Caribbean - Central America Weather

[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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
401 AM AST Tue Dec 8 2020

.SYNOPSIS...Generally fair and stable weather conditions with
limited shower activity are expected during the next few days.
Winds will be out of the southeast today, gradually turning from
the east to east-northeast by the latter part of the week into the
weekend. A weakening of the trade wind cap is expected to enhance
deeper moisture content by Friday into Saturday, resulting in a
slight increase in shower activity.


&&

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

The patch of deeper moisture that has been effecting the local area
is moving away, causing the skies to clear overnight and into the
morning hours, though a few clouds are moving in from the east,
causing partly cloudy skies across the USVI. Light and brief showers
across the local waters, could briefly affect land areas, but the
accumulations are expected to be minimal. Afternoon showers are
expected across NW-PR, but the showers are expected to cause little
accumulation. High pressure persists in the mid and upper levels,
which will keep a stable atmosphere, and any shower activity that is
observed will likely be light to moderate for the next few days.
Winds today are expected to be light and from the ESE to SE. Even
drier air is expected to move in for early Wednesday. The SE winds
continue today into very early Wednesday, but winds are expected to
become easterly during the day on Wednesday into Thursday. Generally
fair weather is expected through the short term period, with brief
moments of light rain.


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

Recent model guidance suggests that a mid-to-upper level trough
extending southward into the Caribbean will stream across the
region Friday into the weekend, with its axis crossing the
forecast area late Friday into Saturday. This feature will
generate somewhat favorable conditions aloft with the weakening of
the trade wind cap. As a result, deeper moisture content is
forecast to move over the area, with model-estimated precipitable
water peaking around 1.7 by Saturday afternoon. At the surface, a
weak surface induced trough, followed by a surface high pressure
moving into the western Atlantic, will maintain a generally east
to east-northeast wind flow through early next week. Overall,
patches of low-level moisture embedded in the trade winds 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 favorable to
support enhanced shower activity on Friday and Saturday, but
significant rainfall accumulations are not anticipated.


&&

.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 08/14Z. Sct SHRA forecast across NW PR between
08/18Z and 08/22Z, possibly resulting in VCSH at TJBQ. Skies are
clearing, and mainly FEW/SCT coverage expected today, though TEMPO
BKN is possible. Light and variable winds expected through 08/12Z,
increasing to up to 10 kts or so from the SE with sea breeze
variations after 08/14Z.


&&

.MARINE...Tranquil marine conditions with seas up to 5 feet are
expected to prevail across the regional waters during the next few
days. Winds will be out of the south to southeast at 10-15 knots
through Wednesday. Then, winds are forecast to turn from the east
to east-northeast as a surface high moves into the western
Atlantic. There is a moderate risk of rip currents for beaches
along the north coast of Puerto Rico, Culebra and Saint Croix.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 74 86 73 / 10 10 10 20
STT 85 75 84 73 / 20 20 20 10

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
423 AM AST Wed Dec 9 2020

.SYNOPSIS...Mainly fair and stable weather conditions with limited
shower activity are expected during the next few days. An
increase in shower activity is forecast for Friday and Saturday
as an upper level trough streams across the region and available
moisture increases. Winds will be light and variable today,
gradually increasing and turning from the east to east- northeast
Thursday onwards. Cooler temperatures can be expected during the
weekend into early next week.


&&

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

Fair weather and light winds expected today across the local area. A
patch of moisture with some cloudiness will move in today, causing
variably to mostly cloudy skies, but the shower activity is expected
to be minimal. Ridge of high pressure in the mid and upper levels
will keep a stable atmosphere today, but a weak trough will approach
from the northwest for Thursday as it further weakens and flattens,
at the same time as a cold front stalls to our west and northwest
over Hispaniola. However, this weak trough will weaken rapidly and a
high pressure will develop in the mid levels while the upper levels
will see an increase in wind speed, but mainly with zonal flow as
the upper trough flattens. This will leave the local islands with
mainly fair weather on Thursday as well, but with less cloudiness
than today. Winds will also turn more east southeasterly on Thursday
at around 10 mph. Friday could have a bit more shower activity as
moisture increases. The overall setup in the mid and upper levels
stays the same as Thursday, but with the increase in moisture we can
expected scattered showers across the local waters, USVI, and
eastern PR in the morning hours, then moving across central and
western PR on Friday afternoon, as the patch of moisture moves west.
As of now it looks like Friday will be the rainiest day in the short
term forecast, but this rainfall is still not expected to cause
significant hazards.

.LONG TERM...Saturday to Tuesday...

Model guidance continues to suggest that a mid-to-upper level
trough extending southward into the Caribbean will stream across
the region Friday into the weekend, with its axis crossing the
forecast area on Saturday. This feature will generate somewhat
favorable conditions aloft with the weakening of the trade wind
cap and deeper moisture content over the area, with model-
estimated precipitable water peaking around 1.7 by Saturday
afternoon. Thereafter, mid-to-upper level ridging will hold
through early next week, supporting fair and stable weather
conditions under a strong trade wind inversion and the erosion of
the available moisture. At the surface, a surface high pressure
moving eastward across the western into the central Atlantic will
maintain a generally east to east-northeast wind flow through
Monday. Then, a surface induced trough to our east will generate
a more northeasterly wind flow late Monday night onwards. Cooler
temperatures can be expected with this flow.

Overall, patches of low-level moisture embedded in the trade
winds 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 western sections of Puerto Rico. If this forecast
materializes, environmental conditions will be favorable to
support enhanced shower activity on Saturday. Also, a slight
increase in shower activity can be expected once again late
Tuesday night with the proximity of the surface induced trough.
Nevertheless, significant rainfall accumulations are not
anticipated.


&&

.AVIATION...VFR conds will prevail for the next 24 hours. Some
cloudiness may cause CIGS at around FL040 today. However, SHRA
activity is expected to be minimal and not pose significant hazards.
The wind will be generally light and variable, less than 10 knots
but with a strong sea breeze influence at the terminals in PR, while
TIST and TISX will be light from the SE, becoming ENE after 09/21Z.


&&

.MARINE...Fairly tranquil marine conditions with seas up to 5
feet and winds up to 15 knots are expected during the next couple
of days. A small northerly swell may increase seas slightly
across the Atlantic waters by the end of the work week, but seas
will remain below Small Craft Advisory criteria. A moderate risk
of rip currents continues for beaches along the north coast of
Puerto Rico and Culebra, as well as for eastern beaches of Saint
Croix.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 74 86 73 / 10 10 0 20
STT 85 75 84 73 / 20 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
403 AM AST Thu Dec 10 2020

.SYNOPSIS...
A patch of shallow moisture will cross the area today, resulting
in passing showers. Conditions are expected to be a bit more
favorable for shower development for the end of the workweek.
Drier air and light winds are expected for the beginning of next
week.

&&

.SHORT TERM...Today through Saturday...
A weak frontal boundary west and northwest of the region along
with a broad high pressure ridge anchored over the northeast
Atlantic, will continue to induce a weak surface trough over the
forecast area along with fairly east-northeast wind flow. In the
mid to upper levels the ridge aloft will hold across the region
today but will erode overnight through Saturday as an amplifying
polar trough moves eastward across the west and central Atlantic.
This in turn will erode the trade wind cap inversion now in place
and destabilize the upper levels while bringing cooler
temperatures aloft Friday through Saturday as suggested by latest
model guidance.

For the rest of the morning hours, expect limited passing trade wind
showers as a patch of shallow low level moister will cross the
region. The shower activity will be mainly over the Atlantic and
offshore Caribbean waters, but a few will continue to briefly brush
the north and east coastal areas of the islands from time to time.
No significant accumulations are so far expected. During the
afternoon hours showers activity should to limited and focused
mainly over the west interior and southwest sections of PUerto Rico.
Lesser afternoon shower activity is forecast elsewhere as the ridge
aloft will continue to suppress and limit significant convection
across the area.

Later tonight through Saturday winds are forecast to gradually
become more east southeasterly between 10 to 15 mph as the Atlantic
surface ridge builds in from the northeast. In the meantime, as the
upper ridge erodes a slight increase in trade wind shower activity
is forecast as the trade wind cap inversion erodes and the
aforementioned upper trough sweeps eastward just north of the
region. This brief shift in the present weather pattern should
increase the potential for isolated to scattered afternoon
convection over parts of the west interior sections of Puerto Rico.
So far however widespread rainfall is not anticipated. For now, the
forecast calls for isolated to scattered showers across the coastal
waters, parts of the USVI, and eastern PR during the morning hours,
followed by scattered shower activity over parts of the central and
western interior sections of PR by Friday afternoon, as patches of
tradewind moisture will move across the region from time to time.
Model guidance still suggest the best chance for enhanced afternoon
showers development is on Friday, but again widespread rainfall
accumulations are not expected at this time. On Saturday the chance
of passing morning showers will remain likely with some reaching
parts of the east and southeast section of the islands. This will be
followed by afternoon convection over parts of the interior and west
sections of Puerto Rico. In addition, recent guidance suggests
cooler 500 millibar temps by Friday afternoon and on Saturday and
therefore there is a better chance for an isolated thunderstorm on
Friday afternoon over western PR and possibly on Saturday afternoon.
However, will hold off on including in the present forecast pending
the next model run to see how the expected pattern unfolds.

.LONG TERM...Sunday through Wednesday...
As a mid-level high pressure begins to build over the western
Caribbean, a generally tranquil weather pattern is expected to be
established across the forecast area. At the surface, a high
pressure system over the central Atlantic will continue to migrate
toward the west, and as a surface trough develop to the east of
the islands, an east-northeast wind flow is anticipate to prevail.
On Sunday, precipitable water values near 1.4 inches are
expected, which is near or just below normal for this time of
year. As a result, some showers are expected to work their way
into the eastern and northern half of Puerto Rico and the U.S.
Virgin Islands early in the day. Then, some activity is
anticipated in the southwestern quadrant of Puerto Rico, aided by
local effects. For now, Monday and Tuesday look to be the driest
days of the periods, hence only limited showers are expected to
affect the local area. By Wednesday, fragments of moisture
associated with the surface trough are expected to reach the local
islands, which should result in an increase in shower activity.
However, since the mid-level ridge will remain anchored west of
the area, significant rainfall accumulations are not expected. In
terms of temperatures, under an east-northeast wind flow, cooler
temperatures can be anticipated. Additionally, the trough will act
to weaken the pressure gradient across the region, resulting in a
light wind flow through late Tuesday.


&&

.AVIATION...VFR durg prd. SCT lyrs nr FL025...BKN-OVC btw FL050-
FL080. Mstly clr ABV. Isold SHRA ovr regional waters and en route
btw local islands. Mtn top obscr psbl ovr E interior sections of PR
til 10/12Z. Otherwise no sig operational wx impacts attm. SFC wnd
calm to lgt/vrb bcmg mainly E-NE btw 10-12 kts aft 10/14Z. VCSH psbl
mainly over parts of W-SW PR and at TJMZ/TJPS fm 10/17-10/22Z.


&&

.MARINE...
A northwesterly swell will create choppy seas up to 6 feet through
Friday across the Atlantic Waters and Mona Passage, hence small
craft operators are urged to exercise caution. Winds will be at 5
to 15 knots from the east northeast. There is a high rip current
risk for the northern coast of Puerto Rico.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 74 85 74 / 20 40 40 40
STT 85 74 85 75 / 20 40 30 30

&&

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
356 AM AST Fri Dec 11 2020

.SYNOPSIS...
Conditions are expected to become somewhat more favorable for
showers to affect the islands through early in the weekend.
However, significant rainfall accumulations are not expected. A
generally fair weather pattern is expected for the next workweek.
A northwesterly swell will continue to affect the Atlantic waters
through Saturday.

&&

.SHORT TERM...Today through Sunday...
Mid to upper levels ridge will gradually erode today through
Saturday as an amplifying polar trough moves eastward across the
west and central Atlantic. This in turn will break down the trade
wind inversion in place and destabilize the upper levels bringing
cooler temperatures aloft through Saturday as a jet max rounds the
base of the upper trough just north of the region. By Sunday, an
upper level ridge will build across the region from the west while
promoting subsidence and stable condition aloft once again. A
building surface high pressure across the west Atlantic and
remnants of a frontal boundary/shear line just west and north of
the area, along with the strong high pressure ridge anchored over
the northeast Atlantic, will maintain a east- northeast wind flow
across the region through the period. This will favor the
transport of occasional low level moisture fragments across the
region from time to time.

For the rest of the morning hours, expect the prevailing east
northeast low level wind flow to bring periods of passing cloud and
showers across the regional waters and parts of the islands from
time to time. The shower activity should be mostly of light to
moderate intensity and will be of short duration mainly along the
north and east coastal areas of the islands. No significant
accumulations are expected. Afternoon showers activity should be
focused over the parts of the interior and west sections of Puerto
Rico while lesser afternoon shower activity is forecast in and
around the USVI. Parts of the San Juan metro may also receive a few
brief afternoon showers but no significant accumulations are
anticipated.

Overnight through Saturday, expect the easterly trades to
gradually increase to 10 to 15 mph as the Atlantic surface ridge
builds across the region from the northeast. In the meantime, as the
upper ridge erodes expect an increase in trade wind shower activity
as the previously mentioned cap inversion erodes and the
aforementioned upper trough sweeps eastward just north of the area.
This shift in the weather pattern should increase the potential for
isolated to scattered afternoon convection over parts of the central
and west interior sections of Puerto Rico and mainly downwind of the
USVI. So far widespread rainfall is not anticipated as recent model
guidance does not suggest significant moisture transport across the
region during the entire period. The overall forecast calls for
isolated to scattered showers across the coastal waters, parts of
the USVI, and eastern PR during the morning hours, followed by
scattered shower activity over parts of the central and western
interior sections of PR as occasional patches of shallow tradewind
moisture will move across the region. The effects of cooler 500
millibar temperatures today through Saturday should support some
enhanced shower activity mainly over parts of the interior and west
sections of Puerto Rico today and on Saturday. More seasonal weather
conditions and pleasant weather condtions are forecast for Sunday as
the ridge will build aloft as well as a surface high pressure across
the west and Central Atlantic favoring an overall cool advective
weather pattern typical for this time of the year.

.LONG TERM...Monday through Thursday...
A mid level ridge will continue to build over the western Caribbean,
while a mid to upper level trough will be located to the east of the
islands. The forecast area will be under the subsidence side of the
trough, and hence in an area that will be unfavorable for shower
development. At the surface, a trough will be reflected to the
northeast of Puerto Rico and the U.S. Virgin Islands, inducing an
east-northeast wind flow. Due to the surface trough, the pressure
gradient should relax, resulting in a light flow, that should
continue through late Tuesday. Under this wind pattern, temperatures
are expected to remain mild through the islands. On Monday and
Tuesday, precipitable water values are expected to be below normal,
with values ranging between 1.0 to 1.3 inches. Both the GFS and the
ECMWF are showing that this moisture should be confined below 850
mb. Hence, any shower activity should be light, with possible
morning showers affecting eastern Puerto Rico and the U.S. Virgin
Islands in the overnight and early morning hours, followed by some
showers developing in the southwest of Puerto Rico due to local
effects.

By Wednesday and Thursday, as a surface high pressure north of the
islands migrates to the east, the wind flow will turn more from the
east, and will become moderate. At the lower levels, however, only
small patches of moisture are expected to affect the local area.
Therefore, a generally benign weather pattern is expected to
prevail through the long term forecast period.


&&

.AVIATION...
VFR conds will prevail at all TAF sites. Occasional patches of
trade wind moisture will bring SCT-BKN lyrs nr FL025...FL050 with
Isold SHRA en route btw islands and ovr regional waters. Few
passing showers will bring VCSH at TJSJ/TJNR/TISX/TIST til 11/14Z
but no significant operational wx impacts attm. SFC wnds will be
calm to LGT/VRB increasing to 10-15 knots with sea breeze
variations aft 11/14Z.


&&

.MARINE...
A northwesterly swell will continue to impact the Atlantic waters
today, creating choppy seas up to 6 feet, and small craft
operators are urged to exercise caution. Seas up to 5 feet are
expected in the Caribbean. A High Rip Current Risk is expected for
the north facing beaches of Puerto Rico and Culebra.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 76 85 75 / 40 40 40 40
STT 85 75 85 74 / 40 50 40 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
411 AM AST Sat Dec 12 2020

.SYNOPSIS...
A surface high pressure ridge will build and spread eastwards
across the west and central Atlantic through the weekend into
early next week. This will maintain an east northeast wind flow
across the forecast area. An amplifying mid- upper level trough
will continue to sweep across the region today reaching the
northern Leeward Islands by early Sunday. This will support the
development of scattered shower activity over the regional waters
and parts of the islands today into early Sunday. Thereafter, a
building upper level ridge will lift northward across the region
from the west and central Caribbean into early next week. This
will lead to improving weather conditions and a more seasonable
weather pattern as high pressure will be the dominant weather
feature promoting a drier and stable airmass.

&&

.SHORT TERM...Saturday through Monday...

A mid to upper level trough is amplifying over the area, resulting
in an increase in instability across Puerto Rico and the U.S. Virgin
islands. This has also resulted in a weakening of the trade cap
inversion, as is evident from the 12/00Z TJSJ sounding. At the
surface, a high pressure located over the western Atlantic is
maintaining a moderate wind flow coming out of the east. Satellite-
derived Total Precipitable Water shows an area of increased moisture
being pulled into the islands, resulting in scattered showers across
the U.S. Virgin Islands and eastern Puerto Rico. In the afternoon,
with enough moisture and with better conditions aloft, showers are
expected to develop in the interior and western Puerto Rico, as well
as some streaming over portions of eastern Puerto Rico and the San
Juan metro area. Moderate accumulation is expected, which could
result in ponding of water on roadways and low-lying areas, or minor
urban and small stream flooding, especially over southwestern Puerto
Rico.

However, the unsettled weather conditions are not expected to last
long, as the mid to upper level trough is expected to moved into the
Lesser Antilles by late Saturday into Sunday, leaving the forecast
area under its subsidence side. Additionally, a mid level ridge will
begin to build over the western Caribbean, which will help to
maintain most of the moisture confined to the lower levels of the
atmosphere. This will gradually result in drier conditions, but
still, some passing showers are expected early on the day on Sunday,
followed by afternoon showers over the interior and western Puerto
Rico. Also by Sunday, the winds will shift again from the east
northeast as a surface trough develops to the northeast of the
islands. This will slacken the pressure gradient, resulting in a
lighter wind flow through early in the workweek.

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

A mid level ridge will build over the western Caribbean, while a
mid to upper level trough will be located to the east of the islands.
The forecast area will be on the subsidence side of the trough,
and hence in an area that will be unfavorable for significant shower
development. At the surface, a weak trough will linger northeast
of the region while high pressure will build north of the area to
induce an east- northeast wind flow. With this expected weather
pattern, the local pressure gradient should relax, resulting in a
light wind flow which will continue through mid week. Under this
wind flow pattern, seasonal temperatures can be expected across
the region with limited convection over most of the islands.
Through at least the middle of next week, precipitable water
values are expected to be below normal, with values ranging
between 1.0 to 1.4 inches. Both the GFS and the ECMWF suggest
limited moisture content confined below 850 millibars.
Consequently, any shower activity should be light, with only brief
showers affecting parts of north and eastern coastal areas of
Puerto Rico and the U.S. Virgin Islands overnight and in the early
morning hours, followed by limited isolated to scattered
afternoon shower development mainly in southwest of Puerto Rico
due to local effects.

By Wednesday and through the latter part of the period, a surface
high pressure north of the islands is forecast to migrate eastward
across the Atlantic. This will gradually increase the easterly
wind flow as the local pressure gradient tightens across the
forecast area. As a result, a slight increase in trade wind moisture
transport can be expected across the region with better potential
for early morning trade wind showers and locally and diurnally
induced afternoon showers in isolated areas, mainly on the west-
end of the islands and just downwind. No significant weather
features are so far forecast for the period with overall seasonal
weather conditions and temperature expected for the area.

&&

.AVIATION...Mainly VFR conditions are expected across the terminals
through the forecast period. VCSH could result in brief MVFR
conditions due to low ceilings and reduced visibility across TJSJ
before 12/22Z. Passing showers may affect the Leeward terminals
and TIST/TISX as well, but no major impacts are anticipated. Winds
will be out of the east at 10 to 15 knots.

&&

.MARINE...Recent data from the surrounding buoys suggests a gradual
fading of the northerly swell along with subsiding seas. Mariners
can however expect seas between 4 and 6 feet over the offshore
waters and local passages and seas between 3 and 5 feet elsewhere.
A light to moderate wind chop will continue across portions of
the local waters and passages and therefore small craft operators
should exercise caution.


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
329 AM AST Sun Dec 13 2020

.SYNOPSIS...
Mid to upper level trough will continue to shift eastward across
the northern leeward islands today as a high pressure ridge will
build across the region from the west. This will place the area
on the subsident and more stable side of the upper trough. In the
low levels an induced trough northeast of the region and broad area
of high pressure across the west and central Atlantic will maintain
a moderate east northeast wind flow across the forecast area through
the early part of the work week. The overall pattern will combine
with land and sea breeze convergence to maintain periods of light
to moderate showers each day during the morning and afternoon hours.

&&

.SHORT TERM...Sunday through Tuesday...
Mid level ridge continues to build west of the islands, and as a
result, instability aloft is decreasing. At the lower levels,
however, Total Precipitable Water, derived from satellite imagery,
indicates an area of enhanced moisture lingering to the north of the
region. This has been resulting in passing showers affecting eastern
and northern sections of Puerto Rico, as well as the U.S. Virgin
Islands. Just like yesterday, showers are expected to develop this
afternoon over the interior and western Puerto Rico, but without
upper level support, this activity is only expected to result in
ponding of water on roadways and low-lying areas.

For tomorrow, as an induced surface trough developed to the
northeast of the Lesser Antilles, a lighter east-northeast wind flow
is expected to be established. Additionally, the model guidance
indicates that the mid levels will continue to dry off. Moisture at
the lowest levels will decrease as well, but some showers may still
be advected over the local area through the day. Then, by Tuesday,
as the mid-level ridge continues to hold, the trade wind cap is
expected to strengthen and moisture is expected to decrease as well.
In general, the environment will become less conductive for
significant rainfall to develop across the islands through early in
the week. In terms of temperatures, due to a northeasterly wind
flow, a drier air mass and clear skies at night and in the morning,
temperatures are expected to be cool to mild, especially over the
mountains.

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

A mid to upper level ridge will build and spread across the region
from the western Caribbean, promoting subsident and stable conditions
aloft though the period. In the low levels the induced trough northeast
of the region will continue to weaken by Thursday as a high pressure
ridge will build north and east of the region. This will result in
an east-northeast wind flow, and the further strengthening of the
trade wind inversion during the latter part of the period. Under this
wind flow and expected weather pattern, seasonal temperatures can
be expected across the islands with limited convective development
expected each day.

Recent model guidance continued to suggest below normal layered
precipitable water values to less than an inch Wednesday into
Thursday then a slight increase in mainly low level moisture as
PWAT values increase once again to near normal during the latter
part of the period. Therefore, for the early part of the period,
any shower activity should be mostly light to moderate, with only
brief showers affecting mainly the north and east coastal areas of
the islands overnight, followed by locally and diurnally induced
showers of short duration mainly over the west interior and
southwest sections of Puerto Rico. Some brief showers will remain
possible each day over parts of the west-end of the U.S. Virgin
Islands or just downwind, but no significant widespread rainfall
accumulations are forecast for the period.

By the latter part of the period, surface high pressure across the
west Atlantic will migrate further eastward and spread across the
across the Atlantic. This will gradually increase the easterly
winds as the local pressure gradient tightens across the forecast
area. As a result, increasing tradewind moisture transport can be
expected across the region with better potential for early morning
trade wind showers and some enhanced locally and diurnally induced
afternoon showers in isolated areas. The daytime shower activity
however should be focused mainly on the west sections of the islands
and just downwind over the coastal waters steered by moderate
east-northeast tradewinds. No significant weather features are
however forecast for the period ,with an overall seasonal weather
pattern and near normal temperatures forecast for the area.

&&

.AVIATION...VFR conditions are expected to prevail across all terminals through
the forecast period. Passing showers may move near TJSJ, but significant
operational impacts are not anticipated. Winds will be out of the east
to east northeast at around 10 knots.

&&

.MARINE...Seas up to 6 feet across the offshore Atlantic, and mainly
between 2 to 5 feet elsewhere. Winds generally 10 to 15 knots from
the east northeast. there is a low to moderate risk of rip
currents across the local beaches.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 85 76 / 30 40 30 30
STT 85 75 84 73 / 20 20 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
525 AM AST Mon Dec 14 2020

.SYNOPSIS...

Overnight and early morning passing showers are forecast to
affect portions of eastern and northern Puerto Rico, as well as
the U.S. Virgin Islands from time to time. Afternoon convection
will be limited as a surface high pressure combined with below
normal moisture dominates the area. An increase in low level
moisture will increase the potential for showers by the upcoming
weekend. An increase in seas across the Atlantic waters will
result in hazardous marine conditions through late tonight.

&&

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

High pressure at the surface dominates most the of Atlantic ocean. A
weak low induced by an upper level trough is 500 miles northeast of
saint Martin. The surface low will drift west today and Tuesday and
open up as a trough north of the Leeward islands on Wednesday. The
low is accompanied by precipitable water near seasonal normals with
a band that extends south and then over Puerto Rico and the U.S.
Virgin Islands. Bands of moisture move through the area, but a dry
slot will pass through Tuesday afternoon and evening as the low
level low pressure moves closer. The proximity of the low pressure
to our northeast will mean continued flow from the northeast. This
will bring a good chance of showers this afternoon to southwestern
and interior Puerto Rico this afternoon. Showers will re-develop
over that area on Tuesday,but moisture will be somewhat more limited
and rain is not expected to be as heavy. Accumulations of over one
inch are possible this afternoon in southwest Puerto Rico where
ponding on roadways and low-lying areas is expected. Showers will be
a little heavier on Wednesday as moisture returns. Overnight and
early morning showers are likely each day along the windward
coasts.

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

Seasonal temperatures along with limited convective development
can be expected across the islands each day. Conditions aloft will
be stable as a mid to upper level ridge builds over the region.
This will be accompanied by favorable low level conditions due to
a high pressure ridge that will build north and east of the
forecast area. However, patches of moisture embedded with the
east-northeast trade wind flow will reach our area from time to
time. Expect this shower activity to result in light rainfall
accumulations affecting mostly parts of northern and eastern
coastal areas of the islands early in the mornings. Afternoon
convection will follow, but focusing over parts of interior and
western PR. Showers down wind from the US Virgin Islands and El
Yunque cannot be ruled out. However, this activity is not expected
to leave significant rainfall accumulation. Thus, at most,
ponding of water may be observed with the heaviest and most
persistent rains. By the end of the forecast period, moisture
content will increase over the region as the pressure gradient
tightens due to the migration of the surface high pressure further
west of the forecast area. This in turn will promote pleasant
temperatures across the islands.

&&

.AVIATION...

VFR conditions are expected to prevail across all terminals through
the forecast period, but ocnl MVFR due to CIGs and SHRA along the N
coast of PR are expected til 14/15Z. NE sfc winds at at 5 to 10
knots with land breezes will become 10 to 15 kt with sea breezes.
Max winds NW-N 35-50 kts btwn FL260-450 strongest at FL440. Upper lvl
winds will be diminishing durg the day.


&&

.MARINE...

The local winds and the northerly swell will aid in generating
hazardous seas mainly across the offshore Atlantic waters through
at least late tonight. Elsewhere, tranquil marine conditions with
seas of 5 feet or less will prevail. Winds will be out of the
east- northeast to east at 10 to 15 knots. In Puerto Rico, there
is a moderate risk of rip currents for beaches along the north
coast of Puerto Rico, east coast of Vieques and most beaches of
Culebra. In the US Virgin Islands, there is a moderate risk of rip
currents for beaches along the northwest coast of Saint Thomas
and east coast of Saint Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 75 84 75 / 50 60 50 40
STT 85 74 85 74 / 30 40 40 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
511 AM AST Tue Dec 15 2020

.SYNOPSIS...

Moisture confined at the low levels, associated with a weak
surface low, will slightly enhance showers tonight through late
Wednesday night. A more typical seasonal pattern with the passage
of intermittent patches of moisture embedded in the trade winds is
expected during the rest of the week. Seas are subsiding, thus
choppy marine conditions are expected over the regional waters. A
high risk of rip currents is expected through at least Wednesday
afternoon.

&&

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

High pressure at the surface dominates most the of eastern Atlantic
ocean. A weak low induced by an upper level trough is almost 600
miles northeast of San Juan. The surface low will open up into a
trough and drift southwest today and cross over the U.S. Virgin
Islands and Puerto Rico Wednesday night. A dry slot is moving
through the area today, but moisture will increase to over 1.5
inches of columnar water by early Wednesday morning. The proximity
of the low pressure to our northeast will mean continued flow from
the northeast, but when the trough passes this flow will become east
to east southeast.

The pattern described will bring a chance of showers this afternoon
to southwestern and interior Puerto Rico. Showers will be a little
heavier tonight on the north coast as moisture returns and then on
Wednesday in southwest and interior Puerto Rico. Models are also
trending wetter in the latest run. On Thursday showers will favor
the eastern slopes of the island in the morning and the northwestern
quadrant of Puerto Rico in the afternoon.

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

At the upper levels, the mid to upper level ridge spreads over
the region. At the low levels, surface high pressure across the
west Atlantic will migrate further eastward and spread across the
across the Atlantic. This will gradually increase the easterly
winds as the local pressure gradient tightens across the forecast
area. Also, precipitable water values values increase once again
to near normal during the the end of the workweek. Then, a slight
increase in mainly low level moisture as can be expected across
the region. Therefore, there will be a better potential for early
morning trade wind showers and some enhanced locally and diurnally
induced afternoon showers in isolated areas during the weekend
into the first part of the upcoming workweek. Seasonal
temperatures are expected over the islands during the forecast
period. Therefore, an overall seasonal weather pattern with
limited convection development can be expected each day across the
local islands.

&&

.AVIATION...

VFR conds are expected to prevail across all terminals thru the fcst
pd, a few SHRA are expected alg the N coast of PR til 14/15Z. SHRA
to dvlp ovr SW PR aft 15/17Z, but tops genly blo FL260. NE sfc winds
at 5 to 10 knots will become 10 to 15 kt with sea breezes aft
15/15Z. Max winds N 35-40 kts btwn FL255-275 and NNW-N 35-45 btwn
FL425-455.

&&

.MARINE...

Seas have dropped below Small Craft Advisory criteria, so the
advisory has been cancelled for the offshore Atlantic waters.
However, small craft operators are urged to exercise caution due
to choppy seas up to 6 feet. Elsewhere, seas are generally
between 3 and 6 feet with a winds up to 15 knots. There is a high
risk of rip currents across the beaches of northern Puerto Rico
today.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 75 84 74 / 40 60 50 30
STT 85 74 86 73 / 30 30 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
525 AM AST Wed Dec 16 2020

.SYNOPSIS...
A northeasterly wind flow due to the combination of
a surface high and an induced trough will bring patches of low
level moisture from time-to-time over the region. Winds will shift
to the east to east-southeast on Thursday. Brief trade wind
showers will affect the local area leaving no significant
accumulations for the rest of the forecast period. Choppy seas
will continue through tonight.


&&

.SHORT TERM...Today through Friday...
The mid and upper level troughs oriented northeast/southwest over
the western tropical Atlantic will continue with little movement and
gradually weaken during the next several days. The trough at the
surface however appears to be released as these are weakened and
will drift west across the area tonight. A band of moisture will
move ahead of the trough this afternoon and this evening. The
apex/axis of the trough, however, will contain a dry slot at 850 mb
and the moisture that follows the axis when it passes through on
Thursday will be less than the moisture that precedes the trough.
Also the patchy moisture that continues in the east southeast flow
behind the trough will fade during the period leading to less
coverage and weaker showers through at least Friday evening.

Temperatures will remain near normal with some variations depending
on whether the flow is moving generally onshore or offshore, where
our local waters will be the buffering factor.


.LONG TERM...Saturday through Wednesday...
An increase the easterly winds is expected as the local pressure
gradient tightens across the forecast area. This will result in
pleasant temperatures across the islands. Precipitable water
values are forecast to be near normal. Current model guidance
suggest a slight increase in moisture content by the weekend.
Thus, local and diurnal effects combined with the available
moisture could produce a few showers during the afternoons.
Showers that do develop will be short-lived and produce light
rainfall amounts. The activity will focus over the interior and
western sections of Puerto Rico. This season weather pattern will
hold through the rest forecast period.


&&

.AVIATION...
VFR conds are expected to prevail across all terminals thru the
fcst pd, sct SHRA are expected alg the N coast of PR and adjacent
waters til 14/15Z. SHRA to dvlp ovr SW PR aft 15/17Z, but tops
genly blo FL260. NE sfc winds at 5 to 10 knots will become 10 to
15 kt with sea breezes aft 15/15Z. Max winds N 40-50 kts btwn
FL480-510.


&&

.MARINE...
Choppy marine conditions will continue for the next couple for
days, mainly across the offshore Atlantic waters and Anegada
passage. Thus, small craft should exercise caution across the
aforementioned waters through at least tonight as seas will be up
to 6 feet. The combination of a surface high pressure and an
induced trough at the surface will maintain northeasterly winds
of 10 to 15 knots during the next several days. There is a high
risk of rip currents for the beaches along the north coast of
Puerto Rico through this afternoon.The risk will continue through
tonight for the beaches along the northwestern to north central
coasts of Puerto Rico.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 74 86 74 / 50 30 30 50
STT 84 73 84 75 / 30 20 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
448 AM AST Thu Dec 17 2020

.SYNOPSIS...A weak trough will exit the area today with moisture
immediately following. Scattered showers will continue through
next week, but winds will become breezy by early next week as
east northeast trade winds increase and showers will favor
eastern Puerto Rico more.

&&

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

The surface trough induced by an upper level low will continue to
promote showers through the early morning hours. This activity is
not expected to lead any significant rainfall accumulations. The
edge of the weakening trough will continue to dissipate and move
away from our area and a surface high pressure takes over the
weather conditions across the forecast area. Lingering moisture
confined in the low levels will combine with local and diurnal
effects to cause shower activity, mainly in the afternoon hours
across most of the interior and western sections of Puerto Rico.
Some streamer-like shower activity downwind from El Yunque cannot
be ruled out and therefore the Greater San Juan and Bayamon metro
area could also observe scattered showers during the afternoon
hours. Although rainfall activity is expected to be light to
moderate, showers could lead to ponding of water on low-lying
areas. The high pressure will hold over our area and will promote
a general easterly wind flow. Thus, shallow moisture embedded in
the trade winds will reach the islands from time-to-time
resulting in intermittent shower activity for the rest of the
short term forecast period.

.LONG TERM...Sunday through Wednesday...
High pressure continues west of the area at upper levels with flow
exclusively west northwest to northwest during the period. At mid
levels, high pressure shifts slightly south to remain mainly west
of the area. At lower levels, higher pressure continues across
the entire Atlantic between 20 and 30 degrees north with migrating
high pressures, some of which become strong, passing north of
this. This pattern will maintain moderate to fresh east northeast
trade wind flow that will continue through the period. These
winds carry areas of moisture across the area that will produce
showers on a daily basis. Precipitable water values vary from 1.3
to 1.6 or 1.7 inches on an almost daily basis through the period.
Because low level winds intensify early next week, showers will
favor eastern Puerto Rico more than western Puerto Rico, but
amounts will be modest and showers will be fairly fast moving.
Also significant moisture will remain below 10 kft, allowing the
strongest influences to be orographic.


&&

.AVIATION...
Mostly VFR conds expected across the local terminals drg
the 24 hr pd. VCSH expected thru 17/14Z for TIST/TISX due to the
passage of moisture associated with an induced trough at the
surface. Brief -SHRA is psbl at the terminals, but this activity
is not expected to cause major operational issues. Winds will be
lgt and vrbl or easterly till 17/14z. Winds are forecast to be
more E to ESE aft 17/14Z at 12kt or less.

&&

.MARINE...Winds and seas somewhat choppy with northerly swell
through Sunday. A stronger northerly swell will arrive on Monday
creating hazardous seas in exposed waters. East winds across the
area will also increase with some areas reaching 20 knots or more
at times. Rip currents will become much more prevalent then also.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 74 86 75 / 30 30 40 40
STT 85 75 86 75 / 20 30 30 30

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
438 AM AST Sat Dec 19 2020

.SYNOPSIS...A mid-level high pressure will continue to dominate the local
weather pattern and it is expected to persist through the
weekend. Trade wind showers will affect the local area from time
to time. A northerly swell will result in hazardous marine
conditions from late Sunday into the workweek. In the mean time, a moderate
rip current risk continues for the north and eastern coast of Puerto
Rico and the U.S. Virgin islands.


&&

.SHORT TERM...

Trade wind showers across the regional waters moved from time to
time over portions of northern and eastern Puerto Rico, as well as
across the U.S. Virgin Islands. Up to a quarter of an inch was
observed with this activity over the north-central municipalities of
PR. Minimum temperatures ranged in general from the mid 60s across
the higher elevations to the high 70s across coastal areas.

A mid-level ridge extending over the local area from the western
Caribbean, will promote an east to northeast trade wind cap over the
region through the short term period. A cold front will remain far
north over the Atlantic waters and a surface high pressure is
expected to move quickly between Sunday and Monday over the western
Atlantic. This will bring a more easterly wind flow by the end of
the forecast period. While conditions are not favorable for
thunderstorm development, enough moisture content at lower levels
will be sufficient to induced diurnal shower activity over portions
of the interior and west/southwest PR each afternoon. Across the
USVI, the breezy trades will move quickly offshore any streamer type
of shower activity that develops around midday each day. Scattered
shower activity is expected during the overnight and early morning
hours across the USVI and the northern/eastern sections of PR each
day, as showers over the Atlantic and Caribbean waters are carried
by the ENE trades.

.LONG TERM...

Model guidance continues to show weather predominantly dominated by
the mid level ridge spreading over our region from the western
Caribbean during the long term forecast period. This will promote
relatively stable conditions aloft. Additionally, a frontal
boundary over western Atlantic will move eastward and stall north
of our region by Thursday and quickly dissipate afterwards. This
could momentarily bring favorable conditions aloft with 500 mb
temperatures cooling to -8 degrees celsius. However, this will be
short in duration but possibly increase areal coverage of shower
activity with the presence of low level moisture for the latter
part of the period. At the surface, a high pressure over western
Atlantic will continue moving eastward over central Atlantic
maintaining a gentle to moderate east northeast trade wind flow
over the forecast area. Shallow areas of moisture embedded in this
northeasterly wind flow will reach the islands from time to time.
This will produce shower activity on a daily basis.

Precipitable water values will vary from 0.75 inches on Tuesday
morning sharply increasing up to 1.5 inches during the afternoon
hours, with varying values between 1.0 to 1.4 inches onwards until
the end of the workweek. Overall, isolated to scattered showers are
expected to stream across the local waters into coastal areas of
eastern and northern Puerto Rico and U.S. Virgin Islands during
overnight and morning hours, while scattered shower development
due to locally induced effects can be expected along the interior
and western sections of Puerto Rico in the afternoon hours of
each day. This weather pattern is expected to hold through the end
of the workweek.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, trade wind shra may
cause brief MVFR cigs across TJSJ and the USVI terminals through the
morning hours. SHRA is expected to develop btw 16z-22z over
southwest PR, this may cause tempo MVFR cigs at TJPS. Low level
winds ENE at 10-15 kts.


&&

.MARINE...Seas at 5 feet or less are expected to prevail through
today. A northerly swell is expected to arrive late Sunday into
Monday, resulting in hazardous marine conditions, with seas
reaching Small Craft Advisory criteria. A moderate rip current
risk continues for the north and eastern coast of Puerto Rico,
Vieques, Culebra and all beaches in the U.S. Virgin Islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 74 86 74 / 40 30 30 30
STT 86 78 85 78 / 40 30 30 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
438 AM AST Sun Dec 20 2020

.SYNOPSIS...Trade wind showers will continue to affect the local
islands through midweek with light to moderate amounts of rainfall
expected. Marine conditions are expected to deteriorate by late
tonight into the workweek, resulting in hazardous seas and coastal
conditions across the islands. In the mean time, a moderate rip
current risk continues today for the north and eastern coasts of
Puerto Rico and the U.S. Virgin islands.

&&

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

East to northeast trade wind showers across the regional waters
moved at times over portions of the U.S. Virgin Islands and across
the eastern and northern coastal areas of Puerto Rico through the
overnight hours. Rainfall amounts were not as significant as
yesterday and mostly clear skies prevailed across the rest of the
area. Minimum temperatures were from the low to mid 60s across the
higher elevations to the mid 70s across coastal areas in general.

A mid-level ridge extending from the western Caribbean will
gradually weaken through the short term period as a polar trough
exits the Eastern Seaboard of the U.S. by Monday. This will relax
the trade wind cap, and allow for weak easterly perturbations to
reach the region by late tonight into Monday morning and another one
on Tuesday morning. This will increase the areal coverage of
diurnally induced afternoon showers over sections of the eastern
interior and western Puerto Rico each day, and across the U.S.
Virgin Islands. A surface high pressure over the western Atlantic
will move into the central Atlantic later today, promoting moderate
easterly trades. However, steering winds are expected to continue
from the east to northeast and diurnally induced afternoon showers
are expected over portions of the Cordillera Central and
southwestern PR. Across the USVI, sunny to partly cloudy skies are
expected overall today, with the occasional trade wind shower moving
at times and streamer type of activity developing in the afternoon.

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

On Wednesday, a surface high pressure moving eastward over north
central Atlantic and a mid level ridge spread out throughout the
Caribbean will continue maintaining a gentle to moderate east
northeast trade wind flow over the forecast area. Low precipitable
water values of less than an inch will promote relatively fair
weather conditions. However, this weather pattern will change as a
series of frontal and prefrontal features will move near our region
for the rest of the forecast period. First, the residual of a
frontal boundary over east central Atlantic will combine with
another frontal boundary moving eastward and stall north of the
forecast area between late Wednesday through Friday. As this
combining features converge to our north, patches of low level
moisture (associated with the dissipating frontal boundaries)
embedded in the trade wind flow will increase the precipitable water
with varying values between 1.4 to 1.6 inches during this period.
Thus, expect locally induced shower development for Wednesday
afternoon over interior and western portions of Puerto Rico and
scattered showers over the local waters during overnight hours.

On Thursday, a mid level short wave trough will build just north of
the region related to the stalled fronts. Cold air advection
associated with the trough will cool 500 mb temperatures to -9
degrees celsius bringing favorable conditions aloft. The weakening
of the mid-level ridge and troughiness north of the area will
promote convection and an increase in areal coverage of shower
development for Puerto Rico and U.S. Virgin Islands. Minor urban and
small stream flooding as well as ponding of waters on roadways and
in poor drainage areas cannot be ruled out in isolated areas with
persistent rainfalls through Friday. Afterwards, moisture will
decrease through late Saturday. However, model guidance suggests the
buildup of a prefrontal trough from another frontal boundary moving
eastward from western Atlantic. There is large uncertainty
regarding the timing and location of this feature. Nevertheless,
for Saturday expect periods of passing showers to the eastern
coastal and mainly parts of the east coastal sections of the
islands during the morning hours and streamer-like showers in the
afternoon hours.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, quick passing showers
may cause brief MVFR cigs at times at TJSJ/TIST/TISX. Diurnally
induced afternoon SHRA is expected to develop mainly in the vcty of
TJPS/TJBQ btw 16z-22z. Winds E-ENE at 10-15 kts.

&&

.MARINE...Seas 1-5 feet near shore and up to 6 feet over the
offshore waters are expected today with winds generally from the
east up to 20 knots. Seas are forecast to gradually increase
today, as a long period northeasterly swell is forecast to invade
the local waters by late tonight into early Monday. This will make
marine conditions to become hazardous through much of the
workweek. A moderate rip current risk continues today for the
north and eastern coasts of Puerto Rico, Vieques, Culebra and most
beaches in the U.S. Virgin Islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 74 84 74 / 20 50 50 50
STT 85 74 84 75 / 30 50 50 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
453 AM AST Mon Dec 21 2020

.SYNOPSIS...Patches of moisture are expected to move into the
islands through midweek, resulting in passing showers. A long-
dominant period northeasterly swell will continue to invade the
local waters today causing hazardous seas through much of the
workweek. Conditions are expected to become more favorable for
rainfall activity by the end of workweek.


&&

SHORT TERM...Today through Wednesday...

Scattered showers in an easterly 20-25 kt wind flow were noted
mainly across the Atlantic waters through the overnight hours. A few
of these showers moved over coastal areas of northern and eastern
Puerto Rico and across the U.S. Virgin Islands, leaving mostly minor
rainfall amounts. Winds over land areas were between 5-10 mph from
the east. Minimum temperatures ranged from the mid 60s across the
higher elevations to the mid 70s across coastal areas.

The mid-level ridge over the Caribbean basin will continue to weaken
during the next few days as a polar trough exits the Eastern
Seaboard of the U.S. today and press against it. However, dry air
will continue at the mid-levels and latest guidance suggest a slight
warming of the 500 mb temps from -7C today to -5C degrees by
Wednesday. Therefore, thunderstorms are not expected at this moment
during the short term period. At lower levels, weak trade wind
perturbations will reach the local area tonight and once again on
Wednesday. This will increase the chances of rainfall across the
USVI and eastern sections of PR during the overnight and early
morning hours, and as well over western PR each afternoon. Also,
streamers are expected to develop off the USVI and from el Yunque
area into San Juan and vicinity. Having said that, precipitable
water content is forecast to remain at normal to below normal values.

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

Model guidance continues to show a wetter pattern for the long term
period. High pressure at the surface will continue dominating most
of the north central Atlantic Ocean promoting an easterly trade wind
flow across the region on Thursday. With moisture embedded in this
easterly wind flow confined within 600 mb reaching the islands,
afternoon scattered shower development can be expected along the
interior and western sections of Puerto Rico and over the local
waters during overnight hours with some reaching the northern
sections of Puerto Rico and the U.S. Virgin Islands.

Afterwards winds will become from east southeast associated with
a prefrontal trough produced by a strong polar trough that will
exit the Eastern Seaboard by Friday. With precipitable water
values of 1.6 inches and 500 mb temperatures cooling to -8 degrees
celsius, Friday is forecast to be the most favorable for
widespread shower activity over the forecast area. In the
afternoon, local effects and the available moisture will combine
to result in convective showers over the western half of Puerto
Rico especially over the northwestern portion of the island.
Isolated to scattered showers are expected elsewhere. Light to
moderate rainfall accumulations are expected over the local area
with localized higher accumulations over western Puerto Rico.
Expect ponding of water on roadways and in low-lying areas with
this activity. A decrease of moisture is forecast over the
weekend. However, shallow moisture embedded in the trade winds
will reach the forecast area from time-to-time resulting in
isolated shower activity over eastern Puerto Rico, Culebra and
Vieques as well in and around the U. S. Virgin Islands during the
morning hours with local effects dominating the interior and
western portions of Puerto Rico in the afternoon hours of each
day.


&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, quick passing showers
may cause brief MVFR cigs at times at TJSJ/TIST/TISX through the
forecast period. Diurnally induced afternoon SHRA over western PR may
cause MVFR conds at TJBQ. Winds from the east at 12-17 kts, with
sea breeze variations aft 14z.


&&

.MARINE...Mariners can expect seas up to 7 feet across the
Atlantic Offshore waters and up to 6 feet elsewhere. A northeast
swell will continue to invade the local Atlantic waters today
increasing seas. A Small Craft Advisory is in effect from tonight
through Thursday across the Atlantic Offshore waters. Winds will
generally continue from the east at 10 to 20 knots. A high rip
current risk is in effect for the north and eastern coasts of
Puerto Rico.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 73 86 74 / 50 40 40 50
STT 84 75 84 74 / 50 50 10 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
447 AM AST Tue Dec 22 2020

.SYNOPSIS...Fair weather conditions are expected today and on
Wednesday. A long-dominant period northeasterly swell will
continue to invade the local waters today causing hazardous seas
through the rest of the workweek. Conditions are expected to
become more favorable for rainfall activity by the end of
workweek.


&&

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

Fair weather conditions are expected today and on Wednesday as
precipitable water content(PWAT) is forecast to range from 1.0-1.3
inches, well below climatology. This is due to a persistent mid-
level ridge over the central Caribbean and drier air intrusion
aloft. Meanwhile, weak easterly perturbations induced by an upper
level trough across the Leeward Islands will continue to provide at
times pulses of shallow moisture and showers embedded within the
trade winds. However, no significant rainfall amounts are expected
through this period. By Thursday, the mid-level ridge is forecast to
gradually erode as an upper level trough moves north of the islands.
This will weaken the trade wind cap and allow for low-level moisture
to increase across the area. PWAT content is forecast to range
between 1.5-1.8 inches and 500 mb temperatures are expected to
drop to -8 degrees C. Therefore, rain showers will increase
through the day and as well as the potential for some urban and
small stream flooding being observed in diurnal activity over
mainland PR.

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

Weather conditions are expected to slowly improve on Friday into the
weekend as a mid level short wave trough to the northeast of the
Leeward Islands moves eastward and a mid to upper level ridge builds
and settles over the forecast area. However, cold air advection in
the mid levels will maintain favorable conditions aloft for
development as 500 mb temperatures will fluctuate between -7 to -8
degrees celsius on Friday. Advective moisture from the mid level
trough to the northeast and plumes of moisture embedded in the
easterly trades will keep precipitable water values oscillating
between 1.3 to 1.5 inches on Friday before decreasing sharply to
around an inch on Saturday. Therefore, expect isolated to
scattered showers to reach the U.S. Virgin Islands and northern
and eastern coast of Puerto Rico in the morning hours on Friday
with scattered to numerous showers over western half of Puerto
Rico in the afternoon. Streamer-like showers from El Yunque and
the local islands cannot be ruled out. Ponding of waters on
roadways and in poor drainage areas will remain possible in
isolated areas with the heaviest rains.

Lingering moisture could produce isolated shower activity to stream
across the local waters into coastal areas of eastern and northern
Puerto Rico, as well as the US Virgin Islands during overnight hours
through Saturday morning before a pocket of dry air decreases shower
activity over the region in the afternoon. However, locally induced
effects may produce some light streamers and shallow rainfall to
develop over interior and southwestern portions of Puerto Rico
Saturday afternoon. For the remainder of the long term period
weather conditions will become wetter once again as a mid level
short wave trough builds to the west of Puerto Rico and an induced
surface low settles north over the area. Through this period, expect
an uptick of shower activity on Sunday through Monday as the mid
level trough moves eastward through the Caribbean. With this feature
winds will shift from the east to more southeasterly, pulling deeper
moisture over the forecast area and increasing areal coverage of
shower development.


&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. Trade wind showers and diurnally
induced afternoon showers will result in mainly VCSH at times across
the area terminals. Low level winds from the east at 15-25 kts.


&&

.MARINE... A long period northeasterly swell will continue to
invade the local waters, creating hazardous seas. Small craft
advisories are in effect for the offshore Atlantic waters and the
Anegada Passage, and the advisories will spread toward must of the
local waters today and tomorrow. This swell event is also causing
hazardous coastal conditions across the north and west-facing
beaches of Puerto Rico and most of the beaches in the U.S. Virgin
Islands, Vieques and Culebra.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 74 83 75 / 40 40 30 30
STT 85 74 85 74 / 10 40 40 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
454 AM AST Wed Dec 23 2020

.SYNOPSIS...Fair weather conditions are expected across the
islands through most of the day. However, showers will increase
on Thursday due to the effects of an induced surface trough. Seas
will continue increasing until Friday morning causing hazardous
seas through the rest of the workweek. High rip current risks,
high surf advisories and small craft advisories are in effect.


&&

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

Fair weather conditions are expected across the islands through
most of the day. However, a weak induced surface trough to our
northeast will promote northeast trades and pulses of shallow
moisture to aid in the development of trade wind showers through
the morning hours across portions of the USVI, and northern and
eastern PR, this will be followed by afternoon showers over
portions of the interior and western PR. However, rainfall amounts
should not be significant today. The mid-level ridge over the
central Caribbean will erode later today as an upper level trough
over the western Atlantic moves over the region by tonight. This
will coincide with the arrival of an easterly perturbation by
Thursday morning, resulting in scattered to locally numerous
showers across portions of the islands through much of Christmas
Eve. Urban and small stream flooding is possible with this
activity. A wind surge is expected as this weather pattern
unfolds, at least through Friday morning.

For Christmas Day, another mid to upper level ridge is forecast
to build from the west, and as the upper level trough moves
further east, more stable conditions are expected. Therefore, fair
weather conditions should return, with the typical trade wind
shower moving at times over land areas and shallow diurnal
activity developing over western PR and from streamers off the
smaller islands with minor rainfall amounts in general.

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

The weekend starts drier as an upper level ridge dominates the
forecast area. Precipitable water content is forecast to be at or
below 1.20 inches throughout Saturday. Although mainly fair
weather conditions can be expected for this day, pulses of shallow
moisture embedded in the easterly trade winds can generate
isolated passing showers. Between Sunday and Monday, weather
conditions will become wetter as a mid level short wave trough
builds to the west of Puerto Rico and erodes the mid level ridge
while an induced surface low settles north over the area. Expect
an uptick of shower activity on Sunday through Monday as the mid
level trough moves eastward through the Caribbean. Hence, on
Sunday, expect isolated showers over eastern Puerto Rico and U.S
Virgin Islands in the morning hours with scattered showers over
western half of Puerto Rico due to induced local effects in the
afternoon. With the induced low to the north, winds will shift
from the east to more southeasterly on Monday, pulling deeper
moisture over the forecast area. According to GFS, precipitable
water values will increase up to 1.7 inches. Therefore, expect an
increase in areal coverage of shower development for Monday with
light to moderate rainfall accumulations throughout the day
especially for the northwest quarter of Puerto Rico in the
afternoon hours. Tuesday will transition into a drier pattern as
the mid level trough and surface induced low continues to move
eastward, however lingering moisture could aid in some light
shower development across the area. With the passing trough,
expect winds to weaken and shift from the south to more westerly
by afternoon hours and northwesterly through Tuesday night. With
less cloud coverage as well, warmer than normal conditions can be
expected.


&&

.AVIATION...Mainly VFR conditions are expected to prevail across
all terminals during the next 24 hours. Low level winds from the
east to northeast at 15-25 kts.


&&

.MARINE...Seas are increasing and hazards are spreading across the
local waters. Small craft advisories are in effect for most of
the local waters. A high surf advisory is in effect beginning this
morning. 7 foot seas are expected to have abated from all areas
by Saturday afternoon. This swell event is also causing hazardous
coastal conditions across the north, west, and eastern-facing
beaches of Puerto Rico and most of the beaches in the U.S. Virgin
Islands, Vieques and Culebra.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 75 83 73 / 40 60 70 50
STT 84 74 84 74 / 30 60 60 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
453 AM AST Thu Dec 24 2020

.SYNOPSIS...

An easterly perturbation moving across the islands will result in
rainy conditions the Eve and the day of Christmas. A long period
northerly swell combined with fresh to locally strong trade winds
will promote choppy to hazardous marine conditions across most of
the regional waters through at least Friday. The long period
northerly swell is producing a high risk of rip currents, and
dangerous breaking waves along the north-facing beaches of Puerto
Rico the U.S. Virgin Islands.

&&

.SHORT TERM...Thursday through Saturday...

An upper-level trough moving across the western Atlantic is relaxing
the ridge pattern over Puerto Rico and the U.S. Virgin Islands. At
low levels, trade wind perturbation will increase moisture during
the Eve and the Day of Christmas. Rainy conditions will persist
under this pattern. Therefore, you can expect a mixture of sunshine
and clouds with frequent trade wind showers across the local waters,
the north and east portion of Puerto Rico, and the Virgin Islands.
The ponding of water in roads and poorly drained areas are the main
threat associated with this activity, even-though urban flooding is
still possible, especially in the east and SJ metro area. Also,
expect easterly winds between 15 and 20 mph, especially along the
coast.

A somewhat drier air mass will filter from the east after this
perturbation exit the region around Friday afternoon into Saturday.
However, do not rule out the typical occasional passing showers,
especially during the overnight and early morning hours. Then,
afternoon convection along the mountains and western sections of PR
and downwind from the USVI.

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

A more wetter weather pattern is expected between Sunday through
Tuesday as a upper level trough approaches the local islands from
the northeast. This feature will induce a surface trough at north
of the CWA, promoting moisture advection to the local islands.
According to model guidance, precipitable water values will remain
near normal between 1.5 to 1.7 inches. Therefore, at this moment,
expected isolated to scattered showers in the afternoon hours
over northwestern quadrant of Puerto Rico on Monday. Then, as the
aforementioned feature moves eastward into the Caribbean, winds
will shift from the east to more northeast increasing the shower
activity potential over the northern and southern coastal sections
of Puerto Rico. However, afternoon convection over interior
sections of Puerto Rico could not be ruled out. Urban flooding
and ponding of waters on roadways and in poor drainage areas will
remain possible in isolated areas with the heaviest rains.

By Wednesday into the Thursday, as a building surface high pressure
move from the northwestern Caribbean, the upper level low short
wave will sink into the south near the leeward Islands. This will
result in an induce surface trough. This feature will move westward
into the area increasing the potential for shower activity over
the region.


&&

.AVIATION...

An easterly perturbation will bring passing SHRA/-SHRA across the
terminals today. Also, expect easterly winds between 15 and 20 mph
with higher gusts through at least 24/23z, when are forecast to drop
at 12kt or less. Cloud cover will range SCT-BKN between FL020-FL050
at times. Clouds and SHRA activity will increase across the interior
and western sections of PR between 24/15-23z.

&&

.MARINE...

Hazardous marine conditions are expected as a long period
northeasterly swell continues to invade the local waters. As a
result, Small craft advisories are in effect for most of the local
waters at least until Friday evening. There is a high risk of rip
currents for all local beaches at north coasts of Puerto Rico and
all the local beaches of Culebra, Vieques and the U.S. Virgin
Islands. There is also a High Surf Advisory in effect for northern
coasts except Vieques and Saint Thomas. An increase in shower
activity is expected over the local waters in the morning and
evening hours as an easterly perturbation move across the region
today.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 73 84 73 / 50 60 20 20
STT 84 74 84 74 / 60 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
450 AM AST Fri Dec 25 2020

.SYNOPSIS...
Active weather conditions will continue for the rest of the
morning hours today,as the low level moisture from the previous
easterly perturbation move out of the forecast area. As the day
goes by a more drier air mass is expected to filter into the
region improving the weather conditions. Hazardous marine
conditions will continue across the regional waters through the
weekend.


&&

.SHORT TERM...Today through Sunday...
The lingering moisture of yesterday`s easterly perturbation will
produce another round of showers across the local waters and the
windward sections of Puerto Rico and the U.S. Virgin Islands.
Although these showers are moving fast, they could produce ponding
of water with the heaviest activity. Satellite imagery indicated a
drier air mass approaching the islands from the east. It`s forecast
to move across the Virgin Islands around midmorning and then over
Puerto Rico by the afternoon, limiting rainfall accumulations.
However, urban and small stream flooding cannot be ruled out across
east-PR today.

A polar-trough (over the Eastern-Seaboard) and a through-low (over
the central Atlantic) will result in a ridge pattern over Puerto
Rico and the U.S. Virgin Islands. This ridge will slowly erode by
Saturday. A cold front will stall to the northwest of the islands
over the western Atlantic Ocean during the weekend. Under this
weather pattern, residents in PR and the USVI can expect the typical
winter climatology. Overnight and morning showers across the
windward sections, followed by afternoon showers across the western
and interior Puerto Rico, without ruling out rain activity downwind
from the Virgin Islands.

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

An increase in shower activity expected between Monday to
Tuesday as an elongated upper-level low trough approaches the local
islands from the northeast. An increase in moisture advection is
expected over the CWA as an induce a surface trough from the
upper-level trough stall at the north of the CWA. According to
both model guidance, Tuesday has better chances for more shower
activity due to the combination of the induced surface trough over
the area and total precipitable water content near normal. As the
aforementioned moves southeastward into the Caribbean, winds will
shift prevail with a north component increasing the shower
activity potential over southern coastal sections of Puerto Rico.
Therefore, minor flooding and ponding of waters on roadways will
remain possible with the heaviest rains. Given the wind flow
cooler temperatures can be expected.

The latest run model guidance shows, the building surface high
pressure over the western Atlantic will move over central
Atlantic resulting in a more easterly wind flow on Wednesday
pushing low- level moisture over the area. However, not
significant rainfall activity is expected at this moment on
Wednesday and Thursday. As the surface ridge moves over the
Central Caribbean a somewhat air drier mass will filter in the
region on late Thursday into Friday resulting in more fair weather
conditions for the last part of the long term.


&&

.AVIATION...
SHRA/-SHRA will continue across the terminals of JSJ/IST/ISX at
times through this afternoon, producing SCT-BKN ceiling between
FL020-FL060 through this period. Winds will persist from the east at
10 to 20 mph and gusty near SHRA. Clouds/SHRA will move into the
interior and western sections of PR between 25/15-23z.

&&

.MARINE...

The combination of a long period northeasterly swell and a wind
surge generated by a a surface high pressure is creating
Hazardous marine across the regional waters. Seas up to to 10 feet
are forecast over most of the regional waters, except the coastal
Caribbean waters. Therefore, Small Craft Advisories remain in
effect into this weekend. Coastal hazards include a high risk of
rip current over the north, western and eastern facing beaches of
Puerto Rico and all local beaches for Culebra, Vieques and the
U.S. Virgin Islands.




&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 73 84 73 / 40 30 50 50
STT 84 74 83 73 / 10 30 30 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
511 AM AST Sat Dec 26 2020

.SYNOPSIS...

A dry air mass will limit shower activity, leaving a mixture of
sunshine and clouds across the islands. However, a few trade wind
showers will reach the windward sections of Puerto Rico and the
U.S. Virgin Islands at times, and isolated to scattered showers
may form across the interior and western portions during the
afternoon. The proximity of a frontal boundary will induce a
surface trough increasing the potential of frequent shower
activity early next week.

&&

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

A drier air mass moving across the region is producing a seasonal
weather pattern. Therefore, expect mostly fair weather conditions
with a few passing showers moving inland. Afternoon showers will
develop across interior sections of Puerto Rico due to the local
effects and diurnal heating. On Sunday, a cold front moving across
the western Atlantic will induce a pre-frontal trough over the
northeast Caribbean. This surface feature could result in a rainy
weather pattern across Puerto Rico and the U.S. Virgin Islands. An
unstable weather pattern will persist on Monday. GFS guidance is
suggesting moisture pooling over the islands as the frontal
boundary stall to the northwest of the islands, over the western
Atlantic.

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

A shortwave trough with a jet stream will move across the region
on Tuesday. This feature with an induced surface trough will
increase the potential to observe shower activity across the local
waters early Tuesday morning, followed by afternoon convection
across the west and interior sections of PR during the afternoon.
Thunderstorm activity may develop that day across the local waters
and near the islands of PR/USVI.

A shear line will dissipate north of the islands, and it is
forecast to be replaced by another cold front. This frontal
boundary could dig southward near the northeast Caribbean by the
second part of next week. While at low-levels, an induced surface
trough (or maybe a low-pressure) will move near the islands,
increasing instability. That said, the easterly winds will return
by Wednesday and onward, pooling moisture over the islands
Wednesday through Friday. Environmental conditions seem favorable
for the formation of isolated thunderstorms Thursday and Friday.

Model guidance suggests the aforementioned frontal boundary
digging down into the Caribbean, and behind it a below-normal dry
airmass by late Friday into the weekend.

&&

.AVIATION...

Mainly VFR conditions are expected across all TAF-sites thru at
least 26/16Z. Then, afternoon convection will develop across the
interior of PR and will possibly affect TJPS btwn 26/18-23Z.
Winds will prevail mainly from the E increasing at 10 to 15 kt
after 26/13z.

&&

.MARINE...
The combination of a fading northerly swell and moderate to
locally fresh easterly winds will result in hazardous marine
conditions across the local waters today. There is a Small Craft
Advisory for the Atlantic Offshore waters due to seas between 5
and 7 feet. Elsewhere, mariners should exercise caution due to
winds between 15 and 20 knots and seas up to 6 feet. A northwest
swell will reach the islands by Sunday afternoon, followed by a
northeast swell around Tuesday afternoon.

Beachgoers, there is a high risk of rip currents along the
northwest beaches in Puerto Rico, especially from Quebradillas to
Isabela.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 73 84 72 86 / 30 20 40 40
STT 72 84 73 85 / 30 30 50 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
413 AM AST Sun Dec 27 2020

.SYNOPSIS...

The proximity of a frontal boundary will induce a surface trough
increasing the potential of frequent shower activity early this
week. This weather pattern will promote moisture pooling across
the islands through the first part of this week. Marine conditions
could deteriorate in the second part of this week.

&&

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

A cold front moving over the western Atlantic will induce
prefrontal trough near the region Sunday and Monday. This induced
surface trough will move near the northeast Caribbean. The
combination of light winds and low-level moisture will result in
isolated to scattered showers over the windward sections of Puerto
Rico and the U.S. Virgin Islands through the day, and across the
interior and western sections of PR during the afternoon hours.
Under this conditions, prolonged periods of moderate to heavy
rainfall could triggers urban and small stream flooding.

On Tuesday, as the shear-line drift closer, it will induced
another surface trough over the region. A shortwave trough and a
jet stream aloft aloft will moves from the northeast increasing
instability. 500 mb temperatures will drop between -8 to -9
Celsius, the available CAPE will increase, and tropical moisture
will ramp-up promoting widespread showers and isolated
thunderstorms.

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

A short wave trough and a jet stream will remain aloft on
Wednesday. At the surface, a high- pressure (behind a cold front)
will move from the western Atlantic into the central Atlantic.
This surface high will push the frontal boundary near the region
Wednesday through Saturday. Once again, model guidance is
suggesting a FROPA around late- Friday night into Saturday. Behind
it, a drier air mass will promote pleasant temperatures and
little or no rain activity Saturday and even Sunday. That said,
the best chance to have flooding rains through the long-term, even
thunderstorm activity, will be Wednesday through Thursday.
However, it`s too early to talk about rainfall accumulations
through that period. If GFS is correct, an increase in local winds
between 20 and 25 mph could be possible from late Wednesday night
onward.

&&

.AVIATION...

Mainly VFR conditions are expected across all TAF-sites thru at
least 27/16Z, with VCSH possibles over TJSJ, TISX, TNCM, TIST and
TKPK. Then, afternoon convection will develop across the
interior/W-PR and will possibly affect TJPS between 27/18-23Z.
Winds will prevail mainly from the E increasing at 10 to 15 kt
after 27/13z.

&&

.MARINE...

Tranquil to choppy marine conditions will continue today into the
first few days of this new week. A small northerly swell will move
across the local waters this afternoon. Model guidance showed
increasing winds and seas around 20 to 25 knots and at 8 feet or
higher late Wednesday into the upcoming weekend, respectively. If
this is correct, hazardous marine and coastal conditions would be
possible.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 73 84 73 / 30 40 40 50
STT 84 73 84 73 / 40 40 40 50