Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
412 AM AST Fri Feb 12 2021

.SYNOPSIS...

A trade wind perturbation is bringing an increase in moisture to the
region today, helping to support shower activity. Decreasing
moisture is expected for this weekend; next week, dry air with
occasional patches of moisture passing through will lead to
generally fair weather, with isolated to scattered showers in a
typical pattern. Hazardous marine conditions are expected for the
offshore Atlantic waters and Anegada Passage through this weekend.
Additionally, there is a high risk of rip currents today for beaches
of northern Puerto Rico and Culebra.

&&

.SHORT TERM...Friday through Sunday...

A trade wind perturbation (detected with GOES-East) is near the U.S.
Virgin Islands. Satellite-derived Total Precipitable Water indicates
values between 1.2 and 1.5 inches of water approaching the islands
(PR/USVI). The aformentioned perturbation will increase cloudiness
and rain activity across the windward sections and regional waters.
An ASCAT pass also indicated winds between 17 and 28 mph (15 and 25
knots), which could push further inland these showers to affect
portions of the interior late this morning. Rain activity will then
spread into western Puerto Rico during the afternoon. Although rainy
conditions seem to be likely today, accumulations will not produce
significant flooding problems across the islands. However, ponding
of water is possible in roads and poorly drained areas.

A building ridge at mid-level ridge will promote subsidence and dry
air aloft, strengthening the trade-wind-cap and inhibiting organized
convection. However, a surface-high pressure across the Atlantic
Ocean will tight the local pressure gradient increasing winds
through the weekend. That said, surface winds will accelerate
through at least Sunday. Winds will veer from the east-southeast
through Saturday and will possibly return from the east by Sunday.
This weather pattern will leave the islands under the influence of
the arrival of trade winds perturbations and the diurnal cycle
during the afternoons. At this time, moisture will erode by Saturday
afternoon into Sunday.

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

Dry air persists across the region through the long term period,
with occasional patches of moisture streaming over the area; these
patches will bring precipitable water values to near-normal levels.
Aloft, a deep layer ridge at the mid-levels will be the dominant
feature, providing stability and dry air above around 700-850 hPa.
Additionally, an upper-level low is forecast to pass by the area to
the north early next week, then strengthen to the east and southeast
of the area; this will also lead to subsidence aloft for the region.
As such, generally fair weather is expected. The patches of moisture
will help to sustain isolated to scattered shower activity in a
typical pattern. No significant rainfall accumulations are expected.
Brisk winds are forecast to persist as well, likely through at least
midweek, associated with the strong surface high to the north of the
area.

&&

.AVIATION...

A perturbation will increase SHRA/-SHRA across the local terminals
today. Passing SHRA/-SHRA and SCT-BKN Btwn FL020-FL060 are likely at
TAF-sites. Rain activity will spread into W-PR Btwn 12/15z-23z,
increasing cloudiness. Winds will be out from the E-ESE at around 10
kt, accelerating at 15 to 20 kt with gusts up to 30 kt.

&&

.MARINE...

Moderate to fresh winds will persist across the local waters for the
next several days, with winds of up to 20-25 knots during the day.
These brisk winds continue to cause building seas, and hazardous
conditions will persist through the weekend for the offshore
Atlantic waters and Anegada Passage, with seas of up to 7 feet. For
most of the rest of the local waters, seas of up to 6 feet are
expected, and operators of small craft should exercise caution.

For the beachgoers, there is a high risk of rip currents for beaches
of northern Puerto Rico and Culebra today.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 73 85 74 / 50 50 40 10
STT 83 73 83 72 / 50 50 20 10

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
421 AM AST Sat Feb 13 2021

.SYNOPSIS...

Generally, fair weather will prevail across the area, with
occasional patches of low-level moisture pooling into the region.
The low-level moisture will cause some isolated to scattered showers
to develop and produce light rainfall amounts. A surface high
pressure north of the area will continue to promote brisk
easterly trade winds and choppy to rough maine condtions over the
next several days.

&&

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

A building surface high pressure across the central Atlantic will
cause an easterly breeze for the next few days. Winds are expected
to be at 10 to 20 mph especially during the daytime hours, with
lighter winds late in the night. Mid level high pressure will
persist over the next few days as well, which will cause subsidence
and any rain that develops should be shallow. That said, with the
exception of this morning, very little rain is expected on the rest
of the short term period. There is a patch of moisture currently
passing through the local area, bringing scattered showers to the
local waters, USVI and eastern PR, but the showers are brief and are
not causing much accumulations. This patch of moisture is expected
to leave the area early this afternoon, and drier air will move in
by the mid afternoon hours.

This air mass of drier air will have precipitable water values of an
inch or less. The forecast soundings show a rather stable atmosphere
starting late Saturday afternoon through early Monday, then a quick
patch or moisture moves in on Monday afternoon, causing an increase
in shower activity, but again, it should be quick passing and brief.
The forecast therefore is for scattered showers this morning,
followed by improving conditions. Isolated to no rain on Sunday and
Monday morning, then isolated to scattered brief showers early on
Monday afternoon.

&&

.LONG TERM...Tuesday through Sunday...

The long-term period will remain relatively tranquil due to
ridging at the surface and aloft stabilizing the atmosphere and
keeping the atmospheric column somewhat dry. The drier conditions
are supported by the GFS and ECMWF models. Occasional patches of
moisture will stream over the region and produce brief, shallow
convection. Moisture will remain confined between the 1000 to 700
mb leve. The devoid moisture in the mid to upper-levels of the
atmosphere will inhibit the development of organized convection
and significant rainfall.

Sunday, recent guidance shows heights falling across the Caribbean
as a TUTT low moves into the regional waters. The TUTT will cause
500 MB temperatures cooling to -9 to -8 degrees celsius through
late Tuesday night. Typically, upper-level instability would
support development of deep convection but, meager moisture
content and ridging at the surface and aloft will off set the the
upper-level instability over the region thus leading to
development of shallow convection. In the middle of the week
through the weekend, the moisture content will increase each day
and slowly moisten the mid- levels of the atmosphere across the
Caribbean as patches of low- level moisture advects over the
region more frequently. Forecast confidence is medium.

&&

.AVIATION...

SHRA across the area is causing VCSH across many of the local
terminals this morning. After 13/14Z weather is expected to
gradually improve and only ISOL SHRA is forecast. No prevailing CIG
expected but possible briefly as SHRA passes by in the morning.
Winds will increase to around 15 knots, gusting to around 25 knots
after 13/13Z. Winds will be from the east, but with sea breeze
variations.

&&

.MARINE...

Choppy to rough wind driven seas will prevail across most of the
regional waters through early next week. Easterly trade winds will
range from 15 to 20 kts with higher gusts. Small Craft Advisories
are in effect for the offshore waters of the Atlantic, Caribbean,
and the eastern waters of the USVI due to seas up to 8 feet. Seas
across the nearshore waters are up to 6 feet. There is a high
risk of rip currents for the northern beaches of PR and Culebra
through at least Sunday afternoon.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
441 AM AST Sun Feb 14 2021

.SYNOPSIS...

Fair weather will prevail across the area over the next several days
with occasional patches of low-level moisture advecting across the
local islands. Low-level moisture will induce a few isolated to
scattered showers and light rainfall amounts. A trough north of
Puerto Rico will cause a slight uptick in showers during the middle
of the week before lifting northeast of Puerto Rico. A surface high
will continue to promote brisk easterly trade winds and choppy to
rough maine condtions through Wednesday.

&&

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

A surface high pressure across the central Atlantic will cause an
easterly breeze for the next few days. Winds are expected to be at
10 to 20 mph, especially during the daytime hours, with lighter
winds late in the night. Mid level high pressure will persist over
the next few days as well, which will cause subsidence and any rain
that develops should be shallow. That said, a tilted upper level
trough appears to show signs of developing starting on Tuesday, but
we will be in the subsident side of its axis by Tuesday night.
Mainly dry air is expected over the next few days, with brief
patches of moisture. Therefore fair weather is to be expected most
of the time, but brief isolated to scattered showers will move in
from time to time, mainly affecting the local waters, USVI, and
eastern PR.

This air mass of drier air will have precipitable water values of an
inch or less, with the brief patches of moisture bumping
precipitable water to around 1.5 inches, but again those patches of
moisture will be brief. The forecast soundings show a rather stable
atmosphere through Tuesday. The forecast therefore is for fair
weather with brief isolated showers this morning, followed by
isolated to scattered showers this afternoon. A similar pattern can
be expected on Monday.


&&

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

The global models are in agreement with the long-term period
relatively tranquil due to the surface and mid-level ridge anchoring
themselves across the area. The ridging will keep the mid-levels of
the atmosphere mostly stable and dry. Brisk easterly winds will push
patches of moisture occasionally over the region and produce brief,
shallow convection. Global models continue to keep the moisture
confined between the 1000 to 700 mb levels of the atmosphere. The
devoid moisture in the mid to upper-levels of the atmosphere will
inhibit the development of organized convection and significant
rainfall.

The GFS and ECMWF keep 500 mb heights around -7 to -9 throughout the
period due to a weak trough developing north of Puerto Rico. The
trough will lift to the northeast of Puerto Rico Tuesday afternoon.
Meager moisture content and ridging at the surface and aloft will
off set the the upper-level instability over the region thus leading
to development of shallow convection. Precipitable water will
remain remain above 1.0 inches throughout the long- term period
due to the trough northeast of Puerto Rico and the easterly
tradewinds advecting moisture into the area. The increase in low-
level moisture will increase rain chances across the region late
in the period. Forecast confidence is medium.

&&

.AVIATION...

VFR conds expected for the next 24 hours with fair weather. VCSH is
possible at TJBQ after 14/18Z. Winds will increase to around 15
knots, gusting to around 25 knots after 14/14Z. Winds will be from
the east, but with sea breeze variations.

&&

.MARINE...

Choppy to rough wind driven seas will prevail across most of the
regional waters through Wednesday. Easterly trade winds will
range from 15 to 20 kts with higher gusts. Small Craft Advisories
are in effect for most of the regional and local waters due to
seas being up to 8 feet. There is a high risk of rip currents for
the northern beaches of PR, Culebra, USVI, Saint Thomas and Saint
John.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
430 AM AST Mon Feb 15 2021

.SYNOPSIS...Surface high pressure across the central Atlantic will
dominate the local wind flow for much of the workweek, causing
moderate to fresh easterly breezes through at least Thursday. Mid
level high pressure will also remain in place to the NNE of the
local islands through the week, promoting some stability most of
the week. However, in the upper levels, there is a weak upper
trough developing, which is tilted and may cause some instability
on Wednesday, especially when it coincides with an increase in
moisture expected on Wednesday. That said, by Thursday we should
be on the west or subsident side of the axis with drier air. The
marine conditions will remain choppy to hazardous for most of the
workweek.

&&

.SHORT TERM...Today through Wednesday...
A mid-level ridge over the region will promote relatively fair and
stable weather conditions across the local islands; by pumping dry
sinking air through the atmospheric layer. The GFS keeps the deepest
moisture confined between 1000 to 800 mb levels.

The drier air will inhibit the development of organized convection
but, shallow convection will induce isolated to scattered showers
during the early morning, afternoon, and evening hours. The moisture
will be carried by the easterly trade winds through the short-term
period. The easterly trades are a result of a tenacious surface high
pressure that is positioned north of the area.

Wednesday, the GFS shows precipitable water increasing to 1.5 inches
during the morning hours as a wind surge and modest low-level
moisture pushes over the region during the day resulting in a slight
up-tick in convection during the day.

&&

.LONG TERM...Thursday through Tuesday...
The surface high pressure across the central Atlantic will
dominate for the latter part of the week, only to be replaced by
another surface high pressure that will move into the western
Atlantic, keeping moderate to fresh easterly breezes through the
forecast period. The mid levels will remain stable with a high
pressure persisting over the area late in the week, but a weaker
high pressure will be present by next weekend. The upper levels
will also be mainly stable. While a weak upper trough and low
could be present over the area, the latest guidance suggests that
we will be in the subsident side of it late this week and into the
weekend. Patches of moisture will move through, which will cause
brief isolated to scattered showers across the area, but no
significant convection would be expected with what we can see from
the latest guidance.

&&

.AVIATION...Prevailing VFR. VCSH with brief -SHRA across PR eastern and
northern terminals and terminals east through 15/15Z. SHRA/-SHRA possible
across most of PR terminal sites and ovr the regional by 15/18Z.
SFC wnds fm E 15-20 kts, gusting to around 25 kts by 15/15Z, with
sea breeze variations.

&&

.MARINE...Small craft advisories continue in effect through
Thursday, as seas up to 7 or 8 feet are expected across the
offshore waters, waters just east of the USVI, and the local
passages. The latest buoy observations in the nearshore waters
indicate that the wave heights have been generally between 5 and 6
feet, but once the winds increase during the day, the local seas
are expected to increase occasionally up to 7 feet across the
coastal Atlantic waters, while the offshore waters could see up to
8 feet. Winds will be up to 22 knots across most of the local
waters through at least Wednesday. There is also a high risk of
rip currents for many of the local beaches, while many more will
have a moderate risk of rip currents. Please see the local Surf
Zone products for details on specific beaches.


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
413 AM AST Tue Feb 16 2021

.SYNOPSIS...Surface high pressure across the central Atlantic will
continue to dominate the local wind flow for the rest of the
workweek, causing moderate to fresh easterly breezes. Mid level
high pressure will also remain in place to the NNE of the local
islands, promoting stability most of the week. In the upper
levels, there is a weak upper trough developing, which is tilted
and may cause some instability on Wednesday, as it coincides with
an increase in moisture. That said, by Thursday we should be on
the subsident side of the axis with drier air moving in. The
marine conditions will remain choppy to hazardous for the rest of
the workweek.

&&

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

The surface and mid-level ridge north of the area will promote
relatively fair and stable weather conditions across the local
islands today. Moisture content will slowly decrease the remainder
of the day; the GFS has the precipitable water falling to 0.60
inches late tonight, which is greater than two standard deviations
below normal.

GOES-16 water vapor shows moisture advecting well to the north and
south of Puerto Rico with a drier air mass moving over the island.
Brisk easterly trade winds could advect meager moisture across
eastern and northern areas of Puerto Rico this morning, and local
and diurnal effects could possibly induce a few isolated to
scattered showers this afternoon. Showers that develop will be short-
lived due to the lack of sufficient moisture and sinking air in the
mid-levels of the atmosphere.

Wednesday, an upper-level trough and wind surge will cause moisture
content to increase rapidly across the region. The GFS has
precipitable water peaking to 1.5 to 1.6 during the afternoon. The
global models advects a robust patch of moisture across Puerto Rico
during the afternoon. The moisture coupled with local effects will
induce isolated to scattered showers across portions of northern,
interior, and western Puerto Rico during the afternoon. The shower
activity could cause minor flooding and ponding of water on
roadways.

Thursday, isolated to scattered showers are expected to develop
across the region due to residual moisture and local and diurnal
effects.

&&

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

Mainly fair weather is to be expected in the long term period with
the exception of a few instances, namely on Friday as an upper
trough provides some instability; and on Sunday into Monday when a
deeper than normal moisture band moves through, mainly affecting
areas near the USVI and eastern PR.

The surface high pressure across the central Atlantic will
dominate for the latter part of the week, only to be replaced by
another surface high pressure that will move into the western
Atlantic on Sunday, keeping moderate to fresh easterly breezes
through the long term forecast period. The mid levels will remain
stable with a high pressure persisting over the area on Friday,
but a weaker high pressure will be present by the weekend. That
said, a weak mid level trough could develop to the NE of the local
area early next week, but at this time it looks like there will be
no instability over the local area associated with that trough.
The upper levels will also be mainly stable, with the exception of
a weak upper trough and low that could be present over the area
on Friday. However, the latest guidance suggests that there will
be only modest impacts, but a patch of moisture is expected to
move in on Friday, which will combine with the local effects and
perhaps the upper low, to cause some convection across western PR
in the afternoon. Starting on Saturday afternoon and through the
rest of the long term period, in the upper levels we will have
zonal flow or under a ridge, promoting stability. However, a
relatively deep moisture patch could approach the islands on
Sunday into Monday, causing precipitable water to increase to as
much 1.80 inches or so. This could bring slightly more
significant rain to the USVI and eastern PR. Otherwise, the
typical and expected patches of moisture during most of the long
term period will bring isolated to scattered brief showers to
eastern PR and the USVI.

&&

.AVIATION...VRF conds are expected to prevail across all terminal
sites through 17/06Z. A brief -ISO SHRA could move over the eastern
terminal through the 16/22Z. Low level winds from the east up to
20 mph with higher gusts possible.

&&

.MARINE...Wind driven hazardous seas will continue until the end
of the workweek. Therefore there is a Small Craft Advisory in
effect for the offshore Atlantic and Caribbean waters, as well as
for the local passages and the waters east of PR near the
northern USVI. Seas up to 8 feet and easterly winds up to 20 knots
are expected, with higher gusts at times. There is a high risk of
rip currents for the northern beaches of PR, Culebra,
northwestern St. Thomas and eastern St. Croix. Please refer to the
latest Coastal Hazard Message (CFWSJU), Surf Zone Forecast
(SRFSJU) and Marine Weather Message (MWWSJU) for detailed
information.


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
443 AM AST Wed Feb 17 2021

.SYNOPSIS...Surface high pressure across the central Atlantic will
continue to dominate the local wind flow for the rest of the
workweek, causing moderate to fresh easterly breezes, but will be
replaced by another surface high pressure late in the weekend.
Mid level high pressure will also remain in place to the NNE of
the local islands, promoting stability most of the week. In the
upper levels, there is a weak upper trough developing, which is
tilted and may cause some instability today, as it coincides with
an increase in moisture, and thus an increase in shower activity
is expected today. On Thursday we should be on the subsident side
of the trough axis with drier air moving in in the morning hours.
The marine conditions will remain choppy to hazardous for the
rest of the workweek.

&&

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

A surface ridge and mid-level ridge will continue to influence the
local weather by promoting general fair and stable weather
conditions through the short-term period. The surface ridge will
create strong easterly trade winds which will occasionally advect
patches of moisture into the region. The GFS shows moisture
fluctuating between below-normal to near-normal through Friday.

The ridging will continue to support a relatively vigorous trade
wind cap that will continue to suppress the development of deep
convection due to drier air in the mid-levels of the atmosphere.
Nevertheless, the shallow moisture will induce isolated to scattered
showers that could cause ponding of water on roadways and minor
flooding.

The best rain chances during the period will be this afternoon into
early thursday morning when east to northeast winds drag patches of
moisture across the northern and eastern areas of Puerto Rico this
morning. The moisture will continue to advect across the interior
and the western areas of the island during the afternoon during
peak heating. Global models continue to advect meager moisture
periodically over the islands through Friday. The moisture will
induce shallow convection across the local water and islands.

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

Mainly fair weather is to be expected in the long term period with
the exception of a few instances, particularly on Sunday night into
Monday when a deeper than normal moisture band moves through,
affecting areas near the USVI and eastern PR.

The surface high pressure across the central Atlantic will
still dominate the local wind flow this weekend, but will start
to be replaced by another surface high pressure that will move
into the western Atlantic by Monday. These surface high pressure
systems will keep a moderate to fresh easterly breezes through the
long term forecast period. Latest guidance still suggests that
the mid levels will remain relatively stable stable with a weak
high pressure prevailing over the area. That said, a weak mid
level trough could develop to the NE of the local area early next
week, but it looks like there will be no real impact on stability
over the local area. The upper levels will also be mainly stable
for most of the long term period. A weak upper trough could be
present over the local area on Saturday. This upper trough will
coincide with a patch of moisture, which will bring rain to the
USVI and eastern PR in the morning, then some convection across
western PR in the afternoon. Starting on Sunday and through the
rest of the long term period, in the upper levels we will have
zonal flow or under a ridge, promoting stability.

A relatively deep moisture patch could approach the islands late
Sunday into Monday, causing precipitable water to increase to as
much 1.70 inches or so. This could bring slightly more significant
rain to the USVI and eastern PR on Monday morning. Otherwise, the
typical and expected patches of moisture during most of the long
term period will bring isolated to scattered brief showers to
eastern PR and the USVI.


&&

.AVIATION...Iso/SCT SHRA will continue to affect the local waters and islands
through 17/22z. SCT-BKN CIGS from FL030-FL050 through 17/22Z. Sfc
winds from the east to northeast up to 12 kts through 17/14Z
increasing to 15 to 20 kts with higher gusts by 17/15Z.

&&

.MARINE...Wind driven hazardous seas will continue through the
end of the workweek. A Small Craft Advisory continues in effect
for most of the local waters. Seas up to 8 feet and easterly
winds up to 23 knots are expected, with higher gusts at times.
There is a high risk of rip currents for the northern beaches of
PR, Culebra, northwestern St. Thomas and eastern St. Croix today,
with SE PR and Vieques having a nigh risk of rip currents starting
this evening. Please refer to the latest Coastal Hazard Message
(CFWSJU), Surf Zone Forecast (SRFSJU) and Marine Weather Message
(MWWSJU) for detailed information.


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
424 AM AST Thu Feb 18 2021

.SYNOPSIS...

Breezy winds will continue due to strong high pressure to our
north. These winds will produce hazardous seas for the next
several days, with choppy yet calmer seas for the weekend. Drier
air is moving in, so calmer weather with some isolated shower
activity can be expected for the next few days. Enhanced moisture
can be expected for Sunday through Tuesday.

&&

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

A band of trade wind moisture along a low level convergence zone
will continue to sink further southwards across the islands and
local waters during the rest of the morning hours, while a strong
low to mid level high pressure ridge will hold north and east of
the region through the end of the work week. The prevailing east
northeast winds are then expected to become more easterly by
Saturday along with diminishing trade winds, as the local pressure
gradient relaxes in response to the Atlantic high pressure
shifting farther north and east into the central Atlantic. Brisk
trade winds and overall breezy conditions will therefore persist
at least through Friday then gradually taper off by Saturday.

A mid to upper level trough east of the region and extending
across the northern Leewards will linger across the northeastern
Caribbean today, with an area of low pressure forecast to
eventually cut off and shift westwards across the region late
Friday into Saturday. In the meantime, a strong high pressure
ridge will persist aloft and just west of the area to maintain
fairly dry and stable conditions. In the low levels, high pressure
ridge will remain the dominant weather feature and thus maintain
a fairly tight local pressure gradient. This will result in
moderate to strong easterly trade winds across the forecast area
at least until late Friday night or early Saturday. Consequently,
expect the windy to breezy conditions to persist across the area
through Friday, with a gradual diminishing of the easterly winds
by Saturday as the surface high pressure relaxes north of the
region.

The present and expected weather pattern will continue to bring
frequent patches of shallow moisture across the region along with
periods of quick passing showers and accompanying wind gust between
25-30 mph through Friday. However most of the shower activity should
be during the late evening and early morning hours, followed by a
mixture of sunshine and clouds with lesser showers expected during
the afternoon hours. Afternoon showers should be more in the form of
localized streamers and of short duration with no significant
rainfall accumulations anticipated.

By Saturday expect the overnight and early morning passing showers
to be less frequent as the trade winds weaken and moisture transport
erodes, along with the mid to upper trough becoming cutoff and
shifting westward just south of the region. Although lesser moisture
transport and shower activity is forecast for Saturday, still expect
some of the passing showers to be enhanced in some areas over the
coastal waters due to the proximity of this weak upper level
feature. So far no significant or widespread rainfall accumulations
are forecast during the period.

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

High pressure at low to mid levels will continue moving eastward for
Sunday. This will weaken pressure gradients at the surface, and
winds will slow down briefly. A cold front is expected to approach
the region for Sunday, but stall out before arriving. However,
moisture convergence ahead of the front will produce scattered
showers across the region for Sunday through Tuesday. The low
pressure trough associated with the cold front will produce fairly
cold temperatures at mid-levels, thus helping to increase
instability. This will help to produce stronger showers and could
lead to some water ponding over roadways. The best moisture at this
point looks to arrive late Sunday and into Monday. High pressure
will once again build back to our north on Monday, resulting in
fairly breezy winds once again across the region for Monday and
Tuesday.

Higher pressure and warmer temperatures aloft will build back in for
the second half of the work-week. At lower levels, drier air will
move in from the east, resulting in calmer weather. Winds will be at
near normal to slightly elevated through the rest of the week. Weak
patches of moisture will move in from time to time, resulting in
isolated to scattered showers.

&&

.AVIATION...

VFR conds at all terminals, but brisk easterly trade
winds will bring -SHRA/SHRA with SCT-BKN clds lyrs nr FL025...FL040
ovr islands and en route between all local terminals. Brief MVFR
conds and gusty wnds 20-25 kts with passing SHRA til 18/14Z with Mtn
Top Obscr ovr Ern PR due to low cloud lyrs and -SHRA. Sfc wnds 10-15
kts bcmg 15-20 kts with gusts to 25-30 kts aft 18/14Z.

&&

.MARINE...

Strong high pressure to our north will continue to produce fresh
to strong easterly winds for the next few days. This will result
in seas of up to 10 feet, particularly for the offshore Atlantic
waters. Seas are expected to subside for the weekend, though
remain choppy. Then more wind will increase seas for the next
workweek.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
417 AM AST Fri Feb 19 2021

.SYNOPSIS...

Winds and seas remain elevated, though conditions are calming down
as we head towards the weekend. Small Craft Advisories will expire
tonight for all the local waters. Passing moderate showers are
expected the next few days, with the next best chance for heavier
rainfall forecasted for Sunday and Monday. Later next week, more
seasonal and drier weather will prevail.

&&

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

Generally fair weather conditions will persist today and into early
Saturday with only occasional shallow patches of low level moisture
expected to cross the region from time to time. Moisture advection
will be limited in the low levels and overall dry and stable
conditions aloft are expected to continue, as mid level ridging will
hold at least into early Saturday. However, an upper level low is
still forecast to cutoff and slide southwestward across the region
later today into the weekend. This will create a gradual erosion of
the upper level ridge and therefore favor a better chance for shower
development across the islands late Saturday and on Sunday. In the
meantime...Isolated to scattered afternoon showers will remain
possible under a more typical weather pattern for today.

Breezy conditions will persist as the strong surface high will
remain anchored across the west and central Atlantic today. During
the short term period, the Atlantic surface ridge is to slowly shift
eastwards while maintaining its hold across the region and therefore
dominating the local pattern. This will promote moderate to locally
strong easterly trade winds, with breezy conditions especially along
the coastal areas and across the regional waters at least for today
and into early Saturday.

The tradewinds are forecast to diminish across the region as the
Atlantic high will lift north and east of the region. This will
allow the local pressure gradient to relax supporting a more typical
weather pattern with less frequent periods of early morning trade
wind showers. A mixture of sunshine and clouds will follow during
the daytime. By Sunday the prevailing easterly winds are forecast to
become more northeasterly and slightly increase once again, as a
surface high pressure ridge will build across the west and southwest
Atlantic.

For the weekend, recent model guidance suggests a gradual weakening
of the mid to upper level ridge as the aformentioned cutoff low
shifts westward across the area. This should erode the trade wind
cap inversion and favor a better chance for convective development
by Sunday. By then, sufficient low level moisture convergence is
forecast across the area and this will increase the chance for early
morning shower activity along the north and east coastal areas of
the islands, followed by scattered afternoon convection over parts
of the interior and west sections of Puerto Rico including parts of
the San Juan metro area. The U.S. Virgin islands will also
experience periods of passing showers during the morning hours,
followed by lesser shower activity during the afternoon.

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

Monday will be the most active day during the long term period, as
somewhat deeper moisture, coupled with decent instability, will act
to produce scattered moderate to heavy showers across the region. On
Monday, a mid-level trough will be to our east and moving eastward
away from us, yet cooler air aloft will still be with us for Monday
and somewhat for Tuesday. This cooler air will help to enhance
shower activity for Monday especially. Moisture moving in from the
east and enhanced by the instability will be with us for Monday,
and less so for Tuesday. Finally, as high surface pressure
reestablishes itself to our north for Monday, winds will once
again pick up to around 10 to 20 mph with higher gusts. Thus
showers will move along quite quickly and reduce their impact. The
wettest period for Monday will likely be in the morning hours, as
that is when models suggest the best moisture will be in the
area.

Heading into the middle of the week, a more typical weather pattern
is expected to prevail. Drier air with patches of moisture moving in
from the east will produce isolated to scattered weak showers from
time to time. High pressure will establish itself just to our west
at mid to upper levels, and this will produce stable and dry
conditions. Thus drier than normal conditions can be expected for
Wednesday and through the rest of the week, as no fronts or waves
are expected.

&&

.AVIATION...

VFR conds thru the fcst prd. SCT lyrs FL025...FL050. Sfc wnds fm
E 10-15 kts,incr to 15-20 kt with hir gusts aft 19/14z. Low level
winds fm E 20-25 kts BLO FL250. No sig operational wx impacts
attm.

&&

.MARINE...

Though still hazardous, seas have calmed down a bit since yesterday.
Winds across the region are also slowing down, though still remain
elevated from average levels. Winds and seas will continue to relax,
and will be below hazardous criteria for the weekend. For the
beginning of the workweek, winds will pick up again and seas will
also become hazardous as a result. Though Monday and Tuesday will
see the highest seas, choppy to hazardous conditions will last
most of next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 73 85 73 / 40 30 30 40
STT 84 75 83 75 / 40 50 50 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
347 AM AST Sat Feb 20 2021

.SYNOPSIS...
Moderate trade winds will continue across the region today, as
the broad surface high pressure ridge across the west and central
Atlantic slowly shifts eastward while relaxing the local pressure
gradient. In doing so, an east southeast wind flow will persist
across the area resulting in the transport of occasional patches
of shallow trade wind clouds and embedded showers across the local
waters and parts of the islands from time to time. Overall fair
weather is forecast for most areas, with isolated to scattered
afternoon showers in a typical pattern. On Sunday and Monday, an
increase in shower activity is expected, as moisture increases and
conditions aloft become marginally unstable.

&&

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

Currently high pressure at all levels of the atmosphere is moving
eastward away from the region. This will result in less stable and
less windy conditions for today and tomorrow. A weak cut-off low
currently resides over the region at upper levels, with its
associated cold air leading to somewhat unstable conditions that
will help enhance shower activity this weekend. A trough of low
pressure passing to our north at low to mid-levels is finally
weakening the local pressure gradient, so winds should be at near
normal intensities for this weekend.

Forecast models suggest some patches of moisture will move in today
from the southeast, and impact us throughout the day today. Given
the east-southeasterly flow, the best chance for showers will be
over western and northwestern Puerto Rico this afternoon. A few
factors will limit the impact of these showers. First, very dry air
will be present aloft despite the shallow patches of moisture moving
in. Second, though winds near the surface are relaxing, the winds
that steer the showers will still be moving at around 20 kts. This
will result in fast moving showers. Still, ponding of water over
roadways and low-lying areas is possible.

Better moisture is expected for tomorrow, though mid to upper levels
will still remain very dry. The atmosphere will be at its most
unstable for the short term period as well, so the greater moisture
and greater instability should lead to some decent shower activity
from Sunday afternoon to Monday afternoon. Thus showers are
expected for western Puerto Rico in the afternoon, and for eastern
Puerto Rico and the USVI overnight into Monday. By Monday afternoon,
winds will be out of the east-northeast so showers will be likely
for western and southwestern Puerto Rico in the afternoon. Once
again, ponding water over roadways and low-lying areas is possible
under the heaviest and most persistent showers.

.LONG TERM...Tuesday through Sunday...

A gradual erosion of moisture is forecast for Tuesday and at
least through Wednesday as high surface pressure reestablishes
itself north and east of the region with the tradewinds to once
again pick up to 15 to 20 mph with occasionally higher gusts.
Thus, expect shower activity to quickly move across the islands
and coastal waters resulting in minimal rainfall accumulations and
weather impacts each day.

By the latter part of the week, a seasonal weather pattern is
expected to prevail. A drier airmass with occasional patches of
tradewind moisture moving in and out of the region from the east
will produce isolated to scattered overnight and morning showers
from time to time. This will be followed by lesser activity
during the daytime except for the west and northwest sections of
Puerto Rico, where scattered afternoon showers will remain
possible. In addition, a surface high pressure ridge will again
reestablish itself just to our west at mid to upper levels, and
this will promote overall dry and stable conditions. Thus drier
than normal conditions can be expected from Thursday and into the
weekend. However, expect the easterly trade winds to increase once
again as the Atlantic surface high pressure ridge will build north
of the region resulting in a tightening of the local pressure gradient
and consequently breezy conditions across the area along with choppy
wind driven seas for the rest of the period.

&&

.AVIATION...Mostly VFR conds expected during prd. VCSH possible for E.
PR and USVI this morning. SHRA expected for NW PR in afternoon,
including TJBQ and possibly TJMZ. Winds will continue from the
east around 5 to 12 kts through 20/13z, and are forecast to
increase between 10 and 20 kt with higher gusts through 20/22z.

&&

.MARINE...Marine conditions have continued to improve overnight, with
winds gradually diminishing and seas subsiding across the coastal
waters. Small Craft Advisories will however continue for offshore
Atlantic waters until early this morning. Small craft operators
should exercise caution elsewhere as choppy conditions will persist.
High Risk of Rip Currents remains in place until early this morning
for some of the north facing beaches of Puerto Rico, Culebrita beach
and Cramer park beach in St Croix. Thereafter, there will be a moderate
risk of rip currents for most of the remaining beaches except for the
west coast beaches of Puerto Rico.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 73 82 73 / 30 40 50 50
STT 84 72 83 72 / 30 50 50 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
453 AM AST Sun Feb 21 2021

.SYNOPSIS...

Surface high pressure exiting the eastern seaboard of the U.S, and a
stalled frontal boundary across the west Atlantic along with another
ridge of high pressure over the north central Atlantic, will induce
light to moderate easterly winds across the region today. A mid-
level ridge will continue to hold in place through Monday, as a
broad upper level trough crosses the Atlantic just north of the
region. This overall scenario will aid in maintaining an advective
weather pattern where shallow moisture fragments trapped in the
low levels will be carried across the area by the dominant trade-
winds. Consequently, periods of enhanced showers can be expected
across the local waters and parts of the islands especially during
the morning and early afternoon. The easterly winds are to once
again increase from Monday onwards, as the high pressure ridge
builds north of the area.

&&

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

Currently a large trough at all levels of the atmosphere is passing
to our north, but is still impacting our weather in a few ways.
First of all, the troughing at low levels has weakened the local
pressure gradient, so surface wind speeds have slowed down to near
normal intensity. Second, fairly cold air aloft associated with the
troughing is extending down into our region, around -8 to -9 degrees
C, and has increased instability which would act to increase shower
vertical development and intensity. However, extremely dry air at
mid to upper levels is working against the cold temperatures, and
will be the dominant factor leading to weak light to moderate
showers. The best low-level moisture during the short term period
will be today into tonight. Thus we will see light to moderate
scattered to locally numerous showers for eastern Puerto Rico and
the USVI this morning. Later this afternoon, showers can be expected
over Puerto Rico, particularly western Puerto Rico. Given the dry
air, it is not likely that these showers will be very impactful, but
some ponding water is possible. Overnight, the moisture will still
be around somewhat, and with winds shifting to east-northeast,
scattered showers will impact the east and north coast of Puerto
Rico.

High pressure will begin to build once again across the region for
Monday and Tuesday, and fairly seasonal and tranquil weather
conditions will prevail. However, with high pressure building, once
again our pressure gradients will be enhanced so windy conditions
are likely, and this will impact seas as described in the marine
section. A few patches of moisture will impact the region for both
days, but shower activity will be limited due to the very dry air at
mid to upper levels, and less moisture at low-levels compared to
today.

.LONG TERM...
Seasonal and tranquil weather conditions will persist during most
of the period with the surface high pressure ridge to reestablish
across the Atlantic, along with a mid to upper level ridge which
will build also across the region. This will maintain overall dry
and stable conditions aloft and again a strengthening of the trade
wind cap inversion. However, as the surface pressure builds to
our north, the local pressure gradient will strengthen resulting
in breezy to windy conditions during the period. The local wind
flow will become east southeast Wednesday through Friday, then
become more east to northeast by Saturday and Sunday.

For the period, expect periods of quick passing clouds and shower
activity across the islands and coastal waters especially during
the overnight and early morning hours. This will result in
minimal rainfall accumulations and weather impacts each day with
no significant or widespread activity forecast for the period.

As suggested by recent model guidance, an overall seasonal
weather pattern is expected to prevail. A fairly dry airmass is
forecast with only occasional patches of tradewind moisture moving
in and out of the region. This will produce isolated to scattered
overnight and morning showers from time to time. This will be followed
by lesser activity during the daytime except for the west and northwest
sections of Puerto Rico, where scattered afternoon showers will remain
possible each day. In addition, expect the increasing trade winds to
continue to create choppy to rough wind driven seas and hazardous marine
conditions through most of the period.

&&

.AVIATION...Mostly VFR conds expected during the next day. VCSH likely
for E. PR and USVI this morning. In the afternoon, VCSH likely for
all terminals except TJPS. After 20/22z, -SHRA possible for TJSJ.
Winds will continue from the east around 5 to 12 kts through 20/13z,
and are forecast to increase to between 10 and 15 kts with higher
gusts through 20/22z.

&&

.MARINE...
Choppy conditions are expected to continue for much of the local
offshore waters and passages today and tonight due to gentle to
moderate easterly winds creating seas up to 6 feet. Small craft
operators are therefore urged to exercise caution . Marine conditions
are expected to deteriorate later tonight and into the upcoming
workweek due to as a northerly swell and increasing trade winds
with will affect the local waters. As a result, seas will increase
to small craft advisory criteria across the local waters, up to 7
or 8 feet with winds up to 20 knots. Please refer to the latest
Coastal Waters Forecast (CWFSJU) and Marine Weather Message
(MWWSJU) issued by NWS WFO San Juan for the latest and up to date
info.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 73 85 73 / 60 50 50 30
STT 83 72 84 73 / 50 50 50 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
512 AM AST Mon Feb 22 2021

.SYNOPSIS...A patchy weather pattern is expected to continue for
the next few days, with the best showers favoring eastern sections
of Puerto Rico and the US Virgin Islands during the morning hours and
western sections of Puerto Rico in the afternoon. Unfavorable
conditions aloft will not support significant rainfall
accumulations nor flooding with this activity. A series of
surface high pressure moving across the western Atlantic will
maintain breezy to windy conditions through the period. These
conditions, along with the arrival of a northerly swell, will
generate hazardous marine and coastal conditions starting this
afternoon.


&&

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

20 to 30 knot winds persist in the lower levels above the surface as
high pressure, now in the western Atlantic, reinforces the easterly
trade wind flow across the area. This high pressure will slide
across the Atlantic and end up centered just south of the Azores by
Wednesday. A weaker secondary high pressure moves off the eastern
coast of the United States on Tuesday night to a position north of
the local area by Wednesday afternoon. Patches of moisture will move
quickly through Puerto Rico and the U.S. Virgin Islands during the
period with the most notable dry intervals only on Tuesday night.
Showers are expected over the area with the best showers during the
morning hours on the eastern slopes of Puerto Rico and in western
Puerto Rico on Monday afternoon. As winds at 850 mb shift more east
southeasterly, showers will affect northwest Puerto Rico more during
Tuesday and Wednesday afternoons.

At upper levels, high pressure aloft remains across the western and
central Caribbean, while mid levels will see high pressure continue
over the local area. A weak developing low at 500 mb in the tropical
North Atlantic will bring some moisture to the area in the long term
period.

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

At the surface, a building high pressure with the tightening of
the local pressure gradient, will maintain breezy to windy
conditions during the period. The local wind flow will become east
southeast through Friday, then turning more east to northeast by
Saturday into early next week.

Under this flow, model guidance suggests that a patchy weather
pattern will dominate the long-term forecast period. This will
result from pockets of low-level moisture embedded in the trade
winds, generating periods of isolated to scattered shower activity
from time-to-time. While less frequent patches of moisture and
longer periods of clear skies are expected Thursday and Friday, an
increase in the extent and moisture content of these patches is
expected Friday night through Sunday, with highest impact
anticipated for portions of eastern Puerto Rico and the US Virgin
Islands. Even with model-estimated precipitable water rising to
1.5 inches and a slight weakening of the trade wind cap, lack of
forcing aloft (mid-upper level ridging) along with a strong
steering flow will not support significant rainfall accumulations
nor flooding with this activity. Conditions are expected to
improve by early next week.

&&

.AVIATION...VFR conds will prevail thru the fcst period. Brief
periods of MVFR conds are psbl in SHRA at TNCM/TKPK and TIST this
morning and in TJMZ this afternoon with some mtn topping. Some bkn
layers btwn 035-050 have also been noted from the USVI east.
Easterly sfc wnds incr to 15-20 kt with hir gusts aft 22/14z.
Maximum winds ESE 35-50 kt btwn FL520-550 and ENE 22-32 kt btwn
FL033-125 and N up to 30 kt nr FL320.


&&

.MARINE...The combination of increasing winds and the arrival of a
northerly swell will generate hazardous marine conditions starting
this afternoon. As a result, Small Craft Advisories will be in
effect for the offshore Atlantic and Caribbean waters, as well as
the Mona Passage this afternoon, extending to the Atlantic coastal
waters and the Anegada Passage on Tuesday. In the meantime, small
craft operators are urged to exercise caution due to choppy seas
up to 6 feet and winds up to 20 knots across most of the local
waters. A moderate risk of rip currents continues for most of the
local beaches today. The risk will elevate to high for beaches
along the north coast of Puerto Rico, Culebra and Saint Thomas
tonight into Tuesday.


&&

.FIRE WEATHER...Recent 10-hour fuel moisture values have dropped as
low as 8 percent, while KBDI values continue to rise, reaching
676 at Camp Santiago. While patches of low-level moisture
embedded in the trade winds will continue to stream across the
region from time-to-time, the chance for significant wetting
rains remains low, particularly for the south-central and
southeastern coastal sections where relative humidity is expected
to fall into the lower to mids 40s. The local wind flow is
forecast to peak at 15-20 mph with higher gusts and sea breeze
variations. That said, the combination of increasing winds, lack
of wetting rains and deteriorating soil and fuel conditions will
support elevated fire danger conditions today. As a result, Fire
Danger Statement has been issued for the southern coastal plains
of Puerto Rico.


&&

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

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
506 AM AST Tue Feb 23 2021

.SYNOPSIS...A patchy weather pattern is expected to continue for
the next few days, with the best showers favoring eastern sections
of Puerto Rico and the US Virgin Islands during the morning hours and
western sections of Puerto Rico in the afternoon. A series of
surface high pressure moving across the western Atlantic will
maintain breezy to windy conditions throughout the period,
carrying patches of moisture over the islands from time-to-time.
These windy conditions, along with a northerly swell, will
generate hazardous marine and coastal conditions.


&&

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

High pressure in the central Atlantic will move to just east of the
Azore Islands by Thursday. This will keep easterly winds at the
surface across the area at 15 to 20 knots with higher gusts. A
weaker secondary high pressure moves off the eastern coast of the
United States tonight to a position northeast of the local area in
the central Atlantic by Thursday afternoon. Patches of moisture will
move quickly through Puerto Rico and the U.S. Virgin Islands during
the period on the persistent trade wind flow with the most notable
dry intervals tonight and Wednesday night, but even these may be
punctuated by a patch of shower-bearing moisture. Showers are
expected over the area with the best showers during the morning
hours on the eastern slopes of Puerto Rico and in western Puerto
Rico this afternoon. As winds at 850 mb shift more east
southeasterly, showers will affect northwest Puerto Rico more during
this afternoon and Wednesday afternoon.

At upper levels, high pressure remains across the western and
central Caribbean and flow will be entirely west northwest to north
northwest. Beginning on Thursday a sharp trough will form over the
Leeward Islands and winds aloft over the local area will increase.
At mid levels high pressure continues over the local area.

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

The line of thought behind the long-term forecast hasn`t change
much in the last 24 hours. At the surface, a series of building
high pressures will tighten the local pressure gradient,
generating breezy to windy conditions during the period. The local
wind flow will remain from the east through Friday, turning more
from the east-northeast by Saturday and holding from that
direction through midweek next week with some weakening Tuesday
into Wednesday.

Under this flow, model guidance continues to suggest that a
patchy weather pattern will dominate the long-term forecast
period, varying in frequency every two to three days. This pattern
results from intermittent patches of drier air and low-level
moisture embedded in the trade winds. The latter will generate
periods of isolated to scattered shower activity from time-to-
time. While less frequent patches of moisture with longer periods
of relatively fair weather conditions and clearer skies are
expected on Friday, an increase in the extent and moisture
content of these patches is expected Friday evening through
Sunday, with highest impact anticipated for portions of eastern
Puerto Rico and the US Virgin Islands Friday night into Saturday.
Even with model- estimated precipitable water rising to 1.5
inches along with a slight weakening of the trade wind cap, lack
of forcing aloft (mid-upper level ridging) under a relatively strong
steering flow will not support significant rainfall accumulations
nor flooding with this activity. Conditions are expected to
improve by early next week with less frequent and weaker patches
of low-level moisture moving into the forecast area.


&&

.AVIATION...VFR conds will prevail thru the fcst period. Brief
periods of MVFR conds are psbl in SHRA at TNCM this morning and in
TJMZ/TJBQ this afternoon with some mtn topping. Some bkn layers btwn
035-050 have also been noted around Saint Croix. Easterly sfc wnds
incr to 15-20 kt with hir gusts aft 23/14z. Maximum winds WNW 25-40
kt btwn FL 250-330.


&&

.MARINE...Choppy to hazardous marine conditions with seas up to 8
feet will continue as a northerly swell continues to invade the
local waters along with easterly winds at 15-20 knots. As a
result, Small Craft Advisories remain in effect for most of the
local waters. Similar conditions are expected to hold throughout
the workweek and into the weekend as swells continue to invade the
local waters and winds remain at these speeds.

Along the coast, a high risk of rip currents will continue for
beaches along the north coast of Puerto Rico, Culebra and St
Thomas through at least Wednesday afternoon. The high risk may
extend through the rest of the workweek, and the risk may
upgrade from moderate to high for a few beaches of eastern St
Croix by Wednesday.


&&

.FIRE WEATHER...The forecast calls for conditions close to elevated
fire weather conditions today. Although lack of wetting rains
have allowed KBDI to remain within fire danger thresholds, the
timing of patches of low- level moisture streaming across the
region has been key in determining whether fire danger conditions
will be in place. Even when winds have reached fire danger
thresholds (=>15 mph) in recent days, both relative humidity and
10-hour fuel moisture values have remained slightly above
thresholds, failing to coincide with peak wind periods. That said,
a similar weather pattern is expected today, with a patch of low-
level moisture expected to affect the area through early this
afternoon. Although a Fire Danger Statement (RFD) will not be
issued at this time, close monitoring of fire danger conditions
will continue. If needed, an RFD will be issued later today.


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Wed Feb 24 2021

.SYNOPSIS...Although a few patches of low-level moisture will
stream across the region from time-to-time, extended periods under
the influence of drier air will maintain generally fair and
stable weather conditions during the next few days. If any, unfavorable
conditions aloft along with a persistent, fresh east- northeast
flow will suppress any chance for significant rainfall
accumulations from showers affecting the area. Hazardous marine
and coastal conditions remain as the main threat through the rest
of the workweek.


&&

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

High pressure dominates the eastern Atlantic. A very old cold front
associated with a low pressure in the northeast Atlantic lies south
of this high and is holding near 22 degrees north north of the
forecast area. A second cold front is advancing through the western
Atlantic from the west northwest. A weaker high pressure at the
surface is behind the latter front and just north of 30 degrees
north. This high pressure will continue moving east across the
central Atlantic ocean. This leaves the local area under persistent,
fresh easterly trade winds. Precipitable water values around or just
below 2 standard deviations will hover just under one inch, the
lowest values of the upcoming 7 days is expected to occur around
midday on Friday with 0.70 inches. Nevertheless, shallow patches of
moisture continue to move through on the easterly flow to produce
rapidly moving scattered showers that will leave slight
accumulations in favored areas, namely eastern Puerto Rico and
during the afternoons western Puerto Rico. Showers are expected to
diminish a little each day today through Friday. Only very minor and
isolated showers are expected in the U.S. Virgin Islands.

At upper levels, high pressure continues to wobble just north west
of Colombia, with persistent northwest flow. A moderate jet will
invade the area late Friday. Very dry air from high pressure at mid
levels will suppress all convection above 10 kft through the period.

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

The reasoning behind the long-term forecast analysis has somewhat
change, now calling for mainly fair and stable weather with less
frequent and intense patches of low-level moisture and extended
periods under the influence of drier air through most of the
long-term forecast period. At the surface, a building high
pressures will maintain breezy to windy conditions through Monday,
gradually weakening as the local pressure gradient relaxes
thereafter. The local wind flow will remain from the east-
northeast through most of the period, briefly favoring a more
easterly direction on Tuesday.

Under this general flow, model guidance continues to suggest that
patches of low-level moisture will stream across the region from
time-to-time. So far, the wettest patch (model-estimated
precipitable water around 1.50 inches) is forecast to reach the
local islands late Friday night into Saturday morning. Although
an increase in the potential for isolated to scattered shower
activity can be expected, unfavorable conditions aloft along with a
strong steering flow will not support significant rainfall
accumulations with this activity. Thereafter, the frequency and
intensity of such patches will diminish, with longer periods of
drier air affecting the area through midweek. This will result in
mainly fair and stable weather conditions with limited shower
activity, if any, across the forecast area.

&&

.AVIATION...VFR conds will prevail thru 25/06Z. Lcl streams of
shallow clds will form off many of the islands and where these cross
downstream some MVFR conds are psbl, but not expected to impact TAF
sites. Sct SHRA btwn 27/17-22Z in wrn PR with brief MVFR psbly
affecting TJMZ. Easterly sfc winds incr to 15-20 kt with hir gusts
aft 23/13z. Maximum winds NNW 30-40 kt btwn FL 260-420 increasing to
55 kt by 24/15Z. East winds up to 30 kt will also be found near
FL100.


&&

.MARINE...Choppy to hazardous marine conditions with seas up to 7
feet and winds up to 20 knots will continue across the offshore
Atlantic waters and Anegada Passage. As a result, Small Craft
Advisories remain in effect for these areas. Elsewhere, small
craft operators are urged to exercise caution due to seas up to 6
feet and winds up to 20 knots today. However, hazardous marine
conditions are expected to spread across most of the local waters,
with additional Small Craft Advisories in place starting on
Thursday morning.

Along the coast, a high risk of rip currents continues for
beaches along the north coast of Puerto Rico, Culebra and St
Thomas through at least Thursday afternoon. A moderate risk
continues for most of the remaining local beaches. These
conditions may hold through the end of the workweek into the
upcoming weekend.


&&

.FIRE WEATHER...A mass of drier air is expected to move into the
region today, limiting shower development and causing relative
humidity values to fall into the mid to upper 40s. Yesterday`s
10-hour fuel moisture fell as low as 8 percent, with KBDI
remaining well above 600 at Camp Santiago, Guanica and St Croix.
Since wetting rains are not anticipated, similar soils and fuels
conditions are expected. Winds are forecast to peak at 15-20 mph
with higher gusts and sea breeze variations. As a result, elevated
fire weather conditions can be expected across these areas today
and a Fire Danger Statement has been issued.


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
459 AM AST Thu Feb 25 2021

.SYNOPSIS...Drier than normal air mass will maintain fair and
stable weather conditions are expected during the next few days.
Upper level ridge will generate unfavorable conditions aloft,
limiting any chance for shower development. At the surface, a
persistent, fresh east- northeast flow will prevail through the
rest of the workweek into the weekend. Hazardous marine and
coastal conditions will remain as the main threat through the
weekend.


&&

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

At the surface high pressure dominates the eastern Atlantic and
extends towards Florida. A cold front is advancing through the
western Atlantic from the west northwest. Meanwhile low pressure has
deepened along the western coast of Colombia. This tightens the
local pressure gradient considerably and leaves us under persistent,
fresh easterly trade winds. Precipitable water values around or just
below 2 standard deviations will hover just under one inch, the
lowest values of the upcoming 7 days is expected to occur around
midday on Friday with 0.66 inches. Nevertheless, shallow patches of
moisture continue to move through on the easterly flow to produce
rapidly moving mostly isolated showers that will leave slight
accumulations in favored areas, namely eastern Puerto Rico and
during the afternoons western Puerto Rico. Showers are expected to
diminish today and Friday, but moisture spikes to over 1.5 inches
Friday evening and many more showers will be seen Friday evening
through Saturday morning. Only very minor and isolated showers are
expected in the U.S. Virgin Islands until Friday afternoon.

At upper levels, high pressure continues to wobble just northwest of
Colombia, with persistent northwest flow over Puerto Rico and the
U.S. Virgin Island. A moderate jet that invaded the local area
yesterday will fade tonight and Friday, but will return on Saturday
with winds in excess of 75 knots at 250 mb. Very dry air from high
pressure at mid levels will suppress all convection above 10 kft
through Friday, but showers will become a little deeper Friday night
through Saturday when the mid-level ridge angles off to our north
and the low pressure over the western tropical Atlantic edges toward
the Windward Islands.


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

The reasoning behind the long-term forecast analysis has not
changed much, suggesting mainly fair and stable weather
conditions across the region. At mid-to-upper levels, ridging
will maintain a generally strong trade wind cap and unfavorable
conditions for shower development. At the surface, a building high
pressures will maintain breezy to windy conditions through
Monday. Thereafter, winds are forecast to diminish while gradually
turning from the east southeast as the high pressure moves away
into the north central Atlantic and the local pressure gradient
relaxes. Under this flow, warmer temperatures can be expected
Wednesday onwards.

Although the overall weather pattern expected will only support
limited shower activity, there is a chance that cool advection
along with a prefrontal shear line will enhance showers moving
from the waters into northern sections of the local islands into
Sunday morning. Since deep convective development is not expected,
the occasional patch of low-level moisture will be the only
source of any relevant shower activity expected thereafter, with
model-estimated precipitable water reaching 1.40 inches at most.


&&

.AVIATION...VFR conds will prevail thru 26/06Z. Sct SHRA psbl btwn
25/17-22Z in wrn PR. Easterly sfc winds incr to 15-20 kt with hir
gusts aft 25/13z. Maximum winds NNW 50-65 kt btwn FL 335-375 . East
winds up to 25 kt will also be found near FL060.


&&

.MARINE...Choppy to hazardous marine conditions with seas up to 7
feet and winds up to 20 knots will continue across the offshore
Atlantic and Caribbean waters, as well as both Mona and Anegada
Passages through at least late Sunday night. Therefore, Small
Craft Advisories remain in effect for these areas. Elsewhere,
small craft operators are urged to exercise caution due to seas up
to 6 feet and winds up to 20 knots today. Although the forecast
now calls for a delay, hazardous marine conditions are still
expected to spread across other marine zones, with additional
Small Craft Advisories in place for the coastal waters starting on
Friday morning.

Along the coast, a high risk of rip currents continues for
beaches along the north coast of Puerto Rico and Culebra and St
Thomas through at least Sunday afternoon. A moderate risk of rip
currents is expected almost everywhere else. By this evening, the
moderate risk will elevate to high for beaches of eastern St
Croix.


&&

.FIRE WEATHER...Drier air along with unfavorable conditions aloft
will continue to dominate the local weather conditions today.
This will limit the chance for shower development and cause
relative humidity values to drop into the lower to mid 40s, with
the potential for even lower values across portions of the
southern coastal plains of Puerto Rico. Winds are forecast to peak
once again at 15-20 mph with gusts up to 30 mph and sea breeze
variations. Recent Fuel Moisture and KBDI reports continue to
support further drying, with values at 8 to 10 percent and 550 or
higher, respectively. Since wetting rains are not anticipated, the
combination of moderate to fresh winds along with persistent
drying conditions will support the spread of wild fires.
Therefore, a Fire Danger Statement has been issue for elevated
fire danger conditions expected across these areas today.

As drier air continues to moves into the area, there is a
potential for elevated to briefly critical fire danger conditions
during the next few days. If conditions warrant, Fire Danger
Statements or Red Flag Warnings will be issued accordingly.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 73 85 74 / 30 20 70 70
STT 85 74 85 74 / 20 30 60 60

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
437 AM AST Sat Feb 27 2021

.SYNOPSIS...
Strong winds will continue across the region due to a surface high
pressure to the north, with sustained winds 20 to 25 mph expected.
These winds are causing hazardous marine conditions through early
in the workweek. A group of showers is expected to move across the
islands later tonight, increasing the potential for passing
showers. In the long term, significant rainfall are not expected.

&&

.SHORT TERM...Today through Monday...
An easterly perturbation moved overnight across the region and
scattered shower activity was observed across much of northern and
eastern half of Puerto Rico. The Doppler radar estimated between
half to an inch of rain, mainly over the northeast to north
central coastal areas of the island. Gusty winds between 25-32 mph
were observed with the showers and minimum temperatures ranged
from the mid 60s across the higher elevations to the mid 70s
across coastal areas in general.

Strong east to northeast winds will continue across the region
through the short term period, in response to a building high
pressure at the surface to our north. This will promote a cool
advective pattern across the region, favoring shower development
along the northern and eastern sections of Puerto Rico and across
the U.S. Virgin Islands. Sustained winds between 20-25 mph and gusts
up to 35 mph are expected through the weekend, mainly across coastal
areas. Another easterly perturbation is expected to move tonight
into Sunday morning across the islands, enhancing once again shower
activity over northeastern and north central Puerto Rico. Across
west/southwest PR, overall fair weather conditions should prevail
with gusty winds through the period. By early Monday morning, the
remnants of a front are forecast to move quickly across the Atlantic
waters and across the islands, increasing shower activity once again
during the overnight hours and a drier air mass will follow during
the day and promote more stable conditions across the region.

.LONG TERM...Tuesday through Sunday...
A low to mid level high pressure will continue to be the dominant
feature as we extend into the long-term period. The global models
show an upper level trough developing over the central Atlantic,
but this feature won`t appear to have a strong influence over the
local islands. In fact, the mid-level ridge will maintain the
trade cap inversion through at least mid-week. Additionally, at
the lower levels precipitable water values are expected to range
from 0.8 to 1.3 inches of water. During this period, only shallow
moisture embedded in the trade winds will drag a few showers
across the islands, but without leaving significant rainfall
accumulation.

By the latter part of the workweek, a polar trough will exist the
eastern coast of the U.S., causing the ridge to flatten out. By
late Thursday into Friday, the forecast sounding from the GFS
shows a weaker trade wind cap. As a result, moisture a little
deeper will be able to enter the forecast area, increasing shower
activity a little bit. Moving into the weekend, another mid to
upper level ridge is expected to develop over the western
Caribbean, which once again will act to limit the potential for
vertical development across the islands. Precipitable water values
are expected to remain on the low side, with only occasional
patches of moisture being displaced from the east from time to
time.


&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, SHRA may cause brief
MVFR conds at TJSJ and TJBQ through the period and mtn top obscd
ovr eastern and north central PR. SCT/BKN cigs from FL040-FL090.
Surface winds from the east at 20-25 kt with higher gusts expected
through the weekend.


&&

.MARINE...
Hazardous marine conditions continue across most of the local
waters, except southwestern Puerto Rico, with building seas up to
10 feet. This is due to a strong surface high pressure that is
causing fresh to strong winds across the waters, 20 to 25 knots
and stronger gusts. These conditions are expected to continue
through early in the workweek. As a result, Small Craft Advisories
are in effect.

For the beaches, there is a High Rip Current Risk statement for
the the northern, eastern, and southeastern Coast of Puerto Rico,
as well as for Vieques, Culebra, and St. Thomas and St. Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 73 84 73 / 50 60 60 60
STT 85 73 84 73 / 40 50 50 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
413 AM AST Sun Feb 28 2021

.SYNOPSIS...
Windy conditions continue across the area, resulting in hazardous
seas through the first half of the workweek. No major rain events
are in the forecast through the next several days, but the trade
winds will carry some areas of showers across the area from time
to time.

&&

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

A surface high pressure over the southwestern Atlantic will continue
to promote strong east to northeast winds through at least Monday
morning. Sustained winds between 20-25 mph and gusts up to 35 mph
are expected through this period, mainly across the northern and
eastern coastal areas. Moderate trades are expected to return on
Tuesday. These winds will promote an advective pattern across the
region, and shower activity is expected mainly across the northern
and eastern sections of Puerto Rico and across the U.S. Virgin
Islands, mainly during the nights and early morning hours. Low-level
moisture and instability peaks between 03z-09z Monday, as the
remnants of a frontal boundary will move across the area. A drier
air mass will follow during the day on Monday as a mid-level ridge
builds from the west and strengthens the inversion layer, while an
upper-level trough lies northeast of the Leeward Islands. Therefore,
more stable conditions are expected. For Tuesday, fair weather
conditions should continue across the islands, however, another area
of trade wind showers is forecast to move from the northeast during
the overnight/early morning hours.

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

A relatively dry weather pattern is expected for the middle of the
workweek. At the low to mid-levels, a high pressure will be the
dominant feature. This will maintain a trade wind cap around 800
to 850 mb to at least Friday. The forecast soundings are showing
precipitable waters near 1.0 inch or less, hence very limited
shower activity is expected to prevail through this forecast
period. Some shallow patches of moisture may be advected across
the islands from time to time, resulting in a few passing showers.

At the surface, a high pressure will begin to migrate toward the
eastern Atlantic, while a cold front exists the eastern coast of
the United States. Although the cold front is not expected to
affect the islands, the wind flow is expected to shift from the
southeast by late Thursday and continuing into the weekend. This
will pull some moisture over the area, increasing somewhat the
chances of showers. In general, this shower activity should affect
the local waters, as well as the eastern half of Puerto Rico and
the U.S. Virgin Islands, while enhancing afternoon activity across
western Puerto Rico.

&&

.AVIATION...
Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, quick passing -SHRA may
cause brief MVFR conds at TJSJ/TJBQ/TIST/TISX through the period.
Surface winds from the east-northeast at 15-25 kt with higher gusts.

&&

.MARINE...
Fresh to strong winds, 20 to 25 knots, are causing hazardous
marine conditions, with seas up to 10 feet expected. These
conditions are expected to continue through early in the workweek.
As a result, Small Craft Advisories are in effect. For the
beaches, there is a high rip current risk for most of the coastal
areas across the islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 73 83 72 / 50 50 40 40
STT 85 73 85 72 / 50 50 20 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
501 AM AST Mon Mar 1 2021

.SYNOPSIS...Breezy conditions expected today. Surface and mid-
level high pressure systems will maintain drier conditions through
the end of the week. A trough will increase showers by the
upcoming weekend.


&&

.SHORT TERM...Today through Wednesday...
A surface high pressure located to the north of the region is
producing strong winds across the local waters and islands. This
system will generate an east-northeast wind flow at 15 to 20 mph,
with stronger gusts through late today and early tonight. Then, the
high pressure is expected to weaken, relaxing the pressure gradient
a bit, with a moderate steering flow continuing through the short-
term forecast period.

A drier air mass will continue to filter in, with precipitable water
values around 1.0 inch or less in the forecast for today and
tomorrow. This will act to inhibit any significant rainfall
development over the area. However, under a northeasterly wind flow,
advective showers may develop north of the area and move from time
to time over portions of northern and eastern Puerto Rico, as well
as across the U.S. Virgin Islands. By Wednesday, as the high
pressure migrates toward the eastern Atlantic Ocean, the wind flow
is expected to shift from the east-southeast. So far, the model
guidance are not suggesting any increase in moisture, but again,
some clouds carried by the trade winds may cause brief showers over
the islands.

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

A mid-level ridge will dominate the local weather conditions
through the end of the workweek. This will promote stable
conditions aloft and maintain the trade wind cap across the
region. Precipitable water content through this period will be
around 1 inch, and diurnally induced afternoon showers should
result in minor rainfall accumulations. A surface high pressure
will continue to move further away into the central-eastern
Atlantic, while a polar trough and associated surface front exits
the U.S. East Coast by Friday. The base of the trough and the
front are expected at this time to remain just north of the
region, however, a pre-frontal trough is expected to develop in a
southeasterly wind flow and move over the region on Saturday.
Pooling of moisture is expected through the weekend into early
next week. Precipitable water content is forecast to increase from
1.75-2.00 inches during this time. Therefore, expect wetter
conditions and the potential for urban and small stream flooding
will increase due to periods of moderate to locally heavy
rainfall. Drier conditions are expected by Tuesday.


&&

.AVIATION...Mainly VFR conditions expected through the forecast
period. Strong winds will continue, out of the E at 15 to 20
knots. A patch of clouds may affect the USVI and Leeward terminals
early in the period, which could cause VCSH and brief periods of
MVFR conditions due to lower ceilings and reduced VIS.


&&

.MARINE...Choppy and hazardous seas are expected to continue
through at least Tuesday across the regional waters and Small
Craft Advisories are in effect for most of the local waters and
passages. Breezy conditions will continue today with winds from
the east to northeast at 20-25 kts with gusts up to 30 kts in
trade wind showers. There is a high risk of rip currents for most
of the beaches with northern and eastern exposure across all the
islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 71 85 72 / 40 40 30 30
STT 85 72 84 73 / 30 30 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
352 AM AST Tue Mar 2 2021

.SYNOPSIS...Overall fair weather conditions are expected to
prevail through the end of the workweek. However, areas of low-
level clouds and light showers will move at times across the
islands. An induced surface trough is forecast to increase
moisture content and shower development between Friday into early
in the weekend. Trade winds are forecast decrease and turn more
from the southeast during the second part of the week.


&&

.SHORT TERM...Today through Thursday...
As the surface high pressure to the north of the islands continues
to weaken, the pressure gradient is gradually slacking off,
resulting in a decrease in sustained wind speed over the area. At
the mid levels, high pressure also dominates the western
Caribbean, which is resulting in a trade wind cap around 850 mb.
This will maintain moisture trapped in the lower levels of the
atmosphere. According to Total Precipitable Water from GOES-16, a
relatively dry air mass, with values around 0.9 inches, is
currently located over Puerto Rico and the U.S. Virgin Islands. In
fact, the forecast soundings and the latest model guidance are
not suggesting any significant increase in moisture over the
islands, meaning that rainfall should be very limited through the
next few days. Even with the low moisture content expected, trade
wind showers may still form and affect the eastern half of Puerto
Rico and the U.S. Virgin Islands, with additional showers
developing in the afternoon over western Puerto Rico, but none of
these showers are expected to be significant.

As the surface high pressure migrates toward the eastern Atlantic
and a cold front exits the eastern coast of the United States,
winds will begin to shift more from the east-southeast on
Wednesday and from the south-southeast on Thursday. In fact, the
southeasterly wind flow is expected to extend into the mid-layers
of the atmosphere. As a result, warmer temperatures are expected
by the end of the workweek, with possible high temperatures
reaching the upper 80s, especially across the coastal areas.

.LONG TERM...Friday through Wednesday...
The mid-level ridge over the region is forecast to weaken by
Friday, but it is expected to build and strengthen once again
over the central Atlantic. Meanwhile, an amplifying mid to upper
level trough over the western Atlantic will extend into the
northeastern Caribbean. A surface front is expected to remain well
north of the region, while an induced pre-frontal trough is
expected to develop just west of the local area, promoting a weak
and moist southerly wind flow on Friday and Saturday. Although
global models are not as aggressive as last night solutions,
precipitable water (PWAT) content is forecast to remain just above
climatology around 1.40 inches. Therefore, expect diurnally
induced afternoon showers to develop over the interior and
northern sections of PR, due to the light steering winds, slow
moving showers could lead to minor flooding.

On Sunday, trade winds are forecast to return to around 15-20 kts
and overall fair weather conditions are expected with afternoon
showers developing over western PR. For early next week, another
induced surface trough is forecast to develop over the local area
and increase shower development across the islands. PWAT content
is expected to continue above climatology at 1.40-1.50 inches
through midweek, favoring afternoon shower development over
western PR.


&&

.AVIATION...Mainly VFR conditions expected to prevail through the
forecast period. Surface Winds will be out of the ENE at 10 to 15
knots with stronger gusts. VCSH may occur over the Leeward and
U.S. Virgin Islands, as well as TJSJ early in the period, which
could cause brief periods of low ceilings.


&&

.MARINE...Choppy wind driven seas up to 8 feet will continue
through at least today across the regional waters. Small Craft
Advisories will expire later this afternoon. Seas will gradually
improve during the next few days across most of the local waters,
however, seas up to 6 feet are expected to continue mainly across
the Atlantic waters and passages. East to northeast winds up to 20
kts will prevail through Wednesday, thereafter, winds turn more
from the east to southeast at 10-15 kts. A 3-5 ft northerly swell
will move briefly across the Atlantic waters and passages between
Thursday afternoon and Friday.

There is high risk of rip currents today for the northern and
eastern beaches of PR, Culebra, St. Croix and northwestern beaches
of St. Thomas.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 82 72 85 72 / 30 40 40 30
STT 84 73 83 74 / 20 40 40 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
403 AM AST Wed Mar 3 2021

.SYNOPSIS...A drier air mass will continue through at least
Friday over the region. A few areas of low-level clouds and light
showers may move at times across the islands, but overall fair
weather conditions should prevail through the workweek. Moisture
increases over the region in a southeasterly wind flow by late
Friday into Saturday. Drier conditions are expected on Sunday and
moisture gradually increases early next week. Winds are forecast
to increase once again from the east to northeast during the
first part of next week.


&&

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

A mid to upper level ridge will continue to hold today over the
local area through early Thursday. This is causing a trade wind cap
around 850 mb, while the moisture content remains trapped under this
layer. At the surface, a generally dry air mass is evident on
satellite imagery and in the forecast soundings, with precipitable
water values around 1.0 inch or less. A few trade wind showers could
be advected into the eastern sections of Puerto Rico and over the
U.S. Virgin Islands during this period, but no significant rainfall
accumulation are expected due to the lack of mid and upper level
support.

As a polar trough and a cold front exit the eastern coast of the
United States later today and the surface high pressure moves toward
the eastern Atlantic, the wind flow will response by shifting more
from the east-southeast today, then more from the south-southeast
for the end of the workweek. Additionally, the trade wind cap will
gradually weaken, allowing deeper moisture to flow into the
region. So far, the model guidance are showing a moisture field
being pulled from the south by late Friday, increasing
precipitable water values to 1.2 to 1.4 inches. As a result,
shower activity is expected to increase by then over the islands.
The layer of southeasterly winds is expected to extend into the
mid-levels of the atmosphere, resulting in temperatures increasing
as well, with highs reaching the upper 80s, especially near the
coastal sections.


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

Polar trough and frontal boundary over the western Atlantic are
expected to remain just north of the region, while an induced
surface trough west of the area promotes a moist southeasterly
wind flow across the region on Saturday. Therefore, expect showers
to move across the USVI and east/southeast sections of PR during
the early morning hours, followed by periods of possible locally
heavy rainfall over the interior and northwestern PR. On Sunday,
trade winds are forecast to return to around 15-20 kts and
limit shower development during the afternoon hours over western
PR. Across the USVI, fair weather conditions should prevail and
normal to above normal temperatures are expected in general across
the islands.

For early next week, another induced surface trough is forecast
to develop to our northwest, and increase moisture content in
general across the local area on Monday. However, models suggest
today that the best areas of moisture are to remain over
Hispaniola, and a broad surface high pressure will move over the
western Atlantic...promoting a moderate to fresh northeast wind
flow across the islands through midweek. This should favor a cool
advective weather pattern, with trade wind showers moving over
the USVI and east/northeast sections of PR during the night/early
morning hours...followed by shallow convection developing during
the afternoon hours over west/southwestern PR.


&&

.AVIATION...Mainly VFR conditions expected to prevail through the forecast
period. Winds will be from the east at 10 to 15 knots, shifting from
the ESE around 03/15Z. VCSH are possible after 15Z for TJBQ, which
could result in brief MVFR conditions due to reduced VIS and low
ceilings.


&&

.MARINE...Small crafts should exercise caution due to seas up to 6
feet and east winds up to 20 knots across most of the regional
waters. There is a moderate risk of rip currents for all the
islands. A long period northerly swell will move briefly on
Thursday and Friday. Winds will gradually turn more from the east
to southeast later today and become light to moderate by the end
of the week.


&&

.FIRE WEATHER...There is an elevated fire danger for the southern
coastal plains of Puerto Rico today. Other areas across the
interior and western PR may see relative humidities in the low
40%s, but light afternoon showers are expected to develop this
afternoon across these areas.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 72 85 73 / 30 30 40 10
STT 83 74 84 74 / 30 20 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
422 AM AST Thu Mar 4 2021

.SYNOPSIS...Fair weather conditions due to a drier than normal air
mass will prevail through early Friday. Moisture will increase in
southeasterly flow later Friday through Saturday, resulting in an
increase in shower activity. Drier conditions expected for Sunday
before low-level moisture gradually increases through most of
next week. Winds are expected to increase as well by early next
week as another surface high pressure moves across the western
Atlantic.

&&

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

Drier than normal conditions will prevail across the islands today
and early Friday morning, as indicated by the GOES-East water vapor
channels. At mid-levels, a high-pressure over the northeast
Caribbean is promoting subsidence and dry air at those levels. At
the surface, the interaction of a frontal boundary over the western
Atlantic and a surface-high pressure across the central Atlantic is
inducing a weak southerly wind flow across the northeast Caribbean.
Under these weather conditions, expect above-normal temperatures
north of the Cordillera Central of Puerto Rico, little or no rain
activity, and calm to light and variable winds across Puerto Rico
and the U.S. Virgin Islands.

The weather pattern will persist through at least late in the
morning or the afternoon of Friday when an easterly disturbance,
forecasted to propagate across the islands, enhance rain formation
across PR/USVI. Dynamic aloft could be reinforced by an eastward
propagating mid to upper-level trough forecast to reach the islands,
as both GFS and ECMWF suggest. The trailing moisture of this
disturbance will promote rainy conditions through at least Saturday.
If the timing is correct, urban and small stream flooding will be
likely Friday afternoon through Saturday evening.

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

Fair weather conditions are expected to return on Sunday as a
drier air mass moves across the area, limiting shower activity.
On Monday, a frontal boundary is expected to be situated northwest
of the area, with an increase in low-level moisture expected.
This will cause shower activity to increase somewhat with isolated
to scattered showers across eastern Puerto Rico and the USVI
during the morning hours followed by locally induced activity
across western Puerto Rico during the afternoon hours. The low-
level winds will then increase on Tuesday and Wednesday as a
surface high pressure builds across the western Atlantic. This
will favor a cool advective pattern with patches of moisture
moving across the area from time to time, resulting in trade wind
showers.

Then, by the end of the long term period, the weather pattern
begins to undergo changes aloft as a mid and upper-level trough
amplifies across the central and eastern Caribbean. If model
guidance is correct on this solution, then a more unstable
weather pattern is more likely by the latter half of next week
with more enhanced shower activity possible across portions of
the area.

&&

.AVIATION...VFR conditions will prevail today. Winds will persist
from the ESE- SE at 10 kt or less, with sea breeze variations
after 04/13z. VCSH will remain possible without any impact on
operations.

&&

.MARINE...A northerly swell is expected to impact the Atlantic
waters and local passages later today through Friday. This will
result in choppy seas of up to 6 feet, mainly across the offshore
Atlantic waters. Across the rest of the local waters, seas of up
to 5 feet are expected. Seas are expected to remain below 6 feet
through the upcoming weekend.

For beachgoers, there is a moderate risk of rip currents across
all the northern beaches of Puerto Rico and Culebra as well as the
easternmost beaches of Vieques and Saint Croix for today. The rip
current risk increases to high across the north-central beaches
of Puerto Rico for tonight due to the aformentioned northerly
swell.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 73 86 74 / 20 0 40 50
STT 85 73 85 73 / 20 20 50 60