Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
510 AM AST Tue Jul 2 2024

.SYNOPSIS...

Major Hurricane Beryl continues to move WNW over the Caribbean
waters and south of the local area. Unstable weather conditions
are expected throughout the day with the arrival of bands of heavy
showers and gusty winds. The biggest impact to our islands from
Beryl are the chaotic seas due to a strong swells across Caribbean
regional waters with breaking waves up to 18 feet. Conditions
will gradually improve by Wednesday, with the arrival of drier
air. Nonetheless, Invest 96L is forecast to approach the area on
Thursday and will enhance the potential for active weather through
Friday.

&&

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

Breezy to windy conditions will prevail throughout the day across
the islands as Major Hurricane Beryl continues to pass south and
away from the region. Outer rainbands from Beryl will continue to
bring showers and thunderstorms across all islands and waters
through at least this afternoon. Quick-moving showers with periods
of heavy rainfall could lead to urban and small-stream flooding and
localized flash flooding. Due to the fast-moving nature of these
showers, rainfall accumulations should generally range between 1 and
2 inches, with isolated higher amounts. However, the main hazards
from Beryl will be the dangerous seas across the Caribbean waters
and portions of the Mona and Anegada Passages, as well as the life-
threatening rip currents with high surf conditions and possible
coastal flooding across the Caribbean coastline of all the islands.

Weather conditions should improve by this evening and continue
through Wednesday as a Saharan Air Layer with drier air and
suspended Saharan dust moves from the east. Therefore, hazy skies,
warm to hot temperatures, and limited shower development are
expected through late Wednesday. A tropical wave will move across
the eastern Caribbean on Thursday, increasing shower and
thunderstorm activity again across the USVI and PR.

.LONG TERM...

The National Hurricane Center (NHC) continues to monitor an area
of low pressure (Invest 96L) located in the Central Tropical
Atlantic with a low formation chance over the next 48 hours and
the next 7 days. This low pressure is expected to move quickly
over the Caribbean waters on Thursday, and move away from the
local area by Friday morning. However, lingering moisture
associated to the Invest 96L will generate showers and isolated
thunderstorms across the islands and regional waters. By Saturday
morning this activity will move over the Mona Passage and The
Hispaniola. A mass of drier air is expected to follow and move
over the region, promoting fair weather conditions through the
beginning of the workweek. Despite of the presence of drier air,
patches of moisture will be moving into the area. This, in
combination with daytime heating and local effects will increase
the chance of showers and isolated thunderstorms over the western
portions of Puerto Rico during the afternoon hours. Latest model
guidance suggest the arrival of a tropical wave between Monday
night and Tuesday morning. Therefore, an increase in moisture is
expected along with the potential for convective activity across
the islands. Regardless of the expected weather, daytime
temperatures will continue warm to hot. Highs will remain in the
range between the mid to upper 80s and low 90s along the coastal
and urban areas and heat indices surpassing the mid 100s each day.

&&

.AVIATION...

(06Z TAFS)

SHRA/TSRA associated with the rainbands from Hurricane Beryl will
continue to increase through at least 02/18z across the local area
terminals. Therefore, tempo MVFR to brief IFR conds and mtn top
obscd are possible across all PR and USVI terminals. VFR conditions
with hazy skies are expected to gradually improve from east to west
late in the fcst period. East winds increasing at 20-25 kt with
stronger gusts.

&&

.MARINE...

Fresh to strong easterly winds will continue today as Major
Hurricane Beryl moves westward across the Caribbean Basin, far to the
south of the regional waters. This will cause hazardous marine and
coastal conditions to prevail especially for the Caribbean Waters and
Passages. The outer bands of Beryl may produce squally weather
throughout the day.

&&

.BEACH FORECAST...

Dangerous breaking waves up to 18 feet are anticipated today for
the southern coastlines. Some of these areas in Puerto Rico
include: Patillas (Road PR-3, Sector La Guarda Raya, communities
near Inches Beach, and the fishing village; Guayanilla (El Faro
community); Ponce (La Playa neighborhood); Guayama (Villa Real,
Quebrada Branderi, Playita Machete, Barrancas, Pozuelo); Salinas
(Playa Salinas and Playita); Santa Isabel (Yauca); Juana Diaz
(Pastillo and Manzanillo); and Arroyo (Barrio Pueblo and Playita
Cortada).

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
512 AM AST Wed Jul 3 2024

.SYNOPSIS...

Dry weather conditions and the presence Saharan Dust will promote
hazy skies and hot conditions today. Above-normal temperatures in
combination with the available moisture will result in warm to
hot heat indices. Therefore, a Heat Advisory will be in effect for
portions of Puerto Rico and St. Croix. A tropical wave (Invest
96L) is expected to approach the area tonight, enhancing the
potential for showers and isolated thunderstorms across the
region.

&&

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

Calm weather conditions prevailed overnight, with warmer-than-normal
low temperatures across Puerto Rico and the U.S. Virgin Islands.
Additionally, we had variably cloudy skies due to a mid- to upper-
level cloud deck associated with Major Hurricane Beryl, located
south of Hispaniola. The winds were mainly from the east to east-
northeast at 10 mph or less. Additionally, a drier air mass with
suspended Saharan dust particles began producing hazy skies and
limiting rain activity across the region.

The mid to upper-level clouds and the suspended dust particles limit
the nighttime cooling, resulting in warmer-than-normal low
temperatures. Thus, we can expect maximum temperatures to rise to
near or above-normal values today. The arrival of a Saharan Air
Layer will reduce the available moisture, but the lingering moisture
will still lead to warm and hot heat indices. This has prompted a
Heat Advisory for most of the coastal areas and western sections of
Puerto Rico and St Croix. Virgin Islands. However, expect a few
trade wind showers across the windward sections and isolated to
scattered afternoon showers across the interior and western PR.

A tropical wave, the Invest 96L, will cross the Lesser Antilles
later today, with its leading moisture arriving late tonight across
the local islands. The wave's axis should cross the region around
early Thursday morning, promoting an unstable weather pattern
through the 4th of July. This wave may bring strong thunderstorms,
producing downpours and frequent lightning, especially during the
day and afternoon of the 4th. Urban and small stream flooding may
also be observed. Residents and visitors should monitor the weather
conditions for additional updates.

The wave's trailing moisture will linger across the regions through
Friday morning, when additional suspended dust particles from the
African deserts will arrive, creating hazy skies once more. However,
the interaction of the available moisture and the dust particles
will enhance the formation of afternoon and evening convection,
especially across western PR and the surrounding waters. A drier
air mass with Saharan Dust Particles will result in hazy skies
affecting visibilities, lowering them around 6 SMi. SHRA/TSRA could
develop across the interior and western PR between 03/17-21z. A
tropical wave will deteriorate weather conditions after 04/06z
onward. The winds will remain calm to light and variable through
12z, returning from the E to ENE at 15-20 kt with gusts between 20
and 30 kt and sea breeze variations.

LONG TERM...Saturday through Wednesday...

A strong high pressure located in the central Atlantic will maintain
the wind flow from the east southeast for most of the long-term
period. Dry conditions are expected to prevail for the first half
of the period as a drier airmass moves into the region with
moderate to high concetrations of Saharan Air Layer (SAL). Hazy
skies will dominate until at least Monday, resulting in lower
visibilities. Very hot conditions are expected too, with
temperatures rising to the 90s along the coastal and urban
portions of the islands. This in combination with the available
moisture will result in higher heat indices across the region
surpassing the mid 100s. By the second half of the period a
vigorous tropical wave is anticipated to approach the local
islands. The precipitable water content analysis suggest values
between 1.90 to 2.15 inches from Tuesday to Wednesday. This wave
will move relatively fast across the region on Tuesday. Moderate
to heavy showers and isolated thunderstorms are expected across
the western and northwestern portions of Puerto Rico during the
afternoon hours. The US Virgin Islands can expect passing showers
throughout the morning hours and isolated shower activity during
the afternoon. After wave passage, a drier pattern will establish
and will persist through the week.

&&

.AVIATION...

(06Z TAFS)

A drier air mass with Saharan Dust Particles will result in hazy
skies affecting visibilities, lowering them around 6 SMi. SHRA/TSRA
could develop across the interior and western PR between 03/17-21z.
A tropical wave will deteriorate weather conditions after 04/06z
onward. The winds will remain calm to light and variable through
12z, returning from the E to ENE at 15-20 kt with gusts between 20
and 30 kt and sea breeze variations.

&&

.MARINE...

Fresh to locally strong easterly winds will continue today as Major
Hurricane Beryl continues moving westward across the Caribbean Basin
south of Hispaniola. This will cause hazardous marine and coastal
conditions to prevail especially for the Caribbean Waters and
Passages. A tropical wave will move across the Eastern Caribbean
later today, deteriorating the local weather and marine conditions
late tonight into Thursday.

&&

.BEACH FORECAST...

Coastal condtions will gradually improve as Hurricane Beryl
continues to move westward. A high risk of life-threatening rip
currents remain in effect until this afternoon for southern Puerto
Rico. Elsewhere, a moderate risk of rip currents is in effect.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
458 AM AST Thu Jul 4 2024

.SYNOPSIS...

The passage of a tropical wave (Invest 96L) will increase the
frequency of passing showers and thunderstorms across the region
through at least Friday. Even with the anticipated increase in
cloud cover and high chances of rain, warm to hot conditions will
continue. A drying trend is expected during the weekend.
Nonetheless, by Tuesday another tropical wave will reach the
islands increasing the potential for shower activity once again.

&&

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

Calm weather conditions prevailed overnight, with warmer-than-normal
low temperatures across Puerto Rico and the US Virgin Islands around
midnight and before the arrival of a tropical wave by early this
morning. Then, showers and thunderstorms began to affect the Anegada
Passage and Caribbean Water, moving over St Croix early this
morning. The skies were variably cloudy due to a mixture of mid- to
upper-level clouds and the cloudiness from the approaching tropical
wave. The winds were mainly from the east to east-northeast at 10
mph or less.

Today, a tropical wave will bring unsettled weather conditions. The
instability and moisture associated with this wave will likely fuel
the formation of strong thunderstorms, leading to downpours, gusty
winds, and frequent lightning. These conditions will first affect
the local waters, the US Virgin Islands, and eastern PR before
spreading into the interior and north and western sections of PR by
mid-morning into the afternoon. Of particular concern is the
potential for urban and small-stream flooding. It's crucial that
residents and visitors stay updated on the weather conditions and
take necessary precautions. The wave's trailing moisture will linger
across the regions through Friday afternoon. During the event, 2 and
4 inches of rain will remain possible, especially across the
southern and eastern third of Puerto Rico, with higher isolated
amounts.

Rain activity will tampered off about Friday afternoon into the
evening as a Saharan Air Layer moves in following the trailing
moisture of today's wave. Therefore, expect hazy skies due to the
increase in suspended dust particles. However, the interaction of
the available moisture, local effects, sea breeze, excessive
heating, and dust particles could promote the formation of strong
afternoon and evening convection, especially across western PR and
the surrounding waters.

The dry and hazy weather pattern will extend into the weekend.
However, a surface high-pressure building across the central
Atlantic and extending into the northeast Caribbean will promote
breezy easterly winds, advecting occasional patches of clouds and
showers, especially across the windward sections of the US Virgin
Islands and Puerto Rico.

&&

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

The inherited forecast remains unchanged. The latest model guidance
continues to suggest a strong high-pressure system over the
central Atlantic. This weather feature will maintain the wind flow
out of the east-southeast through most of the long-term period.
Precipitable water models show values in the 25th percentile or
below normal climatological levels for this time of the year as a
drier airmass continues to move across the region with low
concentrations of Saharan dust according to the Dust Aerosol
Optical Depth model. Therefore, we foresee dry weather conditions
through Monday. We anticipate warm weather conditions with
temperatures in the 90s along the coastal and urban areas of the
islands and in the upper 70s to low 80s in the mountainous areas.
As mentioned in previous discussions, the mixture of warm
temperatures and the available moisture will result in higher heat
indices across the region, surpassing the mid-100s.

From late Monday into Tuesday, expect a change in weather
conditions as a vigorous tropical wave approaches the local
islands. The precipitable water content analysis shows values
between 1.90 and 2.30 inches on those days. This wave will move
relatively fast across the region, particularly on Tuesday. With
the passage of this tropical wave, expect the passing showers to
increase across the islands during the morning hours, with
moderate to heavy showers and isolated thunderstorms expected
across the western and northwestern portions of Puerto Rico during
the afternoon hours. At this time, mid-week is the transition day
to a drier weather pattern.

&&

.AVIATION...

(06Z TAFS)

A tropical wave will bring SHRA/TSRA across the local flying area,
promoting brief MVFR conds. Although VFR conds will prevail,
TSRA/SHRA will spread across ISX through around 4/15z, across
IST/JSJ/JPS btwn 04/10z-15z, and into the rest of PR after 04/14z.
The unsettled wx pattern will extend thru 05/15z, when a drier air
mass with suspended dust particles will move across the islands. The
winds will remain calm-light/var thru 12z, returning from the E to
ENE at 15-20 kt with gusts btwn 20-30 kt near TSRA and sea breeze.

&&

.MARINE...

A tropical wave moving westward will bring more showers and
thunderstorms across the regional waters today and tomorrow. A
surface high pressure over the central Atlantic will strengthen and
extend into the northeast Caribbean on Friday afternoon through the
weekend, leading to moderate and fresh easterly winds across the
local waters. Another tropical wave will be approaching the islands
by late Monday night or Tuesday.

&&

.BEACH FORECAST...

Coastal conditions will continue to improve gradually. There is
moderate risk along all the coastal areas of the islands, with the
exception of the western beaches of PR where the risk is low. In
the island of St. Croix the risk will become high as the
approaching tropical wave get closer. For more information,
consult the Coastal Hazard Message (CFWSJU) issued by the NWS San
Juan office.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
435 AM AST Fri Jul 5 2024

.SYNOPSIS...

Residual moisture from the tropical wave (Invest 96L) will lead
to occasional passing showers across the region through at least
this afternoon. A drying trend is expected during the weekend
along with a Saharan Air Layer. Warm to hot conditions will
continue. The next tropical wave will reach the islands Monday
night into Tuesday increasing the potential for shower activity
once again.

&&

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

Last night, a tropical wave caused showers and thunderstorms in the
local waters. These showers and thunderstorms then moved inland
across the US Virgin Islands, as well as the south and east of
Puerto Rico. Additionally, the arrival of a Saharan Air Layer led to
hazy skies, and the GOES-E infrared channel detected cloudy skies.
These two factors - the suspended dust particles and cloud cover -
blocked outgoing longwave radiation, preventing nighttime cooling
and resulting in warmer-than-normal low temperatures. The winds were
mainly from the east-southeast at 10 mph or less.

From this morning through this afternoon, the trailing moisture
associated with the tropical wave will maintain high low-level
moisture values, which, combined with the maximum air temperatures,
will result in hazardous heat index values along PR and the USVI's
coastal and urban sections. Therefore, a Heat Advisory is in effect
for most of these locations. The skies will also be hazy due to
moderate to high suspended Saharan dust particles. The proximity of
a mid to upper-level trough north of the islands will promote enough
instability, resulting in periods of showers and thunderstorms
across the local waters, eastern Puerto Rico, and the Virgin
Islands. The combination of the lingering tropical moisture,
excessive heating, suspended dust particles, topography, and sea
breeze variations will promote some isolated strong thunderstorms,
especially during the afternoon.

Rain activity will tampered off late this afternoon into the evening
as the concentrations of the suspended African dust particles
increase, making the haziness more evident and promoting stable
conditions. The dry, stable, and hazy weather pattern will extend
into the weekend. However, a surface high-pressure building across
the central Atlantic and extending into the northeast Caribbean will
promote breezy easterly winds, advecting occasional patches of
clouds and showers, especially across the windward sections of the
US Virgin Islands and Puerto Rico. A trade wind perturbation may
increase the potential for showery weather on Sunday, as a sharp
increase in moisture would be possible.

&&

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

On Monday, residual Saharan dust particles will remain in low
concentrations across Puerto Rico and the U.S. Virgin Islands.
Nonetheless, by late Monday, expect an increase in moisture and
shower activity as a tropical wave, along with a wind surge,
reaches the islands on Tuesday. Precipitable water models show
values in the 50th percentile or around normal climatological
levels for this time of the year with the passage of this tropical
wave. This wave will move relatively fast across the region,
particularly on Tuesday. With it, expect the passing showers to
increase across the islands during the morning hours, with
moderate to heavy showers and isolated thunderstorms expected
across the western and northwestern portions of Puerto Rico during
the afternoon hours. Trailing moisture associated with the
tropical wave will prevail over the long-term period.

The latest model guidance continues to suggest a strong surface to
mid-level high-pressure system over the central Atlantic. This
weather feature will maintain the wind flow out of the east-
southeast through at least Friday. With these weather conditions,
we anticipate warm weather conditions with temperatures in the 90s
along the coastal and urban areas of the islands and in the upper
70s to low 80s in the mountainous areas. As mentioned in previous
discussions, the mixture of warm temperatures and the available
moisture will result in higher heat indices across the region,
surpassing the mid-100s.

&&

.AVIATION...

(06Z TAFS)

Although VFR conds will prevail for most of the period. SHRA/TSRA
will affect the surrounding waters of USVI and may move inland,
affecting ISX or IST through at least 05/18z; then this activity may
spread into PR, affecting JSJ/JPS or JBQ between 05/16-05/22z,
promoting brief MVFR conds. Hazy skies will remain possible as a SAL
enters the region. The winds will remain calm to light and variable
through 12z, returning from the E to ESE at 15-20 kt with gusts
between 20 and 30 kt near TSRA and sea breeze variations after 12z.

&&

.MARINE...

A departing tropical wave will continue to bring showers and
thunderstorms across the regional waters through this morning. A
strengthening surface high pressure over the central Atlantic will
extend into the northeast Caribbean by this afternoon through the
weekend, leading to moderate to fresh easterly winds. The next
tropical wave will be approaching the islands by late Monday night
into Tuesday, increasing the chance of showers across the local
waters.

&&

.BEACH FORECAST...

Today, the rip current risk should remain moderate along the
southern beaches of Puerto Rico, Vieques, Culebra, Saint Thomas,
Saint John, and Saint Croix. Elsewhere should remain low. For
additional information, consult the Surf Zone Forecast (SRFSJU)
issued by the NWS San Juan Office.

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
511 AM AST Sat Jul 6 2024

.SYNOPSIS...

A Saharan Air Layer (SAL) will promote hazy skies and limit
longwave radiational cooling, promoting warmer-than-normal low
temperatures today and tomorrow. Combining the available moisture
and maximum air temperatures in the 90s will promote hazardous
heat index values across the Puerto Rico and US Virgin Islands
coastal areas, where an Excessive Heat Warning and Heat Advisory
are in effect. The next tropical wave will arrive between Monday
afternoon and Tuesday. Another pulse of SAL may move in by the
middle of next week. Another tropical wave will swing by the
islands around the following weekend.

&&

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

During the overnight hours, Puerto Rico and the U.S. Virgin Islands
experienced mostly calm weather conditions, with some tradewind
showers in the southern and eastern municipalities of Puerto Rico.
The showers were not significant, and accumulations were below 0.30
inches. Hazy skies were observed as a Saharan Air Layer prevailed.
Satellite observations also suggested partly cloudy skies across
the islands. The combination of cloudiness and hazy skies
prevented significant nighttime cooling, resulting in warmer-than-
normal low temperatures. Temperature-wise, they remain in the low
80s along the coastal/urban areas, while across the higher
elevations, they remain in the 70s. Official weather stations
reported southeasterly winds of less than 10 mph throughout the
night.

Todays forecast leans towards hazy skies and dry air dominating the
area, with the possibility of some rainfall and isolated
thunderstorm activity by late afternoon and evening due to suspended
dust particles. These weather conditions should prevail through at
least Sunday. Model guidance suggests a surface high-pressure system
building across the central Atlantic and extending into the
northeast Caribbean, leading to breezy easterly winds and occasional
clouds and showers, especially in the windward sections of the U.S.
Virgin Islands and Puerto Rico.

An increase in moisture is expected on Sunday as a trade wind
perturbation moves through the region, potentially bringing showery
weather. Precipitable water models suggest normal to below-normal
climatological levels for this time of year through the beginning of
the workweek. The forecast for Monday leans towards calm weather
throughout the day, with Saharan dust particles reaching the area by
late Monday and a gradual increase in moisture associated with an
approaching tropical wave.

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

Model guidance suggests the lingering moisture of a tropical wave
on Tuesday, pooling total precipitable water (TPW) between 2.0
and 2.30 inches across PR and the USVI's region. Additionally, we
observed steep lapse rates at the 850-700 MB layer, and the
African Easterly Jet maxima are moving south of the islands on
Tuesday and Wednesday. Under this weather pattern, scattered to
numerous showers and thunderstorms may develop across the region
each day. We noted that model guidance suggests surges of SAL
between the available moisture, which may also cause hazy skies.
If thunderstorms develop, the interaction with the suspended dust
particles could enhance them.

A surface high pressure anchored across the North Atlantic Ocean
will promote breezy easterlies across the islands throughout the
week. This wind flow will promote a mixture between the arrival of
dry slots and pockets of moisture each day. This means that we
may observe a mix of clouds and sunshine or clear skies (during
the nighttime) with the arrival of quick passing showers advect by
the winds. Although we may observe periods of rainy conditions,
the interaction of plenty of low-level moisture, above-normal sea
surface temperatures, and maximum summer heat temperatures could
result in an extended warm-to-hot spell during the upcoming week
if we do not observe prolonged periods of rain activity.

GFS suggests another tropical wave moving across the northeast
Caribbean around next weekend, which could promote unsettled
weather conditions.

&&

.AVIATION...

VFR conds will prevail across all terminals. However, brief MVFR
conds are possible after 06/17z in TJBQ and TJSJ. Hazy skies will
remain possible as a SAL prevails in the region. The winds will
remain from the ESE at 5 to 10kt through 06/12 and increase to 15-20
kt with gusts between 20 and 30 kt near TSRA and sea breeze
variations after 12z.

&&

.MARINE...
A surface high pressure across the Atlantic Ocean will tighten the
local pressure gradient, promoting choppy seas across the islands
through the next few days. Seas will range between 3 and 5 feet
across most of the coastal waters. Winds will be mainly from the
east to southeast at 10 to 15 knots, increasing between 15 and 20
knots later in the day.

In summary, a drier airmass with Saharan Dust will continue to
move over the region, limiting shower development. A strengthening
surface high pressure over the central Atlantic will extend into
the northeast Caribbean through the weekend, leading to moderate
to fresh easterly winds. The next tropical wave will be approaching
the islands by late Monday night into Tuesday, increasing the
chance of showers across the local waters.

&&

.BEACH FORECAST...
There is a moderate risk of rip currents for southwest PR,
Vieques, Culebra and St Croix today, becoming moderate for most
of the beaches tomorrow due to the increase in the easterly winds.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
403 AM AST Sun Jul 7 2024

.SYNOPSIS...

The available moisture associated with a trade wind perturbation
and maximum air temperatures in the 90s will promote hazardous
heat index values across the Puerto Rico and US Virgin Islands
coastal areas, where an Excessive Heat Warning and Heat Advisory
are in effect. A relatively stable atmosphere will prevail
throughout the week. However, the chance of rain will increase
due to a couple of tropical waves, the first arriving on Tuesday
and the second by the weekend. Between and around those waves
(especially on Tuesday and Wednesday), air masses with important
suspended dust particles from the African Deserts could inhibit
widespread rain activity and promote hazy skies.

&&

.SHORT TERM....Tonight through Tuesday...

Overnight, Puerto Rico and the U.S. Virgin Islands experienced
predominantly calm weather conditions, with hazy skies prevailing
due to the Saharan Air Layer. Like previous days, the prevailing
Saharan Air Layer prevented significant nighttime cooling, resulting
in warmer-than-normal low temperatures. For that reason, official
weather stations reported temperatures in the low 80s along the
coastal/urban areas, while across the higher elevations, they were
in the 70s. Wind-wise, they were mostly out of the east and stayed
below 10 mph.

The latest model guidance suggests a surface high-pressure system
building over the central Atlantic and extending into the northeast
Caribbean, leading to breezy easterly winds and occasional clouds
and showers, especially in the windward sections of the U.S. Virgin
Islands and Puerto Rico. Today, the forecast leans towards hazy
skies with the introduction of a trade wind perturbation that can
bring a slight increase in showery weather. Nonetheless, we
anticipate little cloud growth across the islands, with some
rainfall and isolated thunderstorm activity by late afternoon due to
suspended dust particles. Precipitable water models suggest normal
to below-normal climatological levels for this time of year through
at least the beginning of the workweek. The forecast for Monday
leans towards calm weather throughout the day and a gradual increase
in moisture associated with an approaching tropical wave by late
Monday.

On Tuesday, a weak tropical wave with its associated wind surge will
reach the islands. At this time, we do not anticipate significant
rainfall activity nor cloud growth as an extensive mass of Saharan
Air Layer will move across Puerto Rico and the U.S. Virgin Islands.
The Dust Aerosol Optical Thickness model suggests concentration
values around 0.55, and to be considered a slight to moderate event,
it needs to exceed 0.20. Therefore, it was added to the forecast and
we want to inform citizens and tourists about this upcoming slight
to moderate dust event that could affect people with respiratory
illness.

.LONG TERM...WEDNESDAY THROUGH SUNDAY...

Relatively stable atmospheric conditions will prevail throughout
most of the forecast, with above-normal heights at mid- and upper-
level, warmer-than-normal temperatures at 500 MB, and relatively
stable lapse rates at mid- and low levels. Additionally, the 925
MB temperatures suggested warmer-than-normal temperatures, which
may indicate a warm-to-hot spell during those days in the long
term.

The NASA Dust Extinction guidance suggests the presence of
significant suspended dust particles from the African deserts,
especially on Wednesday, with some traces remaining on Thursday.
This dry air mass will surround the trailing moisture from a
tropical wave, which may limit widespread rain activity but create
hazy skies. However, be prepared for the possibility of some
strong thunderstorms, especially on Wednesday afternoon, as steep
lapse rates between 850-700 MB may be possible during those days
due to the passing wave. However, the bulk of moisture and the
African Jet-stream maxima may be located off to the south of the
islands, across the southeastern Caribbean.

Once again, model guidance suggests a surface high pressure
anchored across the North Atlantic Ocean that could promote breezy
easterlies across the islands throughout the second part of the
week. Under this wind flow, we may observe the arrival of dry
slots and pockets of moisture each day, resulting in a mix of
clouds and sunshine or clear skies (during the nighttime) and the
arrival of quick passing showers.

Model guidance suggests a tropical wave arriving by the upcoming
weekend. If the dry air mass surrounding it does not negatively
impact it, we may see a wet and unstable pattern with a better
chance of organizing convection on Saturday or Sunday.

&&

.AVIATION...
(06Z TAFS)

VFR conds will prevail across all terminals. However, brief MVFR
conds are possible after 07/17z near TJBQ. Hazy skies will remain
possible as a SAL prevails in the region. The winds will remain from
the E at 5 to 10kt through 07/12 and increase to 15-20 kt with gusts
between 20 and 30 kt near TSRA and sea breeze variations after 14z.

&&

.MARINE...

A surface high pressure anchored across the Atlantic Ocean will
tighten the pressure gradient across the Northeast Caribbean,
promoting moderate to fresh easterly winds with choppy seas. A
tropical wave will cross the Lesser Antilles late Monday night and
approach the islands on Tuesday with residual moisture until
Wednesday.

&&

.BEACH FORECAST...

The CariCOOS buoy network reported seas around 3 feet (from the
northeast with a 5-second period in the Atlantic and from the
southeast with a 6-second period in the Caribbean) and winds
around 13 knots out from the east. The water temperatures were in
the mid-80s, as were the air temperatures above the water. Winds
will increase at 15 to 20 knots during the day, producing choppy
seas between 4 and 5 feet or higher.

Beachgoers, the risk of rip currents will be moderate in the north
and southwest of PR, Culebra, and St Croix.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
508 AM AST Mon Jul 8 2024

.SYNOPSIS...

A tropical wave will reach the islands increasing the potential
for showers and thunderstorms and bringing a break from Saharan
dust today, but another Saharan Air Layer (SAL) is expected to
reach the islands tomorrow and last until mid week. Lingering
moisture and slightly unstable atmospheric conditions will
continue to support shower and thunderstorm development for the
same period. In addition, an elevated to significant heat risk
will likely persist. Another tropical wave is forecast to reach
the islands by next weekend.

&&

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

An overnight radar and satellite imagery analysis indicated clear to
partly cloudy skies, with passing showers brushing Puerto Rico's
northern coast, Vieques, Culebra, and the northern U.S. Virgin
Islands. Reports again highlighted warm overnight low temperatures
above 80 degrees Fahrenheit in coastal areas of the San Juan
metropolitan area, eastern and southern Puerto Rico, and the local
islands. Coastal observation sites and local buoys have also
recorded warm low temperatures, hovering around 83-84 degrees
Fahrenheit. Winds were mainly light to calm and variable.

Satellite and radar data also indicated a tropical wave moving
through the northern Leeward Islands, accompanied by increased
cloudiness and persistent thunderstorm activity. As this system
advances through the eastern Caribbean, it will bring substantial
tropical moisture, with precipitable water levels exceeding seasonal
moisture thresholds through most of the forecast period. This will
elevate the likelihood of showers and thunderstorms. On Tuesday, a
brief break is expected as a drier air mass and a dense Saharan Air
Layer follow the tropical wave. However, persistent lingering
moisture and slightly unstable atmospheric conditions will continue
to support shower and thunderstorm development throughout the
forecast period. This weather pattern may result in heavy rainfall,
frequent lightning, and strong winds, leading to a moderate to high
risk of excessive rainfall, particularly in eastern and far western
Puerto Rico. Potential impacts include water ponding on roads,
flooding in poorly drained areas, and urban and small stream
flooding. Localized flash floods are also possible. Additionally,
breezy conditions, driven by high surface pressure over the North
Atlantic, are likely, especially in southern and northern Puerto
Rico and the nearby islands.

Even with the anticipated high rain chances, warmer-than-usual
conditions will persist in the coming days. Daytime highs will range
from the lower 90s in lower elevations to around 80 degrees in
higher elevations. With abundant moisture in the air, heat indices
in many coastal and urban areas may soar above 108 degrees
Fahrenheit. These conditions present significant health risks,
leading to the issuance of Heat Advisories. It is crucial for
residents and visitors, especially those participating in outdoor
activities, to take necessary precautions to stay safe.

&&

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

Model guidance suggests a broad surface high pressure will remain
anchored across the Atlantic Ocean, promoting easterly winds across
the islands throughout the long-term period. Thursday seems to be
a transition day where we still have residual humidity from the
tropical wave, but some patches of drier air are beginning to
enter along with the wind flow, resulting in a mix of clouds and
sunshine and the arrival of quick passing showers. The latest
Precipitable Water (PW) models suggest values decreasing from
above-normal to normal climatological levels that day. Still,
afternoon convection will remain possible with available moisture,
diurnal heating, and local effects. By the end of the week, the
NASA Dust Extinction guidance is suggesting the presence of
another Saharan Air Layer across the islands which probably will
limit rain development that day. However, during the weekend, the
next tropical wave should approach our region. If the dry air mass
surrounding it does not negatively impact it, we may see a wet
and unstable pattern with a better chance of organizing convection
on Saturday or Sunday.

Temperature-wise, an elevated to significant heat risk will likely
persist across lower elevations and coastal areas of Puerto Rico
and the rest of the islands, as models suggest the pattern will
continue with warmer-than-normal temperatures at 500 MB and 925 MB.

&&

.AVIATION...

(06Z TAFs)

VFR conditions will likely prevail across all terminals through
the morning hours. However, increased SHRA/TSRA from a passing
tropical wave may result in MVFR to brief IFR conditions, with
reduced visibility and lower ceilings, at most terminals. Light to
calm and variable winds will become more easterly and increase to
14-18 knots between 08/13-23Z, accompanied by higher gusts and
sea breeze variations. Higher wind gusts are likely near the
SHRA/TSRA.

&&

.MARINE...

A surface high pressure anchored across the Atlantic Ocean will
tighten the pressure gradient across the Northeast Caribbean and
promote moderate to fresh easterly winds with choppy seas. A
tropical wave will move across the islands today, increasing the
potential for showers and thunderstorms across the local waters.
Higher winds and seas near thunderstorms.

&&

.BEACH FORECAST...

There is a moderate risk of rip currents for southwestern,
northwestern, northern and eastern Puerto Rico, as well as for
Culebra, St. Thomas, St. John, and St. Croix. Low risk elsewhere.
Mainly low risk is forecast through mid-week, then moderate risk
returns.For additional information, consult the Surf Zone
Forecast (SRFSJU) issued by the NWS San Juan Office.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
446 AM AST Tue Jul 9 2024

.SYNOPSIS...

Residual moisture from a departing tropical wave and the
proximity of a TUTT low to the north will keep the potential for
showers and t-storms across the forecast area through mid-week.
Additionally, a Saharan Air Layer (SAL) over the islands will
maintain hazy skies through Wednesday afternoon, then another
round should reach the islands around Friday afternoon. An
elevated to significant heat risk will also likely persist.
Another tropical wave is forecast to reach the islands during the
next weekend.

&&

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

An overnight radar and satellite imagery analysis indicated
increased cloud cover and scattered showers with isolated
thunderstorms over the local waters, with some bringing rains
around a quarter of an inch in eastern Puerto Rico, Culebra, and
the northern U.S. Virgin Islands. Reports again highlighted warm
overnight low temperatures above 80 degrees Fahrenheit in most
coastal areas of Puerto Rico and the local islands. In contrast,
higher elevations have reported low temperatures in the upper 60s.
Winds were mainly from the east-northeast at 5-10 mph but light
to calm and variable further inland.

Satellite and radar observations indicate increased cloud cover and
persistent thunderstorm activity to the east and north of the
forecast area, driven by residual moisture from a departing tropical
wave and the proximity of a TUTT low to the north. This conditions
will likely spread west-southwestward into parts of our forecast
area today, with favorable conditions likely persisting through at
least Wednesday. Above-average precipitable water values ranging
from 2.0 to 2.3 inches and near seasonal 500 mb temperatures will
support favorable conditions for the development of deep convection.

Meanwhile, a dense Saharan Air Layer (SAL), mixed around the wave's
moisture field, will maintain a moderate to severe dust event
through at least Wednesday afternoon, exacerbating health conditions
for immunocompromised individuals, vulnerable populations, and those
sensitive to air quality issues. Additionally, it will cause hazier
skies and reduced visibility. More stable conditions will likely
return on Thursday with the entrance of a drier-than-normal airmass
and mid-level ridging building over the region.

Today and tonight, the anticipated showers and thunderstorms will
likely generate frequent lightning, strong gusty winds, and heavy
downpours, raising some flooding concerns. So far, there is a
moderate risk of excessive rainfall for the northeastern and western
Puerto Rico portions. A limited risk exists for the remaining land
areas except for south-central to southwestern Puerto Rico. Potential
impacts range from ponding water on roads to flooding in poorly
drained areas and urban and small stream flooding. Localized flash
floods may also occur from the most intense and persistent rainfall.
Despite increasing concentrations of Saharan dust potentially limiting
convective development, the current forecast leans towards a wetter
trend.

Warmer-than-normal conditions will persist in the coming days.
Daytime highs will range from the lower 90s in lower elevations to
around 80 degrees in higher elevations. With abundant moisture in
the air, heat indices in many coastal and urban areas may soar
above 108 degrees Fahrenheit. These conditions present significant
health risks, and as a result, Heat Advisories have been issued
for all coastal municipalities of Puerto Rico, Vieques, Culebra,
and the US Virgin Islands. It is crucial for residents and
visitors, especially those participating in outdoor activities, to
take necessary precautions to stay safe.

&&

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

Based on the latest models, a broad surface high pressure should
remain anchored across the Atlantic Ocean, promoting easterly
winds across the islands most of the long-term period. By next
Friday, the NASA Dust Extinction guidance is suggesting the
presence of another Saharan Air Layer across the islands which
probably will limit rain development that day. However, afternoon
some afternoon convection across western Puerto Rico and the
western local waters cannot be ruled out of the forecast due to
low level moisture, diurnal heating, and local effects. During the
weekend, the next tropical wave should approach our region. If
the dry air mass surrounding it does not negatively impact it, we
may see a wet pattern with a better chance of organizing convection,
mainly on Saturday. On Sunday, the main area of moisture associated
with a tropical wave should be departing allowing some patches of
drier air to filter to our region with the wind flow, resulting
in a mix of clouds and sunshine and reducing rain chances. However,
early next week, the high pressure across the Atlantic moves more
to the east changing the wind flow to more southeasterly and
pushing a moisture field from the previous tropical wave to our
area resulting in a wet pattern to return. Conditions aloft should
enhance instability as a troughiness will be dominating in the
upper levels.

Temperature-wise, an elevated to significant heat risk will likely
persist across lower elevations and coastal areas of Puerto Rico
and the rest of the islands during the long term period.

&&

.AVIATION...
(06Z TAFS)

VFR conditions will likely prevail across all terminals through the
morning hours. However, near-shore and afternoon SHRA/TSRA may
result in MVFR to brief IFR conditions, with reduced visibility and
lower ceilings, particularly for TJSJ and TJBQ. The remaining
terminals may experience the occasional VCSH/VCTS. Light to calm and
variable winds will become more E-ENE and increase to 14-18 knots
between 09/13-23Z, accompanied by higher gusts and sea breeze
variations. Higher wind gusts are likely near the SHRA/TSRA.

&&

MARINE...

A surface high pressure anchored across the Atlantic Ocean will
promote moderate easterly winds through midweek, then increasing
to moderate to fresh for the latter part of the week. Residual
moisture from a departing tropical wave will keep the potential
for showers and thunderstorms across the local waters today and
Wednesday. Higher winds and seas are expected near thunderstorms.

&&

.BEACH FORECAST...

Today, there is a low risk of rip currents across Puerto Rico
beaches, including Vieques and Culebra. In the USVI, there is a
low risk of rip currents in St. Thomas and St. John, however St
Croix remains in a moderate risk. For tomorrow, similar conditions
should be present. For additional information, consult the Surf Zone
Forecast (SRFSJU) issued by the NWS San Juan Office.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
526 AM AST Thu Jul 11 2024

.SYNOPSIS...

Moisture is forecast to gradually decrease, with patches of more
humid and drier air reaching the region, through Friday night and
the establishment of mid to upper level ridging over the region.
More breezy easterlies, during the second half of the week, with
showers and possible afternoon thunderstorms in the forecast, mainly
due to diurnal heating and local effects, today and Friday. Another
pulse of suspended Saharan dust particulates will reach the islands
on Friday and persist through Sunday. An elevated heat risk will
also likely persist. Moisture from another tropical wave is forecast
to reach the islands by Friday night leading to an increase in showers
and thunderstorms throughout the weekend. On Monday, another TUTT
will approach the region enhancing instability.

&&

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

Today, moisture levels will decrease slightly to near-normal levels.
Meanwhile, the TUTT that impacted the area the previous day will
continue to move westward as ridging aloft settles in. This will
promote a less active day, with some showers reaching windward
coastal areas during the morning hours. In the afternoon, diurnal
heating and local effects will promote showers and isolated
thunderstorms across western and northwestern portions of Puerto
Rico under an east-southeast steering flow. However, this activity
is expected to have less areal coverage and last for a shorter
period.

For the rest of the short-term forecast, weather conditions will
vary. On Friday, another pulse of suspended Saharan dust
particulates will reach the islands, promoting hazy skies for the
most part. However, the leading edge of a tropical wave will also
arrive, increasing moisture content to above-normal levels,
particularly during the afternoon hours. This raises the potential
for isolated to scattered showers and some isolated thunderstorms in
localized areas, mostly across interior and western Puerto Rico. By
Saturday, model guidance suggests the arrival of a wind surge, which
could bring squally weather for a very short period. Therefore,
after 12z, expect an increase in thunderstorm activity with the
potential for frequent lightning and gusty wind conditions. Behind
the wind surge, a broad area containing higher concentrations of
suspended Saharan dust particulates will engulf the forecast area.
This could shorten the period of shower activity in some areas,
bringing back hazy skies by late Saturday evening.

Warmer-than-usual conditions will persist in the coming days.
Consequently, some urban and coastal areas may experience a limited
to elevated excessive heat threat, increasing the possibility of
heat exhaustion with prolonged exposure, particularly on Friday and
Saturday.

&&

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

Based on the latest models, during the beginning of the long-term
period, we will continue to have the presence of Saharan dust
across the region exacerbating health conditions for immunocompromised
individuals, vulnerable populations, and those sensitive to air
quality issues. During Sunday afternoon and evening, the Saharan
dust should be receding. Residual moisture from a tropical wave
will keep precipitable water mainly above normal values, with a
slight decrease to normal on Sunday. On Monday, PWAT should
increase again as a Tropical Upper- Tropospheric Trough (TUTT)
will approach the region and for now looks like it could be the
more active day of this forecast period. This feature will also be
evident in the mid and low levels of the atmosphere, with winds
first from the northeast on Monday, and then shifting from the
southeast on Tuesday and Wednesday. Early next week, enough
instability will be available to generate active afternoons across
the interior and western Puerto Rico. Temperatures in the 500 MB
are expected to drop to around -7 degrees Fahrenheit on Sunday and
Monday and that could be beneficial for thunderstorm development.
Trade winds will carry some showers across portions of Puerto
Rico and the Virgin Islands too, but the higher risk of flooding
and mudslides will be for the interior and west of Puerto Rico.
Potential impacts range from ponding water on roads to flooding in
poorly drained areas and urban and small stream flooding.

In terms of temperatures, warmer-than-usual conditions are
expected for most of the period. On Monday, if the rain
materializes, the temperature should stay a few degrees lower.
Generally, daytime highs will range from the lower 90s in lower
elevations to around 80 degrees in higher elevations. With
abundant moisture in the air, heat indices in coastal and urban
areas may soar above 108 degrees Fahrenheit.

&&

.AVIATION...
(06Z TAFS)

VFR conditions will likely prevail across all terminals through the
morning hours. However, afternoon SHRA/TSRA may result in MVFR to
brief IFR conditions, with reduced visibility and lower ceilings,
particularly for TJBQ. The remaining terminals may experience the
occasional VCSH/VCTS. Light to calm and variable winds will become
more E-ESE and increase to 14-18 knots between 11/13-23Z, accompanied
by higher gusts and sea breeze variations. Higher wind gusts are
likely near the SHRA/TSRA.

&&

.MARINE...

A surface high pressure across the Atlantic Ocean will promote
moderate to fresh easterly to southeasterly winds for the next
several days. An approaching drier airmass will result in less
rain chances across the waters today, but some thunderstorms could
develop and move across the western waters of Puerto Rico during
the afternoon hours. Moisture from another tropical wave is
expected to reach the northeastern Caribbean by Friday night
leading to an increase in showers and thunderstorms throughout the
weekend.

&&

.BEACH FORECAST...

There is a moderate risk of rip currents for beaches of Saint Croix
today, low risk elsewhere. However, by tonight, the moderate risk
of rip currents is forecast to spread to the rest of the local islands
and remain moderate through the upcoming weekend. For additional
information, consult the Surf Zone Forecast (SRFSJU) issued by the
NWS San Juan Office.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
508 AM AST Fri Jul 12 2024

.SYNOPSIS...

Another pulse of suspended Saharan dust particulates will reach
the region today and prevail through Sunday. Tonight and Saturday,
a tropical wave and its moisture field is forecast to move across
the region leading to an increase in showers and thunderstorms
throughout the weekend. On Monday, a TUTT will approach the region
enhancing instability and maintaining the wet and unstable pattern
in place through at least the first part of the week. An elevated
heat risk will also likely persist.

&&

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

The Doppler radar loop since last night showed a few lines of
showers reaching the municipalities of eastern Puerto Rico, as
well as the Virgin Islands. These showers were weak to moderate,
and rainfall accumulations were minimal.

A surface high pressure will maintain the wind flow from the east,
and enhanced, at speeds of 17-20 knots at the low levels. In this
flow, a small patch of moisture will continue to cross the region,
resulting in passing showers for eastern Puerto Rico, and for the
Virgin Islands. Wet roads and ponding of water can be anticipated
with this activity. Saharan dust will also move in today, and skies
will turn gray due to the haze. Additionally, the available moisture
and the local effects will aid in the development of showers this
afternoon, from the islands into portions of eastern Puerto Rico,
but with the strongest activity in the interior and west, and from
El Yunque into portions of the San Juan metro area, and the
municipalities of the north-central. Urban and small stream flooding
is likely in these areas.

On Friday night and Saturday, a tropical wave, currently located
well to the east of the Lesser Antilles, will reach the islands. The
moisture field of this wave stretches into the mid-levels of the
atmosphere. At the upper levels, a trough will be positioned to the
northeast of the islands, and this feature will increase instability
aloft. In fact, the 500 mb temperatures are expected to cool down,
while the mid-level lapse rates will increase. Some Saharan dust
will be mixed in with the wave too. The Galvez-Davison index also
show the potential for widespread showers, with heavy rain, and
thunderstorm. Taking all these factors into consideration, heavy
showers and strong thunderstorms are possible. The risk of frequent
lightning, gusty winds, and flooding will be present too.

The wave departs late on Saturday, and again, a dense Saharan Air
Layer will follow. Visibilities are expected to be reduced, and
skies will be hazy. However, at the low levels, trailing moisture
lingers. Therefore, it will not be dry, as some passing showers and
isolated thunderstorms are expected to move in at times across the
waters, the eastern half of Puerto Rico and the Virgin Islands.
Also, enough heating should trigger another round of strong
convection for the interior and west, where the risk for flooding
will be elevated.

&&

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

The latest models suggest the wet and unstable pattern will
prevail early next week. The Saharan Dust concentrations decrease
significantly. A TUTT low is forecasted to move north of our
region, inducing a surface perturbation. Also, the 500 mb
temperatures should remain cooler, around -7 to -8 degrees
Celsius. The high pressure across the Atlantic Ocean will weaken
somewhat, and low-level winds will become lighter on Monday and
Tuesday. With the proximity of the aforementioned TUTT low, those
other factors in place, and residual moisture from the departing
tropical wave (above-normal PWAT values; around 2 to 2.2 inches),
we can expect the development of showers and thunderstorms that
will likely generate frequent lightning, strong gusty winds, and
heavy downpours, and flooding concerns early next week. If the
rain materializes, lighter winds at the surface may result in
slow-moving showers, which are not beneficial for flooding
concerns. By mid-week, the surface high pressure across the
Atlantic will reinforce, winds should veer from the ESE and become
slightly stronger. That will continue to push tropical moisture
into our area. By Thursday, we should see some improvement in
weather conditions as models are showing patches of drier air
mixing and moving into our forecast area and a more typical
weather pattern may return.

In terms of temperatures, warmer-than-usual conditions are
expected for most of the period. On Monday, if the rain
materializes, the temperatures should stay a few degrees lower.
Generally, daytime highs will range from the lower 90s in lower
elevations to around 80 degrees in higher elevations. With
abundant moisture in the air, heat indices in coastal and urban
areas may soar above 108 degrees Fahrenheit.

&&

.AVIATION...
(06Z TAFS)

Passing SHRA are expected to continue to affect the USVI and TJSJ
terminals through the period. Hz due to Saharan dust is also
expected, but with VIS remaining at P6SM. After 16Z, SHRA and TSRA
are expected to develop in Puerto Rico, with periods of reduced
VIS and low ceilings anticipated for TJSJ and TJBQ. Mountain
obscuration is also expected for the Cordillera Central. Winds
will be from the ESE at 16-22 kts, and stronger gusts.

&&

.MARINE...

A surface high pressure across the Atlantic Ocean will promote
moderate to fresh easterly to east southeasterly winds through
Saturday night. A wind surge associated with a tropical wave will
arrive this afternoon, increasing moisture and convective activity.
The wave's axis will cross the region by Saturday, promoting
unsettled weather conditions throughout the weekend due to residual
moisture.

&&

.BEACH FORECAST...

There is a moderate risk of rip currents for most beaches of
Puerto Rico, Vieques, Culebra, and the U.S. Virgin Islands today
and tonight. The risk will likely remain moderate through the
weekend. For more details about the latest forecast, please refer
to the Surf Zone Forecast (SRFSJU).

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Sat Jul 13 2024

.SYNOPSIS...

A tropical wave and its moisture field will move across the
region leading to an increase in showers and thunderstorms
throughout the weekend. To start the next workweek, a TUTT will
approach the region enhancing instability and maintaining the wet
and unstable pattern in place through at least the first part of
the next workweek. An elevated heat risk as well as saharan dust
particulates will persist. A Small Craft Advisory is in effect for
the offshore Atlantic Waters, through this afternoon, and for the
Anegada Passage, through noon. Small Craft should still exercise
caution over most of the other local waters.

&&

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

A tropical wave and associated moisture field will continue to cross
the Lesser Antilles bringing an increase in showers and thunderstorm
activity across the region through the weekend. By Monday, a TUTT is
still forecast to cross the region from the east. This will enhance
instability and thus maintain a moist and unstable pattern through
the forecast period. Another extensive plume of Saharan dust will
trail the aforementioned tropical wave with elevated heat risk
likely to persist during the period.

Skies were partly cloudy to variably cloudy overnight with scattered
passing showers and isolated thunderstorms noted over the coastal
waters and local passages. Showers and thunderstorms continued to
quickly reach parts of the north and east coastal areas of the
islands, producing periods of moderate to locally heavy downpours and
brief gusty winds. Overnight low temperatures were in the upper 70s
to near 80 degrees along the coastal areas and in the upper 60s to
low 70s in higher elevations and valleys. Surface winds generally
from the east 5 to 10 mph.

For the rest of the day, the presence of Saharan dust along with the
increasing moisture and a mix of sunshine and clouds will aid in
maintaining hazy conditions in some areas. However, the potential
for shower and thunderstorm development will continue to increase
during the afternoon and into the evening hours as the tropical wave
approaches the region. Although convective development will not be
continuous over the islands, periods of enhanced afternoon
convection will be likely across the islands and coastal waters.
This in turn will lead to periods of locally heavy rains and moderate
to high potential for urban and small stream flooding in isolated
areas as well as rapid increase in water level and surges along
rivers and small streams.

For the rest of the period, lingering suspended Saharan dust
particulates is expected to continue across the region. This
along with trailing moisture from the tropical wave and the
presence of a retrograding Tutt will maintain unstable conditions
enhanced by the good heating each day. As a result, isolated but
strong afternoon convection will remain likely especially across
the central and west to northwest sections of Puerto Rico.

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

Humid and unstable conditions will be present to start the period.
A TUTT low will be north of our region on Tuesday while persistent
remnant moisture from the tropical wave from the short term period
will continue to push precipitable water (PWAT) values to above
normal, between 2.0 and 2.2 inches. At surface level, a high
pressure across the Atlantic will persist and promote light east to
east-southeast winds on Tuesday. Winds will increase, becoming
breezy, by the second half of the workweek. Patches of above normal
moisture will continue reaching the islands through midweek. The
TUTT low will move away from the region by Wednesday. Although some
saharan dust will linger, a more noticeable plume will approach the
islands by the second half of the workweek. More normal PWAT values
will be seen on Thursday. Current model guidance suggests another
upper low will approach the area on Friday, increasing instability.
Moisture will also gradually increase on Friday as a another
tropical wave and associated moisture move into the islands to end
the long term period. For Thursday, more typical weather with
passing showers in the morning and afternoon convection steered by
east to east-southeast winds. The other days in the period will have
more wet and unsettled weather due to the aforementioned features
and/or available tropical moisture. Warm conditions are still
expected for most of the period. Highs will be in the upper 80s to
around the low 90s in lower elevations of the islands. With
available moisture and east to east-southeast winds, heat indices in
coastal, urban and lower elevation areas can reach above 108 degrees
Fahrenheit.

&&

.AVIATION...

(06Z TAFS)

A tropical wave now crossing the Lesser Antilles will bring SCT
SHRA/ Isold TSRA across the area promoting brief MVFR/psbl IFR at
TIST/TISX/TJSJ with MTN Top Obscr psbl eastern Cordillera Central
til 113/14Z. Slight HZ will linger due to suspended Saharan dust,
but flight VIS should be plus 6SM. SHRA/VCTS ovr regional waters
and en route btw islands. SFC wnd will be fm the ENE btw 5 to 10
kts bcmg more easterly 12-15 kts with higher gusts and sea breeze
variations aft 13/14Z. Stronger gust likely w/Isold TSRA.

&&

.MARINE...

A surface high pressure across the Atlantic Ocean will promote
moderate to fresh easterly to east southeasterly winds through
tonight. Seas up to 7 feet are expected today across the offshore
Atlantic Waters and Anegada Passage. A tropical wave and associated
moisture field and wind surge will promote an increase in showers and
thunderstorm activity across the waters. The axis of the wave will
cross the region today, promoting unsettled weather conditions
throughout the weekend with its residual moisture. A TUTT will
approach the region to start the next workweek maintaining a moist
and unstable pattern.

&&

.BEACH FORECAST...

There is a moderate risk of rip currents for most beaches in Puerto
Rico, Vieques, Culebra, and the U.S. Virgin Islands. The risk
will start decreasing for several areas tonight through tomorrow.
For more details, please refer to the Surf Zone Forecast
(SRFSJU).

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
443 AM AST Sun Jul 14 2024

.SYNOPSIS...

An upper trough (TUTT) and associated induced low level trough
just northeast of the region will approach the area today through
Monday increasing low level moisture. Late morning showers are
possible along the north and east coastal areas, followed by
afternoon convection mainly over the central interior and west to
southwest sections of Puerto Rico. Surface winds will be from
the east- northeast today, becoming lighter from the east on
Monday then more southeasterly and increasing once again by
Tuesday as the trough retrogrades westward.

A mix of sunshine and clouds and the presence of the Saharan dust
will maintain hot, hazy and humid conditions with maximum heat indices
between 100 and 111 degrees or slightly higher in isolated areas
in the west and northwest coastal and urban areas. Saharan dust
will decrease through tomorrow, but another plume will reach the
area by midweek accompanied by more breezy winds.

&&

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

Upper trough (TUTT) and associated induced low level trough just
northeast of the region will approach the area today through Monday
bringing a quick surge of low level moisture. This will enhance
instability and thus maintain a moist and unstable pattern at least
until Monday. Surface wind will be from the east northeast becoming
lighter from the east on Monday then more southeasterly and
increasing once again by Tuesday as the trough retrogrades westward.
During the period a gradual warming trend is expected with
increasing humidity and the light to moderate east to south east
wind flow. As a result elevated heat risk likely to persist during
the period. In addition the extensive plume of Saharan dust
particulates will linger through Monday resulting in hazy
conditions, then diminishing by Tuesday, before another round
arrives later on in the week.

Impacts for today: Hot and humid conditions may produce maximum heat
indices between 100 and 111 degrees or slightly higher in isolated
areas in the west and northwest coastal and urban areas. Late
morning showers possible along the north and east coastal areas,
followed by afternoon convection mainly over the central interior
and west to southwest sections of Puerto Rico. Isolated
thunderstorms and locally heavy rains may lead to urban and small
stream flooding and in poorly drained areas. Dangerous lighting
likely with strong afternoon thunderstorms.

Skies remained partly cloudy to variably cloudy overnight with
mostly scattered passing showers noted over the Atlantic waters and
Anegada passage so far but no significant accumulations are so far
anticipated. Overnight low temperatures were in the upper 70s to
near 80 degrees along the coastal areas and in the upper 60s to low
70s in higher elevations and valleys. Surface winds were generally
from the east northeast at 5 to 10 mph.

A mix of sunshine and clouds and the presence of the Saharan dust
will maintain hot and hazy conditions with the potential for
afternoon shower and thunderstorm development. This will be focused
mainly over the central interior and southwest Puerto Rico with only
brief and isolated showers expected elsewhere. Periods of locally
heavy rains may lead to urban and small stream flooding in isolated
areas as well as rapid increase in water level and surges along
rivers and small streams across parts of Puerto Rico.

For the remainder of the period, lingering suspended Saharan dust
particulates will gradually diminish by Monday but the approach of
the TUTT from the east will maintain unstable conditions and this
will provide sufficient instability for some early morning and afternoon
convection on Monday and Tuesday. Widespread afternoon convection
is not anticipated. However,locally heavy rains and isolated
thunderstorms will remain possible each day. Therefore the chance
of minor urban and small stream flooding will persist in isolated
areas mainly over the central interior and west sections of Puerto
Rico steered by the local low level winds.

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

No major changes to the long term forecast. A TUTT low will be
north of our region to start the period while persistent tropical
moisture will continue to push precipitable water (PWAT) values to
above normal, between 2.0 and 2.2 inches, on Wednesday. At
surface level, a high pressure across the Atlantic will persist
and promote increasing east to east-southeast winds, becoming
breezy by the second half of the workweek. The TUTT low will move
away from the region by late Wednesday. A Saharan Air Layer (SAL)
will approach the islands by Wednesday morning, prompting hazy
skies and decreased air quality through at least Thursday. More
normal PWAT values will be seen on Thursday. Current model
guidance suggests another upper low will approach the area on
Friday and persist through the end of the period, increasing
instability. Moisture will also gradually increase on Friday as a
another tropical wave and associated moisture move into the
islands by late Friday into early Saturday. PWAT values should
return to around normal by late Saturday afternoon. For Thursday,
more typical weather with passing showers in the morning and
afternoon convection steered by east to east- southeast winds. The
other days in the period will have more wet and unsettled weather
due to the TUTT, wave and/or available tropical moisture. Maximum
temperatures will be in the upper 80s to around the low 90s in
lower elevations of the islands. The Saharan dust can also inhibit
nighttime cooling, prompting warmer than normal nights. With
available moisture and east to east-southeast winds, heat indices
in coastal, urban and lower elevation areas can reach above 108
degrees Fahrenheit.

&&

.AVIATION...

(06z TAFs)

VFR conds thru fcst prd. Wdly SCT SHRA ovr regional waters en
route btw islands. SCT ocnl BKn cld lyrs nr FL025...FL040. VCSH
psbl at TJSJ/TISX/TIST 14/09Z-14Z with very brief MVFR psbl due to
low cig/SHRA. Extensive plume of suspended Saharan dust will
remain across the area with HZ ALQDS psbl but Flight VIS fcst
P6SM. SFC wnd lgt/vrb but generally fm ENE btw 3-10 kts bcmg from
the ENE at 12-16 kts. SHRA/Isold TSRA fcst 14/17Z-22Z mainly ovr
Cordillera central and TJPS.

&&

.MARINE...

A surface high pressure across the western Atlantic will promote
light to moderate east to northeast winds. An upper trough and
associated induced low level trough just northeast of the region will
approach the area today through Monday increasing low level
moisture. Winds will become lighter from the east on Monday then more
southeasterly and increasing once again by Tuesday to become more
breezy by midweek (possibly prompting Exercise Caution statements by
that time). Hazy skies due to Saharan dust will continue through
today, gradually decreasing in the first half of the workweek and
then increasing again by midweek.

&&

.BEACH FORECAST...

For today and tonight there is a moderate risk of rip currents for
the coastlines of northwestern to north-central Puerto Rico, as
well as for the eastern half of St. Croix. Low risk elsewhere. The
risk of rip currents for the local coastlines is forecast to be
low tomorrow.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
456 AM AST Mon Jul 15 2024

.SYNOPSIS...
Tutt and induced low level trough will continue to cross the region
today trough Tuesday, with trailing moisture to affect the area as the
east northeast winds become more southeasterly by midweek. Hot, hazy
and humid conditions will persist with another extensive plume of
Saharan dust forecast to affect the region by mid week. Good daytime
heating along with local sea breeze variations and the proximity of
the upper trough will aid in enhancing afternoon shower and thunderstorm
development particularly across the interior and southwest sections
of Puerto Rico, as well as over the coastal waters and local passages
today.

&&

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

Current satellite derived precipitable water (PWAT) values indicate
a dry air mass approaching the region from the northeast. Lows last
night were in the upper 70s to low 80s at lower elevations and in
the upper 60s to low 70s in higher elevations and valleys. Surface
winds were generally from the east northeast at 5 to 10 mph. Showers
moved across the area during the overnight hours, leaving mostly
minimal accumulations over northern, interior and eastern Puerto
Rico since midnight. Radar estimated rainfall indicate up to 0.20 to
0.24 in at localized sectors of north-central and western interior
Puerto Rico since midnight.

Throughout the day, drier air will plummet available PWAT to below
normal values for this time of the year. PWAT values could even
decrease to 2 standard deviations below normal, around an inch. For
today, only patches of more humid air reaching the region, and
afternoon convection can promote local areas of more normal PWAT
values. Instability will be present, however, as a TUTT and an
induced surface trough continue to cross the region today through
Tuesday. Daytime heating, sea breeze convergence and these features
will aid in enhancing afternoon shower and thunderstorm development.
Surface winds will be from the east northeast veering and becoming
lighter from the east later in the afternoon. Winds will then
continue to veer to become east-southeasterly, while also
increasing, by Tuesday and Wednesday as the trough retrogrades
westward and a surface high-pressure continues to builds over the
central Atlantic. Current model guidance indicate PWAT values
increasing and reaching above normal values, above 2 inches, by late
Tuesday morning and persisting throughout most of the period.
Afternoon showers and thunderstorms today will concentrate over the
interior to the southwestern quadrant of Puerto Rico. For tomorrow
and Wednesday, afternoon activity should focus mainly on the
northwestern quadrant of Puerto Rico as steering winds become more
east-southeast. The risk of minor urban and small stream flooding
will persist in isolated areas mainly over the central interior and
west sections of Puerto Rico steered by low level winds. Patches of
moisture and showers will affect some windward sectors of the
islands during the overnight to morning hours each day.

Lingering, but overall decreasing, Saharan dust will be present
today and tomorrow. However, a more prominent Saharan Air Layer
(SAL) will approach the islands by Wednesday morning, prompting hazy
skies and decreased air quality to end the short term period.
Aerosol Optical Depth (AOD) values can reach around 0.40. This can
exacerbate respiratory conditions in immunocompromised, vulnerable
and sensitive groups. Maximum temperatures will be in the upper 80s
to around the low 90s in lower elevations of the islands. The
Saharan dust can also inhibit nighttime cooling (especially with
more prominent dust like on Wednesday), prompting warmer than normal
nights. Heat indices in coastal, urban and lower elevation areas can
reach above 108 degrees Fahrenheit. This will be further exacerbated
by east-southeast winds from tomorrow onwards. Hot temperatures and
high humidity may cause heat illnesses.

.LONG TERM...Thursday through Tuesday...
Recent model guidance suggests a strong surface high pressure will
remain anchored across the Atlantic and north of the region to
maintain moderate to strong east southeast winds on Thursday. Winds
are then to become more east northeast by Friday into the following
weekend as a tropical wave will enter the eastern Caribbean and
cross the forecast area. This is expected to bring increasing
moisture and instability to the region along with a wind surge and
moderate to strong southeasterly winds by Saturday afternoon, as
the tropical wave crosses the region. Accompanying the wave and
thereafter another extensive plume of dense Saharan dust is forecast
to quickly spread across the region Sunday through Monday then
gradually diminish from Tuesday onwards. By then winds are to become
more easterly with yet another Tutt and induced surface trough
forecast to approaches from the east.

All in all the most impactful period will so far be late Thursday
through Saturday, when enhanced overnight and afternoon convection
is expected due to the tropical wave along with good moisture
convergence and cooler advective temperatures aloft. This will be
followed by hazy/dusty conditions and a somewhat drier airmass
due to the forecast dense Saharan dust particulates which will
maintain hot and humid conditions. Temperatures are expected to
continue slightly above normal and elevated to significant maximum
daytime heat indices are forecast to be reached at times in some
coastal and urban areas. Marine conditions area also expected to
deteriorate by Friday and into the weekend due to the tropical wave
and the increasing trade winds. Therefore precautionary statements
and small craft advisories may be required for all or portions of
the local waters and passages by that time.

&&

.AVIATION...
(06z TAFs)

Mainly VFR conditions across the terminals. Winds will be ENE, bcmg
E later in the afternoon then ESE by tomorrow. VCSH AND VCTS are
forecasted for the interior and SW PR, including TJPS, at around
15/17Z-22Z. This can promote brief MVFR conditions. Brief VCSH
across other terminals possible during the period. Lingering but
decreasing saharan dust present, visibility P6SM.

&&

.MARINE...
Surface high pressure across the western Atlantic will promote
light east to northeast winds today, then become more southeasterly
and increase to moderate on Tuesday and become breezy by midweek
due to the arrival of a tropical wave and accompanying wind surge.
As the wind increases, choppy seas will be likely across the local
waters and passages, resulting in seas up to 7 feet and winds up
to 20 knots. Small craft advisories and precautionary statement
will be required by then.

&&

.BEACH FORECAST...
The rip current risk will be low today, however life-threatening
rip currents often occur in the vicinity of groins, jetties and
piers. By Tuesday and for the remainder of the workweek, there
will be a moderate risk of rip current for most beaches and
therefore life-threatening rip currents will be possible in the
surf zone.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
531 AM AST Tue Jul 16 2024

.SYNOPSIS...
Tutt and associated low level trough will continue to cross the
region today. Fragments of trade wind moisture will affect the area
as the low level winds become more east southeast then southeasterly
by Wednesday. Hot and humid conditions will continue the rest of the
period with an elongated plume of Saharan dust forecast to affect
the area into the upcoming weekend promoting hazy skies. Good daytime
heating along with local sea breezes and the proximity of the upper
trough will aid in enhancing afternoon shower and thunderstorm development
each day. A tropical wave will bring additional moisture and instability
to the islands Friday through Saturday. Breezy conditions with moderate
to locally strong east to southeast winds will return to the region
by Wednesday and continue into the weekend.

&&

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

Current satellite derived precipitable water (PWAT) values indicate
a dry air mass over the region. Overnight minimum temperatures were
in the upper 70s to low 80s at lower elevations and in the upper 60s
to low 70s at higher elevations. Steering winds gradually veered to
become east-southeast. Showers moved across the area during the
overnight hours, leaving mostly minimal accumulations over eastern
Puerto Rico, Vieques and St. Croix since midnight. Radar estimated
rainfall indicate up to 0.68 to 0.95 inches at sectors of Ceiba
since midnight.

A TUTT low will linger north of the region today while moisture
gradually increases. More normal PWAT values will be seen late this
morning. A patch of moisture related to an induced surface trough
will increase PWAT values to above normal, above 2 inches, this
evening and tomorrow. The presence of these features will promote
instability, and, alongside with daytime heating, sea breeze
convergence and local effects, will aid in enhancing afternoon
shower and thunderstorm development. Afternoon showers and
thunderstorms today will concentrate over the northwestern quadrant
of Puerto Rico, as well as possibly downwind of El Yunque. Surface
winds will generally be from the east-southeast during the period,
increasing to become more breezy for the second half of the
workweek, as the upper trough retrogrades westward and a surface
high-pressure continues to builds over the central Atlantic. Model
guidance suggest PWAT values staying at normal values for Thursday.
Patches of moisture, showers and potential t-storms will affect
windward sectors of the islands. Strong showers and thunderstorms
can lead to periods of heavy rainfall that will cause urban and
small stream flooding.

Lingering Saharan dust will be present today. However, a more
prominent Saharan Air Layer (SAL) will approach the area by tomorrow
morning, prompting hazy skies and decreased air quality for the rest
of the short term period. Aerosol Optical Depth (AOD) values can
reach around 0.40 to 0.55. Highs will be in the upper 80s to around
the low 90s in lower elevations of the islands. The Saharan dust can
also inhibit nighttime cooling (especially with more prominent dust
like on Wednesday), prompting warmer than normal nights. Heat
indices in coastal, urban and lower elevation areas can reach above
108 degrees Fahrenheit in part due to east-southeast winds and
available moisture.

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

Strong surface high pressure will remain the dominant feature across
the Atlantic and north of the region. This will maintain moderate
east to northeast winds Friday into Saturday while a tropical wave
will enter the eastern Caribbean and cross the forecast area. This
is expected to bring increasing moisture and instability to the
region along with a wind surge and moderate to strong southeasterly
winds by Saturday afternoon and on Sunday, as the tropical wave
exits the region. Accompanying and trailing the wave is an
extensive plume of dense Saharan dust which will quickly spread
across the region the rest of the weekend through Monday before
diminishing from Tuesday onwards. Winds are then to become more
easterly while another Tutt and induced surface trough approaches
from the east. Hot,humid and hazy conditions will likely persist
through the weekend.

Model guidance continued to initialize fairly well so far and still
suggests the most impactful period to be Friday through Saturday due
to increasing moisture convergence and instability with enhanced
overnight and afternoon convection expected due to the tropical wave
and cooler advective temperatures aloft. This will be followed by
hazy conditions as mentioned and a drier airmass due to the dense
layer of Saharan dust particulates which will maintain unseasonably
hot and humid conditions. Local temperatures are expected to continue
above normal with maximum daytime heat indices forecast to be elevated
to significant at times especially along the coastal and urban areas.
Marine conditions area also forecast to deteriorate Friday and into
the weekend due to the tightening of the local pressure gradient
and a wind surge which will increase the trade winds. Precautionary
statements and small craft advisories may be required for all or
portions of the local waters and passages through Saturday.


Sunday through Monday are expected to improve with typical summer
time weather and hot and hazy conditions. So far only isolated to
scattered locally and diurnally afternoon convection expected mainly
over the west and northwest sections of Puerto Rico. By late Monday
through the rest of the period, the upper ridge will erode as a Tutt
low is forecast to retrograde across the region and low level
moisture gradually increases. This in turn will increase the chance
for more frequent overnight passing showers and afternoon convection
across parts of the islands.

Otherwise based on the tropical weather outlook for the National
Hurricane center... Tropical cyclone formation is not expected
during the next seven days.


&&

.AVIATION...
(06Z TAFS)

Mainly VFR conditions across the terminals. Winds will be ESE. VCSH
and VCTS are forecast for the interior and NW PR, including TJBQ, at
around 16/17Z-22Z. Streamers can also affect TJSJ at that time. This
can promote brief MVFR conditions. Brief VCSH across other terminals
possible during the period. Lingering saharan dust present,
visibility P6SM.

&&

.MARINE...
A surface high pressure centered across the west central Atlantic and
an upper trough and associated induced low level trough crossing the
region will maintain a light to moderate east to southeast wind flow
with occasional passing showers across the local waters and passages.
Winds will become more southeasterly and increase to moderate to locally
fresh by Wednesday becoming breezy and thus creating choppy conditions.
Small craft operators should exercise caution across the offshore
waters and local passages today.

&&

.BEACH FORECAST...
There will be a moderate risk of rip current for most beaches and
therefore life- threatening rip currents will be possible in the
surf zone.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
530 AM AST Thu Jul 18 2024

.SYNOPSIS...Saharan dust and very warm temperatures will appear
again today with Excessive heat warnings for most lower elevations
and a heat advisory for the northern U.S. Virgin Islands. Showers
and thunderstorms are expected each day, but will increase with
the passage of tropical waves Friday afternoon into early
Saturday, Sunday night and Wednesday. Stronger winds will bring
moderate rip current risk to most beaches, and a high risk to
Saint Croix Friday through Saturday.


&&

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

Current satellite derived precipitable water (PWAT) shows gradually
eroding moisture across the islands, values at normal to locally
slightly above normal were observed over the region. A Saharan Air
Layer (SAL) continues to move into the region from the east.
Overnight minimums were in the upper 70s to low 80s at lower
elevations and in the upper 60s to low 70s at higher elevations of
Puerto Rico. Since midnight, radar estimated rainfall shows
accumulations at northern, eastern and southeastern Puerto Rico, as
well as over Vieques, Culebra, and the USVI.

The dense SAL will continue to promote a moderate to severe dust
event, prompting hazy skies and decreased air quality. These
conditions can exacerbate respiratory conditions in
immunocompromised, vulnerable and sensitive groups. Pulses of
Saharan Dust will continue to arrive through the rest of the week.
However, concentrations are expected to decrease by tomorrow due to
the arrival of a tropical wave and its associated moisture field.
Dust concentrations will increase again on Saturday. Warmer than
normal conditions will persist through the period. Daytime maximum
temperatures will be in the upper 80s to around the low 90s in lower
elevations of the islands. Saharan dust will also inhibit nighttime
cooling, prompting warmer than normal nights. Heat indices in
coastal, urban and lower elevation areas can reach above 108 degrees
Fahrenheit.

In the mid to upper levels, a ridge continues to build across the
area as the TUTT low that affected us this week continues to move
north and away from the region and another TUTT stays well east-
northeast of the region during the short term period. A strong
surface high pressure across the west central Atlantic will promote
breezy easterlies today, with sea breeze variations and higher
gusts. PWAT values will be at normal values today through early
tomorrow. As the breezy winds become more southeasterly tomorrow,
the moisture field from the tropical wave will increase instability
and push PWAT values to above normal, above 2 inches, by late Friday
morning through early Saturday. This wave will increase shower with
thunderstorm activity across the islands as it moves through. By
Saturday, moisture will gradually erode as dust concentrations
increase. Daytime heating, sea breeze convergence and local effects
will promote afternoon shower and thunderstorm development today,
mainly over western Puerto Rico. Some convective activity can
develop and move from the local islands to eastern PR. Patches of
moisture, showers and potential t-storms will affect windward
sectors of the islands, especially when enhanced by the tropical
wave. Strong showers and thunderstorms can lead to periods of heavy
rainfall that will cause urban and small stream flooding.

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

High pressure at upper levels will dominate the long term period.
Some tropical waves are expected to move through the area
specifically Sunday night and Wednesday. The last tropical wave
will have a wind surge behind it. This surge will be most
prominent at 700 mb however.

Showers and thunderstorms are expected each day in the typical
diurnal pattern for the islands. Overnight and morning showers
are likely most days in eastern Puerto Rico, while afternoon
thunderstorms will be the rule over western and interior Puerto
Rico. Owing to the quasi station surface high over the western
Atlantic, easterly flow will prevail each day. Some thunderstorms
may be intense, but overall relatively stable conditions will
exist and precipitable water will range from 1.2 to 2.0 inches as
the waves pass through. This will represent a decrease from the
values expected Friday through early Sunday in the short term
period.

Some days will see some warm--if not-record warm--minimum
temperatures when winds turn northeasterly early next week. This
will boost the heat indices during the day, but should minimize
the chances of record high temperatures.

&&

.AVIATION...
(06Z TAFS)

Mainly VFR conditions across the terminals. Winds will be mainly
from the E at up to 12 to 18 kts from 18/13Z with sea breeze
variations and higher gusts. Afternoon TSRA/SHRA are forecast for
the interior to W PR, which can affect TJBQ/TJMZ, at around
18/17Z-22Z. This can promote brief MVFR conditions. Brief VCSH
across other terminals possible during the period. HZ across the
terminals with increasing Saharan Dust today reducing
visibilities.

&&

.MARINE...Seas will begin to rise with the increase in winds.
Small craft advisories are expected in various waters beginning
tonight and extending into Saturday night. Winds in the Outer
Atlantic waters and the Anegada passage could approach 25 knots
sustained with some extending into the nearshore waters of the
northwest coast where winds are usually strongest. Winds will
increase again later next week.

&&

.BEACH FORECAST...Moderate rip currents are expected at many
beaches, but there will be a high risk of rip currents in Saint
Croix Friday through Saturday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
508 AM AST Fri Jul 19 2024

.SYNOPSIS...A tropical wave is moving through the U.S. Virgin
Islands and will be over the Mona Channel before midnight tonight.
After showers and thunderstorms associated with the wave, Saharan
dust will return until Sunday. A weak wave and some moisture will
pass through on Monday. This modest moisture will continue
through the end of the week with the typical diurnal pattern.

&&

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

A variable weather pattern was observed over the night and early
morning, with continued moderate to strong passing showers affecting
the local waters and streaming across the eastern coastal areas of
Puerto Rico, Culebra, Vieques, and the U.S. Virgin Islands. Strong
showers dragged by the breezy conditions moved farther inland,
affecting the Metro area of San Juan and the vicinity of Caguas.
Although shower activity was persistent, rainfall accumulations were
not impressive due to the velocity of the translation of the
showers. According to the Doppler radar, Vieques registered almost
an inch of rain during the period. The islands observed temperatures
in the upper 70s to the lower 80s across the coastal and urban areas
and in the low to mid-70s in the mountains.

Today, a variable to deteriorating weather pattern is forecast with
an upper-level trough and a tropical wave with the axis over the
U.S. Virgin Islands. It will move over Puerto Rico today. The
surface feature will drag plenty of tropical moisture with PWAT
values of 2-plus inches, as shown in the derived imagery from the
GOES satellite. On the other hand, the instability aloft will
result in colder 500 MB temps, which is the best scenario for
vertical development of the showers and thunderstorms. Along with
the moisture, the tropical wave will result in breezy conditions
across the region, resulting in winds ranging from 15-20 mph, with
gusty winds near the strongest showers. As a result, the islands
will experience fast-moving showers for the rest of the day as
the tropical wave moves closest to the CWA. Isolated to scattered
thunderstorms are expected, with the heaviest activity in the
afternoon leading to periods of elevated flood threat across the
western interior and eastern sections of Puerto Rico. Therefore,
minor urban and low-lying flooding is expected, as well as rapid
small stream increases and ponding of water in poor drainage
areas. Residents and visitors are urged to keep updated with the
latest weather information.

From late Saturday into Sunday, a large area of dry air with a
significant pulse of a Saharan Dust Air Layer will filter in,
eroding all the available moisture. According to the NASA Goddard
Earth Observing System Model V5, the optical depth for this event of
Saharan dust will be in the 0.3 to 0.5 range, with the bulk in the
early hours of Sunday. The lack of moisture at the surface, with a
mid- to upper-level ridge, will enhance a stable weather pattern
with some pockets of moisture arriving in the easterly winds across
the islands. Therefore, the forecast calls for a seasonal pattern
with warm conditions, followed by limited afternoon convection and
hazy skies. People with respiratory conditions should follow the
recommendations provided by the local health departments.

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

High pressure at upper levels will continue to dominate the the
local islands and the eastern Caribbean even though the 500 mb
high remains closely located with the surface high over the
western Atlantic. The tropical wave is still expected later in the
day on Wednesday and will constitute one of the pulses of
moisture with precipitable water values of around 2 inches that we
will see Monday through Wednesday. Instability during the period,
however, will be modest until Friday of next week, although a few
thunderstorms are expected in western and interior Puerto Rico
each day. Moisture also will begin to diminish Thursday and
Friday weakening the showers that will form anyway because of
local island effects and strong heating.

&&

.AVIATION...
(06z)

Brief MVFR conditions might persist for the rest of the
morning hours across TJSJ, TIST, and TISX due to locally heavy SHRA
across the CWA. Winds will continue from the E at 10 knots with
gusty winds near the SHRA, becoming stronger at 19/15Z and
shifting more SE at around 19/19Z. VCTS and TSRA are expected
across nearly all the TAF sites due to the approach of a tropical
wave, resulting in lower ceilings in the FL015 and FL020 and gusty
winds. HZ is forecast beginning 20/06Z.

&&

.MARINE...Winds associated with a wind surge behind the currently
passing tropical wave will keep seas choppy and hazardous. Small
craft advisories will be in effect from today through at least
Saturday night. Conditions are expected to improve on Sunday, but
choppy conditions will persist.

&&

.BEACH FORECAST...A moderate risk of rip currents will be seen on
most of the beaches in the area. Saint Croix will have a high risk
of rip currents today through Saturday.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
455 AM AST Sat Jul 20 2024

.SYNOPSIS...

Exiting moisture from the previous tropical wave and another big
pulse of Saharan Dust Air Layer will mostly result in a warm
weather pattern across the region today. Although some showers
might persist during the morning hours across some coastal areas,
breaking clouds are forecasted by mid-morning leading the heat
indices to reach heat advisory criteria. As a result a Heat
Advisory is in effect from 10 AM to 5 PM across all the coastal
areas of Puerto Rico and the U.S. Virgin Islands. Similar
conditions are forecast for Sunday. Windy conditions would
maintain hazardous marine conditions for today.

&&

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

Quick moving showers moved across the region during the overnight
hours. These showers brought moderate to locally heavy rainfall and
wind gusts around 25 knots. Some lightning strikes were observed
near San Juan, and over the Caribbean waters. Rainfall accumulation
was light across the board.

Satellite-derived precipitable water imagery show a gradient of
moisture, with a moist air mass over Puerto Rico, and a drier air
one already reaching the Virgin Islands. The aerosol models show a
significant Saharan Air Layer also reaching the area, so skies will
be hazy. This particulate will last into tomorrow, gradually
clearing out late Sunday and Monday. With less clouds and rain
activity than yesterday, temperatures will soar once again, with
dangerous heat indices anticipated. People are advised to stay
hydrated and to take break from the sun, especially with the air
quality deteriorated due to the Saharan dust.

A surface high pressure centered north of the islands will also
maintain the steering flow enhanced, with winds coming out of the
east southeast at 20 to 25 mph, and stronger gusts. Even with the
drier air mass, some showers will move through, and some activity
could develop in the afternoon. Strong heating could lead to some
thunderstorms as well. Tomorrow, the ridge will be stronger, and a
trade wind cap inversion is expected to develop at 800 mb.
Therefore, the potential for showers will significantly decrease.

On Monday, with the Saharan dust departing, some moisture will
filter in from the east. In fact, precipitable water values are
expected to be above normal, so showers will increase once again.
The low level winds will weaken some, but will remain from the east
at around 15 knots. As it is usual with this event, the morning
activity will be favored across eastern Puerto Rico and the Virgin
Islands, while stronger convection should fire up in the interior
and west in the afternoon hours, where the risk for urban and small
stream flooding will be elevated.


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

A seasonal pattern will be in place for the beginning of the long
term. At the surface, broad high pressure will dominate the Atlantic
Basin, including the Caribbean, resulting in easterly winds across
the region. Embedded in the wind flow, patches of shallow moisture,
with PWAT around 1.7 to 2 inches, will move in and out of the area
from Tuesday through Wednesday. Under this pattern, the islands will
primarily experience the typical weather pattern with variable
mornings between warm conditions and some isolated showers, followed
by afternoon convection over the western interior sections of Puerto
Rico. From late Wednesday into early Thursday, a slot of drier
airmass will move in but not last long, as a wind surge reaches the
islands, increasing the sustained surface winds and the potential
for shower development. Combining the wet pattern on Thursday, model
guidance indicates some instability provided by the divergence side
of an upper-level trough of an upper-low just over the western
Atlantic. The outcome will be a more favorable scenario for more
widespread shower activity. However, given the windy conditions,
fast-moving showers might not accumulate significant rainfall in
most areas.

After that wind surge, the NASA Goddard Earth Observing System Model
V5 suggests another round of a Saharan Dust event. Similar to the
past week's event, this will be moderate, with optical depth
concentration between 0.2-0.3. This pattern will erode most
available moisture, limiting the shower activity. For the same
period, the dominant feature will be the surface high pressure just
over the Central Atlantic, resulting in an east-southeasterly wind
flow. As usual during the summer days in Puerto Rico and the U.S.
Virgin Islands, warmer conditions with Saharan Dust particles will
increase heat index values across the region. Excessive heat
products are forecasted for those days.

&&

.AVIATION...
(06Z TAFs)
Quick moving SHRA will continue through 18Z for the local
area, with gusts around 15-25 kts. Saharan dust will reach the USVI
terminals this morning, stretching into the PR terminals after 14Z,
but VIS will remain P6SM. TSRA expected after 18Z near TJBQ, with
brief reduction in VIS and low ceilings. FL050 will be from the SE
at around 20 kts.

&&

.MARINE...
A broad surface high pressure over the Central Atlantic will
continue to promote moderate to locally fresh easterly winds across
the local waters, resulting in choppy seas. As a result, several
small craft advisories will remain in effect until 6 PM today. For
tonight, winds will diminish to 10-15 knots for the rest of the
period. Afternoon convection over the Mona Channel might result in
localized hazardous marine conditions each day.

&&

.BEACH FORECAST...
Windy conditions provided by surface high pressure over the Central
Atlantic will promote breezy conditions across the coastal areas of
the islands. These conditions might turn choppy at the beach,
occasionally resulting in slightly higher seas. There is a high risk
of rip currents for St. Croix beaches, but a moderate risk of rip
currents will be present for other areas.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
417 AM AST Sun Jul 21 2024

.SYNOPSIS...

Hazy skies will persist during all the day. Warmer conditions are
forecasted for today, as a result a Heat Advisory is in effect
from 10 AM to 5 PM across all the coastal areas of Puerto Rico and
the U.S. Virgin Islands. A wind perturbation will arrive to the
islands tomorrow, increasing the shower activity once again. The
next tropical wave will move across the islands by Thursday
increasing winds and the potential for shower activity.

&&

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

The night was very calm across Puerto Rico and the Virgin Islands. A
few showers did manage to develop late in the overnight hours, but
rainfall accumulations were little. It stayed warm, with lows in the
low 80s across coastal areas.

A surface high pressure over the western Atlantic maintains the trade
winds from the east northeast, at speeds around 15 to 20 knots, with
stronger gusts. A Saharan Air Layer will begin to clear out later in
the afternoon or evening hours, but until then, skies will be hazy.
A trade wind cap inversion at 850 mb will maintain conditions
hostile at the low and mid levels for strong showers to develop, but
some may still manage to form in the extreme southwest of Puerto
Rico, due to strong heating.

Tonight, a perturbation in the trade winds will reach the islands,
bringing an increase in showers to the region. Accumulations are not
expected to be too significant, but enough to cause ponding of water
on roadways along eastern Puerto Rico and the Virgin Islands, and
with an elevated potential for flooding in the west. Conditions will
be drier on Tuesday, but enough lingering moisture should fire up
more showers and thunderstorms for the western portions of Puerto
Rico.

Temperatures will continue to run above normal, and with plenty of
moisture, it will feel muggy. Elevated heat indices are anticipated.
With these levels of heat, everyone without effective cooling or
adequate hydration will be affected. There could be some impacts to
health systems and to industries sensitive to heat.

.LONG TERM...Wednesday through Sunday

A variable weather pattern is forecast for the first part of the
long term. At the upper levels, some influence from the divergent
side of an upper-level trough just over the western Atlantic will
result in some instability across the local region from Wednesday
into early Friday. At the surface, a broad high pressure will
dominate the Atlantic Basin, including the Caribbean, resulting in
easterly winds across the region. Embedded in the wind flow,
patches of shallow moisture, with PWAT around 1.7 to 2 inches,
will move in and out on Wednesday. Like yesterday's solutions,
model guidance continues to suggest the slot of drier airmass
moving into the region on Wednesday evening, followed by the wind
surge embedded with a tropical wave. Therefore, the islands will
be in a favorable scenario for widespread shower activity.
However, given the windy conditions, fast-moving showers might not
accumulate significant rainfall in most areas.

For Friday and Saturday, the NASA Goddard Earth Observing System Model
V5 suggests another round of a Saharan Dust event. Similar to the
past week's event, this will be moderate, with optical depth
concentration between 0.2-0.3. This pattern will erode most
available moisture, limiting the shower activity. For the same
period, the dominant feature will be the surface high pressure
just over the Central Atlantic, resulting in an east-southeasterly
wind flow. As usual during the summer days in Puerto Rico and the
U.S. Virgin Islands, warmer conditions with Saharan Dust
particles will increase heat index values across the region.
Excessive heat products are forecasted for those days.


&&

.AVIATION...(06Z TAFs)

Mainly VFR conditions expected to prevail. Passing isolated SHRA
will move near the USVI terminals and TJSJ, but without impacts to
operations. HZ due to Saharan dust will persist through at least
20Z, but with VIS at P6SM. Winds will be from the ENE at 18-23 kts,
with stronger gusts.


&&

.MARINE...
A broad surface high pressure over the Central Atlantic will
continue to promote moderate to locally fresh easterly winds
across the local waters, resulting in seas up to 5 feet and
occasionally up to 6 feet. As a result, small craft operators are
urged to exercise caution. By midweek, another tropical wave and a
wind surge will deteriorate the marine conditions again.

&&

.BEACH FORECAST...

Windy conditions provided by surface high pressure over the
Central Atlantic will promote some breezy conditions across the
coastal areas of the islands. There is a moderate to low risk of
rip currents for all the coastal areas today. For more beach
information, refer to weather.gov/sju/beachforecast.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
442 AM AST Mon Jul 22 2024

SYNOPSIS...
A low level perturbation is increasing the chance of rain for the
beginning of the workweek. The next tropical wave
will move across the islands by Thursday increasing winds and the
potential for shower activity once again with a thick Saharan Air
Layer arriving after, brining hazy and hot conditions for the end
of the week.

&&

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

The most recent satellite-derived precipitable water imagery show a
low level perturbation approaching the islands. This feature brought
early showers for the Virgin Islands and eastern Puerto Rico, with
even a thunderstorm developing northwest of St. Thomas and St. John.
This increase in shower activity will continue through the day, with
ponding of water expected to continue across eastern Puerto Rico and
the Virgin Islands. In the afternoon, showers should cluster across
the interior and western Puerto Rico, where the risk of flooding
will be elevated.

At the surface, a high pressure over the central Atlantic will
maintain the wind flow from the northeast. The gradient is still
tight, but not as much as yesterday, so winds will be from the east
southeast at 15 to 20 mph. These winds will continue to carry
patches of moisture into the region, especially on Wednesday, when
another plume of moisture should lift from the Caribbean Sea into
the region. Aside from the moisture, conditions aloft are not
particularly favorable for strong showers and thunderstorms to
develop, but there will be enough heating to repeat the afternoon
activity for western Puerto Rico.

It will be just a tad less hot today, but still in the upper 80s and
low 90s. This level of heat could affects those individuals
extremely sensitive to heat, especially when outdoors without
effective cooling or adequate hydration.

&&

LONG TERM...Thursday through Monday...

The arrival of a tropical wave on Thursday will bring showery and
windy conditions across the area. With surface winds prevailing
from the east, most of the rainfall will be seen across eastern
Puerto Rico during the day and then afternoon convection will
bring heavier rainfall to western sections. Following this wave, a
thick Saharan Air Layer will bring hazy and hot conditions
starting late Thursday into the weekend, before moist air arrives
along with a trade wind perturbation on Sunday. The worst of the
dust event may be on Friday, however high dust concentrations can
last through the weekend. Coastal areas are likely to experience
higher than usual maximum temperatures during this time.

&&

.AVIATION...

(06Z TAFs)

Passing SHRA expected through the period, especially for the USVI
and TJSJ terminals. After 16Z, SHRA and TSRA are expected for the
Cordillera Central and near TJBQ. Periods of reduced VIS and low
ceilings can be anticipated. Winds will be from the ESE at 15-19
kts, with stronger gusts.

&&

.MARINE...
A strong surface high-pressure across the Central Atlantic will continue
to promote moderate to fresh east to northeast winds for the next few days.
A trade wind perturbation and moisture field is increasing the
potential for showers and thunderstorms across the regional waters
today.

&&

.BEACH FORECAST...

Windy conditions provided by surface high pressure over the Atlantic
will cause choppy conditions across the coastal areas of the
islands causing a moderate risk of rip currents for most beaches.
Similar conditions should prevail for the next few days, for more
details about the latest forecast, please refer to
weather.gov/sju/beachforecast.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
430 AM AST Tue Jul 23 2024


.SYNOPSIS...

A seasonal pattern is expected with afternoon thunderstorms mainly
across western Puerto Rico. On Thursday a tropical wave and wind
surge will arrive. Following this, a Saharan Air Layer (SAL) is
expected by the end of the day on Thursday, bringing hazy and hot
conditions for the end of the week into the weekend.

&&

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

The small low level perturbation that moved across Puerto Rico and
the United States Virgin Islands yesterday moved out of the area.
Some lingering showers persisted in the night hours, but without
leaving significant accumulation. For today, a surface high pressure
continues to drive the trade winds from the east southeast, at
speeds of 15 to 20 mph, and stronger gusts. With drier air moving in
above 850 mb, moisture will be trapped close to the surface. These
winds and moisture will combine to generate lines of showers moving
from the Lesser Antilles into the vicinity of the Virgin Islands,
and from the Virgin Islands into eastern Puerto Rico. Additional
activity is anticipated over the interior and west, portions of the
north and the San Juan metro area. This activity may lead to urban
and small stream flooding. A similar pattern is anticipated for
Wednesday, with a little bit of Saharan dust filter in from the east.

On Thursday, conditions will begin to change. A tropical wave along
with a wind surge will arrive, bringing quick moving showers and
thunderstorms. This activity will come with winds of 20 to 25
mph, so aside from the rain and lightning, gusty winds can be
anticipated. The wave will depart quickly during the daytime,
followed by a very dense Saharan Air Layer, so conditions will
become very hazy once again.

&&

LONG TERM...Friday through Tuesday...

A thick Saharan Air Layer will bring hazy and hot conditions
through at least Sunday, with the worst concentrations expected
on Friday through Saturday. Rainfall will be minimal during the
first few days of the event, however the arrival of moist air
Sunday onward will increase the chance of rainfall, where
afternoon thunderstorms may form with the help of diurnal heating.
Expect pretty hot conditions with coastal areas experiencing
higher than usual maximum temperatures during this time. It is
likely that heat advisories or warnings will be issued, therefore
stay alert as we approach the end of the week. A significant
increase of rainfall is expected on Tuesday as the dust begins to
move out of the area and as a tropical wave approaches the region
by Tuesday night, breaking the drier spell that the Saharan Air
Layer brought the days before.

&&

.AVIATION...

(06Z TAFs) Mainly VFR conditions expected to prevail through the
forecast period. SHRA will continue to move across the local waters,
but without significant impacts to operations. After 17Z, additional
SHRA expected to develop around TJSJ and TJBQ, with periods of
reduced VIS and low ceilings. Winds will be from the ESE at 17-22
kts, with stronger gusts.

&&

MARINE...

A strong surface high-pressure across the Central Atlantic will continue
to support moderate to fresh easterly winds and choppy seas for the
next few days. Unstable weather conditions and sufficient moisture
content will promote shower and thunderstorm activity across the
regional waters for the next few days, particularly across coastal
waters of western Puerto Rico each afternoon.

&&

BEACH FORECAST...

Choppy conditions will continue across the coastal areas of the
islands for the next few days. This will result in moderate risk
of rip currents for most beaches. For more details about the
latest forecast, please refer to weather.gov/sju/beachforecast.