Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
423 AM AST Sat Oct 15 2022

.SYNOPSIS...

Increasing activity is expected into the start of next week, as a
deep-layer polar trough affects the region, increasing
instability. Then, decreasing moisture and instability is expected
starting around Tuesday, and decreasing shower activity will be
seen into the end of the week next week.

&&

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

The available moisture is gradually increasing, and is expected to
continue increasing through the day. This increase in moisture is
causing scattered showers to be observed across the local waters,
some of the brief showers could affect the USVI and eastern PR in
the morning hours early in the morning. However, in the afternoon
hours, the available moisture is expected to combine with the local
effects and diurnal heating to cause showers and thunderstorms to
develop. The central to western sections of PR as well as portions
of the San Juan Metro have the best chance of showers, some of which
could be heavy at times. This activity could cause urban and small
stream flooding. Elsewhere, isolated to scattered showers are
forecast, and some ponding of water in areas of poor drainage could
be observed in isolated spots.

For Sunday, there is the potential for more persistent thunderstorms
over PR, due to an approaching upper trough from the northwest,
causing an increase in instability over the local area. This is in
addition to the near to slightly above normal moisture with
precipitable water values reaching 1.9 inches by Sunday afternoon.
That said, the upper trough would be in an even better position for
thunderstorm development on Monday. Therefore, showers and
thunderstorms are also forecast over PR on Monday afternoon, while
scattered showers are forecast elsewhere. The coverage area of
thunderstorms on Monday may be limited simply because the winds are
very light, so the thunderstorms that due develop in areas of
convergence over PR will move very slowly, and other thunderstorms
may develop with convergence of the outflow boundaries of other
thunderstorms as the afternoon progresses. This pattern generally
causes at least urban and small stream flooding, but some isolated
flash flooding should not be ruled out.

As far as temperatures, daytime high temperatures will be near
normal, with highs in the upper 80s to low 90s across the lower
elevations. The heat index values will continue reaching or
surpassing the 100s degrees Fahrenheit during short term period,
especially across north central Puerto Rico.

&&

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

The affects of the polar trough will linger over the region into
Tuesday, resulting in lingering instability. This will help to
sustain shower activity. However, moisture will decrease over the
area Tuesday through at least late Thursday. And instability will
decrease through the period. As such, a decrease in shower activity
is expected. Still, a typical shower pattern will be maintained, if
inhibited. The weak steering flow will result in slow-moving
showers. Convection that reaches into the mid-levels could also be
affected by westerly to northwesterly flow, as well. Streamer
development is less likely due to the light winds.

&&

.AVIATION...
(06Z TAFS)

VFR conditions will prevail. VCSH expected across the local
terminals in the morning hours. VCTS is expected at TJBQ after
15/17Z. TJSJ may have VCTS/VCSH at some point between 15/17 and
15/20Z, as SCT SHRA/ with possibly TSRA develops south and west of
the terminal. Winds will be generally easterly at around 10KT with
sea breeze variations developing after 15/13Z.

&&

.MARINE...

Winds of up to around 10 to 15 knots will continue across the local
waters. Seas will remain generally 4 feet or less for the offshore
Atlantic waters, and 3 feet or less across the rest of the waters.
There is a low risk of rip currents.


&&

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

$$

SHORT TERM...JA
LONG TERM....CRS
AVIATION...JA

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
433 AM AST Sun Oct 16 2022


.SYNOPSIS...

Near-normal moisture and increased instability will result in an
active afternoon today and tomorrow, with the typical shower
activity increasing through this time. Showers and thunderstorms are
expected for western and interior portions of Puerto Rico,
especially. A light steering flow will result in slow-moving
showers, which could lead to locally high rainfall totals,
increasing the potential for flooding conditions to develop.
Decreasing moisture and stability are expected for Tuesday into the
end of the week.

&&

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

The available moisture is expected to remain fairly steady today and
tomorrow, with precipitable water near 1.8 inches but perhaps
peaking to 1.9 inches on Monday. Then, a slight decrease to around
1.7 inches is forecast. We also have a diffluent pattern in the
upper levels and an upper trough moving in from the NW, which will
cause an increase in instability by this afternoon and through
Monday. The slightly above normal moisture is causing widely
scattered showers across the local waters in the early morning
hours, some of which also affected portions of eastern PR and will
continue for the rest of the day. Brief showers could also affect
the USVI, though none have so far tonight. In the afternoon hours,
the available moisture is expected to combine with the local effects
and diurnal heating to cause showers and thunderstorms to develop.
The central to western sections of PR as well as portions of the San
Juan Metro have the best chance of showers, with central to western
Puerto Rico having more persistent and longer lasting showers and
thunderstorms. This activity, combined with the shower activity
observed in the past few days, will likely cause some could cause
urban and small stream flooding, while isolated flash flooding will
not be ruled out. Elsewhere in PR, scattered showers with isolated
thunderstorms are forecast, and some ponding of water in areas of
poor drainage could be observed. Across the USVI, mainly scattered
showers could be observed, as well as lines of showers streaming off
the islands.

For Monday, there is the potential for another round of persistent
thunderstorms over PR, due the approaching upper trough from the
northwest, which will be in a favorable position to cause
instability over the area. This is in addition to the above normal
moisture with precipitable water values reaching 1.9 inches.
Therefore, showers and thunderstorms are forecast over PR on Monday
afternoon, while scattered showers are forecast elsewhere in the
local area. The thunderstorms on Monday may persist over any one
area simply because the winds are very light, so the thunderstorms
that due develop in areas of convergence over PR will move very
slowly. This pattern will once again cause at least urban and small
stream flooding, but some isolated flash flooding should not be
ruled out. By Tuesday, the moisture decreases slightly and the upper
trough continues moving to the SE, with the local islands being in
the subsident side of the trough by Tuesday afternoon. This will
limit shower and thunderstorm development to locally induced
thunderstorms over PR, which will be once again across the central
to western sections of PR, while isolated to scattered showers are
forecast elsewhere.

As far as temperatures, daytime high temperatures will be near
normal, with highs in the upper 80s to low 90s across the lower
elevations. The heat index values will continue reaching or
surpassing the 100s degrees Fahrenheit during short term period,
especially across north central Puerto Rico.

&&

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

Ridging is expected in the mid- to upper-levels, maintaining
stability over the region through at least the end of the workweek.
Meanwhile, drier than typical air will be over the area into Friday,
as well, though patches of near-normal (on the low end of the normal
range) moisture are likely to pass through the region from time to
time. Still, local effects will combine with available moisture to
result in showers and isolated thunderstorms in a typical pattern
over the region. Forecast confidence is medium, largely due to
uncertainties in the direction of a slow steering flow and the
timing of moisture patches.

Forecast certainty decreases at the end of the week. Both the Euro
and GFS suggest that an upper-level low will approach from the
northeast, absorbing the upper-level low that will have been
effectively stationary east of the Windward Islands over the
previous days. This trough will then affect the region, resulting in
an increase in shower activity. However, there is disagreement on
timing, and just how close the low will get to the area. As such,
there is the potential for active weather next weekend, but it is
essentially equally likely that there will be seasonally-typical
conditions. Forecast confidence becomes low by late Friday/early
Sunday.

&&

.AVIATION...
(06Z TAFS)

VFR conditions will prevail. VCSH expected across the local
terminals in the morning hours. VCTS is expected at TJBQ after
16/16Z. TJSJ may have VCTS/VCSH at some point between 16/16 and
16/20Z, as SHRA/TSRA develops mainly south of the terminal, but
considering uncertainty, TEMPO TSRA is possible both at TJSJ and
TJBQ. Winds will be generally easterly to northeasterly, though ESE
at TIST, at around 10KT with sea breeze variations developing after
16/13Z.

&&

.MARINE...

Winds of up to around 10 to 15 knots will continue across the local
waters. Seas will remain generally 4 feet or less for the offshore
Atlantic waters, and 3 feet or less across the rest of the waters.
There is a low risk of rip currents.

&&

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

$$

SHORT TERM...JA
LONG TERM....CRS
AVIATION...JA

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
417 AM AST Mon Oct 17 2022

.SYNOPSIS....A seasonal weather pattern will prevail today, with
showers favoring windward sections in the morning and the interior
to western areas in the afternoon. Near-normal moisture levels,
instability, and a weak steering flow will induce excessive rain
from slow-moving showers with thunderstorms this afternoon,
increasing the potential for urban and small-stream flooding.
Isolated flash flooding is possible. Other hazard risks include
lightning and excessive heat. Although there is low confidence
concerning mid-to-upper dominant features by the end of the
workweek into the weekend, similar weather conditions will
persist.

&&

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

Today through Tuesday, unstable conditions are expected aloft as
a short wave polar trough will sink southeastward across the
region, followed by a Tutt low developing just northeast of the
northern Leeward Islands by early Wednesday. Thereafter upper
level ridge will build across the region once again. The
combination of a stalled frontal boundary and an induced surface
trough just north and west of the region, along with a weak
tropical wave now crossing the eastern Caribbean, will all
maintain sufficient low level moisture convergence today through
early Tuesday. This overall pattern will result in a fairly moist
and active weather pattern particularly across Puerto Rico today
into early Tuesday. Lesser activity is expected for the U.S.
Virgin Islands but afternoon showers with a chance of isolated
thunderstorms during the late afternoon hours and overnight into
Tuesday morning cannot be ruled out.

For today as previously mentioned active and unstable conditions,
due to the proximity of the polar trough northwest and good low
level moisture convergence and daytime heating. Cooler mid level
temperatures and light low level winds will also aid in enhancing
the afternoon convection over Puerto Rico which will lead to strong
thunderstorms activity and periods of heavy rains especially over
parts of the interior and west sections of Puerto Rico. The
heaviest activity is forecast to develop across the central interior
then eventually drift west and southwest towards the surrounding
municipalities. This expected periods of enhanced afternoon
activity and heavy rains will again lead to ponding of water in
roadways and in poor drainage areas, as well as minor flooding in
urban areas. The heavy rains and associated excessive runoff may
also lead to sudden water surges along local rivers and streams
especially those that have recently had heavy rainfall from previous
days. By Tuesday, similar pattern is expected but across portions of
the interior and west to northwest sections of Puerto Rico, as
winds are to become more southeasterly while the polar trough shift
farther eastward. Consequently, the associated frontal boundary is
forecast to weaken and move farther into the west central Atlantic
and will be replaced by a building surface high pressure over the
central Atlantic. Given the expected wind pattern the shower
activity should then be focused over the northwestern quadrant
including the San Juan Metro area. Therefore, the potential for
urban flooding and ponding of water on roads and poor drainage areas
will be likely in those areas.

On Wednesday, weather conditions are expected to gradually improve,
as the upper trough is forecast to weaken and lift northwards and
will be replace by a high pressure ridge and more stable condition
aloft. In addition the surface Atlantic high pressure ridge will
again build north and east of the region bringing a return of more
easterly winds and a more seasonal weather pattern.

Daytime temperatures are forecast to remain near normal for today
but slightly warmer on Tuesday and Wednesday due to the expected
southeasterly low level wind component. Maximum heat indices may
between 102 to 105 degrees across portions of the northwest and
north central areas of Puerto Rico.

&&

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

A seasonal weather pattern, characterized by overnight/early
morning showers moving over windward areas and afternoon
convective development steered by sea breeze convergence and
diurnal heating across the interior and western sections, will
prevail during the cycle despite variations in key synoptic
features' location and timing influencing the local weather
conditions. Guidance from main global models suggests an upper-
level low lingering over the northeastern Caribbean through the
end of the workweek before slowly drifting to the northeast and
being absorbed by yet another upper-level low propagating
southwestward through the weekend. Between these features and a
robust polar trough moving off the eastern coast of the United
States, ridging will hold, stretching southward into the Caribean
region. Discrepancies, and thus, lower confidence levels, emerge
from the location and westward extension of these lows concerning
the northeastern Caribbean. While the GFS suggests that these
troughs will remain well to the east with ridging holding over the
area, the ECMWC presents much closer proximity with favorable
conditions for deep convective development.

Despite this, model-estimated total precipitable water values
will generally remain at normal seasonal levels, briefly falling
to below-normal values by the end of the workweek with the
entrance of a somewhat drier air mass. Any surface-induced feature
generated by the upper-level lows will propagate westward under
generally easterly trade winds, supporting overnight and early
morning showers and afternoon convective development across the
interior and western sections of the islands. A seasonal
temperature pattern will also persist, ranging from around 60
degrees across higher elevations in the early morning to the lower
90s across coastal areas by mid-afternoon hours.

&&

.AVIATION...VFR cond will prevail with passing SHRA affecting the
regional waters and JSJ/IST/ISX at times. Btw 17/16Z-17/22Z, SCT-
to NMRS SHRA and Isold-SCT TSRA will develop across the ctrl MTN
range of PR then drift N and W resulting in VCTS at TJBQ and TJSJ
17/17Z-22z. This will cause brief MVFR conds due to low cig and
+SHRA/TSRA. SHRA/Isold TSRA ma affect the coastal waters of Tisx and
TIST durg prd. Winds will calm to light/VRB,bcmg fm E at 10-15 kt
with sea breeze variations and higher gusts aft 17/14z.

&&

.MARINE...Marine and coastal conditions will remain promising for
small craft and beachgoers. Seas of 3 feet or below and winds up
to 10 knots will prevail until late Tuesday night. Nonetheless,
stay alert for afternoon thunderstorm activity and locally
hazardous marine conditions.

Low risk for life-threatening rip currents will also persist;
however, life-threatening rip currents often occur near groins,
jetties, reefs, and piers.

Increasing winds and a weak northerly swell will deteriorate
marine and coastal conditions by the latter part of the week.

&&

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

$$

SHORT TERM...RAM
LONG TERM....ICP
AVIATION...ICP

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
409 AM AST Tue Oct 18 2022

.SYNOPSIS...A seasonal weather pattern will prevail again today.
Influenced by the upper-level polar trough and driven by diurnal
heating and local effects, expect another active afternoon with
thunderstorms capable of producing strong winds, heavy rain, and
frequent lightning activity, mainly across the interior to western
areas in the afternoon. Prolonged periods of rain from slow-
moving showers due to a persisting weak steering flow will lead to
elevated excessive rain hazard risk and, thus, an increased risk
for urban and small- stream flooding. Isolated flash flooding and
mudslides are possible. Despite variations in moisture levels, the
proximity of mid-to-upper lows should maintain unstable
conditions through the weekend into early next week.

&&

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

Unstable conditions will persist aloft today as the polar trough
axis will continue eastward across eastern Puerto Rico and the
U.S. Virgin Islands, followed by a developing Tutt low just
northeast of the northern Leeward Islands on Wednesday. By then,
an upper level ridge will build across the region resulting in
more stable conditions aloft. The combination of a stalled frontal
boundary northwest of the area and a weakly induced surface
trough will maintain sufficient instability aloft and low level
moisture convergence for shower development across the local
waters during the morning, followed by enhanced afternoon
convection across portions of the islands and the coastal waters
later in the day. The relatively moist and active weather pattern
will persist particularly across the central interior and
northwest sections of Puerto Rico including parts of the San Juan
and east interior. Due to the proximity of the upper trough the
USVI may also experience a better chance isolated thunderstorms
with possibly periods of locally heavy rains in isolated areas.
Recent model guidance suggests the coolest mid level temperatures
between -7 and -8 degrees C to shift over eastern PR and USVI
during the afternoon. This along with the fairly light low level
winds and good daytime heating will favor enhanced afternoon
convection in these areas with potential for isolated but strong
thunderstorms and periods of heavy rains including around the San
Juan metro and the U.S.Virgin Islands. In addition due to the
light winds the heaviest activity should first develop across the
central interior then drift west northwest towards the surrounding
municipalities. This scenario will again lead to ponding of water
in roadways and in poor drainage areas, as well as minor urban
and small stream flooding with mudslides remaining a high
possibility in areas steep terrain where soil remain loose and
saturated. Heavy rains and associated excessive runoff will also
lead to sudden water surges along local rivers and streams
particularly those that have had recent heavy rains from previous
days.

Later today into Wednesday, the frontal boundary north of the area
is forecast to weaken while moving farther into the west central
Atlantic and being replaced by a surface high pressure which will
build across the central Atlantic. On Wednesday, weather conditions
are forecast to gradually improve, as the upper trough shifts
farther east and northeast of the region and is replaced by a high
pressure ridge from the west, thus favoring more stable conditions
aloft. In the meantime a surface high pressure ridge will build and
reestablish across the north central atlantic supporting increasing
easterly winds and a more seasonal weather pattern through Thursday.
This should result in periods of overnight and early morning showers
affecting the coastal waters and windward areas, followed by
afternoon convective development steered by sea breeze convergence
and good daytime heating across the interior and western sections of
Pr. Afternoon shower activity around the USVI should be mainly
downwind and on the west end of the islands. Model guidance
continued to suggest the TUTT low to linger northeast of the region
during the period and this will also aid in enhancing the trade wind
showers forecast to cross the region from time to time.

Generally southeasterly winds through Wednesday will promote
slightly warmer temperatures along the north coastal areas, reaching
the upper 80s to lower 90s, across urban and coastal areas with
maximum heat index values reaching or surpassing 100 degrees in
isolated spots.

&&

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

The most recent global model guidance is now in closer agreement,
with somewhat unstable conditions persisting through the weekend
into early next week. This guidance suggests that although ridging
will remain to the west and close to the area, the proximity of
upper-level lows lingering over the northeastern Caribbean will
maintain a weak trade wind inversion and, thus, favorable
conditions for shower and thunderstorm development. These
conditions will not support widespread activity but a more
seasonal weather pattern characterized by overnight/early morning
showers moving over windward areas and afternoon convective
development across the interior and western sections, where
isolated thunderstorm development is likely.

Model-estimated total precipitable water values still suggest
near-normal moisture levels, with brief drying periods by the end
of the workweek and early next week with the entrance of a mid-
level drier air mass. Any surface-induced feature generated by the
upper-level lows, despite their distance, will propagate westward
under generally easterly trade winds, supporting periods of
excessive rainfall and, thus, a flooding hazard risk across the
local islands. A seasonal temperature pattern will also persist,
ranging from the upper 50 degrees across higher elevations in the
early morning to around 90 degrees across coastal areas by mid-
afternoon hours.&&

.AVIATION...Prevailing VRF durg prd. The proximity of an upper trough
will enhance passing SHRA with Isold TSRA ovr the regional waters
and en route btw PR and the USVI. This will cause brief MVFR conds
with SHRA en route and VCSH at TJSJ and the USVI terminals through
18/14Z. Aftn convective development will bring VCSH/Isold TSRA at
TJSJ/TJBQ/TJPS between 18/17-23Z, with MVFR and Mtn top obscr psbl.
Sfc wnds will remain light and variable, increasing to around 10
knots with sea breeze variations after 18/14Z.

&&

.MARINE...Marine and coastal conditions will remain promising for
small craft and beachgoers. Seas of 3 feet or below and winds up
to 10 knots will prevail until late tonight. Nonetheless, stay
alert for afternoon thunderstorm activity and locally hazardous
marine conditions. A low risk for life-threatening rip currents
will also persist; however, localized life-threatening rip
currents often occur near groins, jetties, reefs, and piers.
Increasing winds and a weak northerly swell will deteriorate
marine and coastal conditions by Wednesday onwards.

&&

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

$$

SHORT TERM...RAM
LONG TERM....ICP
AVIATION...RAM
PUBLIC...ICP

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
425 AM AST Wed Oct 19 2022

.SYNOPSIS...A seasonal weather pattern will prevail during the
next few days, with overnight/early morning showers affecting
windward areas and afternoon shower development over the interior
and western sections of Puerto Rico, where thunderstorm
development is likely. Showers development is also possible
downwind from El Yunque into the San Juan metro area and the local
islands. Flooding impacts are likely with any prolonged period of
moderate to heavy rain. Excessive heat will also remain a hazard
risk during the next few days. The proximity of upper-level lows
and associated surface features should maintain wet and unstable
conditions through the weekend into early next week.

&&

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

A weak frontal boundary well north of the region will continue to
dissipate as a surface high pressure ridge builds and spreads across
the north central Atlantic. This will induce a light southeasterly
wind flow across the area. A tutt low will continue to develop and
linger northeast of the northern Leeward islands while a mid to
upper level ridge will build from the west and hold across the
region. This will maintain overall stable conditions aloft and thus
limit widespread convective development. The overall pattern will
support a gradually increase in the easterly winds by the end of the
period with a seasonal weather pattern expected through Friday.

Occasional periods of passing overnight and early morning showers
will affect the regional waters and windward areas each day,
followed by afternoon convective development influenced by sea
breeze convergence and good daytime heating especially across the
interior and western sections of PR. Afternoon showers in and around
the USVI will be limited during the period and should be mainly
downwind and on the west-end of the islands. Afternoon convection
over PR will produce periods of heavy rains in isolated areas and
this may lead to ponding of water n roads and in poor drainage areas
as well as minor flooding in urban areas and along small streams.
Significant rainfall accumulations and impacts are not anticipated
for the USVI. Model guidance continued to suggest the TUTT low to
linger northeast of the region during the period and this will
therefore aid in enhancing cloudiness and the nocturnal tradewind
showers forecast to cross the region from time to time.

Generally southeasterly winds will persist today then become more
easterly on Thursday and Friday. This will promote slightly warmer
temperatures once again along the north coastal areas, reaching
lower 90s in some of the urban and coastal areas with maximum heat
index values expected to range between 100 and 107 degrees in
isolated spots.

&&

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

A wet and unstable weather pattern will persist through the
weekend into early next week, with the highest chance for
significant rainfall accumulations likely by Tuesday onwards. In
the meantime, the most recent global model guidance suggests that
ridging will remain over the area, but the proximity of upper-
level lows will maintain a weak trade wind inversion and, thus,
potentially favorable conditions for shower and thunderstorm
development. The first low will linger and amplify to our
northeast through late Monday after merging with another low
forecast to meander to our east-northeast throughout the workweek.
With possibly the most significant influence over the area, the
second low will begin propagating southeastward from the Bahamas
region while amplifying until its axis stretches southward over
the Hispanola into the southwestern Caribbean on Tuesday before
lifting to the north-northeast after that. Under its upper-level
wind divergence pattern over the forecast area, this feature will
set the conditions for deep convective development. On top of
this, the associated surface-induced trough will also lift north-
northeastward, bringing deep tropical moisture from the Inter-
Tropical Convergence Zone into the region, with model-estimated
precipitable water totals as high as 2.3 inches by late Tuesday
night.

Both GFS and ECMWF model guidances agree on the existence of this
feature, but there are some disagreements on its evolution, with
the GFS guidance favoring a more aggressive tendency. The current
forecast leans towards the more aggressive and wet guidance, and
if this scenario materializes, expect an elevated risk for
excessive rain, leading to urban and flash flooding impacts.
However, there is low confidence in this scenario, and further
monitoring of this feature is strongly recommended.

&&

.AVIATION...VFR conds durg prd. Periods of passing SHRA will cont
over regional waters with SCT ocnl Bkn cld lyrs nr FL025...FL050.
VCSH at TJSJ and USVI terminals til 19/13Z but no sig wx impacts
anticipated. Fm 19/17z-19/22Z SHRA/ psbl Isold TSRA fcst for W-NW PR
and at TJBQ/TJMZ and brief MVFR due to low cig/reduced VIS with aftn
convection at times. VCSH at TJSJ fm 19/18Z-22Z with brief Mtn Top
obscr along the ctrl Mtn range of PR. Sfc wnds lgt/vrb, incr to 10
to 12 knots after 19/14Z with ocnl hir gusts and local sea
breezes.

&&

.MARINE...Although increasing winds up to 15 knots and a small
northeasterly swell will cause seas to build up to 4 feet, mainly
across the offshore Atlantic waters, marine conditions will remain
promising for small craft. Nonetheless, stay alert for afternoon
thunderstorm activity generating locally hazardous marine
conditions.

Low risk for life-threatening rip currents will prevail today;
however, localized life-threatening rip currents often occur near
groins, jetties, reefs, and piers. The risk will elevate to
moderate tonight for northern Puerto Rico, Culebra, and the
northern U.S. Virgin Islands.


&&

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

$$

LONG TERM...RAM
SHORT TERM...ICP
AVIATION...RAM
PUBLIC...ICP

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
450 AM AST Thu Oct 20 2022

.SYNOPSIS...
Surface high pressure ridge across the north central Atlantic and
a tropical wave and broad low level trough east of the Lesser Antilles
will maintain east to northeast tradewinds through Friday. A TUTT low
and associated mid to upper level trough extending across the northern
Leeward Islands into the southeast Caribbean, will aid in enhancing
the shower activity across the region bringing occasional showers to
portions of the islands and coastal waters overnight. Peripheral moisture
in advance of the weak tropical wave forecast to cross the southeastern
Caribbean will combine with local effects and daytime heating to support
afternoon showers and isolated thunderstorms across portions of the
islands each day.

&&

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

Between today and Saturday, expect limited impacts from excessive
heat and lightning but elevated impacts from excessive rainfall,
mainly from locally- and diurnally-induced afternoon convective
development. Based on the latest 2 AM AST Tropical Weather Outlook
issued by the National Hurricane Center, tropical cyclone development
is not expected during the next five days.

The forecast area will stay enclosed between a weak ridge to the
west and an amplifying low to the east at the mid to upper levels.
Despite the trade wind inversion generated by the ridge, the
proximity of the low will not allow further strengthening; thus, the
inversion will remain prone to erosion from daytime heating
processes and predisposed to convective development. Precipitable
water values should generally stay at normal seasonal levels of
around 1.7 inches through the cycle. Yet, a band of deep tropical
moisture sheared by the upper-level low, originating from the
northern edge of a tropical wave located east of the Leeward
Islands, will reach the region today, causing precipitable water
values to rise around 1.9 inches. Marginally unstable conditions
aloft with plentiful tropical moisture influenced by sea breeze
convergence and diurnal heating will lead to an active afternoon
with isolated thunderstorm development capable of producing limited
lightning and thunderstorm wind impacts. Although at 10 to 15 mph,
the expected east-southeast steering flow should favor relatively
slow-moving showers. As a result, there is a potential for elevated
excessive rain hazard risk impacts, mainly across the interior and
western to northwestern sections of Puerto Rico, where urban and
small stream flooding with possible isolated flash floods and
mudslides are likely. Showers and an isolated thunderstorm are
possible downwind from El Yunque into the San Juan metropolitan area
and downwind from the local islands.

A more seasonal shower pattern will return on Friday and Saturday
when precipitable water values return to seasonal levels, but
localized impacts from excessive rain are still possible. Daytime
maximum temperatures are forecast to peak into the upper 80s to
lower 90s between the late morning and early afternoon hours before
the onset of afternoon convective development when the solar
radiation is at its peak. The combination of southeasterly trade
winds and high moisture levels will lead to limited excessive heat
impacts, with heat index values as high as 102-107 degrees, mainly
across coastal and urban areas of northern and western Puerto Rico.

&&

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

-A seasonal weather pattern is forecast through Monday except for
a weakly induced easterly perturbation forecast to bring passing
low level clouds and occasional showers to the region. Scattered
afternoon showers and possibly isolated thunderstorm can be
expected particularly over the interior and west Puerto Rico.
Mostly isolated showers possible in the San Juan metro and
around the U.S. Virgin Islands where mostly sunny skies and fair
weather should should prevail.

-Tutt low weakens and lifts farther northeastward while a mid to
upper level ridge builds overhead through the most of the weekend
but erodes late Sunday into early next week with the approach of
a polar trough from across the western Atlantic bringing the
unstable upper level conditions to the region.

-As suggested by recent model guidance, the combination of the
aforementioned amplified long wave polar trough, cooler mid level
temperatures along with an induced surface frontal trough and a
vigorous tropical wave approaching the region, all favor
increased instability aloft and a very moist and wetter pattern
by Tuesday and continuing through at least Thursday with good
pooling of deep tropical moisture. Slight improvement and drier
and more stable conditions with a low concentration Saharan dust,
is forecast by the end of the period accompanying and following
the tropical wave.

-Expected impacts are moderate to high potential so far for urban
and flash flood flooding. There is still some inconsistencies in
the timing and evolution of the overall active weather pattern
during the middle and latter part of the period as both the
preferred GFS and ECMWF remain in disagreement, with the GFS
still being the more aggressive model which at this time so far
has been initializing fairly well in recent days.

-Regardless, work of note is the soil conditions have not
completely dried out and remain fairly saturated in several areas
over Puerto Rico. Consequently, any additional rains will only
aggravate the loose and unstable soil especially in areas of
steep terrain. Be aware and remain alert of the surrounding area
especially in times of heavy rains.

-Low level wind profile suggests a moderate east winds becoming
east northeast through Friday, then east southeast again on
Sunday and Monday following a weakly induced easterly
disturbance. Winds are forecast to diminish and becoming more
easterly thereafter, as a vigorous tropical wave and increasing
moisture is forecast to approach the region Tuesday through
Thursday.

&&

.AVIATION...
Mainly VFR conditions will prevail across all local terminals
through the cycle. Trade wind SHRA may result in brief MVFR
conditions at TJSJ and USVI terminals through 20/14Z and after
20/22Z. Afternoon SHRA/Isold TSRA development could also result
in MVFR conditions, with the highest impact at TJSJ and TJBQ
between 20/16- 22Z. Light and variable will prevail through
20/14Z, becoming more easterly and increasing 10-15 knots with
higher gusts and sea breeze variations after 20/14Z.

&&

.MARINE...
Gentle to Moderate easterly winds and a small northeasterly swell
will create choppy conditions and promote slightly building seas
across the Atlantic waters by Friday night and into the weekend.
Seas generally 3 to 5 feet or less, with highest seas expected
over the Atlantic waters. Afternoon isolated thunderstorms will
remain possible near west and northwestern coastal waters of
Puerto Rico.

&&


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

$$

SHORT TERM...ICP
LONG TERM....RAM
AVIATION...ICP

[cycloneye]

Tropical Storm Roslyn Discussion Number 6
NWS National Hurricane Center Miami FL EP192022
400 AM CDT Fri Oct 21 2022

Roslyn's structure has evolved since the previous advisory. A more
distinct core of deep convection appears to be developing, and
infrared satellite images have even shown hints of an eye feature
during the past few hours. An elongated convective band now
extends around the northeastern and southeastern quadrants of the
circulation. Based on consensus Dvorak estimates of T3.5 from TAFB
and SAB, and a CI number of 3.4 from the UW-CIMSS ADT, Roslyn is
now estimated to have maximum winds of 55 kt.

Recent scatterometer data and conventional satellite images
indicate that Roslyn's center is a bit to the northeast of where it
was estimated to be last evening, and the initial motion is
west-northwestward, or 300/6 kt. The track forecast reasoning has
not changed. Roslyn is expected to recurve around the western edge
of a mid-level area of high pressure that will migrate eastward
across Mexico during the next couple of days. In 2 to 3 days,
Roslyn and its remnants are then expected to accelerate
north-northeastward in the flow ahead of an approaching deep-layer
mid-latitude trough. With the exception of the UKMET model (which
is a western outlier), there is very little cross-track spread
among the other track models, and most of the differences are in
the forward speeds after 36 hours. The biggest change in this
forecast package is that with the northeastward adjustment of
Roslyn's center, the entire official track forecast has been
shifted east of the previous prediction, and lies close to the
updated TVCE and HCCA consensus aids.

If Roslyn is indeed developing a better-defined core, environmental
conditions could support rapid intensification (RI). The SHIPS RI
indices are now showing a 50 to 60 percent chance of a 30-kt
increase in intensity over the next 24 hours, and the HWRF,
COAMPS-TC, and HCCA consensus aids are all showing RI. RI is
therefore now explicitly forecast, and Roslyn should reach
hurricane strength later today. In 36 to 48 hours, an increase in
southwesterly shear could induce some weakening, but regardless,
Roslyn is expected to reach the coast of west-central Mexico as a
hurricane. Rapid weakening is expected after landfall, and
although the official forecast shows a remnant low over northern
Mexico in 72 hours for continuity, Roslyn is likely to have
dissipated by that time.

Given the relocation of Roslyn's center and the updates to the
forecast, hurricane and tropical storm warnings are now in effect
for portions of the west-central coast of Mexico. Hurricane
watches have also been extended northward along the coast.


Key Messages:

1. Roslyn is forecast to be a hurricane when it passes near and
makes landfall along the west-central coast of Mexico late Saturday
and Sunday, accompanied by strong winds and a potentially dangerous
storm surge. A Hurricane Warning is now in effect for a portion of
the west-central coast of Mexico and will likely be extended
northward later today.

2. Heavy rainfall could lead to flash flooding and possible
landslides in areas of rugged terrain over coastal southwestern and
west-central Mexico.


FORECAST POSITIONS AND MAX WINDS

INIT 21/0900Z 16.2N 103.8W 55 KT 65 MPH
12H 21/1800Z 16.6N 104.6W 70 KT 80 MPH
24H 22/0600Z 17.4N 105.5W 85 KT 100 MPH
36H 22/1800Z 18.7N 106.2W 95 KT 110 MPH
48H 23/0600Z 20.5N 106.2W 95 KT 110 MPH
60H 23/1800Z 23.0N 105.1W 70 KT 80 MPH...INLAND
72H 24/0600Z 25.7N 103.3W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 25/0600Z...DISSIPATED

$$
Forecaster Berg

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
457 AM AST Sat Oct 22 2022


.SYNOPSIS...

A seasonal pattern is forecast for the short term period, with
typical shower activity in the afternoon hours. A more unstable
weather pattern is forecast on Tuesday and onwards as instability
from an upper level trough and plenty of tropical moisture
reaches the local islands. That said, expect periods of heavy rain
and the threat of flooding for most of the period. Marine
conditions will remain tranquil with seas up to 5 feet and winds
up to 15 knots.


&&

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

Winds at the surface are decidedly east northeast today, but will
gradually become east southeast Sunday and Monday after a weak
low-level trough moves through and a weak ridge at the surface
noses into the northeastern Caribbean Sea. Moisture will remain at
or slightly above normal values with mid levels just cool enough
to spawn isolated thunderstorms each afternoon in the local
convergence and sea breeze pattern that is so typical for Puerto
Rico. At upper levels a ridge will approach the area today and
Sunday while a low pressure will develop off the eastern coast of
Florida. As the trough that passed through the area on Sunday
strengthens flow at 700 mb will become south and will pull
moisture in from South America toward the end of the day on
Monday. This and the deepening trough west of the area will set
things up for the more active long term period.

&&

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

An unstable weather pattern is suggested for most of the long
term period. An upper level trough moving southeastward into the
western Atlantic and eventually over the central Atlantic, will
induce instability and divergence aloft for most of the period.
Combined with the instability aloft, plenty of moisture from a
tropical wave moving west into the area and convergence at the
low levels will aid the development of long-lasting strong showers
and thunderstorm activity each afternoon across the forecast
area that will also continue well into each night. So far, with
the latest guidance the wettest period will be between Wednesday
and Friday, when winds at the surface will shift more from the
east southeast and pull an abundance of moisture from the ITCZ
with PW values above climatological normals across the region.
Given the south component of the winds on Wednesday and Thursday,
the focus of the showers will be more across the central interior
and the northern areas. On Friday into Saturday, the GFS model
suggests a change in the surface pattern as a surface low
develops over the Caribbean Sea and induces a more southeast wind
flow. Embedded in this winds pattern, plenty of tropical moisture
will remain in place. However, this solution has some
discrepancies with the ECMWF model solution for the amount of
water content available across the region. Regardless of the
differences in the solutions, the forecast calls for widespread
shower activity in the afternoon hours each day, mainly across the
central Interior, the northwestern quadrant and the San Juan
Metro area. Given the expected conditions, there an elevated
threat for flooding and thunderstorms. Residents and visitors
should keep track of the possible flooding in urban areas and
water surges in the local rivers.

For the last part of the forecast, there is a lot of uncertainty.
GFS model guidance suggests a more east northeast wind flow,
due to the development of a surface low system just north of
Venezuela over the Caribbean Sea near the ABC Islands on Sunday.
Meanwhile, the ECMWF does not have the same solution. Having said
that, our forecast calls for a normal active day with the
afternoon activity across the interior and the west southwest.
However, since it is too early to determine the wind and moisture
pattern on Sunday, this is quite uncertain.

&&

.AVIATION...Sct SHRA will cont across ern PR and arnd the USVI
thru arnd 22/16Z. SHRA activity will dvlp in wrn PR aft 22/16Z
with isold TSRA psbl bringing lcl MVFR conds and mtn obscurations.
ENE LLVL flow will reach the sfc arnd 22/13Z and increase to
10-15 kts mainly alg the coasts and modified by sea breezes.

&&

.MARINE...

Seas will generally remain 5 feet or less across all the local
waters and local passages. A small northerly swell is forecast to
reach the local islands today through Sunday producing some
isolated locally rougher areas. Winds will remain up to 15 knots.
Afternoon thunderstorm activity will result in locally hazardous
marine conditions mainly off the west coast of Puerto Rico.
A moderate risk for life-threatening rip currents will prevail
today, however, localized life- threatening rip currents often
occur near groins, jetties, reefs, and piers. The risk will
continue to be moderate tonight and tomorrow for northern Puerto
Rico, Culebra, and the northern U.S. Virgin Islands.

&&

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

&&

$$

SHORT TERM...WS
LONG TERM....LIS
AVIATION...WS
PUBLIC...LIS

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
531 AM AST Sun Oct 23 2022


.SYNOPSIS...

A seasonal pattern is forecast today and tomorrow, with the
typical shower activity in the afternoon hours. A more unstable
weather pattern is forecast on Tuesday onwards as instability from
an upper level trough and plenty of tropical moisture reaches the
local islands. For the last part of the upcoming week, model
guidances continues to show some discrepancies. Residents should
monitor closely the forecast during the next several days.


&&

.SHORT TERM...Today through Tuesday...
Above normal moisture and an approaching trough prolonged shower
activity over the local waters with isolated clusters of
thunderstorms occurring in the Mona Channel and north of Puerto
Rico. Another area of showers formed in the northeast portion of
the forecast area and was likely spawned by the upper level low
northeast of the area. These showers are passing around the
northern U.S. Virgin Islands and approaching Puerto Rico at this
time. Good and slightly above normal moisture will continue
across the area through tonight as the trough currently across the
Leeward Islands moves into the area during the day. This will
contribute to continued showery weather during the morning over
eastern Puerto Rico and areas to our east including the U.S.
Virgin Islands. Better moisture will move into the area on Monday
when the 700 mb flow is expected to turn nearly south and
precipitable water values increase from 1.5 inches Monday morning
to 2.3 inches on Tuesday. During this time a low level trough will
extend from Panama into the Dominican Republic and begin to
encroach on Puerto Rico by early Tuesday morning. Showers and
thunderstorms will increase considerably across the area and
increase the coverage of urban and small stream flooding.

An upper level ridge is being squeezed between a TUTT low 700
miles northeast of the southeast corner of the forecast area and
a polar trough deepening just east of Florida. The ridge will pass
over the area Sunday evening and the trough will move over
Hispaniola late on Tuesday. At this time very active weather is
expected on Tuesday and will set the area up for a wet period that
carries into a good portion of the long term period.

&&

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

The long term forecast will start with a very wet and unstable
pattern. An upper level trough deepening into the western Atlantic
will induce instability and divergence aloft for most of the first
part of the period. As this polar trough sinks more to the south,
with the axis over the west of the Hispaniola, it will induce a
surface trough just west of Puerto Rico. This surface trough, in
combination with a tropical wave crossing the area, will generate
a convergence zone, pulling tropical moisture from the ITCZ over
the region. This pattern in the low levels, with all the
instability aloft and colder temperatures at the mid levels, will
aid the development of deep convection across the local Islands.
So far, the wettest days for the long term forecast will be
Wednesday through Friday. However, the timing and the intensity of
the showers will depend on the cloud coverage and the diurnal
heating across the Islands. So far today, our forecast calls for
widespread shower activity in the afternoon hours each day, mainly
across the central interior, the northwestern quadrant, and the
San Juan Metro area. Given the expected conditions, there is an
elevated threat of flooding and thunderstorms. Residents and
visitors should keep track of the possible flooding in urban areas
and water surges in the local rivers.

The model guidance continues to show inconsistency for the last
part of the forecast. The ECMWF continues to shows the typical
easterly trade wind pattern and slightly above normal moisture,
which will result in a seasonal pattern across the region.
However, the GFS model guidance suggests a more east northeast
wind flow due to the development of a surface low system just over
Venezuela over the Caribbean Sea on Sunday. According to the
latest run (23/00Z), the system will move northwestward,
increasing the water content across the region once again. Taking
into consideration all the uncertainty of the long term, our
forecast calls for a normal active day on Sunday and Monday with
the afternoon activity across the interior and the west southwest.
However, residents and visitors are urge to stay tuned for
further updates or new information.

&&

.AVIATION...SHRA will move into NE PR around dawn and activity
will continue to increase--first across ern PR and then aft arnd
23/1530Z across the rest of PR. TSRA will dvlp ovr WNW PR and
parts of the interior with MVFR/IFR conds and mtn obscurations.
Imprvg cond are expected aft 24/00Z. Sfc winds ENE-E 10-15 kts
bcmg aft 23/22Z land breezes of 10 kt or less. Max winds NW 35-40
kts btwn FL 450-475.


&&

.MARINE...

A small northerly swell is affecting the Atlantic waters,
resulting in seas up to 5 feet, with seas up to 6 feet in some
localized areas. For the rest of the local waters, seas will
generally remain 5 feet or less. Moderate easterly winds will
remain 15 knots or less across most of the local waters. Some
brief afternoon showers will result in locally hazardous marine
conditions. There is a moderate risk for life-threatening rip
currents today across all the north, west and eastern coast of
Puerto Rico, Culebra and the U.S. Virgin Islands.

&&

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

&&

$$

SHORT TERM & AVIATION...WS
LONG TERM & PUBLIC....LIS

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
534 AM AST Mon Oct 24 2022


.SYNOPSIS...

For today, the local pattern will dominate the diurnal pattern as
a slot of slightly drier air moves in, eroding the available
moisture somewhat. However, afternoon shower activity is forecast
across the interior and northwest quadrant. A more unstable
pattern is forecast from Tuesday onwards as more moisture and
divergence aloft move over the forecast area. As a result, the
forecast includes scattered showers and thunderstorm activity for
each afternoon and a considerable increase in rainfall with some
possibility for flooding. At this time the greatest rainfall is
expected on Wednesday.


&&

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

A narrow band of slightly drier air is arriving on the east and
southeast coast of Puerto Rico at this time. It will move through
the area by this afternoon in southeasterly low level flow. Then
moisture from a developing trough will begin accumulating in the
convergence zone southwest of Puerto Rico. The moisture from a
weak tropical wave will move into the eastern Caribbean on Tuesday
and the two troughs will converge over Puerto Rico on Wednesday
bringing the best chances of rain to the area and possibly upwards
of 5 inches of rain from Tuesday morning to Friday morning. The
ECMWF is bringing some of this moisture to the area also, but not
as much as the GFS and the moisture flow is now a little farther
east than previous runs, so there still remains considerable
uncertainty regarding the timing and amount of rainfall. A flash
flood watch was considered for Tuesday and Wednesday, but will
not go with it yet since the GFS has backed off from its forecasts
from the last 48 hours. Nevertheless the pattern is conducive to
excessive rainfall and now the National Hurricane Center is noting
a low pressure developing near the Bahama Islands that will
increase the southerly flow and moisture advection over the local
area.

At upper levels a very sharp trough has developed just off
Florida's eastern coast and is expected to form an upper level low
later today. The jet around the southeastern quadrant of the low
will increase in strength over the eastern most Bahama Islands
with pockets of this jet passing through the northwestern portion
of our forecast area. This could serve to enhance the strength of
the convective activity expected in the area on Tuesday. The
trough containing the upper level low is expected to cross over
the Dominican Republic on Wednesday around 26/15Z and across
Puerto Rico from the southwest around 27/00Z Wednesday evening.
Areas of divergence aloft should intensify all the activity
expected on Wednesday. Everyone in Puerto Rico and the U.S. Virgin
Islands should monitor weather conditions and forecasts for the
next several days as this potentially serious situation develops.


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

The weather pattern will continue to be unstable and very wet for
the beginning of the long term period. The main feature will be an
upper level trough deepening into the western Atlantic, inducing
instability and divergence aloft on Thursday into Friday. As this
upper level trough sinks more to the south, with the axis will be over
the west of Hispaniola and the Mona Passage, it will induce a
surface trough just west of Puerto Rico. The latest Tropical
Weather outlook gives some cyclonic potential for this surface
trough. The presence of this surface trough (of low pressure), in
combination with the moisture from a tropical wave will generate
a convergence zone over the area, with surface winds from the
southeast. This combination of some instability aloft and colder
temperatures at the mid levels from the upper trough and plenty of
moisture, well above above the climatological normal, will aid
the development of deep convection across the local Islands. So
far, the wettest days for the long term forecast will be Thursday
through Friday. Therefore, Puerto Rico and the U.S. Virgin Islands
can expect widespread shower activity each day in the afternoon
and evening hours. Showers and thunderstorms will likely continue
into the nighttime hours over the local waters as well. Given the
expected conditions, there is an elevated threat of flooding and
thunderstorms. Residents and visitors should keep track of the
possible flooding in urban areas and water surges in the local
rivers.

Inconsistency is the best word to describe the weather pattern
for the last part of the period, Saturday into Tuesday. The global
model GFS insists on the development of a low pressure system
over the surface just north of Venezuela near the ABC Islands on
Friday. According to the latest run (24/00Z), the system will move
northwestward over the Caribbean waters far south of the U.S.
Virgin Islands on Sunday, moving westward and eventually moving a
few miles south of Ponce, at some point on Monday. This pattern
of a low pressure system at the surface will increase the water
content across the region increasing the potential for a shower
activity. On the other side, is the ECMWF model, this one
continues to show the typical easterly trade wind pattern with
slightly above normal moisture. This solution, from the latest run
(24/00Z), will result in a seasonal pattern across the region.
Considering all the long-term uncertainty, residents and visitors
are urged to stay tuned for further updates or new information.

&&

.AVIATION...VFR conditions across the FA will prevail through
24/16Z. Sct SHRA are expected in ern PR aft 24/15Z and this
development will spread into interior and west northwest PR by
24/18Z with SHRA/isold TSRA generating MVFR conds and mtn
obscurations. Due to southerly flow at lower levels these conds
could briefly affect TJSJ/TJBQ and TJMZ btwn 24/17-21Z. SHRA/TSRA
will diminish aft 24/23Z. LLVL winds ESE-SE 10-15 kts, but will
bcm mostly SE less than 7 kt aft/25/22Z. Maximum winds W 50-60 kts
btwn FL410-460.

&&


.MARINE...

A small northerly swell will continue to affect the
Atlantic waters today, where seas of up to 5 feet are expected.
For the rest of the local waters, gentle to moderate winds will
result in seas up to 4 feet. By midweek, the small northerly swell
will diminish. However, winds will become more moderate to
locally fresh, turning the seas choppy. Afternoon thunderstorm
activity will result in locally hazardous marine conditions.
A moderate risk for life-threatening rip currents will prevail
today; however, localized life-threatening rip currents often
occur near groins, jetties, reefs, and piers. The risk will
continue to be moderate tonight for northern Puerto Rico,
Culebra, and the northern U.S. Virgin Islands.

&&



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

$$

SHORT TERM & AVIATION...WS
LONG TERM & PUBLIC....LIS

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
544 AM AST Tue Oct 25 2022

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

.SYNOPSIS...
Issued at 436 AM AST Tue Oct 25 2022

A trough developing over Hispaniola will move into the area
Wednesday where it will join a westward moving trough over the
area. Where the trough will stall once merged is still uncertain,
but it is likely over eastern Puerto Rico or the U.S. Virgin
Islands. The trough is expected to return to the west on Saturday
after long periods of drenching rain and scattered thunderstorms.

&&

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

As suggested by the GFS for the next few days, a very interesting
weather pattern is expected across the region. A wet and unstable
weather pattern will aid the development of shower activity
across the region. According to the GOES-16 PWAT Imagery, plenty
of moisture at the surface will remain in place for the forecast
area today. This moisture in combination with local and diurnal
heating will result in a seasonal weather pattern for the morning
into the early afternoon hours. The forecast for this morning
includes typical shower activity in the windward and local
sections in the morning, followed by the convection across the
interior and northwestern quadrant. As the day progresses, a more
unstable weather pattern and additional moisture will reach the
forecast area, as suggested the latest run (25/00Z) for the upper
level from both global model guidance (GFS and ECMWF). Both
solutions agree with an upper level trough sinking into the
western Atlantic with the axis located just over Haiti. This
feature will induce a surface trough just south of the Mona
Passage, which will reduce the pressure gradient over the area
and bring a southerly shift in the wind pattern. Given these
conditions, for this afternoon expect extended period of heavy
showers and thunderstorms across the interior and north central
areas. Early on Wednesday, the arrival of a tropical wave, now
located well east of the islands in the Central Atlantic, will
increase the water content across the area even more. This
moisture will arrive in the forecast area just in time to combine
with the upper dynamics and colder temperatures at the 500 MB. The
combinations of these variables will enhance the potential for
strong shower activity across the eastern coast of Puerto Rico,
Culebra, Vieques, the U.S. Virgin Islands and some portions of the
San Juan metro area during very early in the morning on Wednesday
through Wednesday early in the afternoon. After that, weather
conditions will continue deteriorate. There is an elevated threat
of flooding and thunderstorms. Residents and visitors should keep
monitor weather conditions for flooding in urban areas and water
surges in the local rivers. On Thursday, the GFS solution (from
the 25/00Z run) has a low pressure monitored by the National
Hurricane Center with a low chance of formation in the next five
days developing just north of Puerto Rico. This feature will turn
the wind pattern will once again bring southeast winds and will
keep dragging moisture across the region. Basically, a similar
solution is suggested by the ECMWF. No matter, wet conditions are
forecast for the lower levels. The GFS is suggesting some drier
air in the mid to the upper levels. This slightly drier air in
combination with a more zonal flow at the upper levels could
suppress somewhat the vertical motion. Nevertheless, the amount of
moisture and the local effects will be enough for shower activity
with at least isolated thunderstorms.

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

At present many small circulations are forming around systems in
the Atlantic and Caribbean waters and this will also characterize
the first few days of the long-term period. On Friday low level
convergence highlighting abundant moisture will be found east of a
trough extending to the south over the Mona Channel from a low
pressure north of the area. A tropical wave, currently around
30 degrees west and south of 12 degrees north will enter the
Caribbean waters Friday night in the easterly flow across the
tropical Atlantic. This is expected to begin the formation of low
pressure just north of the coast of Venezuela west of the ABC
islands. This low pressure will augment the easterly flow over the
local area and the central portion of the eastern Caribbean
waters and cause the area of convergence to leave our forecast
area and cross the Dominican Republic Saturday through Monday.
This will usher in somewhat drier air. (The GFS lowers
precipitable water values over San Juan from 2.15 on Friday to
1.95 on Sunday morning.)

The models do not agree on the intensity of the developing low
pressure which the GFS takes into the Central Caribbean waters
southwest of our forecast area. Nevertheless the models do not
bring the system into the area. If the system develops into a
tropical storm according to the GFS it would pass south of the
Mona channel Monday night and begin to pull in another pulse of
tropical air rich in moisture into the southern and southwest
portion of the forecast area through the end of the forecast
period. It would also cause seas to increase considerably over the
Caribbean waters beginning on Monday. If it does not, scattered
showers typical of the season would ride through the area for the
remainder of the forecast period (Saturday through Wednesday) in
the usual diurnal pattern of overnight and early morning showers
in eastern Puerto Rico and the U.S. Virgin Islands and afternoon
showers in the western and interior portions of Puerto Rico.

At upper levels, the axis of a sharp short-wave trough will have
already passed the forecast area to the northwest on Thursday.
However a cut-off low may form north of the Bahama Islands that
will cause another weak axis to pass through Friday night and
Saturday. When it does, a ridge will form over the area Sunday and
Monday. This will also prove to be favorable to any tropical
development in the Caribbean that can gain enough vorticity to
launch, as warm waters and moisture are certainly already there.

&&

.AVIATION...
(06Z TAFS)
Issued at 436 AM AST Tue Oct 25 2022

VFR conditions are expected through at least 25/17Z. Winds
will continue VRB at 6 knots until 25/14Z, after that, east winds
5-15 kt will dvlp, shifting to the S by around 25/18Z. Some VCSH
are possible over TJSJ, TISX and TIST during the morning hours.
VCTS are possible over TJBQ at around 25/19Z, elsewhere SCT-BKN
high clouds will cont. An increase in SHRA and VCST is expected
for all the eastern TAF sites at around 25/22Z, gusty winds and
variable winds are expected.

&&

.MARINE...
Issued at 436 AM AST Tue Oct 25 2022

The entrance of several troughs from opposing directions will
cause winds to become variable across the local area. A minor
northeasterly swell will continue to enter the area. Seas will
increase locally on Wednesday night in the local outer Atlantic
waters but are not expected to exceed 7 feet before Monday. Small
craft Advisories may be needed if tropical development in the
Caribbean occurs over the weekend.

&&

.HYDROLOGY...
Issued at 436 AM AST Tue Oct 25 2022

With the increasing moisture rain amounts during the next 48 hours
are expected to be between 2 to 5 inches. Areas that have already
had considerable rainfall are likely to experience urban and small
stream flooding at a minimum and possible more widespread flash
flooding with river rises in a worst case scenario (10 percent
exceedance). A decision will be made today whether a flash flood
watch will be necessary.

&&

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

$$

SHORT TERM...WS
LONG TERM....LIS
AVIATION...LIS

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
542 AM AST Wed Oct 26 2022

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

.SYNOPSIS...
Issued at 457 AM AST Wed Oct 26 2022

An upper level trough has created an active band of convergence
with showers and thunderstorms that will move across Puerto Rico
today and into the U.S. Virgin Islands. A tropical wave will also
move into the area from the east creating very wet conditions over
most of the area. A flash Flood Watch is in effect for Puerto Rico
and the U.S. Virgin Islands. Conditions will improve somewhat
through the rest of the week but both Puerto Rico and the U.S.
Virgin Islands are expected to be wet through at least Friday,
with showers and thunderstorms in rich moisture carrying on well
into next week.

&&

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

The short term forecast remains on track. An upper-level low and the
associated surface trough in combination with a tropical wave will
maintain wet and unstable weather conditions today and tomorrow.
This will cause widespread shower activity along with thunderstorms
across the region. As a result, a Flash Flood Watch was issued for
all of Puerto Rico and the U.S. Virgin Islands, where urban and
flash flooding impacts are likely, including mudslides in areas of
steep terrain. With the activity of today and tomorrow, rainfall
accumulations will range between 6 and 8 inches with isolated
maximum amounts of 10 inches over the eastern third of Puerto Rico
and between 2 to 6 inches, elsewhere. Residents and visitors
should remain alert for flooding in urban areas and water surges
in the local rivers.

On Friday, as the upper-level low and associated surface trough
moves northward, the wind pattern at the surface will turn from the
southeast, setting up low-level convergence over the area. This will
promote moisture pooling across the forecast area with plenty of
tropical moisture increasing precipitable water values above
climatological normals. Therefore, expect an active weather day,
especially in the afternoon hours with enhancement of local and
diurnal effects. Continued flood impacts are also likely on
Friday.

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

The upper level trough to our northwest will move northeast
Saturday and Sunday, but some influence will still be felt. As it
goes by, the 700 mb high in the central Atlantic will be able to
push some drier air into the area and this will reduce the over
all precipitable water values--though not below 2 inches. But, a
tropical wave currently near 50 west and 8 degrees north will move
into the southeastern Caribbean Sea on Friday and there is a fair
probability at this time that it will initiate cyclogenesis near
the coast of Venezuela. By Saturday night, the southeast flow
diverted around this low will already be bringing another surge of
moisture into the area that will continue the wet pattern through
at least Monday night. Currently, the GFS does not develop this
low substantially until Tuesday night or Wednesday and this will
allow modestly moist air to replace the supercharged tropical
airmass that the system will have brought up Saturday night
through Monday. Actually, with one minor exception Sunday morning,
precipitable water values will remain above 2 inches through
Tuesday morning of next week where normal is around 1.7 inches.
This continued moisture in modestly unstable air (500 mb
temperatures remain between minus 5 and minus 6 degrees the whole
time) will bring scattered showers and thunderstorms with local
urban and small stream flooding each day in an easterly windflow
pattern. Because of the already saturated soils, flooding and
mudslides will continue to be a risk throughout the period.

&&

.AVIATION...
(06Z TAFS)
Issued at 457 AM AST Wed Oct 26 2022
Poor weather conditions will persist through the forecast period.
Sct-Num SHRA and TSRA will continue thru 26/18z across the most
of PR and the USVI resulting in periods of MVFR conds across all
TAF sites. Additionally, +SHRA with VCTS & TSRA are expected over
the north coast of PR affecting the regional waters and the local
flying area. SFC winds will remain from the E-SE at 10 kt with
higher gusts near the thunderstorms, increasing to 10- 15 kt
around 26/14Z with sea breeze variations. Maximum winds 30-45 kt veering
from SSW at FL220 to WSW at FL500. Strongest winds at FL350, 400
and 470.

&&

.MARINE...
Issued at 457 AM AST Wed Oct 26 2022

Marine conditions will remain generally southeast 10 to 15 knots,
but will be variable around showers and thunderstorms and in the
vicinity of a north-south oriented trough currently over the
western third of Puerto Rico. This trough will move across Puerto
Rico and the waters north and south of it today and stall around
the U.S. Virgin Islands tonight through Friday. Locally stronger
winds will bring seas up to 6 feet in the activity. Winds turn
toward the east on Saturday as the trough returns to the west will
and remain easterly through Wednesday.

&&

.HYDROLOGY...
Issued at 457 AM AST Wed Oct 26 2022

A very wet period across Puerto Rico and the U.S. Virgin Islands
has begun. Rainfall amounts over the local waters have exceeded 5
inches in the last 12 hours, and since midnight, 3.5 inches have
fallen over the eastern part of Guayama. Much of the south coast
has received over one half inch. Many areas this week have
received considerable rainfall and will be subject to debris flows
including boulders that can drop onto roads without warning.
Residents are urged to exercise extreme caution if they must
travel today and tomorrow. For more details please see the Flash
Flood Watch issued by the National Weather Service.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Flood Watch through Thursday evening for PRZ001>013.

VI...Flood Watch through Thursday evening for VIZ001-002.

&&

$$

SHORT TERM...DS
LONG TERM....WS
AVIATION...LIS

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
448 AM AST Thu Oct 27 2022

.SYNOPSIS...

Wet and unstable weather conditions are expected to prevail
throughout the workweek into the weekend due to the interaction
between an upper-level low and a tropical wave. A Flash Flood
Watch have been issued due to the excessive rainfall expected with
this event.

&&

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

A Flash Flood Watch is in effect for Puerto Rico and the U.S. Virgin
Islands through this evening. Please refer to the latest Flash Flood
Watch (FFASJU) for more information

An unsettled weather pattern will continue today across the region
as an upper-level trough and associated surface trough continues to
promote moisture pooling across the islands. However, the upper-
level trough is gradually weakening and 500 mb temperatures are
expected to remain around -5.5C through the short term period.
Meanwhile, a weak upper-level ridge will gradually build across the
eastern Caribbean and a surface high pressure over the central
Atlantic will promote moderate southeasterly trades across the
region. This scenario suggest a slow drying pattern through the
weekend, with PWAT values forecasted to decrease from around 2.30
inches today to near 2.00 inches on Saturday. Regardless, this
moisture content is still above normal values, and showers and
thunderstorms are expected to develop each day in diurnal activity.
Today should be the wettest day, in terms of areal coverage across
all islands. Then, a more seasonable pattern is expected on Friday
and Saturday with nighttime convection favoring the windward areas
of the islands, followed by afternoon convection downwind of the
islands and across portions of the interior and western PR.


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

The inherited forecast is still on track. On Sunday, expect
another moisture surge to reach the forecast area, as the low-
pressure system approaches. This wet pattern will prevail through
the first part of the workweek. Latest model run is suggesting
that Tuesday will be the peak of the event, with moisture contents
reaching 2 inches. The National Hurricane Center is monitoring
this system and is giving it a 50% chance of development within
the next five days. At this time, the system does not represent a
direct impact on the local islands other than an increase in
moisture content across the region. The main threats with this
event are flooding and mudslides, due to how saturated the soils
are. Urban and small stream flooding is very likely with the
passage of this weather feature. Expect Wednesday to be a
transition day, as models suggest a more seasonal weather pattern
through at least Friday.

&&

.AVIATION...Sct-Num SHRA with Isold TSRA will continue to affect the
regional waters and the local flying area today, as a tropical wave
continues to cross the region while interacting with an upper-level
trough. SCT ocnl bkn lyrs nr FL025..FL050...BKN-OVC lyrs btw FL080-
FL120. Winds will increase from the east-southeast at 10 to 15 kts
with sea breeze variations aft 14Z.


&&

.MARINE...Increasing winds and the passage of a tropical wave
across the regional waters will maintain choppy seas and hazardous
conditions today, mainly across the offshore Atlantic, Caribbean
waters and coastal waters surrounding the U.S. Virgin Islands,
Vieques, Culebra, and eastern Puerto Rico. As a result, small
craft operators should exercise caution due to occasional seas up
to 6 feet and east to southeasterly winds up to 20 knots. Please
refer to the latest Coastal Waters Forecast (CWFSJU) issued by WFO
San Juan PR for latest updates.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Flood Watch through this evening for PRZ001>013.

VI...Flood Watch through this evening for VIZ001-002.

&&

$$

SHORT TERM...DS
LONG TERM....MMC
AVIATION...LIS

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
450 AM AST Fri Oct 28 2022


.SYNOPSIS...

Unsettled weather conditions will prevail today into
early this weekend due to remaining moisture from the upper-level
trough. Due to the expected excessive rainfall impacts, a Flash
Flood Watch remains in effect through this evening. The proximity
of an area of low pressure and the associated plume of moisture
may induce wet and unstable weather conditions from Sunday into
early next week. Persistent showers and thunderstorm activity,
increasing winds, and a small northeasterly swell will cause
choppy to locally hazardous marine conditions during the next day
or so.

&&

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

A Flash Flood Watch remains in effect for Puerto Rico and the U.S.
Virgin Islands through this evening. Please refer to the latest
Flash Flood Watch (FFASJU) for more information

Upper-level trough northwest of the area will gradually lift further
north, while a ridge slowly builds over the northeastern Caribbean
through the short term period. At the surface, a lingering trough
with axis just west of the area will continue to promote moisture
pooling over the islands, and an unsettled weather pattern is
expected today, mainly across the local waters and portions of
Puerto Rico. Due to saturated and loose soils, any period of
moderate to heavy rainfall could lead to flash flooding and
mudslides, as well as rapid river rises. Therefore, a FFA continues
in effect through at least this evening.

Looking further into the weekend, the scenario looks somewhat
complicated, as an area of low pressure at the surface is expected
to form off the lingering trough across the Caribbean waters. The
rainfall forecast will be driven by where the low forms, if it
develops to our south (GFS solution) then, an increase in the areal
coverage of showers could likely persist into early next week or if
it develops more to our southwest (ECMWF solution) then, Sunday
should be our wettest day. Regardless of both solutions, and taking
into consideration the evolution of the past few days weather
pattern, and the proximity of the surface and upper-level troughs,
there is still the potential for shower and thunderstorm activity
across the region. Therefore, please continue to monitor the weather
conditions during the weekend before doing any outside activities.

&&

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

On Monday, expect conditions to continue deteriorating as the
low-pressure system moves close to the forecast area. The National
Hurricane Center is monitoring this area of low pressure and is
giving it a 60% chance of development, as environmental conditions
seem favorable and conducive for gradual development. At this
time, models continue to suggest the peak of the event on Monday
and Tuesday, with moisture values in the 2 inches, close to the 3
inches. Still, this system does not represent a direct impact on
the local islands. Nevertheless, an increase in moisture content
across the region is anticipated. The main threats to this event
are flooding and mudslides due to how saturated the soils are.
Urban and small stream flooding is very likely with the passage of
this weather feature.

By midweek, models suggest a more seasonal weather pattern. The
latest model run remains uncertain from the end of the work week
into the weekend. However, both the GFS and the ECMWF models
suggest a wetting pattern with a trough and a tropical wave
merging. Therefore, it is best to continue monitoring the weather
conditions.

&&

.AVIATION...Unsettled weather conditions will continue across the
local region. SHRA/TSRA is expected to develop once again over the
islands, causing mtn top obsc and BKN/OVC layers btw FL030-120.
Therefore, tempo MVFR conditions across local terminals will remain
possible throughout this evening. Winds will increase 12-16 kt after
28/13z out of SE/ESE.

&&

.MARINE...Moderate east southeasterly winds up to 20 knots can be
expected over the offshore Atlantic waters and local passages
with seas up to 6 feet, and 10 to 15 knots and 5 feet or less
elsewhere. Please refer to the latest Coastal Waters Forecast
(CWFSJU) issued by WFO San Juan PR for latest updates.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Flood Watch through this evening for PRZ001>013.

VI...Flood Watch through this evening for VIZ001-002.

&&

$$

SHORT TERM...DS
LONG TERM....MMC
AVIATION...DS

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
514 AM AST Sat Oct 29 2022

.SYNOPSIS...

Moisture remains high across the region and it will prevail
through the end of the weekend, resulting in an increase in shower
activity. For Sunday, the magnitude of this increase in showers
is uncertain, as well as the location of the activity, associated
with uncertainties with the potential development of Invest 95L
over the Caribbean. While this system is not expected to have
direct impacts over the area, its effects on instability and
steering flow will impact conditions on Sunday, resulting in
decreased confidence in the forecast over the local islands. The
wet pattern will likely continue into midweek.

&&

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

Increasing trade winds brought showers across portions of the U.S.
Virgin Islands and east/southeast Puerto Rico through the overnight
hours. Rainfall accumulations so far were less than a quarter of an
inch. This surge in moisture today, will also aid in diurnal
convection and showers with isolate thunderstorms are expected to
develop across the interior and western sections of PR during the
afternoon hours. Also, streamers are expected to develop downwind of
the USVI and eastern sections of PR, with the highest rainfall
accumulations expected across San Juan and vicinity.

For the rest of the weekend into Monday, a developing surface low
pressure well south of the area is expected to increase moisture
content across the region. As the low pulls further west and away of
the eastern Caribbean, an advective weather pattern is expected to
prevail in a moist southeasterly wind flow. Therefore, expect an
increase in coverage of showers with possible isolated thunderstorms
tonight into Sunday, mainly across the Caribbean waters, the USVI,
and across eastern and southern PR as well. Due to already saturated
soils across PR, the risk of flooding will remain elevated through
the short term period. Elsewhere, showers are still expected, but
the main flood threat remains across the eastern half and southern
sections of PR.

&&

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

The remaining moisture from the surface low pressure will prevail
as it moves close to the forecast area. The National Hurricane
Center continues to monitor this area and it now has a 70% chance
of development, as environmental conditions remain favorable and
conducive for gradual development. Still, this system does not
represent a direct impact on the local islands. Nevertheless, an
increase in moisture content across the region is anticipated for
Tuesday. The main threats to this event are flooding and mudslides
due to how saturated the soils are. Urban and small stream
flooding is very likely with the passage of this weather feature.

Models continue to suggest a more seasonal weather pattern from
Wednesday into Thursday. However, wetter conditions will return by
the end of the workweek and weekend. At this time, both the GFS
and the ECMWF models agree and are showing a wetting trend with a
trough and a tropical wave merging. Therefore, it is best to
continue monitoring the weather conditions.

&&

.AVIATION...Mainly VFR conditions expected across all terminals
through the fcst period. However, trade wind SHRA may cause brief
MVFR cigs at times across the USVI and eastern PR terminals, and
+SHRA/+TSRA developing over western PR this afternoon should cause
tempo MVFR conds at TJBQ. East winds expected at 12-18 kt with
higher gusts and sea breeze variations after 29/14z.

&&

.MARINE...Moderate to locally fresh east southeast winds of 10 to
15 knots can be expected with seas between 4 to 6 feet over the
offshore waters and local passages and 1 to 3 feet elsewhere.
Please refer to the latest Coastal Waters Forecast (CWFSJU) issued
by WFO San Juan PR for latest updates.

&&

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

$$

SHORT TERM...DS
LONG TERM....MMC
AVIATION...DS

[cycloneye]

National Weather Service San Juan PR
503 AM AST Sun Oct 30 2022

.SYNOPSIS...

An ample moisture field related to Invest 95L over the central
Caribbean will continue to affect our region today into early
next week. Today showers and thunderstorms under a generally
southeasterly flow will impact most of the region but will mainly
be more continuous over the southern waters, eastern and
southeastern Puerto Rico, Vieques, Culebra and the USVI. Showers
and thunderstorms during the afternoon hours over central and
western Puerto Rico are also posible. The threat of flooding and
mudslides is elevated in areas of persistent showers.

&&

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

Scattered showers prevailed across portions of the U.S. Virgin
Islands and east/southeast Puerto Rico through the overnight hours
due to a surge in moisture. Rainfall accumulations up to three
quarters of an inch were observed in eastern PR. Once again, this
surge in tropical moisture could aid in diurnal afternoon convection
across portions of the interior, northern and western PR. Also,
streamers are expected to develop downwind of the USVI and eastern
sections of PR, with the highest rainfall accumulations expected
across San Juan and vicinity.

For the rest of the short term period, the situation was re-
evaluated, and there is still some level of uncertainty, therefore
the forecast remains unchanged from previous modifications. In
general, the weather conditions will be driven by a broad area of
low pressure over the central Caribbean Sea. This will promote
abundant tropical moisture in a southeasterly steering wind flow
across the region. Therefore, expect an increase in coverage of
showers with possible isolated thunderstorms, mainly across the
Caribbean waters, the USVI, and across eastern and southern PR as
well. Due to already saturated soils across PR, the risk of flooding
will remain elevated through the short term period. Elsewhere,
showers are still expected, but the main flood threat remains across
the eastern half and southern sections of PR.

&&

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

On Wednesday, expect a more seasonal pattern across Puerto Rico
and the U.S. Virgin Islands as a mid-upper level ridge positions
across the area. This pattern should persist through at least
Thursday. By Friday, conditions will deteriorate slightly as
another moisture surge reaches the islands. The latest model run
suggests that the precipitable water values at the end of the
workweek will fluctuate between 1.00 and 1.50 inches. Afterward,
the precipitable water content will increase to 2.30 inches or
higher. During the weekend, the weather conditions look more
unstable due to a deep layer of low developing over the
southeastern Atlantic. This weather feature will create a
southerly wind flow across the eastern Caribbean, pulling deep
tropical moisture into the area. Therefore, due to the available
moisture, unsettled weather conditions are anticipated.

&&

.AVIATION...Mainly VFR conditions are expected across most of the
forecast period. However, increasing SHRA/TSRA across the Caribbean
waters may cause tempo MVFR conds across the USVI terminals and TJPS
throught the day. Additional showers and iso tstms may develop in
and around TJSJ and TJBQ btw 16z-22z. East to southeast winds
expected at 10-15 kt with higher gusts and sea breeze variations
after 14z.

&&

.MARINE...Showers and posible isolated thunderstorms under
moderate to locally fresh southeast winds will prevail today.
Seas up to 5 feet and up to 6 feet occasionally. There is a
moderate risk of rip currents for most of the local beaches across
Puerto Rico and the USVI.

&&

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

$$

SHORT TERM...DS
LONG TERM....MMC
AVIATION...DS

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
503 AM AST Mon Oct 31 2022


.SYNOPSIS...
Potential Tropical Cyclone Fifteen will promote above-normal
moisture content across the U.S. Virgin Islands and Puerto Rico
through Tuesday as it moves westward across the Caribbean Sea. A
more seasonal weather pattern can be expected by mid-week with an
unstable wetter pattern returning this weekend as a polar trough
approaches from the northwest.



&&

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

Potential Tropical Cyclone Fifteen will promote above-normal
moisture content across the U.S. Virgin Islands and Puerto Rico
through Tuesday as it moves westward across the Caribbean Sea.
Although mid to upper-level dynamic is not favorable for organized
and deep convection, afternoon convection due to local effects and
sea breeze convergence will develop mainly across the interior and
western sections of the islands each day. In addition, showers
embedded in the trades will affect the windward areas during the
night and early morning hours. Also, urban flooding is possible
across the San Juan Metropolitan area if El Yunque Streamer develops
late this morning into the afternoon. Keep in mind that soils are
saturated, and river levels are above-normal; therefore, the risk of
flooding, mudslides, and sudden water surges along river tributaries
will remain high each day with the most vigorous rain activity.

Moisture will slowly erode late Tuesday into Wednesday in Puerto
Rico and the U.S. Virgin Islands, promoting a typical seasonal
weather pattern consisting of trade wind showers early in the
morning, followed by afternoon convection over the interior and
western sections.


&&

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

A seasonal weather pattern will prevail on Thursday with below
normal to near normal moisture content across the area. Under an
east southeast wind flow, expect passing showers during the
morning hours affecting eastern coastal areas of the local
islands, later developing across western and northwestern
portions of Puerto Rico in the afternoon. Some isolated
thunderstorms are possible promoting localized urban and small
stream flooding.

A gradual change in weather pattern can be expected by Friday
through the weekend as a polar trough and eventual cut-off low digs
into western Atlantic, northwest of the CWA. The positioning of the
trough will favor divergence aloft and cold air advection at mid-
levels increasing instability across the northeastern Caribbean. An
induced surface trough will pull deep tropical moisture from the
south increasing precipitable water values to above 2.0 inches.
This setup will be very conducive for deep convective activity.
Therefore, expect periods of heavy rain due to widespread shower
and thunderstorm development through at least early next week.
Winds will gradually shift with a more southeastern component
between Friday and Saturday and south/southwest by Sunday into
early next week. As winds shift, light steering flow is
anticipated elevating the flood potential associated with this
event. Flash flooding can also be expected if this forecast
materializes, as well as rapid river rises and mudslides in
affected areas. We`ll need to monitor forecast trends over he
coming days as this scenario could lead to additional flooding
issues across already vulnerable areas across the islands.


&&

.AVIATION...
(06Z TAFS)
Issued at 454 AM AST Mon Oct 31 2022

VFR conditions will prevail. SHRA will affect USVI terminals without
significant impacts. Local effects will aid in the formation of
SHRA/TSRA between 31/16-22z across the interior and western PR and
downwind from El Yunque and the USVI. This activity may affect
JPS/JBQ/IST/ISX. Expect calm to light and variable winds thru
31/13z, and then they will return from the ESE at around 10-15kt
with sea breeze variations.

&&

.MARINE...
Issued at 454 AM AST Mon Oct 31 2022

Wave heights will be limited to under 5 feet across all the local
waters for the next several days. Moderate southeasterly winds
will prevail, with locally fresh winds across the Caribbean
Waters. Shower and Thunderstorm activity will remain elevated
across the Caribbean Waters due to a tropical disturbance in the
Central Caribbean, elsewhere lighter shower activity is expected.
Rip Currents will remain moderate to low across the local beaches.

&&

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

$$

SHORT TERM...CAM
LONG TERM....CVB
AVIATION...CAM

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
506 AM AST Tue Nov 1 2022


.SYNOPSIS...Weather conditions will turn more seasonal in the
coming days. However, a polar trough approaching from the
northwest will promote once again wet and unsettled weather
conditions over the local area by this weekend.


&&

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

Near-to-above-normal moisture content will continue across the U.S.
Virgin Islands and Puerto Rico today while a mid to upper-level
ridge builds aloft. This ridge pattern above will promote subsidence
and dry air at mid to upper levels, limiting organized convection
and widespread activity. Nevertheless, expect trade wind showers
across the local waters and moving inland over the windward
sections, followed by afternoon convection due to local effects and
sea breeze convergence developing mainly across the islands'
interior and western sections each day. Also, urban flooding will
remain possible across the San Juan Metropolitan area due to the
development of the El Yunque streamer during the afternoon. Soil
saturation continues, and river levels remain near to above-normal;
therefore, the risk of flooding, mudslides, and sudden water surges
along river tributaries will remain high each day with the most
vigorous rain activity.

A weak tropical wave will move across the eastern Caribbean Sea on
Thursday. Although the bulk of moisture may remain well to the south
of Puerto Rico and the U.S. Virgin Islands, a jet associated with an
approaching polar trough could enhance afternoon convection.


&&

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

A very wet and unsettled weather pattern continues to be expected
for this weekend and possibly into early next week. Model guidance
maintains the deep-layer polar trough digging southward over western
Atlantic with axis northwest of the CWA by Friday evening. The
positioning of the trough will promote 250 mb height falls, upper
diffluence and divergence pattern over the area along with mid-
level cold air advection. At low-levels, both GFS and ECMWF model
has the trough inducing a surface low over central Caribbean Sea
shifting winds out of the southeast by Friday. While it do so, the
deep-layer trough will interact with a tropical wave, currently
at 57W, while its axis is southwest of Puerto Rico. This will
pull deep columnar moisture across the area by late Friday night.


Overall, this set up will increase the potential for organized
convection with scattered to widespread heavy rain producing
thunderstorms for the early part of the long-term period. Latest
model runs show a slight discrepancy between GFS and ECMWF regarding
the duration of this pattern. GFS prolongs this wet and unstable
weather pattern with winds even turning westerly through early
Tuesday. ECMWF shows the north-south bulk of moisture moving
eastward by Sunday confining the wet pattern mostly over Vieques,
Culebra, and the U.S. Virgin Islands and at times eastern Puerto
Rico, while drier air filters from the west shortening the period
of this wet pattern for western Puerto Rico. Due to this
discrepancy, a slight decrease in POPs was implemented for late
Saturday night into early Sunday. Nevertheless, main global models
are consistent that a strong synoptic forcing will evolve across
northern and northeastern Caribbean over the weekend, possibly
into early next week. With this pattern, an elevated flash flood
threat can be expected for the local islands, as well as rapid
river rises and mudslides in and near steep terrain, especially
over interior Puerto Rico. Although some uncertainty is present,
pay close attention as the forecast for this event continues to
evolve. A gradual improvement of weather conditions is anticipated
by mid- week of next week.

&&

.AVIATION...
(06Z TAFS)

VFR conds will prevail. However, passing SHRA will continue across
the local flying area, with some moving near/over local terminals
(especially over IST/ISX/JSJ). Once again, local effects will aid in
the formation of SHRA/TSRA downwind from the USVI and El Yunque and
across the Cordillera Central, reducing visibility and creating low
ceilings btwn 01/16-22z. This activity may affect local terminals.
Expect calm-light/var winds thru 01/13z, returning from the E at
around 10-15kt with sea breeze variations.

&&

.MARINE...

Gentle to moderate easterly winds and seas at 5 feet or below will
persist for the next several days. Unsettled weather conditions
will increase winds across the regional waters turning seas
hazardous by the weekend. Low to moderate rip current risk will
prevail for most of the workweek.

&&

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

$$

SHORT TERM...CAM
LONG TERM....CVB
AVIATION...CAM

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
504 AM AST Wed Nov 2 2022



.SYNOPSIS...A seasonal weather pattern will prevail for the next
couple of days. However, wet and unsettled weather conditions are
still forecast for Friday through the weekend as a deep-layer polar
trough deepens and surface low settles near the area. A tropical
moisture plume will develop close to the local islands throughout
this period, however, uncertainty remains regarding its exact
location. Coastal and marine conditions will deteriorate in the
upcoming weekend.



&&

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

Today`s weather conditions will be typical for this time of the
year, consisting of a mixture of sunshine and clouds with trade wind
showers moving across the windward areas in the U.S. Virgin Islands
and Puerto Rico throughout the day. Then, afternoon convection will
develop across the mountains of PR and western sections of the
islands. The northeast wind flow will promote thunderstorm activity
across the southwest quadrant sections of Puerto Rico, where urban
and small stream flooding are possible. The maximum air temperatures
and available moisture content will result in heat index values of
100 degrees Fahrenheit or more in urban and coastal areas.

A weak tropical wave crossing the Lesser Antilles today will move
near the archipelago of Puerto Rico and the U.S. Virgin Islands late
tonight into Thursday. Although the bulk of moisture may remain well
to the south of Puerto Rico and the U.S. Virgin Islands, a jet
associated with an approaching polar trough could enhance afternoon
convection on Thursday.

A polar trough will amplify across the northeast Caribbean, inducing
a surface trough and increasing instability across PR/USVI by
Friday. A jet maximum at the upper level will also promote favorable
mid to upper-level dynamics. The GFS and ECMWF Gálvez-Davison Index
(GDI) suggest supportive environmental conditions for the
development of scattered thunderstorms, especially across the
eastern third of Puerto Rico and the U.S. Virgin Islands by Friday
afternoon into the weekend. We encourage residents to stay aware of
the evolution of Friday`s weather scenario due to the current soil
saturation and river streamflows which are prone to the formation of
flooding, mudslides, and sudden water surges along river tributaries.


&&

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

Model guidance persist on a wet and unstable weather pattern for the
weekend across the local islands, especially for Saturday. The deep
layer polar trough, and eventual cut-off low, will continue to sink
southward while strengthening north of Hispaniola. At low-levels,
the induced surface low will shift winds out of the south tapping
into deep tropical moisture and advecting it over the northeastern
Caribbean. This scenario will promote very favorable weather
condtions for development of widespread heavy rain producing
thunderstorms as mentioned in earlier discussions. However, the
location of the moist plume, and hence the area of maximum moisture
convergence, continues to shift between model cycles. GFS persist on
a longer duration of wet and unstable weather conditions through
at least early Monday, but the area with maximum convergence has
shifted a little more eastward than in previous model runs. ECMWF
now has the moist plume even further east confining the wettest
period mostly for Saturday, although instability will remain as
the polar trough will persist over the area at least through early
next week. Additionally, the National Hurricane Center is closely
monitoring the evolution of this event as the broad area of low
pressure that might develop in the vicinity has a low formation
chance in the next five days. Please refer to the latest Tropical
Weather Outlook (TWOAT) issued by the National Hurricane Center.

Even though uncertainty remains, both models agree that
eastern/southeastern Puerto Rico, Vieques, Culebra and USVI could be
impacted the most with this event. Furthermore, soils continue to be
saturated from previous rainfall events in the last few weeks;
rivers are running at near normal to well above normal streamflow
levels, with some running at all-time high levels; and areas of
steep terrain remain vulnerable to additional mudslides with any
rain event. Therefore, pay special attention to the forecast as this
event evolves in the coming days.

The latter part of the long-term forecast will depend on how long
the upper-level features linger across the area with a building
ridge out east moving over the northeastern Caribbean. This will
bring a more seasonal weather pattern over the local islands,
possibly by mid-week of next week.

&&

.AVIATION...
(06Z TAFS)

VFR conditions will prevail. However, passing SHRA will continue
across the local flying area, with some moving near/over local
terminals (especially over IST/ISX/JSJ). Local effects/sea breeze
variations will promote SHRA/TSRA downwind from the USVI and El
Yunque, and across the Cordillera Central between 02/16-22z. This
activity may affect local terminals and create low ceilings and
mountain obscuration. Expect calm to light and variable winds thru
02/13z, followed by NE-ENE at 10-15kt with sea breeze variations.
&&

.MARINE...

Gentle to moderate easterly winds will prevail over the
next few days. The risk of rip currents is moderate to low for
the local beaches of Puerto Rico and the USVI. Coastal and marine
condtions will deteriorate in the upcoming weekend.

&&

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

$$

SHORT TERM...CAM
LONG TERM....CVB
AVIATION...CAM

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Thu Nov 3 2022

.SYNOPSIS...

A mixture of sunshine and clouds will prevail today. However, a
weak tropical wave will promote afternoon convection across the
interior and western sections of Puerto Rico, near the San Juan
Metro Area and downwind from the USVI. A polar trough approaching
from the west will promote an unstable and wet pattern Friday
through early next week. Therefore, special attention to the
forecast for this event is advised as it evolves during the next
few days.

&&

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

Ridging aloft is slightly being pushed by a polar trough that is
starting to strengthen and descend from the Eastern Seaboard;
however, drier air above the 600 mb layer will persist throughout
the day inhibiting somewhat the effects of ridge erosion at upper-
levels. At lower-levels, GOES-16 Total Precipitable Water
estimates values between 1.5 to 1.6 inches over the forecast area
which is below normal to near normal climatological levels for
this time of year and is expected to remain within these values
today. Therefore, under an east southeast steering wind flow, a
seasonal weather pattern is expected during the day with advective
showers affecting the windward coastal areas of the local islands
during the morning hours and diurnally induced afternoon showers
and isolated thunderstorms developing across the Cordillera
Central and western/northwestern Puerto Rico. The San Juan metro
area could observe heavy showers and brief isolated thunderstorms
in the afternoon as well. Streamers downwind of the smaller
islands can be expected with some brushing eastern portions of
Puerto Rico at times. Urban and small stream flooding can be
observed with this activity. Localized flash floods cannot be
ruled out.

By Thursday evening and onwards, weather conditions will gradually
deteriorate through the weekend as a complex pattern unfolds. First
the leading edge of a tropical wave, currently located over 63W,
will start to filter in the evening hours. As it moves westward, the
tropical wave will pass mostly south, but will increase moisture
content across the CWA throughout Friday. Instability aloft will
also gradually increase as the aforementioned polar trough continues
to sink in and settles northwest of the area. Dynamics aloft will
become favorable as cold air advection and a divergent pattern
establishes over the northeastern Caribbean. At low-levels, a broad
area of low pressure will start to develop west of the area inducing
a southerly flow by Friday evening. This deep-layer trough will
interact with the tropical wave and even pull additional deep
tropical moisture from the south by Friday night into Saturday.
Uncertainty remains regarding the area of maximum moisture
convergence, but models have been consistent that southeastern
Puerto Rico, Vieques, Culebra and U.S. Virgin Islands will be most
impacted by this weather pattern, with Saturday being the most
active day.

With this set up, a more enhanced convective pattern can be expected
on Friday as high moisture content and instability interacts with
surface heating during the day. The area of heaviest rain will
gradually increase with numerous showers and scattered thunderstorms
developing over interior and northwestern quadrant of Puerto Rico.
Convective activity will become widespread by Friday evening and
overnight hours. For now, model guidance has most of the activity
slowly moving eastward by early Saturday through the end of the
short-term period. However, this will all depend on where the area
of maximum convergence develops. Therefore, continue to monitor the
evolution of this forecast as this event has the potential of
causing widespread thunderstorm activity capable of producing gusty
winds and heavy rain over already saturated soils, rapid river rises
and mudslide events.

&&

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

Model guidance, once again, indicated unsettled weather
conditions from Friday (from the Short Term Period) through early
next week associated with a strong TUTT-Low lingering through late
Monday night. The confidence remains low-moderate concerning the
exact location where the rainfall maxima will occur as the ECMWF
and GFS continue flip-flopping around it. Both models suggest that
the southern and eastern sections of Puerto Rico, the U.S. Virgin
Islands, and surrounding waters have the highest potential to
observe the maximum precipitation amounts. In addition, the
National Hurricane Center (NHC) continues to closely monitor the
evolution of this event as the broad area of low pressure that
might develop in the vicinity has a low chance of tropical cyclone
formation in the next five days (20 percent). Please refer to the
latest Tropical Weather Outlook (TWOAT) issued by the NHC.

Tuesday through Thursday may be a transition period, exiting the
wet and unstable weather pattern. However, this part of the
forecast will be tight to the evolution of the area of low
pressure, which NHC is monitoring. This system could alter the
wind pattern (inducing a southerly wind flow) and may continue to
lift plenty of tropical moisture from the southeastern Caribbean
over the islands (Northeast Caribbean). Now, model guidance is
leaning toward continuing a wet and showery weather pattern
through next week's second part, pushing the plume of moisture
over the Northeast Caribbean. The confidence is still low because
it will depend on the trajectory of the moisture plume.

&&

.AVIATION...
(06Z TAFS)

VFR conditions will prevail. SHRA will affect USVI
terminals without significant impacts. Local effects will aid in the
formation of SHRA/TSRA between 03/16-22z across the interior and
western PR and downwind from El Yunque and the USVI. This activity
may affect JPS/JBQ/JSJ. Expect calm to light and variable winds thru
03/13z, and then they will return from the ESE at around 10-15kt
with sea breeze variations.

&&

.MARINE...

A small northerly swell will continue to fade across the local
waters slowly. Seas will continue up to 4 feet, and the winds out
from the east at 10 to 15 knots. However, local effects could
locally increase winds and seas each afternoon.

A tropical wave today and an upper-level trough Friday through
the early next week will deteriorate weather conditions across
the northeast Caribbean. Unsettled weather and the arrival of
another northerly swell will cause marine and coastal conditions
to deteriorate over the weekend.

For beachgoers, the risk of rip currents is moderate along the
Atlantic Coastline of Puerto Rico, Vieques, Culebra, and the
Virgin Islands. The risk of rip currents will increase to high
this weekend into early next week for most of the beaches.

&&

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

$$

SHORT TERM...CVB
LONG TERM....CAM