Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
504 AM AST Sun Jul 31 2022

.SYNOPSIS...A Saharan Air Layer and associated drier air mass will
maintain generally fair weather conditions and hazy skies through
early next week. The next rain producer is expected by Tuesday
into Wednesday, when a surface-induced trough will enhance shower
and thunderstorm development. Yet, it is not until a broader
tropical wave reaches the region by Saturday that the potential
for significant measurable rainfall and minor flooding will
increase. In the meantime, expect the typical shower pattern
highlighted by afternoon convective development over western
sections of the islands. Moderate to fresh winds will maintain
choppy to hazardous marine conditions and life-threatening rip
currents during the next few days. Above-normal heat indices are
also expected each afternoon.


&&

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

Hazy skies will prevail today due to suspended African dust
particulate. GOES-East derived Total Precipitable Water (TPW)
imagery indicated normal to above-normal water content in the
column, with TPW values between 1.59 and 1.70 inches. A surface high
pressure across the Atlantic Ocean will continue to promote windy
easterlies, advecting patches of moisture across the region from
time to time. Therefore, the moisture embedded in the trades will
promote a seasonal weather pattern, consisting of passing showers
across the windward sections and afternoon convection across the
western areas. However, expect mainly a combination of sunshine and
clouds with heat indices above 100 degrees Fahrenheit by mid-morning
into the afternoon. A similar pattern should persist on Monday.

A retrograding TUTT will approach the North East Caribbean late
Monday and Tuesday. This TUTT will induce a surface trough that
should increase moisture and the potential for showers and
thunderstorms across the islands, especially Tuesday afternoon and
early Wednesday morning

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

Based on the most recent model guidance, the weather scenario
expected in the long-term forecast cycle remains unchanged, with
the following features influencing the local weather conditions;
surface-induced trough through Wednesday, followed by a weak
tropical wave on Thursday, and yet another tropical wave on
Saturday into Sunday. Each feature will enhance shower and
possible thunderstorm activity across the area, producing
measurable rainfall. Still, it is not until the second and broader
tropical wave reaches the region, causing precipitable water
values to rise above 2.0 inches, that there may be a potential for
minor flooding. In the meantime, localized moderate to heavy rains
could lead to ponding of water on roadways and poorly drained
areas, even during periods with relatively drier air streaming
across the region. A high surface pressure meandering across the
north Atlantic Ocean will maintain a generally easterly wind flow
at 10-20 mph, but the above features will cause winds to vary
briefly in intensity and direction. Changes in the general wind
flow will also alter daytime maximum temperatures, but highs will
still peak into the upper 80s to around 90 degrees, with heat
indices into the lower to mid 100s each afternoon.


&&

.AVIATION...VFR conds expected across the local terminals. Brief
SHRA could affect the vicinity of TJSJ, TIST, and TISX but without
impacts to operations. Hazy skies will persist today, but with P6SM
visibilities. SHRA/TSRA will form along and west of the Cordillera
central and could affect the VCTY of TJBQ btwn 31/17-23Z. Winds will
remain from the E at 10 kt or less and increasing at 15-20KT with
higher gusts and sea breeze variations through 31/23Z.


&&

.MARINE...Moderate to fresh winds up to 20 knots will maintain
choppy seas up to 6 feet during the next few days. Thus, small
craft operators should continue to exercise caution. A Coastal
Hazards Message is in place due to a high risk of rip currents
continuing for beaches across the north coast of Puerto Rico. A
moderate risk of rip currents remains in place for most remaining
local beaches.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 91 79 / 30 30 30 30
STT 91 79 91 79 / 10 20 30 30

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
459 AM AST Mon Aug 1 2022

.SYNOPSIS...

Hazy skies will persist through at least Tuesday. The urban and
coastal areas of northern Puerto Rico could expect heat index
values between 100 and 111 degrees Fahrenheit. An induced surface
trough will bring some showers Tuesday. An advective pattern will
persist through the end of the work week with the arrival of a
weak tropical wave.

&&

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

As the dominant feature, a surface high pressure across the
western Atlantic will maintain east to east-northeast winds
ranging between 10 and 20 mph through most of the cycle, veering
more from the east by Wednesday as this feature moves further into
the north-central Atlantic. Ridging will remain in place through
early this afternoon, maintaining a strong trade wind cap
inversion and promoting hostile conditions for deep convective
development. However, a retrogressive Tropical Upper Tropospheric
Trough (TUTT) will slowly replace this feature, causing mid-level
temperatures to fall around -8 degrees Celsius this afternoon and
gradually weakening the trade wind cap inversion by Tuesday into
Wednesday. GOES-East Total Precipitable Water (TPW) estimates
aligned with the most recent model guidance suggest that a drier
air mass, accompanied by a Saharan Air Layer (SAL), will maintain
below-normal seasonal moisture levels ranging between 1.30 and
1.60 inches over the area. Although remaining below normal levels,
the highest moisture levels will result from the passage of a
surface-induced trough associated with the aforementioned TUTT
from Tuesday afternoon onwards. Saharan dust particle
concentrations, generating hazy skies, are expected to diminish
briefly during this period.

Due to either hostile upper-level conditions aloft or low
moisture levels, the expected shower activity should be limited.
Despite these conditions, expect afternoon shower development over
western Puerto Rico and downwind from the local islands and
isolated mountainous areas. Since the influence of the sea breeze
convergence and diurnal heating could be strong enough to break
into the inversion, there is a slight chance for isolated
thunderstorm development each afternoon. So far, significant
rainfall accumulations are not anticipated with this activity, but
ponding of water on roadways to poorly drained areas cannot be
ruled out.

Daytime high temperatures will peak into the upper 80s to the
lower 90s across lower elevations, with heat indices reaching the
mid 100s to around 110 degrees. Due to the above-normal heat
indices expected today, a Heat Advisory is in effect for the
coastal and urban areas of northern Puerto Rico. These conditions
may persist during the next few days, and Heat Advisories will be
issued accordingly.

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

The long-term forecast did not change much, and we are still
expecting the arrival of a weak tropical wave Thursday or Friday
and another tropical wave from late Saturday to Sunday. Model
guidance suggests that dry air with suspended African dust
particles surrounds these waves. Each tropical feature will
enhance shower and thunderstorm activity across the area, bringing
beneficial rainfall activity. Late Saturday night into Sunday is
the best period with a higher chance for significant rainfall when
precipitable water may increase to/or above 2.0 inches.

A high surface pressure meandering across the North Atlantic Ocean
will maintain a generally easterly wind flow at 10-20 mph. Still,
the tropical waves will cause winds to vary briefly in intensity
and direction. Changes in the general wind flow will also regulate
daytime maximum temperatures. However, each afternoon highs will
still peak into the upper 80s to around 90 degrees, with heat
indices into the lower to mid 100s each afternoon.

&&

.AVIATION...

Mainly VFR conditions will prevail across all local terminals
through the cycle. Light and variable winds will continue
through at least 01/12Z, increasing to 10-20 knots with higher
gusts and sea breeze variations by mid-morning.

&&

.MARINE...

Across the regional waters, small craft operators should exercise
caution across the Caribbean Sea and Passages where winds and seas
will reach up to 20 knots and 6 feet, respectively. Elsewhere seas
and winds will range between 3 and 5 feet and around 15 knots,
respectively.

Beachgoers, there is a high risk of rip currents for Jobos beach
in northwest Puerto Rico. The risk is moderate for most of the
beaches in Puerto Rico and the U.S. Virgin Islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 91 79 89 78 / 30 40 40 50
STT 90 79 90 78 / 20 20 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
451 AM AST Tue Aug 2 2022

.SYNOPSIS...

Traces of African dust will promote some haziness across the
islands this morning but should slowly diminish. An induced
surface trough will increase shower activity across the islands
today, especially during the afternoon. Above-normal heat indices
above 100s will continue across the urban and coastal areas of
north-central Puerto Rico and the San Juan Metropolitan area.

&&

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

A surface high pressure across the western Atlantic will maintain
east-northeasterly trades ranging between 10 and 20 mph today,
veering more from the east to the east-southeast and accelerating
by Wednesday into Thursday as this feature moves further into the
north-central Atlantic. A retrogressive Tropical Upper
Tropospheric Trough (TUTT) will set its base over the islands
today and into the Mona Passage on Wednesday. This feature will
support somewhat favorable conditions for deep convective
development, with mid-level temperatures between -5 and -7 degrees
Celsius and weak trade wind cap inversion. As ridging aloft
reestablishes over the region by Wednesday, expect the
strengthening of the trade wind cap inversion. GOES-East Total
Precipitable Water (TPW) estimates aligned with the most recent
model guidance suggest the associate surface-induced feature,
streaming across the region today, will provide additional
enhancement. This enhancement will cause moisture levels to reach
seasonal normal moisture levels at around 1.70 inches this
afternoon. After that, moisture content levels will vary
considerably, but easterly perturbations in the trades, associated
with increasing wind speeds, will cause periods with TPW as high
as 2.1 inches by Thursday evening. Saharan dust particle
concentrations, generating hazy skies, are expected to diminish
today.

The expected weather scenario should support enhanced shower
activity, accentuated by afternoon showers and possible isolated
thunderstorm development focused across southwestern Puerto Rico,
where moderate to locally heavy rains could lead to ponding of
water on roadways and poorly drained areas. Increased stability
and winds, leading to shallow, fast-moving showers, will lead to
lesser rainfall totals on Wednesday and Thursday, with peak
rainfall totals by Thursday night. Expect streamer-like showers
each afternoon downwind from El Yunque and the local islands into
eastern Puerto Rico and neighboring islands.

Once again, daytime high temperatures will peak in the upper 80s
to the lower 90s across lower elevations, with heat indices
reaching the mid to upper 100s. Due to the above-normal heat
indices expected today, a Heat Advisory is in effect for the
coastal and urban areas of northern Puerto Rico. These conditions
may persist during the next few days, and Heat Advisories will be
issued accordingly.

.LONG TERM...Friday through Tuesday.

Moisture embedded in the trades will bring quick passing showers
across the windward sections on Friday. The available moisture
combined with sea breeze variations will result in afternoon
convection across the western areas of Puerto Rico and downwind
from the Virgin Islands. A weak tropical wave will cross the
Lesser Antilles by late Friday evening, and behind it, a wind
surge will also arrive around Saturday afternoon. The bulk of
moisture of a more substantial tropical wave will promote a better
chance for widespread showers and isolated to scattered
thunderstorms Sunday. The lingering tropical moisture may promote
showery weather conditions early next week. Keep in mind that
GFS`s new solutions look moister than the previous runs.

Although the tropical waves will induce fluctuations in the main
wind flow, a surface high-pressure meandering across the North
Atlantic Ocean will maintain a generally easterly wind flow at
10-20 mph. These changes in the general wind flow will also
regulate daytime maximum temperatures. However, each afternoon
highs will still peak into the upper 80s to around 90 degrees,
with heat indices into the lower to mid 100s each afternoon.

&&

.AVIATION...

Mainly VFR conditions will prevail across all local terminals
through the cycle. Trade wind SHRA may result in brief MVFR
conditions at TJSJ, TJBQ, and TIST through 02/14Z. Except for
TJPS, where winds will remain light and variable, east-northeast
winds will continue through the cycle, increasing from 10-15 knots
to 10-20 knots with higher gusts and sea breeze variations by
mid-morning.

&&

.MARINE...

Mariners can expect moderate easterly winds across the local
waters, with locally fresh winds in some areas, especially during
the afternoon. This will sustain moderate chop to locally choppy
conditions throughout the local waters. Seas of 5 feet or less are
expected. A wind surge will bring back choppy seas across the
local waters on Thursday.

There is a moderate risk of rip currents across nearly all local
beaches, except for western Puerto Rico and most of the beaches in
St Thomas and St John, where the risk is low.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 81 90 79 / 20 30 40 40
STT 90 80 90 79 / 30 30 20 10

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
454 AM AST Wed Aug 3 2022

.SYNOPSIS...

A retrograding TUTT will induce an easterly perturbation
propagating westward across the islands today. Therefore, expect
the typical pattern of passing showers across the Virgin Islands
and windward sections of Puerto Rico followed by more intense
afternoon convection across the northwest quadrant in PR and over
San Juan due to the "El Yunque" streamer. If model guidance
remains constant, the next rain producer will be next Sunday`s
tropical wave.

&&

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

According to higher resolution models, a surface high pressure
moving further into the north-central Atlantic will promote east
to east-southeast trades ranging between 10 and 20 mph today,
increasing up to 25 mph and becoming more easterly on Thursday and
northeasterly on Friday. A retrogressive Tropical Upper
Tropospheric Trough (TUTT) will continue to move away from the
region today. This feature will be replaced by a mid-level ridge,
centered well to the north of the local islands over the north
Atlantic. The latter will gradually strengthen the trade wind cap
inversion through the rest of the cycle. Although relatively drier
air will occasionally stream across the region, perturbations
embedded in the trades will lead to a prevailing increased
moisture pattern in 16-20 hours intervals, with patches of low-
level moisture increasing precipitable water value (TPW) from 1.6
inches this morning, as depicted by GOES-East TPW estimates, to
around 2.0 inches by Thursday night. After that, expect a quick
drying pattern with the entrance of an extended area of drier air
and TPW dropping as low as 1.4 inches.

Although conditions will slowly become hostile for deep
convective development during the next few days, expect the
seasonal shower pattern, accentuated by overnight and early
morning showers moving over windward areas, followed by afternoon
shower development across western Puerto Rico. Sea breeze
convergence and daytime heating could aid in the development of
isolated thunderstorms, producing moderate to locally heavy rains
that could lead to ponding of water on roadways and poorly drained
areas. Increased stability and winds, resulting in shallow, fast-
moving showers, will lead to lesser rainfall totals from this
evening onwards. Still, increased frequency of trade wind showers
could result in significant rainfall totals by Thursday night.
Expect streamer-like showers each afternoon downwind from El
Yunque and the local islands into eastern Puerto Rico and
neighboring islands. Daytime high temperatures will peak in the
upper 80s to the lower 90s across lower elevations, with heat
indices slightly lower than previous days, peaking into the lower
to mid 100s.

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

A surface high pressure in the North Atlantic will promote breezy
trade winds Saturday through early next week. However, Saturday`s
wind surge and Sunday`s tropical wave will induce fluctuations in
the main wind flow.

Model guidance indicates a wet and unstable weather pattern due
to the arrival of a wind surge on Saturday and a robust tropical
wave Sunday/Monday. These features will interact with a TUTT
lingering near the Northeast Caribbean. The best chance to observe
scattered thunderstorms and widespread showers at this time looks
like Sunday and Monday. Subsidence behind the wave will limit
shower activity Monday night into Tuesday before the arrival of a
second wind surge Tuesday morning. Then we forecast the appearance
of a tropical wave axis late Tuesday night or early Wednesday
morning.

&&

.AVIATION...

Mainly VFR conditions will prevail across all local terminals
through the cycle. Trade wind SHRA may result in brief MVFR
conditions at TJSJ, TJBQ, and USVI terminals through 03/14Z.
Afternoon SHRA/TSRA development could also result in MVFR
conditions at TJSJ and TJBQ around 03/16-22Z. Except for TJPS,
where winds will remain light and variable, east winds will
continue through the cycle, increasing from 10-15 knots to 10-20
knots with higher gusts and sea breeze variations by mid-morning.


&&

.MARINE...

Moderate to locally fresh winds will continue to support some
moderate chops to choppy conditions across the waters. Seas of 5
feet or less will prevail until tomorrow when a wind surge
increases local winds and seas up to 22 knots and 6 feet,
respectively. Winds and seas will increase even more from Friday
onward, and we may reach Small Craft Advisory criteria on Sunday.


There is a moderate risk of rip currents for nearly all local
beaches.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 78 89 78 / 40 40 50 50
STT 91 79 89 77 / 20 20 40 40

[cycloneye]

 https://twitter.com/TTWeatherCenter/status/1554846706029760513

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
501 AM AST Thu Aug 4 2022

.SYNOPSIS...
For today, a more seasonal weather pattern is forecast. In the
morning, frequent passing showers over the local waters, windward
sections, and the surroundings of the U.S. Virgin Islands. Then,
in the afternoon hours, shower activity with isolated
thunderstorms over the western interior. On Sunday, a tropical
wave is forecast to move over the region increasing the potential
for showers and thunderstorms.

&&

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

Near normal moisture expected today with patches of slightly higher
and slightly below normal moisture through the short term period.
The model guidance has backed off in the moisture for today, with
precipitable water values between 1.5 and 1.7 inches for the most
part. This will cause isolated to scattered showers in the morning,
then more specific shower activity across eastern and western PR
with isolated thunderstorms in the afternoon. The USVI is expected
to observe brief showers through the day, but the morning showers
may be lighter than the brief showers expected in the early
afternoon hours. The wind speed is expected to increase to around 15
to 20 mph today as the day progresses, so the locally induced
showers and thunderstorms this afternoon will be across a small
portion of western PR and then over the waters west of PR. The
showers across eastern PR in the afternoon may be mostly due
streamers from the USVI, Vieques and Culebra. In the upper levels,
conditions will become less conducive fore widespread convective
activity as the TUTT moves north and away from the local area. The
trough in the mid levels is also expected to move away today. By
tomorrow, zonal flow is expected in the mid levels. That said,
patches of moisture will continue tomorrow and on Saturday, but less
coverage of shower activity is expected compared to what is
expected today.

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

The surface pattern will be dominated by a high pressure located
across the center of the Atlantic. This high pressure will result
in easterly winds on Sunday through Wednesday. In these easterly
trade winds, moisture associated with a tropical wave will move
through the region between Sunday and Monday. Due to broad high
pressure, the bulk of moisture is expected to remain south of the
island on Sunday, increasing further on Monday as the tropical
wave turns northeastward into the southwest Atlantic. In addition
to an increase in winds, according to the NASA Goddard Earth
Observing System Model, an increase in Saharan dust is expected.
Therefore, there is a potential for frequent showers, and isolated
thunderstorms are expected for portions of the forecast area from
Sunday through Monday due to the above mentioned conditions.

As the high pressure builds across the central Atlantic, a mix of
dry air and some patches of moisture are expected to change
rapidly with the arrival of a wind surge on late Tuesday into
Wednesday. By Wednesday, we could be seeing typical seasonal
showers across parts of the interior west and the AM passing
showers in the windward sections. A slight shift in surface winds
from east to east-southeast is expected on Thursday as the high
pressure weakens and moves a bit more toward the northeast
Atlantic. This slight change in wind direction will make
temperatures slightly warmer across the north and north central
sectors on Thursday and Friday.

&&

.AVIATION...
VFR conds expected through the forecast period. SCT SHRA
will cause VCSH across the local terminals through 04/15Z.
Thereafter, SHRA/ ISOL TSRA could affect areas near the vicinity of
TJBQ and TJSJ. Winds will be increasing this morning, at around 15
KT and gusty by 04/14Z, but at 20 KT or so by 04/16Z with higher
gusts, from the east, with some sea breeze variations.

&&

.MARINE...

A broad high pressure over the northeastern Atlantic will continue
to result in moderate to locally fresh easterly winds across the
forecast area. This increase in winds will turn choppy seas for
all the local waters today into tonight. Therefore, small craft
operators are urged to exercise caution today into tomorrow. A
slight improvement is forecast for tomorrow when winds slightly
decrease for some areas. On Sunday, marine conditions are forecast
to deteriorate again, with a tropical wave arrival. There is a
high risk of rip currents for the northwestern exposed beaches of
Puerto Rico; for the rest of the areas, the risk will remain low
to moderate.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 77 90 78 / 40 50 50 40
STT 89 76 90 78 / 40 40 40 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
457 AM AST Fri Aug 5 2022

.SYNOPSIS...
Passing showers are forecast to prevail through the morning hours
across the windward sections of the islands and across the local
waters. In the afternoon, another round of showers is expected
over the western interior section of Puerto Rico. Heat indices are
forecast to reach 100 to 105 degrees for the north- central coast
of Puerto Rico. Due to moderate to locally fresh winds, choppy
marine conditions are forecast to remain. Weather conditions are
forecast to deteriorate on Sunday as a tropical wave moves into
the forecast area.

&&

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

Near normal moisture expected today with patches of above and below
normal moisture through the short term period. The model guidance
has backed off in the moisture for today, with precipitable water
values between 1.3 and 1.7 inches today and Saturday, but deeper
moisture is expected to move in on Sunday as a tropical wave moves
in. The weather pattern expected today and Saturday will cause
scattered showers across the local waters, USVI, and eastern PR
through the day. Locally numerous showers with isolated
thunderstorms are forecast across western PR in the afternoons. For
Sunday, with the deeper moisture that will move in with the tropical
wave, the shower activity will be more persistent for eastern PR and
the USVI, while some afternoon shower and thunderstorm activity is
expected for western PR. However, the global model guidance is not
very aggressive with the rainfall totals, but the hi-res models do
put the heavier rain for eastern PR, with lower amounts across the
USVI and elsewhere in PR.

The wind speed is expected to increase during the daytime to around
15 to 20 mph, so the scattered shower activity is expected to be
relatively brief over any one area.

In the upper levels, conditions will become less conducive for
widespread convective activity today and Saturday as a TUTT moves
north and away from the local area, but another TUTT will move
closer to the local islands by Sunday afternoon. Zonal flow is
expected in the mid levels in the short term period, with a high
pressure across the northwest Atlantic.

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

A variation in weather conditions is expected for the long term
period. Monday through Tuesday, the main feature at the surface
will be a broad localized high pressure across the Central
Atlantic. This high pressure will cause an easterly wind flow
through the region. Embedded in these winds, fragments of moisture
associated with a tropical wave passing to the south of the area
will reach the islands, increasing the potential for shower
activity. Most of the moisture is expected on Monday, generating
localized showers and thunderstorms across western sections of
Puerto Rico. At the upper levels, a tilted trough located to the
north of the islands is expected to create some instability,
sufficient for developing some localized heavy showers. As
moisture from the tropical wave moves out of the region,
considerable improvement in weather conditions is expected on
Tuesday, with only a few brief showers in the morning across the
windward sections and the typical afternoon activity product of
the local effects.

Some changes are forecast for the upper levels on Wednesday into
Friday.The upper level trough will be replaced by an upper level
ridge moving westward, establishing just to our east. The
subsiding side for this high pressure aloft might slightly
increase the potential for some showers. The high pressure at the
surface will diminish and create more moderate winds across the
CWA. On Wednesday, a wind surge is forecast to move into the
region, increasing the values of the precipitable water across the
area. According to models guidance, conditions will rapidly
change on Thursday as a dry air mass filter, with Pwat values
​​below normal weather conditions, resulting in fair weather
conditions for most of the region. This pattern is expected to
change with another round of showers across the area due to the
approach of another tropical wave moving into the area on Friday.


&&

.AVIATION...VFR conds expected through the forecast period. SCT SHRA
will cause VCSH across the local terminals through 05/14Z. SHRA
could affect areas near the vicinity of TJBQ and TJSJ after 05/16Z.
Winds will be increasing this morning, at around 15 to 20 KT and
gusty by 05/14Z from the east, with some sea breeze variations.

&&

.MARINE...

A high building pressure over the eastern Atlantic will continue
to result in moderate to locally fresh easterly winds across the
forecast area today into Saturday. Those winds will turn choppy
seas for all the local waters, with seas up to 6 feet for the
offshore Atlantic waters. Therefore, small craft operators are
urge to exercise caution. On Sunday, marine conditions are
forecast to deteriorate again when a tropical wave moves into the
forecast area. There is a high risk of rip currents for the
northwestern into the north-central exposed beaches of Puerto
Rico, as well Kramer Park In St. Croix; for the rest of the areas,
the risk will remain low to moderate


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 91 78 89 78 / 40 40 30 50
STT 91 79 90 79 / 40 30 30 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
452 AM AST Sat Aug 6 2022

.SYNOPSIS...
Recent satellite imagery shows some patches of cloudiness and
moisture moving into the forecast area. This pattern will lead to
the usual passing showers in the morning for the eastern sections
of the islands, the U.S. Virgin Islands, and the local waters.
Weather conditions are forecast to deteriorate later tonight into
Sunday, with the arrival of moisture from a tropical wave moving
just to our south.

&&

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

Near normal moisture expected today with patches of above and below
normal moisture through the short term period. The model guidance
has precipitable water values between 1.3 and 1.7 inches today, with
the patch of deeper moisture moving in this afternoon. This will
cause showers and thunderstorms in the afternoon across western PR,
while isolated to scattered brief showers are possible elsewhere. A
tropical wave is expected to move in on Sunday, increasing moisture
over a larger area. This may cause scattered showers with isolated
thunderstorms across the local waters, USVI, and eastern PR through
the day, while showers and thunderstorms are possible across western
PR on Sunday afternoon. However, some model guidance has backed off
even more in the amount of rain, especially the GFS and NBM model,
but the ECMWF ensembles still have decent amounts of rain. Therefore
some lowering in the PoPs were done but didn`t reduce too much as
there is obviously still some uncertainty. Drier air will move in on
Monday after the tropical wave, causing very little, if any, shower
activity and perhaps some Saharan dust.

The wind speed is expected to increase during the daytime hours each
day to around 15 to 20 mph.

The daytime high temps will be near normal today and Monday, but
Sunday could be a couple of degrees below normal as cloudiness and
some shower activity is expected.

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

At the surface, a mixture of some tropical waves and drier airmass
patches are forecast for the long term. Meanwhile, high pressure
aloft will result in stable and drier conditions in the upper
levels for most of the period.

On Tuesday, a broad high pressure located over the central
Atlantic moving westward into the western Atlantic will be the
dominant feature through at least Thursday. Embedded in the trade
winds, a slot of drier airmass with precipitable water below the
climatological normal will limit the widespread shower activity.
Conditions start to deteriorate late Tuesday into Wednesday when a
wind surge moves into the area and increases the cloud coverage
and humidity. This increase will mainly cause the typical weather
pattern across Puerto Rico and the U.S. Virgin Islands, with the
AM passing showers followed by the afternoon convection over the
interior and western Puerto Rico. So far, expect ponding of water
in roadways and poor drainage areas, as well minor flooding in
urban areas.

In the evolving pattern, surface conditions are forecast to change
on Thursday, when the high surface pressure moves westward into
the western Atlantic, replaced by a building surface high pressure
over the tropical eastern Atlantic. This change in the pattern
will affect the wind pattern over the area, turning more east-
southeasterly winds on Thursday afternoon. With the available
moisture and local effects, this wind pattern is forecast to
result in some afternoon convection over the northwestern quadrant
of Puerto Rico and the San Juan Metro. On Friday, another round
of drier air and stable conditions will prevail, changing rapidly
with the arrival of the leading edge of the next tropical wave on
late Friday into Saturday.


&&

.AVIATION...VFR conds expected through the forecast period. SCT SHRA
will cause VCSH across the local terminals through 06/14Z. Winds
will be increasing this morning, at around 15 to 20 KT and gusty by
06/14Z from the east, with some sea breeze variations.

&&

.MARINE...

A broad high pressure over the central Atlantic will continue to
result in moderate to locally fresh easterly winds across the
forecast area today. Therefore, expect choppy seas for all the
local waters, with seas up to 6 feet for the offshore Atlantic
waters. Therefore, small craft operators are urge to exercise
caution. By late tonight, marine conditions are forecast to
deteriorate again as a tropical wave moves into the forecast
area, with seas up to 7 feet across the offshore Atlantic waters,
and Anegada Passage, where a small craft advisory is in effect
from 2 AM AST Sunday. There is a high risk of rip currents for the
northwestern and Kramer Park In St. Croix, extending into the
north-central exposed beaches of Puerto Rico at 8 AM AST today.
The risk for other local beaches across the north coast and
Culebra will increase tonight.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 91 79 90 77 / 40 50 60 20
STT 94 79 91 78 / 40 50 50 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
434 AM AST Sun Aug 7 2022

.SYNOPSIS...
A tropical wave will continue to move across the area today,
bringing an increase in shower and thunderstorm activity to the
area, along with gusty winds. Drier weather is expected for the
beginning of the workweek, along with some Saharan dust.

&&

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

Satellite and radar images indicate the arrival of the leading edge
of the next tropical wave already moving through the region.
According to GOES-16 Total Precipitable Water, moisture values
​​are about 1.7 inches over the islands, with the bulk of the
moisture over the Caribbean waters with values around 2.1 inches.
As the day progresses, the axis of the wave is expected to move
closer to the region, gradually increasing the potential for
shower and thunderstorm activity. This activity will bring gusty
winds, especially with the heaviest showers for portions of the
eastern third of Puerto Rico, the US Virgin Islands, and along the
local waters. In addition, diurnal-induced convective activity
will affect sections of the interior and western Puerto Rico this
afternoon into the early evening hours.

As the moisture from the previous tropical wave moves out of the
region, a drier trend is forecast to begin late Monday in the
afternoon through Tuesday afternoon as a drier air mass with
Saharan Dust particles filters into the region. According to the
NASA Goddard Earth Observing System Model, the bulk of the Saharan
particles will be on Monday. Although weather conditions will not
be conducive for widespread shower activity, afternoon convection
will still be possible, mainly focusing on western sections of
Puerto Rico, and less activity expected for the eastern areas.
Temperatures should remain typical for the season with highs in
the low 90s and heat indexes in the low 100s. By Tuesday, the
frequency of showers is forecast to increase as a a wind surge
drags another patch of enhanced moisture.

.LONG TERM...Wednesday through Sunday...
A mid to upper level ridge continues to hold northeast of the local
islands. Due to the anticyclonic flow created by the upper level
high, winds at these levels will be from the south, with moisture
being dragged from the Caribbean Sea that could aid in the
development of high clouds. At the mid-levels, dry air will dominate
through the end of the workweek. On Wednesday, however, a modest
increase in showers is expected as a tropical wave moves south of
the islands. There is some Saharan dust embedded within the
airmass that may result in hazy skies. Even with the limiting
factor of the dry air in the mid-levels, afternoon convection is
still expected to develop across western Puerto Rico due to local
effects. Additionally, occasional patches of moisture dragged by
the trade winds may bring some passing showers for eastern Puerto
Rico and the Virgin Islands. By the end of the workweek, while the
mid-dry air layer remains, the upper level ridge collapses in
response to an upper level trough north of the Bahamas, which
could promote better conditions aloft for thunderstorm
development.

For the weekend, uncertainty increases in the forecast. First of
all, the GFS shows a tropical wave crossing the area on Saturday,
which could increase the potential for some showers. However, the
ECMWF shows the continuation of generally dry air covering the
northeastern Caribbean. The global models due agree in the formation
of a tropical cyclone that should remain north of the local islands.
Based on the current guidance, the main weather impacts will be a
weaker low level wind flow. However, the bulk of the moisture
associated with this system should remain far away from the
islands. Since this a long-term forecast, the users should pay
attention to the progress of this system as adjustments could be
introduced later in the week.

&&

.AVIATION...VFR conditions are expected across most of the TAF
sites. A tropical wave moving to the area will result in SHRA and
VCTS for TIST, TISX, TJSJ, and TJBQ, causing some briefly MVFR
conditions with the heaviest activity. Low-level winds winds are
from the E at 10 kts with some gusty wind, increasing at 07/14Z up
to 15 to 20 KT, with seas breeze and some higher gusty winds. Some
VCTS are possibles across TJPS in the late afternoon hours.


&&

.MARINE...
Increasing winds will create choppy to hazardous seas today along
the Anegada Passage and the Atlantic waters through the day, with
seas rising up to 7 feet. Winds of 20 to 25 knots are also
anticipated for the Atlantic coastal waters north of Puerto Rico.
As a tropical wave moves trough, squally weather is also
anticipated for the local waters.

For the beaches, there is a high rip current risk for the northern
coast of Puerto Rico, Culebra and St. Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 78 90 78 / 50 50 40 40
STT 91 79 90 78 / 60 30 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
545 AM AST Wed Aug 10 2022

.SYNOPSIS...

High temperatures and maximum heat indices in the low 100s will
continue through the workweek. A weak perturbation will move across
the forecast area today through Thursday increasing the potential
for some showers with a chance of isolated thunderstorms over the
regional waters and mainly western Puerto Rico. Lingering Saharan
dust will result in slightly hazy skies through the end of the
week. A tropical wave is forecast to move across the region on
Saturday followed by a stronger and vigorous tropical wave late
Sunday through Monday.

&&

.SHORT TERM...Today through Friday
A mid to upper level ridge continues to hold east of the Lesser
Antilles. The circulation of the upper level high is causing winds
to shift from the southwest at these levels, which is bringing some
high level clouds with it. The mid level high is sustaining a trade
wind cap inversion around 800 mb. At the low levels, infrared satellite
imagery shows an easterly perturbation advancing into the local
islands. A narrow band of showers was evident in the Doppler radar,
with the bulk of the activity crossing the Atlantic waters. The
low level moisture associated with this feature should combine with
local effects to generate showers this afternoon across western
Puerto Rico. With enough diurnal heating, isolated thunderstorms
cannot be ruled out. Ponding of water on roadways and low-lying
areas will be possible with this activity.

East of this perturbation, the air mass looks drier, with Total
Precipitable Water from GOES-16 showing values around 1.3 inches.
This is below the climatological value, so once this air mass
filters in, the probability of precipitation will decrease. This
period of fair weather should not last too long, since a tropical
wave wave should cross the Caribbean Waters early Thursday. The mid
and upper level ridge will also weaken in response to a trough
digging in from the north. With the available moisture and better
support aloft, the potential for isolated thunderstorms increases.
In the afternoon hours, widespread activity is anticipated, with the
stronger convection developing across the Cordillera Central,
northern and northwestern Puerto Rico, and downwind from El Yunque
and from the Virgin Islands.

Once this wave departs into the central Caribbean, another drier air
mass will filter in across Puerto Rico and the U.S. Virgin Islands.
Some saharan dust will be embedded within the air mass, hence skies
could turn hazy. Under an easterly wind flow, near normal or just
above normal temperatures will persist into the area. This in
combination with dewpoints between 75 and 80 degrees, heat indices
will soar between 102 to 107 degrees today, and a little higher
through the end of the workweek.

&&

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

As previously mentioned the drier airmass is expected across the
region on Friday, but a weak tropical wave will quickly move
across the region on Saturday. This will bring an increase in
moisture and better chance for showers and isolated thunderstorms
mainly over the coastal waters and the west sections of Puerto Rico
and the U.S. Virgin Islands during the afternoon hours. Some saharan
dust and breezy conditions will accompany this wave, but widespread
showers and thunderstorm activity is not expected during the day.
However, by late Sunday and through Monday of next week, recent model
guidance continued to suggest increasingly moist and unstable conditions
with the arrival of a strong and more vigorous tropical wave, which
will affect the region through at least Tuesday due to trailing moisture.
That said the potential widespread showers and isolated thunderstorms
will increase as guidance continue to suggest precipitable water values
to exceed 2.0 inches during that time. Consequently urban and small
stream flooding will be likely across the islands with the best chance
late Sunday or early Monday through Tuesday. Additionally, as the wave
crosses the region by Monday, the low level winds are expected to shift
and become more southerly resulting in sufficient moisture being lifted
up across the region favoring afternoon convection each day along with
maximum heat indices above the 100 degrees in some area. By Wednesday
conditions are expected to gradually improve. Please stay tuned and
continue to monitor as this so far expected weather pattern unfolds.

&&

.AVIATION...Mainly VFR conditions expected to persist through the
forecast period. Some Saharan dust remains, but VIS are expected to
remain P6SM. VCSH are expected to develop around TJBQ after 17Z with
brief periods of low ceilings possible. Winds will be out of the
east at 10 to 15 knots, with stronger gusts due to sea breezes.
Winds are expected to slow down after 10/23Z.

&&

.MARINE...Recent data from the surrounding buoys suggest seas
will continue up to 5 feet and mainly from the E between 10 to 20
knots. Marine conditions will continue to gradually improve
throughoutthe day, but will remain choppy for the rest of the
work week especially over the offshore waters and local passage,
where small craft operators should exercise caution.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
&&

$$

SHORT TERM...ERG
LONG TERM....RAM
AVIATION...ERG

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
502 AM AST Thu Aug 11 2022


.SYNOPSIS...
A weak tropical wave will cross the eastern Caribbean today bringing
with it quick surge of low level moisture and accompanying trade wind
showers to the region. Following the passage of the wave, winds will
become southeasterly and persist through Friday when a hot and drier
airmass is forecast. Lingering Saharan dust particulates will result
in slightly hazy skies with maximum heat indices expected to soar into
the elevated risk threshold exceeding 107 degrees along portions of
the north section of Puerto Rico. Another tropical wave is forecast
to quickly cross the region with an accompanying wind surge on Saturday
followed by an active and more vigorous tropical wave late Sunday through
Monday. Trailing moisture forecast to affect the region through Tuesday.
Light to moderate concentrations of suspended Saharan dust particulates
will persist through the period.

&&


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

A weak tropical wave will cross the local area today, although with
the best moisture remaining over the Caribbean Sea. The wave is
evident in satellite imagery, with Total Precipitable Water from
GOES-16 showing values around 1.6 to 1.9 inches. Scattered showers
are expected to move in along the eastern municipalities of Puerto
Rico during the day, leaving wet roads and ponding of water in low-
lying areas. At the upper levels, a trough centered north of Cuba is
creating a southwesterly wind flow, dragging some upper level clouds
from the south and providing ventilation aloft. The effect of the
trough will combine with the low level moisture to generate
widespread shower activity and isolated thunderstorms this
afternoon. The National Blend Model and the high resolution models
have the bulk of the activity focusing over the interior and
northwestern quadrants of Puerto Rico, with a secondary bullseye
developing from El Yunque and moving toward the San Juan metro area.
Additional streamers may develop from the isles and move over
sections of eastern Puerto Rico. With the strongest activity, urban
and small stream flooding will be possible.

Once the tropical wave departs, a drier air mass will filter in.
This air mass carries slight amounts of Saharan dust, so hazy skies
can be anticipated at times on Friday. For Saturday, some adjustment
to the forecast were introduced. In the last few cycles of the GFS,
the trend was pointing toward a weaker solution for the wave
arriving on Saturday. Now, it only appears as a narrow swath of
moisture crossing the local islands, trapped between two pockets of
Saharan dust. Regardless, with enough diurnal heating, and still
under the influence of the upper level trough, some showers should
fire up in the afternoon for the interior and western Puerto Rico.
Additionally, passing showers should cross the rest of the area,
especially in the morning hours.

In terms of temperatures, near normal or just above normal highs are
expected to prevail. These values in combination with dewpoints in
the upper 70s and low 80s, will result in heat indices above 102
each day. The areas with the highest heat indices in the forecast
are the municipalities of north-central Puerto Rico, but other
areas, including the Virgin Islands, will experience elevated heat
indices as well.

&&

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

So far recent model guidance continue to initialize fairly well and
still suggests that by late Sunday and through Monday of next week,
a significant increase in instability and moisture content is forecast
for the region. If this continues to unfold, this wave should bring
increasingly moist environment to the region and thus favor unstable
conditions with good potential for early morning and afternoon convection
across the islands, with increasing cloudiness, showers and isolated
thunderstorm development likely through at least Tuesday. Therefore
with the expected weather pattern, the potential for widespread showers
and thunderstorm development will remain high due to the increasing
instability, the proximity of an upper level trough, and good
moisture convergence with the layered precipitable water values
exceeding 2.0 inches during that time.

Under this moist and unstable environment urban and small stream flooding
as well as ponding of water on roads and poor drainage areas will be
likely across the islands, with still the the best chance late Sunday
or early Monday through Tuesday. As this active wave crosses the region,the
low level winds are expected to shift and become more southeasterly
resulting in sufficient moisture being lifted up across the region
favoring afternoon convection each day along with maximum heat indices
above the 100 degrees in some area. By Wednesday and Thursday conditions
are expected to gradually improve as winds become more easterly and
a drier and more stable airmass filters in. This will lead to the more
typical summertime weather pattern. Stay tuned and continue to monitor
as this expected scenario unfolds and some adjustment in timing may
be needed.

&&

.AVIATION...

Mainly VFR conditions are expected to prevail through the forecast
period. VCSH are expected for TJSJ and the USVI terminals through
early in the period. After 17Z, VCTS are expected for TJBQ AND TJSJ.
These could result in periods of reduces VIS and low ceilings.
Mountain obscuration along the Cordillera Central is also expected
after 17Z. Winds will be out of the east at 10 to 15 kts, with
stronger gusts within the showers and thunderstorms, and due to sea
breezes.

&&

.MARINE...

Moderate to fresh easterly winds up to 20 knots will continue across
the local waters and passages. Small craft operators should continue
to exercise caution. Seas will continue at 5 feet or less today
Friday. There is a moderate risk of rip current across most
locally exposed beaches, except for those across the western coast
of Puerto Rico and St. Thomas. An increase in showers and thunderstorms
is expected over the regional waters today with the passages of a
tropical wave and afternoon shower activity over western Puerto
Rico.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 11 AM this morning to 4 PM AST this afternoon
for PRZ001-005.

VI...None.
&&

$$

SHORT TERM...ERG
LONG TERM....RAM
AVIATION...ERG

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
458 AM AST Sat Aug 13 2022


.SYNOPSIS...

A weak tropical wave will cross the eastern Caribbean today bringing
with it quick surge of low level moisture and accompanying trade wind
showers to the region. Then a robust tropical wave is expected to
reach the forecast area on Sunday night increasing the potential
for shower and thunderstorm activity. High humidity and southerly
wind flow will promote hot weather and high heat indices through
early next week.

&&

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

High pressure at lower levels is centered over the central north
Atlantic ocean and will drive generally east northeasterly trade
winds across the area. At mid levels the high pressure was just over
1500 miles east northeast of San Juan, Puerto Rico and will drift
west to a position about 500 miles northeast of San Juan by Monday
evening. At upper levels a Tropical Upper Tropospheric Trough (TUTT)
is northwest of the area. It will be partially absorbed into a long
wave trough over the United States but the remnants will ride over a
weak ridge to a position northeast of the area. This will result in
weak forcing and generally light upper level flow.

A dry airmass was centered over and south of Puerto Rico early this
morning at 13/07Z. It is slowly moving westward as a tropical wave,
roughly extending from 10 N 60 W to 22 N 53 W approaches the area.
The tropical wave will induce northeasterly flow at lower levels as
early as this morning which will continue with natural diurnal
fluctuations until the wave passes. The wave is expected to cross
the U.S. Virgin Islands late Sunday and all of Puerto Rico Monday
morning. The best moisture will be behind the wave, but owing to its
fairly rapid movement, drying will begin Monday evening.

The GFS has favored this tropical wave in previous runs with good
vertical motion and deep moisture, but in the last run from 13/00Z
moisture is limited and the best moisture remains below 850 mb.
Its forecast of precipitable water is more dramatic, with a rise
from about 1.1 inches to 2.25 inches between Friday evening (last
night) and Monday noon. Nevertheless the high pressure at mid and
upper levels tend to work against expectations of prolonged heavy
rains for the area. Some local urban and small stream flooding is
likely however due to local effects Monday afternoon. The pronounced
flow from the south southeast at 850 mb will favor convection during
the afternoons along the northern coastal plains of Puerto Rico,
although orographic effects will also bring better rains to the
south slopes of the ridges of the island. A mass of Saharan dust is
following the tropical wave, but it is fading and is not expected to
be a major concern late Monday.

&&

.LONG TERM...Tuesday through Saturday

Columnar moisture is expected to drop on Tuesday after the passage
of a vigorous tropical wave from the previous day. However,
lingering low-level moisture will remain within climatological
normal levels with precipitable water fluctuating between 1.6 to
1.7 inches during the day. Therefore, early morning showers will
affect the eastern portions of Puerto Rico and U.S. Virgin
Islands. Showers will also be affecting the local waters,
especially western local waters as the tropical wave continues its
westward retreat. Instability aloft will be marginal, enough for
afternoon showers and isolated thunderstorms to develop as
lingering moisture combines with diurnal heating and sea breeze
convergence. Under a southeast to east southeast wind flow, the
activity will be concentrated over the northwestern quadrant of
Puerto Rico. Fast steering wind flow could promote streamers
downwind of the local islands and El Yunque into the San Juan
Metropolitan area. Ponding of water in roadways and in low-lying
areas and localized urban flooding will be possible with this
activity.

Given the aforementioned wind pattern, temperatures will be
seasonably hot on Tuesday, possibly reaching the highest maximum
temperatures of the week. Combined with the available moisture,
heat indices could reach 110 degrees in urban and coastal areas
especially across the north central municipalities of Puerto Rico.

The low-level wind pattern is forecast to shift east northeast on
Wednesday and remain mainly easterly throughout the week into the
weekend. A mid to upper-level ridge will hold through most of the
workweek promoting a weak inversion cap between the 750-800 mb
layer. Therefore, expect mostly a seasonable weather pattern by mid-
week through the rest of the workweek with morning showers across
windward coastal areas and diurnally induced afternoon showers
mainly across western Puerto Rico. Thunderstorm activity, if any,
should be localized and brief.

By the end of the week into the weekend, the proximity of a weak
upper-level low is forecast to combine with an approaching tropical
wave and accompanying wind surge. However, forecast confidence is
low due to existing discrepancies between global models regarding
instability and available moisture.

&&

.AVIATION...
(06Z TAFS)

VFR conds expected thru 13/17Z. Sfc winds by 13/14Z ENE
12-18 kt with gusts to 26 kt in sea breezes. Aft 13/17Z sct SHRA/
isold TSRA expected to form until arnd 13/21Z. Aft 13/21Z sct SHRA
expected to mov into FA and across TISX ahead of apchg trop wave.
Aft 13/22Z sfc winds bcmg ENE less than 12 kt with some land breeze
influences. Max winds SW 25-35 kts btwn FL350-410.

&&

.MARINE...

Mariners can expect calm conditions with seas below 5 feet and winds
around 15 knots. Thunderstorms may develop across the western
coastal waters of Puerto Rico during the afternoon hours today.
Beachgoers, the risk of rip currents is moderate for the north and
eastern beaches in Puerto Rico, elsewhere the risk is low.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
&&

$$

SHORT TERM...WS
LONG TERM....CVB
AVIATION...WS

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
441 AM AST Sun Aug 14 2022


.SYNOPSIS...
High temperatures and an increase in humidity will cause heat
indices to reach 111 degrees Fahrenheit today in several urban
and coastal sections in Puerto Rico. Therefore, a Heat Advisory is
in effect for those areas. An approaching tropical wave will
bring unsettled weather conditions today and Monday increasing the
potential of urban and small stream flooding.

&&

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

The tropical wave, with an axis stretching from 11 N 63 W to 21 N 56
W continues to advance through the flow generated around the high in
the central Atlantic. A ridge from this high will build southwest
into the area behind the tropical wave and said wave is expected to
roll through the forecast area Sunday night and Monday. Upper levels
are most supportive of this wave on Monday, but high pressure at
upper levels will rule the forecast Monday and Tuesday.

High levels of moisture are seen in the Total Precipitable Water
Product from the GOES satellite several hundred miles east of the
area, with amounts seen up to 2.1 inches, while San Juan is running
just under 1.5 inches and southwest Puerto Rico 1.3 inches. A lobe
of the best moisture is currently about 100 miles north northeast of
Guadeloupe. The GFS shows it crossing northeast of the northern U.S.
Virgin Islands and eastern Puerto Rico, with a band of moisture
extending southwest expected to move into Puerto Rico around 15/06Z
Sunday night. The best moisture, however is not expected until after
12Z Monday morning and timing on this portion of the wave has
changed little in the last 48 hours.

Time height sections of relative humidity over San Juan show a
rapid build-up in relative humidity over the station lasting
between 15/12Z to 16/00Z, but negative vertical velocities--that
is downward vertical motion--are also depicted up to 775 mb due to
flow that becomes nearly south, and downslope on the north coast,
which is concerning for an event that was supposed to be a heavy
rain-maker. Currently there is no high-topped convection within
450 miles upstream from the forecast area, although some
intensification of the wave and convective activity is expected as
the wave approaches the area. For this reason, expectations have
been eased downward somewhat for this package, but will still hold
up to 2.0-2.5 inches for both western and eastern Puerto Rico
with isolated areas receiving more than 4 inches during the 48
hours from 14/00Z to 16/00Z. The best rainfall is expected on
Monday and will likely bring ponding on roads and poorly drained
areas and local urban and small stream flooding then. Late Monday
afternoon, drier air at low levels is expected to cross into the
U.S. Virgin Islands and eastern Puerto Rico, with local 850 mb
relative humidities dropping below 50 percent. This drying trend
will spread across the area overnight and Tuesday, but conditions
will still favor local convection with showers and thunderstorms
in western Puerto Rico that could still leave more than 1 inch in
western or northwestern Puerto Rico Tuesday afternoon.
Southeasterly winds will bring warmer temperatures today and
Tuesday to the north coast and will bring little relief to the
south coast. Heat advisories have been issued for these areas and
are likely to be repeated--if not on Monday then at least on
Tuesday.

&&

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

Mid-week maximum temperatures are forecast to be a bit lower than
previous days as winds shift more out of the east and remain so for
the rest of the long-term period. Subtle movements of the surface
high pressure across the central Atlantic will result in some
deviations in the wind direction shifting between east southeast to
east northeast through the weekend. Weather-wise, both ECMWF and GFS
models continue to have small changes between cycles with GFS having
a weak tropical wave passing late Thursday through Friday and ECMWF
having the slightly moister day by the weekend. However, moisture
content at low levels will remain within climatological normal
levels. Dynamics should also remain fairly seasonable, with ridging
aloft dominating most of the period, with a few weak upper short-
wave troughs crossing the area from time to time. This will
result in 500 mb temperatures to fluctuate between -6 to -5
degrees Celsius. Therefore, a blend of both model solutions was
taken into account and POPs were adjusted accordingly. Overall, a
seasonal weather pattern is expected to prevail for the rest of
the week into the weekend with diurnally induced afternoon showers
and thunderstorms mainly across western Puerto Rico with late
night and morning showers over windward coastal sections of the
local islands. Each day, ponding of water in roadways and in low-
lying areas are anticipated with the possibility of minor urban
and small stream flooding in localized areas with the heaviest
showers, mainly out west during the afternoon hours.

&&

.AVIATION...
(06Z TAFS)

VFR conds expected thru 14/17Z. Sfc winds by 14/14Z ENE
12-18 kt with gusts to 26 kt in sea breezes. Aft 14/17Z sct SHRA/
isold TSRA expected to form until arnd 14/22Z. Aft 14/21Z sct SHRA
expected to mov into FA and across TISX/TIST ahead of apchg trop
wave. Aft 14/22Z sfc winds bcmg E less than 12 kt with some land
breeze influences. Max winds SW 35-40 kts btwn FL400-425.

&&

.MARINE...Seas and winds will remain at 5 feet and 15 knots or
below. However, locally hazardous marine conditions are possible
near the shower and thunderstorm activity as a tropical wave
approaches the local waters today and tomorrow.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
for PRZ001-003-005-007-008.

VI...None.
&&

$$

SHORT TERM...WS
LONG TERM....CVB

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
530 AM AST Tue Aug 16 2022

...New SYNOPSIS, AVIATION, MARINE...

.SYNOPSIS...

Southeast flow and rather warm temperatures will bring showers and
isolated thunderstorms to the northern half of Puerto Rico. Low
level flow then turns more easterly and a more typical summertime
pattern ensues. Showers and thunderstorms are expected each
afternoon in western and interior Puerto Rico, with showers in
eastern Puerto Rico mostly in the mornings. Generally isolated
showers are in store for the U.S. Virgin Islands with downstream
afternoon showers. Winds remain gentle today and tomorrow and
then become more moderate as trade winds strengthen.

&&

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

The axis of an elongated tropical wave is currently over
Hispaniola with a weakening surface trough northwest of Puerto
Rico. GOES-16 PWAT imagery shows the trailing moisture of the
tropical wave still engulfing the forecast area with precipitable
water values above 2.0 inches. However, most of the area is fairly
tranquil at the moment with Doppler radar observing a band of
isolated to scattered showers over the Caribbean waters, south of
Puerto Rico, crossing into USVI, Vieques and Culebra. Rainfall
accumulations are minimal with this activity. Expect this pattern
to persist through early morning hours, with some showers also
affecting the eastern portions of Puerto Rico.

Today, a similar weather pattern can be expected with a southeast
wind flow and surface heating promoting deep convection over
northwestern and north central Puerto Rico. Streamers downwind of
the local islands and El Yunque will also produce moderate to heavy
showers over the San Juan Metropolitan area. Above seasonable normal
temperatures could help reach convective temperatures much earlier
than usual with the first round of convection starting by the late
morning hours and persisting through the afternoon. Light
steering winds will enhance rainfall accumulations with the
strongest thunderstorms and downpours. This activity will generate
ponding of water in roadways and in low-lying areas with the
possibility of minor urban and small stream flooding with the
heaviest showers.


As the broad tropical wave slowly moves away from the area, a drying
trend will take place with Saharan dust particulates filtering into
the region. Having said that, moisture erosion will be gradual with
precipitable water values remaining above normal to near normal
levels through the end of the short term period. Instability aloft
will remain marginal, enough to trigger deep convective activity
each afternoon with the seasonable morning showers out east. Winds
will shift east northeast on Wednesday and more east by Thursday,
focusing afternoon showers and thunderstorms over southwestern and
western Puerto Rico, respectively.

Heat index values above 100 degrees fahrenheit will be observed
every day over urban and coastal areas of the local islands.

&&

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

Despite migrating TUTT lows well outside of the forecast area to
the northwest through the northeast, the dominant pattern at
upper levels will be high pressure. This is only broken on Friday
when an inverted trough moving from east to west passes through
the area. After Thursday the precipitable water is generally less
than 2 inches with the exception of Friday and Monday where there
are brief excursions above 2 inches. At the surface high pressure
in the northeast Atlantic begins to migrate into the central
Atlantic ocean to maintain and strengthen the easterly trade wind
flow. A tropical wave moves through on Friday and Monday with
increased convective activity, but they are weak and have only
narrow bands of better moisture. Overall, however moisture is
somewhat above normal for the season, so showers will remain
active over Puerto Rico and to a lesser extent, the U.S. Virgin
Islands each day. Due to high relative humidities excessive heat
is expected in many lower elevation locations and heat advisories
may be needed for Wednesday and Friday through Monday.

&&

.AVIATION...
(06Z TAFS)

Mainly VFR conditions are expected to prevail across all
terminals through 16/16Z, with VCSH at times across the USVI
terminals and TJSJ. SHRA/TSRA is expected to develop across
northwestern and northern PR btwn 16/16-22, which may cause MVFR
conds at TJBQ and possibly at TJSJ as well. Winds will continue at
10-15 kt with sea breeze variations through 21z, bcmg light and
variable overnight.

&&

.MARINE...

Conditions remain generally tranquil for the next several days and
5 feet or less beyond that. Some isolated thunderstorms may be
encountered over the local waters each afternoon and evening--
mostly west of Puerto Rico.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
&&

$$

SHORT TERM...CVB
LONG TERM....WS
AVIATION...CVB

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
516 AM AST Thu Aug 18 2022


.SYNOPSIS...
Expect an active day of weather today with numerous showers and
isolated thunderstorms with the heaviest rainfall during the
afternoon hours. Flash flooding and mudslides are possible for
areas of steep terrain and the ponding of water on roadways is
also likely across urbanized areas. Typical weather of passing
showers and afternoon convection is forecast for the weekend as
drier air filters in. A tropical wave is expected to arrive on
Monday, starting off a wet pattern for next week.


&&

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

A surface trough just north of the area and trade wind convergence
across the northeastern Caribbean are producing scattered showers
and isolated thunderstorms across region. Most of the activity has
remained offshore, but showers are moving at times across portions
of northern and eastern PR, and across the USVI. The doppler radar
estimated around half an inch of rain with the heaviest showers
across northeastern and southeastern PR during the overnight hours.
Latest imagery from the Polar Blended-Percent of Normal Total
Precipitable Water(TPW) indicates between 110%-130% of above TPW
spread between PR and the northeastern Leeward Islands. Therefore,
higher moisture content will continue to stream across the area
today, and another active afternoon is expected with locally
numerous showers and isolated thunderstorms developing from central
to western PR. Flash flooding and mudslides in areas of steep
terrain are possible once again. Across the USVI and eastern PR, the
best window for periods of moderate to locally heavy rainfall are
through the morning hours, as a drier air slot is expected to move
from the east later in the day.

Through the rest of the short term forecast, areas of drier air and
patches of relative high moisture content will move from the east at
times. The next peak in precipitable water is forecast for late this
evening/overnight hours, favoring showers across the USVI and
eastern PR. A tropical wave currently near 52W is expected to stream
across the region on Friday during the day, therefore, showers and
thunderstorms are expected to develop once again across portions of
the Cordillera and western PR, and as well across San Juan &
vicinity. Moisture trailing the wave will favor passing showers
across the USVI and eastern PR on Friday night. A PWAT minima of
1.50 inches is forecast on Saturday morning, and mostly fair weather
conditions should prevail through the day, with the exception of
diurnally induced afternoon showers over west/northwest PR. In
summary, the threat for urban and small stream flooding with
localized flash flooding will remain elevated at least through
Friday.

&&

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

On Sunday, moisture values seem around climatological average and
a no upper level feature is notable, therefore a day of typical
passing showers and diurnal induced convection is expected.
A mainly easterly wind flow prevails until Monday when the
arrival of a tropical wave causes the winds to veer to the
southeast. Current GFS guidance shows Precipitable Water values
associated with this wave around 2 inches. In the upper levels, a
TUTT northeast of the region may enhance instability and the
proximity of this feature will determine how strong this rain
event will be. This SE wind flow on Monday and Tuesday is
expected to be generally lighter and because of this, a
significant amount of rainfall is possible along the Cordillera
Central.

Brief patches of dry air start to move in by Wednesday, however high
Precipitable Water values are present across the whole Caribbean due
to the passing of the aforementioned tropical wave. Expect
passing showers and afternoon development on Wednesday and
Thursday mostly driven by windward showers and local effects. By
Thursday at the surface, high pressure begins to strengthen across
the Central Atlantic, promoting the winds to back, becoming
mainly easterly with a bit more strength than previous days.
Friday was looking dry in previous model runs yet now another
tropical wave is expected to arrive during the afternoon hours,
bringing a wet pattern for the weekend. The upper levels also look
conducive for activity as low pressure aloft begins to prevail
around the islands. Overall, a wet pattern is forecast for the
long term period.


&&

.AVIATION...Mainly VFR conditions are expected to prevail across
all terminals through the forecast period. However, showers and
thunderstorms are expected to develop in and around TJBQ from
18/16z- 22z, which may cause tempo MVFR conds. Across the USVI and
TJSJ, passing SHRA & -TSRA across the coastal waters may cause
brief MVFR cigs through the morning hours. East winds expected at
10-15 kt with sea breeze variations.

&&



&&

.MARINE...
Seas remain calm with sea heights up no greater than 4 feet
today. Winds prevail from the east up to 15 knots. Passing
showers and isolated thunderstorms are likely over the local
waters as a surface trough north of the region is aiding activity.
Winds are expected to strengthen into the weekend, raising sea
heights slightly. There remains a moderate to low risk of rip
currents for the beaches of Puerto Rico and the US Virgin
Islands.



&&



&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
&&

$$

SHORT TERM...DS
LONG TERM....RC

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
455 AM AST Fri Aug 19 2022


.SYNOPSIS...
Due to a broad tropical wave, expect trade wind passing showers
and an increase of storm activity during the afternoon hours for
the interior/western and eastern mountainous sections of Puerto
Rico. There is a slight to elevated flooding threat with this
activity. These conditions will prevail through the weekend and
heat indices should range between 102-108 degrees along coastal
areas of northern, western and southern PR. The combination of a
tropical wave and a Tropical Upper Tropospheric Trough (TUTT) may
bring unsettled weather conditions on Monday, lasting into next
week.


&&

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

Passing trade wind showers ahead of a broad tropical wave will
continue to move across the regional waters and portions of the USVI
and eastern PR through the morning hours. Precipitable water (PWAT)
content is expected to peak just above 2.10 inches by this afternoon
as the tropical wave moves across the eastern Caribbean. Therefore,
showers and thunderstorms are expected to develop today along
portions of the interior and western PR, and over the eastern
mountains into portions of San Juan and vicinity. There is a slight
to elevated flooding threat with this activity. Latest Total
Precipitable Water imagery suggest that there is a drier air mass
trailing the wave, which could limit shower development tonight
across the forecast area. However, this is expected to be short-
lived as moderate to locally fresh trades will continue to carry the
occasional passing showers across the islands and PWAT will
remain between 1.80-1.90 inches through the weekend. Therefore,
early morning convection will favor showers between the USVI and
eastern PR, followed by diurnally induced afternoon showers with
thunderstorms across portions of the interior and western PR each
day. This higher moisture content will keep dewpoints in the upper
70s to low 80s along coastal areas of northern, western and
southern PR, and heat indices should range between 102-108 degrees
across these areas between the late morning and early afternoon
hours.


&&

.LONG TERM...Monday through Saturday...
The axis of a tropical wave will cross through the region on
Monday, providing sufficient moisture for enhanced rainfall across
the islands. Atmospheric dynamics looks favorable with high
surface Omega values Monday afternoon as a Tropical Upper
Tropospheric Trough (TUTT) retrogrades north of the region. As the
wave passes, winds will veer and prevail from the southeast, with
variable speeds between 10 and 15 knots. This will favor
afternoon development in the interior/northwest quadrant of
Puerto Rico and also streamer formation may occur, affecting the
San Juan Metro area. As winds will continue to prevail from the
southeast for most of the week, warmer temperatures are expected
for the northern coastline of Puerto Rico. Heat indices will rise
in the 100s especially across urban coastal areas.

The influence of this TUTT will be weaker on Tuesday, however a
short wave trough reflected down to the surface from this dying
TUTT will pass by on Wednesday. The region`s Precipitable Water
values will remain elevated until about Thursday. Plus, during
these days, diurnal heating and local effects should cause enough
instability that should enhance rainfall. Activity by the end of
the week should become more isolated due to this patchy moisture,
however moisture convergence in the afternoon may provide some
decent rainfall in select areas of Interior/Western Puerto Rico.
Current model guidance for weekend shows that Friday onward will
consist of a drier trend as the bulk of moisture from passing
tropical waves remain south of the region. Winds will assume more
of an easterly direction and a typical passing shower and
afternoon convection regime will prevail.



.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals early in the forecast period. Passing showers may cause
brief MVFR cigs through the morning hours across the USVI terminals
and TJSJ. Then, in the afternoon hours a tropical wave is expected
to bring periods of showers and thunderstorms across the islands and
tempo MVFR conds are likely across most of the area terminals. East
winds expected to continue btw 9-18 kt with sea breeze variations.



&&

.MARINE...Seas remain around 4 feet, as wind wave energy and
moderate easterly wind flow will prevail today into the weekend.
Unstable weather conditions continue to allow scattered showers
and isolated thunderstorms to affect the local waters from time to
time. Wave heights are expected to get up to around 5 feet as the
winds will hold strength throughout the weekend, with the
dominant period rising to around 7 seconds. A very small 10
second swell will be present by Saturday morning, without causing
noticeable increases in wave heights. Weather over the local
waters will deteriorate on Monday as a tropical wave passes
through.

A moderate to low risk of rip currents exist for the beaches of
Puerto Rico and the USVI.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
&&

$$

SHORT TERM...DS
LONG TERM....RC

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
442 AM AST Sun Aug 21 2022


.SYNOPSIS...
A tropical wave passing south of the islands and trade wind
convergence is resulting in numerous showers and scattered
thunderstorms across region. Another active day of weather is
expected today with an elevated threat for urban and small stream
flooding, with localized flash flooding and mudslides in areas of
steep terrain. Tomorrow more unstable weather is forecast as an
upper level low moves close to the region and then a seasonal wet
weather pattern of passing showers and afternoon storms is
expected for the majority of the week. A strong tropical wave may
pass over the islands at the end of the long term period.

&&

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

A tropical wave moving across the central Caribbean and trade wind
convergence across the eastern Caribbean are producing numerous
showers and scattered thunderstorms across region. The heaviest
activity has remained across the Caribbean waters, but showers with
periods of moderate to locally heavy rainfall moved at times across
portions of southeastern PR, and across the USVI. Since midnight,
the doppler radar estimated near an inch of rain across portions of
eastern PR. Latest Blended-Percent of Normal Total Precipitable
Water (TPW) indicated a broad area of 110%-130% of above TPW between
the local area and just east of the Leeward Islands. Therefore,
higher moisture content will continue to advect across the islands
today, and another active weather day is expected with scattered to
locally numerous showers and isolated thunderstorms affecting
portions of the islands at times. There is an elevated threat for
urban and small stream flooding, with localized flash flooding and
mudslides in areas of steep terrain.

Unstable conditions will continue through early in the week, as an
upper-level low moves close to the region from the central Atlantic.
An induced surface trough will move across the northeastern
Caribbean by Monday, and weakening of the surface high across the
western Atlantic will promote a light to moderate and moist
southeasterly wind flow across local area. Therefore, an overall wet
pattern will continue across the islands through at least Tuesday.

&&

.LONG TERM...Wednesday to Monday...
The ridge phase of the African Easterly Jet arrives on Wednesday and
it brings patchy moisture over region. No prominent feature is
present in the mid to upper levels besides a TUTT-low to the north
that may excite more showers over the Atlantic Waters but nothing
significant. Wind flow will prevail from the East-southeast
around 10-15 knots with seabreeze variation as a high pressure
system dominates the Northern Atlantic Basin. The typical weather
pattern of passing showers and afternoon convection over
interior/western Puerto Rico is expected through Friday. Local
effects and diurnal heating may amplify the available moisture so
there could be some standout periods of rainfall during this
time.

Saturday afternoon a snap of moisture is expected to reach the
islands and provide a wetter evening compared to the days before.
Winds continue from the east at moderate speeds and atmospheric
stability seems normal so an increase of passing showers and
stronger afternoon thunderstorms will be the result of this
increase in moisture. Currently the NHC is monitoring an area of
development that GFS model guidance is suggesting will begin
affecting the region by Sunday afternoon. It appears as a robust
tropical wave that has the potential to bring heavy rainfall and
strong winds for the beginning of next week. GFS model guidance
has the axis passing by Monday night into Tuesday morning, a day
later in timing than yesterday. This forecast will change due to
the fickle nature of weather forecasting models this far out, yet
a strong tropical wave is expected sometime during the end of the
long term period. The results of this is a veering of the winds
and a very saturated, unstable atmosphere up to the tropopause.

&&

.AVIATION...VFR conds expected but SCT SHRA and iso TSRA may
continue to affect the USVI and TJSJ/TJNR terminals during the
morning hours. Mtn top obscd over eastern PR and SCT-BKN lyrs nr
FL025...FL050 ovr regional waters and enroute btw islands are
expected. Brief periods of MVFR are possible due to low CIGS and
reduced VIS. Winds expected to increase btw 12-16 kt from the east
with higher gusts and sea breeze variations aft 14Z.



&&

.MARINE... A high pressure system stretched across the Central
Atlantic continues to promote moderate to locally fresh easterly
winds across the region. These winds are producing a local wind
swell that is resulting in choppy seas up to around 5 feet. Winds
are expected to decrease in strength and become more
southeasterly tomorrow. Passing showers and isolated
thunderstorms continue to effect the local waters with most of the
concentration in the Caribbean waters today. A very small
northerly swell is expected to arrive overnight on Monday. Across
Puerto Rico and the US Virgin Islands, a moderate risk of rip
currents exist along most northern and eastern facing coastlines
and the risk is low elsewhere.



&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
&&

$$

SHORT TERM...DS
LONG TERM....RC

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
507 AM AST Mon Aug 22 2022


.SYNOPSIS...
An active weather day with a high risk of urban and small stream
flooding is expected today with instability aloft supporting deep
convection over the region. Expect showers in eastern sections of
Puerto Rico and the USVI followed by deep afternoon convection
along and north of the Cordillera Central. With saturated soils,
flash flooding and mudslides cannot be rulled out in areas with
continuous showers. Increased moisture is also expected during the
weekend and a tropical wave may affect the region to start after
next weekend.

&&

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

GOES-East Total Precipitable Water still estimates plenty of
tropical moisture over the region, with values ranging between 1.5
and 1.85 inches, which are between the percentile 25th and 75th for
August. A retrograding TUTT-low will provide good instability
supporting deep convection over the region. Under this weather
pattern, you can expect the advection of showers across the eastern
sections of Puerto Rico and the U.S. Virgin Islands, followed by
deep afternoon convection along and north of the Cordillera Central,
including the metropolitan area of San Juan. A similar pattern
should persist on Tuesday. The risk of urban and small stream
flooding is high, and because soils are saturated, flash flooding
and even mudslides may not be ruled out if downpours affect the same
area, especially during the afternoon.

In addition, heat index values will reach and surpass the 100s
degrees Fahrenheits each afternoon, especially along coastal and
urban areas.

The TUTT-low should move farther away from the islands by Wednesday,
and the tropical moisture should somewhat diminish. Therefore,
Wednesday should be the driest day in the short-term forecast.
However, pockets of moisture embedded in the trades will promote the
typical overnight and early morning passing showers across the
windward sections. Under the influence of the sea breeze
fluctuations and the diurnal heating, afternoon convection will
develop across western Puerto Rico and downwind from the Virgin
Islands.

&&

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

A relatively wet long term forecast period is expected, especially
from the weekend onwards. As patches of moisture reach the forecast
area on Thursday and Friday expect a generally typical weather
pattern of passing showers mainly over the eastern forecast area and
shower activity during the afternoon hours mainly over the interior
and western municipalities of Puerto Rico due to diurnal heating and
local effects. Models currently show that most of the moisture
patches that will enter the area through the end of the workweek
will arrive on Thursday. Several of those areas of moisture will
have Precipitable Water values above 2 inches, which is above
normal values for this time of the year. Winds will be generally
from the east-southeast at around 10-15 knots with seabreeze
variations.

A wind surge along with a band of increased moisture is forecast to
reach the region during the late afternoon hours on Saturday. This
band should also have Precipitable Water values above 2 inches. With
easterly winds, this area of increased moisture can bring increased
shower activity as it passes through the forecast area from the late
afternoon hours on Saturday through the morning hours on Sunday.
Lingering moisture could also increase the typical shower activity
on Sunday.

GFS model guidance continues to start the workweek with a tropical
wave affecting our region. This tropical wave is currently being
monitored by the NHC as it is currently producing showers and
thunderstorms over the eastern tropical Atlantic. The NHC has given
this tropical wave a low formation chance of 20 percent through the
next five days. Nevertheless, model guidance currently has the axis
of this tropical wave passing through our area from Monday night
through the end of the forecast period. Current model guidance has
backed off on previous Precipitable Water values over our region.
This tropical wave still has the potential to bring heavy rainfall
to our region but given how far out in time the models are and how
they have been behaving with regard to this wave, the forecast and
direct impacts to our region can vary.


&&

.AVIATION...SHRA will move across the local flying area today,
some of them will affect JSJ/IST/ISX at times. Afternoon SHRA/TSRA
are expected across the Cordillera Central and the SJ-Metro Area,
as well as downwind from the USVI. This activity could impact
JSJ/JBQ between 22/16-22z, and may result in MVFR or even IFR
conditions. Expect calm to light and VRB winds thru 22/13z, when
will return from the E-ESE at 10-15kt with sea breeze variations
and gusty near TSRA/+SHRA.

&&

.MARINE...Moderate easterly winds will prevail as a surface high
pressure continues to build over the Central Atlantic. Quick
passing showers and isolated thunderstorms and brief wind gusts
will continue to affect the coastal waters and local passages from
time to time. There is currently a low risk of rip currents for
all local beaches in the forecast area.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
&&

$$

SHORT TERM...CAM
LONG TERM....MRR

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Tue Aug 23 2022

.SYNOPSIS...
Another active weather day is expected today due to available
tropical moisture, the proximity of a TUTT-low and an induced
surface perturbation. Once again, expect showers in eastern
sections of Puerto Rico and the USVI followed by deep afternoon
convection along and north of the Cordillera Central, including
the San Juan metro area. The risk of urban and small stream
flooding continues and saturated soils can increase the risk of
flash flooding and mudslides in areas with continuous showers.
Tropical waves may lead to an active weekend and start of the
workweek. Heat index values in/over the 100s degrees are expected,
especially along coastal and urban areas. There is currently a
low risk of rip currents for all local beaches.

&&

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

We are still expecting active weather today due to the proximity of
a TUTT-low and an induced surface perturbation combined with plenty
of tropical moisture. Once again, GOES-East Total Precipitable Water
estimated values between 1.7 and 1.90 inches, which are between the
25th and 75th percentile for August. Therefore, expect the advection
of showers across the eastern sections of Puerto Rico and the U.S.
Virgin Islands, followed by deep afternoon convection along and
north of the Cordillera Central, including the San Juan metropolitan
area. Once again, the risk of urban and small stream flooding is
high, and because soils are saturated, flash flooding and even
mudslides may not be ruled out if downpours affect the same area,
especially during the afternoon.

In addition, the available moisture combined with maximum
temperatures in the 90s will result in heat index values in/over the
100s degrees Fahrenheits, especially along coastal and urban areas.
These heat indices may extend each day.

The TUTT-low will move farther away, and a drier air mass should
replace the current moist air mass by Wednesday. Therefore,
Wednesday should be the driest day in the short-term forecast.
Nevertheless, the trade winds will advect pockets of moisture,
promoting a seasonal weather pattern. A trade wind perturbation will
increase the frequency and intensity of showers on Thursday. Sea
breeze, low-level convergence, and diurnal heating could enhance the
development of afternoon convection across western Puerto Rico and
downwind from the Virgin Islands.

&&

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

A relatively wet long term forecast period continues to be expected,
especially from the weekend onwards. Friday currently appears to be
the driest day of the period in terms of precipitable water, with
patches of moisture reaching the islands staying at normal values
for this time of the year. The end of this workweek should be
characterized by a generally typical weather pattern of passing
showers mainly over the eastern forecast area and shower activity
during the afternoon hours mainly over the interior and western
municipalities of Puerto Rico due to diurnal heating and local
effects. According to model guidance, Friday also currently shows
the driest mid- and upper- levels when compared to the rest of the
long term period. Winds will be generally be from the east at around
10-15 knots with seabreeze variations.

Current model guidance shows humidity related to a tropical wave
reaching our off-shore Caribbean waters by Saturday morning, this
humid airmass includes precipitable water values of above 2 inches.
Meanwhile, a wind surge along with a band of moist air is also
forecast to reach the region during the late afternoon hours on
Saturday. This band should also have precipitable water values above
2 inches. Both of these areas of increased moisture can bring
increased shower activity as they affect the forecast area from the
late afternoon hours on Saturday.

GFS model guidance shows humidity from the tropical wave being
monitored by the NHC also affecting our region from Sunday and into
the first half of the workweek. This tropical wave is currently
producing showers over the eastern tropical Atlantic and the NHC has
given it a low formation chance of 10 percent through the next 48
hours and 20 percent through the next five days. Current model
guidance has once again added higher precipitable water values over
the region. Late Sunday through early Wednesday currently show a
deep moist layer reaching the upper levels. This tropical wave still
has the potential to bring heavy rainfall to our region but given
how far out in time the models are and how they have been behaving
with regard to this wave, the forecast and direct impacts to our
region can vary. Weather conditions in the forecast region will be
tied to the development of these systems, we will continue to
monitor the future development of theses system throughout the
coming days.

&&

.AVIATION...Calm weather conditions will prevail early in the
morning (thru 23/15z). SHRA/TSRA will develop across the local
islands between 23/15z-24/04z. This activity will develop mainly
downwind from the USVI and over the Cordillera Central, but may
impact JSJ/JPS/JBQ/IST/ISX at times. MVFR or even IFR conditions
are possible btwn 23/17-22z. Expect calm to light and VRB winds
thru 23/13z, when will return from the ESE at 10-15kt with sea
breeze variations and gusty near TSRA/+SHRA.

&&

.MARINE...Moderate easterly to southeasterly winds will prevail
as a surface ridge builds over the central Atlantic and drifts
eastward. Quick passing showers and isolated thunderstorms and
brief wind gusts will continue to affect the coastal waters and
local passages from time to time. There is currently a low risk
of rip currents for all local beaches in the forecast area.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
&&

$$

SHORT TERM...CAM
LONG TERM....MRR

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
510 AM AST Wed Aug 24 2022

.SYPNOSIS...
Improving weather conditions are expected today with only a few
passing showers in the morning and afternoon showers with one or
two thunderstorms across the interior and western sections of
Puerto Rico. Heat index values will reach the 100 degrees
especially along coastal and urban areas. There is a moderate
risk of rip currents for the northcentral and northwest beaches of
Puerto Rico, there is a low risk of rip currents elsewhere.

A broad trough of low pressure is forecast to cross the Lesser
Antilles around late Thursday night or early Friday morning. The
National Hurricane Center is actively monitoring this disturbance;
additional information is available in the Tropical Weather
Outlook (TWOAT) or www.nhc.noaa.gov.

&&

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

Weather conditions should improve today compared with the previous
days. Therefore, expect a few passing showers early in the morning
(but mainly across the local waters), with a mixture of clouds and
sunshine through the morning. The available moisture combined with
maximum temperatures in the upper-80s and low-90s will result in
heat index values in/over the 100s degrees Fahrenheits, especially
along coastal and urban areas. These heat indices may occur the rest
of the days of the workweek. During the afternoon, local effects,
sea breeze, and diurnal heating will promote showers with one or two
thunderstorms across the interior and western PR.

A trade wind perturbation will increase the frequency and intensity
of showers on Thursday, and sea breeze, low-level convergence, and
diurnal heating could enhance the development of afternoon
convection across the interior and western Puerto Rico and downwind
from the Virgin Islands.

A broad trough of low pressure is forecast to cross the Lesser
Antilles around late Thursday night or early Friday morning, with
its bulk of moisture remaining well south over the Caribbean Sea.
However, the typical weather pattern is anticipated for the Virgin
Islands and Puerto Rico. The National Hurricane Center actively
monitors that system; additional information is available in the
Tropical Weather Outlook (TWOAT) or www.nhc.noaa.gov.

&&

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

The weekend will start off with humidity related to a low pressure
system reaching our offshore Caribbean waters on Saturday morning
according to model guidance. This humid airmass includes
precipitable water values of above 2 inches, which is above normal
values for this time of the year. This disturbance is currently
being monitored by the NHC, who gave it a low formation chance of
near 0 percent through the next 48 hours and 20 percent through
the next five days. This low formation chance of 20 percent
through the next five days could occur in the Caribbean Sea.
Nevertheless, the humid air related to this disturbance will
increase rain chances, especially in the Caribbean Sea. Meanwhile,
a wind surge along with a band of moist air is also forecast to
reach the region during the late afternoon hours on Saturday. This
band should also have precipitable water values just below 2
inches. Both of these areas of increased moisture can bring
increased shower activity as they affect the forecast area on
Saturday.

GFS model guidance shows humidity related to a tropical wave
affecting our region from Sunday and into the first half of the
workweek. This wave no longer has any cyclonic formation chance,
but current model guidance shows high precipitable water values
over the region. Late Sunday through early Wednesday still show a
deep moist layer reaching the upper levels. These disturbances
promote an increased potential for heavy rainfall, especially to
start the workweek. Weather conditions in the forecast region will
be tied to the development of these systems, we will continue to
monitor the future development of theses system throughout the
coming days and given how the models have been behaving,
especially for the start of the workweek, direct impacts to our
region can vary. A drying trend will be observed from late
Wednesday through the end of the long term forecast period, with
precipitable water values reaching normal values. For this time
expect a generally typical weather pattern of passing showers
mainly over the east and shower activity during the afternoon
hours mainly over the interior and western Puerto Rico due to
diurnal heating and local effects.

&&

.AVIATION...VFR conditions will prevail today. SHRA/TSRA will
form across the Cordillera Central and downwind from the USVI
during the afternoon, btwn 24/17-22z. This activity could impact
local terminals, but most of the activity is expected in the VCTY.
Expect calm to light and VRB winds through 24/13z, returning from
the E at 15-20kt with sea breeze variations and gusty near
TSRA/+SHRA.

&&

.MARINE...Generally moderate easterly winds are expected to
prevail due to a surface high pressure system over the Atlantic.
Quick passing showers and isolated thunderstorms producing brief
wind gusts will continue to affect the coastal waters and local
passages from time to time. Small craft should exercise caution in
the local Atlantic waters due to locally fresh winds. There is
also a moderate risk of rip currents for the northcentral and
northwest beaches of Puerto Rico, there is a low risk of rip
currents elsewhere.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
&&

$$

SHORT TERM...CAM
LONG TERM....MRR