Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
408 AM AST Sat Jul 22 2023

.SYNOPSIS...Drier air with suspended Saharan dust particles will
continue to dominate the region, supporting mainly fair weather,
warm-to-hot, and hazy conditions with limited shower activity
throughout the workweek. An increase in showers with thunderstorm
activity, breezy conditions, and locally choppy to hazardous seas
is likely with the passage of a tropical wave early next week.


&&

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

Tranquil conditions persisted through the night hours. Very isolated
and brief shower activity was observed around Vieques, Culebra and
the U.S. Virgin Islands. Temperatures remained close to the 80
degree mark around the coastal areas.

A thick Saharan Air Layer will persist across the islands through
today, resulting in hazy skies and reduced visibilities. The dust
will finally moves westward, with lesser concentrations anticipated
for Sunday and Monday. Even with the presence of an upper level low
just south of the islands, below normal moisture will prevent
significant shower from forming across the islands. It should not be
completely dry, though, as strong diurnal heating should be enough
to generate showers across the interior and western Puerto Rico in
the afternoon. Light to moderate rainfall accumulation is
anticipated.

As the Saharan Air Layer begin to depart on Sunday, moisture at the
lower levels will flow a little bit better. Precipitable water
values are expected to climb to around 1.8 inches, which is near
normal. On the other hand, the upper level low will migrate toward
Cuba, and 500 mb temperatures will warm up. In general, conditions
will not be favorable for widespread rainfall production, but the
increase in low level moisture should trigger another round of
seasonal showers and thunderstorms across the interior and western
Puerto Rico. Late Sunday and into Monday, another slot of dry air
with Saharan dust will move in. Then, some narrow patches of
moisture associated with the tropical wave AL95 could reach the area
at times. Therefore, variable conditions with periods of sunshine
and others with passing showers are anticipated.

Temperatures will remain on the warm side, especially today, when
the 925 mb temperature will be well below normal. For Sunday and
Monday, temperatures will remain hot, but close to average. Highs
will be in the upper 80s to low 90s, with lows closer to 80 degrees
at coastal areas.

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

Model guidance suggests that despite some variations, precipitable
water content (PWAT) will remain normal to above-normal
climatological levels, between 1.7-2.1 inches, through the long-
term forecast period. Peak PWAT periods above 2.0 inches,
generated by a wind surge and tropical wave, are likely around
Tuesday morning and Wednesday night, respectively. As a result,
expect increased showers with thunderstorm activity and an
elevated excessive rainfall risk. During the rest of the time,
expect the seasonal shower pattern, with limited excessive
rainfall risk from overnight and early morning showers moving over
eastern Puerto Rico and the U.S. Virgin Islands and showers with
isolated thunderstorms over western Puerto Rico in the afternoon.
At the surface, a broad high pressure system across the north-
central Atlantic will maintain east-to-east-southeast winds, but
some deviations are likely with the passage of each feature
mentioned above. Daytime temperatures will continue to peak into
the upper 80s to lower 90s, which considering the expected high-
moisture environment, could result in heat indices of 102 degrees
or higher and the potential for excessive heat risks each
afternoon.

The National Hurricane Center (NHC) continues to monitor an area
of low pressure (AL95) located across the central tropical
Atlantic, with moderate to high formation chance during the next
2-7 days. Although uncertainties are high, AL95 could become a
tropical depression early next week. According to the latest
model guidance, AL95 could enter the eastern Caribbean region and
move south of the local islands between Tuesday and Wednesday,
but this timing window could vary. It is too early to determine
what impacts this system could bring to the area, if any, at this
time. However, residents and visitors should continue to monitor
the evolution of this system with forecast updates issued by the
NHC and the local forecast office.


&&

.AVIATION...HZ due to Saharan dust will persist through the
forecast period, decreasing gradually after 23/00Z. VIS are
expected to be at 6-9SM. SHRA could develop after 18Z around TJBQ
with brief impacts to operations possible due to low ceilings and
reduced VIS. Winds will be out of the ESE at 9-14 kts with
stronger gusts.


&&

.MARINE...Recent CariCOOS buoy network observations around Puerto
Rico and the U.S. Virgin Islands indicated seas between 1 and 3
feet. Across the local waters, seas should remain at 4 feet or
below, increasing to around 5 feet by early next week. Increasing
showers with thunderstorm activity and moderate to fresh winds
generated by a passing tropical wave will yield locally hazardous
marine conditions between Monday and Wednesday. The rip current
risk will stay low for all local beaches today, elevating to
moderate from Saturday onwards.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Excessive Heat Warning from 10 AM this morning to 5 PM AST this
afternoon for PRZ001-004-005-008-010-012.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
512 AM AST Mon Jul 24 2023

.SYNOPSIS...

Variable weather conditions should persist for today across the
islands, with Saharan dust particles and moisture across the area.
On Tuesday, A vigorous tropical wave (Invest 95L), will arrive to
the islands increasing the water content and resulting in more
frequent showers. A wet pattern is forecast for the long-term
period, with a wind surge and a tropical wave moving across the
region. Choppy marine conditions will persist due to wind-driven
seas across the offshore waters.

&&

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

Skies were mostly clear to partly cloudy across the forecast area
during the overnight and early morning hours. Surface high pressure
anchored across the north central Atlantic will maintain light to
moderate easterly winds across the region today. This will aid in
transporting patches of low level moisture with embedded showers
across the regional waters during the rest the morning hours. Some
showers will briefly affect the north and east coastal areas of the
islands from time to time. A tropical wave and area of low pressure
((Invest AL95) still east of the Windward islands is forecast to
continue westwards and enter the eastern Caribbean by Tuesday.
Moisture along the leading edge and north of this feature is
expected to arrive across portions the regional waters and affect
the islands beginning later tonight, then gradually increase through
the rest of the period, thus increasing the chance for morning and
afternoon shower development. The prevailing easterlies will also
increase Tuesday through Wednesday as the surface high reestablishes
north of the area and the tropical wave enters the eastern Caribbean.

In the meantime hot and hazy condition will continue with above-
normal morning low temperatures and slightly above normal daytime
high temperatures. Maximum heat index values will range between 100-
108 degrees Fahrenheit in most areas, especially in urban and
coastal areas. Local effects, sea breeze, and excessive heating will
result in afternoon shower development across portions of the west
interior section of Puerto Rico and mainly downwind of the U.S.
Virgin Islands. A few quick passing showers may also be possible
from the Yunque into the San Juan metro area but significant
accumulations are not anticipated.

For the remainder of the short term period increasing peripheral
moisture from the approaching tropical wave is expected, although
the bulk of the associated moisture with this wave is so far
forecast to pass south of the islands. Nevertheless the proximity of
the upper trough (TUTT) the increasing moisture convergence and
instability will favor better chance for morning and afternoon
convection Tuesday through Wednesday with good potential for
enhanced showers with isolated thunderstorms especially during the
afternoon hours. As a result the risk for urban and small stream
flooding as well as ponding of waters on roads in poor drainages
areas will increase Tuesday through Wednesday.

The daytime high temperatures across the forecast area will remain
in the low 90s mainly along the coastal areas and in the mid to
upper 80s at higher elevations. The main impacts continues to be
maximum heat indices between 100-108 degrees along coastal and in
urban areas and also an increase risk for urban and small stream
flooding during the afternoon hours especially Tuesday through
Wednesday.


&&

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

According to the most recent model guidance, a wet weather
scenario is expected in the long-term forecast cycle. By Thursday,
residual moisture from the previous tropical wave will linger in
the area. The available moisture, colder temperatures at 500 MB at
around -7 degrees, and instability aloft will enhance periods of
moderate to locally heavy rain across the region. According to The
Gálvez-Davison Index (GDI), exist the potential for isolated to
scattered thunderstorms with the heaviest shower activity.
Instability conditions will slightly improve on Friday into
Saturday; however, enough trap moisture at the low levels with
PWAT of 1.7 inches, as suggested by GFS, will trigger the
convection with the local and daily effects. Given the east-
southeast winds across the region due to the surface ridge, the
showers will focus on the interior, northwestern, and the San Juan
Metro area. The heaviest activity would result in ponding of
water in roadways and poor drainage area.

By the last part of the period, weather conditions will
deteriorate even more as a wind surge and a second and broader
tropical wave move westward into the region, causing precipitable
water values to rise above 2.0 inches. So far today, both global
model guidance (GFS and ECMWF) agreed on an increase in moisture
across the region. However, the GFS shows a very unstable and wet
pattern with a vigorous wave for Monday, providing enough moisture
in all the levels over the region. Contrarily, the ECMWF shows the
humidity drifted more to the north of the islands. Regardless of
the discrepancies, the forecast calls for a very wet pattern for
Sunday into Monday, with a moderate flood threat for Puerto Rico.

&&

.AVIATION...

VFR conds at all terminal durg prd. Aftn convection
with SHRA/VCTS psbl at TJBQ/TJMZ fm 24/17z-22Z. SCT SHRA psbl at
TJSJ and en route to USVI terminals til 24/14Z. SFC wnds lgt/vrb to
calm bcmg fm E 12-18 kts with sea breeze influences and ocnly hir
gusts aft 24/14Z. VCSH psbl at TJSJ/TIST/TISX terminals fm 24/17Z-
24/23Z.

&&

.MARINE...

A surface high pressure over the Central Atlantic will continue to
promote a moderate to locally fresh east-southeasterly wind flow
across the local waters. That said, expect seas up to 5 feet with
winds up to 20 knots across the offshore waters and Atlantic
coastal sections, where the small craft operators are urged to
exercise cations. For the rest of the local waters, seas will
remain between 2 to 5 feet with winds up to 15 knots. A tropical
wave will deteriorate the local waters today into Wednesday,
resulting in localized hazardous marine conditions due to
thunderstorms and winds. There is a moderate risk of rip currents
across most of the coastal zones of the U.S. Virgin Islands and
Puerto Rico, except the western coast.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
532 AM AST Tue Jul 25 2023

.SYNOPSIS...

An increase in moisture is expected today as a tropical wave
tracked by the National Hurricane Center with a low chance of
formation in the following days moves westward into the region.
This wave is now located over the Lesser Antilles and will move
over the Caribbean Sea during the day. The file of moisture will
induce periods of squally weather across the region. Moisture will
persist across the region from Thursday into Friday, maintaining
the potential for shower activity across the CWA. For the upcoming
weekend, a wind surge will bring periods of heavy showers.

&&

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

Partly cloudy to variably cloudy skies prevailed across northeast
Puerto Rico, Culebra,Vieques and the U.S Virgin Islands, as quick
passing clouds and tradewind showers continued to move in and out of
the area. Meanwhile the rest of Puerto Rico was mostly clear.
Tropical moisture and occasional convective bands along the leading
edge of the tropical wave (Invest 95L), now crossing the Lesser
Antilles, will continue to propagate north and west of this feature
resulting in a gradual deterioration of the local weather conditions
across portions of the U.S. Virgin islands particularly St Croix and
east coastal areas of Puerto Rico later this morning. This is then
expected to spread across the southern,interior and west sections of
Puerto Rico and rest of the islands later in the afternoon and
during the evening hours. Based on the expected condition, the risk
for urban and small stream flooding as well as ponding of waters on
roads in poor drainages areas will be high for today and through
Wednesday with mudslides possible in areas of steep terrain due to
any heavy rains.

The tropical wave is forecast to quickly move westward with the bulk
of the moisture and heaviest convection expected to remain south of
the islands. However, with the increasing instability and good low
level moisture convergence across the interior and southern slopes
of Puerto Rico and St Croix, enhanced afternoon and evening
convection will be possible and may cause periods of locally heavy
flooding rains later today and especially overnight and into
Wednesday.

As the tropical wave crosses the eastern Caribbean, expect the local
pressure gradient to tighten across the region thus resulting in
increasing trade winds today through Wednesday along with breezy
condition and frequent gusty winds, especially along the coastal
areas.

In the meantime sufficient sunshine is expected for the early part
of the period leading to near normal high temperatures and hot and
humid conditions with still above normal low temperatures. Maximum
heat indices will range between 100-108 degrees Fahrenheit in most
areas especially in urban and the north coastal areas. Local terrain
effects, sea breezes, and good heating will favor afternoon showers
and isolated thunderstorm development across portions of the
interior, west and southern slopes of Puerto Rico and mainly in and
around St Croix in the U.S. Virgin Islands. Quick passing showers
and chance of afternoon isolated thunderstorms cannot be ruled out
over the east interior, El Yunque and the San Juan Metro later this
afternoon and during the evening hours. Based on the expected
conditions, the risk for urban and small stream flooding as well as
ponding of waters on roads in poor drainages areas will be moderate
to high for today and through Wednesday or early Thursday morning.
Mudslides will possible in areas of steep terrain as a result of any
heavy rains.

By Thursday afternoon a gradual erosion of tropical moisture is so
far expected as the tropical wave and associated moisture field
exits the region, and an area of Saharan dust and drier airmass
filters in and spreads across the region along with decreasing trade
winds. Southeasterly winds and warmer and slightly above normal
temperatures can again be expected. Showers and isolated
thunderstorm activity will then be focused over parts of the central
interior and northwest Puerto Rico, and downwind of the U.S. Virgin
Islands.

&&

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

A variable pattern is forecast for the long-term period across
the local islands. A broad high pressure at the surface will
dominate the wind pattern within a moderate east-southeast flow
over the Caribbean for Friday and Saturday. Dragged by this wind
flow, Caribbean moisture with PWAT values of 1.6 inches will
filter in the area, maintaining the potential for cloudiness and
shower development. Some unstable conditions, as suggested by the
model guidance, colder temperatures at 500 MB, and the diurnal
effects will induce afternoon showers across the western and
interior sections of Puerto Rico. A wind surge moving westward
into the area will increase moisture and winds from late Saturday
to early Saturday, resulting in wind-driven showers. Just after
that, by early Sunday, the NASA Goddard Earth Observing System
Model V5 suggests an increase in Saharan Dust particles with an
optical depth of 0.2. The particles will suppress shower
development and will result in hazy skies.

For the last part of the period, the uncertainty in the forecast
increases with the arrival of a broad tropical wave with PWAT
values of more than 2 inches, as suggested by the GFS. The ECMWF
suggests a different solution with moisture moving in the CWA but
with the bulk of the water well to the north of the region. Given
the global model guidance discrepancies, the forecast calls for a
wet pattern across the local area, with morning showers across
windward sections and afternoon convection over the interior.
Residents and visitors should stay tuned for further information.

&&

.AVIATION...
VFR conds at all termimals til 25/08z. Thereafter moisture
along the leading edge of a broad area of low pressure and a
tropical wave (AL95) now crossing the Windward Islands will bring
prds of unsettled wx conds with SHRA/Isold TSRA to the flying area
fm 25/09z-15z mainly btw E PR and the USVI. SCT ocnl BKN lyrs nr
FL025...FL040 w/SHRA/Isold TSRA...brief MTN top obscr psbl ovr E PR
til 25/12Z w/SHRA. Incr clds cover and SHRA dvlpmnt ovr the interior
and W PR vcty TJMZ/TJBQ aft 25/16z. Brief MVFR due to SHRA/Isold
TSRA til 25/23Z. Wnds fm E less than 10 kts, incr to 15-20 kt and
gusty to 25-30 kts psbl aft 25/14Z.

&&

.MARINE...
Choppy to hazardous marine conditions will prevail today and
tomorrow across the islands. At the surface, a brad high pressure
over the Central Atlantic will continue to result in moderate to
locally fresh easterly winds across the region. Wind up to 20
knots will result in choppy seas up to 6 feet across all the local
waters. Deteriorating marine conditions are expected tonight as
the tropical wave moves over the Caribbean waters, with seas up to
7 feet, winds up to 20 knots with gusty winds and thunderstorms.
Seas will gradually subside by Thursday. There is a moderate risk
of rip currents across the north, east, and southeast coastal
zones of Puerto Rico, Culebra, Vieques, and the U.S. Virgin
Islands.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
505 AM AST Thu Jul 27 2023

.SYNOPSIS...
A seasonal pattern is forecast for the next couple days and into the
upcoming weekend. Trade wind showers will move over the coastal
waters and affect the windward side of the islands during the
rest of the early morning hours,followed by isolated to scattered
afternoon convection mainly over the west sections of Puerto Rico
and downwind of the U.S. Virgin Islands. A wind surge and
accompanying band of moisture is expected to quickly cross the
area late Friday into Saturday bringing breezy conditions with
better chance for shower development in and around the islands.
East to southeast winds will prevail with temperatures to remain
seasonably hot and slightly above normal. Maximum heat indices
are expected to be above 102 degrees each day, especially in the
urban and coastal areas along the north and west sections of the
islands.

&&

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

Trailing moisture and cloudiness from the previous tropical wave,
now located over the Hispanola, resulted in passing showers across
the local waters and some windward sections of Puerto Rico. The
heaviest activity was observed over the offshore Atlantic waters and
some southeastern sections of Puerto Rico; however, no significant
rainfall accumulations were reported. Overnight temperatures were in
the low 80s across the coastal areas and in the low to mid-70s
across the interior.

Variable weather conditions would persist in the morning with cloudy
skies and brief passing showers over the eastern sections. As the
day progresses, the cloudiness will move out of the region, and a
drier airmass will filter into the area. According to the GOES
derived Imagery, PWAT will fluctuate from 1.6 to 1.4 inches.
Although conditions will improve and clear to partly cloudy will
last, the available moisture and the diurnal and local effects will
enhance the typical afternoon showers across the interior and
western sections. With the heaviest activity, some ponding of water
in roadways and some poor drainage areas is possible.

On Friday, the islands can expect a more east-southeast component in
the wind as the surface high pressure establishes over the Central
Atlantic. Dragged by this wind flow, tropical moisture will move
into the area, increasing the potential for a convective pattern
once again. A more wet and breezy pattern is expected by Saturday.
According to global model guidance (GFS), a wind surge would quickly
move westward into the forecast area. This moisture increase will
enhance periods of moderate to heavy rain with isolated to scattered
thunderstorms, as suggested by the latest Gálvez-Davison Index
(GDI). Therefore, residents can expect an elevated threat risk with
the potential for urban and small stream flooding, primarily where
the heaviest activity occurs.

&&

.LONG TERM...Sunday through Thursday...
On Sunday, rapid improvement is expected as a drier air mass
accompanied by a low to moderate concentration of Saharan dust,
will filter in and spread across the region. This drier airmass
along with the increasing tradewinds will aid in eroding moisture
pooling and thus limit widespread shower activity across the
islands and coastal waters at least until early Monday. Based on
latest model guidance both suggest the driest period to be Sunday
into Monday with more seasonal weather conditions expected dominated
by the Atlantic high pressure ridge and the moderate easterly trades.

For the rest of the period both model guidance continued to suggest
inconsistencies and uncertainty in the overall weather pattern
with the approach of a tropical wave which The National Hurricane
Center continued to monitor now located a couple of hundred miles
southwest of the Cabo Verde Islands. Although inconsistent, both
model guidance (GFS and ECMWF), suggest a chance of further
development as the tropical wave moves westward into Central
Tropical Atlantic. While the GFS,now suggest increasing moisture
transport and northeast winds across the region by late Monday
through Tuesday, the ECMWF model remain less aggressive and
suggest drier condtions with the feature moving even farther
northeast of the region during the same time period. All in all,
expect a gradual increase in tropical moisture and humidity by the
latter part of the period. Given the discrepancies in guidance
for the forecast period, confidence remains low for now due to the
disrupted weather pattern. The expected wind flow for now should
become more east to northeast during the early part of the
period, then become more south to southeast by the end of the
period. Will therefore remain on the conservative side and
continue with the typical summertime weather steered by the
Atlantic high pressure ridge and local steering flow along with a
slight but gradual increase in advective moisture through
Wednesday followed by a drying trend on Thursday.

The overall weather pattern for now is for typical passing morning
showers becoming more frequent Monday through Tuesday, followed by
afternoon convection with isolated diurnally driven thunderstorm
activity each day especially Monday through Tuesday when urban
and small stream flooding will be possible. Please continue to
monitor how the aforementioned feature unfolds and stay tuned for
additional info and updates issued by the local weather office
WFO San Juan and the National Hurricane Center.

&&

.AVIATION...
VFR conditions will likely persist across the local terminal through
the forecast period. However, clouds and VCSH to ISOLD-SHRA are expected
across TJBQ at around 27/18Z. E-SE surface winds of around 10 kts will
continue to increase to 15 to 18 knots aft 27/14Z with sea breezes
variation until sunset, then subside, becoming generally light and
variable.

&&

.MARINE...

Mariners can expect choppy conditions due to winds between 12 to
and 20 knots across the Atlantic, local Passages, and Caribbean
Waters. Local data from surrounding buoys continued to suggest
choppy seas between of 3 to 5 feet across these areas. Mariners
should continue to exercise caution.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
456 AM AST Fri Jul 28 2023

.SYNOPSIS...
Partly cloudy to variably cloudy skies prevailed, with occasional
trade wind showers noted affecting the coastal waters and parts of
the islands overnight. A wind surge and band of moisture in advance
of a tropical wave will continue to approach the region today and
will increase showers by this afternoon into the evening hours. This
combined with local diurnal effects will support afternoon convection
mainly downwind from the USVI and across portions of northeast,central
interior, and northwest Puerto Rico. A low concentration of Saharan
dust will linger across the region today. Excessive heat hazard
risks will be likely each afternoon into the weekend, with maximum
heat indices peaking at 102 degrees or slightly higher.

&&

.SHORT TERM...Today through Sunday...
Passing showers were observed across the local waters and some windward
sections of Puerto Rico. The heaviest activity was observed over the
offshore Atlantic waters and some southeastern sections of Puerto Rico;
however, no significant rainfall accumulations were reported. Overnight
temperatures were in the low 80s across the coastal areas and in
the low to mid-70s across the interior.

Increase in moisture are forecast for later today into Saturday
as a wind surge moves westward quickly into the forecast area.
This increase in humidity and winds will promote a breezy and
convective pattern later today, with more frequent passing morning
showers across the local waters and windward sections of the
islands. This activity will be followed by moderate to locally
heavy showers across the eastern half of Puerto Rico on Saturday
morning, followed by afternoon convection with thunderstorms across
the western interior. According to the latest Gálvez- Davison
Index (GDI) run, the highest chance of thunderstorms will be in
the northwestern sections in the afternoon. Breezy conditions will
result in fast- moving showers, inducing light to moderate rainfall
accumulations. Therefore, the heaviest activity could result in urban
and small stream flooding in localized areas and minor flooding over
the local roadways.

From late Saturday into Sunday, low-level moisture will move out of
the region, allowing a drier airmass filter into the region. According
to the NASA Goddard Earth Observing System Model V5, some Saharan dust
particles will be suspended in the airmass mentioned above. Therefore,
the lack of abundant moisture, the presence of Saharan dust, and the
drier air aloft will therefore favor a more typical pattern across
the region.

&&

.LONG TERM...Monday through Friday...
Latest model guidance suggests drier and more seasonal weather
pattern is expected to continue through Monday dominated by the
influence of the Atlantic high pressure ridge and the moderate
easterly trade winds. Both forecast model guidance are in better
agreement this period and suggest no direct impacts from the
tropical wave which The National Hurricane Center continued to
monitor now located about midway between the Cabo Verde Islands
and the Lesser Antilles. Environmental conditions are expected to
be favorable for gradual development of this wave in the next few
days as the system moves west northwest across the tropical Atlantic.
Overall the wettest days far the period is late Monday into early
Wednesday with a gradual improvement by Thursday and Friday.

The GFS model guidance suggests increasing moisture transport with
initially east northeast winds then becoming southeasterly late Monday
through Tuesday or early Wednesday. Meanwhile the ECMWF model remained
less aggressive suggesting somewhat drier conditions, as the aforementioned
feature continued farther away from the forecast area. For now, will
remain consistent with the present long term forecast and guidance
which suggests a gradual increase in precipitable water content and
tropical moisture late Monday through early Wednesday followed by
diminishing moisture transport along with decreasing southeast winds
as the pressure gradient relaxes and winds become more east northeast
Thursday into Friday.

The overall weather pattern and impacts for the period calls for passing
trade wind morning showers, becoming more frequent late Monday through
early Wednesday, when the chance for urban and small stream flooding
will be possible in isolated areas across parts of the interior, north
and west to northwest sections of Puerto Rico. Ponding of water on
roads and in poor drainage areas can be expected with the heaviest
rains over the U.S. Virgin Islands during this time. Afternoon convection
each day will be locally and diurnally driven with isolated thunderstorm
activity possible each day, but especially Monday afternoon through
Tuesday. This pattern will also favor warmer temperatures and more
of a summertime weather conditions for most of the period.

&&

.AVIATION...VFR conditions will persist for all the TAF sites during
the morning hours. Winds will continue from the east-south at 8
knots, increasing to 15 knots at 28/14Z from the east-southeast with
sea breeze variation in all the sites. VCSH will persist over TJSJ
and TIST until 28/14Z, VCSH to SHRA are expected over TJBQ at
around 28/18Z. Upper-level clouds would result in SCT ceiling until
28/15Z.

&&

.MARINE...
Mariners can expect choppy conditions due to winds between 15 and
20 knots across the Mona Passage, and Caribbean Waters, where
small craft operators should exercise caution. Elsewhere, seas
will be around 15 knots out from the east. Local nearshore buoy
network observed slightly choppy seas around 3 feet and up to 5
feet offshore.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
521 AM AST Sat Jul 29 2023

.SYNOPSIS...
Lingering moisture from a departing tropical wave is expected to
bring extra showers today, with the heaviest activity expected
this afternoon for western Puerto Rico. Some Saharan dust will
filter in today, followed by another tropical wave early in the
workweek. Summer hot temperatures are expected to persist for the
next several days.


&&

.SHORT TERM...

Showers over eastern Puerto Rico dissipated after midnight except
for a few showers which appeared around 2 AM AST. Showers continued
across the local waters and a few thunderstorms were observed in the
southern portion of the outer Caribbean waters. Minimum temperatures
across the area ranged from the mid 60s in the highest mountains to
the lower 80s along the windward coasts and outer islands.

The tropical wave is now moving out of the area and the back edge of
the moisture is approaching the eastern edge of the forecast area.
Precipitable water values were seen as high as 2.2 inches last night
with values upstream just below 1.4 inches east of the area at 60
degrees west. The GFS shows areas of drier air (less than 30 percent
relative humidity) moving into the area by 29/21Z and over much of
Puerto Rico by 30/06Z. This should be enough to quell most of the
showers when it arrives. Another patch of moisture passes through on
Sunday followed by an even smaller dry patch sunday evening. This
moisture will continue to generate scattered showers for the area
with a slight chance of a thunderstorm in western Puerto Rico Sunday
afternoon.

On Monday winds will veer to the east southeast with the
approach of another tropical wave. The hurricane center will be
watching the top of this wave for tropical development which they
give a 20 percent chance of development before Monday. The low
pressure is expected to be 960 miles east northeast of San Juan
Monday morning and too far away for any significant action. The
bottom of the wave, however will pass over the U.S. Virgin Islands
and Puerto Rico late Monday night. Showers and a few thunderstorms
are likely, but at this time moisture is modest and rainfall amounts
are not expected to be excessive.

On Friday 28 July, low pressure at upper levels was found just north
of Haiti, but it will migrate west across Cuba today and higher
pressure will move in over the local area Sunday and Monday. This
will also help to suppress most deep convection over the area.

Owing to a weak southerly component to the general flow near the
surface, and warm sea surface temperatures, daily temperatures are
expected to continue 1 or 2 degrees above normal.

&&

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

Winds out of the south to southeast at the lower levels of the
atmosphere will persist on Tuesday as a tropical wave (AL96)
continues to move well northeast of the Caribbean. It looks like the
southernmost portion of this wave will separate from the main
feature, reaching the local islands. This will maintain moisture
levels slightly above the climatological value, increasing the
potential for showers. As is usual, the strongest activity should be
expected north of the Cordillera Central in the afternoon hours, but
passing showers along with isolated thunderstorms could also be
observed early in the day across the local waters, eastern Puerto
Rico and the U.S. Virgin Islands. By Wednesday, the winds will back
and turn east, but lighter, with a projected low level steering flow
below 10 knots. This change in winds should cause moisture
convergence across the islands, as more patches of moisture moves
from the east. Precipitable water values will climb up to above
normal values, topping at 2.1 on Wednesday and 2.2 inches on
Thursday. The Galvez-Davison index also indicates favorable
conditions for thunderstorm development through Thursday. By Friday,
drier air along with Saharan dust will move in, resulting in hazy
skies. On the weekend, the latest guidance from both the ECMWF and
the GFS has a tropical wave moving mainly northeast of the islands,
with the bulk of the moisture field over the offshore Atlantic
waters. Soon after the wave moves north of the region, high pressure
is expected to build at the low to mid levels, with Saharan dust
once again turning the skies grayish.

&&

.AVIATION...
VFR conditions will prevail. Winds will continue from
the east-south at 8 knots, increasing to 12 to 18 knots arnd 29/14Z
from the east-southeast with sea breeze variation in all the sites.
Isold-sct SHRA with a streamer off of El Yunque psbl aft 29/15Z, but
conds should remain VFR at TJSJ. Showers with isolated thunderstorms
will dvlp aft 29/17Z in wrn PR and along the west half of the
Cordillera Central. Maximum winds E 22-27 kts btwn FL110-120 and
FL195-225 and SW-S btwn FL445-510.

&&

.MARINE...
A departing tropical wave will maintain fresh winds across the
area, resulting in choppy seas. Showers and thunderstorms are also
expected early in the day across the Caribbean waters. Recent buoy
observations have seas at 4 feet nearshore. There is a moderate
rip current risk for most of the local beaches.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
541 AM AST Sun Jul 30 2023

.SYNOPSIS...
Hot temperatures will persist across the region for the next
several days. A tropical wave will approach the region by early in
the workweek, increasing the potential for showers and
thunderstorms. After the wave, patches of clouds and areas of
Saharan dust will reach the islands at times.

&&

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

Skies have been mostly clear with no shower activity for the most
part. After 5 AM AST clouds with a few very light showers formed
downstream from Saint Thomas and Saint Croix. Lower elevation
temperatures ranged from the upper 70s to lower 80s. Land breezes of
less than 6 mph prevailed.

The tropical wave and the potential tropical cyclone have separated
now with the best activity in the wave now 500 miles southeast of
San Juan and 400 miles southeast of Saint Croix. Showers in the wave
are widely scattered and models do not show much improvement. The
National Hurricane center gives AL96 a 40 percent chance of
formation in the next 48 hours, but its best convection is over 1100
miles east northeast of Saint Thomas. Moisture from these two
systems is not expected to reach the southeast corner of our
forecast area until later Monday morning, but once it does, it will
move through rapidly and be mostly clear of the area by Tuesday
afternoon. Some thunderstorm activity is expected mainly late Monday
afternoon through Tuesday morning, but owing to the scattered nature
of the showers, there is only a limited risk of any local flash
flooding. Thunderstorms will very likely also develop over
northwestern Puerto Rico Tuesday afternoon as well.

Models are showing the passage of this wave to be rather sharp and
winds will turn abruptly south southeast Monday night and continue
through Tuesday. This will continue the above normal temperatures on
the south coast with south coast temperatures remaining pretty much
as warm as before, while temperatures on the north coast will rise
into the lower 90s. The GFS is forecasting 1000-850 mb thicknesses
to spike to almost 1430 m on Tuesday and Wednesday. While the NBM is
showing little difference in the maximum temperatures in San Juan
for the entire week despite the wave passage early on. These above
normal temperatures must also be expected for the U.S. Virgin
Islands as well.

Returning to today, a heat advisory has been issued for Culebra, due
to high dewpoints and temperatures and heat indices are expected to
reach at least 108 degrees. In western, northwestern and north
central Puerto Rico, heat indices will exceed 112 degrees from time
to time during the day and a heat warning has been issued there. We
expect the greatest heat to be between 10 AM and 5 PM AST. The
public in these areas is urged to take precautionary measures
including adequate hydration and avoiding sunlit areas during heavy
physical exertion.

&&

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

By the middle of the workweek, the pressure gradient will remain
weakened as the steering flow continues from the east-southeast
below 10 knots. The tropical wave will be departing the region,
giving way to a drier air mass covering the islands. Additionally,
small concentrations of Saharan dust will also be available,
creating hazy skies. Weak ridging will be present at all levels, so
any available moisture should be limited to the lower-most levels
of the atmosphere. On Thursday, some moisture following the flow
of the system AL96 (well northeast of the Caribbean) will reach
the islands, increasing the potential for some showers across the
region. For the rest of the workweek and into the weekend, on and
off patches of moisture are anticipated to cross the region. In
between these areas of clouds, there will be some Saharan dust as
well, but the highest concentrations are expected on Friday and
then again on Monday. No significant weather feature is expected
to prevail through this time, so a seasonal pattern of morning
showers moving across eastern Puerto Rico and the Virgin Islands
can be expected each morning. Afternoons are expected to be
active, but mostly for the interior and west of Puerto Rico, where
lightning and localized urban and small stream flooding can be
observed.

&&

.AVIATION...
VFR conditions will prevail. East northeast winds will increase
to 12 to 18 knots arnd 30/14Z with sea breeze variations at all
sites. Isold-SHRA in a streamer off of El Yunque are psbl aft
30/15Z, but conds should remain VFR at TJSJ. Showers with isolated
thunderstorms will dvlp aft 30/17Z in wrn PR and along the west
half of the Cordillera Central. Maximum winds aloft are ESE 25-30
kts btwn FL100-110 and SSW btwn FL400-420.


&&

.MARINE...
The pressure gradient will weaken, resulting in lighter winds
across the region. As a result, seas will diminish in the next
several days. There is a moderate rip current risk for northern
Puerto Rico and for eastern St. Croix.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
512 AM AST Mon Jul 31 2023


.SYNOPSIS...
Issued at 416 AM AST Mon Jul 31 2023

Tropical waves with some showers and isolated thunderstorms will
move through an otherwise hot and mildly dusty period in the
middle of summer. The tropical waves passages are expected Tuesday
and Friday, but above normal temperatures will continue through
most of the period. Easterly trade winds will prevail between the
wave passages. Afternoon showers and thunderstorms in western
Puerto Rico will continue--only fluctuating in intensity.
Overnight and morning showers will also continue in synchrony with
the ebb and flow of the tropical waves. Rainfall amounts are not
expected to be extreme during the period, but slowing winds could
cause heavier showers to linger in place longer.

&&

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

Passing showers were observed across the local waters, northern and
eastern Puerto Rico, the U.S. Virgin Islands and Vieques and Culebra
under a northeast wind flow. Rainfall accumulations were generally
light. Temperatures cooled down to the upper 70s and low 80s for
coastal and urban areas.

A low pressure system (AL96) continues to move well northeast of the
islands, while the axis of a tropical wave is crossing the Lesser
Antilles. These features will shift the winds from the southeast
today. The moisture field is evident in satellite-derived
precipitable water products, showing values around 2.2 inches.
Before this wave arrives later tonight, a thin slot of drier air
will move through, so goodly amounts of sunshine are expected
during the earlier part of the day. For the afternoon hours, local
effects are expected to generate showers and isolated
thunderstorms across northwestern Puerto Rico. At the same time,
the bulk of the wave will gradually approach the Caribbean waters
and St. Croix. The area of showers and thunderstorms is expected
to spread northward, reaching the northern Virgin Islands and the
eastern half of Puerto Rico in the evening hours. Although the
global and high resolution models are not too aggressive with
rainfall accumulations through the entire duration of the event,
these showers may still result in water surges along the streams
and rivers, and urban and small stream flooding.

Showers will continue to move from the Caribbean Sea on Tuesday,
reaching coastal municipalities of western Puerto Rico and also the
U.S. Virgin Islands. Precipitable water values are expected to be
well above normal on Tuesday. At the same time, winds will become
southerly from the surface to around 700 mb (nearly 10,000 ft),
while the steering flow slow down to about 7-8 kts at lower
levels. On Wednesday, as the wave moves north of the islands,
columnar moisture will decrease, but only at the upper levels.
Moisture levels will be closer to climatological values at the
lower and mid levels. Both days should experience active
afternoons, mainly for the Cordillera Central and the northern
half of Puerto Rico. On Wednesday, however, the winds will have a
southeasterly component, so the focus of the afternoon convection
should be the interior and northwest quadrant of Puerto Rico.
Since the steering flow will be light, the showers could linger in
the same areas, increasing the risk for urban and small stream
flooding, as well as mudslides in areas of steep terrain.

Another aspect that needs to be considered with southerly winds and
a moisture-rich low level atmosphere is the temperatures. So far,
925 mb temperatures are expected to be over two standard deviation
above the climatological value for Tuesday and Wednesday, which
translates in temperatures and heat indices well above normal.
Therefore, areas that are not protected by the cloudiness and the
showers could experience really hot temperatures these days.

&&

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

High pressure in the eastern and central Atlantic will be the
dominant force at the surface with moderate to fresh easterly
trade winds except after the passage of another tropical wave on
Friday and a second on Sunday. Precipitable water values will have
reached a maximum on Tuesday with a secondary peak on Wednesday,
but then moisture falls to its lowest level for the week on
Friday morning. By Sunday the GFS forecasts values above 2.1
inches once again. High pressure at mid levels coincides well with
high pressure at the surface and lower levels. High pressure at
upper levels will only suffer the passage of a trough to the south
Friday and Saturday that coincides with the tropical wave
passage. Bu this should be sufficient to bring showers and
scattered thunderstorms to Puerto Rico and the U.S. Virgin
Islands. Although temperatures will continue above normal, winds
will be more easterly than today or Tuesday and this should allow
some moderation from the highs expected for the first half of this
week. Although some haze from Saharan dust will continue, models
suggest that the passages of the tropical waves will bring back
some of the clearest air of several weeks Tuesday, Friday and
Saturday.

&&

.AVIATION...
(06Z TAFS)
Issued at 416 AM AST Mon Jul 31 2023

Light and passing SHRA expected before 18Z, with limited impacts to
operations, if any. An apchg trop wave will increase SHRA and
isolated TSRA aft 31/18Z for TISX, spreading northward into TIST
and TJSJ through 01/03Z, with additional activity also expected
for TJBQ from 31/18-22Z. Some interruptions to operations will be
possible due to low ceilings and reduced VIS. Winds will be from
the ESE at 13-15 kts, with stronger gusts.

&&

.MARINE...
Issued at 416 AM AST Mon Jul 31 2023

Generally tranquil seas will persist through the week. On Friday
and Saturday winds will increase and seas will rise-- especially
in our Atlantic waters. Small craft advisories may be necessary
by Saturday morning. At this time, after the moderate risk of rip
currents of northwest and north central Puerto Rico settles down
tonight the risk of rip currents will be low through Friday.



&&

.CLIMATE...
Issued at 416 AM AST Mon Jul 31 2023

Temperatures and relative humidities continue running well above
normal even though no records appear to be in jeopardy today. Heat
indices of up to 116 degrees are expected in parts of coastal
north central Puerto Rico with values over 108 degrees in most
lower elevations and urban areas of all but south Puerto Rico.
Despite the passage of a tropical wave, southeast to southerly
winds will also contribute to high heat indices along the north
coast for the rest of the week. &&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
535 AM AST Wed Aug 2 2023


.SYNOPSIS...
Issued at 456 AM AST Wed Aug 2 2023

A series of weak tropical waves will pass through the area during
the period. Each will bring increased showers and thunderstorms
followed by somewhat drier air. Saharan Dust is at a minimum, but
will increase beginning Sunday and Monday. Excessive heat will
remain problematic during the period especially today when winds
are more southeasterly.

&&

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

Some showers and thunderstorms were observed early across the Mona
Channel, and between the Virgin Islands in the overnight hours.
Culebra received a few nice showers as well, with radar estimates
just below one inch. Skies were mostly clear.

A low pressure system well north of the islands is keeping the
trade winds weak, resulting in light and variable winds across the
area. This low pressure connects with the tropical wave now
centered west of Haiti, and it is causing above normal moisture
across the northeastern Caribbean. Even with the abundant
moisture, plenty of sunshine is expected today, and that should
fuel afternoon convection across the area. Under such light winds,
the activity should begin along the Cordillera Central, but then
it will spread toward the coastal areas of Puerto Rico. It is
likely that some showers will also pop up across the Virgin
Islands, Vieques and Culebra. Since the showers are not expected
to be able to move too much, another couple of days with localized
urban and small stream flooding and isolated flash flooding will
be possible. Frequent lightning, mudslides and water surges along
rivers may also be observed.

As the low pressure moves north, the trade winds will recover on
Friday, coming out of the east at 10 to 15 knots, which is closer to
normal. At the same time, a well defined tropical wave will
approach the islands. Some Saharan dust will be embedded with the
wave, so a mix of hazy skies and passing showers can be anticipated.
The passage of the wave will then again combine with local effects
and result in another round of afternoon activity for the interior
and western Puerto Rico, and downwind from the Virgin Islands, and
from El Yunque into the San Juan metro area. Fortunately, faster
winds mean that the showers will not linger as long, but the risk
for urban and small stream flooding will be possible each day.

In terms of temperatures, 925 mb temperatures are expected to be well
above normal today...yet again. For the latter part of the workweek,
these values will not be as high, but still above normal, so
scorching hot temperatures and heat indices will just not go away.

&&

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

By Saturday the tropical wave that crossed the area on Friday
will be over Hispaniola, and somewhat drier and more stable air
will be found between that wave and the next which will enter the
Caribbean on Saturday night. The best moisture of this wave will
be narrow and move through our forecast area faster early
overnight Sunday into Monday. We also look for an increase in
thunderstorm activity as 500 mb temperatures cool over the area
through 07/12Z. At the same time winds at 850 mb will be from the
east northeast and will increase through Sunday as they veer to
east southeast. Moisture will again increase with precipitable
water values of 2.1 to 2.3 inches. Although drier air moves into
the area behind this wave also, the tail of the moisture that
will connect yet another wave will drag through the area late on
Tuesday afternoon. The third wave will move through on Wednesday.

Moisture across the area this weekend will be enough to generate
heavy rains and some urban and small stream flooding is expected
most afternoons in western and interior Puerto Rico.

Saharan dust will be at a minimum, though not entirely absent from
the area until Saturday, from there it will increase again on
Monday.

Lighter winds are found at upper levels with flow being quite
variable. A weak inverted trough will move through on Tuesday.

Surface winds on the other hand will also be light but generally
with a southerly component that will keep high heat indices over
the northern coastal areas of Puerto Rico.

&&

.AVIATION...
(06Z TAFS)
Issued at 456 AM AST Wed Aug 2 2023

VFR conditions expected bfr 02/18Z today. Then, SHRA and TSRA are
expected to develop along the Cordillera Central, spreading
toward the coastal areas. This could lead to periods of reduced
VIS and low ceilings along the terminals in Puerto Rico. For the
USVI, VCSH are also expected from 02/12-22Z, with some impacts to
operations possible. Winds will be light, mostly below 10 kts,
from the ESE, but with variations due to sea breezes and outflows
from TS. Maximum winds E 25-30 kts btwn FL300-320.

&&

.MARINE...
Issued at 456 AM AST Wed Aug 2 2023

Marine conditions will remain tranquil through today. Winds
associated with the passage of waves and weak surges behind them
will cause seas to rise beginning early Saturday. There is still a
good chance of small craft advisory conditions due to seas being
found in the local outer Atlantic waters Sunday into Monday. Seas
are expected to subside by Tuesday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Thu Aug 3 2023


.SYNOPSIS...
A surface trough and increasing moisture will bring shower and
thunderstorm activity today, particularly during the afternoon
hours. Friday, another tropical wave will reach the local islands.
Therefore, urban and small stream flooding can be expected
associated with these features, as well as localized flash
flooding and mudslides in areas of steep terrain.

&&

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

Minimum temperatures were from the mid 60s across the higher
elevations of Puerto Rico to the upper 70s and low 80s across the
coastal areas of the islands. Showers were increasing late in the
night under a weak northeasterly steering wind flow across the local
waters, with some reaching portions of the northern USVI and
northeastern PR, leaving minor rainfall accumulations. A slight
improvement in temperatures is expected today, however, the usual
urban areas in the lower elevations of the islands should see max
temps reaching the upper 80s to low 90s.

A surface trough currently moving between the Leeward Islands and
the Anegada Passage will cross the islands today. Winds have turned
from the east to northeast and are expected to continue mostly light
to locally moderate through late this afternoon, shifting the focus
of afternoon convection over the Cordillera and the southwestern
quadrant of PR. Meanwhile, as the trough axis moves over the
islands, winds will shift from the east to southeast first across
the USVI by this afternoon, and through the night across PR. This
will bring the bulk of moisture across the eastern and southern
sections of PR overnight. Therefore, expect shower and thunderstorm
activity to gradually increase across the islands and regional
waters during the next 12-24 hours. Urban and small stream flooding
can be expected with this activity, as well as localized flash
flooding and mudslides in areas of steep terrain. Following quickly
behind on Friday, a tropical wave is expected to reach the islands
by the peak of daytime heating. Enhancing the diurnal convection
cycle across the islands and maintain a wet pattern in general, with
an elevated flood threat once again. On Saturday, the moisture
content is expected to decrease as a drier air mass with Saharan
dust and returning trades promote typical afternoon convection,
mainly across western PR.

&&

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

Based on the most recent model guidance, the weather scenario
expected in the long-term forecast cycle remains unchanged, with the
following features influencing the local weather conditions; wind
surge on Sunday, followed by suspended Saharan dust particulates on
Monday, and a strong tropical wave between Wednesday and Thursday.
The first feature on Sunday will bring possible squally weather with
the potential of thunderstorms and gusty wind conditions across the
area. Precipitable water content is expected to increase to above
2.0 inches which could promote heavy rains in localized areas.
However, fast-moving storms will limit rainfall accumulations at the
surface.

Although the presence of Saharan dust by early next week may inhibit
somewhat shower development, enough moisture content will be present
for some shower activity each day, particularly during the afternoon
hours. Localized moderate to heavy rains could lead to ponding of
water on roadways and poorly drained areas, even during periods with
relatively drier air streaming across the region.

The vigorous and broader tropical wave reaching the islands by mid-
week of next week will promote wet weather conditions for the rest
of the long-term period. Dynamics aloft will also turn favorable
with 500 mb temperatures cooling to -7 degrees Celsius.
Therefore, weather conditions will be conducive to widespread deep
convective activity that could potentially lead to urban and
small stream flooding and isolated flash flooding events.

A high surface pressure meandering across the North Atlantic Ocean
will maintain a generally eastern southeasterly wind flow at 10-20
mph, but the above features will cause winds to vary briefly in
intensity and direction. Changes in the general wind flow will also
alter daytime maximum temperatures, but highs will still peak into
the upper 80s to around 90 degrees, with heat indices into the lower
to mid 100s each afternoon. Some low-lying and urban areas could
reach heat advisory criteria, particularly across the north-central
municipalities during the long-term period.



&&

.AVIATION...A surface trough will cross the region today. SCT-Bkn
lyrs nr FL022...FL050...FL100. MTN tops obscd this afternoon. SCT
SHRA/ISOLD TSRA expected between 03/18z-04/04z in and around the
USVI and PR terminals, tempo MVFR conds possible. Winds E-ENE at 8-
12 kts with higher gust near convective activity.

&&

.MARINE...
Gentle to moderate easterly winds will persist with seas remaining
at 4 feet or less. Winds are expected to increase tomorrow through
the weekend bringing choppy sea conditions across the regional
waters. An approaching surface trough and tropical wave will
promote shower and thunderstorm activity across the local waters
for the next couple of days. Therefore, localized hazardous
marine conditions can be expected close to the strongest
thunderstorm activity.

&&

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

$$

SHORT TERM/AVIATION...DSR
LONG TERM/MARINE....CVB
PUBLIC...RVT

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
514 AM AST Fri Aug 4 2023


.SYNOPSIS...
Showers and thunderstorms over the local waters will continue
through the morning hours with some affecting windward coastal
areas. Afternoon activity will concentrate across western portions
of Puerto Rico. A wetter and unstable weather pattern is expected
by mid-week of next week as a vigorous tropical wave approaches
the local islands. Urban and small stream flooding along with
flash flooding and mudslides can be expected during this period.
An increase in easterly winds will promote choppy to hazardous
marine conditions this weekend.

&&

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

A lingering trough over the area promoted shower and thunderstorm
activity through the night. Observed rainfall amounts were from a
quarter of an inch of rain in Vieques to just over an inch of rain
in Las Piedras. Lesser amounts were observed across the U.S. Virgin
Islands. Minimum temperatures were from the mid 60s across the
higher elevations of Puerto Rico to the upper 70s and low 80s across
the coastal areas of the islands.

Shower and thunderstorm activity will continue to spread westward,
and mainly across the Atlantic and Caribbean waters as a surface
trough exits the region later this morning. Meanwhile, a slot of
drier air is moving from the Anegada Passage into the USVI and
eastern PR, promoting fair weather conditions. However, increasing
trades and a tropical wave propagating across the Leeward Islands,
will bring scattered showers and isolated thunderstorms once again
through the afternoon and evening hours across the local waters and
over portions of the islands at times. In addition, diurnally
induced afternoon convection is expected over portions of eastern PR
and the northwestern quadrant of PR, where urban and small stream
flooding is possible. On Saturday, moisture content is expected to
decrease as an area of drier air with Saharan dust moves over the
region. Trade winds will continue to increase during the weekend as
a surface high pressure over the central Atlantic strengthens, and
another tropical wave moves through the area by Sunday. Therefore,
shower and thunderstorm activity will increase once again over land
areas on Sunday.

East to southeast trades should promote max temperatures in the low
90s across the islands, with heat indices ranging from 102-108
degrees Fahrenheit in general. Higher heat indices are possible
before the onset of afternoon convection today. On Saturday, a Heat
Advisory may be requires for the northern sections of PR, Culebra
and Vieques.

&&

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

Monday appears to be the driest day of the long-term period. Traces
of suspended Saharan dust particulates will be present, resulting in
hazy skies. However, a mid-to-upper weak shortwave trough will move
over the area and, in combination with near-normal to above-normal
moisture content, some shower and thunderstorm activity may develop,
mostly in the afternoon across western portions of Puerto Rico.

As we progress into the workweek, the weather pattern could turn
wetter as a vigorous tropical wave reaches the islands. Precipitable
water values are expected to climb above 2.0 inches, even reaching
close to 2.40 inches as indicated by the GFS model. Both ECMWF and
GFS Galvez-Davison Index indicate the potential for scattered to
widespread heavy rain-producing thunderstorms. First, southeasterly
trades will advect a plume of moisture on Tuesday concentrating the
bulk of the activity across the Caribbean waters. Sea breeze
convergence and streamer-like showers will also promote thunderstorm
activity across the northwestern quadrant of Puerto Rico, Cordillera
Central, and possibly over the San Juan metro area. Afterward, the
leading edge of the moisture field from the tropical wave will
approach the local islands by Wednesday with the wave axis over USVI
by late Wednesday evening. The peak of the activity is expected on
Thursday as the wave axis crosses Puerto Rico.

According to model guidance, the strongest activity is expected to
affect the USVI and eastern Puerto Rico on Thursday. However,
uncertainty exists as the positioning and strength of the tropical
wave could change in the coming days. Nevertheless, limited to
elevated flooding risk can be anticipated most days of next week,
particularly on Wednesday and Thursday. Urban and small stream
flooding, along with flash flooding and mudslides are possible as
the tropical wave moves over the forecast area. Please stay tuned
for further updates in the forecast.

&&

.AVIATION...VFR conditions expected thru 04/15z across all
terminals. Then, SHRA/TSRA increasing in and around the USVI
terminals due to an approaching tropical wave, and across western PR
due to the combination of a surface trough with local effects. This
should impact mainly TJBQ with tempo MVFR conds. Sfc winds E-ESE at
10-15 kt with higher gusts and sea breeze variations after 04/14z.

&&

.MARINE...
Winds are expected to increase through the weekend promoting
choppy to hazardous seas. For beachgoers, there is a low risk of
life- threatening rip currents across all beaches of Puerto Rico
and the U.S. Virgin Islands today. However, moderate risk is
expected for north- and east-facing beaches of all the local
islands this weekend.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
519 AM AST Sat Aug 5 2023

.SYNOPSIS...Moderate to fresh trades will continue through early
next week as surface high pressure strengthens over the central
Atlantic into the northeastern Caribbean. A series of tropical
waves and induced troughs will reach the islands through next
week. Hot and humid conditions should lead to heat indices ranging
from 106-111 degrees in general across the lower elevations of
north central PR, San Juan and vicinity, and across Vieques and
Culebra today.


&&

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

The eastern third of Puerto Rico and the smaller islands observed
isolated to scattered showers throughout the night. This was due to
a weak tropical wave interacting with the local islands. Some
isolated thunderstorms developed, but remained mostly over the
Caribbean waters. Meanwhile, mostly fair weather conditions with
clear to variably cloudy skies prevailed across the western portions
of Puerto Rico during overnight hours. As the weak tropical wave
continues moving westward, expect showers to continue affecting
eastern portions of Puerto Rico and USVI through the morning hours.

GOES-16 satellite data shows a dry slot behind the tropical wave
moving toward the forecast area. Precipitable water values
associated with this area are close to 1.5 inches, which is below
normal to near normal levels for this time of year. This dry slot is
expected to reach the local islands by late morning into early
afternoon decreasing cloud coverage and shower activity across the
region. Nevertheless, surface heating and sea breeze convergence
will promote shower and thunderstorm activity across the
northwestern quadrant of Puerto Rico this afternoon. Sky clearing
during peak hours of the day will raise surface temperatures
possibly reaching the low 90s across low-elevation and urban areas.
Heat index values will increase to above 108 Fahrenheit in some
areas. Therefore, a Heat Advisory is in effect for north-central
municipalities and the San Juan metropolitan area, along with
Vieques and Culebra.

Tonight and Sunday, another tropical wave will impact the local
islands. A low-level wind surge follows this tropical wave promoting
squally weather as the tropical wave crosses the area. Hi-res models
indicate shower activity increasing late tonight into early morning
hours with the eastern half of Puerto Rico, Vieques, Culebra, and
USVI observing the bulk of precipitation. Due to the fast-moving
nature of these showers, and possible isolated thunderstorms,
rainfall accumulations will be diminished. However, ponding of water
in roadways and low-lying areas can still be expected. In the
afternoon, shower and thunderstorm activity will cluster once again
across western/northwestern Puerto Rico, however, gusty wind
conditions could push convective activity offshore earlier than
usual. Suspended Saharan dust particulates will be present behind
the wave, therefore hazy skies will prevail in areas with little
shower activity.

Precipitable water values will remain at 2.0 inches or higher for
the remainder of the long-term forecast as a moist plume gets
advected towards the northeastern Caribbean. The 500 mb temperatures
will also slightly cool to -6 degrees Celsius, increasing mid-level
lapse rates and enhancing the potential for deep convective
activity. Therefore, wet and somewhat unstable weather conditions
will promote shower development in a seasonal pattern; first across
the eastern half of Puerto Rico and smaller islands during the
morning hours and later affecting interior and western portions of
Puerto Rico.


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

An upper-level low is forecast to move just north of the region
early next week, promoting instability aloft for diurnal
convection. As stated previously, the long term forecast is
expected to remain wet in general as induced troughs and active
tropical waves stream across the region from time to time.
The threat for flooding will be elevated, particularly on
Thursday(tropical wave) and Saturday(induced trough). For the rest
of the period, trade wind showers will move at times across the
USVI and eastern sections of PR during the nighttime, and in the
afternoon hours, thunderstorms are expected to develop each day
over portions of the interior and western PR. Meanwhile, east to
southeasterly trades and dewpoints in the low 80s will promote hot
and humid conditions, that could lead to heat indices meeting or
exceeding Heat Advisory criteria on Wednesday and Friday.


&&

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



&&

.MARINE...Choppy wind driven seas will continue to build up to 7
feet across the Atlantic waters and the Anegada Passage during the
next 24 hours or so, and a Small Craft Advisory is in effect for
these waters. Elsewhere, small craft should exercise caution.
There is a moderate risk of rip currents for the north and east
facing beaches of the islands.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 11 AM this morning to 4 PM AST this afternoon
for PRZ001-005-012-013.

VI...None.
AM...Small Craft Advisory from 2 AM Sunday to 2 PM AST Monday for
AMZ711.

Small Craft Advisory from 8 AM to 8 PM AST Sunday for AMZ723.

&&

$$

SHORT TERM...CVB
LONG TERM....DSR
AVIATION...CVB

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Sun Aug 6 2023

.SYNOPSIS...Moderate to fresh trades will continue through next
week as surface high pressure strengthens over the central
Atlantic into the northeastern Caribbean. Moisture content will
remain high through the first part of the week due to tropical
waves and induced troughs moving across the eastern Caribbean.
There will be some haze today due to the presence of Saharan dust
mixed in with a tropical wave. A moderate Saharan dust event is
expected by the end of the week.


&&

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

Isolated to scattered showers were observed across the northern and
eastern portions of Puerto Rico and lesser islands during the
overnight hours. A few isolated thunderstorms developed over the
local waters affecting St. Thomas, Culebra, and northeastern Puerto
Rico at times, but convection weakened as soon as it interacted with
land areas. A few spots received between half and an inch of rain,
but overall, rainfall accumulations were on the light side as
showers were moving fairly quickly. This activity was related to the
proximity of another weak tropical wave with an axis currently
located over the Leeward Islands. As the weak tropical wave
continues moving westward, expect showers to continue affecting
eastern portions of Puerto Rico and USVI through the morning hours.

According to the Tropical Analysis and Forecast Branch, the axis of
the tropical wave will be located over the USVI and Hispaniola by
06/12z and 07/00z, respectively. Therefore, expect variable weather
conditions today across the local islands as the tropical wave
crosses the area. Afternoon convection will impact the interior and
western/northwestern portions of Puerto Rico. As mentioned in
previous discussions, a low-level wind surge behind the wave will
promote gusty wind conditions today. For that reason, shower and
thunderstorm activity will move fairly quickly inhibiting somewhat
rainfall accumulations across the islands. Nevertheless, reduced
visibility while driving, ponding of water in roadways, and poor
drainage areas can still be expected with the heaviest showers.
Urban and small stream flooding is still possible across western
municipalities during the afternoon hours. Suspended Saharan dust
particulates will also be present today promoting hazy skies in
areas with limited shower activity.

From Monday onwards, a wet weather pattern will prevail across the
forecast area with precipitable water remaining at or above 2.0
inches. First, by early Monday, a trade wind perturbation will cross
the area and bring another patch of low-level moisture across the
region along with more frequent passing showers. This additional
moisture should promote a better chance for scattered afternoon
convection mainly over parts of the Cordillera Central and western
sections of Puerto Rico. Streamers downwind of El Yunque affecting
the San Juan metro cannot be ruled out.

By Tuesday and following the passage of the aforementioned
perturbation, winds are to become more east-southeast and
consequently favor a gradual increase in low-level moisture
convergence as well as even warmer temperatures along the north
coastal areas. This will also favor a better chance for early
morning passing showers along the east-southeast coastal area
followed by afternoon convection mainly over the northwest quadrant
of Puerto Rico, and downwind of the U.S. Virgin Islands. By late
afternoon, the leading edge of a tropical wave will begin to affect
USVI and eastern Puerto Rico promoting scattered to numerous showers
and isolated thunderstorms for the rest of the long-term period.
Urban and small stream flooding, localized flash flooding as well as
ponding of water on roads in poor drainage areas are possible each
day as a wet weather pattern settles over the local islands this
week.

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

At least through Thursday, the precipitable water content is
expected to remain above normal levels(between 2.00-2.40 inches).
This is in response to a tropical wave crossing the islands on
Wednesday, followed by a stronger tropical wave on Thursday.
However, the second wave may encounter strong trades with a
Saharan Air Layer, causing the wave to pass mainly south of the
islands. Thereafter, hazy and breezy conditions could prevail
through Saturday, before a TUTT induced trough moves over the
northeastern Caribbean on Sunday. Having said that, expect a wet
pattern to continue early in the long term period, with scattered
to locally numerous showers and isolated thunderstorms across PR
and the USVI, and a drying trend into the weekend. Currently, the
NHC is not expecting TC formation from these tropical waves.


&&

.AVIATION...Mainly VFR cond expected to persist through the forecast
period. HZ from Saharan dust will be present, but VIS are expected
to remain P6SM. VCTS is expected across TJSJ/TIST thru 06/10z. VCTS
is also expected after 06/15Z for TJSJ/TJBQ/TJPS with brief periods
of low ceilings possible as a tropical wave crosses the area today.
Winds will be out of the east at 15 to 20 knots, with stronger gusts
due to sea breezes. Winds are expected to slow down after 06/22Z,
but will remain close to 10 knots for all terminals.


&&

.MARINE...A tropical wave and a surface high pressure over the
central Atlantic will continue to promote choppy wind driven seas
up to 7 feet across the Atlantic waters and the Anegada Passage
through at least Monday. Therefore, a Small Craft Advisory is in
effect for these waters. Elsewhere, small craft should exercise
caution due to the moderate to fresh trades and seas between 4 and
6 feet. There is a moderate risk of rip currents for the north
and east facing beaches of the islands.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
425 AM AST Mon Aug 7 2023


.SYNOPSIS...
Moderate to fresh trades will continue as a surface high pressure
strengthens over the central Atlantic into the northeastern
Caribbean. Moisture content will remain high through the first
part of the week due to tropical waves and induced troughs moving
across the eastern Caribbean. The tropical wave will continue to
move out of the area tonight, but residual moisture is still
expected through Monday. A moderate Saharan dust event is expected
by the end of the week.

&&

.SHORT TERM...Tonight through Wednesday...
Shower and thunderstorm activity prevailed across the Atlantic
waters and Anegada passage throughout the night. The Geostationary
Lightning Mapper showed some areas with frequent lightning across
the local waters, with strong outflows between 30 to 35 knots
detected by the Doppler radar. This area of unsettled weather
conditions is produced by a trade wind perturbation crossing the
islands. Hi-Res models suggest shower and thunderstorm activity to
continue across the waters for the rest of the morning hours, with
convection intensity pulsating throughout the period. Some of this
activity will affect the USVI, Vieques, Culebra, and the eastern
third of Puerto Rico. In the afternoon, expect low-level moisture
interacting with the topographic features of the islands, promoting
deep convective activity across the interior and western portions of
Puerto Rico. Streamers downwind of the lesser islands are also
possible.

Above-normal moisture content is expected to prevail across the area
for the rest of the short-term period. The trade wind perturbation
will persist through early Tuesday with a tropical wave, currently
located at 51W, crossing the area by late Tuesday through Wednesday.
The GFS suggests precipitable water content remaining above 2.00
inches and increasing to 2.40 inches at times through Wednesday
evening. The dynamics above will also be conducive for convective
activity as a series of weak retrogressing TUTTs move over the local
islands on Tuesday through Wednesday.

Overall, expect the same weather pattern each day with the potential
of scattered to numerous showers and isolated to scattered
thunderstorms across the forecast area. In terms of rainfall
accumulations through Wednesday night, model guidance suggests the
eastern third of Puerto Rico, Vieques, and Culebra receiving most of
the precipitation during night and morning hours, with western
interior and western municipalities of Puerto Rico receiving the
other bulk of precipitation during the afternoon hours. Urban and
small stream flooding along with ponding of water roadways and in
poor drainage areas can be expected with the heaviest showers.
Localized flash flooding and mudslides in steep terrains cannot be
ruled out.

&&

.LONG TERM...Thursday through Monday... Anticipate higher levels
of moisture and winds as a tropical wave progresses south of
Puerto Rico.This transition is expected to occur from Thursday
night through Friday. The increased moisture will persist in the
area until at least Sunday. This elevated moisture, along with the
influence of local diurnal effects, will contribute to the
formation of afternoon showers and thunderstorms , mainly
concentrated over the the interior and western parts of Puerto
Rico.

It's advisable to closely observe the evolution of the tropical wave
due to o indications from global models pointing towards a notable
rise in winds associated to this weather feature between Thursday
and Friday. The GFS model are suggesting sustained winds ranging
from 30 to 35 mph mainly over the local Caribbean waters.
In the official forecast, we limit the wind speeds to 25 mph due to
the high uncertainty in the forecast.

&&

.AVIATION...SHRA will move across the local terminals today, some of
them will affect TJSJ/TIST/TISX at times. Afternoon SHRA/TSRA are
expected across the Cordillera Central and the SJ-Metro Area, as
well as downwind from the USVI. This activity could impact TJSJ/TJBQ
between 07/16-22z, and may result in MVFR conditions. Expect light
and VRB winds thru 07/13z, when will return from the E at 12-20kt
with sea breeze variations and gusty near TSRA/+SHRA.

&&

.MARINE...The tropical wave maintains its westward movement,
distancing itself from the nearby waters. The high pressure
system in the central Atlantic will persist in creating choppy
seas generated by winds across the local water. Anticipate
a gradual wind reduction and subsequently slightly calmer seas
over the next day or so, as the pressure gradient eases. Thursday
is anticipated to bring another episode of rough seas, affecting
the nearby waters, as a more robust tropical wave is forecast to
move across the local forecast waters.

Small craft should exercise caution across most local waters due
to choppy to hazardous marine conditions generated by increasing
winds of 15-20 knots. This increase in winds will yield seas up to
7 feet across the off shore Atlantic waters, where a Small Craft
Advisory is in effect.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
416 AM AST Tue Aug 8 2023


.SYNOPSIS...
Moderate to fresh trades will continue as a surface high pressure
strengthens over the central Atlantic into the northeastern
Caribbean. Moisture content will remain high through the first
part of the week due to tropical waves and induced troughs moving
across the eastern Caribbean.

&&

.SHORT TERM...Tonight through Wednesday...
The proximity of an upper-level trough combined with warmer waters
and the above-to-normal water content resulted in scattered to
numerous showers across the local waters, some of them moving into
the U.S. Virgin Islands and the windward sections of Puerto Rico
overnight. The unstable pattern also promoted scattered
thunderstorms across the Atlantic Waters. Low temperatures remain in
the upper 70s and low 80s across the lower elevations and the low
and mid-70s in the mountain areas, while the winds were mainly from
the east but under the influence of the land breeze.

The subsidence ahead of today's tropical wave will somewhat limit
rain activity around sunrise and early morning, especially across
the Virgin Islands and Puerto Rico windward sections. However, as
the wave approaches, there will be more frequent and intense showers
and thunderstorms by mid-morning to afternoon, leading to unsettled
weather conditions. Although before the beginning of the inclement
weather this afternoon, the combination of the abundant moisture and
the air temperature will result in heat index values between 100 and
107 degrees Fahrenheit. Periods of moderate to locally heavy
rainfall will maintain an elevated risk of urban and small stream
flooding across Puerto Rico and the U.S. Virgin Islands today.
Mudslides along steep terrains and flash flooding will be possible
if widespread activity materializes. Thunderstorms will develop
(especially during the afternoon), so please remember, "When Thunder
Roars, Go Indoors!"

The unstable weather pattern with above-normal moisture will persist
through at least Wednesday. However, the east-southeast winds will
promote warm to hot temperatures Wednesday morning across the urban
and coastal locations, followed by strong afternoon convection
across the northwest PR and near the San Juan Metropolitan Area. The
U.S. Virgin Islands may observe occasional squally weather,
resulting in gusty winds and frequent lightning.

Another tropical wave will arrive around Thursday afternoon or
during the evening, extending the wet and unstable weather pattern
for the islands. However, subsidence ahead of the wave will bring
occasional relief from the rain activity, but the near to above-
normal moisture combined with the maximum temperatures will promote
warm and hot weather before the beginning of the rain activity on
Thursday.

&&

.LONG TERM...Friday through Tuesday...
On Thursday, even as the tropical wave will continue to westward
and out of our local area the moisture associated to this
phenomenon will persist over the local region throughout the
weekend. On Saturday, a mid to upper level trough will extend
southward, increasing the instability across the area at least
until Sunday. Therefore expect showers and thunderstorms to
develop each afternoon over the interior and western portions of
Puerto Rico. Passing showers will affect the eastern sections of
Puerto Rico and the U.S. Virgin Island during the overnight and
morning hours. Between Monday and Tuesday a more stable and less
humid air mass will dominate the region.

Global models have scale back their forecast regarding the
strength of the winds associated to the tropical wave expected
between late thursday and Friday. Nevertheless, there is still an
anticipation of breezy conditions, particularly over the
Caribbean waters.

&&

.AVIATION...A tropical wave will bring SHRA/TSRA across the local flying area.
Periods of VFR conditions are expected, but TSRA will develop by
mid-morning into the afternoon (especially between 08/15-22z).
TSRA will bring gusty winds and frequent clouds to ground lighting.
Local winds will persist from the east, with land breeze variations
until 08/13z. Then, the easterlies will range between 10 and 15 kt
but locally higher in/near SHRA/TSRA and with sea breeze
variations.

&&

.MARINE...mariners should exercise caution across the off shore
Atlantic waters due to seas. Also strong thunderstorms and heavy
showers had been affecting the Atlantic waters throughout the
overnight hours. Seas will be below the 5 feet elsewhere and winds
between 10 to 15 knots.

Mariners should closely observe the evolution of the tropical wave
expected to move across the local waters between Thursday and Friday.
A notable rise in winds associated to this weather feature is forecast
during this period with the GFS model suggesting sustained winds of
around 25 knots.


&&

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

$$

SHORT TERM...CAM
LONG TERM....EM
AVIATION...CAM

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
431 AM AST Wed Aug 9 2023

.SYNOPSIS...
Throughout the remainder of the week, moisture levels will remain
elevated across the local area. Moderate to fresh trade winds
will persist due to a surface high pressure situated north of the
region, interacting with tropical waves passing over the local
waters. The upcoming tropical wave is forecast to move across the
the local forecast area between Thursday and Friday.

&&

.SHORT TERM...TODAY THROUGH FRIDAY...

The abundant trailing moisture of the tropical wave brought
widespread shower activity across the local waters overnight,
spreading across the islands of St Thomas, St John, and St Croix, as
well as across the windward sections of Puerto Rico. The Doppler
Radar detected periods of moderate to locally heavy rains with this
activity. GOES-E observed isolated thunderstorms across the local
waters too. Low temperatures remain in the upper 70s and low 80s
across the lower elevations and the low and mid-70s in the mountain
areas, while the winds were mainly from the east but under the
influence of the land breeze.

GFS suggested the advection of vorticity into the region later this
morning into the afternoon may result in favorable atmospheric
conditions for another rainy day. The trailing moisture of
yesterday's tropical wave will bring another rainy day today,
combined with vorticity advection, excessive heat, local effects,
and sea breezes, resulting in enhanced convection periods across
most islands. Rain activity will begin across the local waters, the
U.S. Virgin Islands, and windward sections of Puerto Rico during the
morning, spreading into the rest of Puerto Rico late this morning
into the afternoon. Although rainy conditions are likely today, warm
to hot temperatures (with HI up to 107 degrees Fahrenheit or even
more) due to the combination of air temperatures and abundant
moisture will happen across the urban and coastal areas where rain
does not form.

Most islands have an elevated risk of urban and small stream
flooding today. Mudslides along steep terrains and flash flooding
will be possible if widespread activity materializes. The atmosphere
is also favorable for the formation of thunderstorms, so please
remember to avoid outdoor activities if you can hear them.

Although there is a high chance of rain forecasted, it is expected
to clear out of the U.S. Virgin Islands by late morning. This will
create favorable conditions for the heat index to reach 108-111
degrees Fahrenheit, particularly between 11 am and 5 pm. As a
result, a Heat Advisory is currently in effect for St. Thomas, St.
John, and St. Croix.

There is going to be another tropical wave arriving on Thursday
afternoon that will bring wet and unstable weather to the islands.
However, there will be some relief from the rain activity due to
subsidence before the wave bulk of moisture. Despite this, the
moisture levels will remain above average, and combined with high
temperatures, it will promote warm and hot weather. Additionally,
the African Easterly Jet will cause the wind to increase during the
arrival of this tropical wave.

A somewhat drier air mass will set over the islands by Friday,
resulting in periods of sunshine and heat index values between 102-
111 degrees Fahrenheit. The typical August weather pattern consists
of the morning passing showers across the windward sections in
USVI/PR and strong afternoon convection across western PR. Heat
Advisories and Excessive Heat Warning may be required during the
afternoon.

&&

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

Even though there is a slight anticipated decrease in moisture
during Friday, there will still be sufficient moisture present to
trigger showers and thunderstorms across the interior and western
areas of Puerto Rico.

Saturday will see a mid to upper lever trough moving southward,
enhancing the instability in the local area until Sunday. In the
morning, anticipate passing showers than will mainly affect the
northeast portions of Puerto Rico and the U.S. Virgin Islands.
later in the late morning and early afternoon , showers and
thunderstorms will begin to develop and impact the western ,
interior and southwest areas of Puerto Rico. These weather
conditions might persist into the evening due to the continued
movement of the mid to upper level trough across the region,
sustaining and unstable environment throughout this period.

According to the GFS model, there is and indication of steep lapse
rates and colder temperatures than usual at the 500 mb level. the
primarily constraint, however, will be the availability of
moisture.Despite this, there is a potential for strong
thunderstorms on Saturday.

Sunday is anticipated to be a transitional day, with weather
conditions contingent upon the trough's location and moisture
availability. It won't be until Monday when a considerably drier
and more stable airmass arrives to the local region. This dry
weather pattern is forecast to persist at least until Wednesday of
the upcoming week.

&&

.AVIATION...The tropical wave will bring another round with SHRA/TSRA
across the local flying area. IST/ISX may be impacted thru 09/16z.
Periods of VFR conditions are expected, but TSRA will develop by mid-
morning into the afternoon (especially between 09/15-22z). TSRA will
bring gusty winds and frequent clouds to ground lighting. Expect
winds from the E-ESE, with land breeze variations until 09/13z. Then,
they will range between 10 and 15 kt but locally higher in/near SHRA/TSRA
and with sea breeze variations.

&&

.MARINE...Latest observation from CariCOOS buoys indicate seas
between 3 to 5 ft around the islands, with the exception of the
Rincon buoy, which indicates 1.6 ft and the Ponce Buoy indicating
2.3 ft. Small Craft Should Exercise Caution over the offshore
Atlantic waters with seas up to 6 ft. Other seas up to 5 ft.

Additionally, showers and isolated thunderstorms moving over the
waters can promote locally higher seas and winds with frequent
lighting.

Consistent across all global models is the forecast of noteworthy
rise in local winds from Thursday and Friday. This wind increase
is associated to the anticipated tropical wave during this period.
As a result, anticipate breezy conditions across all local waters,
especially in the Caribbean waters and Anegada Passage. Therefore
a Small Craft Advisory will be in effect between Thursday
Afternoon and Friday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
429 AM AST Thu Aug 10 2023



.SYNOPSIS...
Unstable weather conditions will prevail for the rest of the
afternoon and evening hours. Throughout the remainder of the week,
moisture levels will remain elevated across the local area.
Moderate to fresh trade winds will persist due to a surface high
pressure situated north of the region, interacting with a tropical
waves passing over the local waters. The upcoming tropical wave
is forecast to move across the the local forecast area between
later today and Friday.


&&

.SHORT TERM...
The tropical wave caused showers and thunderstorms across local
waters, the US Virgin Islands, and the eastern half of Puerto Rico
overnight. The Doppler radar recorded up to 2 inches of rain in
Salinas and around an inch in the rest of Southeast Puerto Rico. Low
temperatures persist in the upper 70s and low 80s across lower
elevations and low to mid-70s in mountain areas, while winds are
predominantly from the east-southeast with strong gusts near
thunderstorms and showers.

GOES-E derived TPW showed above-normal moisture of 2-2.5 inches with
the tropical wave. GFS predicts vorticity advection into the region,
potentially causing squally weather this afternoon. The abundant
moisture, vorticity advection, excessive heat, local effects, and
sea breezes will enhance afternoon convection across most islands.
Rain activity will begin across local waters, the US Virgin Islands,
and windward sections of Puerto Rico in the morning, spreading into
the rest of Puerto Rico in the afternoon. Today, most islands face a
high risk of flooding from urban areas and small streams. If
widespread activity occurs, mudslides may occur along steep terrain
and flash flooding. The region will be affected by scattered
thunderstorms, so it's best to avoid outdoor activities if you hear
them.

Although rainy conditions are likely today, warm to hot temperatures
(with HI up to 107 degrees Fahrenheit or even more) due to the
combination of air temperatures and abundant moisture will happen
across the urban and coastal areas where rain does not form. The
heat index values in the US Virgin Islands and Culebra will reach or
exceed values above 112 degrees Fahrenheit for a prolonged time,
particularly between 11 am and 5 pm. As a result, an Excessive Heat
Warning is currently in effect for them.

A somewhat drier air mass will set over the islands by Friday,
resulting in periods of sunshine and heat index values between 102-
111 degrees Fahrenheit or more. The typical August weather pattern
consists of the morning passing showers across the windward sections
in USVI/PR and strong afternoon convection across western PR. Heat
Advisories and/or Excessive Heat Warning may be required during the
afternoon.

A retrogressive TUTT will approach the Northeast Caribbean from the
northeast, creating unstable weather conditions from late Friday
night or early Saturday morning. Then conditions will improve
somewhat early Saturday morning. However, the excessive heat and
diurnal effects will again result in afternoon convection across
Puerto Rico. The US Virgin Islands may continue with the warm spell.
&&

.LONG TERM...Sunday through Thursday...
Expect passing showers affecting the U.S. Virgin Islands and
eastern portions of Puerto rico during the Sunday morning hours.
While Sunday marks the start of a transition towards drier and a
more stable weather pattern, is forecast the development of showers
and thunderstorms mainly in the afternoon over the Cordillera
Central and western portions of Puerto Rico.

Anticipate a noteworthy shift in the weather pattern across the
local area beginning Monday. Consequently, from Monday to
Thursday, there will be limited shower activity and coverage.
Expect hot and hazy conditions to dominate the incoming week over
Puerto Rico and the U.S. Virgin Islands.

With most schools in Puerto Rico set to commence classes next week,
it's important for the school administration to factor in the hot
and hazy weather forecast. This will enable them to implement
essential measures to safeguard student's health and address any
special needs.

&&

.AVIATION...
The tropical wave will bring rounds with SHRA/TSRA across the local
flying area. Periods of VFR conditions are expected, but TSRA will
spread by mid-morning into the afternoon (especially between 10/15-
22z), bringing gusty winds and frequent clouds to ground lighting.
Expect winds from the E-ESE, with land breeze variations until
10/13z. Then, they will range between 10 and 15 kt but locally
higher in/near SHRA/TSRA and with sea breeze variations.

&&

.MARINE...Although the increase in wind speed won't be as strong as
previously forecasted, they will be strong enough to generate choppy
seas mainly across the Caribbean local waters. The previous wind
forecast kept them around 25 knots, and in the recent model
runs,they have been lowered to around 20 knots. Seas will remain
below the 7 feet through Friday. Therefore, the small craft
advisory has been canceled. Nevertheless, small craft operators
should exercise caution across mainly the Caribbean local waters.

The conditions of wind driven seas will persist over the upcoming
days. On Saturday afternoon, a small long-period swell will enter
the local Atlantic waters. This northward swell will reach the
highest height of approximately 1.5 feet on Sunday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Fri Aug 11 2023

.SYNOPSIS...The local weather conditions will continue to dry out
today, and despite some increase in moisture levels during the
weekend, it will dry out again by the following workweek. Still,
overnight and early morning passing shower activity over eastern
Puerto Rico and the U.S. Virgin Islands are likely, followed by
afternoon showers with isolated thunderstorm development, even
during the driest day. While excessive rainfall risk levels will
decline, excessive heat hazard risks will pose a higher threat in
the expected weather scenario.


&&

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

A drier air mass with suspended dust particles produces hazy skies
and limits rain activity across the region overnight. A few showers
developed mainly due to cool air advection over warmer waters. Low
temperatures persist in the upper 70s and low 80s across lower
elevations and low to mid-70s in mountain areas, while winds are
predominantly from the east with land breeze variations.

The easterly winds are pushing a drier air mass, and the Total
Precipitable Water (PTW) derived from the GOES-E showed below-normal
moisture (between 1.5 and 1.37 inches of water). NASA aerosol
optical thickness (AOT) suggests hazy skies today and will last
throughout the day. Warmer than normal temperatures will also
persist across most urban and coastal areas, with heat index values
greater than 107 degrees Fahrenheit. Therefore, today we issued an
Excessive Heat Warning for the US Virgin Islands, Vieques, Culebra,
North Central, Northwest, and West Puerto Rico. The rest of the
coastal and urban areas of Puerto Rico had a Heat Advisory in
effect. Rain activity will be confined across the western sections
during the afternoon, mainly due to the available moisture, local
topography, excessive heat, sea breeze, and dust particles, which
may result in one or two strong thunderstorms.

A TUTT will retrogress from the Atlantic Ocean into the Northeast
Caribbean today, reaching the islands late tonight into Saturday.
This system may result in some thunderstorms late tonight and early
Saturday, mainly across the surrounding waters of the Virgin Islands
and northeast PR, as the GFS Galvez-Davison Index (GDI) suggests.
Afternoon convection will also be expected for the southwest
quadrant of Puerto Rico. Regardless of not anticipating widespread
significant rainfall amounts, we cannot rule out some strong
thunderstorms.

The typical August weather pattern with morning passing showers
across the windward sections in USVI/PR and strong afternoon
convection across northwest PR is possible for Sunday. Heat
Advisories and/or Excessive Heat Warning may be required during the
afternoon. Traces of Saharan dust particles will prevail during the
weekend too.

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

After the passage of a weak tropical wave early next week, expect
the local weather conditions to gradually dry out, with
precipitable water vapor values falling to two standard deviations
and below-normal climatological levels around 1.3-1.5 inches by
midweek. Still, the occasional shallow patch of moisture and
sufficient lingering moisture will support passing shower
activity moving into windward areas from the waters, followed by
afternoon showers with isolated thunderstorm development, even
during the driest day. While excessive rainfall hazard risks will
decline during the first half of the workweek, excessive heat will
present a higher threat level, with heat index values of 108
degrees or higher yielding heat-related illness with prolonged
exposure.

The latter part of the workweek, and the wettest period in the
forecast, presents the chance for significant rains and the
potential for excessive rainfall hazard risks as increased
tropical moisture steered by a robust tropical wave spreads across
the region. Confidence levels in this wet scenario are low,
particularly on potential impacts, due to its timing in the
forecast. Yet, increased tropical wave activity is likely during
this time of the year.


&&

.AVIATION...Expect VFR conditions across the local flying area. A
Saharan Air Layer will create hazy skies with P6SM. Some
+SHRA/+TSRA could develop across western PR between 8/17-22z and
may affect the VCTY of JBQ. Winds will prevail calm to light and
VRB overnight, but at 10-15 with gusts around 20-30 kt and sea
breeze variations.


&&

.MARINE...Recent CariCOOS buoy network observations around Puerto
Rico and the U.S. Virgin Islands indicated steady seas between 1
and 4 feet. Across the local waters, seas should remain 5 feet or
below and favorable for small craft during the next few days.
However, small craft operators should exercise caution across
coastal waters, local passages, and offshore Caribbean waters due
to locally wind-driven choppy seas. Increased trade winds will
yield choppy seas by Sunday into early next week. There is a
moderate rip current risk for most north-facing beaches of Puerto
Rico and the easternmost beaches of Vieques, Culebra, and Saint
Croix.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
408 AM AST Sat Aug 12 2023


.SYNOPSIS...

Patches of moisture will continue to move across the area
today and Sunday increasing the chance for rain. Breezy
conditions will keep enhancing choppy seas at times. Saharan Dust
remains present, but will reduce in concentration by Monday when
a thick layer arrives.

&&

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

Today's hazard risks focus on excessive rainfall at limited to
elevated and Wind and lightning at limited threat levels. Despite
the expected rains, expect excessive heat hazard risks each day.

Fair weather conditions, hazy skies, and limited shower activity
prevailed in the evening. After midnight, radar and satellite
imagery indicated an increase in shower with thunderstorm activity
across the waters, with some moving over northern and eastern Puerto
Rico and the U.S. Virgin Islands. So far, rainfall totals have
peaked around half an inch over northeastern Puerto Rico. Overnight
low temperatures fell to around 70 degrees across higher elevations
of the interior and lower 80s across lower elevations. Winds were
generally light from the east-northeast but calm and variable
further inland.

Surface high pressure over the North Atlantic will maintain breezy
to windy conditions, with peak 15-25 mph winds veering from the east
today and east-southeast on Sunday and Monday. Steered by this
general wind flow, moderate to high moisture airmass, spreading
across the region from the east, will gradually replace a drier
airmass and Saharan Air Layer that dominated the area in recent
days. Precipitable Water (PWAT) values will likely rise to one
standard deviation or into the above climatological thresholds
around 2.0 inches later this afternoon, as suggested by satellite-
derived Total PWAT and the most recent model guidance, and hold
within normal moisture levels at 1.7-1.9 inches throughout the
period. As this transition materializes, reduced visibilities are
still possible, mainly across rain-free areas today.

Adding to the already moist environment, a retrograding TUTT will
continue to move westward over the northeastern Caribbean region
today, increasing instability and setting the perfect environmental
conditions to support scattered to numerous showers with isolated to
scattered thunderstorm development. Over the local waters, this
activity will decrease but persist throughout the day. In contrast,
the focus of the rain activity shifts over land areas, aided by
local effects and diurnal heating, with the most vigorous activity,
steered by easterly winds, clustering across the interior to western
sections of Puerto Rico, where moderate to heavy rains will likely
lead to elevated excessive rainfall hazard risks. Elsewhere, showers
with isolated thunderstorms are possible, mainly downwind from El
Yunque into the San Juan metropolitan area. As a result, weekend
outdoor activities could be affected, primarily by potential
flooding impacts, including rapid rises along small streams and main
rivers, thunderstorm winds, and increased lightning activity.

A similar weather pattern is likely on Sunday but with more
localized and lesser showers and thunderstorms favoring more
northern sections of the local islands steered by east-southeast
winds. A more patchy weather scenario is likely on Monday, with more
frequent patches of relatively drier air supporting fairer weather
conditions, which presents an excellent start to the work and school
week. Southeasterly winds and a lower chance of precipitation will
lead to higher excessive heat hazard risk levels, with heat index
values likely to exceed 108 degrees across most lower elevations and
urban areas.

&&

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

The inherited forecast remains unchanged. At this time, precipitable
water models suggest PW values falling below normal climatological
levels through mid-week. Precipitable water content is expected
to remain around 1.30 to 1.60 inches. Nonetheless, patches of
moisture will still filter across the area from time to time,
allowing some occasional passing showers from the waters to move
into the windward sections of Puerto Rico and the U.S. Virgin
Islands. This activity will be followed by afternoon showers and
thunderstorm development, mainly across the western- southwestern
quadrant of Puerto Rico, even during the driest day. During the
first half of the workweek, excessive heat threat is anticipated,
with heat index values of 108 degrees or higher. Therefore, heat-
related illnesses with prolonged exposure are foreseen.

The latest model guidance suggests wetter conditions across the
islands by the latter part of the workweek. This increase in
tropical moisture and precipitable water content will be due to a
robust tropical wave spreading across the forecast area.
Therefore, the potential for excessive rainfall threats increases.
As mentioned in previous discussions, the confidence levels on
this wet scenario are low, particularly with potential impacts,
due to its timing in the forecast. However, increased tropical
wave activity is likely during this time of the year.

&&

.AVIATION...TSRA/SHRA could result in brief MVFR conditions across
TJSJ and USVI terminals through 12/13Z and after 12/22Z. Between
12/13-22Z, TSRA/SHRA could also bring similar conditions across most
terminals, with the highest impact on operations at TJSJ and TJBQ
between 12/16-22Z. Winds will remain light from the east with land
breeze variations, gradually increasing to 15-20 knots with higher
gusts and sea breeze variations by 12/14-20Z. Winds will become
lighter after 12/22Z.

&&

.MARINE...Latest CariCOOS coastal buoys indicated seas around 3
feet. Today, expect an increase in moisture, as well as, seas and
winds increasing slightly. There is a low risk of rip currents
for all the coastal beaches of PR and moderate over Ct. Croix.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
for PRZ012-013.

VI...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
for VIZ001-002.

[cycloneye]

WDPN32 PGTW 130900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 05E (DORA) WARNING NR
052//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
INITIAL POSITION: 18.3N 174.2E
INITIAL INTENSITY: 55 KTS
GEOGRAPHIC REFERENCE: 937 NM WEST OF JOHNSTON ISLAND
MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS
SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) THAT IS BECOMING MORE
EXPOSED BY THE MINUTE DUE TO THE PERSISTENT SOUTHWESTERLY SHEAR. A
130605Z SSMIS 91GHZ MICROWAVE IMAGE REVEALS A SMALL NAKED
CIRCULATION WITH A SMALL BLOOM OF CONVECTION EVIDENT TO THE
NORTHEAST OF THE LLCC. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON MSI AND SSMIS IMAGERY. THE INITIAL INTENSITY OF
55 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON PGTW AND KNES
DVORAK INTENSITY ESTIMATES TOGETHER WITH CIMSS AIDT INDICATING
55KTS, WHILE CIMSS ADT AND D-PRINT INDICATE SLIGHTLY HIGHER AT 63
KTS AND 67KTS RESPECTIVELY.

INITIAL WIND RADII BASIS: PERSISTENCE

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T4.0 - 65 KTS
RJTD: T4.5 - 77 KTS
KNES: T3.5 - 55 KTS
CIMSS ADT: 67 KTS AT 130530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
VWS: 15-20 KTS
SST: 28-29 CELSIUS
OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
INITIAL INTENSITY: MEDIUM
INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TROPICAL STORM DORA (05E) IS FORECAST TO
CONTINUE WEST-NORTHWESTWARD OVER THE NEXT 24 HOURS. DURING THIS
TIME, PERSISTENT SOUTHWESTERLY SHEAR WILL CONTINUE TO EAT AWAY AT
THE SYSTEM, RESULTING IN GRADUAL WEAKENING. AS THE SYSTEM CROSSES
THE 20TH PARALLEL, 05E WILL BE FORCED BETWEEN THE CURRENT STR AND A
NEW RIDGE THAT BUILDS TO THE NORTHWEST, THIS COMBINED STEERING
EFFECT WILL FORCE THE SYSTEM GENERALLY POLEWARD. THE INTENSITY OF
THE SYSTEM AFTER TAU 36 IS ENTIRELY DEPENDENT ON ITS TRACK. IF THE
SYSTEM IS ABLE TO WITHSTAND THE CURRENT VERTICAL WIND SHEAR AND
ENTER THE NORTHWARD TURN WITH A MAJORITY OF ITS STRENGTH, 05E WILL
TREND ON A MORE EASTWARD COURSE AS SEEN IN GFS AND NVGM. THIS
INSIDE TRACK WOULD BRING DORA INTO A REGION OF LOWER VERTICAL WIND
SHEAR AND THE UP-SHEAR ENVIRONMENT WOULD MOISTEN, FACILITATING A
PERIOD OF REINTENSIFICATION. ON THE OTHER HAND, THERE REMAINS A
CHANCE THAT DORA DISSIPATES BEFORE THIS OPPORTUNITY TO REINTENSIFY,
AS SHOWN BY THE ECMWF AND HWRF. THE JTWC OUTLOOK CONTINUES TO LEAN
TOWARDS A MORE RIGHT OF TRACK APPROACH WITH A MARGINAL AMOUNT OF
REINTENSIFICATION. AS THE SYSTEM PROGRESSES INTO THE HIGHER
LATITUDES, IT WILL BEGIN TO INTERACT WITH STRONG BAROCLINIC FORCES
THAT WILL INITIATE EXTRATROPICAL TRANSITION BY TAU 120.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT THROUGH
TAU 24 WITH MINIMAL CROSS TRACK SPREADING. AS THE TIMING AND EXTENT
OF THE NORTHWARD TURN VARIES AMONGST THE MEMBERS, THE CONSENSUS
BEYOND TAU 24 IS NOT AS TIGHT AND THEREFORE OF LOWER CONFIDENCE. FOR
THIS REASON THE JTWC TRACK FORECAST IS PLACED INITIALLY WITH MEDIUM
CONFIDENCE AND WITH LOW CONFIDENCE THEREAFTER. RELIABLE MODEL
INTENSITY GUIDANCE IS IN FAIR AGREEMENT WITH ALL MEMBERS GENERALLY
FOLLOWING THE MULTI-MODEL CONSENSUS THROUGH THE FORECAST PERIOD. AS
MENTIONED ABOVE, THERE IS A STRONG AND DIRECT CORRELATION BETWEEN
TRACK AND INTENSITY BEYOND TAU 36. THE JTWC FORECAST INTENSITY IS
THEREFORE PLACED WITH THE SAME CONFIDENCE AS THE TRACK FORECAST.

FORECAST CONFIDENCE:
TRACK 0 - 72 HR: MEDIUM
TRACK 72-120 HR: LOW
INTENSITY 0 - 72 HR: MEDIUM
INTENSITY 72-120 HR: LOW//
NNNN