 50 40 40 20
STT 87 77 86 75 / 20 20 20 10

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
429 AM AST Thu Nov 26 2020

.SYNOPSIS...

A mid-level ridge will continue to build over the area today and
hold through the weekend. A drier air mass will maintain its grip
over the local islands now through the weekend. The drier air
mass will promote relatively calm weather over the region; with a
few showers developing during the afternoon due to Local and
diurnal effects.

&&

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

Showers in a northeasterly steering wind flow persisted through
the overnight hours across the north central and northwestern
sections of Puerto Rico. The doppler radar estimated between half
to near an inch of rain across the northern coastal areas of PR.
Overnight temperatures were in the mid 60s across the interior and
in the mid 70s across coastal areas. Although a drier air mass is
present above 700 mb, moisture trapped below will continue to
stream in a 10-15 kt NE trade wind flow across the region today.
This will be enough to cause scattered trade wind showers to
continue through the morning hours across the northern sections of
PR and mainly isolated activity across the U.S. Virgin Islands
and eastern PR.

For this afternoon, the combination of the low-level moisture with
daytime heating and the sea breeze convergence will cause showers to
develop over the southwestern quadrant of PR. Streamer type of
rainfall activity is expected downwind of the USVI and over eastern
PR. A drying trend is forecast to continue on Friday, and a similar
weather pattern should continue across the islands. However, less
rainfall activity is expected. For Saturday, another area of showers
is expected to move from the Atlantic waters into the northern
sections of PR and across portions of the USVI during the early
morning hours. This surge in low-level moisture once again will aid
in the development of diurnally induced afternoon showers over
portions of the interior and southwestern PR.

&&

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

Currently, global models show a relatively tranquil long-term
period with patches of moisture advecting over the area from time
to time. High pressure in the low to mid-levels of the atmosphere
will hold through the period. However, the surface high pressure
will fluctuate in intensity due to several short-waves that will
develop over the Atlantic waters.

Saturday, ENE will pull a drier air mass from the northwestern Atlantic
into the area; the drier air and limited moisture will thwart the
development of deep convection over the region. The GFS and EURO
keep the drier air over the area through early next week.

The EURO diverges from the GFS on Monday. The EURO lifts moisture
from the Caribbean waters into the local islands, and the GFS
keeps the drier air across the region through late Tuesday. At the
beginning of the period, the moisture content is forecast to be
two standard deviations below normal for November, with totals
ranging from 0.7 to 1.0 inches across the region. However, by the
middle of the week, an increase in moisture is expected. The
moisture coupled with local and diurnal effects will boost showers
over Puerto Rico and the local islands.

Forecast Confidence: Medium

&&

.AVIATION...

Mainly VFR conditions are expected to prevail across all
terminals. However, SHRA is expected to develop over the south-
southwestern sections of PR btw 16z-22z, this could cause tempo MVFR
cigs at TJPS. Low level winds NE at 10-15 kts, with sea breeze
variations expected aft 14z across the southern terminals.

&&

.MARINE...

A northerly swell is impacting the Atlantic waters and will
continue to spread across the local waters today. East to
northeast winds will continue to prevail over the local waters
through the weekend. A Small Craft advisory is in effect for the
offshore Atlantic waters and the Mona Passage. A Small Craft
advisory will be in effect for Puerto Rico near-shore waters
later today. There is a high risk of rip currents for the western,
eastern, and northern beaches of Puerto Rico.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 75 85 75 / 20 40 20 30
STT 86 75 84 75 / 40 20 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
410 AM AST Fri Nov 27 2020

.SYNOPSIS...

Mid-level ridge will persist over the area through most of the
forecast period and keep a drier air mass entrenched over Puerto
Rico and the U.S Virgin Islands through early next week. The drier
air and ridging will promote fair weather conditions through Monday,
with a few isolate showers possible due to local and diurnal
effects. Late Tuesday into Wednesday, a deepening trough east of
Florida will cause the mid-level ridge to buckle; and create
troughiness aloft north of Puerto Rico. The weakening of the mid-level
ridge and troughiness north of the area will promote an increase
in convection for Puerto Rico and the U.S. Virgin Islands.

&&

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

A mid-level ridge over the western Caribbean will continue to build
across the region through the short term period. This should
continue to promote drier air and stable conditions aloft through
the weekend. A weak high pressure over the western Atlantic and
surface low to our northeast will continue to promote northeasterly
trades for the next several days. Trapped in this flow, areas of
shallow moisture will continue to stream from the Atlantic waters
across the islands, resulting in passing light showers across the
northern and eastern sections of Puerto Rico and the U.S. Virgin
Islands during the night and early morning hours. During the
afternoon hours, the combination of the sea breeze convergence with
this moisture and daytime heating will cause showers to develop over
the south/southwestern portions of PR and downwind of the USVI. This
weather pattern is forecast to hold today, with a slight increase in
showers early on Saturday morning. Sunday continues to be the driest
day in the forecast, with light showers developing over the same
areas over south/southwest PR.

&&

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

The GFS and EURO continue to show drier air and relatively tranquil
weather at the beginning of next week, followed by a return in
moisture at the end. A surface and mid-level high pressure will
influence the local climate by strengthening the trade wind cap and
producing east to northeast wind flow across the area. The east to
northeast winds will pull drier air from the Atlantic waters into
the region. The above conditions will inhibit the development of
deep convection. Still, patches of shallow moisture moving in from
time to time and local and diurnal effects will help develop shallow
convection mainly during the afternoon.

Wednesday and Thursday, the GFS has an Upper-level low and a
negatively titled trough near the Great Lakes. The upper-level low
is forecast to deepen and push a frontal boundary through central
Florida and another into the Atlantic Waters. As the trough moves
into the western Atlantic, it will weaken the mid-level ridge
that has dominated the local weather and allow moisture from the
Atlantic waters to advect into the area.

Thursday, the GFS develops a weak perturbation north of Puerto Rico
and brings a wind surge with moisture into the region. The weak
perturbation and moisture increase will cause an uptick in shower
activity for Puerto Rico and the U.S. Virgin Islands through Friday.

Forecast Confidence: Medium

&&

.AVIATION...

Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. SHRA is expected to develop over
the south-southwestern sections of PR btw 18z-22z, this may cause
tempo MVFR conditions at TJPS. Winds ENE at 7-12 kts, with sea
breeze variations expected aft 14z across the southern terminals.

&&

.MARINE...

A northerly swell will continue to create choppy to hazardous
seas across the Atlantic and local waters through this evening.
Seas will range from 5 to 8 feet. Small craft advisories are in
effect for these waters. Seas across the Caribbean waters are up
to 5 feet. A high risk of rip currents is also in effect for the
northern beaches of Puerto Rico and Culebra as well as the
northwestern beaches of Saint Thomas. Winds will be from the east
to northeast ranging from 5 to 10 kts.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 85 76 / 20 40 30 10
STT 84 75 84 76 / 30 30 40 20

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
408 AM AST Sat Nov 28 2020

.SYNOPSIS...A mid-level ridge will continue to influence the local
weather conditions through next week. East to northeast trade
winds will bring areas of shallow moisture from the Atlantic
waters, resulting in passing showers at times across the northern
areas of PR and the USVI, followed by limited afternoon shower
development over portions of the interior and west/southwest PR.
Seas will improve by Sunday and remain relative tranquil through
next week.


&&

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

A dry stable air mass and ridging aloft will promote fair weather
for Puerto Rico and the U.S. Virgin Islands through the short-
term period. Deep convection is not forecast to develop during the
period due to the mid-level ridge creating substance in the
atmospheric mid-levels, lack of significant synoptic features, and
shallow moisture.

GOES-16 total precipitable water shows a slender patch of moisture
just north of Puerto Rico this morning. East to northeast wind flow
will pull the moisture across northern coastal areas of Puerto Rico,
producing isolated to scattered showers through the morning hours.

This afternoon high resolutions models shift the isolated to
scattered showers across portions of the interior and northern areas
of Puerto Rico; the convection will develop due to local effects and
diurnal heating.

Sunday and Monday, a drier air mass is forecast to advect into the
region from the east-northeast and influence the local weather.
Guidance shows precipitable water falling throughout the day on
Sunday and bottoming out at 0.7 inches Monday morning, which is far
below average for this time of year. Nevertheless, a few isolated
showers are possible during the afternoon due to local effects.

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

The mid-level ridge is forecast to meander just west of the area
through the long term period. This will continue to promote drier
air and stable conditions aloft. At low-levels, a broad area of low
pressure northeast of the region is forecast to merge with a
frontal system by midweek. This and a weak surface high behind the
front will continue to promote east to northeast trades across
the region. Shallow areas of moisture embedded in this
northeasterly wind flow will reach the islands from time to time,
causing light passing showers at night across the northern
sections of PR and the USVI, followed by limited afternoon shower
development over portions of the Cordillera and southern PR. This
weather pattern is expected to hold through the end of the week.
By Saturday, an upper level low is forecast to develop northeast
of the region, weakening the pressure gradient and promoting
somewhat more unstable conditions during the weekend.


&&

.AVIATION...VFR conds expected across the local terminals. VCSH ARE
possible across terminal sites possible across terminals TJSJ and
TJBQ through 28/15Z. SRHA will continue ovr ATL waters. This
afternoon vcsh/shra will develop across terminals TJSJ and TJBQ
starting at 28/16Z and ending by 29/01Z. Winds will remain from the
E-NE at around 10 KT through the afternoon with sea breeze
variations.


&&

.MARINE...Choppy seas up to 6 feet will continue today across the
Atlantic waters and portions of the local passages. Therefore,
small crafts should exercise caution across these waters.
Elsewhere, seas will range in general from 3 to 5 feet. East-
northeast trades up to 15 knots are expected. There is a high risk
of rip currents across the northern beaches of Puerto Rico.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 85 72 / 50 20 20 10
STT 85 73 85 74 / 40 10 20 10

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
350 AM AST Sun Nov 29 2020

.SYNOPSIS...A mid-level ridge will continue to promote fair
weather conditions across the islands for the next several days.
East to northeast trades will bring occasional passing showers
across the local waters. Mostly minor rainfall amounts are
forecast across the islands. There is a High Rip Current Risk in
effect for the northern beaches of Puerto Rico through late this
afternoon.


&&

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

Ridging aloft and limited moisture content will promote relatively
fair weather across Puerto Rico and adjacent islands through Monday
evening. Precipitable water will remain below the seasonal average
through the period. The ridging aloft coupled with limited moisture
content and significant forcing at the surface and aloft will
suppress robust convection.

Today and Monday, shallow moisture embedded in the east-northeast
winds will cause light showers during the morning hours across
northern and eastern Puerto Rico and the U.S. Virgin Islands. Then
showers over the interior and western areas of Puerto Rico during
the afternoon due to local and diurnal effects. The high-resolution
models have performed well the last several days and have handled
the current weather pattern well. Recent guidance shows showers
developing again over portions of the northern, interior, and
eastern areas of Puerto Rico through Monday.

Tuesday, west of the forecast area, a frontal boundary is expected
to transverse Florida`s peninsula and move into the western Atlantic
waters. The frontal boundary will cause the mid-level ridge to
weaken, resulting in a weakening of the trade wind cap. The above
features will cause a small increase in moisture content over the
area, resulting in an uptick in afternoon convection.

Forecast Confidence: High

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

A mid-level ridge across the Caribbean basin will continue to
dominate the local weather conditions through the long term
period. Below normal precipitable water content between 1.00-1.30
inches is expected from Wednesday through Friday, as drier air
aloft continues to hold across the islands. However, shallow
patches of low-level moisture in a persistent northeasterly wind
flow will reach the islands from time to time. This small surge of
moisture will be enough to cause light passing showers across the
local waters and aid in the development of afternoon showers over
isolated areas of the interior and southern Puerto Rico. No
significant rainfall amounts are anticipated with this activity.
Across the U.S. Virgin Islands, fair weather conditions are
expected with minimal rainfall activity.

During the weekend, the ridge is forecast to gradually weaken due
to a polar trough and associated surface front moving over the
western Atlantic and an upper level trough developing northeast of
the region. However, latest model guidance suggest that this
synoptic weather pattern will not have a significant impact on the
local weather conditions as precipitable water content increases
to just 1.50 inches during this period. Therefore, similar weather
conditions are expected to continue during the weekend with a
slight increase in shower activity over the islands.


&&

.AVIATION...VFR conds expected across the local terminals. VCSH are
possible near terminals TJSJ, TIST, and TISX 29/14Z. Aft 29/14Z sea
breezes in ENE flow with winds of 6-12 kt. VCSH/SHRA over the
interior and eastern PR by 29/15Z and ending by 29/20Z.


&&

.MARINE...Fading northerly swell and moderate northeast winds are
still causing seas to range between 4 to 6 feet across the
Atlantic waters and portions of the local passages. Therefore,
small crafts should continue to exercise caution today. Marine
conditions are forecast to gradually improve during the next few
days. There is a high risk of rip currents across the northern
beaches of PR through late this afternoon.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 72 85 72 / 20 20 20 20
STT 85 74 84 74 / 20 10 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
349 AM AST Mon Nov 30 2020

.SYNOPSIS...A fair weather pattern is expected to prevail across
the area during the next several as relatively drier than normal
air mass and a ridge aloft is expected to generally limit shower
activity. Marine conditions are expected to be tranquil through
the middle of the work week with seas of up to 5 feet expected.

&&

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

A mid to upper-level ridge will hold through the short term period.
This atmospheric feature will promote drier than normal conditions
between the mid-levels and upper-levels. An easterly perturbation
will move across the Caribbean Sea today and tomorrow. However,
the bulk of the moisture will remain far to the south over the
Caribbean. Therefore, fair weather conditions will prevail across
the islands of Puerto Rico and the U.S. Virgin Islands. The
northeasterly wind flow will push pockets of moisture at times
that could bring quick passing showers mainly across the windward
sections, followed by afternoon convection across the interior and
western portions. At this time, model guidance is indicating that
the remnants of a frontal boundary will move across the area on
Wednesday, increasing the low-level moisture and the potential for
observing more frequent showers.

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

A ridge aloft will continue to prevail overhead through the end of
the work week. This feature in combination with a drier than
normal air mass will continue to result in fair weather conditions
across the local islands. Surface high pressure traversing the
western Atlantic will continue to result a northeasterly wind
flow. This will bring shallow patches of low-level moisture into
the area from time to time resulting some light trade wind
showers across portions of northeastern Puerto Rico and in and
around the northern USVI during the overnight and early morning
hours followed by the development of some afternoon showers across
the interior and southwestern quadrant of Puerto Rico.

By the upcoming weekend into early the following week, a polar
trough is expected to amplify and move across the western
Atlantic, weakening the ridge aloft. Along with this polar trough,
model guidance is indicating that a surface low pressure and an
associated front will develop off the east coast of the United
States and move east-northeastward across the western Atlantic. As
the associated surface front moves across the western Atlantic,
the low-level winds are expected to gradually shift from the
southeast to south by late in the weekend into early the following
the week. Even though the ridge aloft is expected to weaken,
moisture is expected to remain generally below normal, therefore,
significant shower activity is not anticipated at this time
during this period.

&&

.AVIATION...VFR conditions will prevail thru the forecast period.
SHRA will move at times across the terminals of PR/USVI without
significant impact. Cloudiness will increase across the interior of
PR and downwind from the USVI between 30/16z-22z. Winds will
continue calm to light and variable, and northeasterly winds will
return at 10-15 kt after 30/13z.

&&

.MARINE...Fairly tranquil marine conditions are expected to
prevail through the middle of the week with seas of up to 5 feet
expected. A northeasterly swell is expected to deteriorate marine
conditions during the second half of the work week. There is a
moderate risk of rip currents for most of the north-facing as well
as some of the east-facing beaches of the islands for today.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 75 85 74 / 20 10 10 30
STT 85 74 84 73 / 20 10 10 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
356 AM AST Tue Dec 1 2020

.SYNOPSIS...A fair weather pattern is expected to prevail during
the next several days due to a ridge aloft and a generally drier
than normal air mass. As a result, shower activity will remain
limited. A northeasterly swell is expected to affect the local
waters during the second half of the work week.

&&

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

The mid to upper-level ridge continues to promote a strong inversion
and drier conditions aloft. Once again, the forecast for today is
fair weather conditions with mostly clear skies and pleasant
temperatures across the islands of Puerto Rico and the U.S. Virgin
Islands. Although the possibility to observe one or two trade wind
showers is low, as well as the development of afternoon convection
across the interior and western sections, this activity does not
represent any hazard.

The remnants of an old front are forecast to increase the available
moisture as well as the chance for passing showers across the
islands early Wednesday morning into the afternoon hours. By
Thursday, after the passage of this feature, stable weather will
return across the islands.

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

The ridge aloft is expected to prevail through at least Saturday.
This feature in combination with a generally drier than normal air
mass is expected to result in mainly fair weather conditions.
Meanwhile, at lower levels, a surface high pressure traversing the
western Atlantic will continue to result in a northeasterly flow
across the area. This will bring patches of low-level moisture
into the area from time to time to result in some brief showers
across portions of northeastern Puerto Rico and the northern USVI
during the overnight and early morning hours followed by the
development of some afternoon showers across interior and
southwestern portions of Puerto Rico.

Later during the weekend into early next week, a broad polar
trough is still expected to move across the western Atlantic and
this feature is expected to gradually weaken the ridge aloft. This
polar trough will also spark the development of a surface low
pressure, which is expected to develop off the east coast of the
United states and move east-northeastward. This low pressure along
with its associated front will weaken the pressure gradient
significantly, causing very light winds. Even though the ridge is
expected to weaken, the moisture content will remain quite limited
with precipitable water values below normal. Therefore, no
significant shower activity is anticipated into early next week.

&&

.AVIATION...VFR conditions will prevail thru the forecast period.
Cloudiness will increase across the interior/W-PR and downwind from
the USVI between 01/16z-22z. Winds will continue calm to light and
variable, increasing between 10 and 15 knots from the NE after
01/13z. Passing SHRA will return aft 01/23z, mainly across the
Atlantic Waters and the VCTY of IST/JSJ/ISX.

&&

.MARINE...Generally tranquil marine conditions are expected
through Wednesday across the regional waters with seas expected to
range between 2 and 5 feet. A northeasterly swell is expected to
affect the local waters during the second half of the work week,
causing choppy seas across the Atlantic waters and local passages.
A moderate risk of rip currents is expected across most of the
north-facing beaches of the islands for today.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 74 84 74 / 10 30 30 30
STT 84 73 85 73 / 10 30 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
414 AM AST Wed Dec 2 2020

.SYNOPSIS...A fair weather pattern will continue to dominate
weather conditions during the next several days as a ridge aloft
and a generally drier than normal air mass will limit shower
activity. A northeasterly swell is expected to affect the local
waters during the end of the work week, resulting in choppy seas.

&&

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

Stable weather conditions due to a mid to upper-level ridge are the
dominant feature. It`s promoting a strong inversion and drier
conditions aloft. However, moisture associated with an old front and
the northeasterly winds will push some clouds and possibly some
quick passing showers across the windward sections of Puerto Rico
and the U.S. Virgin Islands this morning and late tonight into early
Thursday morning. Afternoon convection will develop across the
interior and southwest quadrant of PR as well each afternoon. Stable
weather conditions will continue on Friday with just a few showers
associated with the advection of pocket of moisture from time to
time and isolated to scattered showers due to afternoon convection.
This activity will not represent any hazard that could put at risk
the life and property of the residents of Puerto Rico and the U.S.
Virgin Islands.

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

The ridge aloft will continue to hold into early next week. Even
though a polar trough is expected to move into the western
Atlantic, the latest guidance is indicating that this feature will
not be as highly amplified to cause the ridge to completely weaken.
Therefore, the ridge in combination with a generally drier than
normal air mass will continue to result in a fair weather pattern.

A surface high pressure north of the area during the
weekend will maintain a northeasterly flow. This will bring
occasional patches of low-level moisture to result in some passing
showers across portions of northeastern Puerto Rico and the
northern USVI during the overnight and early morning hours
followed by the development of some afternoon showers across the
interior and southwestern quadrant of Puerto Rico. A surface low
pressure and an associated frontal boundary are expected to move
across the western Atlantic during the early to middle portion of
next week. This feature as it moves across the western Atlantic
will cause the winds to gradually become more east-southeast to
southeast as well as become light as the local pressure gradient
weakens. As mentioned previously, the air mass will continue to
remain generally drier than normal into the middle of next week,
therefore, no significant shower activity is anticipated at this
time.

&&

.AVIATION...VFR conditions will prevail thru the forecast period.
The NE winds will push clouds and possibly a few SHRA/-SHRA at
times. Then, clouds and SHRA/-SHRA will develop over the interior/SW-
PR btwn 02/16z-22z. Winds will continue calm to light and VRB,
increasing around 13 kt from the NE after 02/13z. Passing SHRA will
increase aft 02/23z, mainly across the Atlantic Waters and the
VCTY of IST/JSJ/ISX.

&&

.MARINE...Tranquil marine conditions will continue today with seas
generally expected to remain below 5 feet. A northeasterly swell
is forecast to invade the local waters beginning on Thursday and
lingering into the upcoming weekend. This will result in choppy
seas across the Atlantic waters and local passages. There is a
moderate risk of rip currents for the north-facing beaches of
Puerto Rico and Culebra for today.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 75 84 74 / 30 40 40 10
STT 85 72 85 73 / 30 40 40 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
404 AM AST Thu Dec 3 2020

.SYNOPSIS...

Stable weather conditions will continue due to a mid to upper-
level ridge aloft. This feature will limit rain activity across
the islands, though pockets of moisture could bring some rain
showers at times. A high risk of rip currents will affect the
north and east-facing beaches of Puerto Rico, Culebra, and St
Croix from this evening to tomorrow night.

&&

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

A mid and upper-level ridge will continue to remain the dominant
synoptic feature through the period. This will continue to result in
very dry conditions at the mid and to upper-levels of the
atmosphere. Therefore, a fair weather pattern is expected to prevail
across the local area. Meanwhile, at lower-levels, the combination
of an induced surface trough located northeast of the Lesser
Antilles and a surface high pressure exiting the east coast of the
United States into the western Atlantic will induce a northeasterly
flow through the period. This northeasterly flow will also carry
with it patches of low-level moisture, which will move over the area
from time to time. This will result in some passing showers
affecting portions of northeastern Puerto Rico and the northern USVI
during the overnight and early morning hours followed by limited
afternoon shower activity across southwestern Puerto Rico. Given the
hostile conditions aloft, the shower activity is expected to be
short-lasting with no significant rainfall accumulations expected.
Generally speaking, pleasant weather conditions are expected to
continue across the area into the upcoming weekend.

.LONG TERM...Sunday through Friday...

Stable weather conditions will remain as a mid to upper-level
ridge holds over the islands. A surface-low pressure with its
associated frontal boundary will move across the Western Atlantic
during the weekend. Then, a second low-pressure system moving
near the Carolinas into the Western Atlantic will induce a weak
east-southeasterly wind flow across the islands early next week.
The frontal boundary associated with this low will stall over the
Atlantic Ocean off to the north of PR/USVI Wednesday and Thursday.
That said, and due to a relatively dry air mass, no significant
shower activity is forecast to impact the islands at this time.

&&

.AVIATION...

VFR conds expected across the local terminals. Passing SHRA will
continue to result in VCSH, mainly across TJBQ/TJSJ/TIST through
03/12z. Afterwards, fair wx conditions expected across the area.
Winds light and variable through 03/12z, increasing to 10-15 kts
from the ENE-NE with sea breeze variations after 03/14z.

&&

.MARINE...

A northerly swell will move across the Atlantic and Caribbean
Passages Thursday and Friday. Mariners can expect seas between 4
and 6 feet with occasional seas up to 8 feet across the exposed
Atlantic waters and at 5 feet or less across the protected waters.
Winds will continue around 15 knots from the NE. Beachgoers, this
swell will promote a high risk of rip currents along the north and
east-facing beaches of PR, Culebra, and St Croix from this evening
to tomorrow evening. A second NE swell will move across Sunday and
early Tuesday. A third swell will move in from the northwest
Atlantic late Monday or Tuesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 74 82 74 / 30 20 20 30
STT 83 73 84 73 / 20 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
417 AM AST Fri Dec 4 2020

.SYNOPSIS...

A mid to upper-level ridge is producing stable weather and dry air
aloft. This feature and the lack of tropical moisture will result
in favorable weather conditions with no to little rain activity. A
northeasterly swell will create hazardous rip currents along the
north facing beaches from the northwest to northeast coast of
Puerto Rico, including Culebra and the east-end of St Croix.

&&

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

A similar weather pattern to what has been experienced during the
last several days will continue through the upcoming weekend. A mid
and upper-level ridge will continue to result in very dry conditions
aloft. Therefore, mainly fair weather conditions will prevail across
the local area. Meanwhile, at lower levels, the combination of an
induced surface trough well northeast of the northern Leeward
Islands and a surface high pressure moving into the western Atlantic
will continue to induce an east-northeast to northeast steering
flow. With it, occasional patches of low-level moisture will move
across the area. This will result in some passing showers across
portions of northern and northeastern Puerto Rico and in and around
the USVI during the overnight and early morning hours followed by
the development of some locally induced showers across the
southwestern quadrant of Puerto Rico during the afternoon hours each
day. Given the very dry air aloft, any activity will be short-lived
with only minor rainfall accumulations expected.

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

Stable weather conditions will remain in the long-term as a mid
to upper-level ridge holds over the islands. A polar trough will
weaken the ridge-aloft by mid- week. At the surface, a low-
pressure with its associated frontal boundary will exit near the
Carolinas around Monday. It is then forecast to move northeastward
across the Western Atlantic, inducing a weak east-southeasterly
wind flow by mid-week. While this boundary dissipates north of the
islands will induce a pre- frontal-trough over the PR/USVI
Thursday or Friday. If models are right, this could result in
favorable environmental conditions for inclement weather, the
second part of the next work-week.

&&

.AVIATION...

VFR conds expected across all local terminals throughout the
period. Some passing SHRA may result in VCSH mainly across TJSJ
and TIST through 04/12z. Sct SHRA may develop and affect SW PR
between 04/17z and 04/22z, resulting in VCSH across TJPS. No
impacts to operations expected at this time. Light and variable
winds through 04/12z, increasing to up to 15 kts from the ENE-NE
with sea breeze variations after 04/14z.

&&

.MARINE...

A northeasterly swell moving across the Atlantic is producing
hazardous coastal conditions from the northwest to the northeast
coast of Puerto Rico, including Culebra and the east-end of St
Croix. A small craft advisory is in effect across the Atlantic
Offshore waters until this afternoon due to seas up to 7 feet with
occasional seas up to 9 feet. Elsewhere, mariners can expect seas
between 4 and 6 feet with occasional seas up to 8 feet across the
exposed waters and at 5 feet or less across the protected waters.
Winds will continue around 15 knots from the NE.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 85 73 / 30 20 20 10
STT 85 73 85 73 / 30 30 20 10

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
452 AM AST Sat Dec 5 2020

.SYNOPSIS...A mid to upper-level ridge will support stable and
fair weather through midweek next week. Nevertheless, pockets of
moisture and passing showers embedded in the trades will move into
the local islands from time to time. Winds are to turn from the
east- southeast early next week, then turning light and variable
by midweek. Thereafter, somewhat enhanced shower activity is
expected with the passage of a pre-frontal trough and weakening of
the ridge aloft.


&&

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

Mainly fair weather is expected for the next several days, with the
exception of brief showers, which may cause rainfall accumulations
of less than a quarter of an inch. High pressure in the mid and
upper levels will keep a stable atmosphere, so any shower activity
that develops will likely be light to moderate. Relatively dry air
is expected today with light to moderate ENE winds prevailing, a
patch of moisture moves in on Sunday as winds become lighter and
more easterly, then drier air moves in again on Monday while winds
gradually shift to the SE, which will cause an increase in
temperatures across the northern sections of PR. There is a small
area of light rain that will affect eastern PR early this morning,
but the chance of rain will decrease later in the morning. For this
afternoon, some shower activity could develop across the SW quadrant
of PR, while fair weather is expected elsewhere. The patch of
moisture that will move in on Sunday will help in the development of
moderate showers across the eastern to central portions of PR as well
as Saint Croix USVI starting on early Sunday. Because of this brief
bump in moisture, Sunday could be the rainiest day in the short term
period, but the accumulations are still not expected to cause
significant flooding, though ponding of water on poor drainage areas
are possible. Relatively dry air makes a return on Monday and the
winds will gradually become southeasterly. With that setup, some
shower activity is possible in the afternoon across NW-PR.


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

Recent model guidance suggests that mid-to-upper ridging will hold
over the region through at least Thursday, supporting stable
weather conditions under a strong trade wind cap and the erosion
of the available moisture. By late Thursday and continuing into the
weekend, a strong mid-to-upper level trough extending southward
across the western Atlantic will displace the ridge eastward and
weaken the trade wind cap, allowing for deeper moisture with
model-estimated precipitable water reaching 1.8 inches by Friday.
At the surface, weakening frontal boundary stalling just north of
the region will maintain a light to moderate east- southeast wind
flow on Tuesday. Thereafter, an induced pre- frontal trough is
forecast to meander across the northeastern Caribbean, generating
a light and generally variable wind flow while providing
sufficient instability to support somewhat enhanced shower
activity across the region. Fair and more table weather
conditions are expected to return on Saturday.



&&

.AVIATION...VFR conds expected across all local terminals for the
next 24 hours. Brief SHRA may result in VCSH across TJSJ and TIST
through 05/12Z. Sct SHRA forecast across SW PR between 05/17Z and
05/22z, possibly resulting in VCSH at TJPS. No significant hazards
expected. Light and variable winds through 05/12z, increasing to up
to 15 kts from the ENE-NE with sea breeze variations after 05/14Z.


&&

.MARINE...Small craft operators are urged to exercise caution due
to choppy seas up to 6 feet across the offshore Atlantic and
Caribbean waters. Elsewhere, tranquil marine conditions will
continue with seas up to 5 feet and winds up to 15 knots. Marine
conditions are to improve tonight into Sunday, but a
northeasterly swell spreading across the Atlantic waters will
generate choppy seas up to 6 feet by Sunday night.

For beach goers, a high risk of rip currents remains for beaches
along the north coast of Puerto Rico, eastern-most beaches of
Culebra and Saint Croix today. The risk will drop to moderate
tonight, but a high risk is expected to return by Sunday night.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 74 84 73 / 20 10 20 30
STT 83 80 82 79 / 20 20 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
451 AM AST Sun Dec 6 2020

.SYNOPSIS...Mid to upper-level ridging will support stable and
fair weather conditions through most of the workweek.
Nevertheless, pockets of moisture and passing showers embedded in
the trades will move into the local islands from time to time.
Winds are to turn from the east-southeast early next week,
then light and variable by midweek, but backing from the
northeast thereafter. Environmental conditions will be somewhat
favorables for enhanced shower activity during the upcoming
weekend.


&&

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

A patch of deeper moisture is currently affecting the local area,
causing an area of clouds and brief showers across the USVI into
eastern PR this morning. This patch of moisture will continue today,
causing light to moderate rain across the local area, and possibly
causing some convection and persistent showers in the afternoon
across the northwestern quadrant of PR. The showers expected across
NW-PR this afternoon could cause some ponding of water on roadways
and poor drainage areas. High pressure in the mid and upper levels
will keep a stable atmosphere, that is why the shower activity that
is expected will likely be light to moderate. Winds today are
expected to become lighter and more easterly, then drier air moves
in again on Monday while winds gradually shift to the SE, which will
cause an increase in temperatures across the northern sections of
PR. The SE winds continue into Tuesday, but another patch of
moisture is expected to move in on Tuesday, causing a slight
increase in shower activity once again.


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

Recent model guidance now suggests that mid-to-upper ridging will
hold over the region later than previously suggested, supporting
stable weather conditions under a strong trade wind cap and the
erosion of the available moisture through Friday. In the
meantime, a strong mid- to- upper level cutoff low will sink
southward across the western Atlantic into the northeastern
Caribbean through the weekend. This low will displace the ridge
well to our eastward and weaken the trade wind cap, generating
favorable conditions to support deeper moisture content. So far,
model- estimated precipitable water reaching 1.6 inches by
Saturday night. At the surface, an induced pre- frontal trough
streaming westward across the northeastern Caribbean is forecast
to generate a light and generally variable wind flow through late
Wednesday night. Thereafter, winds are forecast to increase and
turn from the east- northeast influenced by a surface high moving
into the western Atlantic and a surface induced trough. If any,
environmental conditions are forecast to be somewhat favorable to
support enhanced shower activity by the end of the workweek into
the upcoming weekend.


&&

.AVIATION...Prevailing VFR conds expected across all local
terminals for the next 24 hours. Brief SHRA may result in VCSH
across TJSJ, TISX and TIST through 06/16Z. Sct SHRA forecast
across W PR between 06/17Z and 06/22z, possibly resulting in VCSH
at TJPS and TJBQ. TEMPO SHRA is possible at TJBQ. Light and
variable winds expected through 06/12z, increasing to up to 10 kts
or so from the East with sea breeze variations after 06/14Z.


&&

.MARINE...A northeasterly swell will continue to generate choppy
seas up to 6 feet across the Atlantic waters and Anegada passage
through at least Monday. Thus, small craft operators should
exercise caution across these waters. Elsewhere, tranquil marine
conditions with seas up to 5 feet and winds up to 15 knots will
prevail. There is a high risk of rip currents for a few beaches
along the north coast of Puerto Rico and eastern-most beaches of
Saint Croix. The high risk will extend to most beaches along north
coast of Puerto Rico tonight, and hold through at least late
Monday night.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 74 84 73 / 20 20 20 20
STT 83 80 82 79 / 20 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
414 AM AST Mon Dec 7 2020

.SYNOPSIS...A patch of shallow moisture will enhance shower
activity today, particularly over the northwestern quadrant of
Puerto Rico in the afternoon. Thereafter, fair and stable weather
conditions will persist through at least Thursday. Thereafter, an
increase in moisture and somewhat favorable conditions aloft will
enhance shower activity. Winds will be out of the southeast
during the next few days, turning from the east-northeast by the
end of the workweek.


&&

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

A patch of deeper moisture is currently affecting the local area,
causing mostly cloudy skies over the local islands and light brief
showers across the USVI into eastern PR this morning. This patch of
moisture will continue moving slowly west today, causing light to
moderate rain across the local area and variably to mostly cloudy
skies for most of the day. Afternoon showers are expected across NW-
PR, but the showers expected are expected to cause little
accumulation. High pressure in the mid and upper levels will keep a
stable atmosphere, that is why the shower activity that is expected
will likely be light to moderate for the next few days. Winds today
are expected to become lighter as they gradually shift SE, then
drier air moves in starting late tonight into Tuesday, and
essentially having dry air through Wednesday. The SE winds continue
into Tuesday and Wednesday, but are expected to be light.
Essentially fair weather is expected for most of the short term
period, with clouds and some rain today, drying off by Tuesday and
remaining dry on Wednesday. If shower activity occurs on Tuesday and
Wednesday, it is expected to be light.


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

Recent model guidance now suggests that ridging aloft will hold
over the region through earlier than expected, holding strong
through Thursday and gradually weakening late Thursday night into
Friday. Regardless, expect stable weather conditions under a
strong trade wind cap and limited available moisture while ridging
holds. In the meantime, a strong mid-to-upper level trough is
expected to sink southward across the western Atlantic, with
developing low over the northeastern Caribbean during the
weekend. This feature will displace the ridge well to our east,
while weakening the trade wind cap. As a result, deeper moisture
content is forecast to move over the area, with model- estimated
precipitable water peaking between 1.7 and 1.9 inches between
Friday morning and Saturday evening. At the surface, an induced
surface trough, followed surface high pressure moving into the
western Atlantic from the continental United States, will maintain
a generally east-northeast wind flow. This flow will favor
overnight and early morning passing showers moving over eastern
and northern Puerto Rico and the USVI, while afternoon convection
development, if any, will cluster along the interior and
southwestern sections of Puerto Rico. If this forecast
materializes, environmental conditions will be somewhat favorable
to support enhanced shower activity by the end of the workweek
into the upcoming weekend.


&&

.AVIATION...Prevailing VFR conds expected across all local terminals
for the next 24 hours. Brief SHRA may result in VCSH across TJSJ,
TISX and TIST through 07/16Z. Sct SHRA forecast across NW PR between
07/18Z and 08/22z, possibly resulting in VCSH at TJBQ. BKN SKY will
cause CIGS at around FL070 today, but TEMPO CIGS at FL020-030 is
possible through 07/13Z mainly at IST and TISX. Light and variable
winds expected through 07/12z, increasing to up to 10 kts or so from
the ESE to SE with sea breeze variations after 07/14Z.


&&

.MARINE...A northerly swell will continue to cause choppy seas up
to 6 feet across the Atlantic waters and Anegada passage, where
small craft operators should exercise caution through late Monday
night. Elsewhere, tranquil marine conditions with seas at 5 feet
or below will prevail. As the swell subsides, tranquil marine
conditions will return to all regional waters. There is a high
risk of rip currents for the northern and eastern beaches of
Puerto Rico and the beach of eastern St. Croix through Monday
night.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 73 85 73 / 30 30 30 20
STT 84 74 84 74 / 50 50 20 40