Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
423 AM AST Sun Apr 10 2022

.SYNOPSIS...Typical seasonal weather conditions will prevail for
the forecast area today. Scattered to numerous showers are
expected for portions of western and northwestern Puerto Rico in
the afternoon hours. This weather pattern will continue through
at least Tuesday, when an upper level trough with a frontal system
increase the potential for thunderstorms, heavy rainfall and
flooding for the local islands.

&&

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

A typical weather pattern is expected through the short term period.
Near to below normal moisture is expected across the local islands
with a few patches of moisture moving in. These patches of moisture
will peak during the daytime hours today and on Monday during the
day as well. Moisture will stabilize on the lower end of normal for
the rest of Monday into Tuesday. The mid to upper levels are
expected to keep things relatively stable, so mainly scattered to
locally numerous showers would be forecast in the afternoon hours
across western PR, but no thunderstorms are in the short term
forecast. For the nighttime and early morning hours, isolated to
scattered passing showers are forecast across the USVI and eastern
PR as well as the local waters. Given the increase in moisture
during the time of max heating for the next couple of days, some
showers across western PR could produce minor flooding such as
ponding of water on roadways and poor drainage areas across isolated
areas. That said, the rainfall coverage on Tuesday is forecast to be
a bit more broad than today and Monday, so the numerous showers
forecast for Tuesday afternoon may cause urban flooding.

The local winds are expected to diminish compared to the past few
days, with speeds of 10-15 mph from the ESE this morning, gradually
shifting to a ENE direction by Monday afternoon. This is due to a
couple of surface high pressures in the Atlantic that will be
dominating the local wind flow, one of them is over the central
Atlantic, which will dominate through today, then another SFC High
will move into the western Atlantic by Monday. The temperatures will
also be near normal through the short term, but today may have a few
degrees above normal high temperature.

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

Unstable weather conditions are forecasted for this term as a trough
and a strong frontal system move over the local area from the
Western Atlantic. The trough is expected to amplify across the
region, promoting unstable weather, including the potential for
thunderstorms for the local islands. This pattern will support the
development of showers with rainfall accumulations over Puerto
Rico and the U.S. Virgin Islands and will persist across the area
for several days. Winds are expected to shift from the north-
northeast as the trough and the frontal system merge. Latest GFS
model guidance forecast the development of organized convection
and thunderstorms across the islands. By Wednesday, associated
bands will start to affect portions of Puerto Rico early in the
morning, enhancing unstable conditions aloft and shower formation.
Similar weather conditions are expected from Thursday through
Sunday. Some of the impacts this weather event can cause are
thunderstorms, flash flooding, urban and small stream flooding,
landslides, ponding of water in low drainage areas, dangerous
driving conditions.

&&

.AVIATION...VFR conditions expected across the local terminals
through the forecast period. SCT/NMRS SHRA possible across W-PR
between 10/17Z and 10/22Z would cause at least VCSH at TJBQ, but
possible TEMPO SHRA at the terminal. Winds will be from the E-ESE at
5-10 KT through 10/13Z, increasing to 10 to 15 KT and shifting to a
more easterly direction with sea breeze variations thereafter.


&&

.MARINE...Breezy east winds up to 15 knots with seas between 3 and
5 feet will prevail for the next couple of days across the
regional waters and passages. For beachgoers, there is a moderate
risk of rip currents for most of the exposed beaches of Puerto
Rico and the U.S. Virgins Islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 75 88 75 / 20 20 10 40
STT 85 75 85 75 / 20 20 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
433 AM AST Mon Apr 11 2022

.SYNOPSIS...A typical seasonal weather conditions will prevail
until today. Scattered to numerous showers are expected for
portions of western and northwestern Puerto Rico in the afternoon
hours. This weather pattern will continue through at least
tomorrow, when a surface front will approach the local area
increasing the potential for thunderstorms, heavy rainfall and
flooding for the local islands. Marine conditions will also start
to deteriorate by tonight, due to a northerly swell that will
affect most of the local waters and passages.

&&

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

Some changes to the weather pattern are expected in the short term
forecast, compared to what we have observed over the past week or
so. A surface high pressure, entering the western Atlantic will
cause the local winds to shift from easterly this morning, to
northeasterly tonight, before shifting to the east again for Tuesday
and Wednesday as they gradually strengthen, with Wednesday having
winds that could reach 20mph over coastal areas. There will be mid
and upper level troughs over the area, that will cause a slight
increase in instability, supporting shower activity over a broad
area on Tuesday and Wednesday, but the mid level temperatures and
other parameters are still not favorable for thunderstorms. Although
the 500mb temps will be steadily getting colder with each day, it`s
not until after Wednesday that the models show a strong signal for
thunderstorm development, though perhaps shouldn`t be completely
ruled out for Wednesday afternoon. The available moisture will be
below normal today, but will be near normal on Tuesday and Wednesday.

The expected weather pattern today will be a typical one once again,
with brief showers in the morning across the local waters, USVI, and
eastern PR, then afternoon showers across western and central PR in
areas of sea breeze convergence. However, starting on Tuesday, an
old frontal boundary will approach the local area, causing the
increase in moisture that will linger into Wednesday. This will
combine with the mid and upper level troughs, to promote a wider
coverage of shower activity, and therefore scattered to numerous
showers are forecast in some areas and at different times on Tuesday
and Wednesday. Near to slightly above normal temperatures are
expected today; but due to the expected increase in moisture,
clouds, and shower activity on Tuesday and Wednesday, the daytime
high temps are forecast to be a degree or two below normal.

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

A frontal system continues to forecast to bring more moisture into
the local area by the beginning of the term. The surface front with
an amplified upper trough are going to promote unstable weather,
including the potential for thunderstorms for the local islands.
This current pattern will support the development of numerous
showers with rainfall accumulations over Puerto Rico and the U.S.
Virgin Islands and will persist across the area for several days.
An increase of winds from the north-northeast is expected as the
frontal system move across the islands. Latest model guidance (GFS
& ECMWF)guidance continues to develop organized convection with
isolated thunderstorms for most of the term. Associated bands of
moisture are expected to enhance shower formation across Puerto
Rico and the U.S. Virgin Islands. Weather impacts continue to be
thunderstorms, flash flooding, urban and small stream flooding,
landslides, ponding of water in low drainage areas, and dangerous
driving conditions. For Monday, weather conditions will improve,
returning back to the typical seasonal weather pattern.

&&

.AVIATION...VFR conditions expected across the local terminals
through the forecast period. ISOL/SCT SHRA expected through 11/16Z,
causing VCSH across the local terminals. SCT/NMRS SHRA is forecast
over central and W-PR, after 11/17Z, which could cause VCSH at TJPS
until 11/21Z. Winds will be from the E at 10 KT or less through
11/13Z, increasing to 10 to 15 KT and shifting to a more E-ENE
direction with sea breeze variations thereafter.


&&

.MARINE...As a frontal system moves towards the local area, winds
are expected to be moderate to fresh once again this week. A
northeasterly swell is forecast to arrive, and building seas up to
7 feet can be observed by early Tuesday. A high risk of rip
currents will start in effect tonight for the north-facing beaches
of Puerto Rico, due to hazardous and choppy marine conditions in
the area.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 76 84 74 / 10 40 40 20
STT 85 75 84 72 / 30 40 30 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
457 AM AST Wed Apr 13 2022

.SYNOPSIS...Fair weather is expected today with scattered
showers expected for portions of western and northwestern Puerto
Rico during the afternoon hours. Marine conditions continue
deteriorating across the local waters. High risk of rip currents
are in effect for the north and eastern beaches of Puerto
Rico, Vieques, Culebra, and the U.S. Virgin Islands. Small Craft
Advisories are in effect for the Atlantic offshore waters.

&&

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

The latest guidance keeps the local area in a dry slot today with
below normal moisture, but near normal moisture is expected for
Thursday and Friday. The model agreement for little to no weather
today is very strong, just about all models at different resolutions
agree that there is a very slight chance of rain today. That being
said, there is always some uncertainty, and therefore, isolated to
scattered but very brief showers are forecast in the morning across
the local waters, USVI, and eastern PR. Mostly fair weather is
forecast in the afternoon, with only a slight chance of brief
showers in the forecast for most of the local islands, while a small
section of eastern and western PR having scattered showers in the
forecast. Any rainfall accumulations is expected to be minimal.

A surface high pressure, across the western Atlantic will cause
moderate to locally strong easterly winds for the next few days.
Winds could reach 20mph over the coastal areas. A broad upper level
trough with strong winds will move over the area on Thursday, which
will cause divergence and increase the chances of thunderstorms over
the local area. In addition, the 500mb temps will be getting colder
with each day, and by Thursday, the 500mb temps will be below
normal, which would support thunderstorm development. The upper
level winds will be slightly weaker for Friday, and the deep
moisture is expected to remain to the north of the local islands, so
the shower and thunderstorm potential on Friday may be mostly across
the northern and western portions of PR and near the northern USVI,
mainly in the afternoon hours.

The daytime temperatures over the next few days are forecast to be
in the mid 80s across the lower elevations, and in the upper 70s to
low 80s across the higher elevations. Overnight lows are forecast to
be in the low to mid 70s across the lower elevations, and in the 60s
across the higher elevations.

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

Bands of moisture associated to the remnants of a cold front will
prevail until late Saturday. On Sunday, a drier air mass is expected
to entrain, with strong trades that are favorable for the
development of morning showers across the U.S. Virgin Islands, and
eastern sectors of Puerto Rico from time to time. Warmer
temperatures are expected. By Monday onwards, a low pressure will
establish north of the area. Therefore, an area of moisture being
pulled from South America, especially Colombia and Venezuela
could potentially enhance unstable conditions aloft producing a
rainfall event over Puerto Rico and the U.S. Virgin Islands. The
potential for the development of organized convection exist with
isolated thunderstorms. Possible weather impacts to take in
consideration are flash flooding, urban and small stream flooding,
landslides and ponding of water in low drainage areas. This
pattern will linger through the end of the long period.

&&

.AVIATION...VFR conditions expected to prevail across the local
terminals through the forecast period. ISOL/SCT SHRA expected
through 13/14Z, causing VCSH across TJSJ and TIST. After 13/17Z, VFR
conds expected to continue, but VCSH is possible at TJBQ. Winds will
be from the E at 15 KT or less through 13/13Z, increasing to 15 to
20 KT with stronger gusts and sea breeze variations thereafter.


&&

.MARINE...A northerly swell will promote choppy to hazardous
marine conditions, with building seas up to 7 feet across the
local waters. Small Craft Advisories (SCAs) are in effect for the
offshore Atlantic waters. Later in the day, SCAs will be in
effect for most of the local waters. High risk of rip currents
are in effect for the north and eastern facing beaches of Puerto
Rico, including Vieques, Culebra and the U.S. Virgin Islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 85 74 / 30 40 40 50
STT 84 74 85 73 / 20 40 30 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
509 AM AST Thu Apr 14 2022

.SYNOPSIS...

Typically weather conditions are forecast for today with
afternoon shower activity due to the presence of low level
moisture from a frontal boundary just at our north. On Saturday
into Sunday, deteriorate weather conditions are forecast as a mid
to upper level trough and the associated low pressure. This pattern
will become more southeasterly winds, and this in turn is expected
to gradually lift more tropical moisture over the forecast area.
Hazardous marine and coastal conditions will prevail for the next
couple of days.

&&

.SHORT TERM...Today through Saturday...Today through Saturday...
Surface high pressure was spread across the west central Atlantic
while a stalled and slowly dissipating frontal shear line sags
west to east north of the region. A mid level area of low pressure
north of the Lesser Antilles along with a broad upper trough will
linger across the region today, but will be further reinforced
and become amplified by Friday into the weekend. The surface high
will maintain a moderate easterly winds today and this will favor
breezy conditions. The winds are to become more southeasterly and
gradually weaken from Friday into the weekend as the high shifts
farther into the central Atlantic, and a cold front moves into the
west Atlantic.

For today low level moisture along the frontal shear line will be
transported across the region from time to time to bring periods of
early morning showers to the north and east coastal areas of the
islands. For the rest of the day there will be sufficient moisture
available across the region to support locally and diurnally induced
afternoon convection, but mainly over parts of the interior and
west sections of Puerto Rico. Lesser afternoon showers are expected
for the U.S. Virgin Islands. Also, good daytime heating and the
marginal instability aloft will favor isolated afternoon thunderstorms
over western PR. This may lead to minor urban and small stream flooding
or ponding of water on roads and in poor drainage areas in isolated
spots.

For the rest of the forecast period, the mid to upper level trough
will become more amplified as previously mentioned. This along with
the much cooler mid-level temperatures will favor the development
of isolated thunderstorms activity over portions of the coastal waters
and in isolated areas across the interior and west sections of Puerto
Rico each afternoon. By Saturday however, as winds diminish and a weakly
induced surface trough develops across the region, expect low level
moisture convergence and pooling to gradually increase especially
by late Saturday. That said, although there remains some inconsistency
in the recent model guidance, the overall pattern and trends suggests
that the passing morning shower activity as well as afternoon convection
will increase by late Friday and into Saturday due to the instability
aloft and good low level moisture convergence. Therefore the potential
for urban and small stream flooding will be moderate to high each
afternoon especially over the central interior and west sections
of Puerto Rico. Meanwhile, the U.S. Virgin islands should expect
mostly isolated passing morning showers, followed by isolated to
scattered afternoon shower activity mainly on the west- end and
downwind of the islands.

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

Model guidance agreed in a very unstable pattern for the long
term period. For the first part, at the upper levels, a polar
trough exiting the east coast of the United States will re-enforce
another upper trough sitting just northeast east of the islands.
As a result, a mid to upper level trough develops over the Hispanola
enhancing cold temperatures at the 500 MB between - 8 to -10 Celsius.
In this evolving pattern, a low pressure develops at the surface,
resulting in a south-southeasterly component in the wind trend
across the region. This wind pattern will drag plenty of ITCZ
moisture with precipitable water values above the climatological
normals, from Sunday onwards. At the same time, the surface high
pressure moving eastward will push the remnants of an old front
and this will create low-level moisture converge across the forecast
area. As the low pressure moves at our north, the combination of
the humidity and the instability aloft will mostly result in widespread
shower activity. According to the Galvez- Davison Index(GDI), conditions
are favorable for isolated to scattered thunderstorms with the heaviest
activity. By late Friday, wind conditions turn unfavorable, as the
pressure gradient relaxes over the area and gentle to moderate winds
are forecast. In general terms, and with the agreement of the guidances
today, expected moderate to strong periods of shower activity
accompanied by isolated thunderstorms for all the upcoming week.
This activity could lead to flash flooding in localized areas. If
this pattern unfolds, rainfall accumulations and saturated soils
will trigger much flood potential during the latter part of the
period, due to the slow motion of the showers. Daytime
temperatures will remain near normals and may fluctuate with the
cloud coverage.

&&

.AVIATION...VFR conds will prevail at all terminals. SHRA and SCT-
BKN lyrs nr FL025...FL050 will affect the local flying area and
portions of the islands due to a frontal shear line north of the
region and moderate easterly trade winds. Sfc wnds will continue fm
east at 10 kts of less incr to 15-20 kt with hir gusts btw 25-30 kt
psbl aft 14/14Z. SHRA/ Isold TSRA psbl ovr W PR fm 14/16Z-14/22Z
with Mtn Top Obscr and MVFR conds with SHRA/Isold. L/LVL wnd fm E 15-
20 kts BLO FL150...Then backing and incr w/ht ABV.


&&

.MARINE...

Deteriorate marine conditions are forecast for the next couple of
days across the local waters. The combinations of a fading
northerly swell and a moderate wind flow will result in seas up to
7 feet across most of the exposed waters and up to 6 across the
nearshore waters. Winds will remain form the east with some
variations and up to 20 knots. Therefore, several small craft
advisories are in effect at least until Sunday. Hazardous coastal
conditions are forecast to prevail as well. There is a high risk
of rip Current for all the north, east and the northwestern
beaches of Puerto Rico, including Vieques and Culebra, as well
all the U.S. Virgin Islands. Elsewhere, the risk will remain
moderate.


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
553 AM AST Fri Apr 15 2022

.SYNOPSIS...
A more unstable and deteriorate conditions will gradually develop
across the region. This evolving pattern will enhance the chance
for showers and isolated thunderstorms for today into the upcoming
week. Moisture will increase considerably Sunday onward. Hazardous
marine conditions are forecast to prevail across the Atlantic
offshore waters and the Anegada Passage with seas up to 7 feet and
winds up to 20 knots.

&&

.SHORT TERM...Today through Sunday...
Surface high pressure remained spread across the west central
Atlantic, but will shift farther east into the central Atlantic
today and through the weekend. Local winds are expected to become
more southeasterly while gradually diminish. A broad mid to upper
level trough extending southwards across the region will be further
reinforced and become amplified by a secondary short wave trough
today through the weekend. Somewhat breezy conditions are still
forecast for today ,especially along coastal areas and accompanying
the passing morning showers. Increasing instability aloft along with
colder mid-level temperatures and increasing low to mid level
tropical moisture convergence, all continue to suggest a much wetter
weather pattern by Sunday and into the following week.

For today, good trade wind moisture advection will bring periods of
clouds and showers across the coastal waters and over parts of the
north and east coastal sections of the islands. This will cause
minor ponding of waters on roads and hazardous driving conditions in
isolated areas especially during the early morning hours. For the
afternoon hours, showers and isolated thunderstorm development is
expected to again be focused mainly over parts of the central and
northwest sections of Puerto Rico with lesser shower activity
expected elsewhere and around the San Juan metro. The activity in
the west may cause minor urban and small stream flooding or ponding
of water on roads and in poor drainage areas in isolated spots.

For the rest of the forecast period, the mid to upper level trough
will become more amplified across the area as previously mentioned.
This along with the cooler mid-level temperatures and divergent
pattern will support the development of isolated to scattered
thunderstorm activity over the coastal waters and parts of the
interior and west sections of Puerto Rico including around the San
Juan metro area. On Saturday, as winds diminish and become more
southeasterly , an induced surface trough is forecast to develop and
lift northwards across the region. By then expect increasing low
level moisture convergence and pooling across the islands especially
by late Saturday, with the worst conditions expected to begin by
Sunday into early next week. The overall pattern and trends based on
recent model guidance all suggest an increase in morning shower
activity as well as afternoon convection to the increasing
instability aloft and good moisture pooling across the region.
Therefore the potential for urban and small stream flooding will
continue to increase each day especially over the interior and
northern half of Puerto Rico and mainly on the west-end and northern
parts of the U.S. Virgin Islands. In the meantime, the U.S. Virgin
Islands can expect mostly passing morning showers, followed by
isolated afternoon shower activity today through Saturday with
increasing chance for Showers and isolated thunderstorms on Sunday
onwards as well.


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

A much wetter pattern is forecast for the long term period over
the forecast area. An enhancement in the upper divergent pulse of
the MJO and a upper level trough just northeast of the region
will increase the instability over the CWA. This mid to upper
level trough is forecast to reflect in the surface, creating a low
pressure trough just over the The Hispanola. As this trough moves
into the northwestern Caribbean near The Bahamas, a more
southeasterly component in the wind profile is forecast. This wind
flow will drag ITCZ moisture across the region with Precipitable
water above climatological normals on Monday and onwards. The
presence of the upper level trough will bring cold temperatures at
the mid to upper levels between the -8 to -10 degree Celsius for
the fist part of the period. Adding to the analysis the Galvez-
Davison Index(GDI) suggests better conditions for isolated to
scattered thunderstorms with the strongest activity on Monday and
Wednesday. However, thunderstorm activity is also expected on
Tuesday as well due to the instability aloft and colder
temperatures.

By midweek as the upper level trough will be again reinforced
just at our west over Cuba, an more ridging pattern in the upper
levels could lead to an anticyclonic circulation overhead,
resulting in a some mid level cloud advection over the forecast
area. This cloud layer could delay the daytime heating, placing
the shower activity more into the mid to late afternoon hours. On
Thursday, a little break in moisture with a slot of drier air is
possible, but shower activity still forecast mainly in the afternoon
hours. By late Friday, wind conditions will turn unfavorable, as
the pressure gradient relaxes over the area and gentle to moderate
winds are forecast. In general terms, expected moderate to strong
periods of shower activity accompanied by isolated thunderstorms
for all the upcoming week. This activity could lead to flash
flooding in localized areas. If this pattern unfolds, rainfall
accumulations and saturated soils will trigger much flood
potential during the latter part of the period, due to the slow
motion of the showers. Daytime temperatures will remain near
normals and may fluctuate with the cloud coverage.

&&

.AVIATION...Prevailing VFR conds at all terminals durg prd.
However brief MVFR conds psbl en route btw islands and ovr east
interior sections of PR . MTN top OBSCR ovr E PR due to SHRA/Low
clouds. SCT- BKN lyrs nr FL025...FL050...FL080. FEW-Isold tops btw
top nr w FL150- FL180 ovr ATL water and nr the northern Leeward
islands. Sfc winds btw 5 to 10 kts...bcmg fm E 15-20 kt aft
15/14Z. SHRA/ Isold TSRA expected ovr wrn PR fm 15/17Z-15/22Z with
VCTS psbl at TJBQ.

&&

.MARINE...

Across the regional waters, choppy marine conditions are forecast
for the next couple of days across the most of the local waters.
Moderate wind flow over the forecast area will result in seas up
to 7 feet across of the exposed Atlantic waters waters and the
Anegada Passage. Therefore, there is a small craft advisories in
effect at least until Sunday. For the rest of the waters seas up
to 6 will remain. Winds will prevail from the east with some
variations and up to 20 knots. Hazardous coastal conditions are
forecast to prevail as well. There is a high risk of rip Current
for all the north, east and the northwestern beaches of Puerto
Rico, including Vieques and Culebra, as well all the U.S. Virgin
Islands. Elsewhere, the risk will remain moderate.



&&

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

[cycloneye]

Area Forecast Discussion...DELAYED
National Weather Service San Juan PR
617 AM AST Sat Apr 16 2022

.SYNOPSIS...
The broad upper level trough continued across the region while a
weakening mid level ridge lingered across the area. The ridge will
however erode by Sunday into early next week as a short wave trough
will dig southwards and amplify the upper level trough, resulting
in increasing instability aloft. A surface high pressure ridge will
lift farther north into the north central Atlantic as an area of
low pressure develops and gradually lifts northwards across the
southwest Atlantic. This will result in a more southeasterly flow
across the region and create a fairly moist airmass as deep tropical
moisture is to be lifted northwards across the forecast area.
This expected pattern will result in a marked increase in shower
and thunderstorm activity during most of the period with moderate
to high potential for urban and small stream flooding by early
next week.

&&

.SHORT TERM...Today through Monday....
An increasingly wet pattern is forecast for the short term period.
At the upper levels, a broad short wave trough will induce instability
aloft. At the surface a strong high pressure will continue to result
in moderate winds across the area. The east- southeasterly wind
profile will push fragments of moisture from the frontal boundary
located at our north into the CWA. This will enhance the shower
activity across windward sections of Puerto Rico and the U.S.
Virgin Islands in the morning hours and afternoon convection over
the west and interior. This activity today is forecast to result
in urban and small stream flooding. On Sunday, at the surface to
mid levels, both model guidances now suggest a slightly intrusion
of drier air, this will diminish the available moisture, however,
given the upper dynamics and the diurnal and local effects
afternoon shower activity with isolated thunderstorms still
forecast for the local area. Additionally, at the mid levels some
anticyclonic circulation overhead, resulting in a some mid level
cloud advection over the forecast area. This cloud layer could
delay the daytime heating, placing the shower activity more into
the mid to late afternoon hours.

On Monday, another upper level trough existing the east coast of the
CONUS will move into the western Atlantic. As this mid to upper
level trough amplifies over the western Atlantic is forecast to
reflect in the surface, creating surface trough just over the The
Bahamas. As this trough develops at our northwestern, another low
pressure will migrate from South America and will move over to the
southwestern Caribbean. The presence of the surface trough at the
northeast and the low pressure at our southwest will result in a
more southeasterly component in the winds. This wind flow will drag
ITCZ moisture across the region with Precipitable water above
climatological normals on Monday. At the upper levels, the divergence
side of an upper level trough will bring cold temperatures at the
mid to upper levels between the -8 to -10 degree Celsius for the
fist part of the period. That being said, expected moderate to
strong periods of shower activity accompanied by isolated thunderstorms
each day mainly in the afternoon hours. In general terms, if model
guidances continues to shows this trend, Sunday looks like the
driest day and Monday the wettest day for the short term period.

.LONG TERM...Tuesday through Saturday...
A very moist and unstable weather pattern is still forecast for
most of the upcoming workweek...with increasing risk for flooding
across Puerto Rico and the U.S. Virgin Islands. A surface trough
over the Central Caribbean and an area of low pressure developing
over the southwest Atlantic will promote a southeasterly wind flow
which will lift deep tropical moisture across the region. This
along with the amplification of the upper trough over the area
will support a very moist advective pattern across the region
through at least the middle of the week. However, moisture will
linger across the area through the end of the week ,with yet another
surge of trade wind moisture expected by the following weekend.
That said, the copious amounts of moisture expected across the
region combined with favorable atmospheric conditions, will increase
the chance for widespread showers and thunderstorm activity across
the islands and coastal waters for most of the week. Based on the
latest guidance which continue to show much inconsistencies in
the timing of the activity, decided to continue with the most likely
time period for the heaviest rainfall to be Tuesday through Wednesday
and possible into Thursday. The areas most likely to receive the
highest rainfall accumulations are portions of the southeastern
and eastern third of Puerto Rico. Periods of locally heavy rains
are also expected for the U.S. Virgin Islands during this time
period as well. Stay tuned for updates and possibly modifications
in the forecast as we continue to monitor how this pattern unfolds.

&&

.AVIATION...VFR conditions are forecast for all TAF sites during the period.
VCSH will continue to TJSJ and TIST until 16/14Z. After 16/16Z some
MVFR/IFR conditions will develop over the interior, therefore VCSH
and -SHRA are included for TJBQ with vcts until 16/22Z. Winds will
remain from the E at 10 knots or less until 16/14Z picking up again
from the E-ES up to 18 knots with gust and sea breeze variation.

&&

.MARINE...
A moderate to locally fresh easterly wind flow will prevail across
the regional waters. A broad upper level trough will combine with
the remnant moisture from a frontal shear-line over the offshore
Atlantic waters, to promote the development of showers and isolated
thunderstorms with areas of locally heavy rains over portions of the
local waters through the period. Choppy and hazardous seas will remain
up to 8 feet through the weekend due to sustained breezy conditions.
Please refer to the latest Coastal Waters Forecast (CWFSJU) and Marine
Weather Message (MWWSJU) issued by the NWS WFO San Juan for the most
current marine updates.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
538 AM AST Sun Apr 17 2022

.SYNOPSIS...
Model guidances continues to suggest a wet and unstable pattern
for the short term period. A broad mid to upper level trough
will be the dominant feature for today. This trough will provide
colder temperatures at the mid levels which will again range
between -8 to -11 degrees Celsius. Meanwhile, a surface high
pressure moving more into the eastern Atlantic will result in a
more southeasterly wind flow today. Embedded in this wind pattern,
fragments of low level moisture from a previous frontal boundary
will continue to filter into the region. Choppy and hazardous seas
will continue across the local waters and passages today.

&&

.SHORT TERM...Today through Tuesday....
Given the expected conditions aforementioned , showers and thunderstorm
development with periods of heavy rainfall is expected especially for
the interior, western and the San Juan metro area today. Rainfall
accumulations will fluctuate between 1-2 inches, as a result, urban
and small streams flooding is expected. Some areas may also experience
ponding of water on roads and in poor drainage areas today.

On Monday, the axis of the upper level trough will shift more south
of The Hispanola pushed by other short wave trough existing the east
of the CONUS. As this mid to upper level trough amplifies over the
western Atlantic is forecast to reflect in the surface, creating a
surface trough or a low pressure just over the The Bahamas east of
the Florida Panhandle. As this feature develops at our
northwestern, another strong low pressure will migrate from South
America and will move over to the southwestern Caribbean. The
combination of the both low pressures will result in a more
southeasterly component in the winds. This wind flow will drag
plenty of ITCZ moisture across the region with Precipitable water
above climatological normals on Monday. As a matter of fact, both
model guidances continues to show a even more wet trend for Tuesday
with precipitable water values near 2 inches which is well above the
climatological normals. Meanwhile at the upper levels, the
divergence side of the upper level trough will move just over our
CWA and will aid the heavy shower activity over the interior and
northwestern Puerto Rico, including the San Juan Metro area.
Additionally, the potential for scattered thunderstorms increase on
Tuesday as suggest the Galvez-Davison Index (GDI) over the forecast
area. As a result, scattered thunderstorms are included in the
weather forecast. That being said, expected moderate to strong
periods of shower activity accompanied by isolated thunderstorms
each day mainly in the afternoon hours. In general terms, if model
guidances continues to shows this trend, today looks like the driest
day and Tuesday the wettest day for the short term period.

.LONG TERM...Recent model guidance appears to be in much better
agreement and continued to suggest a very moist and unstable
weather pattern for most of the work week with possibly lingering
moisture into the following weekend. Therefore expect deteriorating
weather conditions through at least Thursday as a plume of deep
tropical moisture will continue to be lifted up across the region
steered by the dominant southeasterly wind flow. This along with
the amplification of the mid to upper level trough just west of
the region will further enhance convective across the forecast
area. For now, the chance for urban and small stream flooding
along with mudslides in areas of steep terrain and rapid rises
along rivers and streams will remain moderate to high at least
until Thursday.

As these expected conditions unfold expect an increasing risk for
wetting rains and flooding across Puerto Rico and the U.S. Virgin
Islands as previously mentioned. The influence of the surface trough
over the central Caribbean and an area of low pressure developing
and lifting northwards over the southwest Atlantic will promote a
moist southeasterly wind flow across the region. Consequently,
good moisture convergence and pooling can be expected across the
region. This scenario will all support a very moist advective
pattern at least into early Thursday. However, low level moisture
will linger across the area through the end of the week as another
quick surge of moisture from an easterly pertubations will cross
the region as winds become more east to north east. The deep
layered moisture expected across the region combined with favorable
atmospheric conditions will therefore maintain a moderate to high
risk for widespread showers and thunderstorm activity across the
region at least until early Thursday.

The best chance for widespread shower and isolated thunderstorms
activity remains Wednesday into early Thursday morning. The areas
most likely to receive the highest rainfall accumulations are portions
of the southeastern and eastern third of Puerto Rico during the late
night and morning hours followed by activity spreading across the
central interior and northern half of Puerto Rico during the daytime.
Periods of locally heavy rains are also expected for the U.S. Virgin
Islands during this time period as well. As a result the chance for
urban and small stream flooding will remain moderate to high at least
into early Thursday. Lesser impacts are so far expected by Thursday
afternoon and on Friday and into the upcoming weekend based on model
guidance. However, minor urban and small stream flooding and ponding
of water on roads and poor drainage areas will still remain possible
in isolated areas. Gradually improving conditions are expected for
the following weekend as winds become more east to northeast and a
surface high pressure builds across the western Atlantic while a
mid to upper level ridge builds over the area.

&&

.AVIATION...
Mainly VFR conditions will prevail for the forecast period. -RA
to SHRA expected near TJSJ causing VCSH. SHRA/TSRA are included in
TJBQ causing some brief MVFR conditions at 17/18Z. Some VCSH are
included for TJSJ, TISX and TIST from 18/03Z. Winds will remain at
10 knots or less until 17/14Z for most of the TAF sites, increasing
at 15 knots with seas breeze variation at 17/15Z.

&&

.MARINE...Hazardous seas expected today and through at least Monday,
as seas of 7 or 8 feet are expected across the Atlantic waters, offshore
Caribbean, Anegada Passage, and the waters surrounding the northern
USVI. Therefore, Small Craft Advisories remain in effect. Small craft
operators should exercise caution elsewhere. There is also a high
risk of rip currents for many of the local beaches and a moderate
risk of rip currents remaining beaches except for some of the
protected beaches in the west coast of Puerto Rico.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 75 86 75 / 50 50 60 50
STT 83 74 83 75 / 40 50 40 60

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
524 AM AST Mon Apr 18 2022

.SYNOPSIS...
An unstable weather pattern is forecast for the first part of the
workweek, especially Tuesday into Wednesday. This wet pattern
will increase the potential for urban and small stream flooding
over some sections of Puerto Rico. Conditions will remain
unstable at least until Thursday when the upper level trough
moves more to our east. However, rainfall activity is still
forecast each day over the interior and northwestern sections of
Puerto Rico, as well as the San Juan Metro area. Hazardous marine
and coastal condition will prevail for today mainly due to breezy
conditions across the local waters.

&&

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

High pressure at the surface in the mid Atlantic north of 40 degrees
north latitude will move east during the period, but will be
replaced by another, stronger high pressure on Wednesday. When a
strong low pressure develops along the east coast of the United
States this evening a trough will develop over the eastern tip of
Cuba overnight and move into Hispaniola by Wednesday. At mid levels
a ridge of high pressure will persist northeast of the local area
with a trough moving into the area from the west on Tuesday and
weakening on Wednesday. At upper levels, a weak short wave trough
will move through the area overnight then west southwest flow will
return for the rest of the period as low pressure digs southeast
over Cuba and High pressure ridges weakly over the Lesser Antilles.

Moisture now north of Venezuela will be picked up by the trough in
the lower levels and transported north; first into the Dominican
Republic and then Tuesday and Tuesday night into Puerto Rico before
being pushed back to the west later on Wednesday by flow around the
high pressure at lower levels in the mid-Atlantic. While our normal
pattern of night and morning showers will persist through the period
across Puerto Rico during the morning hours followed by heavier
showers and isolated thunderstorms in the afternoon in the interior
and western portions, the additional moisture will increase the
showers coverage and intensity Tuesday through Wednesday. Hence the
threat of urban and small stream flooding will continue for the
middle portion of the week.

Unfortunately, the U.S. Virgin Islands, will see only the passing
moisture from the east southeast flow, but for now, the heavier
amounts of moisture appear to be remaining west of the area and
expected rainfall accumulations appear to be light.

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

A unstable weather pattern is forecast for Thursday into Friday.
An upper level trough with an axis located just over the east end of
Cuba will generate unstable conditions aloft. This short wave
trough is forecast to reflect as a surface trough just over The
Hispanola. In this evolving pattern, a building surface high
pressure exiting from the east coast of the CONUS will aid a shift
in the surface winds more to the east-northeast. According to
both model guidances, low level moisture with precipitable water
above normals will remain in place over the local area. The
combination of the instability aloft, the plenty of moisture and
the local effects will result in afternoon activity with isolated
thunderstorms, mostly over the interior and western sections of
Puerto Rico. Urban and small stream flooding is expected with the
heaviest activity.

For Saturday into Sunday, the building surface high pressure over
the western Atlantic will sink more to the central Atlantic
resulting in mostly east-northeast wind flow. Embedded in this
wind profile, the Islands will be surrounded by moisture with
precipitable waters above the climatological normals. Meanwhile,
the presence of the zonal flow at the upper level will result in
colder temperatures at the 500 MB ranging between the -6 and -8
Celsius. Additionally, Galvez-Davison Index (GDI) shows chances
for isolated thunderstorms for the afternoon hours, mainly with
the heaviest showers. For the last part of the long term, the
dominant feature will be the surface high pressure just to our
northwest. There are some minor discrepancies in both global
model guidances in terms of the available moisture for this part
of the period. The GFS place more wet conditions, but the ECMWF
remain a little drier. Nevertheless, the available moisture will
be enough to combine with the local effects to result in rounds of
afternoon showers on Monday. Daytime temperatures will remain
between the mid 70s to mid 80s, and some upper 80s in isolated
areas due to the southeasterly component in the winds, and will
fluctuate with the cloud coverage.

&&

.AVIATION...Mainly VFR conditions are expected thru 18/15Z. Isold
SHRA will occur ovr ern PR with some mtn topping. Then SHRA will
dvlp aft 18/15Z--first in ern PR then in wrn PR. Isold TSRA psbl aft
18/17z. Sfc winds E 10 kt or less, bcmg aft 18/13Z 10-18 kts with
ocnl gusts to 25 kft in sea breezes. Maximum winds WSW 77-87 kt btwn
FL420-450, but diminishing during the day.


&&

.MARINE...
A moderate to locally fresh easterly wind flow will prevail across
the regional waters. As a result, choppy and hazardous seas will
continue with up to 8 feet across the Atlantic and Caribbean
offshore waters and the Anegada Passage due to sustained breezy
conditions. Given the marine conditions, small craft advisories
are in effect for those waters, please refer to the latest Coastal
Waters Forecast (CWFSJU) and Marine Weather Message (MWWSJU)
issued by the NWS WFO in San Juan for the most current marine
updates. There is a high risk of rip current for all the north,
east and southeast exposed beaches of Puerto Rico, Culebra and
Vieques, as well all the U.S. Virgins Islands. Elsewhere the risk
will remain moderate, except for the west coast just south of
Rincon where the risk will be low.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 87 74 / 50 30 70 70
STT 84 76 84 73 / 30 20 60 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Tue Apr 19 2022

.SYNOPSIS...Weather conditions will fluctuate between wet and
unstable and a more drying trend through the end of the workweek.
Today the potential for thunderstorms is expected to increase,
which could enhance urban and small stream flooding,over portions
of Puerto Rico. Hazardous marine conditions and choppy seas will
prevail across the local waters through at least tonight due to
moderate and fresh winds with a small northeasterly swell.


&&

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

High pressure at the surface over eastern Canada will move southeast
into the mid Atlantic during the period and join another high
pressure in the east central Atlantic. A vigorous low pressure is
moving rapidly up the eastern coast of the United States while
deepening rapidly. Strong convergence is found south of it in the
form of a front that extends south to a very weak low over the
Bahamas. Troughing is also found extending south into the Caribbean
across Hispaniola. This is serving as a focal point for showers and
thunderstorm formation and is the axis of the best moisture. At mid
levels low pressure is found south of Santo Domingo and flow is
generally toward the north. This area served as the focus of
persistent thunderstorms during the day Monday, but they moved east
and dissipated overnight in the Caribbean Sea. Currently there are
no thunderstorms withing 250 miles of the NEXRAD radar near Caguas,
Puerto Rico. At upper levels a weak short wave moved through Puerto
Rico and is helping, in conjunction with the mid level lows, to
maintain widely scattered showers of light to moderate intensity
over eastern Puerto Rico, its south coast and the Caribbean waters.
Another shortwave trough at upper levels will advance to the
southeast during the period and will be found over Cuba by Thursday.
This will help to maintain southwesterly winds over the area through
Thursday at 250 mb.

Models have over-estimated the amount of showers expected this far
east from the zone of convergence associated with the trough over
the Caribbean. Only very modest amounts have been noted on National
Weather Service Radar--generally under one quarter inch and mostly
less than one tenth inch. Rainfall over the area now appears to be
mostly attributable to a band of moisture stretching southeast from
Puerto Rico across Guadalupe and into the western tropical Atlantic
that is feeding into the area. Currently it is moving slowly
northwest across Puerto Rico. Today, it is expected to enhance the
normal diurnal pattern in southeasterly flow yielding showers and
isolated thunderstorms by afternoon in northwest Puerto Rico that
may also generate some urban and small stream flooding for Puerto
Rico, while mostly neglecting the U.S. Virgin Islands. However, by
Wednesday it moves west out of the area and allows air only dappled
with moisture to cross through. During this period the GFS wants to
bring the zone of convergence and showers into the Mona Channel and
this may also disrupt the normal pattern, however shower activity
should diminish as total precipitable water decreases. On Thursday
flow begins to gain a northerly component and most of the best
moisture is pushed out of the area. This flow and the consequent
drying will be enhanced at 700 mb by a trough that extends into the
area from the east southeast out of the western Tropical Atlantic
from a low near 27 degrees N, 37 degrees W and high pressure over
northern Florida.

This is a complicated situation for sure, and one that has been
evolving slowly during the last 7 days, therefore near-term
confidence is only medium at this time.


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

On Friday, winds will flatten out at upper-levels becoming mainly
zonal. During this stage, a jet streak will intensify for the
next few days over the northeastern Caribbean basin to the east,
across the tropical Atlantic. According to both GFS and ECMWF
models, the divergent side of this jet streak will remain over the
forecast area through the weekend maintaining dynamical
instability aloft during this period. At mid-levels, a weak short-
wave trough will remain with 500 mb temperatures between -8 to -7
degree Celsius, well within seasonal normals. These features will
support favorable conditions at mid- to upper-levels for deep
convective development during the early part of the long-term
period. Activity should not be widespread, but support mostly
isolated thunderstorms when combined with surface heating and
local effects.

The limiting factor will be moisture availability. Model guidance
suggests Friday as the wettest day through the weekend period.
Precipitable water and relative humidity values between 850 to 500
mb are forecast to remain between normal to above normal
climatological levels. Therefore, under an east northeast wind flow,
expect isolated to scattered showers across the northern and eastern
portions of Puerto Rico and U.S. Virgin Islands during Friday
morning. In the afternoon, activity should move across interior and
west/southwest Puerto Rico where scattered to numerous showers and
isolated thunderstorms could be observed. Streamers downwind of
the local islands could also affect the eastern coastal
municipalities of Puerto Rico in the afternoon. This will produce
minor urban and small stream flooding along with ponding of water
in roadways and poorly drained areas.

Moisture content is forecast to plummet on Saturday with
precipitable water values decreasing to below normal to near
normal levels. This will promote clear to partly cloudy skies with
a few showers developing mostly across southwestern Puerto Rico
in the afternoon. Sunday, a patch of moisture embedded in the
northeasterly trades will bring another round of shower activity,
accompanied by isolated thunderstorms developing with the onset of
sea breeze convergence across west/southwest Puerto Rico in the
afternoon. A decrease in wind speeds throughout the weekend will
enhance residence time of any shower activity increasing rainfall
accumulations with the heaviest rains.

Uncertainty widens for the remainder of the forecast period. GFS and
ECMWF both coincides in the development of a strong surface low
pressure system across north central Atlantic as a a surface ridge
builds over eastern United States. This will induce a northerly wind
flow dominating the northern Caribbean through midweek of next week.
At the same time, a surface high pressure system over the eastern
tropical Atlantic will induce a southerly wind flow across the
eastern Caribbean advecting tropical moisture northward throughout
this period. This will produce a shear line along with a southwest
to northeast frontal boundary slowly moving northward. The
difference between the global models lie on the positioning of
this shear line and frontal boundary. GFS has it more northern,
supporting once again the wettest solution. This should enhance
moisture convergence across the Caribbean basin while maintaining
a moisten atmospheric column through the remainder of the forecast
period. On the other hand, ECMWF has it well south of the
forecast area promoting dry mid-to upper-levels supporting a more
stable weather solution. Therefore, forecast confidence is low due
to large discrepancies between models regarding moisture
availability. We will continue to monitor model trends with this
event.


&&

.AVIATION...Mainly VFR conds over PR and the USVI, except for some
MVFR for CIGs along the south coast of PR south of the Cordillera
Central. Mountain obscurations there. SHRA/Isold TSRA dvlpg aft
19/16Z mainly north of the Cordillera Central with lcl MVFR/IFR
conds and mtn obscurations. Sfc winds E-ESE less than 10 kt bcmg aft
19/14Z ESE with sea breezes 10-20 kt and gusts alg the coasts to 25
kt. Max winds WSW-W 50-80 kt btwn FL400-470 strongest at FL430.
Winds SSE-SSW 5-15 kt btwn FL110-320.


&&

.MARINE...Hazardous and choppy marine conditions continue across
the local waters. Therefore, Small Craft Advisories will continue
in effect through tonight, due to seas up to 7 or 8 feet. Winds
will be up to 20 knots across most of the local waters. There is
still a high risk of rip currents across many of the local
beaches.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 74 85 75 / 70 50 50 40
STT 84 74 85 74 / 50 10 30 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
501 AM AST Wed Apr 20 2022

.SYNOPSIS...Although variations in moisture levels are expected, a
generally moist and somewhat unstable weather pattern will hold
through the cycle. The best chance for shower and possible
isolated thunderstorm development, with the potential for ponding
of water on roadways and poorly drained areas to localized urban
and small stream flooding, will result from afternoon convective
development each day. Choppy marine conditions and life-
threatening rip currents will prevail during the next few days.


&&

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

High pressure at the surface over the Atlantic near 49 degrees north
and west last night will move southeast and fade rapidly as it is
pushed out by the cold front. The high will reach the mid Atlantic
Friday. Although the cold front moves into the Atlantic at higher
latitudes, it will remain west of the local area and drift even
farther west during the period as it loses strength. This is in part
due to a weak low at the surface under a mid level low in the
eastern Atlantic that will amplify northeast flow around it as it
drifts west during the period.

Good moisture advection out of South America continues to be found
east of the troughing extending north out of the low just north of
Panama. This is serving as a focal point for showers and
thunderstorm formation and is the axis of the best moisture that,
although fading, remains close to Hispaniola. The eastern edge of
this moisture is now approaching Saint John and the drier air will
continue to invade in flow that will turn to the northeast tonight.
Moisture will return early Friday morning and Friday as a band of
moisture forms northeast of the area and is brought in with the
flow. Currently the GFS has this moisture peaking around 07Z Friday
with precipitable water values of just over 1.9 inches. It will mark
the return of showers to the northeast coast Friday morning, and the
shift of the focus of afternoon convection to southwest Puerto Rico.

At mid levels low pressure is found in the east central Atlantic. A
passing trough well north of that low will cause east-west troughing
north of the local area on Friday. At upper levels a ridge that
extends north from the Leeward Islands will move just slightly east.
A shortwave trough, now digging down into Cuba, will flatten out as
it approaches the local area on Friday and the upper level jet on
its forward side will remain north of the area, but also cause
stronger winds aloft. There will be some help for showers on
Thursday from it over eastern Puerto Rico.

This pattern will keep skies partly to mostly cloudy with scattered
showers, especially Wednesday and Friday. Some heavier rains may
occur where local circulation holds shower formation in one place
for more than an hour and urban and localized small stream flooding
are possible. Winds will continue to fade during the period, and the
turn to northeast flow on Thursday and Friday will allow the maximum
temperatures on northern side of Puerto Rico to cool one or two
degrees. Otherwise large changes in the weather experienced are not
anticipated during the short-term.

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

Although there are some discrepancies among global models, the
long-term forecast leans towards a generally moist environment
dominating the region, as suggested by model guidance from the
GFS. A surface high pressure moving into the western Atlantic will
maintain east to northeast surface winds, holding at 10-20 knots
through Monday but diminishing to 5-15 knots and backing more to
the northeast by Tuesday into Wednesday as the high fades. By
Thursday, surface winds will veer to the east- southeast as
another multi-layer high pressure over the tropical Atlantic and
to our east extends further westward into the eastern Caribbean
region. At the 850 to 700 mbar layer, winds will veer to the
south- southeast earlier in the week, supporting mid-level
moisture advection as early as Monday. So far, patches of moisture
streaming across the region will maintain normal seasonal
moisture levels around 1.3 to 1.6 inches during the weekend. After
that, deep tropical moisture advection will cause moisture levels
to reach above-normal seasonal levels, with model-estimated
precipitable water values increasing from 1.7 inches by Monday
afternoon to 2.2 inches by late Thursday night.

Since conditions aloft should remain favorable for deep
convective development, with mid-level temperatures ranging
between -6 and -8 degrees Celsius, expect a gradual increase in
shower and isolated thunderstorm development as the week advances,
mainly resulting from afternoon convection. So far, the best
chance for significant rainfall accumulations appears to be
Wednesday and Thursday, not only due to an increase in moisture
levels but also from slow-moving showers under a weak steering
flow. As a result, the threat of flooding will also increase, with
moderate to heavy rains generating ponding of water on roadways
and poorly drained areas to urban and small stream flooding,
mainly across and to the north of the Cordillera Central. Since
uncertainties increase with time and any variations in the timing
and moisture levels could result in a completely different
scenario, there is low confidence in this forecast.


&&

.AVIATION...Mainly VFR conds over PR and the USVI, except for some
MVFR for CIGs due to sct SHRA from Cabo Rojo to Aguas Buenas and
south. Mountain obscurations there. SHRA/Isold TSRA dvlpg aft 19/16Z
with lcl MVFR/IFR conds and mtn obscurations. Sfc winds E-ESE less
than 10 kt xcp 10-15 kt in the USVI, bcmg aft 19/14Z ESE with sea
breezes 10-20 kt and gusts alg the coasts to 27 kt. Max winds W 50-
70 kt btwn FL350-480 strongest at FL420. Winds SE-S less than 18 kt
btwn FL024-170 strongest at FL040.


&&

.MARINE...Moderate to fresh winds up to 20 knots will maintain
choppy marine conditions through the rest of the workweek into the
upcoming weekend, mainly across the offshore waters and local
passages, where small craft operators should exercise caution.
Mariners can expect seas of 5 feet or below and surface winds up
to 15 knots elsewhere across the local waters. For beachgoers, a
high risk of rip currents remains for beaches across the northwest
to the northeast and the southeast coasts of Puerto Rico and some
beaches of Vieques, Culebra, and St Croix.


&&

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

[cycloneye]

Let's prepare folks.

 https://twitter.com/NWSNHC/status/1516789546284855299

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
513 AM AST Thu Apr 21 2022

.SYNOPSIS...Northeast to east northeast flow will usher in periods
of showers and shift the focus of afternoon convection to the
interior and southwest portions of Puerto Rico. Limited shower
activity is expected for the U.S. Virgin Islands. Bands of
moisture will enhance this pattern Friday morning, Saturday night
and Tuesday morning. Deeper moisture is being watched as a front
approaches the area later Thursday next week and moisture
increases the following weekend.

&&

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

A surface high pressure over the western Atlantic will maintain
moderate east to northeast winds of up to 15 mph today, backing more
to the northeast as yet another surface high pressure moves off
the east coast of the United States into the western Atlantic
Friday into Saturday. A mid to upper level low, centered over the
north-central Atlantic, extends into the northeastern Caribbean.
This feature will maintain a building cell of the subequatorial
ridge to the south while supporting a northeasterly flow at the
700 mb layer until it fades on Friday. In its wake, a shortwave
trough, with its axis still digging south into Cuba, will flatten
and settles north of the area on Friday into Saturday, sustaining
a subtropical jet maxima just north of the region as it presses
against the subequatorial ridge through the rest of the forecast
cycle. This scenario will support favorable conditions for deep
convective development with enhanced upper-level divergence. In
the meantime, bands of moisture forming to the northeast and
streaming across the region in the general flow will cause
moisture levels to rise as high as 1.8 inches at times. These
bands will feed nocturnal/early morning showers under a cool
advective pattern, followed by afternoon convective development
across the local islands, with the potential for isolated
thunderstorm development. Nonetheless, drier air will move into
the area between bands, limiting shower development at times.

For today, a drier air mass will filter the area, but lingering
moisture combined with local and diurnal effects will support
showers and possible isolated thunderstorm development in the
afternoon. This activity will cluster across the interior to western
sections of Puerto Rico, where moderate to heavy rains could lead to
ponding of water on roadways and poorly drained areas to localized
urban and small stream flooding. Streamers cannot be ruled out, with
showers affecting portions of eastern Puerto Rico in the afternoon.
For the US Virgin Islands, mainly fair weather conditions should
prevail until a band of moisture moves into the forecast area
tonight. Somewhat drier air will follow by early Saturday morning
and yet another band of moisture by Saturday night into Sunday
morning. Daytime highs will peak into the mid to upper 80s across
lower elevations, with lower temperatures across higher elevations.


.LONG TERM...Sunday through Wednesday...
High pressure will move into the western Atlantic on Sunday as low
pressure deepens in the central Atlantic. The trailing cold front
will approach Puerto Rico and the U.S. Virgin Islands on Thursday
with northeasterly flow during most of the period. Moisture from
the front will stall over the area Thursday and Friday, with even
better moisture invading the area in southwest flow on Friday.
Moisture continues to improve over the following weekend.

At 500 mb, weak troughing will be seen extending from a broad low
in the Atlantic. At upper levels, flow is relatively flat Sunday
through Thursday with an upper level jet arching just north of
the area and brushing Puerto Rico and the U.S. Virgin Islands. On
Friday the jet is joined by a sub-equatorial jet that will move
over the area and usher in considerably wetter weather.

&&

.AVIATION...Mainly VFR conditions are expected. However, SHRA/TSRA
from afternoon convection could result in brief MVFR conditions
across TJBQ between 21/17-22Z. Minimal impacts to operations are
expected, but an increase in passing SHRA could also lead to brief
MVFR conditions after 21/22Z across northern PR and USVI terminals.
Surface winds will remain from the E to ENE at 5-10 knots,
increasing to 10-15 knots with higher gusts after 21/14Z.

&&

.MARINE...Conditions are relatively constant through the week with
4 to 6 foot seas in the Atlantic and 2 to 5 foot seas in the
Caribbean. Winds also remain moderate to fresh, but will become
more northeasterly now and over the weekend. Although small craft
advisories are not expected during the next 7 to 8 days, showers
and thunderstorms may increase considerably late next week and
continue into the following weekend making navigation a little
more difficult.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
518 AM AST Fri Apr 22 2022

.SYNOPSIS...Easterly flow maintained by higher pressure to the
north will continue to bring patches of moisture and showers across
the area with cooling from the central Atlantic. Flow will
gradually become more northeast as high pressure builds off the
east coast of the Carolinas. On Friday of next week flow will
become more southerly and moisture will increase considerably as
tropical moisture enters the area, but until that time showers
will favor west and west southwest Puerto Rico in the afternoons
and the northeastern sections during the overnight and morning
periods.

&&

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

A set of surface high pressures over the northwestern and north-
central Atlantic will maintain an east to northeast wind flow of up
to 15 mph through the weekend. These features will also hold a
prominent northeasterly flow at the 850-700 mb layer. An upper-
level shortwave trough, with its axis extending further west over
the Bahamas, will continue to flatten as it slowly lifts
northeastward, sustaining a subtropical jet maxima just north of
the region as it presses against the deepening subequatorial ridge
to the south. This scenario will favor enhanced upper-level
divergence and favorable conditions for deep convective
development through the forecast cycle. At the surface, a set of
bands of moisture streaming across the region in the general flow
will cause moisture levels to rise as high as 1.7 inches at times.
The timing of these bands will be critical to feeding
overnight/early morning showers under a cool advective pattern and
afternoon convective development across the local islands.
Relatively drier air, with precipitable water values dropping as
low as 1.30 inches, will also move into the area after each band,
limiting shower development and briefly promoting mainly fair
weather conditions.

The first band of moisture, which has moved into the forecast area
from the northeast during the overnight hours, will continue to
bring isolated to scattered showers to portions of northern and
eastern Puerto Rico and the U.S. Virgin Islands through the rest of
the morning hours. As this band propagates westward throughout the
day, the bulk of the activity will shift to portions of the western
interior to southwestern sections of Puerto Rico, steered by the
dominant low to mid-level northeasterly flow. A high moisture
environment and favorable conditions aloft combined with local and
diurnal effects will enhance afternoon convection with the potential
for isolated thunderstorm development. The resulting moderate to
locally heavy rains could lead to ponding of water on roadways and
poorly drained areas to urban and small stream flooding across these
areas through the evening hours. A mass of drier air will quickly
follow, enveloping the area tonight and limiting overnight/early
morning shower activity until another band of moisture reaches the
area between Saturday afternoon and late Sunday night. Although a
gradual erosion of the available moisture is expected by Sunday,
moisture levels will remain high enough to support a seasonal shower
pattern. Daytime highs will peak into the mid to upper 80s across
lower elevations, with lower temperatures across higher elevations.


.LONG TERM...Monday through Sunday...
Low pressure at the surface continues to strengthen in the mid
Atlantic, while high pressure off the coast of the Carolinas
drives cooler air toward the area. On Tuesday and Thursday bands
of moisture in the form of cold fronts, or lines of convergence,
push into the local area and bring additional moisture separated
by a dry slot on Wednesday. The original low moves into the north
central Atlantic and weekend. The final frontal band is joined by
tropical moisture that is expected to greatly enhance shower
activity over the area the following weekend. This moisture is
accompanied by a near complete reversal of the flow that becomes
nearly south.

Flow at mid and upper levels is mostly zonal, that is from west to
east, with the main sub-tropical jet holding north of the forecast
area. The models show the sub-equatorial jet only very weakly
during the weekend next week. Stability is borderline so some
thunderstorms are indicated, but mainly on Tuesday and over the
weekend. Moisture appears to be the strongest driver of activity
and it increases unsteadily toward the first of next month. The
biggest dip will come between the two frontal bands on Wednesday.

This is a somewhat unusual pattern and so confidence is only
medium and timing could shift plus or minus twelve hours as we
draw nearer to the latter part of the forecast. In the final
analysis, however, at least scattered showers are indicated for
Puerto Rico every day during the period with the south coast
receiving the least rain until Thursday or Friday.

&&

.AVIATION...Mainly VFR conditions are expected across all local
terminals. However, an increase in SHRA moving inland from the
waters could result in brief MVFR conditions at TJSJ and USVI
terminals through 22/14Z. SHRA/TSRA development could also result in
brief MVFR conditions across terminals of western Puerto Rico.
Nonetheless, minimal impacts on operations is expected. Surface
winds will remain from the E to NE at 5-10 knots through 22/14Z,
increasing to 10-15 knots with higher gusts after that.

&&

.MARINE...Low pressure in the Atlantic will likely generate some
strong swell of 6 to 7 feet from the north northeast beginning on
Wednesday and peaking on Wednesday night. It is possible, if the
low develops as forecast, for this to create high surf on the
north coasts of Puerto Rico as well as small craft advisories in
the Atlantic waters and the Caribbean passages. Winds however are
expected to diminish over the area as these swell approach.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 74 85 74 / 60 40 50 60
STT 84 74 85 74 / 30 20 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
540 AM AST Sat Apr 23 2022

.SYNOPSIS...Expect a more seasonal pattern for the weekend and
early workweek. Morning showers over the east of Puerto Rico and
the U.S. Virgin Island and afternoon showers over the west of
Puerto Rico. Seas will remain up to 6 feet across the Atlantic
offshore waters, therefore, small craft operators should exercise
caution. There is a high risk of rip current for all the north
and east coast of Puerto Rico, including Culebra and St. Croix.


&&

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

Seasonable weather conditions are expected to prevail through the
short term period. A persistent, moderate northeasterly steering
wind flow should promote a cool advective pattern during the night
and early morning hours, with showers moving over windward areas of
PR and portions of the USVI. Then, during the afternoons, the sea
breeze is expected to develop along the southern coastal sections of
PR, promoting low-level convergence over the Cordillera Central and
the southwestern coastal sections. There is a slight to moderate
threat for urban flooding across the southwestern quadrant of PR
each afternoon. Across the USVI, Vieques and Culebra, streamers are
expected to develop around noon, leaving mostly minor rainfall
accumulations downwind of the islands.

Precipitable water content(PWAT) is expected to fluctuate from
1.25-1.50 inches through Sunday. The 500 mb temperatures should
remain around -7.5C, and therefore, isolated thunderstorms were
left in the forecast during the afternoon period over SW PR. On
Monday, the PWAT is forecast to increase near 2.0 inches, as a
line of convergence develops across the local area in response to
a col area setting up just east of the Windward Islands.
Therefore, shower activity should increase in coverage and as
lighter winds are expected, the threat of urban and small stream
flooding will also increase.

.LONG TERM...Tuesday through Monday...

Long range model guidance is not showing significant changes to
the current long-term forecast, as a low-pressure system at the
surface continues to get stronger in the mid-Atlantic during the
first part of the forecast period. Meanwhile, a surface high
pressure is expected to linger over the southwestern Atlantic,
through at least early in the weekend. This should continue to
promote a moderate northeasterly wind flow across the region. By
early mid-week, the remnants of a front will maintain enough
moisture content over the region to trigger seasonal shower
activity across the islands. On Wednesday, a drier air mass is
expected to dominate the area for a relatively short period of
time, promoting fair weather conditions. On Thursday, expect a
second pulse of moisture to move into the area due to another
frontal boundary. Late mid-week, the winds are forecast to become
more zonal (easterly), and shift from the southeast along with an
increase in PWAT content from the Caribbean waters. This pattern
will continue at least until the beginning of the workweek.


&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, showers are expected to
develop over south-southwest PR btw 23/16z-22z, which may lead to
brief MVFR conds at TJPS. Winds are expected to continue from the
northeast at 12-18 kt with higher gusts and sea breeze variations
aft 23/14z.


&&

.MARINE...Small crafts should exercise caution across the offshore
Atlantic waters due to seas up to 6 feet, elsewhere, seas should
range from 3 to 5 feet. East to northeast trades around 15 kt are
expected to continue through the rest of the weekend, with
locally higher winds across the northwest and southwest coastal
areas of Puerto Rico.

There is a high risk of rip currents for all the north and east
coast of Puerto Rico, including Culebra and St. Croix.


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Mon Apr 25 2022

.SYNOPSIS...A surface high pressure over the western Atlantic will
promote moderate to locally fresh trades during the next several
days. A seasonable weather pattern is expected to prevail through
the workweek. During the weekend, a low level trough is forecast
to develop across the eastern Caribbean, increasing showers and
thunderstorms across the local area.


&&

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

A surface high pressure anchored over the western Atlantic, and a
developing deep layered low over the central Atlantic will continue
to promote a moderate northeasterly wind flow through the short term
period. Embedded in this flow, patches of moisture and pockets of
drier air will continue to advect from the Atlantic waters from time
to time. This seasonable weather pattern should promote light
passing showers during the night and early morning hours over the
northern half of the islands, followed by organized shallow
convection developing over the southwest quadrant of Puerto Rico
each afternoon. The remnants of a frontal boundary should reach the
local area on Tuesday afternoon, and the precipitable water content
is expected to peak around 1.50 inches. Model guidance suggest drier
air filtering on Wednesday, behind the remnants of another weak
frontal boundary.

.LONG TERM...Thursday through Wednesday...

Latest model guidance suggests a similar weather pattern to previous
days, with winds out of the northeast and mainly fair weather
conditions, at least for the first part of the long-term period.
By early Friday morning, expect a transition to a wetter period as
a low-level trough strengthens across the eastern Caribbean,
bringing tropical moisture into the area. This weather pattern
will linger through the weekend. Therefore, unsettled weather
conditions are expected to prevail across Puerto Rico and the
U.S. Virgin Islands from late Friday through Sunday. Although, the
ECMWF brings low to mid-level drier air on Sunday, the GFS
solution remains wet through next week, and has the drier air mass
lingering south of the islands. Having said this, there is a
medium confidence in the forecast during the weekend, with
Saturday being the wettest day in the forecast period.

Early in the week, expect drier conditions as a surface high in
the central Atlantic strengthens and moves closer to the region.
The high is forecast to continue to promote southeasterly winds
on Monday, but as it moves closer to the area, the wind flow will
become more easterly on Tuesday and Wednesday. Therefore, a more
seasonal weather pattern is expected to return, with passing
showers moving at times across eastern Puerto Rico and the U.S.
Virgin Islands during the night and early morning hours, followed
by afternoon showers developing over western Puerto Rico.


&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, showers are expected to
develop over southwest PR btw 25/16z-22z, which should cause mostly
VCSH across the southern and western terminals. Winds are expected
to continue from the east to northeast at 12-18 kt with higher gusts
and sea breeze variations aft 25/14z.


&&

.MARINE...Choppy seas up to 6 feet will continue across the
Atlantic waters and Mona Passage today. A northerly swell will
build seas between 6 and 8 feet on Wednesday. Hazardous seas and
coastal conditions are expected until the end of the week. Northeast
trades should continue around 15 knots. There is a high risk of
rip currents for the northern and eastern beaches of PR, Culebra,
and St. Croix.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 73 84 73 / 30 40 40 40
STT 84 71 86 73 / 50 40 40 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
501 AM AST Tue Apr 26 2022

.SYNOPSIS...The surface high pressure over the western Atlantic
will continue to promote moderate to locally fresh winds for the
remaining days of the workweek. A more seasonable weather pattern
is expected to dominate through the end of the week. Throughout
the weekend, a surface trough is forecast to develop across the
eastern Caribbean, increasing showers and thunderstorms across the
local area.

&&

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

A similar weather pattern is expected to prevail through Thursday,
as the area remains under the influence of a surface high
pressure over the western Atlantic, and a deep layered low over
the central Atlantic. This will cause winds to turn more northerly
through the period, with areas of drier air and small surges of
moisture moving at times across the islands. There are 2 weak
frontal boundaries that are expected to reach the northern
sections of PR and the northern USVI, the first one late this
afternoon, and the other one by early Wednesday morning. On
Thursday, mostly drier air and stable conditions aloft should
promote fair weather conditions in general.

Therefore, a cool advective pattern should favor nighttime showers
along the windward areas of the islands, followed by afternoon
showers developing over portions of the Cordillera Central and
southern PR. No significant rainfall amounts are anticipated at
this moment through the short term period. Normal to below normal
temperatures are expected to continue across the islands.

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

A transition into a wetter pattern is forecast by Friday, as a
surface trough continues to strengthen along the eastern Caribbean,
bringing significant tropical moisture to Puerto Rico and the U.S.
Virgin Islands. As mentioned in previous discussions, this
weather pattern will linger through the weekend. Therefore,
unsettled weather conditions are expected to prevail from late
Friday through Sunday. Latest ECMWF solution shows low to mid-
level drier air filtering from the east on Sunday, and the GFS
solution remains slightly wetter through Wednesday and has the
drier air mass lingering south of the local islands. Taking this
into consideration, there is medium confidence in the forecast
during the weekend, with Saturday being the wettest day in the
forecast period.

By Monday through Wednesday, expect drier conditions as a surface
high in the central Atlantic strengthens and moves closer to the
region. The high is forecast to continue to promote southeasterly
winds on Monday, but as it moves closer to the area, the wind flow
will become more easterly on Tuesday and Wednesday. Therefore, a
more seasonal weather pattern is expected to return, with passing
showers moving at times across eastern Puerto Rico and the U.S.
Virgin Islands during the night and early morning hours, followed
by afternoon showers developing over western Puerto Rico.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, showers are expected to
develop over southern PR btw 16z-22z, which may cause brief MVFR
cigs at TJPS. Elsewhere, VCSH expected in the afternoon and once
again during the overnight hours. NNE winds are expected to
prevail between 10-16 kt.


&&

.MARINE...Choppy seas up to 6 feet will continue across the
Atlantic waters and Mona Passage today. A northerly swell will build
seas between 6 and 8 feet on Wednesday. Hazardous seas and coastal
conditions are expected until the end of the week. Northeast trades
should continue around 15 knots. There is a high risk of rip
currents for the northern and eastern beaches of PR. Other beaches
could be added later on as the breaking wave action continues to
become hazardous during the second part of the week. Starting late
tonight, there is a small craft advisory in effect through Friday.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 71 81 71 / 40 40 30 30
STT 86 75 85 75 / 40 30 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
502 AM AST Wed Apr 27 2022

.SYNOPSIS...A surface high pressure over the western Atlantic
will continue to promote moderate to locally fresh winds for the
remaining days of the workweek. A more seasonable weather pattern
is expected to dominate through the end of the week. Throughout
the weekend, a surface trough is forecast to develop across the
eastern Caribbean, increasing showers and thunderstorms across the
local area.

&&

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

A weak front over the local Atlantic waters will continue to move
southwards across the islands today. Gusty winds up to 23 mph were
observed in St. Thomas with the first band associated to the frontal
boundary, and locally higher gusts can be expected as the day
progresses. Showers associated to the front should reach portions of
northern Puerto Rico before sunset. Then in the afternoon hours,
this small surge in low-level moisture should aid in the development
of showers over portions of south-southwest PR. Mostly light to
moderate rainfall amounts are expected today. A drier air mass and
more stable conditions should prevail on Thursday and early Friday.
As PWAT decreases between 0.75-1.00 in, mostly clear skies and fair
weather conditions are expected across all the islands. Below normal
temperatures are also expected to prevail during this period.

The weather pattern is expected to gradually transition into a
wetter one by Friday evening into the weekend. As a mid-to upper-
level low over the central Atlantic induce a low level trough over
the eastern Caribbean. Winds aloft will turn more west-southwest,
while a low-level ridge over the Tropical Atlantic promotes
southeasterly winds across the eastern Caribbean. This setup will
cause pooling of deep tropical moisture across the area,
increasing the potential for flooding rains late Friday into
Saturday.


.LONG TERM...Saturday through Thursday

The forecast is currently on track. Saturday is forecast to be
the wettest day as a surface trough strengthens along the eastern
Caribbean, bringing significant tropical moisture to Puerto Rico
and U.S. Virgin Islands. Therefore, unsettled weather conditions
are expected to prevail during the first part of the forecast
period. The GFS and ECMWF are not in agreement on Sunday. The
ECMWF is bringing drier air quickly, while the GFS remains wet
through the end of the period, with the drier air mass lingering
south of the local islands. As mentioned in previous discussions,
there is medium confidence in the forecast for later in the
weekend.

Early in the workweek, expect drier air to filter into the region
as a surface high in the mid-Atlantic strengthens and moves
closer to the region. The high is forecast to continue to promote
easterly winds Monday through and Thursday. Therefore, a more
seasonal weather pattern is expected to return, with passing
showers developing at times across eastern Puerto Rico and the
U.S. Virgin Islands during the night and early morning hours,
followed by afternoon showers developing over western Puerto Rico.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, showers are expected to
develop over southwest PR btw 27/16z-22z, which should cause
mostly VCSH across the southern and western terminals. Winds are
expected to continue from the north-northeast at 10-15 kt.


&&

.MARINE...Hazardous seas up to 8 feet are expected across the
Atlantic waters and local passages today. Rough seas and coastal
conditions are expected until the end of the week. Northeast
trades should continue around 15 knots. There is a high risk of
rip currents for the northern and eastern beaches of PR including
Culebra, St. Croix,and St. Thomas. There is a small craft advisory
in effect through Saturday afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 81 73 84 74 / 20 20 20 10
STT 84 71 84 72 / 20 20 20 10

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
459 AM AST Thu Apr 28 2022

.SYNOPSIS...
Northeasterly wind flow persist, enhancing a drier weather
pattern. A strong northerly swell is influencing local seas,
raising them to heights of 10 feet and occasionally greater,
therefore High Surf Advisories, Small Craft Advisories, and High
Risk of Rip Currents are in effect. Unsettled weather is expected
this weekend as tropical moisture from southeasterly flow moves
into the region and Saturday there is a high chance for
thunderstorms and flooding to occur. Moisture values will drop
throughout next week with an easterly wind flow and there is the
potential for an upper level trough to develop over the region
before next weekend.

&&

.SHORT TERM...TODAY THROUGH SATURDAY...

A northeasterly wind flow pushed a cooler and dry air mass across
the islands, limiting rain activity overnight. Expect a similar
weather pattern through the morning hours. However, maximum
temperatures should reach the mid and upper 80s across the coastal
areas and even the low 90s on the southern coasts.

A northerly swell is creating dangerous breaking waves across the
north-facing beaches of Puerto Rico (from Rincn to Fajardo),
Culebra, St John, and St Thomas, where a High Surf Advisory is in
effect; please be aware of this coastal hazard.

Moisture will slowly increase across the islands late tonight
through the weekend. An upper-level jet will move over Puerto Rico
and the U.S. Virgin Islands through that time too. As surface winds
become more southeasterly, GFS pushes abundant moisture across
PR/USVI late Friday morning into Saturday. Thunderstorm activity
will slowly increase from the Caribbean, spreading into the islands
by Friday afternoon and Saturday. At this time, we could expect
Saturday to be the wettest day in the forecast, when urban flooding,
scattered thunderstorms, and even flash flooding and mudslides are
likely.

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

As an inverted shortwave trough continues to promotes surface to 850
mb southeast flow, tropical moisture fills into the region causing
precipitation values to be significant across the islands, with
emphasis on the eastern half of the forecast area. GFS model
guidance shows moisture variables to remain within values well above
the climatological average for the start of the the week, promoting
the continuation of rainfall over regions that previously became
saturated. By early in the week, high pressure at the surface in the
Western Atlantic begins to tighten the flow and there will be a
backing of the winds that will alter which areas will receive the
heaviest precipitation. Overall there appears to be a drying
trend compared to what was seen the previous weekend yet lower
level moisture remains around average.

In the upper levels, a weak shortwave trough north of the region may
support instability yet how far south the jet maximum reaches will
determine the influence. After this feature moves east of the region
by around late Tuesday, zonal flow will persist. The combination of
zonal flow aloft and climatologically average moisture values
indicates the return to a more recognizable seasonal pattern of
windward showers and afternoon development in western regions. Winds
are trending to become light from the southeast by the end of the
week as the aforementioned surface high pressure moves further east
into the Atlantic. Friday morning, a upper level trough will
begin to pass through Hispanola and by the the end of the day over
the local region. This has the potential to enhance instability
for another weekend of unsettled weather, therefore it`s
development will be monitored.


&&

.AVIATION...VFR conds expected to prevail through out the day across most
terminals. Showers could develop across the Cordillera Central
during the afternoon, but do not expect significant impacts to
terminals. Winds will continue from the NE at less than 10 kts
through 28/12z. Winds will increase at 10 to 15 knots with gusty
winds up to 25 kts and sea breeze variations after 28/13z.

&&

.MARINE... The combination of a strong northerly swell and wind
waves have raised seas up to 10 feet, resulting in a High Surf
Advisory until this evening. Surf heights will remain hazardous as a
second pulse of swell energy arrives on Friday. Moderate winds
continue from the east up to 15 knots with occasionally stronger
gust. There is a Small Craft Advisory in effect and a High Risk of
Rip Currents for most beaches of Puerto Rico and the U.S. Virgin
Islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 73 83 74 / 10 30 60 80
STT 85 72 85 73 / 10 50 70 80

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
515 AM AST Fri Apr 29 2022

.SYNOPSIS...
As an inverted low to mid-level trough passes through the region
tonight, thunderstorms and flooding is expected this weekend. A
typical weather pattern of windward showers and afternoon
development in the west will persist from Monday through midweek
until an upper level trough may promote unstable weather
conditions towards the end of the week. A strong northerly swell
continues to influence local waters, causing hazardous seas and
high breaking waves.

&&

.SHORT TERM...TODAY THROUGH SUNDAY...
Expect calm weather conditions through early this afternoon.
However, as we move forward in time, abundant tropical moisture will
arrive from the eastern Caribbean, increasing the risk for showers,
first across the Virgin Islands and then spreading into the eastern
third of Puerto Rico. An inverted low to mid-level trough with
plenty of tropical moisture will promote an unstable weather pattern
later this afternoon into late Saturday or early Sunday. In
addition, an upper-level jet will enhance ventilation over Puerto
Rico and the Virgin Islands, which could promote deep convection.
The synoptic pattern looks favorable for the formation of isolated
to scattered thunderstorms, especially on Saturday. At this time, we
could expect Saturday to be the wettest day in the forecast, when
urban flooding, scattered thunderstorms, and even flash flooding and
mudslides are likely.

Although the potential for showers and even thunderstorms will
persist on Sunday, the activity should slowly erode across the
islands. The main uncertainty remains on how fast this drying trend
will occur. Nevertheless, weather conditions should improve
throughout the day on Sunday.


.LONG TERM...Monday through Saturday...
Northeast of the region, the surface shortwave trough associated
with recently enhanced weather begins to weaken as a high pressure
system builds in the Western Atlantic. Winds will remain
southeast on Monday before backing to a easterly flow for most of
the week. Variable and climatologically average moisture values
are expected for the beginning of the week as patches of moist
and dry air are carried by breezy easterlies. This will provide
the typical weather regime of windward showers and afternoon
development in the west. By midweek, precipitable water values
start to gradually increase showing a wetter trend.

Currently the GFS and ECMWF forecast models do not agree on
moisture variables with the differences being around Thursday
having moist mid to upper levels values versus drier mid to upper
level values, respectively. However, as we enter the month of
May, it is reasonable that precipitation values are in a wet trend
as we exit the dry season. On Friday, GFS model guidance shows
the development of an upper level shortwave trough with it`s axis
over Puerto Rico at 00z Saturday. This feature may provide
another weekend of heavy precipitation as southeast flow brings
enhanced precipitable water values to the region. Friday appears
to have conducive variables for thunderstorm development as the
trough creates a favorable environment for vertical motion. The
potential for this to linger into Saturday is likely therefore
next weekend there is a chance for thunderstorms and flooding.

&&

.AVIATION...
VFR conditions expected to prevail through this morning. Then,
showers will slowly spread across the USVI and east-PR terminals by
early this afternoon (around 29/16z onward). This activity could
produce brief periods of MVFR conditions. An unstable weather
pattern is anticipated for the local flying area after 30/06z. Calm
to light/VRB winds will persist through 29/13z, increasing at 10 to
15 knots with higher gusts and sea breeze variations after 29/13z.
Winds will prevail mainly from the ESE-SE.

&&

.MARINE...As a northerly swell from a low pressure system
in the Central Atlantic continues to maintain wave heights up to
7 feet, local waters remain hazardous and along the coast breaking
wave heights remain high, therefore a High Surf Advisory is in
effect until Friday Evening. Expect seas to remain high into the
weekend as this swell reinforces today. Moderate winds continue
from the east up to 15 knots. There is Small Craft Advisory until
Saturday afternoon and there is a High Risk of Rip Currents for
most beaches of Puerto Rico and the U.S. Virgin Islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 76 81 76 / 40 80 90 80
STT 86 74 81 74 / 40 80 90 80

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
454 AM AST Sat Apr 30 2022

.SYNOPSIS...
Today as an inverted low to mid-level trough moves though the
region, rainy conditions will prevail across most local Islands
with the risk of urban and minor stream flooding and even
thunderstorms. This weather will persist into Sunday yet will
begin to improve as the weekend ends. Climatologically average
moisture values will provide a week of typical weather with a
drying trend beginning on the weekend. As a northerly swell is
still in the local waters, marine hazardous remain.

&&

.SHORT TERM...TODAY THROUGH MONDAY...

Weather conditions will deteriorate today as a wetter air mass moves
from the Caribbean Sea into the islands of Puerto Rico and the U.S.
Virgin Islands. The following factors: abundant moisture, an
inverted low to mid-level trough, an upper-level trough, local
topography, and low-level convergence will promote showery
conditions today. Although rainy conditions will prevail across most
islands, model guidance is now backing up or indicating less
rainfall accumulation than previous simulations. However, the risk
for urban and minor stream flooding will remain high across the
islands today. We could not rule out flash flooding across some
spots today. Some of these showers could have moderate to heavy
rain, increasing the risk of flooding. The strongest activity is
expected across eastern PR, Vieques, Culebra, and the U.S. Virgin
Islands. There is a potential to observe areas with 3 to 5 inches of
rain totals; elsewhere, between 1 and 3 inches will remain possible
through Sunday.

Although the potential for showers and even thunderstorms will
persist on Sunday, the activity should slowly erode across the
islands. The main concern continues to be on how fast this drying
trend will occur. Nevertheless, weather conditions should improve
throughout the day on Sunday.

A more seasonal weather pattern with an easterly wind flow,
combinations of clouds and sunshine, and a few passing showers in
the night and morning hours, followed by afternoon convection across
the interior and western portions, will return by Monday.

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

At the surface, a high pressure system in the Western Atlantic
promotes breezy easterly flow throughout the week. This flow will
advect patches of moisture into the region with Wednesday and
Thursday morning appearing with the best precipitable water values
according to the GFS. The previous expected wet trend starting
around the end of the week is not present in the current GFS model
run with the precipitable water and columnar RH values much lower
than previous simulations. However, GFS 250 mb heights still
indicate that an upper level trough will pass through the region
on Friday which could enhance instability.

On the contrary to previous model runs, the end of the week shows
the beginning of a drying trend that continues on past Sunday
with light winds from the southeast. A lack of moisture during the
weekend is consistent between the latest GFS and ECMWF model
runs. Therefore, A predictable weather pattern is expected
throughout the week with passing showers along windward regions
and afternoon development in the western side of Puerto Rico and
if model guidance holds true, next weekend will have fair, dry
weather as moisture values reach below climatological averages.

&&

.AVIATION...Unstable weather, cloudy skies and rainy conditions
will prevail today. -SHRA/SHRA are expected across most of the
local flying area. Prds of MVFR conds likely with BKN-OVC clds
lyrs nr FL025...FL050... FL100 and wdly SCT SHRA/ISOLD TSRA. SFC
wnds will continue calm to light and VRB bcmg ESE-SE at 10 to 15
knots with higher gusts and sea breeze variations aft 30/13Z.
Higher wind gusts btw 20-25 kts will accompany Isold/Sct-TSRA and
+SHRA.

&&

.MARINE...A weakening northerly swell has raised wave heights up to
7 feet. Moderate winds from the east continue to cause choppy
seas. As a trough moves through the region today, expect winds
from the southeast with numerous showers and isolated
thunderstorms over the local waters. There are Small Craft
Advisories in effect and a High Risk of Rip Currents Remain for
beaches of Puerto Rico and the U.S. Virgin Islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 73 82 74 / 90 70 50 40
STT 83 72 83 75 / 90 90 70 30