Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
523 AM AST Sat Oct 28 2023

.SYNOPSIS...A Flash Flood Watch is in effect for Puerto Rico and
the U.S. Virgin Islands through Monday morning. Unsettled
conditions are expected to persist due to the interaction of the
mid to upper trough and the broad surface trough with axis now
crossing the region, with showers and scattered thunderstorms
affecting the islands. The risk of urban, river, and flash
flooding, as well as mudslides will be elevated through at least
early next week. Hazardous marine and coastal conditions will
persist across the Atlantic waters and coastlines, as well as
across the Caribbean Passages through early next week due to
northerly swells.

&&

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

Abundant pooling of moisture and good low level convergence across
the region will persist due to the interaction of the mid to upper
trough and the broad surface trough with axis now crossing the
region. This weather scenario will maintain a moist light to
moderate east southeast to south southeast low level wind flow
through the short term forecast period. However, recent model
guidance and the present synoptic pattern and satellite imagery, all
suggest that the upper trough will gradually shift farther west and
will be replaced by an upper level ridge. In the meantime the local
area will be under a south to southwesterly wind flow aloft which
will provide good ventilation for convective activity through the
weekend. Favorable conditions for convective development across the
region is therefore expected to persist. Consequently there remains
an elevated to significant risk of urban and small stream flooding
and flash flooding across much of Puerto Rico and portions of the
U.S. Virgin Islands. In addition the strong northerly swells
generated by Tropical Storm Tammy will continue to invade the
regional waters and passages resulting in hazardous seas and
dangerous surf-zone conditions at least until Monday.

For the rest of the morning hours,passing showers and isolated
thunderstorms will bring periods of moderate to locally heavy rains
across regional waters mainly between eastern Puerto Rico and the
U.S. Virgin islands. Some of this activity may reach portions of
south and east sections of PR and the USVI. This may lead to ponding
of water on roads and in poor drainage areas due to moderate to
locally heavy rains. Later in the day afternoon convection is again
expected and urban and small stream and river flooding will be
likely in many areas across Puerto Rico, and isolated spots in the
USVI. Based on the present wind flow, the afternoon activity should
be focused over the interior, east-southeast and north sections of
sections of Puerto Rico,to include the San Juan metro and northwest
PR. The U.S. Virgin Islands will also continue to receive periods of
showers and isolated thunderstorms throughout rest of the day.

On Sunday and through Monday, as mentioned the upper trough will be
replaced by a ridge which build and linger across the region the
rest of the period. However model guidance suggests continued
moisture convergence with a winds surge and easterly perturbation
crossing the area. This will be sufficient to support the
development of early morning and afternoon showers and
thunderstorms, some of which will be enhanced and will result in
periods of locally heavy rains each day.

The heavy rains accompanying the early morning and afternoon showers
and thunderstorms across the islands will cause ponding of water on
roads and poor drainage areas and will continue to cause urban,
small stream and flash flooding. Therefore a Flash Flood Watch will
remain in effect for Puerto Rico and the U.S. Virgin Islands due to
the elevated risk of widespread flooding. Please refer to the latest
Flash Flood advisory (FFASJU) issued by WFO San Juan PR.

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

The period will start with a mid- to upper- level ridge overhead of
the islands. Model guidance suggests a mid- to upper- level trough
building to our east slowly eroding the ridge throughout the long
term period and gradually increasing instability aloft. GFS model
suggests precipitable water (PWAT) values up to around 2.4 inches
across the region Tuesday, decreasing to around 2.0 inches on
Wednesday with drier air filtering in on late Thursday and Friday,
and finally more moist air filtering in again and increasing PWAT to
around 2.0 inches on Saturday. Southerly windflow will persist over
the area through Thursday, helping lift tropical moisture into the
area from the ITCZ. Winds are forecast to become more easterly and
increase late Thursday and into Friday. Although the environment
will remain moist, the driving force for the afternoon convection
will be diurnally induced to start the period, as conditions will be
more stable aloft during that time, with additional instability from
perturbations reaching the region and a lingering surface trough.
Instability aloft due to the mid- to upper- trough and and increase
in moisture will in turn increase rain chances during to end the
period. Discrepancies continue between the GFS and the ECMWF model
but already saturated soils from events in the short term period
increase the potential for urban, small stream and flash flooding,
along with mudslides in areas of steep terrain. Please continue to
monitor future updates.

&&

.AVIATION...Variably cloudy skies and unsettled weather conds
will persist across the flying area due to the interaction of a mid-
upper-level trough and broad surface trough spread across the
region. SCT-BKN cld lyrs nr FL025...FL040...FL090 and BKN-OVC nr
FL250. SHRA/Isold TSRA ovr lcl waters and en route between the local
terminals. TIST/TISX can expect prds of MVRF/IFR conds due to
SHRA/Isold TSRA, and VCSH at TJSJ til 28/12Z. Late morning and aftn
SHRA/Isold TSRA dvlpmnt fcst btw 28/16-22z around the islands with
MTN top obscr ovr PR due to low cig w/SHRA/ Isold TSRA. SFC wnd calm
to LGT/VRB, BCMG fm ESE/SSE around 10 kt aft 28/14z. Hir gusts with
aftn convection.

&&

.MARINE...Hazardous marine and coastal conditions will persist
through early next week due to northerly swells. Small Craft
Advisories are in effect for the Atlantic Offshore Waters and
Caribbean Passages until at least late Sunday night due to seas
between 8 and 12 feet. At 5 AM AST the San Juan, Arecibo and
Rincon CariCOOS buoys reported 7-10 foot wave heights with
periods of 13-14s. Beachgoers, avoid the Atlantic Coastline in
Puerto Rico and the U.S. Virgin Islands due to hazardous coastal
conditions. Please see the CFWSJU and MWWSJU products for more
information.

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
605 AM AST Sun Oct 29 2023

.SYNOPSIS...
A broad and elongated trough of low pressure extending northwards across
the region into the southwest Atlantic, and a mid to upper level trough
now just west of the region, will maintain moist and very unstable weather
conditions today through Monday. North northeasterly swells generated
from distant Tropical Storm Tammy will continue to affect the regional
waters and passages, creating hazardous marine and dangerous surf zone
conditions. A Flash flood watch will remain in effect for Puerto Rico
and the U.S. Virgin Islands at least until Monday due to the unsettled
weather and saturated soil conditions.

&&

.SHORT TERM...Today into Tuesday...

A building mid- to- upper level ridge continues to establish itself
over the area with the mid- to upper- level trough and surface trough
that have affected the region continue moving away from the islands.
The ridge will linger over the area through most of the period. However,
moisture convergence, diurnal effects, and arriving wind surges and
easterly perturbations will continue to promote active weather
throughout the period. This will promote early morning and afternoon
showers and thunderstorms. With east- to- southeast surface winds,
this activity should be focused this afternoon over north, east/
southeast and interior sectors of Puerto Rico, including Vieques
and Culebra.

Heavy rains from these showers can cause ponding of water over
roadways and poorly drained areas, urban, small stream, and flash
flooding across the islands. Shower and thunderstorm activity can
also cause locally gusty winds and frequent cloud-to-ground
lightning, and elevated streamflows and quick river rises. With
already saturated terrain across various areas, landslides in areas
of steep terrain is also likely. The Flash Flood Watch will continue
to be in effect for Puerto Rico and the U.S. Virgin islands through
tomorrow morning as the risk for widespread flooding continues.
However, a wet pattern will continue for the rest of the period.
Model guidance indicates precipitable water (PWAT) values around 2.5
inches persisting during the period. Please continue to monitor the
latest products and updates by WFO San Juan.

&&

.LONG TERM...Wednesday through Sunday...
A mid- to upper level ridge will linger across the region through
much of the workweek but is to slowly erode by Friday and into the
weekend as an upper trough will become amplified and sink southwest
across the northeast Caribbean into the southeast Caribbean. Recent
model guidance suggest still a fairly moist environment through at
least Thursday with PWAT values to remain between 1.80 to 2.35 inches
as an easterly perturbation is to cross the eastern Caribbean. A drier
airmass is then expected to filter in by Friday and into the weekend
with the south southeast winds forecast to become more ease southeast
by then. This in turn will erode the low level moisture convergence
and therefore favor less chance for widespread showers and thunderstorm
development across the region. The prevailing southerly windflow will
persist through Thursday, and will aid in lifting tropical moisture
into the area. However as mentioned, by Friday onwards winds are to
become more easterly and increase through Sunday resulting in erosion
of tropical moisture transport.

Although the environment will remain moist, afternoon convection will
be more locally and diurnally induced, as conditions will be more stable
aloft. However additional instability caused from the easterly perturbations
crossing the region and a lingering surface trough will be sufficient
for early morning and afternoon convection each day. However by Friday
and into the weekend, both model guidance suggest a somewhat drier
weather pattern with more seasonal conditions. Regardless, saturated
soils from previous rainfall and daytime heating will still maintain
the potential for urban, small stream and flash flooding in isolated
areas, along with mudslides in areas of steep terrain. Please continue
to monitor future updates.

&&

.AVIATION...
Periods of MVFR conditions, and occasional IFR conditions remain possible
across the terminals due to SHRA/TSRA through the forecast cycle. Particularly
for the TJSJ, TJBQ and USVI (due to SHRA/Isold TSRA moving in from the
local waters) terminals. ESE winds between 10 to 15 knots with higher
gusts in showers and thunderstorms.

&&

.MARINE...
Recent data from surrounding buoys including the CariCOOS buoy
network around Puerto Rico and the U.S. Virgin Islands indicated
persistent wave heights between 4-7 feet for buoys with north
exposure (San Juan, Arecibo, and Rincon) and 3-5 feet for more
protected buoys (Ponce, Vieques, and Saint John). Swell periods
continued between 10-13 secs across the Atlantic waters and
passages. North northeasterly swells generated by Tropical Storm
Tammy will maintain hazardous seas and life- threatening surf zone
conditions into early next week. As a result, Small Craft Advisories
and a High surf advisory and Rip Current Statement remain in
effect. For details, refer to the Marine Weather Message (MWWSJU)
and Coastal Hazard Message (CFWSJU) issued by the National Weather
Service, San Juan office.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
519 AM AST Tue Oct 31 2023

.SYNOPSIS...
Issued at 455 AM AST Tue Oct 31 2023

A variable weather pattern will persist at least until today
across the region due to the presence of an trough over the region
and plenty of tropical moisture. Therefore, the islands can
expect period of showers across the local areas and in the
afternoon hours. A more seasonal weather pattern is forecast for
midweek, as a more drier filters into the region and the influence
of the trough moves out of the region. Tranquil marine conditions
will persist for most of the period.

&&

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

Minimum temperatures were between the mid 70s to low 80s across the
lower elevations, and from the upper 60s to low 70s across the
higher elevations. Scattered showers and isolated thunderstorms were
noted across the Caribbean waters and under southeasterly winds they
moved along portions of southern and eastern PR through the night.
The Doppler radar estimated between half to an inch of rain with
this activity.

Additional showers and thunderstorms are expected to redevelop
across the same areas through the rest of the day, as a surface
trough to our south continues to develop into an area of low
pressure while moving slowly westward. This may cause a training
effect over the south/southeastern sections of PR through at least
tonight, producing urban and small stream flooding. Localized flash
flooding is also possible as soils are saturated from previous days
rainfall. Due to a break in clouds today, daytime heating in
combination with the available moisture and the sea breeze
convergence should lead to thunderstorm development over portions of
the Cordillera and west/northwest PR, including from El Yunque area
into the San Juan metro area due to the southeasterly steering winds.

A building mid-level ridge and a developing TUTT-low to our east are
expected to promote more stable conditions and drier air intrusion
over the northeastern Caribbean from Wednesday to Thursday. In
addition, a weak Saharan Air Layer will bring minor dust
concentrations during this period. Therefore, a more typical weather
pattern is expected across the islands during these two days, with
locally induced afternoon convection developing mainly over the
interior and northwestern PR. Across the USVI, Vieques, and Culebra,
streamers are expected to develop downwind of the islands. But,
overall fair weather conditions are expected.

&&

.LONG TERM...Friday trough Tuesday...

Global model guidance continues to show the development of a low-
pressure system just southwest of the local islands by midweek.
This area, now being monitored by the NAtional Hurricane Center
has a high chance of formation in the next seven days. Given the
proximity of the system, as a tropical cyclone develops, the
islands can be influenced by the system with changes in the wind
pattern and the presence of the abundant moisture filed over the
Caribbean. According to the GFS, PAT values would range from 1.5
to 2.1 inches. Additionally to the moisture, the islands will be
under the influence of a easterly winds, favoring a seasonal
pattern with advective showers across the windward sections of
Puerto Rico and the U.S. Virgin Islands.

For the upcoming weekend, as the tropical cyclone or low pressure
moves westward, more into the southwestern Caribbean, a more
direr air mass will filter into the region. That drier air, in
combinations with the convergence side of a mid to upper level
ridge and a upper level trough will inhibit the vertical
development of showers. Having said that,. the lack of instability
and the presence of humidity in the climatological normals, will
only drive a very seasonal pattern. Therefore, residents can
expect, morning showers over the windward section and afternoon
convection in the interior and west side in the afternoons.

By Sunday into Tuesday, a broad building surface high pressure
will spread across the central Atlantic into the Western Atlantic,
resulting in a more east-southeasterly winds. This wind pattern
influx will allow, pockets of tropical moisture moving into the
area. As a result, the potencial for shower increase in somewhat
by this last part of the forecast.

In general, the forecast expect pop of 20 to 40 from Friday to
Sunday, increasing up to 50 for the upcoming Sunday into Tuesday.


&&

.AVIATION...
Mainly VFR conditions expected across all terminals through the
forecast period. However, SHRA/TSRA may cause tempo MVFR conds at
TJSJ/TJPS throughout the day, and at TJBQ this afternoon. Low
level winds will continue S-SE at 10-15 kt with sea breeze
variations and higher gusts after 31/14z.

&&

.MARINE...
Marine conditions will remain generally benign today, with a
moderate southeasterly wind flow and seas up to 5 feet across most
of the local waters. Shower and thunderstorms activity will
persist for the rest of the day, resulting in localized hazardous
marine conditions. A broad surface high pressure will likely
build over the central Atlantic by midweek, bringing moderate to
locally fresh easterly trade winds. A northerly swell is forecast
to spread across the local Atlantic waters by Friday. In the
meantime, shower and thunderstorm activity will continue to affect
the local waters.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
445 AM AST Wed Nov 1 2023


.SYNOPSIS...
The mid to upper-level high pressure ridge making its way across
the local area will create a more stable and drier weather
pattern in the local forecast area until at least late Thursday.
This weather feature will keep an east-southeast flow in place
today, transitioning to an eastward flow on Thursday. Any limited
shower and thunderstorm activity is expected to focus on the
northwest portions of Puerto Rico this afternoon.

&&

.SHORT TERM...Today through Friday...
Today's main hazards revolve around the risk of excessive rainfall
and lightning at limited threat levels and excessive heat risks at
limited to elevated threat levels.

An analysis of overnight radar and satellite imagery indicated that
portions of Puerto Rico's eastern half, Vieques, Culebra, and the
U.S. Virgin Islands experienced isolated to scattered showers,
resulting in radar- estimated rainfall accumulations of up to
quarter of an inch over southeastern Puerto Rico. Overnight
temperatures varied across the region, ranging from around 68
degrees across higher elevations to about 80 degrees across
windward areas and the local islands. Winds were generally light
and variable.

A transition between dominant synoptic features will continue today,
transitioning from an upper-level ridge, now centered between
Hispaniola and Cuba, to a retrogressive TUTT-low, expanding over the
eastern Caribbean from the east. While ventilation from the ridge
will continue to enhance convective development, the TUTT-low and
the associated surface-induced trough will likely create conditions
marginally conducive to deep convective development later in the
week. The extent to which the TUTT-low will propagate westward
before the ridge remains uncertain, with the scope of the activity
depending on the influx of tropical moisture and the strength of the
trade wind cap. At the surface, expect a drier airmass along with a
light concentrations of Saharan dust to extend across the region
from the east today, while a moist plume will persist from the
southeast, creating a pronounced moisture contrast from below-normal
PWAT values of 1.2-1.4 inches to the north and more typical PWAT
values of 1.7-1.9 inches to the south through Thursday morning. By
Thursday, the plume of moisture will likely envelop most of the
region, followed by intermitent patches of drier with Saharan
dust and moister air in the wake of the surface-induced trough's
path on Friday. Surface winds will remain southeasterly at 10-15
mph today, gradually increasing to 10-20 mph and veering more from
the east from Thursday onwards.

In the upcoming days, expect a more seasonal weather pattern,
characterized by overnight and early morning showers moving inland
from the waters, followed by afternoon convective development
aided by local effects and diurnal heating. However, there is a
chance for increased shower activity, more pronounced in the
southern sections of Puerto Rico, portions of the U.S. Virgin
Islands, and local Caribbean waters on Thursday, but fast-moving
due to increasing winds. So far, expect limited excessive rainfall
impacts, ranging from ponding of water to localized urban and
small stream flooding. Friday's shower activity hinges on the
timing of moisture moving across the region, with current
indications suggesting that it will reach the local islands in the
afternoon and extend through late Friday night. Brief hazy
conditions are likely.

Due to reduced anticipated rainfall, clearer skies, and
southeasterly winds, there is a renewed concern for excessive heat
risks during the next few days. Heat index values could reach as
high as 108-111 degrees, primarily in northern Puerto Rico, where a
Heat Advisory is currently in place today.

&&

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

From Saturday into Sunday, model guidance (GFS and ECMWF) continues
to suggest the approach of an upper-level trough just east of the
region. This retrogressing TUTT will likely remain just at our east,
as the intensification of the mid to upper ridge over the western
Atlantic into the forecast area. In the lower levels, not a
favorable pattern for widespread shower activity is expected either;
according to the GFS, PWAT values will remain just at 1.5 inches.
The combination of the stable conditions and drier air aloft,
combined with the lack of deep tropical moisture across the islands,
will mainly drift a seasonal pattern across the islands. Therefore,
residents will mostly expect passing showers in the morning hours
over the windward sections and the localized afternoon local
convection.


By late Sunday, a surface low pressure developing well at our
southwest over the Caribbean will result in variable winds becoming
more from the east-northeast veering to the east-southeast. This
surface wind pattern will also reduce the pressure gradient,
reducing the wind velocity over the forecast. The predominant wind
pattern will be the east-southeast. Under this wind flow, deep
tropical moisture will filter. As a result, an increase in showers
is expected from late Monday into Tuesday due to this surface
perturbation. Discrepancies in the timing and the amount of moisture
remain in place from both global model guidance. However, the
forecast reflects the most possible scenario with the increase in
the available moisture.

&&

.AVIATION...Brief MVFR conditions are still possible across TJSJ,
TJPS and USVI terminals due to passing SHRA through 01/14Z and after
01/22Z. For TJBQ, afternoon SHRA/TSRA could also result in brief
MVFR conditions between 01/17-22Z. Light to calm and variable winds
below 8 knots, increasing to 8-12 knots with higher gusts and
significant sea breeze variations after 01/14Z.

&&

.MARINE...Recent CariCOOS buoy network observations around Puerto
Rico and the U.S. Virgin Islands continue to indicated wave
heights between 2-3 feet for buoys. After mid morning a minor
uptick in wind-driven waves is anticipated, driven by and expected
increase in winds speeds influence by the sea breeze.

A low-pressure system and its associated front, currently
positioned east of the U.S. are set to create a zone of strong
winds, generating a north-northwest swell that may reach our
local Atlantic waters by early afternoon on Saturday. Therefore
beachgoers and mariners should expect between 3 to 5 feet swells
with 10-12 seconds periods affecting mainly the Atlantic waters
and northern coast of Puerto Rico and the U.S. Virgin Islands.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
452 AM AST Thu Nov 2 2023

.SYNOPSIS...

A drier airmass will move out of the region, replaced by a more
moist airmass. As a result, the periods of sunshine in the morning
and the increase of moisture will trigger heat indices across the
northern areas of Puerto Rico, Culebra, and Vieques. Therefore, a
heat advisory is effective from 10 AM to 5 PM AST. The increase in
moisture will also enhance afternoon shower activity across
western and northwestern Puerto Rico. Tranquil marine conditions
will prevail until Friday when a northwesterly swell will reach
and spread across the local Atlantic waters.

&&

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

Today's main hazards revolve around the risk of excessive rainfall
and lightning at limited threat levels and excessive heat risks at
limited to elevated threat levels.

An analysis of overnight radar and satellite imagery indicated that
portions of *eastern Puerto Rico, Vieques, Culebra, and St. Croix
experienced showers, resulting minimal rainfall accumulations.
Overnight temperatures varied across the region, ranging from
around mid 60s across higher elevations to about 80s degrees
across windward areas and the local islands. Winds were generally
light and variable.

A dominant synoptic features transition continues, between an upper-
level ridge, positioned west of Hispaniola, and a retrogressive TUTT-
low and associated surface-induced trough, centered just east of the
Leeward Islands. While the ridge still has some influence, the TUTT-
low will likely create conditions marginally conducive to deep
convective development. The extent to which the TUTT-low will
propagate westward before the ridge remains uncertain, with the
scope of its influence aligned with the influx of tropical moisture
and further weakening of the trade wind cap.

At the surface, a drier airmass will continue to encompass the
region until a moist plume, steered into the area by increasing east-
southeast winds at 10-20 mph, will gradually degrade the pronounced
moisture contrast from today into Friday. So far, this influx of
tropical moisture, with precipitable water values increasing to
typical seasonal values around 1.5-1.8 inches, should favor more
frequent overnight and early morning showers moving over eastern
Puerto Rico and the U.S. Virgin Islands, followed by more pronounced
afternoon showers with isolated thunderstorm development over the
west-northwestern sections of Puerto Rico. Streamer-like showers
from the local islands and inland mountainous areas are also likely,
driven by the same more robust steering flow. These lines of showers
with possible isolated thunderstorms will affect portions of eastern
Puerto Rico and the San Juan metropolitan area. Excessive rainfall
impacts, as well as limited lightning hazard risks, are likely,
ranging from ponding of water to localized urban and small stream
flooding. Saturday's weather conditions hinge on the timing of
intermittent patches of drier air and moisture moving along the
periphery of a surface-induced trough, with current indications
suggesting that the moist air will reach the U.S. Virgin Islands in
the morning and Puerto Rico in the afternoon.

Due to the timing and coverage of the anticipated rainfall, expected
clearer skies, and predominantly east-southeasterly winds, there is
an ongoing concern for excessive heat risks during the next few
days. Heat index values could reach as high as 108-111 degrees,
primarily in western and northern Puerto Rico, Culebra, and Vieques,
where a Heat Advisory is currently in place.

&&

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

The long-term forecast remains on track. Model guidance (GFS and
ECMWF) continues to suggest a deep retrogressing upper-level
trough, reflected in all the levels. This upper-level trough will
linger just over our east due to the intensification of an upper-
level ridge just over the western Atlantic over the Hispaniola.
Meanwhile, as the TUTT interacts just east of the area, it will
induce a low-level trough. By Monday into Wednesday, as the TUTT
elongates in the upper levels, the axis of the surface feature
will linger over the east of the CWA, resulting in southeasterly
winds over the eastern PR and the U.S. Virgin Islands and
northeasterly over western Puerto Rico. This pattern will favor
shower and thunderstorm activity across the windward sections of
Puerto Rico and the U.S. Virgin Islands. According to The Gálvez-
Davison Index (GDI) (GFS), there is a potential for isolated
thunderstorms across the U.S. Virgin Islands. Although the
moisture field will be extensive, its models keep showing the bulk
of the moisture just east of the area. By late Wednesday into
Thursday, a broad building surface high pressure will spread into
the area, resulting in more east-northeasterly winds by Wednesday,
veering on Thursday, becoming more from the east. Under this wind
pattern and the surface high pressure, the islands will be trapped
under enough tropical moisture to result in a seasonal weather
pattern with showers AM in the eastern sections and PM showers
across the western interior.

&&

.AVIATION...

Brief MVFR conditions are still possible across TISX due to
passing SHRA/TSRA throughout the period. For TJSJ and TJBQ,
afternoon SHRA/TSRA could also result in brief MVFR conditions
between 02/16-22Z. Light to calm and variable winds below 8 knots,
increasing to 10-15 knots with higher gusts and sea breeze
variations between 02/14-22Z. Winds will become light to calm and
variable again after 02/22Z.

&&

.MARINE...

Bouy data around Puerto Rico and the U.S. Virgin Islands indicates
wave height between 2-4 feet. Today, mariners can expect an
increase in winds becoming moderate to locally fresh easterly
winds, resulting in locally high seas. Today, there is a moderate
risk of rip currents across all the northern coastal areas of the
islands.

An increase in wave height and breaking waves is expected as A
low-pressure system, and its associated front generate a north-
northwest swell that may reach our local Atlantic waters by early
afternoon on Saturday. Therefore, beachgoers and mariners should
expect between 3 to 5 feet of swells with 10-12 seconds periods
affecting mainly the Atlantic waters and the northern coast of
Puerto Rico and the U.S. Virgin Islands.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
505 AM AST Fri Nov 3 2023

.SYNOPSIS...Variable weather conditions are likely today into the
weekend, influenced by increased moisture levels and the proximity
of a TUTT low and associated surface-induced trough. Despite
anticipated rainfall and increasing easterly winds, there are
ongoing concerns regarding excessive heat risks, particularly
across northern Puerto Rico and Culebra, where Heat Advisories are
in effect. From today into Saturday, expect deteriorating marine
and surf zone conditions as a northerly swell spreads across the
local Atlantic waters. A series of surface-induced and mid-to-
upper-level troughs will likely increase the likelihood of showers
and thunderstorms and, thus, an increased risk of flooding by
early next week.


&&

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

Radar Doppler showed a few showers across the local waters,
streaming over the eastern section of Puerto Rico and the U.S.
Virgin Islands. Although the frequency of the showers was
significant, minimal rainfall accumulations were reported. Overnight
temperatures were in the lower 80s across the coastal areas and in
the upper 60s to the lower 70s across the mountains.

A variable weather pattern is forecast for the period due to the
presence of a retrogressing upper-level trough just east of the
region and a mid to upper-level established over the western
Atlantic. This ridge mentioned above has played an important role in
the westward progression of the TUTT, leaving the islands under a
convergence side of the west side of the retrogressing TUTT. As we
move to the weekend, the interaction between the TUTT and the upper
to the mid ridge will reflect on the surface pattern, inducing a
surface trough just south of the region, over the Caribbean. This
surface feature expects to relax the pressure gradient, resulting in
more gentle to light winds for late Saturday into Sunday. Under this
evolving pattern, at the surface, pockets of tropical moisture will
filter in from time to time during the period.

Today, surface winds will persist from the east, dominated by a
surface high pressure over the eastern Atlantic, spreading into the
Caribbean. Under this wind flow, a drier airmass with PWAT of 1.20
inches and Saharan Dust Particles, as indicated by the derived
satellite GOES imagery, will fill in. The presence of the Saharan
Dust particulate will result in brief hazy skies. Although drier
conditions will remain for a period in the morning hours, another
slot of tropical moisture is forecast to reach the islands in the
afternoon hours, increasing the potential for showers and
thunderstorms.

According to the GFS model guidance, a more moist pattern is
forecast for Saturday to Sunday, with PWAT values from 1.5 to 1.7
inches. This increase in humidity and the surface wind pattern will
result in easterly trade wind showers in the morning hours and PM
afternoon convection across the interior and western interior. Given
some colder temperatures at the mid-levels, some pulses of isolated
thunderstorms. During the period, there is a potential for excessive
rainfall impacts, as well as limited lightning hazard risks,
resulting in ponding of water to localized urban and small stream
flooding.

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

According to the latest model guidance, which has remained
relatively consistent over the past few days, expect wet and
unsettled weather conditions to persist throughout the long-term
forecast period. The synoptic pattern early in the week is
complex, transitioning from the influence of an upper-level ridge
to a strong mid-to-upper-level polar trough. This trough will
remain in close proximity to the north of the local islands until
midweek, replaced by another weaker trough that will likely sweep
eastward across the northern Caribbean through the latter part of
the workweek. These features will maintain a relatively weak
trade wind cap inversion, if significant, and create marginally
unstable conditions conducive to deep convective development. At
the lower levels, a surface-induced trough and subsequent easterly
disturbances will maintain an influx of tropical moisture.
Initially, under light winds with a south-southeasterly component,
yielded by the trough, gradually increasing and veering more from
the east from Thursday onwards.

The combination of multiple elements in this scenario, marked by
persistently above-normal precipitable water values exceeding 2
inches, relatively cooler mid-level temperatures reaching as low
as -7 degrees Celsius, and a light steering flow, suggests the
likelihood of increased shower and thunderstorm activity. The
Galvez-Davison Index supports this trend, and such slow-moving
thunderstorms could result in excessive rainfall and lightning
impacts. There is also a likelihood of excessive heat hazard
risks, especially in areas experiencing extended rain-free periods
in the early part of the week.


&&

.AVIATION...Mainly, VFR conditions will prevail throughout the
period. Winds will continue from the E at 8 knots until 03/14Z,
increasing up to 15 knots with gusty winds and land breeze
variation. An increase in SHRA is expected for the afternoon
hours, resulting in lower ceiling and brief MVF conditions from
03/18 to 03/22Z across TJSJ & TJBQ.


&&

.MARINE...Recent observations from the CariCOOS buoy network in
the vicinity of Puerto Rico and the U.S. Virgin Islands have
shown consistent marine conditions with wave heights ranging from
2 to 5 feet.

Marine conditions will deteriorate as a northerly swell propagates
across the local Atlantic waters from today into Saturday. As a
result, a Small Craft Advisory is currently in place due to the
anticipated increase in wave heights, which may reach up to 7
feet. The advisory comes into effect this evening for offshore
Atlantic waters, continuing through Saturday afternoon.

There is a moderate risk of rip currents for beaches of northern,
eastern, and southeastern Puerto Rico, Vieques, Culebra, and all
the U.S. Virgin Islands, where life-threatening rip currents are
possible. The expected swell will likely increase rip current
threat levels, mainly across north-facing beaches of Puerto Rico,
by Saturday into Sunday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
443 AM AST Sat Nov 4 2023

.SYNOPSIS...

An easterly breeze will bring passing showers across portions of
eastern Puerto Rico and the Virgin Islands. Conditions will not
favor strong showers, but local effects will still trigger
afternoon activity across western Puerto Rico. Moisture will begin
to increase later in the weekend and early next week, with another
peak of moisture reaching the islands by Thursday. A northerly
swell will maintain hazardous seas across the offshore Atlantic.

&&

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

Minimum temperatures were between the mid 70s to low 80s across the
lower elevations, and from the upper 60s to low 70s across the
higher elevations. Scattered showers were noted across the Atlantic
and Caribbean waters, with a few moving a along portions of
northeastern and southeastern PR, as well across St. Croix and St.
John through the night. The Doppler radar estimated up to a quarter
of an inch of rain with this activity.

A building mid-to upper-level ridge over the western Caribbean will
extend over the local area during the next couple of days.
Meanwhile, a TUTT-low and associated surface trough are expected to
meander just east of the Lesser Antilles through the short term
period. This scenario will promote warming of the 500 mb
temperatures, about minus 1 degree each day, rising from -6.5C
today to near 3.5C by Monday morning. Also, as the region remains
under the subsidence side of the upper level low, drier air and
stable conditions aloft are expected. Having said that, the trade
wind cap will continue today with low-level winds from the east to
northeast at 18-22kt, promoting an advective pattern through the
morning hours between the USVI and eastern PR. Winds will
gradually decrease on Sunday and further on Monday as the surface
trough moves over the Lesser Antilles. In terms of moisture
content, below normal precipitable water content is expected
today, but slowly increasing to near normal levels by late Sunday
and Monday. In general, locally induced afternoon convection is
expected to develop mainly over portions of the interior and
western PR each day. Although warmer 500 mb temps are expected,
the daytime heating and decreasing trades on Sunday and Monday
should allow for some showers to grow into thunderstorms. Across
the USVI, Vieques, and Culebra, streamers are expected to develop
downwind of the islands with minor rainfall accumulations over
land areas.

Maximum temperatures should reach the upper 80s and low 90s across
the lower elevations, with heat indices ranging from the upper 90s
to near 108 degrees each day.

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

The pressure gradient will remain weak and from the south-southeast
through early next week as a mid to upper level polar trough
continues to move north of the islands. By mid-week, the trade winds
will recover while shifting from the east in response to a ridge
cell stretching into the eastern Caribbean. Simultaneously, a low
level disturbance will begin to cross the local islands, enhancing
the potential for showers and thunderstorms. Although the global
models show some disagreement in timing and coverage, both show an
increase in Probability of Precipitation lasting into Friday.
Additionally, a ridge will build and migrate from the southeastern
coast of the United States into the western Atlantic, tightening the
gradient and thus increasing the wind speeds. Dry air will follow,
and the ridge will hold at the mid levels, so weather conditions
will improve by then.

&&

.AVIATION...
Mainly VFR conditions expected across all terminals
through the forecast period. VCSH at TJPS/TJBQ this afternoon due to
locally induced SHRA/TSRA over the interior and western PR. ENE
winds at 12-16 kt with sea breeze variations and higher gusts after
04/14z.


&&

.MARINE...
Recent buoy observations show seas increasing to around 5 feet
across the Atlantic coast. A northerly swell will continue to
arrive today, resulting in hazardous marine conditions, mainly for
the offshore Atlantic waters. Conditions should begin to improve
by midweek.

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
536 AM AST Mon Nov 6 2023

.SYNOPSIS...A low level trough over the eastern Caribbean will
bring a wet period by mid to late week. An upper level ridge is
forecast to build later in the period over the central Caribbean,
promoting fair weather conditions during the weekend. A broad
surface high pressure building over the central Atlantic will
promote moderate to fresh east to southeasterly trades during the
second part of the week. Light winds will prevail through Tuesday.


&&

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

After the showers over northwestern Puerto Rico dissipated,
conditions improved across the region. Only a few showers developed
over the local waters, but none moved over land. A high pressure
system at the low and mid levels, centered over the eastern Atlantic
will maintain the winds from the southeast today, and a little more
from the south on Tuesday. Additionally, there is a mid to upper
level trough moving from the eastern coast of the United States into
the western Atlantic. These features will maintain the steering flow
weak. The southerly flow will stretch into the mid levels of the
atmosphere, so temperatures will rise above normal these days. In
general,heat indices of 102 to 107 degrees are expected with
isolated up to 108 degrees across northern Puerto Rico.

The most recent satellite imagery show a small patch of clouds
approaching the local islands. The high resolution models show
passing showers affecting eastern and southern Puerto Rico and the
U.S. Virgin Islands today. In the afternoon, additional showers are
expected to develop along the Cordillera Central and the northern
half of Puerto Rico. Some of these showers may be strong enough to
lead to urban and small stream flooding. By tomorrow into midweek,
moisture will influx from the Caribbean Sea into the islands as a
surface trough approaches. A bunch of clouds and increasing showers,
as well as isolated thunderstorms are anticipated for this period.
The users should get ready for a wet period, with areas experiencing
wet roads, ponding of water in roadways and some urban and small
stream flooding as well.

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

A low-level trough will bring above normal precipitable water
content between 2.00-2.30 inches through at least Friday across
the local area. Shower and thunderstorm development will remain
high across portions of Puerto Rico and the U.S. Virgin Islands,
and as well across the regional waters. Latest model guidance
suggest that the bulk of the moisture content should remain just
south of the islands, with the ECMWF Extreme Forecast Index
favoring Thursday and Friday as the wettest period during the long
term period. Under east to southeasterly steering winds, the
highest rainfall accumulations are expected across the eastern and
southern sections of PR. Urban and small stream flooding is likely
with this activity, and if the midweek forecast materializes,
flash flooding and mudslides in areas of steep terrain can be
expected.

A building mid to upper level ridge over the central Caribbean and
a broad surface high pressure over the Atlantic basin will then
promote a drying trend during the weekend into early next week.
However, trade wind showers will move at times across the USVI and
eastern sections of PR under an advective pattern during the
night, and shallow afternoon convection is expected to develop
over the western sections of PR each day.


&&

.AVIATION...Mainly VFR conditions are expected to prevail today. However,
increasing SHRA across the Caribbean Sea may reach the USVI and PR
terminals after 14Z. After 17Z, additional activity is expected
across the Cordillera Central, causing mountain obscuration. All
this activity could cause periods of reduced VIS and low ceilings.
Winds will be from the SE at 6-10 kts.


&&

.MARINE...Small pulses of northerly swells will continue through
the week. Seas are expected to remain under 6 feet. Light to
moderate trades expected through Tuesday, becoming moderate to
fresh later in the forecast period. A moderate risk of rip
currents will continue across the east and north facing beaches of
the islands for the next several days.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
517 AM AST Tue Nov 7 2023

.SYNOPSIS...
A surface trough over the eastern Caribbean will promote a wet
weather pattern through the end of the workweek. An upper level
ridge is forecast to build over the central Caribbean, promoting
fair weather conditions during the weekend into early next week. A
broad surface high pressure building over the western and central
Atlantic will promote moderate to fresh east to southeasterly
trades during the second part of the week.


&&

.SHORT TERM...Today through Thursday...
Plenty of moisture has been covering the eastern Caribbean. Since
early in the night, showers have been developing and moving
across the U.S. Virgin Islands (mainly St. Croix) and over
southeastern Puerto Rico. Some areas around Arroyo to Maunabo
collected up to one inch of accumulation.

The pressure gradient remains loose, resulting in a weak steering
flow out of the south to southeast. This is in response to a mid to
upper level trough now north of the Greater Antilles, and a high
pressure system over the eastern Atlantic. At the surface, a low
level disturbance/trough will be crossing the area through the end
of the workweek. This influx of low level moisture will again
combine with local effects to generate showers along the Cordillera
Central, then moving over the northern half of Puerto Rico
(including the San Juan metro area). With weak winds, the showers
may linger, and urban flooding can be anticipated, especially in
areas with poor drainage. The Virgin Islands and southern Puerto
Rico will receive frequent passing showers, so urban flooding cannot
be ruled out.

On Wednesday and Thursday, as a a ridge builds just east of Florida,
the trade winds will recover a more easterly component. Moisture,
however, will remain above normal, and a showery pattern is expected
to persist. Additionally, a shortwave trough will dig over the
western Caribbean, increasing instability aloft. Therefore, the
potential for thunderstorms should be higher these days.


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

Lingering moisture on Friday will continue to promote wet and
unstable conditions across the local area. Therefore, shower and
thunderstorm development will remain high across portions of
the islands and local waters. Stronger trades from the east to
southeast and the moist environment will increase the frequency
of showers across the USVI and eastern sections of PR through
Friday morning. Urban and small stream flooding is likely with
this activity, and if the midweek forecast materializes, flash
flooding and mudslides in areas of steep terrain can be expected.

A building mid to upper level ridge over the central Caribbean and
a broad surface high pressure spread across the Atlantic basin
will promote a drying trend during the weekend into early next
week. However, trade wind showers will move at times across the
USVI and eastern sections of PR under an advective pattern during
the night, followed by shallow afternoon convection over the
western sections of PR each day.


&&

.AVIATION...
SHRA will be moving across the Caribbean Sea today. Additional
activity is expected after 17Z across the Cordillera Central, also
affecting TJBQ and TJSJ terminals. Periods of reduced VIS and low
ceilings, as well as mountain obscuration are expected, especially
from 17-22Z. SHRA will linger after that across the USVI terminals.
Winds are on the light side, out of the SSE at 4-8 kts, with
stronger gusts.


&&

.MARINE...
A small (3-4 ft) long period (14/15 seconds) northeasterly swell
will continue to spread across the Atlantic waters and passages
today. This will cause life-threatening rip currents across the
northern beaches of Puerto Rico, and a High Rip Current Risk
(CFWSJU) is in effect through this afternoon. Light east to
southeast winds will continue today.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
448 AM AST Wed Nov 8 2023

.SYNOPSIS...A surface trough over the eastern Caribbean, and an
upper level trough north and west of the region will continue to
promote wet and unstable conditions through the rest of the
workweek. A mid-to upper-level ridge will build over the local
area from the west later in the weekend into early next week.
A surface high pressure over the western Atlantic will promote
moderate to fresh trades from Thursday onwards.


&&

.SHORT TERM...Today through Friday...
A trough system over the eastern Caribbean continued to generate
showers and some thunderstorms during the night hours, but mostly
over the open waters. A few showers did reach the U.S. Virgin
Islands, with the highest accumulation over St. Croix. This
unsettled pattern is expected to continue today across the islands,
where the elevated risk for flooding will persist. The most recent
satellite-derived precipitable water value imagery show values well
above the climatological value for the region. At the upper level,
the trough is enhancing instability. Additionally, the wind flow
remains on the light side, at about 8-10 kts out of the southeast.
All these ingredients will combine once more to create abundant
showers across the Cordillera Central, stretching into western and
northern Puerto Rico, including the San Juan metro area. Additional
showers will also stream around and over the U.S. Virgin Islands,
Vieques, Culebra, and east-southeast Puerto Rico. Since some of
these soils are already saturated, mudslides can occur in higher
grounds, as well as rapid river rises and water surges.

By the end of the workweek, moisture values will remain enhanced,
but a ridge will begin to build north of the region at the surface
and at mid-levels. This will cause the winds to shift from the east,
and they will become stronger too. With stronger winds, showers
will move faster, but will still leave wet roads and ponding of
water. Also, local effects will continue each afternoon,
maintaining elevated the risk for urban and small stream flooding.

.LONG TERM...Saturday through Wednesday...
A building mid-to upper-level ridge over the central Caribbean and
western Atlantic will promote drier air aloft and warming of the
500 mb temperatures. Meanwhile, a broad surface high pressure is
expected to build across the western and central Atlantic during
the weekend into early next week, promoting stronger trades across
the northeastern Caribbean. Embedded in this flow, patches of
low-level moisture content will move from time to time from the
east. This will promote an advective weather pattern across the
U.S. Virgin Islands and eastern Puerto Rico during the night and
early morning hours, followed by diurnally induced afternoon
thunderstorms over western Puerto Rico each day. Global models
solutions are in disagreement with the synoptic weather pattern by
midweek, with the GFS developing a surface low pressure west of
the region with an extensive moisture field over the local area,
and the ECMWF suggest a frontal boundary sinking from the Atlantic
waters into the northeastern Caribbean with drier air aloft.
Therefore, the current forecast is more consistent with
climatology, but adjustments can be introduced later this week.


&&

.AVIATION...
Mainly VFR conditions before 17Z. From 17Z to 22Z, SHRA and TSRA are
expected to develop along the Cordillera Central, reaching TJBQ
and TJSJ. This will result in periods of reduced VIS and low
ceilings. Passing SHRA will also affect the USVI terminals. Winds
will be from the SE at 8-10 kts, with strong gusts.


&&

.MARINE...
Seas are forecast to remain at 5 feet or less through Wednesday.
Fresh trades (up to 20 kt) during the latter part of the week
will cause choppy conditions and seas will build around 6 feet,
mainly across the offshore waters and passages. A moderate risk of
rip currents will prevail across the east and north facing beaches
of the islands.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
446 AM AST Thu Nov 9 2023

.SYNOPSIS...
Expect a wet and unsettled weather pattern throughout the weekend
as plenty of moisture interacts with a short-wave trough. Due to
saturated soils, there is an increased potential for urban, river
and life-threatening flash flooding, as well as mudslides and
rockfall. A drying pattern will start late in the weekend into
next week. Breezy conditions are expected later today, Small Craft
Should Exercise Caution. There is a moderate risk of rip currents
for the north oriented beaches of Puerto Rico from Rincon to
Ceiba, as well as for most of Culebra's beaches, the northern and
western beaches of St. Thomas and the easternmost beaches of St.
Croix.

&&

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

A very active night unfolded, yielding several Flood Advisories and
Flash Flooding for municipalities across northern Puerto Rico, with
the latter issued for Bayamon, Catano, Guaynabo, and Toa Baja. Until
4 AM AST, Doppler radar estimated between 1-3 inches of rain fell,
with isolated higher amounts, during that time across that area.
Convective activity continued developing and organizing throughout
the night over the Caribbean waters and eastern/northeastern Puerto
Rico. Low-level convergence along with divergence aloft prevails
over the region. Therefore, expect shower and thunderstorm
development to persist through the morning hours, with an advective
pattern impacting the eastern third of Puerto Rico and lesser
islands.

The polar trough that has been influencing the local weather pattern
will continue lifting north. However, a short-wave trough is
currently developing aloft stemming from the aforementioned polar
trough. Model guidance suggests this short-wave trough will
strengthen as it meanders over the local islands through at least
Saturday. This feature will maintain increased vorticity aloft, 500
mb temperatures between -8 to -7 degrees Celsius, and near normal to
above normal lapse rates. Additionally, 250 mb heights and 1000-
500mb thicknesses will fall during this time promoting favorable
weather conditions for deep convective development. This favorable
dynamic setup will combine with plenty of tropical moisture. The
latest imagery from the Polar Blended-Percent of Normal Total
Precipitable water (TPW) indicates between 140%-150% of above TPW
spread between Puerto Rico and the northeastern Leeward Islands.
Precipitable water values above 2.0 inches will prevail for the
duration of the short-term forecast. Both ECMWF and GFS Galvez-
Davison Index indicate substantial low-level moisture convergence
with isolated to scattered thunderstorms capable of producing heavy
rain every day.

Therefore, expect a wet and unsettled weather pattern through the
weekend as plenty of moisture interacts with the short-wave trough.
Due to saturated soils, there is an increased potential for urban,
river and life-threatening flash flooding, as well as mudslides and
rockfall. Please continue to monitor for any advisories or warnings
issued by our office as this event unfolds.

&&

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

Current model guidance indicates a drying pattern for the long term
period. To start the next week precipitable water (PWAT) values will
still be at around 1.8 to 2 inches, at the higher end of normal
values to slightly above normal values for this time of the year.
However, drier air will filter in late Sunday and during the
workweek, with only patches of low-level moisture pushing PWAT
values to around 1.75 inches. Low concentrations of Saharan Dust
will also filter into the area through at least Tuesday. A mid-to
upper-level ridge over the central Caribbean will build throughout
the period, promoting drier air aloft. At surface level a high
pressure system will build across the western and central Atlantic
into early next week, promoting stronger trade winds across the
northeastern Caribbean. Uncertainty remains in the forecast due to
discrepancies between the GFS and the ECMWF. The GFS develops a
surface low across the western Caribbean which influences moisture
content and wind direction across the local islands late in the
period. On the other hand the ECMWF suggest drier air aloft. The
forecast remains leaning towards climatology for the late long
term period, please stay tuned for future updates. Passing shower
activity is forecast across eastern Puerto Rico and the USVI
during the night and early morning hours. Afternoon shower and
thunderstorm activity is forecast mainly for western Puerto Rico
each day, due sea breeze convergence and local effects.

&&

.AVIATION...
An active weather pattern will persist through the forecast
period. Sct-Num SHRA/SCT-TSRA will affect the local flying area
today. TEMPO MVFR/IFR conds and widespread mtn obscurations can be
expected. Variable sfc winds from up to 10kt until 09/14Z then 10
to 15 kt thereafter with sea breeze variations. Locally higher
gusts near/in TSRA throughout the period.

&&

.MARINE...
CARICOOS buoys indicate around 3 foot wave heights across
nearshore waters. Buoys near San Juan, Arecibo and Rincon indicate
a minor swell with periods of 11-13 seconds. This swell will
slowly dissipate throughout the rest of the week. A developing
surface ridge in the western Atlantic will bring moderate to
locally fresh easterly winds across the local waters starting
today. Small Craft Should Exercise Caution. These choppy
conditions are expected through the weekend. There is a moderate
risk of rip currents for the north oriented beaches of Puerto
Rico from Rincon to Ceiba, as well as for most of Culebra's
beaches, the northern and western beaches of St. Thomas and the
easternmost beaches of St. Croix.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
343 AM AST Fri Nov 10 2023


.SYNOPSIS...
Issued at 339 AM AST Fri Nov 10 2023

Wet and unsettled weather conditions are expected through at least
early this weekend as a short wave trough gradually pulls away from
the area. A more seasonal and stable weather pattern will return by
early next week. Therefore, any activity will become more localized
in the afternoon, in inland and western areas of Puerto Rico.

&&

.SHORT TERM...Tonight through Sunday...

Upper level trough will linger just north and west of the forecast
area through Saturday then gradually erode while lifting northwards
by Sunday. Broad surface high pressure ridge spread across the west
and central Atlantic and north of the region will maintain moderate
to locally strong easterly winds through much of the weekend thus
favoring locally breezy conditions.

For the rest of today and into Saturday...The interaction of the
upper trough and good low level moisture pooling and convergence,
will continue to promote unstable conditions across the region
during the rest of the day and at least into Saturday. This will
support and maintain favorable conditions for additional showers and
isolated thunderstorms development. The easterly winds are however
expected to increase across the region, as the local pressure
gradient tightens over the next few days, so breezy conditions are
also forecast. Expect afternoon convection to develop and quickly
stream westward over the interior and west to northwest sections of
Puerto Rico, and also on the west end and downwind of the U.S.
Virgin Islands. Some afternoon moisture entrainment and streamer
like convection can therefore be expected by late morning and during
the afternoon hours. This will lead to urban and small stream
flooding and possible flash flooding along with mudslides in areas
of steep terrain, as well as area in the east and southeast where
there have been significant rainfall accumulations in recent days.

On Sunday a gradually erosion of low level moisture is so far
forecast as the upper trough fills and lifts northwards and is
replaced by mid to upper level ridging. However, although overnight
and early morning showers will be less frequent, do expected
sufficient moisture to linger across the region through the weekend
to aid in the development of afternoon convection especially over
the central and west sections of Puerto Rico. Lesser shower activity
is so far expected for the U.S. Virgin Islands by then.

&&

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

The expected weather conditions have not changed much for the long-
term forecast period, with mid to upper-level ridging remaining as
the dominant feature for the early part of the week. At the surface,
weak perturbations embedded in the trades are expected to bring
clusters of clouds and showers as they propagate across the region.
Although this activity will mainly favor the US Virgin Islands and
portions of eastern Puerto Rico, an increase in the general wind
flow due to the tightening of the local pressure gradient could
support fast-moving showers reaching portions of the interior
through the workweek. Western Puerto Rico will likely experience
shallow afternoon convection each afternoon due to sea breeze
convergence followed by clearing during the evening and overnight.

Uncertainty increases substantially by the end of the long-term
forecast as it will depend on the evolution of a potential low-
pressure system over the southwestern Caribbean Sea. The National
Hurricane Center is monitoring this scenario, although the latest
Tropical Weather Outlook has a low chance of formation in the next
seven days. The GFS model is, as typical, very bullish in developing
this system while shifting northward and inducing southerly winds,
advecting plenty of tropical moisture over the region. ECMWF has a
much weaker system with a similar track. Nevertheless, both
scenarios are indicating a wet and unsettled weather pattern by the
end of the workweek into the weekend. Stay tuned for further
updates!

&&

.AVIATION...
(06Z TAFS)
Issued at 339 AM AST Fri Nov 10 2023

Prevailing VFR conds at all terminals thru 10/14Z. However, SCT
SHRA/ Isold TSRA will cont to dvlp ovr regional waters and en
route btw islands due to the interaction of an upr level trough
and high moisture pooling along a shearline just north of the
region. Brief MVFR conds will be psbl with passing SHRA/Isold
TSRA. Mtn Top obscr will persist ovc E PR due to low cld lyrs and
-SHRA til 10/13Z. L/lvl wnd fm E 15-20 kts BLO FL120 then veering
and gradually bcmg more fm SW ABV. Sfc wnd calm to lgt/vrb, incr
fm E 12-15 kt with hir gusts and some sea breeze variations.

&&

.MARINE...
Issued at 339 AM AST Fri Nov 10 2023

Choppy seas are expected as winds from the east at 15 to 20 knots
continue across the regional waters. Seas up to 6 feet over the
offshore waters and passages and 5 feet or less elsewhere. There is
a moderate risk of rip currents for north-, east-, southeast-facing
beaches of PR, all beaches of Culebra, and most beaches in
Vieques. The USVI will also have a moderate risk of rip currents
for most of its beaches.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
425 AM AST Sat Nov 11 2023

.SYNOPSIS...

Wet and unsettled weather conditions will continue today with the
heaviest rain expected during the afternoon across the central
interior and western sections of PR. A more seasonal and stable
weather pattern will return by tomorrow. Potentially there is a
trend toward another wet, unstable round of weather next weekend
due to the possible development of an area of low pressure a good
distance west of the local islands. Choppy conditions exist
across the regional waters over the next few days due to moderate
to locally fresh easterly winds.

&&

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

Throughout the night, showers and isolated thunderstorms developed
and organized across the coastal Caribbean and Atlantic waters, with
some impacting coastal areas across northeastern and southern Puerto
Rico. The mid- to upper-level trough continued promoting unsettled
weather conditions while combining with enough columnar moisture.
Expect activity to persist through the morning hours with eastern
Puerto Rico, Vieques, Culebra, and USVI observing the most activity.

The present synoptic pattern will gradually change during the short-
term period as the trough aloft moves northwestward and a mid-level
ridge builds through Monday. Nevertheless, lingering effects from
the trough aloft will provide sufficient instability for deep
convective activity this afternoon. Throughout the period, the well-
above-normal tropical moisture will erode, declining and remaining
within the 25th and 50th percentile of the climatological normal by
Monday. Low-level wind and steering pattern will become more east-
southeast today and remain so through Monday. However, the pressure
gradient between the high pressure north of the region and low
pressure over Colombia will continue to support breezy wind
conditions at least through the weekend.

Therefore, during the afternoon hours, expect sufficient moisture
availability to aid in locally and diurnally induced afternoon
convection. This should be focused on parts of the central interior
and western sections of PR steered by the fairly fast trade wind
flow. Periods of locally heavy rains over these areas may lead to
urban and small stream flooding as well as ponding of water on roads
and in poor drainage areas with mudslides still possible in areas of
steep terrain.

By Sunday, as previously mentioned, the overall weather pattern is
forecast to be more seasonal. However, the occasional surges of
additional moisture embedded in the trades will be sufficient to
support more frequent evening and morning showers over the coastal
waters and east sections of Puerto Rico and the USVI. This will be
followed by locally and diurnally induced afternoon convection
mainly over the western sections of Puerto Rico although some shower
development will remain possible in and around the San Juan metro
and mainly downwind and on the west end of the USVI. The heaviest
rainfall should however be over central and west PR where urban and
small stream flooding will remain possible. The USVI should
experience brief isolated to scattered afternoon showers but no
significant rainfall accumulations are so far expected during the
period at this time. Mainly fair weather conditions can be expected
by Monday, with a few passing showers over windward coastal areas in
the morning hours followed by afternoon diurnally induced convection
out west.

&&

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

A seasonal pattern of passing showers and afternoon convection is
expected for the first half of the week as a mid to upper-level
ridge remains in place over the Caribbean Basin. A steady east-
southeasterly wind flow with seabreeze variations will prevail
bringing warm afternoons and moisture convergence across western
Puerto Rico which will enhance the chance of rainfall. A clearing of
skies is likely each evening throughout the next morning.

Thursday onward conditions will start to become influenced by the
potential development of a low-pressure system across the
southwestern Caribbean Sea. GFS model guidance currently has this
system developing into a hurricane that will move to the northeast
between Cuba and Hispanola, then out into the western Atlantic by
the weekend. ECMWF models are not in agreement with this
solution, however the National Hurricane Center currently has a
thirty percent chance of development over the next 7 days for this
area.

This scenario would bring a quite a wet pattern Friday onwards as
southerly flow brings moist air across the region as the system
travels a great distance northwest of the islands. An increase of
cloud coverage and rain is to be expected if this holds true. Stay
tuned for further updates regarding the weather for next weekend.

&&

.AVIATION...

SCT-SHRA/SHRA ovr regional waters and enroute btw islands and
-RA/VCTS at TJSJ/TJPS til 11/14Z. Winds fm ESE at 12-20 kts with sea
breeze variations and higher gusts aft 11/14Z. Aftn convection
expected fm 11/17-22z mainly downwind fm the the USVI and El Yunque
which may impact TIST/TISX/TJSJ. Mtn Top obscr and SHRA/Isold TSRA
may also develop across the Central mtn range of PR and over W PR
with VCTS at TJBQ.
&&

.MARINE...

Moderate to locally fresh easterly winds continue to produce
choppy seas of up to 6 feet across most of the offshore waters.
Therefore, small craft operators should exercise caution. The risk
of life- threatening rip currents remains moderate across the
northern, eastern, and southern facing beaches of Puerto Rico,
Vieques, Culebra, and the U.S. Virgin Islands.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
424 AM AST Sun Nov 12 2023

.SYNOPSIS...Breezy conditions and a seasonal pattern of scattered
showers, and maybe a few isolated thunderstorms, is possible
throughout the next few days. Thursday night onward conditions
will likely begin to deteriorate as a low pressure system
develops across the western Caribbean Sea and migrates to the
northeast across eastern Cuba and Hispanola. Moderate to locally
fresh winds are causing hazardous marine conditions, with 7 foot
seas for the Caribbean Offshore waters and the Mona and Anegada
Passage.


&&

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

An improvement in weather conditions is forecast to prevail for the
short-term period. For today, according to GOES-16 Total
Precipitable Water (PWAT) imagery, values range between 1.7 to 2.0
inches across the local islands, with the moister area across the
Caribbean waters and Mona Passage. However, there is an area with
PWAT values between 1.30 to 1.40 inches that is currently located
just north of the Leeward Islands. The easterly trades will advect
this drier airmass over the local islands throughout the day.
Meanwhile, the upper-level trough is expected to continue its
westward path while a building ridge will promote stable conditions
aloft. As a result, we will be transitioning to more fair weather
conditions.

During the morning hours, fragments of clouds will move across the
region with passing showers expected to move over the local waters
and windward sections of the islands. With the expected synoptic
pattern, limited and short-lived activity will dominate the region.
However, the local effects and diurnal heating will be enough for
scattered showers, and maybe a few isolated thunderstorms, over
western sections of Puerto Rico, resulting in ponding of water in
roadways and poor drainage areas.

On Monday, the mid-upper ridge will slightly strengthen over the
CWA, resulting in a weak trade wind inversion cap over Puerto Rico
and local islands. This will promote drier air and stable conditions
aloft. The mid-level relative humidity is expected to plummet and
range between 10-30% through Tuesday. Nevertheless, moisture
embedded in the easterly trades will maintain enough low-level
moisture availability throughout the period. Therefore, diurnal
heating and local effects will promote afternoon convection for the
interior and western sections of Puerto Rico each afternoon.

The surface high pressure across the western Atlantic and the low
pressure over central Caribbean waters will maintain a strong
pressure gradient across the local area today. Therefore, breezy
wind conditions will persist today and diminish somewhat by Monday
as the pressure gradient relaxes.

&&

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

The development of a low pressure system in the western Caribbean
and a ridge moving off the eastern coast of United States will
maintain a steady moderate to fresh trade wind regime throught the
surface to mid-levels. In combination with climatologically normal
precipitable water values should bring passing showers and shallow
afternoon convection on Wednesday and Thursday. However, models seem
consistent on the development of an area of low pressure in the
southwestern Caribbean which will begin to deteriorate local
weather conditions beginning Thursday night as moist air begins to
move across the islands. On the bright side an upper-level ridge
does remain in place over the area throughout this time, which may
aid in helping stabilize conditions.

Current GFS model has two main distinct centers of low pressure by
Saturday as this system migrates to the northeast, passing through
eastern Cuba and Hispanola. It is possible that the close proximity
of the lower part of the system may bring strong winds and very
unstable conditions on Saturday through Sunday. As southerly winds
will prevail from this, numerous passing showers and scattered
thunderstorms across the local waters and overland are likely if
this scenario remains. This may bring the risk of flooding,
lightning, and strong winds across the area next weekend and cause
seriously hazardous marine conditions. Currently the National
Hurricane Center has a 40% chance of cyclone formation in the next 7
days for this area of interest, so stay tuned for further updates on
the development and impacts for the local islands.


&&

.AVIATION...

VFR conditions expected across the local terminals. VCSH expected at
TJSJ/TIST/TISX until 12/14Z. Aftn convection fm 12/17z-22z would
result in VCSH mainly at TJBQ. SCT SHRA en route btw islands
possible. Wind will remain blo 10kt, increasing btw 15-20 KT fm ESE
with higher gusts and sea breeze variations.

&&

.MARINE...

Moderate to locally fresh easterly winds continue to produce a local
wind swell causing choppy seas of up to 7 feet across the Anegada
Passage, Caribbean Waters, and Mona Passage and up to 6 feet mostly
elsewhere. Therefore, a Small Craft Advisory is in effect for the
mentioned zones therefore small craft operators should exercise
caution. The risk of rip currents remains moderate across mostly all
beaches of Puerto Rico and the USVI as windy coastal conditions
continue.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
510 AM AST Tue Nov 14 2023

.SYNOPSIS...
Issued at 425 AM AST Tue Nov 14 2023

Passing trade wind showers will give way to breezy conditions with
excessive rain Thursday night. Wet and breezy conditions will
continue through Sunday. Winds will subside on Sunday, but
excessive rains will likely continue through Tuesday of next week.

&&

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

Today's main hazards revolve around excessive heat risks at limited
threat levels. Flooding and lighting hazards risks will likely
become elevated by Thursday.

An analysis of overnight radar and satellite imagery indicated that
portions of Puerto Rico's eastern half, Vieques, Culebra, and the
U.S. Virgin Islands experienced showers, resulting in radar-
estimated rainfall accumulations of up to a quarter of an inch
around Sierra de Luquillo in eastern Puerto Rico. Overnight
temperatures varied across the region, ranging from around 65
degrees across higher elevations to about 80 degrees across eastern
Puerto Rico and the local islands. Winds were generally light and
variable.

Before describing the expected weather pattern, it is essential to
emphasize the likelihood of transitioning from drier and stable
weather to wetter and unsettled conditions during the short-term
forecast period. A mid-level ridge will support a weak trade wind
cap inversion, maintaining generally stable conditions aloft and
trapping the best moisture at lower levels. In the meantime, a
developing low pressure moving northeastward over the central
Caribbean Sea will gradually push the ridge eastward, causing
further weakening of the trade wind cap inversion. As the surface
high pressure to the north over the western Atlantic weakens and
gives way to independently developing low-pressure systems to the
west, the prevailing easterly winds will shift more from the
southeast by Thursday. Concerning moisture availability,
persistent drier air will maintain normal to below-normal moisture
levels through Thursday morning, with precipitable water values
barely reaching 1.5 inches. However, as winds shift to a more
southeasterly direction, an increase in moisture advection is
anticipated, leading to precipitable water values rapidly
increasing to above-normal levels, reaching around 2.0-2.2 inches
by Thursday night.

For today through Thursday morning, expect mainly fair weather
conditions, with prolonged clear skies periods and limited shower
activity. Passing trade wind showers will likely impact eastern
Puerto Rico and the U.S. Virgin Islands during the overnight and
early morning hours. Subsequently, driven by diurnal heating and
local effects, limited and highly localized convective
development is likely over the far western sections of Puerto Rico
in the afternoon. So far, rainfall accumulations are expected to
remain below an inch, posing no risk of flooding. However, with
increasing available moisture and eastward shift of the mid-level
ridge, conditions are expected to become favorable for showers
with isolated thunderstorm development from Thursday evening
onwards. Thus, there is a chance for increasing flooding risks,
particularly across southern and eastern Puerto Rico and the U.S.
Virgin Islands. Typical seasonal temperature variations are
expected during the period, with lows ranging from the mid 60s
across higher elevations and highs to around 90 degrees across
lower elevations and urban areas.

&&

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

Deep moisture in the southeastern Caribbean extending into the
western tropical Atlantic and the likely development of a tropical
cyclone in the western Caribbean between Jamaica and Panama will
contribute to excessive moisture and precipitable water values
between 2.0 and 2.5 inches the entire period. The GFS suggests
that greatest moisture will be Sunday morning.

The tropical cyclone is currently modeled to cross over Haiti on
Saturday afternoon which will pull low level winds directly from
the south by Saturday night. This will pull moisture out of the
southeastern Caribbean over the area and over a frontal boundary
that will cause considerable convergence over the area over the
weekend. This band will continue to be active over the area Monday
and Tuesday with both Puerto Rico and the U.S. Virgin Islands
seeing significant rainfall continuing through the period. Local
amounts for these 5 days could be as great as 8 inches in Puerto
Rico and 4 inches in the U.S. Virgin Islands. The risk of flooding
will increase considerably as well as the threat of landslides
beginning on Friday.

Upper level conditions are dominated by high pressure and this
will suppress anything greater than isolated thunderstorms
development, but thunderstorms are expected Friday through Sunday
at a minimum. Temperatures in the southerly flow are also likely
to push north coast temperatures above normal and some areas will
likely exceed 90 degrees over the weekend until showers cool the
area.

&&

.AVIATION...
(06Z TAFS)
Issued at 425 AM AST Tue Nov 14 2023

Passing SHRA could result in brief MVFR conditions
across USVI terminals through 14/14Z and TJSJ after 14/22Z. For
TJBQ, afternoon SHRA/TSRA could also result in MVFR conditions
between 14/16-22Z. Light to calm and variable winds below 8 knots,
increasing to 10-15 knots with higher gusts and sea breeze
variations between 14/14-22Z. Winds will become light to calm and
variable again after 14/22Z. Maximum winds NW 23-28 kt btwn
FL415-455.

&&

.MARINE...
Issued at 425 AM AST Tue Nov 14 2023

Generally choppy seas are expected over the local waters during
the near term, however by Thursday night small craft advisory
conditions are likely to begin in the outer Atlantic waters. Winds
and seas are expected to increase everywhere as the tropical
cyclone moves west of the area. At this time peak conditions are
expected Friday night and Saturday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
445 AM AST Wed Nov 15 2023

.SYNOPSIS...
Issued at 333 AM AST Wed Nov 15 2023

Low pressure in the western Caribbean shows signs of slow
development through Friday. The system will move northeast across
Haiti on Saturday and pull moisture out of the south and
southeast across the area Thursday night and over the weekend.
This moisture is expected to remain in the area through mid week
next week and may begin provoking flooding and mudslides over the
weekend. Meanwhile east southeast flow of modestly moist low-
level air will bring scattered showers to Puerto Rico and the U.S.
Virgin Islands today and tomorrow, but only modest accumulations
are expected in favored areas.

&&

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

Today's primary hazards revolve around localized excessive
rainfall, lightning, winds, and excessive heat risks at limited
threat levels. Hazard risks associated with flooding and lightning
will likely increase by Thursday.

An analysis of overnight radar and satellite imagery indicated that
portions of eastern Puerto Rico experienced more frequent showers,
with less frequent showers impacting Vieques, Culebra, and the US
Virgin Islands. Since 8 PM AST, radar-estimated preliminary rainfall
totals indicated up to an inch of rain over coastal municipalities
of eastern Puerto Rico. Overnight temperatures varied across the
region, ranging from around 65 degrees in higher elevations to about
79 degrees across eastern Puerto Rico and the local islands. Winds
were generally light and variable.

There is still a high likelihood of transitioning from drier and
stable conditions to wetter and unsettled weather conditions in the
next day or so. This transition is expected due to the proximity of
a broad trough of low pressure and associated surface-induced
features, which the National Hurricane Center is closely monitoring
for potential cyclonic formation. As this feature spreads into the
central Caribbean, it will steer a mid-level ridge eastward, causing
a gradual weakening of the trade wind cap inversion that has
maintained stability aloft since early in the week. Meanwhile,
easterly winds, generated by a surface high pressure to the north
over the western Atlantic, will be replaced by the surface flow
generated by the surface-induced low. Winds are forecast to
gradually veer from the east-southeast on Thursday and from the
south-southeast on Friday. Even with intermittent patches of shallow
moisture moving through the area, the prevailing dry air will
maintain normal to below-normal moisture levels through Thursday
morning, with precipitable water values below 1.75 inches.
Nevertheless, a significant increase in moisture is likely from
Thursday evening onward, causing precipitable water values to rise
rapidly and stabilize around 2.0-2.3 inches thereafter.

For today into late Thursday morning, expect predominantly fair
weather conditions, with extended periods of clear skies and limited
shower activity. Trade wind passing showers will likely impact
eastern Puerto Rico and the U.S. Virgin Islands overnight and early
morning, generating minimal rainfall accumulations. The development
of localized showers with an isolated thunderstorm is likely over
the far western sections of Puerto Rico in the afternoon, where
ponding of water on roadways and poorly drained areas is likely.

Conditions are forecasted to become more favorable for deep
convective development from Thursday afternoon onward. The expected
moderate to heavy rains will likely increase the risk of urban and
small stream flooding, particularly across southern Puerto Rico.
Typical seasonal temperature variations are expected today, ranging
from mid 60s in higher elevations to around 90 degrees in lower
elevations. Slightly higher temperatures, including areas with
elevated excessive heat risks, are possible on Thursday and Friday
as winds shift to a more southerly direction.

&&

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

Moisture from a potential tropical cyclone moving northeast toward
Haiti and moisture moving out of the western tropical Atlantic and
the southern Caribbean and Venezuela will converge over the local
area and form a persistent band of moisture Friday night that
persists through the period. At the same time high pressure aloft
will suppress the majority of the convective activity. This will
bring a steady flow of moisture that will primarily affect the
windward slopes of all land areas with some carryover to the other
sides each day. Total precipitable water will peak on Saturday
and again on Sunday between 2 and 2.5 inches. The GFS has been
backing off on the strength of the tropical cyclone it is
forecasting and the hurricane center now only assigns it a 50
percent chance of development over the next 7 days. Therefore have
backed off the amount of rain expected during the period, but may
still see over 6 inches in eastern Puerto Rico.

Winds remain southerly for the weekend but begin to weaken and
then shift to northeast on Tuesday. This will shift the focus of
the rainfall to the north coast next week, when much of the
moisture in the tropical system, likely trapped by a cold front
north of the area will persist beyond the middle of next week.

This system still has the potential to develop moderate to heavy
rains of long duration that could generate flooding and mudslides
over Puerto Rico and the U.S. Virgin Islands.

&&

.AVIATION...
(06Z TAFS)
Issued at 333 AM AST Wed Nov 15 2023

Passing SHRA could result in brief MVFR conditions
across TJSJ and USVI terminals through 15/14Z and after 15/22Z. For
TJBQ, afternoon SHRA could also result in MVFR conditions between
15/17-22Z. Light to calm and variable winds below 8 knots will
increase to 14-18 knots with higher gusts and sea breeze
variations between 15/14-22Z. Winds will become light to calm and
variable again after 15/22Z.

&&

.MARINE...
Issued at 333 AM AST Wed Nov 15 2023

Seas from a low pressure in the central Atlantic ocean will begin
to arrive on Thursday and should reach maximum height on Saturday.
Nevertheless, seas of 7 feet or more will persist in the open
waters and passages through at least Sunday night. Winds greater
than 20 knots are locally possible during the next 7 days but may
exceed 25 knots in the Mona passage over the weekend. High rip
current risk for the exposed northern coasts will begin on
Thursday night and there is a potential for high surf by Saturday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
525 AM AST Thu Nov 16 2023

.SYNOPSIS...Expect generally fair weather conditions today.
However, a transition towards wetter and unsettled weather
conditions is likely by Friday into the weekend, closely linked to
a broad area of low pressure currently monitored by the National
Hurricane Center for potential tropical cyclone development over
the southwestern Caribbean Sea. Increasing winds and northerly
swells will also cause deteriorating marine and surf zone
conditions starting today, with Small Craft Advisories and Rip
Current Statement already in effect.


&&

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

Calm weather conditions prevailed overnight, with the easterlies
pushing some showers across the windward sections of Puerto Rico and
the U.S. Virgin Islands. Rainfall amounts were minimal. Overnight
low temperatures were around the 60s across mountains and valleys
and in the low 70s along the coast.

Today will be the driest day of the short term due to the influence
of the remnants of a frontal boundary to the north and an area of
interest for NHC across the Western Caribbean. However, the easterly
winds will bring occasional quick passing showers. Most of the
activity must fall over the eastern sections of PR, but some
training will remain possible across the interior and northwestern
areas of Puerto Rico during the afternoon. Although we are currently
in mid-November, the combination of maximum air temperature and the
available moisture will result in heat index values up to 107
degrees Fahrenheit across the urban and coastal sections of Culebra,
Vieques, and North-Central PR.

Winds will slowly shift from the southeast on Friday and more
southerly on Saturday as the two areas actively monitored by NHC
move north to northeast from the Southwestern Caribbean and south of
Florida. These systems will slowly pull abundant moisture near
Puerto Rico and the U.S. Virgin Islands from Friday onward. Based on
the latest model guidance, Saturday will be the wettest day of the
short term. Islanders should prepare for another wet and unstable
period from Friday onward. Please monitor the weather conditions as
frequent lightning, urban and small stream flooding, and strong
winds may evolve during the period.

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

According to the most recent model guidance, wet and unsettled
weather is expected to continue through the weekend and most of
the workweek, maintaining a heightened risk of excessive rainfall.
This weather pattern originates from moisture convergence from a
potential tropical cyclone moving northeast over the Greater
Antilles to the west and the Intertropical Convergence Zone to the
south. This area of persistent moisture convergence will
gradually move east-northeastward into the northeastern Caribbean,
lingering through early next week. By Sunday, this continuous
influx of abundant tropical moisture under southerly steering
winds will likely bring precipitable water vapor past two standard
deviations above normal moisture levels, ranging between 2.4 and
2.6 inches. Although some moisture erosion is possible early in
the workweek, precipitable water values will remain between one
and two standard deviations, or 2.0-2.2 inches, through late
Monday night.

From Tuesday onward, the proximity of a dissipating frontal
boundary to the north will lead to weakening winds and a shift to
more northeasterly directions. While this transition and the entrance
of a drier air patch may cause further moisture erosion, bringing
levels close to or below normal thresholds, remnants of the
frontal boundary and lingering moisture from the previous event
will likely bring moisture levels back to typical thresholds by
Thursday.

The areas prone to flooding impacts, ranging from urban and small
stream flooding to localized flash floods and mudslides, are
forecast to shift from southern Puerto Rico early in the period to
northern Puerto Rico by midweek, while the risk will persist for
eastern Puerto Rico, Vieques, Culebra, and the U.S. Virgin Islands
throughout the period.


&&

.AVIATION...Expect VFR conditions today. Trade wind showers will
sometimes brush local terminals, and some +SHRA may develop during
the afternoon, mainly across E-PR and downwind from the USVI
between 16/18-22z. Winds will prevail, especially from the E-ESE
at 5 to 15 kt, but with higher gusts and sea breeze variations
after 16/13z.


&&

.MARINE...Recent observations from the CariCOOS buoy network in
the vicinity of Puerto Rico and the U.S. Virgin Islands have shown
consistent marine conditions with wave heights ranging from 3 to
4 feet.

The marine conditions are expected to deteriorate as increasing
winds and northerly swells impact the regional waters beginning
today and tonight. Seas are anticipated to reach up to 6 feet,
with occasional seas up to 8 feet today, building up to 7 feet
tonight, and increasing further to 8-10 feet from Friday onward.
Therefore, Small Craft Advisories are in effect for offshore and
near-shore Atlantic waters and local passages. The first advisory
will commence this evening for offshore Atlantic waters.

These conditions will also impact surf zone conditions, leading to
breaking waves of up to 7 feet today and higher on Saturday. A Rip
Current Statement has been issued for most north-facing beaches of
Puerto Rico, spanning from Arecibo eastward to Fajardo, including
Culebra. These conditions are not only expected to expand to most
north- and east-facing local beaches but are also anticipated to
worsen during the weekend, potentially meeting High Surf Advisory
criteria.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
549 AM AST Fri Nov 17 2023

.SYNOPSIS...A transition towards wetter and unsettled weather
conditions is expected today into early next week, closely linked
to Potential Tropical Cyclone Twenty-Two, as it crosses the
Greater Antilles to the west and rushes northeastward across the
western Atlantic. Increasing winds and northerly swells will
continue to deteriorate marine and surf zone conditions, with
Small Craft Advisories, High Surf Advisories, and a Rip Current
Statement in effect through the weekend. Residents and visitors
are advised to avoid life-threatening beach conditions and remain
alert to flood-related impacts.


&&

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

We observed another calm night but under an east-southeast wind
flow. A line of clouds moved across the east and southern portions
of Puerto Rico, resulting in a few showers, while the Virgin Islands
did not observe any rain earlier this morning. Overnight low
temperatures were around the 60s across mountains and valleys and in
the low 70s along the coast.

IR-GOES-East channel detected a band of clouds approaching the
islands from the Caribbean Sea. GOES-E Total Precipitable Water
indicated above-normal values, ranging between 2.0 and 2.30 inches.
The chance of rain activity will slowly increase across the islands
throughout the day, especially in the afternoon and evening, when
the risk of flooding will increase, especially for the windward
sections of southern and eastern PR and St Thomas.

Although model guidance backs down the rainfall accumulations from
previous runs, the unsettled weather pattern will likely develop on
Saturday and Sunday. This possible change is associated with the
forecast track of Potential Tropical Cyclone Twenty-Two, which the
National Hurricane Center monitors (and does not represent a direct
threat to PR/USVI's area). Winds will continue from the east-
southeast today, becoming more southeasterly on Saturday and
southerly by Sunday as Potential Tropical Cyclone Twenty-Two moves
northeast from the Southwestern Caribbean into the Atlantic. Based
on the forecast trajectory, rainfall amounts may be 2 to 4 inches,
with isolated higher amounts from today into the weekend, especially
along the southern slopes in PR. Please monitor the weather
conditions as frequent lightning, urban and small stream flooding,
and strong winds may evolve during the period.

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

Despite a west-northwestward shift and a delayed arrival of the
area of low-level convergence and high moisture associated with
Potential Tropical Cyclone Twenty-Two, the likelihood of continued
wet and unsettled weather early next week remains, thereby
maintaining an elevated risk of excessive rainfall. Consistent
with previous model guidance, a reduction in the available
moisture is anticipated over the forecast period. Nevertheless, an
extended period of abundant tropical moisture influx is expected,
driven by Tropical Cyclone Twenty-Two and the remnants of an old
frontal boundary. This prolonged influence should maintain
precipitable water values between one and two standard deviations
above seasonal norms, ranging from 2.0 to 2.2 inches, persisting
through late Tuesday night into Wednesday morning. A gradual
decline in available moisture is expected later in the workweek,
with precipitable water values potentially dropping below seasonal
normal thresholds (below 1.5 inches) by Friday due to the
entrance of drier air patches.

Tropical Cyclone Twenty-Two is expected to induce south-
southwesterly winds on Monday. However, the proximity of a
dissipating frontal boundary to the north will result in light and
variable winds on Tuesday, briefly transitioning to more
northeasterly winds on Wednesday. Subsequently, a surface high
pressure over the western Atlantic will bring east-to-southeast
winds. Following this shift in wind patterns, areas prone to
flooding impacts will transition from southern Puerto Rico on
Monday to northern and eastern Puerto Rico by midweek. Meanwhile,
Vieques, Culebra, and the U.S. Virgin Islands will remain under a
limited risk of excessive rainfall. A decrease in precipitable
water levels should lower the likelihood of precipitation and,
consequently, diminish the risk of flooding by the end of the
workweek.


&&

.AVIATION...Expect VFR conditions today, but with SHRA/TSRA
increasing from late this morning onward. A line of clouds
approaching from the Caribbean may bring SHRA/TSRA between
17/10-14 and may result in MVFR or brief IFR conditions across
JPS/ISX. Winds will prevail, especially from the ESE at 5 to 15
kt, but with higher gusts and sea breeze variations after 17/13z.


&&

.MARINE...Recent observations from the CariCOOS buoy network near
Puerto Rico and the U.S. Virgin Islands have shown consistent
marine conditions with wave heights ranging from 3.5 to 5.5 feet.

The marine conditions will continue to deteriorate as increasing
winds and northerly swells impact the regional waters through the
weekend. Seas are anticipated to reach up to 7 feet, with
occasional seas up to 9 feet today, building up to 10 feet from
tonight onward. Therefore, Small Craft Advisories are in place for
most local waters, except for the coastal waters of eastern,
southern, and southwestern Puerto Rico, northern Vieques, and
south of the northern U.S. Virgin Islands, where small craft are
still urged to exercise caution.

These conditions will also impact surf zone conditions, with
breaking waves of 6-7 feet today, increasing to 7-11 feet on
Saturday and continuing into the weekend. A Rip Current Statement
has been issued for most north-facing beaches of Puerto Rico,
spanning from Aguadilla eastward to Fajardo, including Culebra.
These conditions will not only affect the shores of western Puerto
Rico, Vieques, and the U.S. Virgin Islands tonight into Saturday
but will intensify across northern Puerto Rico and Culebra, where
a High Surf Advisory is now in place starting Saturday morning.

For details on current marine and surf zone risks, refer to the
Coastal Hazard Message and Marine Weather Message.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
414 AM AST Sat Nov 18 2023


.SYNOPSIS...

A wetter pattern is still forecast over the weekend, however a
mid to upper-level ridge across the eastern Caribbean will help
stabilize conditions. A further increase of rainfall is forecast
for early next week. The strong north-northeasterly swell will
maintain hazardous marine and coastal conditions through the
weekend with seas up to 8 feet across the local waters and
breaking waves up to 11 feet for northern coastlines. Exercise
caution when spending time across effected areas.

&&

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

Overall the columnar moisture continued to increase and spread
across the region steered by the anticyclonic flow aloft and the
moist southeast to south low level wind flow. Increasing low level
convergence and good moisture pooling during the rest of the weekend
into Monday will increase the chance for shower and isolated
thunderstorm development across Puerto Rico and portions of the U.S.
Virgin islands but especially on Sunday and through Monday.

Showers steered by the moderate to strong southeasterly wind flow
continued to develop across the Caribbean waters and passages and
move inland across portions of the south and southeast coastal
municipalities of Puerto Rico, and mainly in the vicinity of St
Croix from time to time. Expect this pattern to continue into the
morning hours with mostly light to moderate showers affecting these
areas from time to time. For the rest of the day and overnight
expect late afternoon and evening convection to be focused over the
southwest to southeast coastal areas, and southern slopes of PR with
lesser activity in and around the USVI.

By Sunday and Monday, expect increasing moisture convergence and
instability aloft due to the passage of a polar trough just north of
the region. Remnant moisture from the broad area of low pressure
which was formerly tropical Cyclone Twenty Two is so far forecast to
be lifted up across the region, where it will merge with an old
frontal boundary/shearline, then linger across the region through
Monday. Meanwhile the southerly wind flow is to diminish in response
to a surface high pressure ridge, which will build across the
southwest Atlantic. So far the wettest period still looks like later
this evening and overnight through Sunday. Consequently, a limited
to elevated flooding risk will persist through the weekend as there
exists the potential for urban and small stream flooding along with
ponding of waters roadways and in poor drainage areas. The strongest
showers and thunderstorms are expected during the late afternoon,
overnight and early morning hours. Therefore localized flash
flooding and mudslides in steep terrain cannot be ruled out. For the
rest of the period, this activity is expected to affect mainly
portions of the west, south and southeast sections of PR, but some
afternoon convection cannot be ruled out along portions of the north
coastal areas, including the San Juan metro. At least through Sunday
only isolated to scattered shower activity is forecast for the USVI
but chances for showers and thunderstorm development development
increases by Monday.

Additionally, although cloudy skies will persist , the moist
southerly flow will create hot an humid conditions resulting in
limited to elevated maximum heat indices between 100-108 degrees
heat indices during the rest of the weekend.

&&

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

The inherited forecast remains unchanged. The latest model guidance
continues to show high moisture content across Puerto Rico and
the U.S. Virgin Islands associated with a broad trough of low
pressure (previously called Potential Tropical Cyclone Twenty-Two)
and the remnants of an old frontal boundary. Therefore, continued
wet and unsettled weather conditions are likely through at least
Tuesday. Models suggest a precipitable water content of around
2.00 to 2.30 inches. The proximity of a dissipating frontal
boundary to the north will result in light and variable winds on
Tuesday, briefly transitioning to more northeasterly winds on
Wednesday. Subsequently, high surface pressure over the western
Atlantic will bring east-to-southeast winds later in the workweek
into the weekend. At this time, mid-week looks like the transition
day into a gradual drying pattern. As mentioned in previous
discussions, a gradual decline in available moisture is expected
after Wednesday, with precipitable water values potentially
dropping below seasonal normal thresholds (below 1.5 inches) by
Friday due to the anticipated patches of dry air. The decrease in
precipitable water levels should lower the likelihood of
precipitation and diminish the risk of flooding by the end of the
workweek into the weekend.

Overall, during the long-term period, expect to see a transition
from a wet/unstable weather pattern to a slightly dry/stable
pattern with the typical seasonal weather conditions of morning
trade wind showers across eastern Puerto Rico and the U.S. Virgin
Islands and the common afternoon convection across western PR due
to diurnal heating and sea breeze variations.

&&

.AVIATION...VFR durg prd, except VCSH TJPS fm 18/06-14Z TEMPO 4SM SHRA
til 08/12Z in moist srly flow w/ocnl CIG nr FL025.Sfc wnd fm SE
5-12 kts til 18/14Z,incr to 14-18kt thru 18/22Z with ocnl hir
gusts. SCT-BKN lyrs nr FL025...FL050... FL120 en route btw
islands. BKN-OVC nr FL250 W of PR and ovr Mona passage. SHRA/Isold
TSRA fcst ovr Mona Passage aft 18/14z mov SSW vcty TJBQ/TJMZ.
L/lvl wnds fm SE winds btw 15-22 kts blo FL120...then veering and
incr w/ht with Max Wnd WNW 30-40 kts btwn FL400-450.

&&

.MARINE...Latest buoys from the CARICOOS network shows seas
ranging around 5-10 feet across the local waters and passages as
the long- period northerly swell continues to make its way into
the our forecast area with periods around 13-15 sec. From these
observations, 10-foot breakers were estimated for the Rincon and
Arecibo buoys.

For details on current marine and surf zone risks, refer to the
Coastal Hazard Message and Marine Weather Message.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
453 AM AST Sun Nov 19 2023


.SYNOPSIS...

Expect dry and stable conditions to prevail across the islands
today. This pattern should continue through at least Monday when
better moisture approaches from the west, which may increase
rainfall the following days. Hazardous marine conditions will
continue due to a strong north- northeasterly swell and moderate
to locally fresh south wind. Seas and breaking waves are reaching
around 10 feet due to this, therefore exercise caution when
spending time around the ocean.

&&

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

Conditions will remain dry and stable over most of the region today
as most of the remnants from the large plume of moisture associated
with the former tropical disturbance are now expected to stay to the
west of the region and over the Dominican Republic. However mid to
upper level cloud debris will continue to spill across the region
steered by the upper level west to southwest wind flow. Southerly
low level winds will persist across the region with the continued
intrusion of drier air from the south and east along with suspended
dust particulates steered by south to southeast low level winds.
Good mid to upper level compression and the presence of Saharan dust
particulates trapped in the low levels will promote warmer than
normal conditions which will persist overnight, and consequently all
official stations at San Juan, and USVI airports have reported the
warmest minimum temperatures on record for yesterday.

Presently,The Doppler Radar and satellite imagery showed the
aforementioned line of showers and thunderstorms west of Puerto
Rico,lingering over the Dominican Republic and Mona passages and being
steered by the prevailing southerly low level wind flow. Recent
guidance now suggest that this plume will be slowly lifted mainly
northwards between the Dominican Republic and the Mona passage
overnight through Sunday, with only fragmented moisture expected to
eventually reach portions of western Puerto Rico later today.

For the rest of the day and into Monday, overall dry conditions will
prevail across the most of the islands as model guidance suggests
that the mid to upper leve ridge and continued intrusion of Saharan
dust particulates, will maintain the area on the dry and subsident
side of the upper trough which is forecast to quickly move north of
the region today through Monday. A southerly low level wind flow
will persist through Monday, then by late Monday though Tuesday
winds, are to shift and become more northerly as a high pressure
ridge will build across the southwest Atlantic. This in turn will
bring return remnant moisture from the north and west, associated
with the aforementioned moisture plume as well as that from a
frontal shearline that will sink southwards across the area. As a
result, increasing low level moisture is forecast by Monday
afternoon into Tuesday with this time frame now expected to be the
best potential for shower and isolated thunderstorm development
across the islands and coastal waters. At this time widespread
rainfall is now anticipated, however there will be increased chance
for excessive rainfall in isolated areas and thus potential for
urban and small stream flooding along with ponding of water on roads
and poor drainage areas especially on Tuesday. Stay tuned!

&&

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

No significant changes were introduced to the long-term forecast.
The latest model guidance suggests Wednesday as a transition day
from a wet/unstable pattern to gradual drying and stable weather
conditions. By mid-week, expect the wind flow to gradually turn
northeasterly due to the proximity of a dissipating frontal
boundary to the north of the forecast area. On Thursday, the
surface high-pressure system over the western Atlantic will
position across the central Atlantic, promoting east-to-southeast
winds through the weekend. As mentioned, a gradual decline in
available moisture is expected after Wednesday, with precipitable
water values dropping below seasonal normal thresholds (below 1.5
inches) as additional patches of dry air filter across Puerto Rico
and the U.S. Virgin Islands. The decrease in precipitable water
levels should lower the likelihood of precipitation and diminish
the risk of flooding by Friday into the weekend.

In general, during this period, expect mostly calm and stable
weather conditions across the islands. However, occasional trade
wind showers in the morning across eastern Puerto Rico and the
U.S. Virgin Islands and the typical afternoon convection across
western PR due to diurnal heating and sea breeze variations cannot
be ruled out.

&&

.AVIATION...VFR conditions will persist through the prd. Hazy
skies will persist due to suspended Saharan dust particulates
across the region, but no restriction to flight VIS is
anticipated. A line of showers may impact The Mona passage between
western PR and the Dominican Republic with SHRA/Isold TSRA psbl
btw 19/06-10z. SFC wnd mainly fm S at 10 kt or less, increasing
between 10-20 kts aft 19/14z. Isold SHRA/TSRA may develop ovr
regional waters of the ATL and coastal waters west of Puerto Rico
durg aftn.

&&

.MARINE...Latest buoys from the CARICOOS network shows seas
ranging around 4-7 feet across the local waters and passages as
a north-northeast swell continues to make its way into the our
forecast area with periods around 12 and 14 sec. Hazardous marine
conditions remain across the Atlantic Ocean and Caribbean
Passages.Therefore, Small Craft Advisories continue in effect for most
local waters.