Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
459 AM AST Mon Nov 8 2021

.SYNOPSIS...Mid-upper high pressure will hold over the local
region the entire week. Although stable conditions will prevail
over the next several days, low level moisture embedded in the
trade winds will reach the local islands from time to time. No
significant rainfall is anticipated as the current pattern does
not support extended periods of heavy rains.

&&

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

High pressure at the surface nosing into the northeastern Caribbean
from the north central Atlantic Ocean will not yield much to the low
pressure migrating to the east northeast from the offshore waters of
the Carolinas. This will cause east southeasterly flow at the
surface today and easterly flow Tuesday and Wednesday. Columnar
moisture began growing over Saint Kitts and Saint Martin yesterday
at noon and has begun drifting into the local forecast area this
morning. Showers are increasing in the bow wave of the easterly flow
around Puerto Rico but the area of cloudiness still over Saint
Martin has little if any rain and is suspected to be mostly
stratocumulus or low altocumulus. The moisture there is expected to
move west northwest and will only brush Puerto Rico. Nevertheless
this should be enough to cause some showers to develop over western
and interior Puerto Rico this afternoon after the limited showers
over eastern Puerto Rico this morning. High pressure at mid levels
will continue to envelope the local area and keep the layer between
11 and 35 thousand feet rather dry through at least Wednesday. This
will keep convective activity shallow. Winds will be fairly light,
however, so showers that do develop may bring some heavy rain
although flooding is not expected today. Monday and Tuesday will
bring a slight warming trend, but the shift to more easterly flow
Tuesday and Wednesday will keep temperatures moderated. Some 90s are
still expected on the south coasts of Puerto Rico and Cotton Valley
in Saint Croix.

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

Mid-upper level ridge will continue to dominate the weather conditions
in the extended range. This will keep dry and stable conditions
aloft as the high-pressure ridge remains over the region. At low
levels, a surface high pressure will establish over the Western
Atlantic, northof the area, between Thursday and Friday. As the
surface high migrates across the north Atlantic waters tradewinds
will strengthenlate in the week into next week. Under thisweather
pattern, a mixture of fair weather and passing showers during the
second part of the week. Then, stronger trade winds during the
weekend and early next week will likely result in more frequent
passing showers streamingacross the local islands. However, no
significant rainfall is anticipated as high pressure aloft will
prevent the vertical development of most of the showers.

&&

.AVIATION...VFR conditions will prevail through the forecast period.
Stable wx conditions are expected across the local area, therefore
no significantimpacts to operations are anticipated over the next
24 hours. SHRA, if any, will form near TJBQ between 08/18Z-21Z. As a
result, VCSH was included at TJBQ. E to ESE winds of 10-15 kts will
continue below FL150. Maximum winds will be less than 20 knots blo
FL540.

&&

.MARINE...Tranquil marine conditions are expected through Tuesday
morning. Then, marine conditions will deteriorate especially across
the Atlantic Waters and Caribbean Passages as a north- northwest
swell invades the local waters late Tuesday. Also, moderate to
fresh winds will produce choppy seas the second part of the week.
Therefore, mariners should exercise caution starting on Wednesday
as confused seas, wind waves and swells, will create hazardous
conditions.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 76 87 76 / 30 40 20 30
STT 85 75 87 76 / 40 30 30 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
504 AM AST Tue Nov 9 2021

.SYNOPSIS...Mid-upper high pressure will maintain relatively
stable conditions over the next several days. However, plenty of
low-level moisture embedded in the trade winds will reach the
local islands from time to time. Light rainfall accumulations are
expected as the ridge pattern does not support significant
rainfall. A northwest swell will reach the Atlantic coastlines
tonight increasing the risk of rip currents to high through late
in the work week.

&&

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

High pressure at the surface nosing into the northeastern Caribbean
from the north central Atlantic Ocean will not yield much to the
strong low pressure migrating to the east northeast from the
Atlantic waters east of North Carolina. This will cause easterly
flow at the surface today and east northeast flow Wednesday and
Thursday. An area of moisture that was over the Leeward Islands
yesterday has moved to eastern Puerto Rico this morning and will be
followed by more pulses during the next several days. The second
pulse should move into the U.S. Virgin Islands by noon today. The
moisture over eastern Puerto Rico will move into western Puerto Rico
by this afternoon. Showers and moisture will be a little better
today than yesterday there. Patches of moisture interspersed with
drier air at lower levels move through the area through Thursday,
bringing periods of fair weather and scattered showers to eastern
Puerto Rico. Western Puerto Rico will still experience scattered
showers mainly during the afternoons. Showers may linger in the west
a little later this evening.

High pressure at mid levels will continue to envelope the local area
and keep the layer between 11 and 35 thousand feet very dry today
through Wednesday night and rather dry through at least Thursday.
This and an inversion of around 3 degrees Celsius will keep
convective activity shallow. Winds will be fairly light, however, so
showers that do develop may bring some heavy rain with ponding of
water in low lying areas. Surface winds are expected to increase
somewhat tonight through Thursday.


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

The GFS 500mb anomaly analysis suggests that the mid-upper level
ridge will hold strong through early next week. This will lead to
generally dry and stable air mass at mid-levels trapping the
moisture in the low levels. Under this pattern, organized
convection will be limited or even suppressed due to the
presenceof the inversion cap. On Friday, a front will stall far
north of the islands, while allowing fragments of moisture to
stream westward over the forecast area. During the weekend and
early next week, migratory highsswinging north of the area will
keepthe shallow clusters of clouds and showers streaming across
the U.S. Virgin Islands and Puerto Rico. This low-level moisture
will be carried by the trade winds favoring the light passing
showers over the windward areas from time to time. The exact
timing of these passing showers is difficult to forecast
especially this far out in the forecast.Western Puerto Rico will
likely experience shallow afternoon convection each afternoon due
to the sea breeze convergence followed by clearing during the
evening and overnight.

&&

.AVIATION...VFR conditions will prevail through the forecast period.
Although sct SHRA aft 09/15Z over interior and wrn PR will produce
lcl MVFR conds with mtn obscurations. SHRA, will form fm TJMZ south
between 08/18Z-21Z. ENE to E winds of 10-15 kts will continue near
the sfc. Maximum winds will be 20 kt or less blo FL540 with a
southerly component abv FL180.

&&

.MARINE...Tranquil marine conditions are forecast today,however
conditions will start deteriorating tonight intoWednesday asa
north- northwest swell invades the local Atlantic Waters and
Caribbean Passages. Also, moderate to fresh winds will produce
choppy seas the second part of the week as high pressure systems
moveacross the western Atlantic. Therefore, mariners should
exercise caution starting on Wednesday as confused seas, wind
waves and swells, will create hazardous conditions. Small craft
advisories may be needed between Wednesday night through Thursday
night.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 76 87 77 / 40 30 20 70
STT 87 76 87 77 / 40 40 30 50

[cycloneye]

000
FXCA62 TJSJ 110901
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
501 AM AST Thu Nov 11 2021

.SYNOPSIS...Generally fair weather conditions will prevail during the
next few days. Clusters of clouds of showers will continue to
propagate across the region, bringing showers to windward areas
from time to time. Although limited, convective development is
still anticipated over land areas. A northerly swell and
increasing winds will cause hazardous seas and life-threatening
rip currents through the end of the workweek and possibly into the
weekend.


&&

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

A broad surface high pressure will move from the western Atlantic
into the central Atlantic through the short term period, this will
promote moderate to locally fresh east to northeast trades. A front
south of the high is expected to remain above 22N, with the trades
bringing occasional patches of moisture across the local area, with
the front undergoing frontolysis. This will also favor a cool
advective pattern across the northern and eastern waters of the
islands, therefore, showers with minor rainfall accumulations are
expected to move at times across portions of the USVI and along the
east/north sections of PR. At upper levels, a ridge over the
northeastern Caribbean will remain as the main weather feature. This
should promote drier air aloft, and stable conditions in general to
suppress thunderstorm activity during the afternoon hours each day.
However, there should be enough moisture content each day to trigger
diurnally induced afternoon showers over portions of the interior
and west/southwest PR, and from streamers downwind of the smaller
islands.

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

Model guidance continues to suggest that a mid to upper level
ridging will remain as the dominant feature through most of the
forecast period. Although weak perturbations driven by the
subtropical ridge are expected to bring clusters of clouds and
showers, with increasing low-level moisture at times, a strong
trade wind cap and drier air aloft will limit the intensity and
areal coverage of any shower activity. The focus of the activity
will remain over windward areas of Puerto Rico and the US Virgin
Islands, whereas limited afternoon convective development is
anticipated over land areas. Generally moderate to locally fresh
east to east-northeast trade winds will prevail through the
forecast period, reaching highest intensity by early next week as
a developing surface high pressure extending over the western
Atlantic tightens the local pressure gradient. In turn, this will
support a higher frequency of evening-early morning showers
moving inland through at least Tuesday. By midweek, model
guidance now suggests drier conditions and a lower chance for
shower activity across the region, but confidence remains low
regarding any possible scenarios due to inconsistencies with the
most recent model solutions.


&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, trade wind showers may
move briefly at times across the local terminals through the
forecast period. Also, SHRA expected to develop over west PR btw 16z-
22z, which may cause brief MVFR cigs at TJBQ/TJPS. Low-level winds
will continue from the ENE at 10-15 kt, with sea breeze variations
after 14z.


&&

.MARINE...A northerly swell spreading across the regional waters
and increasing winds due to the tightening of the local pressure
gradient will maintain choppy and hazardous marine conditions
through at least Friday, mainly across the Atlantic waters and
local passages. As a result, Small Craft Advisories are in effect
due to increasing seas up to 7 feet. For beachgoers, there is a
high risk of rip currents for all north-facing beaches of Puerto
Rico, Culebra and St Thomas today. These dangerous marine and
surf zone conditions may continue into the upcoming weekend.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 78 88 77 / 40 40 20 40
STT 88 78 86 77 / 30 30 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
455 AM AST Fri Nov 12 2021

.SYNOPSIS...A northerly swell and increasing trade winds will
maintain choppy to hazardous seas and dangerous surf zone
conditions into the weekend. A typical weather pattern will
prevail, with clusters of clouds of showers propagating across
the region from time to time. Although limited, convective
development is still anticipated over land areas, with the
potential for ponding of water on roadways and low lying areas
over western Puerto Rico.


&&

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

A mid-level ridge will continue to hold over the region through the
short term period. This will continue to promote the trade wind cap
across the islands, and keep the best moisture trapped below 850 mb.
At the surface, a high pressure will build over the Central Atlantic
during the next few days, and at least through Saturday, steering
winds will continue from the east to northeast. Columnar moisture
increases somewhat on Sunday, and winds turn more easterly as the
surface high moves further east and a polar trough and associated
surface front moves across the western Atlantic. However, the area
will remain between these two features, and a similar weather
pattern is expected each day, with shallow patches of moisture
bringing the occasional trade wind shower across the islands,
followed by enhanced afternoon showers over the interior and western
PR.

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

No changes have been introduced in the forecast for Monday. A mid
to upper level ridge will remain as the dominant feature, with
frequent fast-moving weak perturbations driven by the subtropical
ridge and increasing trade winds bringing clusters of clouds and
showers from time to time. Although ridging aloft is expected to
hold over the region through the long term forecast period, model
guidance now suggest a relatively drier pattern earlier than
previously anticipated, with extensive pockets of drier and less
frequent patches of low-level moisture streaming across the region
between Tuesday and Wednesday, followed by the remnants of an old
frontal boundary reaching the forecast area by the end of the
forecast period. That said, the typical seasonal showers pattern,
with evening-early morning showers favoring the windward areas and
limited afternoon convective development over land areas, but
gradually decreasing in intensity and areal coverage as the week
progresses. Nevertheless, if the current model solution
materializes, an increase in shower activity can be expected by
the end of the workweek.


&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, trade wind showers will
continue to move at times across the USVI and northern/eastern
terminals through the forecast period. Afternoon SHRA over west PR
should cause mostly VCSH at TJPS. Low-level winds will continue from
the ENE at 10-15 kt, with sea breeze variations after 14z.


&&

.MARINE...Recent data from the near-shore and offshore Atlantic
buoys all continue to report choppy to hazardous seas between 5
to 7 feet at 11 to 13 seconds as the northerly swell continued to
spread across the local waters and passages along with the
increasing trade winds. Therefore, Small Craft Advisories remain
in effect through late tonight for the near-shore waters and
local passages and through at least Saturday morning for the
Atlantic waters. Since this will also generate dangerous surf
zone conditions, a High Surf Advisory and High Rip Current Risk
remains in effect for the northwest to north-facing beaches
including Culebra, while a High Risk of Rip Currents continues
for Vieques and the north-facing beaches of the northern U.S.
Virgin Islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 78 87 77 / 30 40 30 50
STT 83 79 83 80 / 30 30 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
409 AM AST Sat Nov 13 2021

.SYNOPSIS...Choppy seas and life-threatening rip currents will
continue through the weekend across the Atlantic waters and northern
beaches of the islands. A mid-level ridge will hold over the region
through next week. Trade winds will bring occasional passing showers
across the region, and diurnally induced afternoon showers are
expected to develop each day over western PR. A TUTT induced
surface trough is forecast to move from the east by midweek next
week, increasing the areal coverage of showers across the islands.


&&

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

Clusters of clouds and showers will continue to propagate across the
region under a generally easterly trade wind flow supported by a
building surface high pressure extending further east into the
western Atlantic. This scenario will continue to bring showers to
portions of eastern Puerto Rico and the US Virgin Islands through
the rest of the morning hours. As the day progresses, and aided by
local effects and diurnal heating, shower development is anticipated
across portions of the interior and western Puerto Rico in the
afternoon. Since a mid-level ridge continues to hold over the
region, supporting a strong trade wind cap, deep convective
development is not anticipated, and at most, ponding of waters on
roadways and low-lying areas remains possible with the heaviest
downpours. By tonight, a slight increase in low-level moisture will
support an increase in evening-early morning shower activity
affecting windward areas of Puerto Rico and the US Virgin Islands,
with a slight potential for localized urban flooding. A similar
weather pattern is expected for Sunday and Monday, dominated by
shallow patches of moisture propagating over the region.

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

Drier air ahead of a TUTT induced surface trough on Tuesday will
move across the region from the east. This, in combination with a
mid-level ridge aloft should promote fair weather conditions and
very limited shower development across the islands. PWAT content
increases during the second part of the week, between 1.75 and 2.00
inches, as the surface trough streams across the eastern Caribbean.
At least through Friday, showers are expected to increase in
frequency and intensity, compared to previous days. At the mid/upper
levels, a ridge pattern will remain in place, extending from the
Caribbean Sea into the Atlantic waters, and the 500 mb temps will
remain relatively warm near -6 degrees Celsius. Later in the
weekend, model guidance suggest that the remnants of an old frontal
boundary could move over the northeastern Caribbean, but confidence
at this moment is low. Moderate northeast steering winds are
forecast to prevail through the long term period, but breezy
conditions are expected on Wednesday.


&&

.AVIATION...Mainly VFR conditions are forecast for all terminals
during the next 24 hours. However, brief MVFR conditions are
possible as trade wind showers stream across the area at times,
mainly affecting TJSJ and TJBQ, as well as the USVI and Leeward
Islands terminals through most of the forecast period. Afternoon
SHRA over west-southwestern PR may bring VCSH to TJPS. Winds will
remain from the ENE at 10-15 kt, with sea breeze variations after
13/14z.


&&

.MARINE...Choppy seas due to lingering northerly swell will continue
today across the Atlantic waters and portions of the local passages,
with seas ranging between 5 and 7 feet. Therefore, small craft
advisories remain in effect through at least Sunday, as the swell
slowly subsides through the weekend. Breaking wave action along the
north facing beaches of the islands will keep an elevated risk for
life-threatening rip currents, and a Rip Current Statement(CFWSJU)
is in effect for Puerto Rico, Culebra and St. Thomas. Moderate
easterly winds will continue through early next week, increasing by
midweek.

Another long period northerly swell and increasing winds will once
again promote hazardous seas and coastal conditions from late Monday
through Thursday.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 76 87 76 / 40 50 40 40
STT 87 77 88 77 / 30 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
326 AM AST Sun Nov 14 2021

.SYNOPSIS...Choppy seas across the offshore Atlantic waters and life-
threatening rip currents across the northern beaches of PR, Culebra
and eastern St. Croix will continue today. A mid-level ridge is
expected to remain in place over the region through next week. Trade
winds will bring occasional passing showers across the region, and
diurnally induced afternoon showers are expected to develop each day
over western PR. Moisture content increases during the second part
of the week.


&&

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

The typical seasonal weather pattern that has been observed in
recent days is expected once again today, dominated by clusters of
clouds and showers propagating across the region under a generally
moderate east to east-northeast trade wind flow generated by a
surface high pressure extending into the western Atlantic. That
said, expect showers moving over portions of eastern Puerto Rico and
the US Virgin Islands through the rest of the morning hours. Then,
in the afternoon, the combination of near normal moisture content,
with model-estimated precipitable water values around 1.50 inches,
and both local and diurnal effects will support shower development
across the interior and western sections of Puerto Rico. Although
mid-level ridging and associated strong trade wind cap should not
support deep convective development, prolonged periods of moderate
to locally heavy rains from shallow convective activity may produced
rainfall accumulations of 1 to 2 inches with isolated higher
amounts across these areas. For that reason, there is a potential
for ponding of water on roadways and poorly drained areas to
localized urban and small stream flooding.

Once again, an increase in the frequency of showers moving over
windward areas from the waters is expected after sunset, with the
potential for ponding of water on roadways and poorly drained
areas with the strongest downpours. A similar weather pattern is
expected for Monday, dominated by shallow patches of moisture
propagating across the region. However, a drier air slot is
expected to reach the area on Tuesday, limiting any chance for
showers across the forecast area.

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

A mid-level ridge west of the area is forecast to hold through the
end of the workweek, and weaken under pressure from a trough during
the weekend. At lower levels, an induced surface trough is expected
to move across the northeastern Caribbean during the second part of
the workweek, this will increase the areal coverage and intensity of
showers each day. A wind surge is expected on Wednesday ahead of the
surface trough. Thereafter, lighter winds are expected as the ridge
erodes under pressure from the upper level trough. In addition,
better columnar moisture is expected, and the precipitable water
content is forecast to oscillate between 1.75 and 2.00 inches
through the weekend. Also, 500 mb temps are expected to cool to near
-6.5 degrees Celsius, this could lead to the development of isolated
thunderstorms on Sat/Sun afternoons. However, will not include them
in the current forecast as confidence remains low at this moment.


&&

.AVIATION...Mainly VFR conditions are forecast for all terminals
during the next 24 hours. However, brief MVFR conditions are
possible as trade wind showers stream across TJSJ and TJBQ, as well
as the USVI and Leeward Islands terminals through most of the
forecast period. Afternoon SHRA over western PR may bring VCSH to
TJBQ. Winds will remain light and variable through 14/12Z, turning
from the ENE at 10-15 kt with higher gusts and sea breeze variations
thereafter.


&&

.MARINE...Choppy seas up to 7 feet due to a subsiding northerly
swell will continue today across the offshore Atlantic waters.
Breaking wave action along the north facing beaches of the islands
will keep an elevated risk for life-threatening rip currents, and a
Rip Current Statement(CFWSJU) continues in effect for the northern
beaches of Puerto Rico, Culebra, and the eastern beaches of St.
Croix. Moderate easterly winds will continue through early next
week, increasing by midweek.

Another long period northerly swell and increasing winds will once
again promote hazardous seas and coastal conditions from late Monday
through Thursday. And, a Small Craft Advisory (SCA) remains in
effect for the offshore Atlantic waters through at least late
Tuesday. SCA conditions are expected through midweek, across the
Atlantic waters and eastern waters of the USVI.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 76 87 76 / 40 40 40 40
STT 88 77 87 75 / 30 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
329 AM AST Mon Nov 15 2021

.SYNOPSIS...
Another northerly swell will maintain hazardous seas, and will
continue to be hazardous due to increasing winds later in the
week. Passing showers are expected every day, with afternoon
convection developing over western Puerto Rico.

&&

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

A mid-to-upper level ridge over the region will continue to promote
the trade wind cap through the short term period. Moisture embedded
in the trade winds will continue to bring occasional passing showers
across the USVI and eastern sections of PR through at least tonight.
This shallow layer of moisture, in combination with the sea breeze
convergence and daytime heating will be enough to cause showers to
develop once again over western PR during the afternoon. Up to an
inch of rain is possible with this activity. On Tuesday, model
guidance continues to suggest the arrival of a very dry air mass,
with PWAT dropping between 0.75-1.00 inches. Therefore, little to no
rainfall is expected in general across the islands. On Wednesday,
breezy conditions are expected as a wind surge moves ahead of an
induced surface trough from the east. In addition, a small surge in
low-level moisture is expected, and PWAT increases to just 1.25
inches. These conditions should cause in general a cool advective
pattern, with quick passing showers affecting mainly the USVI and
east/northeast sections of PR through the day.

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

A mid-level ridge continues to hold on Thursday, but will begin to
weaken in response of a trough to the east of the islands and
another one exiting the coast of the United States. At the surface,
the pressure gradient will remain tight with a steering flow out of
the northeast at around 20 knots. An induced trough is expected to
cross the area by Thursday and Friday, with precipitable water
values climbing to near 1.8 to 2.0 inches and with the layer of
moisture extending deeper into the atmosphere. Therefore, the
frequency of showers is expected to increase, with an advective
pattern for the eastern half of Puerto Rico and for the U.S. Virgin
Islands, and additional activity developing over the west of Puerto
Rico during the afternoon hours.

On Saturday, some moisture from the surface trough is expected to
linger around. Additionally, as a frontal system approaches from the
northwest and the surface high weakens, the winds are expected to
relax. The GFS forecast soundings show the steering wind flow
turning from the east at around 5 knots. Then, on Sunday, as the
frontal system gets closer, the wind flow is expected to turn from
the north to north-northeast. On the latest GFS run, the system will
bring an increase in showers and isolated thunderstorms over the
area. It is worth mentioning that this is a long-term scenario and
the confidence in the forecast is low at this time.


&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, trade wind showers will
continue to move at times across the USVI/Eastern terminals of PR
thru Monday morning. Then, SHRA over western PR may cause brief MVFR
cigs at TJBQ. Low-level winds will continue from the east at 10-15
kt, with sea breeze variations after 14z.


&&

.MARINE...
Another northerly swell is expected to invade the local waters
today, maintaining hazardous seas for the Atlantic waters and
local passages. Winds are expected to increase by early in the
workweek. Small craft advisories are in effect for the offshore
Atlantic and will be in effect for the waters around the Virgin
Islands, Anegada Passage and sections of the offshore Caribbean.
Seas 5 to 8 feet are expected with winds up to 20 knots. For the
beaches, there is a high rip current risk for the northern coast
of Puerto Rico and Culebra, and for northern St. Thomas starting
this evening.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 76 86 76 / 30 30 10 20
STT 88 75 87 76 / 40 40 10 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
441 AM AST Tue Nov 16 2021

.SYNOPSIS...
Hazardous coastal and marine conditions will persist through
midweek due to a northerly swell and increasing winds. Generally
fair weather is expected today due to a drier air mass filtering
in. Patches of moisture as expected to increase by the latter
part of the workweek, enhancing the probability of showers.

&&

.SHORT TERM...Today through Thursday.

Moisture will erode today, and little to no shower activity will
affect Puerto Rico and the U.S. Virgin Islands. Trade winds
disturbances will bring an increase in humidity with a showery
weather pattern Wednesday and Thursday. However, an upper-level
ridge with a mid-level high pressure will create hostile atmospheric
conditions for vertical development, thus thunderstorm formation
is not anticipated. Although the upper level-ridge will weaken
today and onward as a polar trough near the western Atlantic moves
eastward, the mid- level high pressure will hold over the region,
maintaining relatively stable weather conditions.

Winds will increase today into Wednesday in response to the
strengthening of the local pressure gradient. Low RH values
associated with the dry air mass arriving today, the increasing
winds, and the available dry fuels across the Southern Coastal
Plains of Puerto Rico required the issuance of a Fire Danger
Statement (RFDSJU) today.

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

A surface high pressure located over the north-central Atlantic will
maintain winds low level winds out of the east to east-northeast at
around 15 knots for Friday. The steering flow will continue to drag
patches of moisture into the area, with precipitable water values
around 1.8 to 2.0 inches, which is above normal for this time of
year. At the mid-levels, the ridge should begin to weaken due to
a polar trough exiting the eastern coast of the United States. As
a result, moisture is expected to extend deeper into the
atmosphere, with mid-level relative humidities increasing above
70%. As is usual under this pattern, advective showers are
expected to move over the U.S. Virgin Islands and eastern Puerto
Rico through the morning hours, followed by afternoon activity
over western Puerto Rico.

The weather for the weekend will depend on the proximity to the
region of a prefrontal trough. So far, the guidance show that this
feature may get close enough to the islands by late Saturday into
Sunday. Temperatures at 500 mb are expected to drop to
-6 degree Celsius, increasing instability aloft. Therefore, another
increase in showers, and possible isolated thunderstorms is
anticipated for the latter half of the weekend. For the first couple
of days of the next workweek, not much changes are expected in the
weather pattern, as the trough and its associated moisture will
remain in place over the eastern Caribbean. Additionally, the
pressure gradient will weaken in response to this trough by Saturday
onward , with the steering flow around 4 to 7 knots, meaning that
the shower activity could linger for a longer period of time over
the same places. Since this is a long term forecast, the confidence
in the forecast is low at this time, and hence the forecast will be
adjusted accordingly in the next few days.


&&

.AVIATION...VFR conds expected through the forecast period. Winds
will increase between 15 and 20 kt with higher gust and sea breeze
variations after 16/12z, winds will become calm to light and VRB
once again through the nighttime (16/22z-onward).


&&

.MARINE...
Hazardous marine conditions continue due to a northerly swell
invading the local waters. During the night, near buoy
observations ranged between 4-6 feet with a period of around 16
seconds. The outer buoy (41043) was showing seas up to 7 feet.
Additionally, winds are expected to pick up by later tonight into
mid-week, maintaining hazardous seas through at least midweek.

Small craft advisories are in effect for most of the local waters,
due to seas 5 to 8 feet and winds out of the east at 15 to 20
knots, with stronger gusts. For the beaches, there is a High Surf
Advisory for the northern coast of Puerto Rico, Culebra and St.
Croix. There is a high rip current risk for the northern coast of
Puerto Rico, Vieques, Culebra, St. Thomas and St. Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 76 85 76 / 0 30 30 50
STT 87 77 87 78 / 10 30 50 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
429 AM AST Wed Nov 17 2021

.SYNOPSIS...
Marine conditions will continue to be hazardous due to increasing
winds. These winds will result in an increase in passing showers
moving over the islands for the next few days. Additional areas
of clouds and showers are expected for the weekend and for the
next workweek.

&&

.SHORT TERM...Today through Friday.

An advective and showery weather pattern will persist through
Friday. A high surface pressure migrating from the west to the
central Atlantic will tighten the local pressure gradient,
increasing local winds today and Thursday. Therefore, trade wind
perturbations will arrive, increasing the available moisture and
promoting a showery weather pattern lasting through the Short Term
Period. However, an upper-level ridge with a mid-level high pressure
will make it challenging to form thunderstorms today. Instability
will increase somewhat Thursday and Friday, as the upper-level ridge
and the mid-level high-pressure wane in response to an approaching
polar trough Thursday and Friday.

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

A weakening surface high pressure system over the central Atlantic
will maintain a wind flow out of the east-northeast on Saturday. So
far, the GFS show a trade wind cap inversion at around 900 mb, with
precipitable water values just above 1.0 inch and mid level relative
humidities below 20%. This should translate in limited shower
activity over the region. However, later in the day and into Sunday,
moisture from an old frontal boundary should advance over the
eastern Caribbean. This should result in an advective pattern
(showers moving over eastern Puerto Rico and the U.S. Virgin
Islands) during the morning hours, followed by convection developing
over the west in the afternoon. So far, none of the global models
nor de NBM (National Blend Model) are showing significant rainfall
accumulation associated with this event.

By Monday, as a cold front exits the eastern coast of the United
States, winds will shift more from the east, then southeast on
Monday night, from the south to south-southwest on Tuesday, and from
the northwest by Wednesday. On Monday and Tuesday, enough low level
moisture and local effects should work to generate shower activity
over the area. Then on Wednesday, with the cold front still to the
north of the area, instability should begin to increase, with 500 mb
expected to cool down between -7 to -8 degree Celsius. This should
be enough to fuel additional showers and isolated thunderstorms
cannot be ruled out. Since this forecast is still a few days
away, the details regarding intensity, coverage and timing of the
rain will likely be adjusted during the next cycles to reflect the
latest changes in the forecast.

&&

.AVIATION...VFR conds expected through the forecast period.
SHRA will increase in frequency and intensity across the local
flying area and could move across terminals at times. Winds will
increase between 15 and 20 kt with higher gust (up to around 30 kt)
and sea breeze variations after 17/12z, winds will diminish at 15
knots or less through the nighttime (17/22z-onward).


&&

.MARINE...
Near buoy observations, as well as the offshore Atlantic buoy
(41043) are showing that wave heights and periods are decreasing
as the northerly swell subsides. However, hazardous marine
conditions will continue, with seas 5 to 8 feet, due to strong
winds, at 15 to 25 knots.

Therefore, small craft advisories remain in effect. For the
beaches, there is a rip current risk for the north-facing beaches
of Puerto Rico, Vieques, Culebra, St.Thomas and eastern St. Croix.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Thu Nov 18 2021

.SYNOPSIS...

Windy easterly winds will bring showers across the windward
sections of Puerto Rico and the U.S. Virgin Islands and move
inland throughout the day. Winds and rains will diminish on
Friday. However, the advection moisture will persist through the
weekend into early next week. An approaching frontal boundary
could promote a more wet pattern by the second part of next week.

&&

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

A surface high pressure exiting the eastern coast of the United
States will continue to move into the Central Atlantic. This will
maintain the pressure gradient tight, with a steering flow out of
the northeast at around 19 knots. At the mid levels, a ridge will
hold just north of Hispaniola, resulting in a trade wind cap
inversion around 850 to 800 mb. Therefore, the best moisture will
remain trapped at the lower levels and thunderstorm formation will
be inhibited. The strong winds will promote an advective cool
pattern, resulting in quick passing showers affecting the eastern
and northern portions of Puerto Rico, as well as the U.S. Virgin
Islands. Ponding of water on roadways and low-lying areas will be
possible with this activity.

By Friday, as the surface high continues to migrate eastward, the
pressure gradient will loosen up, and winds will become moderate.
The GFS is forecasting a pocket of dry air, with precipitable water
values dropping just below 1.0 inch, at least through the first half
of the day. This, along with the decreasing winds, should limit the
amount of showers dragged by the trade winds, although local effects
could still result in afternoon convection for western Puerto Rico.
Regardless, by the end of the day and into Saturday, additional
areas of moisture will filter in once again, bringing another round
of enhanced shower activity, especially for the USVI and eastern
Puerto Rico, and then fueling convection over western Puerto Rico in
the afternoon. Additionally, the wind flow will continue to weaken,
so some areas could experience higher amounts of rainfall
accumulation.

.LONG TERM...Sunday through Thursday

On Sunday, the trade winds will push moisture from an old frontal
boundary over the northeast Caribbean, resulting in an advective
pattern (showers moving over northern and eastern Puerto Rico and
the U.S. Virgin Islands). The potential for thunderstorm formation
could increase as a shortwave trough swings north of the region,
weakening the ridge pattern aloft.

A cold front forecast to exit the Eastern Seaboard will directly
impact local winds becoming easterly on Monday, shifting from the
southeast by early Tuesday morning, out from the south by Tuesday
afternoon, and northerly on Wednesday. The advection of moisture
will continue to promote pop-corn showers Monday and Tuesday, and
local effects should work to generate afternoon convection across
the interior during the afternoon.

A wet and more unstable weather pattern could develop as the
remnants of the cold front approach the region inducing pre-
frontal troughs Wednesday and Thursday. Instability is forecast to
increase, and mid-level temperature will be more prone to
thunderstorm formation. Since this forecast is still a few days
away, we will likely adjust the details regarding intensity,
coverage, and timing of the rain during the subsequent cycles to
reflect the latest changes in the forecast.

&&

.AVIATION...

Winds should pick up again today, coming out of the ENE at around
15 knots and gusts up to 25 kts for the Puerto Rico and U.S.
Virgin Islands terminals. SHRA/SHRA are expected across all
terminals, except TJPS, through the period. SCT SHRA will continue
to cause VCSH for most of the local area, but no significant VIS
reduction is anticipated.

&&

.MARINE...

Hazardous marine conditions expected through at least Friday.
Small Craft Advisories are in effect for most of the local waters
due to seas of up to 7 feet with occasional seas up to 9 feet.
There is also a high risk of rip currents for most east and north-
facing beaches in Puerto Rico and the U.S. Virgin Islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 77 87 76 / 50 50 30 40
STT 87 75 86 77 / 50 50 30 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Fri Nov 19 2021

.SYNOPSIS...

A slot of dry air will limit shower activity across the islands
today. The easterly winds will continue to push patches of
moisture with clouds and showers during the weekend into early
next week. An upper-level trough and an approaching cold front
will promote a wet and unstable weather pattern through the latter
part of the following work week.

&&

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

A mid-level ridge continues to hold near Hispaniola, resulting in a
trade wind cap inversion at around 850 mb over the eastern
Caribbean. At the surface, the high pressure located over the north
central Atlantic will continue to migrates northeastward, hence the
winds will slack off a little bit, still coming out of the east-
northeast at 10 to 15 knots. This should continue to promote an
advective cool pattern over the islands, with fragments of showers
advancing into the northern coast of Puerto Rico and the U.S. Virgin
islands. However, recent satellite imagery from GOES-16 shows a slot
of drier air filtering in from the north, with precipitable water
values dropping to near 1.0 to 1.2 inches. Therefore, the frequency
of the shower activity should continue to diminish across the area.
As is usual, in the afternoon, the available moisture and local
effects could still trigger convection over the southwestern
quadrant of Puerto Rico.

On Saturday, the guidance is showing some patches of moisture moving
into the area associated with an old frontal boundary located just
to the north of the islands. Although moisture will extend deeper
into the mid-levels of the atmosphere, conditions won`t be
particularly favorable for strong showers development, and only
moderate rainfall accumulation is anticipated, with the eastern
sections of Puerto Rico and the U.S. Virgin Islands receiving
passing showers, and then activity for the west in the afternoon.

On Sunday, the mid-level ridge will begin to flatten out in response
of a polar trough exiting the eastern coast of the United States. As
a result, the GFS-forecast soundings show that the trade wind cap
inversion will weaken. Also, the low level wind flow will continue
to diminish, now at around 10 knots. Since the environmental
conditions are not going to be as hostile, there is the potential
for some isolated thunderstorm formation in the afternoon for
southwestern Puerto Rico.

.LONG TERM...

A cold front moving across the Eastern Seaboard will shift the
local winds from easterly on Monday to the southeast on Tuesday
and then out from the north by Wednesday. Winds will return from
the northeast by Thursday as the high pressure behind the front
pushes the frontal boundary southward into the Caribbean. Moisture
advection will continue to promote isolated to scattered showers
Monday and Tuesday. Local effects with the influence of sea
breezes should work to generate afternoon convection across the
interior during the afternoon.

Instability will increase by mid-week as an upper-level trough
approaches from the west of the northeast Caribbean. Moisture
could pool over the local islands as a cold front approaches
Puerto Rico and the U.S. Virgin Islands, inducing pre-frontal
troughs Wednesday and Thursday. The consensus of the global models
is indicating a FROPA by Friday, which could drop local
temperatures. Since this forecast is still a few days away, we
will likely adjust the details regarding intensity, coverage, and
timing of the rain during the subsequent cycles to reflect the
latest changes in the forecast.

&&

.AVIATION...

VFR conditions expected to prevail through the forecast
period. Winds will be out of the ENE at 10 to 15 kts with stronger
gusts and sea breeze variations. VCSH will be possible after 22Z,
which could result in briefly reduction in VIS, low ceilings and
gusty winds.

&&

.MARINE...

Choppy seas will continue throughout the day, with hazardous seas
around 7 feet expected across the offshore Atlantic waters.
Therefore, a Small Craft Advisory is in effect for the Atlantic
Offshore waters. Elsewhere, seas should range between 4 and 6
feet and gradually improve during the weekend. Winds will also
improve through the weekend, and continue from the east to
northeast between 10-15 kt. Winds will veer from the southeast by
early Tuesday.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
459 AM AST Sat Nov 20 2021

.SYNOPSIS...

Near-normal moisture will support showers across the area, while
stability aloft will inhibit them. A typical pattern of shower
activity is expected. Stability will decrease tomorrow into the
start of the workweek, leading to increasing shower activity. More
active weather is likely for around midweek/Thanksgiving,
followed by a drying trend for the weekend.

&&

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

A mid-to-upper level ridge over the Caribbean Basin will continue to
promote dry air aloft and stable conditions at least during the rest
of the weekend. At lower levels, shallow areas of moisture
associated to the remnants of an old frontal boundary over the
Atlantic waters, and from a surface trough moving from the Leeward
Islands into the Caribbean waters, should aid in the development of
early morning showers across the USVI and east/northeast PR. This
influx of low-level moisture will then aid in the development of
diurnally induced afternoon showers over southwest PR during the
afternoon. However, latest model guidance suggest light to moderate
rainfall totals in general today. On Sunday, the ridge aloft will
start to slowly erode under pressure from a short wave trough over
the western Caribbean, and NE steering winds are forecast to
decrease slightly over the region. Showers are expected to develop
over the same areas, however, due to the nature of the slow moving
showers, rainfall amounts should increase, and minor flooding is
possible during the afternoon over the interior/southwest PR.

On Monday, a strong polar trough and associated surface front is
expected to move across the western Atlantic, this will cause winds
to turn more from the east and decrease to around 5-10 kt. The
overall moisture content is forecast to remain around normal
values(1.75 inches), and showers should linger a little longer than
normal along the Cordillera and west/northwest PR.

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

Moisture levels over the region are expected to be near normal on
Tuesday and through much of the workweek next week. To the north,
over the western Atlantic, a trough is expected to deepen, as a new
low forms in the tail of the trough off of an Alberta Clipper that
has made its way eastward to over Atlantic Canada/northern Quebec.
This system and its attendant front will significantly impact
conditions over our area through at least midweek. The steering flow
will be relatively weak, likely out of the south at the start of the
day on Tuesday, becoming more squirrelly, followed by becoming
more northerly Wednesday. Additionally, increasing moisture is
expected on Wednesday and Thursday, as the frontal boundary pushes
into the area from the north.

The deep-layer trough will lead to increasing instability into
Wednesday and Thursday. With the enhanced moisture - precipitable
water values may be above normal at times, especially on Thursday -
increasingly active weather is likely. There is the potential for
thunderstorms, especially during the afternoons, for Wednesday and
Thursday.

Thursday night into Friday, drier air will push in from the north
behind the frontal boundary. Precipitable water values are forecast
to fall to below normal values. And, on Friday into Saturday, a mid-
to upper-level ridge will build into the area from the west,
decreasing instability. Fair weather is expected, therefore, for the
end of the week and through the weekend next week. A few showers in
a typical pattern cannot be ruled out, but shower activity will be
significantly inhibited. Additionally, the northerly flow over the
region is expected to linger, and cooler temperatures will likely
prevail.

&&

.AVIATION...

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. VCSH expected at TJPS between 18z-22z.
ENE winds are expected to increase btw 10-15 kt.

&&

.MARINE...

Seas are gradually subsiding, but wave heights of up to 6 feet
remain possible, especially for the offshore Atlantic waters.
Typical marine conditions are expected to prevail over the next few
days, with seas of 4 to 5 feet or less starting tomorrow and lasting
into midweek. Watching the potential for hazardous conditions
beginning around Thanksgiving, associated with a northerly swell.
Winds remain generally out of the east at up to 15 knots.

There is a moderate risk of rip currents for beaches of northern and
eastern St. Croix, northern and western St. Thomas, Culebra, and
northern Puerto Rico.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
504 AM AST Mon Nov 22 2021

.SYNOPSIS...

Generally fair weather with isolated to scattered showers in a
typical pattern are expected, followed by drying for the rest of
the early week. For the second half of the week, the approach of a
frontal boundary from the north will bring increasing moisture and
instability to the area. Wetter, more active weather conditions
are expected.

&&

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

Overall, isolated to scattered showers are expected during the
overnight hours over the next couple of days. Moderate to locally
heavy rain is possible this afternoon across PR, though mainly
across the western interior; but fewer showers and less rainfall
accumulation is expected on Tuesday and Wednesday. Temperatures will
be near normal and the wind will gradually decrease through the
short term period. Winds will be light and easterly today, then will
become SSE on Tuesday but still light, then variable on Wednesday.

A mid-to-upper level ridge over the Caribbean Basin is eroding and
a broad polar trough will gradually move closer to the local area by
Tuesday into Wednesday. Even though there is relatively dry air in
the mid and upper levels, there is low level moisture, which will
cause showers in the morning hours, as well as combine with the
diurnal heating and local effects, to cause moderate to briefly
heavy showers across portions of central to western PR this
afternoon. Some minor flooding is possible this afternoon,
especially in areas with poor drainage.

By Tuesday, the polar trough and associated surface front is
expected to continue moving ESE across the western Atlantic, this
will cause winds to further decrease to under 10 KT and shifting
winds to a SE-SSE direction. The latest guidance indicates a
decrease in shower activity for Tuesday as well, though still
isolated to scattered brief showers are expected. The models have
delayed the arrival of the frontal boundary, keeping Wednesday
relatively dry over land areas, while the rain associated with the
front stays just to our north over the Atlantic waters. The rainfall
eventually makes it to the local area, but for the latter part of
the week, beyond the short term period.

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

Model guidance continues to show the progression of a frontal
boundary towards the region for the second half of the week, likely
moving over the area Thursday into Friday. Exact timing remains
uncertain, as does the extent to which the boundary will make it
over and past the area. This is in large part due to uncertainties
related to the low/trough with which it is associated. It appears
likely that the low will stall out over the western Atlantic, in the
vicinity of or south of Nova Scotia. From there, the GFS and Euro
both suggest that the system will spin off a secondary center of low
pressure. There is uncertainty related to how these two lows will
interact, as well as with the exact details, though the system is
expected to stall out for some time, halting progression eastward of
the front. Beyond that, there is some additional uncertainty with
the interaction of this system with another behind it.

Regardless, it is likely that the frontal boundary will make its way
at least partway across the area. Some dry air appears likely to
make its way in behind the front, moving north to south, though said
dry air is unlikely to make it across the islands. With the
additional moisture and instability, active conditions are expected
for Thursday into Friday. After that, with the front stalling out
and then likely returning back northward, moisture will persist over
the region for the most part. The dry air could result in a brief
decrease in activity, especially over the Atlantic waters, likely
Friday into Saturday. After that, with the front stalling out and
then likely returning back northward, moisture will persist over the
region for the most part. The mid-level trough will move away from
the area as a ridge builds in from the west. Stability will increase
for the weekend into next week. Even so, a typical shower pattern
will be maintained by low-level moisture.

&&

.AVIATION...

VFR conditions are expected across the local terminals through
the next 24 hours. VCSH possible through 22/14Z, with SHRA
affecting the local flying area. Light easterly winds expected
through the day, with winds generally at 10KT or less. Sea breeze
variations expected at TJPS, causing SE-SSE winds between
22/15-21Z. VCSH at TJBQ, TJSJ, and TJPS possible after 22/17Z due
to +SHRA/SHRA across portions of PR.

&&

.MARINE...

Seas generally 4 feet or less across most of the waters, with seas
of up to 5 feet for the offshore Atlantic waters today. Winds remain
generally out of the east to east-southeast at up to around 10
knots. These typical or better conditions persist into midweek.

On Thursday, it appears likely that a northerly swell will arrive in
the local waters, generating hazardous conditions. As there remains
uncertainties with the forecast of the low associated with this
swell, some uncertainty remains with this forecast. That being said,
seas of up to 8 feet are expected, with gradual improvement at the
end of the week.

There is a moderate risk of rip currents for beaches of northern
Puerto Rico, Culebra, and eastern St. Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 75 87 76 / 20 20 30 10
STT 85 76 84 74 / 30 30 10 10

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
452 AM AST Tue Nov 23 2021

.SYNOPSIS...Isolated to scattered showers expected over the local
waters, USVI, and eastern PR in the overnight hours and early
mornings today and Wednesday, with afternoon showers developing
over central to western PR. An approaching frontal boundary will
cause an increase in cloudiness and shower activity starting on
Thursday, stalling over the local area through the weekend.

&&

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

Patchy moisture will persist over the area for the next couple of
days. Meanwhile, there remains a mid- to upper-level ridge over the
area, promoting stability. The patches of moisture will generally be
constrained to the lower levels, where they will support some shower
activity in a typical pattern. However, the ridging aloft will
inhibit the activity, and no significant, organized convection is
expected. Steering flow is increasingly light over the region as we
make our way into midweek. Today, the flow, such as it is, will be
generally out of the southeast to south-southeast, becoming
effectively variable by overnight tonight. As such, showers that
develop during the afternoons are expected to not move very much,
likely affecting mostly interior Puerto Rico and drifting into
northern/northwestern Puerto Rico. With these slow-moving or nearly
stationary showers, locally high rainfall amounts are possible; on
the whole, however, rainfall amounts are likely to be generally low.

A frontal boundary is slowly approaching the area from the north.
The associated trough is forecast to stall out over Atlantic
Canada/the western Atlantic. There is some lingering uncertainty
with the exact behavior and strength of this low. The most likely
scenario is that the boundary will make its way into the CWA on
Thursday, likely late. Meanwhile, the ridge aloft will also be
eroded, providing instability as a deep-layer trough swings into the
region from the northwest. Increasing shower activity is expected
with the approach of this frontal boundary during the day on
Thursday.

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

Overall, a cloudy and rainy weekend is expected, with near normal
high temperatures. More seasonable weather is expected on Tuesday
and Wednesday.

A frontal boundary is forecast to stall over the local area during
the long term period. This will keep the local area under deep
moisture through the weekend and possibly into Monday as the front
degrades. Therefore, cloudiness, showers and isolated
thunderstorms are forecast though those days. Drying up slightly
on Tuesday and Wednesday, but enough moisture will prevail to
cause showers over the local area. That said, the rainfall pattern
expected on Tuesday and Wednesday would be more seasonable, with
scattered showers over the waters, USVI, and eastern PR in the
overnight hours, then some showers across central to western PR in
the afternoon hours, under variably cloudy skies. The daytime
high temperatures will be below normal on Friday and Saturday with
a northerly wind flow, but a return to near normal temperatures
are to be expected on Sunday onward, as easterly winds return.

&&

.AVIATION...Generally VFR conditions are expected across all terminals for the
next 24 hours. Shower activity likely to be mostly over the interior
of Puerto Rico, drifting into northern/northwestern areas,
generating VCSH for TJBQ/TJSJ, in the afternoon. Winds generally out
of the southeast at 10 knots or less after sunrise, with sea breeze
variations. After sunset, winds diminish, becoming generally light
and variable.

&&

.MARINE...Seas of 2 to 5 feet are expected through Wednesday
night, with seas becoming hazardous on the latter part of the week
due to a northerly swell. The winds over the waters will be light
and southeasterly today, becoming variable on Wednesday, then
northerly starting on Wednesday night until Friday as it increases
up to 15 knots. There is a moderate risk of rip currents today
for the northwest to northeast beaches of PR and Vieques, as well
as most of Culebra. THere is also a moderate risk of rip currents
for most of the beaches of the USVI.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 76 86 75 / 40 10 20 40
STT 85 74 85 75 / 10 10 10 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
429 AM AST Wed Nov 24 2021

.SYNOPSIS...Isolated showers expected over the local
waters, USVI, and eastern PR this early morning, with afternoon
showers developing over central and southern PR. An approaching
frontal boundary will cause an increase in cloudiness and shower
activity starting on Thursday, stalling over the local area through
the weekend. The marine conditions will be tranquil today, but
will become hazardous by Thursday afternoon and into the weekend.
The surf zone conditions will become hazardous starting tonight
across the north coast of Puerto Rico.

&&

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

Generally fair weather will continue today, with patchy low-level
moisture sustaining some shower activity over the region, in a
typical pattern. There remains stability aloft; though the ridge is
being eroded, it does linger today. As such, significant, organized
convection is unlikely. The steering flow remains light and is
becoming more northerly. Because of this, afternoon activity is
likely to remain over the interior of Puerto Rico, with showers
drifting slowly towards the south. With these slow-moving showers,
locally high rainfall totals are possible; on the whole, though,
rainfall amounts are likely to be unimpressive.

A frontal boundary continues to slowly approach from the north. It
is expected to make its way over the area tomorrow into Friday. This
boundary, like its associated trough, is expected to basically stall
out - the low over Atlantic Canada, the front over or just south of
the local islands. Dry air will push in behind the frontal boundary,
but is unlikely to progress through much of the region, likely only
as far south as over the local Atlantic waters/Mona Passage, or
possibly as far south as the northern parts of the islands. There
remains some uncertainty with respect to the exact details on the
extent to which the dry air will affect the region, and as such,
there is some uncertainty with the forecast for Friday. Otherwise,
forecast confidence is medium-high.

Active weather is expected Thursday into Friday. The ridge aloft
will erode today into tomorrow, providing instability over the area.
Thunderstorms are possible tomorrow into Friday. After that, a mid-
level ridge will gradually build in over the area, decreasing the
potential for organized convection.

.LONG TERM...Saturday through Thursday...

Overall, a variably cloudy and rainy weekend is still forecast as a
frontal boundary is over the local area, though the latest guidance
has recently backed off a little on the amounts of rain over the
local islands. Near normal daytime high temperatures and overnight
lows. Seasonable weather is expected on Monday onward in the long
term period.

A frontal boundary is forecast to stall over the local area and
remain over the local islands this weekend as it weakens. This will
keep the local area under higher than normal moisture through the
weekend as the front degrades. Therefore, cloudiness, showers and
isolated thunderstorms are forecast though the weekend. However, the
latest long term guidance is a bit drier compared to the past few
days. Also, the more significant drying is now forecast to start
earlier, so the shower activity is expected to diminish starting on
Monday. Thereafter, some shower activity is expected over the
waters, eastern PR and the USVI during the overnight hours, then
afternoon showers over PR could develop, as easterly winds and a
more seasonable pattern returns. The daytime high temperatures will
be below normal on Saturday, but a return to near normal
temperatures are to be expected on Sunday onward.


&&

.AVIATION...Generally VFR conditions are expected across all terminals for the
next 24 hours. Afternoon convection is expected over interior into
southern Puerto Rico, causing VCSH for TJPS. Winds will be generally
light and out of the north, with sea breeze variations.

&&

.MARINE...Seas of 2 to 4 feet are expected today, increasing up to 5
feet tonight. Seas becoming hazardous starting on Thursday due to a
northerly swell. The winds over the waters will be light and
variable today, then northerly starting late tonight until late
Friday night as it increases up to 15 knots. There is a moderate
risk of rip currents today for the northwest to northeast beaches of
PR and Vieques, as well as most of Culebra. There is also a moderate
risk of rip currents for the northern beaches of St Thomas and St
Croix. There will be a high risk of Rip Currents for some beaches of
northern Puerto Rico starting tonight, but all beaches of northern
PR and northern Culebra will have a high risk of rip currents
starting on Thursday. Keep in mind that even if the rip current
statement has an end time on Friday, this is mainly to account
for some possible uncertainty in the model guidance. The surf
zone conditions are forecast to remain hazardous through the
weekend and into early next week.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 75 83 75 / 20 60 80 80
STT 83 76 83 75 / 10 60 80 80

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
434 AM AST Thu Nov 25 2021

.SYNOPSIS...Unsettled conditions are expected today during
Thanksgiving Holiday as a cold front approaches the area,
bringing widespread shower activity. The front will remain over
the area into the upcoming weekend, resulting in additional
chances of showers, although of lesser coverage. Hazardous marine
and coastal conditions are expected into the upcoming weekend due
to a northerly swell.


&&

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

Recent satellite imagery as well as the NWS doppler radar, both
suggest increasing cloudiness and shower activity along with
isolated thunderstorms over the Atlantic waters, as the frontal
boundary and associated shear-line continued to sink southwards
towards the forecast area. This along with a deepening upper level
trough shifting across the region will bring unstable and active
weather conditions. So far mostly showers of light to moderate
intensity have reached portions of the north coastal areas of Puerto
Rico and just offshore of the northern U.S Virgin Islands. Expect
the frontal boundary and associated band of moisture to continue to
sag southwards then linger across the region through Friday and into
early Saturday.

Based on recent model guidance and present conditions which both
initialized well, the forecast for increasing moisture and
instability remains on track for the short term. All suggest a
fairly active weather pattern starting later today and continuing
through Friday and early Saturday. The frontal boundary will
approach and linger across the area, thus providing good moisture
pooling and low level convergence along with the instability aloft.
Moisture will rapidly increase with precipitable water values
expected to near 2.00 inches later this afternoon and during the
evening. In addition the deepening upper-level trough will sweep
across the region with a 60-70 knots jet max to cross the area
placing the region in the right rear quadrant, consequently favoring
strong divergence aloft. The combination of all of these factors
along with the 500 millibar temperatures between -8 to -10 degrees,
will result good potential for widespread showers with enhanced
thunderstorm activity across the area later today through Friday.

Activity will continue to reach northern Puerto Rico and the coastal
waters of the northern U.S. Virgin Islands during the rest of the
morning hours, then later spread and develop over land areas while
affecting interior and southern portions of Puerto Rico and the
adjacent islands including the U.S. Virgin Islands, later in the
afternoon and evening hours. As a result the potential for urban and
small stream flooding will increase especially with the heaviest and
most persistent rainfall activity.

Late Friday through Saturday, moisture along the frontal shear-line
is expected to drift southwards, but will meander over eastern
Puerto Rico and the U.S Virgin islands. However, upper level
conditions are forecast to become hostile for organized convection
as the upper trough is expected to lift north and east of the region
as a ridge builds overhead from the west. This will result in a
gradual diminishing of overall moisture content, as well as more
stable conditions aloft. Nevertheless, given that frontal moisture
remnants will persist, expect some low to mid level moisture to
return from the east. This will maintain the potential for isolated
to scattered shower activity across the area. The activity should be
focused across portions of the the U.S. Virgin Islands and parts of
the northeastern and eastern Puerto Rico especially during the
overnight and morning hours. By then afternoon convection is
expected mainly across western and southwestern Puerto Rico, as the
steering flow should be from the northeast. This will be in response
to the surface high pressure ridge building north of the area. That
said, expect the worst conditions and best chance for urban and
small stream flooding across the region later today through Friday,
with less favorable conditions for organized convection and
significant rainfall accumulations on Saturday.

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

Both GFS and ECMWF models suggest the lingering presence of the
frontal boundary over Puerto Rico and USVI by Sunday. The frontal
boundary is expected to initially stall throughout the day.
Meanwhile, another polar trough and associated strong surface low
exiting the eastern United States will settle over north central
Atlantic through Tuesday. The surface low will induce a wind shift
across the area from northeast on Sunday to southeast by late
Monday, and settles back to more east southeast by Tuesday. This
will cause the remnants of the frontal boundary to be pulled
northwestward throughout the first half of the long-term period.
Since the forecast area will be located just within the moisture
boundary as this happens, low-level moisture will gradually increase
on Sunday with precipitable water values close to 1.36 inches, peak
on Monday with 1.68 inches and later decrease to 1.26 inches by
Wednesday as the remnants of the frontal boundary retrogress
across the area.

A mid to upper ridge will maintain dry air and stable conditions
aloft hindering deep convection across the area and favoring a
more shallow convective activity. Therefore, expect a
continuation of a cloudy weather pattern with isolated to
scattered showers mainly over the eastern portions of Puerto Rico
and USVI during night and morning hours. Afternoon shallow
convection will depend on locally induced forcings such as surface
heating and sea breeze convergence. During this time, activity
will move to interior and, depending on the day and wind
direction, southwestern and northwestern sections of Puerto Rico
for Sunday and Monday/Tuesday, respectively. For Wednesday
onwards, a more seasonal weather pattern is expected with moisture
content becoming patchy and gradually increasing through the end
of the workweek. With this pattern, expect mainly fair weather
conditions with shallow areas of moisture embedded in the easterly
wind flow reaching the islands from time to time. This will cause
light passing showers across PR and the USVI on Wednesday and
becoming more frequent with increasing cloudy skies by Friday.


&&

.AVIATION...VFR conds til 25/14Z. An approaching frontal boundary
will bring increasing clouds and SHRA/Isold TSRA ovr the Atlantic
waters north of the islands thereafter. This will cause prds of
SCT- BKN lyrs nr FL022...FL050..FL090 with SHRA/Isold TSRA. Sfc
Wnds will be calm to light/vrb, bcmg fm N-NE around 10 kt with sea
breeze variations after 25/14z. VCSH/VCTS will be psbl at the
northern TAF sites of PR/USVI then ovr the interior and srn
portions of PR aft 25/16z. The frontal boundary is expected to
deteriorate local flying conditions en route and across PR/USVI
throughout the day w/prds of MVFR conds and brief Mtn Top obscr
psbl especially aft 25/16z.


&&

.MARINE...Marine and coastal conditions, due to a northerly swell,
are starting to deteriorate becoming hazardous and will continue
through the upcoming weekend. Seas are expected to range between 5
and 10 feet with occasional seas of up to 11 feet across the
Atlantic waters and local passages with the peak wave height
expected between this afternoon through Friday. Therefore, Small
Craft Advisories are in effect. Across coastal locations, there is
a high risk of rip currents across the beaches from Rincon
through Northeast Puerto Rico as well as the beaches of Culebra,
Vieques, and the USVI. There is also a High Surf Advisory in
effect for the beaches from Rincon through northeast Puerto Rico
as well as the beaches of Culebra from this afternoon into
Saturday due to breaking waves of up to 12 feet.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 75 82 74 / 90 90 70 50
STT 81 77 80 77 / 80 80 70 40

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
431 AM AST Fri Nov 26 2021

.SYNOPSIS...The front will continue to remain in the
vicinity of the area into the weekend, creating additional chances
for showers. A more seasonal weather pattern is expected for early
next week as a ridge builds aloft with a drying trend at upper-
levels. Hazardous marine and coastal conditions due to a northerly
swell will prevail through the weekend.

&&

.SHORT TERM...Today through Sunday

Recent satellite imagery suggest that the base of the mid to upper
level trough was now located between eastern Puerto Rico and the U.S.
Virgin islands, as an upper level ridge continued to build and
spread across the region from the west. In the low levels, the
frontal trough and associated boundary will continue to sink east
southeast towards the Virgin Islands and northern Leeward Islands,
as a surface high pressure ridge spreads eastwards across the
southwest Atlantic while inducing a moderate northeast wind flow and
cool advective pattern. This will result in periods of passing
clouds and showers across the local waters and mainly along the
north and east coastal sections of the islands through the rest of
the morning hours. Some of these shower will be locally heavy at
times and may cause ponding of water on roads and hazardous driving
conditions.

For the rest of today through Saturday, moisture remnants from the
depleting frontal boundary is expected to meander over eastern
Puerto Rico and the U.S Virgin islands. This will provide sufficient
moisture to favor afternoon convection across the islands with still
a slight chance for isolated thunderstorms today. Upper level
conditions will however continue to improve with drier and stable
air expected to prevail into the weekend as the ridge builds
overhead. This in turn will result in a gradual diminishing of
overall moisture content as suggested by recent model guidance, with
less potencial for thunderstorm development on Saturday and more
localized shower activity. Afternoon shower activity today should be
focused over the interior, east and southern slopes of Puerto Rico
as well as in and around portions of the U. S. Virgin Islands.
Widespread rainfall accumulations are however not expected today and
Saturday but the potential for urban and small stream flooding in
isolated areas will remain possible today with lesser chance on
Saturday.

On Sunday, a quick surge of low level moisture will return as low
level winds diminish and become more easterly. This will aid in
transporting shallow moisture and passing showers to the east and
northeast coastal sections of the islands. This will be followed by
afternoon showers development mainly over the west interior and
southwest sections of Puerto Rico and mainly on the west-end or just
downwind of the U.S. virgin Islands.

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

Remnants from the frontal boundary are forecast to linger across the
local area by Monday, although less defined and more fragmented than
in previous model cycles. Both GFS and ECMWF models suggest the
presence of a mid-level ridge over most of the Caribbean basin and
is expected to persist for most of the week. This will provide
subsidence aloft with fairly stable 700-500 mb lapse rates hindering
thunderstorm activity for the most part. A strong surface low
pressure across north central Atlantic will induce light southeast
winds over the area and later shift to a more easterly flow by
Wednesday as a surface high pressure builds over central Atlantic.
This will bring a more seasonal weather pattern with near-normal to
normal moisture content mainly confined to lower levels. Therefore,
expect mainly passing showers over the area with minimal rainfall
accumulations.

For Wednesday onwards, a gradual increase of moisture through the
atmospheric column is anticipated as another frontal boundary slowly
approaches and stalls northwest of the area through the end of the
long-term period. This will cause an increase of cloud coverage and
shower activity. GFS and ECMWF deterministic and ensemble models
mostly agree that shower activity will generally affect eastern PR
and the USVI especially during night and morning hours. However,
ECMWF has the frontal boundary farther away than GFS. Therefore,
confidence is low as it will depend on the evolution of the polar
trough and associated front by the end of the workweek through the
weekend.


&&

.AVIATION...A general north northeast wind flow around 10 knots will
prevail... becoming northeasterly and increasing to around 15 knots
with occasionally higher gust aft 26/14Z. SCT-BKN lyrs nr FL025...
Fl050..FL080 with SCT SHRA en route btw islands and ovr the regional
waters. Isold TSRA psbl btw U.S.VI and northern Leewards til 26/12Z.
SHRA/TSRA will spread across the interior and south to southwest
PR/USVI after 26/16z.


&&

.MARINE...Hazardous marine and coastal conditions will continue
across the Atlantic Waters and north, east and west-facing
beaches. Therefore, expect gradually building seas between 6 and
10 feet offshore and 5 to 8 feet near shore. There is a high risk
of rip currents for the Atlantic Coastline of Puerto Rico, most
beaches of Culebra, and north and east Vieques. The USVI have a
high risk of Rip Currents and a high surf advisory.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 81 74 84 75 / 70 30 40 30
STT 86 75 86 76 / 70 40 30 60

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
501 AM AST Sat Nov 27 2021

.SYNOPSIS...
Recent satelite imagery and the doppler weather radar suggest that
a much drier and stable weather pattern continued to spread across
the region during the overnight and early morning hours. Little
or no shower activity was noted over land areas with mostly light
showers over the coastal waters. This upper level ridge will maintain
its hold and remain the dominant feature through the weekend with
overall limited showers and pleasant weather expected. A slight
increase in trade wind moisture forecast by Monday and Tuesday as
winds become more east southeast and remnants of the old frontal
boundary returns to the area. However so far upper ridge is to
remain sufficiently strong to limit and inhibit significant convective
development.

&&

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

GOES-16 water vapor imagery shows strong subsidence above with the
frontal boundary southeast of the forecast area. A band of moisture
is producing cloudy conditions and some showers but it has stayed
mainly east of the U.S. Virgin Islands throughout the night.
Precipitable Water imagery at 0550Z continues to indicate values
below 1.0 inches over eastern half of Puerto Rico, which is more
than two standard deviations below normal for this time of year,
with up to 1.20 inches elsewhere putting values still below normal.
This has produced fair weather conditions across Puerto Rico and
U.S. Virgin Islands and is forecast to persist at least through
early afternoon as a mid-level ridge builds over the area. This
ridge will strengthen and remain throughout the short-term period.

Model guidance suggests a gradual increase of low-level moisture by
this evening as fragments from the frontal boundary get advected
across the islands. Precipitable water is anticipated to rise
slightly. However, shower activity will still be hindered with drier
air and stable weather conditions aloft. A few isolated showers
across windward coastal areas could be possible tonight and early
morning hours.

Winds will become light and shift to more east on Sunday and later
southeast by Monday. This will push the remnants of the frontal
boundary back across the forecast area. Low-level moisture is
expected to further increase with Monday peaking at near-normal to
normal values. The mid-level ridge will continue to inhibit convective
development. However, a slight increase in cloud coverage with isolated
to scattered showers at times could be expected as the remnants of
the front interact with the islands. No significant rainfall
accumulations is expected with any shower activity in the next
few days.

.LONG TERM...Tuesday through Sunday
The mid to upper level ridge slightly erodes as a short wave
rough crosses the west Atlantic. This will aid in weakening the
tradewind cap inversion and allow for an increase in moisture
transport as a weak easterly perturbation will move across the
area with winds remaining east southeast through Tuesday. Any
afternoon shower development should therefore be in the west and
northwest sections of Puerto Rico and mainly on the downwind side
of the U.S. Virgin islands or just offshore over the coastal
waters. By Wednesday and through the end of the work week, winds
will again become east to northeast and slightly increase as as
surface high builds north of the region. This will favor better
change for quick low level cloud fragments and passing early morning
showers along portions of the north and east coastal areas. However
no significant rainfall accumulations area anticipated. By late Friday
and into the weekend an upper level short wave trough will move north
of the region to further erode the upper ridge while inducing a low
level surface trough, in advance of a cold front which will enter
the western Atlantic and should stall well north of the region. As
a result light winds and the slight increase in low level moisture
and instability will provide a better chance for afternoon shower
development over part of the interior and west sections of Puerto
Rico ,and mainly on the west-end of the U.S. Virgin Islands. For
the most part however, no significant rainfall or weather feature
feature is anticipated at this time as a more seasonal pattern
should prevail.

&&

.AVIATION....Mainly VFR conditions are expected to prevail across all
the terminals during the next 24 hours. Surface winds from the ENE
at 10-15 kts with higher gusts at times, with southerly sea breeze
at TJPS aft 14z.

&&

.MARINE...
Based on recent data from the surrounding Atlantic buoys, hazardous
marine and surf zone conditions are expected to continue at least
through later this afternoon due to a northerly swell and the gentle
to moderate northeast to east trade winds. Small craft advisories,
High surf advisories and high rip current risk continue for portions
of the regional waters and local islands respectively. Please refer
to the latest Coastal waters forecast (CWFSJU), Marine weather message
(MWWSJU) and the Coastal Hazard message (CFWSJU) issued by the NWS WFO
San Juan for more details and updates about these ongoing marine
and coastal conditions.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 75 84 74 / 20 40 40 40
STT 86 75 85 76 / 20 30 30 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
411 AM AST Mon Nov 29 2021

.SYNOPSIS...A seasonable weather will prevail across the area during
the next several days with overnight and early morning isolated to
scattered shower activity across the local waters, with some the
activity affecting portions of eastern Puerto Rico and the USVI
followed by afternoon activity across western Puerto Rico. A mid and
upper-level ridge prevailing over the area will continue to
hinder the development of deep and organized convective activity.
A long dominant period northeasterly swell will result in choppy
seas, especially across the offshore Atlantic waters, through
mid-week.

&&

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

Although a weak trough from the west will migrate through the area
today, high pressure will dominate the Caribbean and a ridge will
build east of the area during the period. At mid levels high
pressure over all of the Caribbean will become centered just
northeast of the Leeward islands Tuesday and Wednesday. This will
keep the mid and upper levels fairly dry between 12-40 kft. At lower
levels moisture is patchy and promises to be best early Monday
night. Thereafter, lower level moisture is mostly confined to the
lowest 6 kft, but will still be abundant enough at times to bring
scattered showers in the typical diurnal pattern of morning showers
in the east and afternoon showers in the west and interior portions
of Puerto Rico, with generally isolated showers around the U.S.
Virgin Islands. Amounts will be limited in most areas to less than
one quarter inch due to the limited vertical extent of the
convection, but showers may still yield 1 to 2 inches in a few spots
each day due to light winds and local circulations over Puerto Rico.
Furthermore, although 500 mb temperatures will be generally
unfavorable for thunderstorms, these temperatures will cool Tuesday
and Wednesday and become slightly more favorable in a few interior
locations.

.LONG TERM...Thursday through Tuesday...

A shortwave trough resulting from a deep polar trough forecast to
move across the northwestern Atlantic on Thursday and Friday will
briefly weaken the mid and upper-level ridge. However, this
shortwave trough will be too far north to have any noticeable
effects on the overall weather pattern. Therefore, seasonable
weather conditions will continue with some overnight and early
morning passing showers across the local waters, with some of the
activity moving inland into portions of eastern Puerto Rico and
the USVI, followed by afternoon convection across western portions
of Puerto Rico. By next weekend, as the shortwave trough lifts
well northeast of the area, the mid and upper-level ridge is
expected to bounce back again, resulting in stable conditions
aloft. Meanwhile, at low-levels, a broad surface high pressure is
expected to build north of the area. This will tighten the local
pressure gradient and thus will cause an increase in the low-level
winds. As a result, a cool advective pattern with an increase in
the frequency of trade wind showers is likely, with eastern Puerto
Rico and the USVI observing the highest concentration. Some
locally induced activity is also possible across western Puerto
Rico during the afternoon hours. This cool advective pattern is
likely to continue into early next week. Overall, no significant
weather features that would result in significant rainfall
activity are expected to affect the area during the long-term
period.

&&

.AVIATION...VFR conds expected across all local terminals thru
29/21Z. Brief passing SHRA ern PR aft 29/10Z, then aft 29/16Z
SHRA ovr wrn and interior PR with lcl MVFR and mtn obscurations
till 29/23Z. Land breezes less than 10 kt thru 29/12Z, increasing
to 10-15 kts from the E with sea breeze variations aft 29/14Z. Max
winds W-WNW 40-50 kts btwn FL410-530.

&&

.MARINE...A long dominant period northeasterly swell between 11
and 14 seconds will affect the local waters through at least the
middle of the work week. Seas are expected to fluctuate between 3
and 6 feet, with the highest seas expected across the offshore
Atlantic waters. As a result of the northeasterly swell, a high
risk of rip currents will continue through at least Wednesday for
the northwest to northeast beaches of Puerto Rico as well as for
the beaches of Culebra, Vieques, and the USVI.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 76 87 75 / 30 30 40 40
STT 86 75 87 76 / 40 40 30 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
440 AM AST Tue Nov 30 2021

.SYNOPSIS...A seasonable weather will continue to prevail during the
next several days with overnight and early morning isolated to
scattered showers over the local waters affecting portions of
eastern Puerto Rico and the USVI followed by locally induced
afternoon showers over western Puerto Rico. A mid-level ridge
will continue to hold, hindering the development of deep,
organized convective activity and thus widespread, significant
rainfall activity is unlikely through the period. Choppy marine
conditions due to a northeasterly swell will continue across
portions of the Atlantic waters through mid-week.

&&

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

Mid level clouds continue to fade over Puerto Rico overnight as the
weak trough that brought showers and some thunderstorms to the
forecast area--mainly the local outer Atlantic waters--is now being
subsumed by a trough at 700 mb that is near 60 west and moving west.
This trough is expected to lose strength, but will move onshore over
the U.S. Virgin Islands and eastern Puerto Rico around midnight
Wednesday morning. Moisture from the top of a tropical wave moving
through the southern Caribbean will then reach the area on Wednesday
where it will spawn showers and isolated thunderstorms during the
day. Bands of moisture, none too distinct, will continue moving
through the area on the easterly flow. Low level flow at the surface
will be mainly driven by lower pressure over South America and the
higher pressure across the central Atlantic through the period.
Although a polar trough will travel east over the Atlantic several
hundred miles away, it is going to be too far north to have any
significant impacts over the local area. A mention of isolated
thunderstorms has been kept in the forecast for today and Wednesday
despite decreasing overall moisture due to 500 mb temperatures
lowering from less than minus 4 this morning to almost minus 6 on
Thursday afternoon according to the GFS. These may not occur if
local circulations to not render any support, however. Moisture
returns on Thursday afternoon and will give convection a boost over
western Puerto Rico.

The U.S. Virgin Islands will generally see fair conditions with only
isolated passing showers and limited rainfall, as synoptic features
remain weak.

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

Not much has changed in the overall synoptic pattern for the long-
term period. A mid-level ridge will continue to remain well
entrenched across the northeast Caribbean through the period. This
will hinder the development of deep, organized convective activity
and thus the potential for significant, widespread rainfall
activity. Meanwhile, at lower-levels, a broad surface high
pressure is forecast to build across the eastern and central
Atlantic. This will tighten the local pressure gradient during the
upcoming weekend and thus the low-level winds will increase
somewhat, resulting an advective weather pattern with patches of
low-level moisture moving across the area. This will feature
overnight and early morning passing showers across the local
waters, with some of the activity moving into portions of eastern
Puerto Rico and the USVI followed by locally induced activity
during the afternoon hours across western Puerto Rico. By early
next week, there are hints amongst the model guidance that a frontal
boundary will move into the western Atlantic due to a
extratropical low pressure system moving off the northeastern
United States and into the northwestern Atlantic. This frontal
system, at this time, is expected to remain far enough north to
not have any direct impacts to our area with the only indirect
effect being weakening the local pressure gradient and thus
resulting in lighter winds.

&&

.AVIATION...VFR conds expected across all local terminals thru 30/20Z.
Brief passing SHRA ern PR aft 30/10Z, then aft 30/16Z SHRA ovr
wrn and interior PR with lcl MVFR and mtn obscurations till
30/23Z. Land breezes less than 10 kt thru 30/12Z, increasing to
10-15 kts from the E with sea breeze variations aft 30/14Z. Max
winds W 35-45 kts btwn FL400-510.

&&

.MARINE...A northeasterly swell between 11 and 14 seconds will
continue to affect the regional waters through mid-week. Seas are
expected to range between 3 and 5 feet with occasional seas of up
to 6 feet, with the highest seas expected mostly across the
offshore Atlantic waters. A high risk of rip currents continues
for the northwest to northeast beaches of Puerto Rico as well as
for the beaches of Culebra, Vieques and the USVI.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 86 76 / 30 50 20 30
STT 86 76 86 77 / 40 40 20 30