Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
420 AM AST Mon Jul 19 2021

.SYNOPSIS...

Drier air is moving into the region from the east, in the wake of
the wave yesterday. More stable weather conditions are likely during
the day today, though there will remain sufficient moisture to
sustain some shower activity. Additionally, there is a Saharan
Air Layer that is part of this drier air mass, and hazy skies are
likely. Increasing patches of near-normal moisture are expected
for midweek into the end of the week, and increasing shower
activity is anticipated.

&&

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

A mid-level ridge and a Saharan Air Layer will promote drier
conditions and hazy skies across the region through most of the
short term period. At lower levels, east to southeast trade winds
are expected to continue through Tuesday. Patches of moisture
embedded in this wind flow will move at times across the region.
Therefore, a few passing showers can be expected across the U.S.
Virgin Islands and the eastern sections of Puerto Rico during the
night and early morning hours, followed by diurnally induced
streamers off the islands and shallow shower development over the
western sections of PR each afternoon. However, no significant
rainfall accumulations are anticipated at this time.

For Wednesday, a TUTT-induced low-level trough is expected to
move from the east, increasing moisture content and causing winds
to shift from the east to northeast. This will promote an increase
in night time and early morning showers across the northeastern
sections of PR and over the USVI. Showers with better vertical
development than previous days are expected to form over the
southwestern quadrant of PR.

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

On Thursday, there will be patches of near-normal moisture streaming
across the area from time to time. This will support a typical
pattern of showers through the day, though rainfall amounts will
likely be relatively low. Forecast confidence for Thursday is
moderate to high.

To the east, a tropical wave is expected to break Thursday into
Friday, then make its way into the region on Friday into Saturday.
Model guidance shows a further decrease in how well this feature
holds together, and with how much moisture makes its way to the
local islands, continuing the trend from yesterday. As such, the
forecast continues to back off on expected shower activity. However,
moisture is still likely to increase Friday into early Saturday,
which will have a correlated increase in shower activity. Troughing
in the mid- to upper-levels will also decrease stability over the
region, which will also act to increase somewhat the potential for
showers. During the day on Saturday, the wave is forecast to have
moved out of the region, and moisture will decrease in its wake.
Precipitable water values are forecast to be on the low end of
seasonal normals, or slightly below. Very dry mid-levels will also
act to inhibit shower activity. Still, some showers are expected.
Forecast confidence for the end of the week is low to moderate.

Another wave is forecast to approach the region during the beginning
of next week. As with previous forecasts, how far north this wave
tracks remains uncertain, though model guidance has continued to
push it further north. This does seem reasonable, considering
weakness in the ridge to the north, which is forecast to be pulling
away to the northeast at the time. On the whole, the trend is
towards increasing showers for Sunday into Monday. Dry air makes its
way into the region for late Monday into Tuesday behind the wave,
and more stable conditions are expected. Confidence in the general
trend of the forecast for next week is moderate to high, but
confidence in the details is low.

&&

.AVIATION...

Mainly VFR conditions expected across all terminals
during the next 24 hours. HZ due to Saharan dust expected to
continue, but VSBY should remain P6SM. East to southeast winds will
increase around 15 kt with sea breeze variations and higher gusts
aft 14z.

&&

.MARINE...

Choppy conditions continue today into tomorrow, associated with
moderate to fresh, and locally strong easterly winds behind the
tropical wave that has exited the region. Sustained winds of up to
22 knots are expected, and seas up to 6 feet. Winds will gradually
diminish into midweek this week, and seas will subside.

There is a moderate risk of rip current for nearly all local
beaches, with some exceptions along the southern west coast and the
south central coast of Puerto Rico.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 77 89 78 / 20 10 20 20
STT 91 80 88 78 / 20 20 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
426 AM AST Tue Jul 20 2021

.SYNOPSIS...A Saharan Air Layer (SAL) will continue to promote
hazy skies through at least today. A TUTT induced trough will move
briefly on Wednesday, increasing the chances for shower activity.
Another area of SAL is expected to move across the region during
the second part of the workweek. A weak tropical wave is expected
to move across the region on Friday, briefly increasing shower
activity. Another tropical wave, with more moisture content is
expected during the weekend.


&&

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

A Saharan Air Layer remains in place over the region, bringing
hazy skies and generally calm weather. Diurnal and local effects
will still cause some shower activity, mostly in northwestern and
interior Puerto Rico, with some streamers off of orographic features
in the east. Minimal rainfall accumulations, less than a tenth of
an inch, are expected.

On Wednesday, an increase in moisture is expected, largely due to
the influence of an induced trough in the lower levels, associated
with the Tropical Upper Tropospheric Trough (TUTT). However, this
additional moisture remains fairly patchy in nature, and precipitable
water values are forecast to fluctuate between 1.3 to 1.4 inches
and 1.6 to 1.8 inches - so, from below seasonal normals to near-normal.
An increase in shower activity is expected, but convection will
remain limited, with the drier air persisting in the mid-levels.
The combination of unfavorable conditions due to the dry air aloft
and the fact that the moisture will not be consistent across the
area or day, will limit the potential for significant rainfall
amounts.

More dry conditions are expected by Thursday morning, and another
round of Saharan dust makes its way into the region. Hazy skies are
expected, and inhibited shower activity is likely. However, moisture
is forecast to increase later in the day, especially after mid-afternoon,
due to the approach of a tropical wave from the east. Increasing shower
activity is therefore likely during the afternoon, evening, and into
the night. Even so, rainfall totals are not likely to be very high
by the end of the short term period.

Forecast confidence is high. Total precipitable water imagery from
GOES-16 shows a large area of generally drier air to the east.
With the Dust RGB, there is significant coverage of dust
particulates over the eastern Atlantic. As such, there is high
confidence in the continuation of dry air (and dust at times) in
the mid- levels, which will inhibit the showers. The expectation
for limited, patchy moisture is also reasonable.

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

A tropical wave currently near 45W is expected to reach the area
by Friday. This wave will promote a small surge of low-level
moisture to aid in the development of early morning showers
between the USVI and eastern PR, followed by afternoon convection
over western PR. However, widespread shower activity is not
expected due to the presence of a Saharan Air Layer. During the
weekend, a TUTT low is currently forecast to move over or close
to Hispaniola, while another tropical wave streams across the
region between Saturday and Sunday. If the forecast holds,
shower and isolated thunderstorm development will increase for
both days across the regional waters and over portions of the
islands.

For Monday and Tuesday, the area is expected to remain under the
subsidence/convergent side of a retrogressing TUTT low from the
central Atlantic. In addition, another SAL is forecast to reach
the local area. This will cause precipitable water content to
drop and limit shower development across the islands. However,
shallow convection is expected mainly over the southwest quadrant
of PR each afternoon due to diurnal and local effects, and as
steering winds shift from the northeast in response to the
approaching TUTT.


&&

.AVIATION...Generally VFR conditions are expected across most
terminals for next 24 hours. MVFR overnight for TIST/TISX, due to
ceilings, improving in the morning. Dry, hazy conditions
continue, limiting SHRA activity; significant operational impacts
not expected at terminals. Winds picking up out of the east by
20/14Z at 10 to 15 knots, with sea breeze variations and stronger
gusts. Winds decrease again around 20/22Z-21/01Z, becoming
generally light.


&&

.MARINE...A surface high pressure northeast of the region will
gradually move further into the central Atlantic during the next
few days. This will promote a moderate to locally fresh trade
wind flow across the regional waters. Choppy seas up to 6 feet are
expected across the offshore Atlantic and Caribbean waters, and
across the Mona Passage today. There is a moderate risk of rip
currents for most of the beaches of PR and the USVI.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 78 89 77 / 20 20 30 20
STT 89 78 89 78 / 20 30 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
502 AM AST Wed Jul 21 2021

.SYNOPSIS...A weak low-level trough will increase moisture content
today. However, drier mid-level air and a lingering Saharan Air
Layer will continue over the area for the next day or so. A
stronger SAL is expected on Friday, and at the same time a weak
tropical wave will stream across the area. For the weekend, an
upper level low over Hispaniola and another tropical wave will
promote more favorable conditions for shower and thunderstorm
activity across the islands.


&&

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

Brisk winds continue over the region, associated with tight
pressure gradient induced by ridge over the central Atlantic.
Aloft, an upper- level trough is located to the north and west of
the region, providing slightly more favorable conditions for
shower development. However, there remains dry air at the mid-
levels, which will inhibit deep convection. Increasing moisture is
moving into the region from the east, with an induced low-level
trough. This moisture is evident on satellite imagery, including
the Total Precipitable Water imagery from GOES-16. There has been
an increase during the night in the amount of trade wind showers
over the local waters as this moisture approached. Increased
shower activity is expected during the day today, in a typical
pattern. However, significant, organized convection is unlikely.
Showers are expected for southwestern and interior Puerto Rico.
Rainfall amounts are likely to be relatively low.

Drier air is expected for tomorrow. There remains very dry air in
the mid-levels, and some additional dust is likely. Convection
will be suppressed, and shower activity decreased. Still, local
effects and daytime heating will cause some afternoon showers over
northwestern and interior Puerto Rico, with some streamer activity
possible in the east.

On Friday, conditions will become more favorable for showers.
A trough at the upper mid-levels will aid in the generation of
instability, and the vertical extent of moisture is likely to
increase. Additionally, moisture is likely to increase later in
the day, as a tropical wave approaches from the east. However,
also at the mid-levels, there is a persisting dry layer, and
another surge of dust looks likely. Satellite imagery shows an
area of increased dust concentration ahead of the feature
anticipated for this weekend. Showers are still likely, and more
vigorous showers cannot be ruled out, as moisture reaches further
aloft. Forecast confidence is moderate to high.

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

During the weekend, model guidance continues to suggest that a
TUTT low will move over or close to Hispaniola, while a stronger
tropical wave streams across the region. The trade wind cap is
expected to decrease during this period, and moisture pooling
in combination with divergence aloft should result in a wetter
pattern than in previous days across the forecast areas.
Therefore, the environment will favor shower and thunderstorm
activity across the islands.

For the first part of next week, the area is expected to remain
under the subsidence/convergent side of a retrogressing TUTT low
from the central Atlantic. In addition, another strong SAL event
is forecast to reach the area. This will cause moisture content to
decrease and mostly light rainfall amounts are expected in night
time/early morning showers across the USVI and eastern sections of
PR, followed by shallow afternoon convection over the southwest
PR each day.


&&

.AVIATION...Generally VFR conditions are expected across all
terminals next 24 hours. VCSH for TJPS after 21/16Z due to
afternoon convection, which will mostly be to north and west of
aerodrome. Winds generally out of the east at 12 to 18 knots after
21/14Z, with sea breeze variations, diminishing after sunset.
Note: observations overnight suggest MVFR conditions at TISX,
but suspect artificially low ceiling due to hazy conditions.


&&

.MARINE...A building surface high pressure over the central Atlantic
will promote a moderate to locally fresh trade wind flow across
the regional waters. Seas should range in general between 3-5 feet.
A moderate risk of rip currents will prevail through the weekend
for most of the beaches of PR and the USVI.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 78 88 78 / 30 20 30 30
STT 90 79 89 78 / 30 30 20 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
430 AM AST Thu Jul 22 2021

.SYNOPSIS...The chance for shower and thunder activity is
expected to increase with two tropical waves passage Friday
and Sunday. Meanwhile, a seasonal weather pattern will continue
to prevail with hazy skies and rainfall activity focused across
western areas of Puerto Rico each afternoon.

&&

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

A TUTT-Low lingering north/west of the islands will continue to
approach throughout the day. However, GOES-16 imagery identified
below-normal Total Precipitable Water (TPW) values and remnants of
suspended African dust moving from the east into the region. That
air mass will move across the U.S. Virgin Islands and Puerto Rico
today, limiting the available moisture and thus rainfall activity.
This weather pattern will result in another day with warm to hot
temperatures and hazy skies. Rain activity, if any, will be confined
across PR`s interior and western sections as well as downwind from
the USVI during the afternoon.

The leading edge of a weak tropical wave will reach the local
archipelago of PR/USVI by late tonight into Friday. This tropical
wave encounters a hostile environment as dry air with African Dust
particles is surrounding it. However, the TUTT-Low will increase
instability, increasing the vertical development, enhancing the
formation of isolated thunderstorms. Due to the persisting dry air
surrounding the wave, we are not expecting widespread. The more
vigorous activity should cluster across western PR during the
afternoon.

The potential for rain formation will diminish late Friday night
into Saturday, but a wind surge associated with Sunday`s tropical
wave will increase moisture. The available tropical moisture will
then interact with the TUTT-Low, located in a more favorable
position over the Hispanola. Therefore, increased shower/thunderstorm
activity is likely early this weekend.

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

Although 250mb heights are expected to rise Sunday night into
Monday, a falling trend is expected once again by midweek as an
upper level trough approaches from the east. Nevertheless, as
the moisture erodes Sunday night into Monday, precipitable water
values are expected to remain below 1.70 inches without any
significant moisture advection foreseen. As a matter of fact,
aerosol guidance suggests more African dust particles reaching
the forecast area early the next week.

As a result, the day with the highest chance for periods of showers
and thunderstorms is Sunday as a tropical wave and associated
moisture interacts with a trough aloft. Urban and small stream
flooding is likely with the heaviest showers. A drying trend is
then expect Tuesday onwards with shower activity focused across
western areas of Puerto Rico. Elsewhere, fair weather. Hazy.
Maximum temperatures continue to range in the upper 80s to low
90s.

&&

.AVIATION...Mainly VFR conditions expected to prevail through the
forecast period. Hazy skies will remain today, but don`t
anticipate restrictions to VIS. Expect calm to light and VRB winds
til 22/13z, then winds return from the east at 10 to 20 with sea
breeze and gusty winds around 25 knots.

&&

.MARINE...A building surface high pressure over the central
Atlantic will promote a moderate to fresh trade wind flow.
Therefore, seas should range in general between 3-5 feet across
all offshore waters and between 2-5 feet over the coastal waters.
A moderate risk of rip currents will prevail through the weekend
for most of the beaches of PR and the USVI.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 78 87 78 / 10 50 40 60
STT 90 78 89 78 / 10 50 30 50

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
425 AM AST Fri Jul 23 2021

.SYNOPSIS...An increase in moisture is expected today, as a weak
tropical wave moves across the region. Another tropical wave, with
more moisture content, is expected to further increase the shower
and thunderstorm activity during the upcoming weekend. Drier and
hazy conditions early the upcoming workweek.

&&

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

Weather conditions will become more favorable for the development of
showers and thunderstorms from today to Sunday. This weather pattern
is associated with a TUTT-low northeast of the islands and two
tropical waves that will swing by. The first tropical wave is weak;
however, as instability increases, the diurnal pattern will develop
near the San Juan metro area and PR`s interior and western sections
due to the nearby TUTT-low. Although moisture will increase and rain
activity will affect the region, we are not anticipating significant
rainfall amounts across the U.S. Virgin Islands with today`s wave.

Rain activity will diminish somehow this evening into early Saturday
morning due to the subsidence ahead of this weekend`s robust
tropical wave. However, moisture will ramp up shortly after midnight
as the leading edge, and a wind surge of the tropical wave reach the
islands on Saturday and its axis by Sunday. As this happens, the
TUTT-Low mentioned above will be relocated near the Hispanola,
providing good ventilation aloft enhancing organized convection
Saturday and Sunday. The Virgin Islands can expect a better chance
to observe significant rainfall accumulations with this wave. GFS-
Galvez and Davidson Index suggest favorable atmospheric conditions
for the development of thunderstorms. If guidance is correct,
widespread showers with isolated to scattered thunderstorms will
increase the risk for urban and small-stream flooding, with
localized flash flooding possible this weekend. If persistent
downpours materialize in the forecast area, then our confidence is
moderate to expect localized Flash Flooding; otherwise, our
confidence is moderate-high to expect widespread showers and
thunderstorms during the weekend.

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

A ridge pattern aloft will erode early the upcoming workweek as a
retrogressing TUTT reaches the forecast area. This feature with
its associated upper level low is expected to cross the local
islands Wed-Thu enhancing moisture advection and instability. At
lower levels, surface high pressure across the north central
Atlantic will continue to yield moderate easterly winds much of
the forecast cycle. As the aforementioned TUTT low moves away, a
mid level ridge will build across the area, bringing drier and
stable weather conditions.

This evolving pattern will result in fair weather conditions
with afternoon convection focused across western areas of Puerto
Rico Monday, Tuesday and Friday, being Tuesday the driest day.
Hazy early in the week due to African dust particles as well. The
intensity and areal coverage of the afternoon showers and
thunderstorms likely to increase Wednesday and Thursday due to the
proximity of the upper trough and precipitable water values near
2.0 inches. The highest chance continue to be across western areas
of Puerto Rico each afternoon. With the heaviest showers, minor
urban flooding is likely.

&&

.AVIATION...A tropical wave will bring showers and possible
thunderstorms later this afternoon. However, mainly VFR conditions
are expected to prevail through the forecast period. SHRA/TSRA will
form across eastern and western PR, especially between 23/15-23z,
impacting JSJ/JBQ. Passing showers moving across terminals can not
be ruled out. Winds will continue calm-light/VRB increasing from the
east at 10-20 kt with higher gusts and sea breeze variations after
23/12Z.

&&

.MARINE...A moderate to fresh trade wind flow will continue during
the next several days, resulting in choppy marine conditions. Seas
should range in general between 3-5 feet across all offshore waters
and between 2-5 feet over the coastal waters. A moderate risk of
rip currents will prevail through the weekend for most of the
beaches of PR and the USVI.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 78 87 79 / 50 60 60 50
STT 89 78 88 78 / 30 60 60 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
417 AM AST Sat Jul 24 2021

.SYNOPSIS...Unstable weather conditions through the weekend due
to a tropical wave passage and the proximity of a trough aloft.
As a result, there is an increasing risk for urban and small
stream flooding as well as localized flash flooding. Weather
conditions are expected to improve early the next workweek.

&&

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

Weather conditions are evolving as expected, and an unsettled
pattern will hold across the islands through at least Sunday. It is
due to the interaction of a meandering TUTT-Low and a tropical wave,
which will enhance shower and thunderstorm formation. GOES-East-
derived products are indicating Total Precipitable Water (TPW)
around 2 inches approaching the U.S. Virgin Islands. Therefore,
abundant tropical moisture will pool over the islands, promoting
widespread showers and scattered thunderstorms across the region
of USVI/PR today and tomorrow. The best round of organized
convection is expected this afternoon as TPW peaks and the TUTT-
low approaches the Hispanola. As a result, widespread showers and
scattered thunderstorms will develop across the region, especially
this afternoon into the evening and early Sunday morning. The
conditions mentioned above could trigger urban and small-stream
flooding, with localized flash flooding and mudslides. The second
round of showers and thunderstorms will develop by Sunday as the
wave`s axis moves closer, and the U.S. Virgin Islands would
possibly observe heavy showers and thunderstorms.

GFS-Galvez and Davidson Index suggest favorable atmospheric
conditions for the development of thunderstorms. Therefore scattered
thunderstorms were introduced for this afternoon and Sunday.

Moisture and rain activity will diminish somewhat by Monday as the
lingering moisture of the wave is replaced by dry air with African
dust suspended particulate. However, the typical weather pattern
will persist, with passing showers across the windward sections
during the morning and afternoon convection across the western
portions. Hazy skies will return by late Monday afternoon into the
evening.

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

Long term forecast is still on track. A ridge pattern aloft will
erode as a retrogressing TUTT moves closer to the forecast area.
This feature with its associated upper level low is expected to
cross the local islands Wed-Thu enhancing moisture advection and
instability. As the aforementioned TUTT low moves away, a mid level
ridge will build once again across the area, bringing drier and
stable weather conditions Friday through the end of the forecast
cycle. At lower levels, surface high pressure across the north
central Atlantic will continue to yield moderate to fresh easterly
winds.

Therefore, expect fair weather conditions with afternoon convection
focused across western areas of Puerto Rico much of the next
week, except for Wednesday and Thursday. The intensity and areal
coverage of the afternoon showers and thunderstorms likely to
increase those days due to the proximity of the upper trough and
precipitable water values near 2.0 inches. Some haziness on
Tuesday due to African dust particles as well. Maximum
temperatures continue to range in the upper 80s to low 90s.

&&

.AVIATION...A tropical wave will bring showers and thunderstorms
across the islands through the forecast period. TEMPOs are in
place for JSJ/IST/ISX/NCM/KPK and could be needed later this
afternoon. Therefore, expect MVFR or IFR conditions due to
TSRA/+SHRA. SHRA/TSRA will spread across most of the islands after
24/15z. Winds will continue calm-light/VRB but gusty near
TSRA/SHRA, increasing from the east at 10-20 kt with higher gusts
and sea breeze variations after 24/12Z.

&&

.MARINE...Moderate to fresh easterly winds will continue to
prevail during the next several days with seas expected to mostly
range between 3 and 6 feet. However, across the northeastern
portion of the offshore Atlantic waters, seas of up to 7 feet are
possible through early Sunday morning. For beachgoers, a moderate
risk of rip currents is expected to continue across most of the
beaches of north and southeast Puerto Rico as well as Culebra,
Vieques, and the US Virgin Islands through the weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 79 88 79 / 80 50 70 50
STT 88 78 88 80 / 60 60 70 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
442 AM AST Sun Jul 25 2021

.SYNOPSIS...Unstable weather conditions will continue to prevail
due to plenty of moisture and the proximity of a TUTT-low. This
will enhance the potential for urban and small stream flooding as
well as localized flash flooding. Weather conditions are expected
to improve early the next workweek.

&&

.SHORT TERM...TODAY THROUGH TUESDAY...

The interaction between a TUTT-low and a strong tropical wave is
producing showers and thunderstorms across the islands. The
unsettled weather pattern will persist across the islands through at
least Monday afternoon when the lingering moisture of this wave
should slowly erode, and a ridge pattern builds aloft.

GOES-East-derived and GFS guidance indicated above-normal Total
Precipitable Water (TPW) across the U.S. Virgin Islands and Puerto
Rico. As the TUTT-Low continues to provide good ventilation aloft,
isolated to scattered thunderstorms will form once again across the
islands throughout the day. GFS-Galvez and Davidson Index suggest
favorable atmospheric conditions for the development of organized
convection near the eastern third of Puerto Rico, the U.S. Virgin
Islands, and surrounding waters later this afternoon into the
evening. The islands had a moderate to high flooding threat. Expect
urban and small-stream flooding, with localized flash flooding
and mudslides today.

Showery weather will persist on Monday as the lingering moisture of
the wave and the TUTT-low remain near the islands but in a more
seasonal pattern. A mid to upper-level ridge building aloft and a
dry air mass with Saharan Dust Particles will limit the potential
for showers and thunderstorm development after Monday afternoon into
Tuesday. The typical weather pattern will return by Tuesday.


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

A retrogressing TUTT will enhance moisture advection and
instability early in the forecast cycle. As this feature moves
away, a mid level ridge will build once again across the forecast
area with some weakening expected by the end of the upcoming
weekend. At lower levels, surface high pressure across the north
central Atlantic will continue to yield moderate easterly winds.
Latest guidance suggests best moisture advection Wednesday night
into Friday with precipitable water values near 2 inches. This
evolving pattern will result in showers across the US Virgin
Islands and eastern Puerto Rico at times with afternoon showers
and thunderstorms across western Puerto Rico Wednesday thru early
Friday. Friday afternoon into the upcoming weekend, fair weather
conditions are expected to prevail across much of the forecast
area with locally induced showers and isolated thunderstorms
focused over western areas of Puerto Rico each afternoon. Maximum
temperatures continue to range in the upper 80s to low 90s.

&&

.AVIATION...A tropical wave will bring SHRA/TSRA across the islands
through the fcst prd. VCTS will persist across most of the
terminals of PR/USVI today. Later today, we cannot rule out
periods of MVFR or IFR conditions due to TSRA/+SHRA. SHRA/TSRA
will spread across most of the islands after 25/14z. Winds will
continue calm-light/VRB but gusty near TSRA/SHRA, increasing from
the SE at 10-20 kt with higher gusts and sea breeze variations
after 25/12Z.

&&

.MARINE...Moderate easterly winds will continue to prevail during
the next several days with seas expected to mostly range between
3 and 5 feet. However, across the northeastern portion of the
offshore Atlantic waters, seas of up to 7 feet are possible
through early Monday morning. For beachgoers, a moderate risk of
rip currents is expected to continue across most of the beaches of
north and southeast Puerto Rico as well as Culebra, Vieques, and
the US Virgin Islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 79 88 78 / 70 60 40 20
STT 87 80 90 79 / 70 70 40 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
420 AM AST Mon Jul 26 2021

.SYNOPSIS...Lingering moisture from a tropical wave will continue
to result in unsettled weather conditions through this afternoon.
Then, a drier air mass with Saharan dust will filter in later
today into Tuesday. Another Tropical Upper Tropospheric Trough
(TUTT) will move towards the area by the middle of the work week,
with more unsettled weather conditions expected.

&&

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

Weather conditions will slowly improve across the islands this
morning. However, the lingering moisture from this weekend`s
tropical wave will combine with local effects and the diurnal
effects to produce another round of showers across the local islands
this morning into the afternoon hours. In addition, as the TUTT
moves westward, a mid to upper-level ridge will build over the
islands later today. A drier air mass with Saharan Dust particles
will filter from the east by this afternoon, creating hazy skies
and limiting shower activity, beginning with the U.S. Virgin
Islands and then the rest of PR. Nevertheless, periods of showers
and even thunderstorms may develop across PR`s interior and
western portions and downwind from El Yunque into the San Juan
metro area.

Another TUTT will move aloft from the northeast into the
Northeastern Caribbean Tuesday into Wednesday, leaving the islands
in the less favorable position for upper-level dynamics. This
upper- level feature will be inducing surface troughs creating the
typical weather pattern with scattered showers across the
windward sections overnight and early in the morning followed by
afternoon convection across the western portions. This activity
will be more frequent on Wednesday as this TUTT continues moving
westward across the region.

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

Conditions are expected to remain somewhat unsettled on Thursday
as the TUTT will be situated over the Dominican Republic, with the
area remaining on the favorable side for divergence aloft. This in
combination with near-normal moisture levels will help to promote
another round of enhanced afternoon convection, mainly across the
northwestern quadrant of Puerto Rico with the low-level flow
becoming southeasterly. As the TUTT continues to move farther
westward, a mid and upper-level ridge will then build into the
area on Friday and into next weekend, promoting dry air intrusion.
A tropical wave is expected to move across the Caribbean waters
late Friday into early Saturday, however, at this time model
guidance suggests that the most active part of the wave remains
south of the area. Therefore, mainly fair weather conditions are
forecast at this time for Friday and into the upcoming weekend
with limited afternoon convection possible across western Puerto
Rico. Another TUTT is expected to retrograde towards the area
early next week, with an increase in convection possible once
again.


&&

.AVIATION...VFR conditions will persist early this morning, with a few
SHRA/-SHRA moving near/across JSJ/IST/NCM/KPK but without
significant impacts. SHRA/TSRA will then develop across PR`s
interior and western portions, where it could impact JSJ/JBQ
between 26/15-22z. Hazy skies are forecast after 26/18z, but with
visibility greater than 6SM. Winds will continue calm-light/VRB,
increasing from the ESE at 10-20 kt with higher gusts and sea
breeze variations after 26/12Z.

&&

.MARINE...Moderate to locally fresh trade winds will result in
seas ranging between 3 and 6 feet for today, with the highest
seas expected across the Atlantic waters. Therefore, small craft
operators should continue to exercise caution. More tranquil seas
are forecast through the rest of the work week. For beachgoers,
there is a moderate risk of rip currents for the northern and
southeastern beaches of Puerto Rico as well as for most of the
beaches of Vieques, Culebra, and St. Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 77 86 76 / 30 20 20 40
STT 88 78 89 77 / 30 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
359 AM AST Tue Jul 27 2021

.SYNOPSIS...Mainly fair weather conditions are expected for today,
with limited afternoon convection over southwestern Puerto Rico.
An increase in shower and thunderstorm activity is expected
Wednesday and Thursday as a Tropical Upper Tropospheric Trough
(TUTT) moves over the area. This will be followed by a drier and
more stable weather pattern on Friday through the upcoming weekend
as a mid and upper-level ridge builds overhead.

&&

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

The available moisture will decrease today, causing the precipitable
water values to be close to 2 standard deviations below normal.
There is also an ENE wind flow today, which will cause sea breeze
convergence across the southwestern quadrant of Puerto Rico this
afternoon. There is overall not a significant amount of instability
to expect widespread or very heavy rain across the local islands.
That said, isolated to scattered brief showers are expected across
the local islands today, mainly in the form of streamers. Also,
scattered to numerous showers are expected this afternoon across the
southwestern sections of PR, with a slight chance of thunderstorms.
The overall impact is expected to be that of ponding of water in
areas of poor drainage, but some urban flooding will not be ruled
out for small areas of southwest PR.

The available moisture will increase on Wednesday, closer to normal
levels for the time of year, while a TUTT passes over the local
islands. This will cause an increase in shower activity across the
local area in both coverage and intensity. Scattered showers are
forecast for most of the day on Wednesday, with numerous showers and
isolated thunderstorms across the western to northwestern PR on
Wednesday afternoon. The general wind flow on Wednesday will be more
easterly, but that will change for Thursday. The general wind flow
will become southeasterly on Thursday. Also, the TUTT will be to our
west and in a better position to support thunderstorm development,
especially across the NW sections of PR where there will be sea
breeze convergence in the afternoon. The available moisture will be
near to below normal, and there is some indication that small
concentrations of Saharan dust could be moving in, so shower
activity may be modest. Therefore, isolated to scattered showers are
forecast across most of the local area, but numerous showers and
isolated thunderstorms are expected across the NW quadrant of PR on
Thursday afternoon.

The overall temperatures will be near normal, with highs in the
upper 80s to low 90s across the lower elevations, and in the upper
70s to mid 80s across the higher elevations. Low temps will be in
the mid 70s to near 80 across the lower elevations, and in the upper
60s to low 70s across the higher elevations.

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

As the TUTT moves further away towards the west, a mid and upper-
level ridge will build over the area on Friday and prevail
through the upcoming weekend. This will result in drier and
more stable conditions aloft. A tropical wave is expected to move
across the eastern Caribbean on Friday, however, model guidance
continues to indicate that the most active part of the wave will
remain south of the area. Although some moisture associated with
the wave may reach the area and produce isolated to locally
scattered shower activity, no significant rainfall is expected due
to unfavorable dynamics aloft. Moisture then is expected to be
mostly below normal during the weekend. Therefore, mainly fair
weather conditions can be expected with rainfall activity limited
to the typical afternoon convection across western Puerto Rico.
The upper-air pattern then changes during the early to middle
portion of next week as another deep-layered TUTT retrogrades
towards the area. This feature in combination with increasing
moisture will result in more favorable conditions for better
convective activity across the local area, especially during the
afternoon time period. Therefore, if model guidance is correct,
a wetter weather pattern will be possible during the early to
middle portion of next week.

&&

.AVIATION...VFR conds are expected across the local terminals through the
forecast period. Brief VCSH is possible in ISOL SHRA this morning,
but is not expected to pose a significant hazard to the local
terminals. Winds will be mainly from the ENE at 10KT or less through
27/13Z, but increasing to 15KT and gusty thereafter. Sea breeze
variations expected, causing SE winds at TJPS after 27/13Z.

&&

.MARINE...More tranquil marine conditions with seas of up to 5
feet will prevail across the regional waters for today. Seas are
expected to remain generally below 6 feet through the rest of the
work week and into the upcoming weekend. For beachgoers, there is
a moderate risk of rip currents for the northern and southeastern
beaches of Puerto Rico as well as the eastern beaches of Culebra,
Vieques and Saint Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 77 86 76 / 20 40 40 40
STT 89 77 87 78 / 20 30 30 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
441 AM AST Wed Jul 28 2021

.SYNOPSIS...An increase in shower activity is expected today into
tomorrow as a Tropical Upper Tropospheric Trough (TUTT) moves
over the area. For this weekend, a drier pattern and air mass is
expected due to increasing Saharan dust and a mid to upper level
ridge over the forecast area. Tranquil marine condtions will
prevail for the next several days over the local waters.

&&

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

The short term forecast period is expected to have some shower and
thunderstorm activity, with the rainiest day expected to be today,
followed by Thursday night into Friday morning.

Scattered to numerous showers are expected today, with
thunderstorms late in the morning and in the afternoon hours over
Puerto Rico. The easterly wind and near normal moisture, combined
with a retrograding TUTT will be the main reasons for the
expected weather today. The TUTT, as it retrogrades and passes
through the local area today, will cause divergence and
ventilation aloft, giving support for thunderstorm development.
Therefore, some areas could observe urban and small stream
flooding, especially portions of western and northwestern Puerto
Rico, as well as some areas of eastern PR. Ponding of water in
poor drainage areas can be expected elsewhere in PR. The USVI is
expected to observe scattered but brief showers, which through the
day could see some rainfall accumulations but flooding is not
expected, though ponding in areas of poor drainage will not be
ruled out.

Thursday is forecast to be a fairly typical summer day with
showers and thunderstorms developing in the afternoon across
northwestern PR under a southeasterly wind flow. The USVI will
observe isolated to scattered showers. Even though the TUTT will
be to the west of the local area, the TUTT continues
retrograding, which generally does not provide as much divergence
aloft compared to a non-retrograding TUTT in the same position.
Also, the mid levels have zonal flow and there is the possibility
of some Saharan Dust. Therefore, the model guidance is suggesting
typical and modest amounts of rain across the local islands, with
the highest amounts of rain across NW-PR.

However, the available moisture will start to increase
significantly on Thursday night into early Friday, as moisture is
pulled northward from the ITCZ and the TUTT would have probably
stalled north of Hispaniola by late Thursday. This could cause
showers and thunderstorms across the local waters, and portions of
the local islands, including the USVI. Drier air, with a higher
concentration of Saharan dust is expected during the day on
Friday, promoting much drier conditions. A patch of moisture could
pass through late Friday, but a mid and upper level high pressure
is expected to be present over the local area, promoting
subsidence and stability, limiting significant shower activity.


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

A dry pattern is expected for the fist part of the long term
period. Model guidance continues to suggest a mid-upper level
ridge located just north of the forecast area, promoting stable
conditions. Meanwhile, at the surface, a drier air mass with
Saharan dust particles is expected to filter into the region this
weekend. Given the expected conditions, a dry weather pattern and
hazy skies can be expected this weekend with minimal precipitation
forecast for western Puerto Rico. On Tuesday, as the surface
high pressure moves into the central Atlantic, southeasterly winds
are expected over the local area. This wind flow will drag some
patches of moisture over the local region. As a result, an
increase in the potential for shower development is expected,
mainly over the northwestern quadrant of puerto Rico and the San
Juan metro area. Daytime temperatures can slightly increase due to
the southeasterly wind flow.

By early Wednesday, at the upper levels, both GFS and ECMWF model
guidance are suggesting a Tropical Upper Tropospheric Trough
(TUTT) moving westward into the local area. The TUTT will result
in unstable conditions aloft starting late Wednesday. At the
surface, several patches of moisture with precipitable water
values above the climatological normal are expected to filter
into the region embedded in the wind flow. The combination of the
aforementioned conditions will result in widespread shower
activity across the forecast area Wednesday into Thursday. As a
result, ponding of water in roadways and poor drainage areas is
likely and urban and small stream flooding is possible with the
heaviest activity each day.

&&

.AVIATION...VCSH/SHRA expected today across most of the local
terminals as SCT/NMRS SHRA move through the local area. TSRA is
expected across portions of PR, causing VCTS at TJSJ and then TJBQ
after 28/16Z or so. Winds from the east at around 10KT expected
until 28/13Z, increasing to around 15-20KT with gusts and sea
breeze variations after 13Z.


&&

.MARINE...Across the regional waters, tranquil marine conditions
with seas of up to 5 feet will prevail across the regional waters
for the next several days. For beachgoers, there is a moderate
risk of rip currents for the northern beaches of Puerto Rico as
well as the eastern beaches of Culebra, Vieques and Saint Croix


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 76 89 78 / 40 40 30 20
STT 87 78 88 79 / 30 40 40 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
446 AM AST Thu Jul 29 2021

.SYNOPSIS...A Tropical Upper Tropospheric Trough (TUTT) currently
moving over the local area will continue to result in shower
activity over the region. A dry pattern is expected for this
weekend, due to an increase in drier air and Saharan dust
particles, and a mid to upper level ridge moves over the forecast
area.

&&

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

Near normal moisture is expected in the morning, but a patch of
drier air with some minor concentrations of Saharan Dust will move
in during the late morning into the afternoon hours. However,
starting late this afternoon and tonight, a tropical wave will move
in and will bring deeper moisture. The overall wind flow will shift
to a more SE direction as the day progresses. There is also a TUTT
passing through the local area, which could help promote
thunderstorm development this afternoon. So given the current and
expected pattern, scattered showers are expected in the morning
across the local islands, isolated thunderstorms could start
developing late in the morning and into the afternoon hours. The
northwestern municipalities of PR have the highest chance of
thunderstorms this afternoon. Also, showers and thunderstorms
expected tonight into Friday morning, as the TUTT interacts with the
tropical wave that will cause the increase in moisture. This
increase in activity will be generally across the Caribbean waters,
south and eastern PR and around the USVI. The SE winds could cause
warmer than normal temperatures for the northern sections of PR
today.

For Friday and Saturday, the shower activity is expected to be more
modest, with locally induced afternoon showers across W/NW PR on
Friday, with isolated to scattered showers elsewhere through the
day. Even less shower activity is expected on Saturday across the
local area. Much drier air is expected to move in with a higher
concentration of Saharan dust. For that reason, very limited shower
activity is expected. The model guidance also is suggesting daytime
temps in the 90s for Saturday.

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

A drier air mass with saharan Dust particles will continue to
move over the forecast area on Sunday. As a result, fair weather
conditions with hazy skies are expected to prevail for the first
day of the long term forecast (Sunday). Tuesday now looks like it
has better potential for shower development. First, the surface
high pressure across the central Atlantic is expected to induce a
southeasterly component in the winds over the forecast area. As a
result, this wind flow will drag some patches of moisture with
precipitable water above normal. Meanwhile, at the upper levels,
the ECMWF and GFS model guidance is suggesting a Tropical Upper
Tropospheric Trough (TUTT) moving westward into the local area,
which will help increase thunderstorm potential. At this time,
the models kind of agree in the timing of the most unstable
conditions over the region. That said, expect morning showers
over the eastern sections of Puerto Rico and the U.S. Virgin
Islands. Then, in the afternoon hours, Galvez- Davison index
suggest the possibility of scattered thunderstorms across
northwestern quadrant of Puerto Rico. Confidence in the forecast
is moderate, but still a few days to follow the dynamics in the
upper levels and the moisture content.

For Wednesday onward, a rainy pattern is expected. On Wednesday,
several patches of moisture are expected to filter into the
region. The combination of the available moisture with the local
effects and the upper level dynamics, will result in afternoon
convection over the western sections of Puerto Rico, while
isolated to scattered showers are expected elsewhere. On Thursday
morning, a slot of dry air will move over the area, limiting the
shower activity, but after that, in afternoon hours, a tropical
wave is expected to increase the potential for shower activity
once again through Friday. As a result, shower development is
expected, mainly over the northwestern quadrant of Puerto Rico
and the San Juan metro area each day.

&&

.AVIATION...
VCSH expected across the local terminals today as SCT SHRA affect
the local area. However, TSRA is expected across NW-PR this
afternoon, which could affect the actual TJBQ terminal, but VCTS on
TAF due to some uncertainty on exact timing. Winds will be from the
east at around 10KT or less through 29/13Z, but will increase to
around 15KT with gusts up to 25KT and sea breeze variations
thereafter.

&&

.MARINE...
Across the regional waters, tranquil marine conditions
with seas of up to 5 feet will prevail across the regional waters
for the next several days. For beachgoers, there is a moderate
risk of rip currents for the northern and southeastern beaches of
Puerto Rico as well most of the beaches of Culebra, Vieques and
Saint Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 91 77 89 79 / 50 50 40 30
STT 88 79 88 80 / 30 50 40 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
426 AM AST Fri Jul 30 2021

.SYNOPSIS...

For the weekend, an improvement in weather conditions is expected,
as a drier air mass with Saharan dust particles filters into the
region. Weather conditions will turn variable as the trade winds
push patches of moisture over the forecast area. Tranquil marine
conditions are expected over the local waters over the next
several days.

&&

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

Below normal moisture is moving in and is expected over the local
islands for much of today. There is a brief patch of moisture that
will pass through this afternoon, but for the most part, drier than
normal available moisture is expected. There is also some Saharan
dust, which could cause hazy skies. Currently there are isolated
and brief showers across the local waters, USVI and eastern PR, but
only trace amounts of rain are being observed. This activity is
expected to remain the same or diminish after sunrise. The mid and
upper levels are starting to show high pressure over the local area,
causing stable conditions. That said, locally induced showers are
possible across western PR this afternoon, thunderstorms are not
expected, but will not rule out a brief and isolated thunderstorm.
Based on the current forecast, some ponding of water in areas of
poor drainage is possible across some areas of western PR. The
daytime temperatures will be in the upper 80s to low 90s across the
lower elevations, heat indices may reach 100-105 across portions of
north central PR.

For Saturday and Sunday, the drying trend is expected to continue,
especially for Saturday as much drier air is expected to move in
with a higher concentration of Saharan dust. For that reason, very
limited shower activity is expected. The model guidance also is
suggesting daytime temps in the 90s. Then un Sunday, the general
pattern remains the same but a small patch of moisture may move in
briefly. This quick patch of moisture may be enough to cause some
shower development across western PR when combined with the diurnal
heating and the local effects.

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

A wetter pattern is expected for most of the long term period. At
the surface, a wind surge with precipitable water values near
normal will reach the local islands, increasing the potential for
shower development. In the upper levels, a retrogressing TUTT-low
will continue to moves westward. For Monday, model guidance
suggests the subsident side of the TUTT will move over the local
area. Regardless of the stability of the conditions aloft, the
available moisture, along with the local effects can erode the
trade wind cap and result in afternoon convection over western
Puerto Rico. By Tuesday, at the surface, moisture embedded in the
east- southeasterly wind flow is expected to move in. Meanwhile,
better upper level dynamics are expected, both the GFS and ECMWF
model guidance are suggesting a TUTT to be located just at north
of the forecast area. If model guidance is correct, the TUTT will
result in unstable conditions on Tuesday into early Wednesday.
Therefore, shower activity is expected across the forecast area,
possibly resulting in urban and small stream flooding each
afternoon over the first half of the workweek.

The moisture will slowly decrease over the region on Thursday,
as a narrow slot of drier air moves in. This will limit shower
activity through the late evening hours on Thursday. By Friday, a
tropical wave is expected to move over the lesser Antilles into
the local area. The bulk of the moisture is expected to remain
to our south, however, above normal moisture is expected over the
area. So given the expected pattern, scattered showers are
expected across the local islands. As the building surface high
pressure moves into the central Atlantic on Saturday, a mixture
of patches of moisture and drier air will result in isolated to
scattered shower activity across the local waters, USVI, and
eastern PR in the morning and overnight hours, while afternoon
convection would be expected somewhere across western PR.

&&

.AVIATION...VCSH expected this morning across the local terminals
today as ISOL -SHRA affect the local area. SHRA is possible
across W-PR this afternoon, which could affect the vicinity of the
TJBQ terminal. HZ is present but VIS expected to remain P6SM.
Winds will be from the east at around 10KT or less through 30/13Z,
but will increase to around 15KT with gusts up to 25KT and sea
breeze variations thereafter.


&&

.MARINE...Tranquil marine conditions will prevail over the local
waters with seas up to 5 feet and winds up to 15 knots. A few
passing showers are posibles over the local waters. There is a
moderate risk of rip current over north, southwest and
southwestern local beaches of puerto Rico, as well most of the
local beaches at Culebra, Vieques and St. Croix.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 89 79 / 30 20 10 30
STT 89 80 89 80 / 20 20 20 20

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
434 AM AST Sat Jul 31 2021

.SYNOPSIS...A weak tropical wave now located over the local region will
continue to move west over the local area through late morning. An
area of Saharan dust along with drier air is expected to move across
the local region behind the tropical wave therefore limiting shower
development across the region this afternoon through Sunday.

&&

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

At the upper levels, a Tropical Upper Tropospheric Trough (TUTT)
continues to hold north of Hispaniola. Drier air mass with Saharan
Dust particles are expected at the mid levels. At low levels, PW
value of 2.28 inches. Forecast sounding suggest near normal PW
values and a strong wind cap inversion at 850 mb. This scenario will
result in a seasonal weather pattern over the islands. However, a
weak tropical wave will continue move across the islands. Thus
shower activity is expected to increase somewhat over the forecast
area. Drier air will quickly filter in afterwards. Hence, moistly
fair weather conditions with hazy skies are expected trough much of
the rest of the short term period. Limited shower activity is
expected during the afternoon hours over parts of interior and
western Puerto Rico. However, showers embedded in the trade winds
will reach the islands and surrounding waters from time to time
during the overnights and early morning hours.

For Monday, model guidance suggests the subsident side of the TUTT
moving over the local area. Regardless of the stability of the
conditions aloft, the available moisture, along with the local
effects can erode the trade wind cap and result in afternoon
convection over western Puerto Rico.

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

Although moisture will remain nearly constant between Tuesday an
Wednesday...models are suggesting a more unstable environment
during this period as the TUTT will be located just to the north
of our region. Therefore, shower and thunderstorm activity is
expected across the forecast area, increasing the potential urban
and small stream flooding to occur. The low level moisture will
be the limiting factor for shower development between late
Wednesday and Thursday night.

The tropical wave now locate just to the west of Africa will
continue to move westward for the next 7 days. As this wave moves
toward our local region will begin to elongated northward and
become positive tilted. A wind surge associated to this wave is
forecast to reach our local region on Friday and the tropical wave
sometime during the weekend.

&&

.AVIATION...Mainly VFR conds at all TAF sites. HZ continues to be
present, but VIS expected to remain P6SM. Winds will be from the
east ranging at 10 knots or less overnight, becoming from 15 to 20
kts with higher gusts and seas breeze variations during the day.


&&

.MARINE...Models and buoy observations show seas around 2-4 feet
across the nearshore waters, and up to 5 feet offshore, and winds
out of the east at 10 to 20 knots. Small craft operators should
exercise caution due to winds. These conditions should linger for
the next few days.

Across the local beaches, the rip current risk is moderate for
the northern, eastern, some in the south, as well as Vieques and
Culebra, most of St. Croix and the southern coast of St. John and
St. Thomas.



&&

.FIRE WEATHER...The entrance of a drier air mass under a generally
easterly wind flow will not support wetting rains affecting the
southern coastal plains of Puerto Rico. Thus, further drying can be
anticipated. This same mass will cause relative humidity values to
fall into the upper 40s to lower 50s, while the highest sustained
winds are forecast to peak around 15-20 mph with higher gusts and
sea breeze variations between the late morning and early afternoon
hours. Taking all these factors into consideration, with the most
recent KBDI and 10-hour fuel moisture values remaining within fire
danger thresholds, a Fire Danger Statement has been issued for
elevated fire weather conditions expected across the southern
coastal plains of Puerto Rico today.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 79 90 77 / 20 10 20 40
STT 89 79 89 78 / 20 10 20 30

&&

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
506 AM AST Mon Aug 2 2021

.SYNOPSIS...Surface high pressure across the north central
Atlantic will continue to yield a gentle to moderate easterly wind
flow during the next several days. A TUTT low will drift westward
from the Atlantic Ocean into the Northeast Caribbean through
Tuesday. Increasing moisture will help in the development of
showers and isolated thunderstorms across the local forecast area.

&&

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

A more typical seasonal weather pattern is expected to prevail for
today. The drier air at the mid levels is expected to erode due to
deeper moisture over the islands. At surface, a high pressure near
the Azores will promote east-northeast trades. Thus, showers will
continue to advect during the early morning hours. Then, a shift in
winds, more to the east-southeast and the available moisture will
combine with diurnal heating and local effects to generate scattered
to numerous showers over the northwestern quadrant of Puerto Rico. A
TUTT-low will move westward from the Atlantic Ocean into the
Northeast Caribbean today through Wednesday. Model guidance
suggest and increase in moisture (PWAT values around 1.7
inches)for Tuesday and Wednesday. There is good potential for
isolated thunderstorm activity during the afternoons mainly due to
daytime heating, local forcing and the proximity of the TUTT.
Rainfall accumulations could be enough to cause minor urban
flooding with the heaviest rains. This will increase the potential
for urban and small stream flooding.


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

On Thursday the GFS model is suggesting a drop on precipitable
water across the region but a wind surge will help increase the
moisture across the local area between late Thursday night and
Friday. This weather feature will help increase the showers
coverage across the region through the weekend. A tropical wave is
forecast to move across the Caribbean waters between Monday and
Tuesday. Although the bulk of moisture associated to the wave will
remain south of the local islands some moisture increase is
expected.


&&

.AVIATION...Mainly VFR conditions will prevail across all terminals
during the next 24 hours. However, the SHRA in route will cause VCSH
across most of the local terminals and TEMPO reductions in VIS are
possible during the afternoon for TJBQ due to VCTS and SHRA. The
winds will be light and variable overnight, but then gradually
turning ESE during the day.


&&

.MARINE...Mariners can expect tranquil marine conditions through
much of the week, with seas below 4 feet and winds at less than
15 knots. However, thunderstorms will develop each afternoon,
especially near the Mona Passage and the Atlantic Coastal waters.


&&

.FIRE WEATHER...Although an increase in the available moisture is
expected, relative humidity values may still fall into the lower
to mid 50s between the late morning and early afternoon hours.
Lack of wetting rains in the forecast across these areas will also
support further drying of soils and fuels. As a result, KBDI and
10-hour fuel moisture values should remain within fire danger
conditions. Taking these factors into consideration, including the
local wind flow peaking at 15-20 mph and considering the chance
for lightning activity in the area, elevated fire weather
conditions are expected across the southern coastal plains of
Puerto Rico today. For this reason, a Fire Danger Statement has
been issued.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 77 89 78 / 40 50 30 40
STT 90 78 88 78 / 40 40 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
419 AM AST Sat Aug 7 2021

.SYNOPSIS...

Drier air with stable conditions aloft will continue today through
part of Sunday producing relatively calm weather conditions
similar to what we have been having in the last couple of days.
Similarly, still, some showers are likely to develop in the
afternoon in western and interior Puerto Rico. On Sunday afternoon,
a tropical wave will make its way across the region. Increased
shower and thunderstorm activity are likely. The most active day
for the next week currently looks to be Wednesday, associated with
another, stronger, tropical wave making its way through the area.

&&

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

Mid level ridge will hold through early next week. This will help to
maintain a relatively dry and stableatmosphere across the region
over the next 24 hours. Therefore, expect a generally fair weather
pattern prevailing across the local islands today with some showers
developing over the western interior of Puerto Rico this afternoon
due to the sea breeze convergence. Elsewhere, conditionsshould
remain dry with mostlysunny skies.

Then, a tropical wave is forecast to move into the Eastern Caribbean
on Sunday. As a result, moisture will increase across the local
islands resulting in scattered showers at times. The presence of the
high pressure at mid level will affect the intensity and duration of
the showers associated with the tropical wave. Although showers and
a few thunderstorms are anticipated with the wave late Sunday into
Monday, no widespread shower activity is forecast at this time due
to weak instability aloft. The drier and stable air masswill return
onMonday morning as the tropical wave exits the forecast area.

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

The long-term period continues to appear very active. A tropical
wave located about 700 miles east of the Lesser Antilles is being
monitored by the National Hurricane Center, although, at the moment,
significant development of this system is not anticipated. So far,
model guidance continues to suggest this system will pass through
the forecast area as a vigorous tropical wave between late Tuesday
through late night Wednesday, however some discrepancies exist
between models and each model cycle regarding its strength. GFS
shows a more bullish solution compared to ECMWF with both showing
the bulk of the activity over northeastern Caribbean; but there
is still uncertainty regarding the tracking of the system. The
eventual path and strength of this tropical wave will determine
how significant the impacts will be and which locations will
affect the most. Therefore, please continue to monitor the latest
forecasts during the next couple of days. Nevertheless, expect a
very moist and unstable weather environment across the forecast
area, with high potential for widespread convection and heavy
rainfall. Urban and small stream flooding can be expected in areas
with the heaviest showers. Flash flooding events cannot be ruled
out with this activity.

Between Thursday through Friday lingering moisture from the tropical
wave will produce a more seasonal weather pattern with showers and
isolated thunderstorms over the west in the afternoon and passing
showers across the eastern third of Puerto Rico and USVI during
overnight and morning hours. For the weekend, confidence in the
forecast is low as many discrepancies remain regarding the
presence close to the region of another strong tropical wave.


&&

.AVIATION...

VFR conditions will prevail thru the forecast period. SCT SHRA
possible to develop over the western interior PR between 07/18Z-21Z
with VCSH near TJMZ. Mountain obscurations over western interior of
PR are likely in the afternoon. ENE winds of 15-25 kts with
occasional higher gusts are forecast below FL150.


&&

.MARINE...
Relatively tranquil to slightly choppy marine conditions are
expected with seas 2 to 5 feet for the next several days. Winds
will be from the east at 10 to 15 knots. For the beaches, the rip
current risk is moderate for the northern and northwestern coast
of Puerto Rico, and some beaches of eastern Culebra and eastern
tip of St. Croix.


&&

.FIRE WEATHER...Slightly lower moisture content is expected through
early this afternoon, before patches of moisture reaches the
local islands. As a result, relative humidity values are forecast
to fall into the mid 40s to low 50s between the late morning and
early afternoon hours. Lack of wetting rains in the forecast
across these areas will also support further drying of soils and
fuels, maintaining KBDI and 10-hour fuel moisture values within
fire danger conditions. Taking these factors into consideration,
including the local wind flow peaking at 15 mph with higher gusts,
elevated fire weather conditions are expected across the southern
coastal plains of Puerto Rico today. For this reason, a Fire
Danger Statement has been issued.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 88 79 / 20 40 50 50
STT 90 78 89 78 / 30 40 50 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
418 AM AST Sun Aug 8 2021

.SYNOPSIS...Two tropical waves will affect the islands during the
next few days. The first one will move across the region today
followed by a stronger wave on Tuesday. The second wave will have
higher potential for producing widespread shower activity and
flooding across the forecast area between Tuesday and Wednesday.

&&

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

A tropical wave will move across the local islands today. Satellite-
derived precipitable water (PWAT) imagery shows an area of enhanced
moisture over the Leeward Islands, with values around 1.9 inches.
This feature will advect showers and thunderstorms through the day
across the area, but also will contribute in convective development
across the interior, west, and portions of the San Juan metro area.
Urban and small stream flooding will be possible with the strongest
activity. The wave should depart tonight and it will be replaced by
a drier air mass on Monday. PWAT values will be plummeting to 1.1 to
1.2 inches, which is below the climatological value for this time of
year. As a result, shower activity should be limited across the
area.

The quiet weather will not last, however, as a strong tropical wave
is expected to reach the islands by Tuesday. This wave is currently
monitored by the National Hurricane Center for the potential for
tropical cyclone formation. There is some discrepancies between the
global models on how strong this system is going to be when it moves
through the area. Regardless of development, squally weather is
anticipated, with periods of gusty winds and heavy rain. Urban and
small stream flooding, as well as rapid rises in rivers, mudslides
in steep terrain, as well as flash flooding will be possible with
this event. Please continue to monitor the products issued by the
National Hurricane Center and the San Juan Weather Forecast Office
for the evolution of this system, updates to the forecast and
further details.

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

Trailing moisture will continue to affect the local islands
on Wednesday in the wake of the strong tropical wave. This
combined with a deep layer southeasterly flow will favor very
moist and unstable conditions over Puerto Rico and the US Virgin
Islands. As a result, additional showers and thunderstorms will
likely affect the islands by midweek and may bring extra 1-2
inches of rain to the local islands on Wednesday. Hopefully, these
rounds of showers will bring beneficial rains to the south
central portions of Puerto Rico as well as portions of the U.S.
Virgin Islands that are experiencing drought conditions. Then, a
drier trend is likely Thursday and Friday as a Saharan Air Layer
will move over the northeast Caribbean. Although conditions
improve the second part of the work week, trade wind showers are
possible across the forecast area from time to time.

Wetter conditions will likely return during the weekend as another
tropical wave is suggested by the operational models. This wave
has a well-defined moisture plume associated with it, and could
result in another round of widespread rainfall across the islands
between Saturday and Sunday. A favorable MJO pattern will persist
across the Atlantic basin, supporting this unsettled scenario for
the following weekend.

&&

.AVIATION...A tropical wave will bring SHRA/TSRA for the local
area today. The Leeward Terminals should see VCTS through 18Z. For
Puerto Rico/USVI terminals, VCTS is expected between 14-20Z,
which could result in TEMPO groups due to reduced VIS and low
ceilings. Winds will be out of the east at 10 to 15 knots with
stronger gusts.

&&

.MARINE...Broad high pressure across the north Atlantic will
maintain a moderate easterly wind flow through at least early next
week. Seas will range from 3 to 5 feet across most of the local
waters. A tropical wave will enter the local waters today
increasing the shower and thunderstorm activity over the local
waters and passages. Another tropical wave is forecast to reach
the region between Tuesday and Wednesday, increasing the winds and
seas across the local waters as well as producing choppy conditions
especially across the offshore waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 78 87 79 / 70 50 10 60
STT 89 79 90 78 / 60 50 10 70

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
447 AM AST Mon Aug 9 2021

.SYNOPSIS...Drier air and fair weather conditions are expected
today across the islands. For Tuesday and Wednesday, Invest 94L is
forecast to move across or close to the local area, increasing the
potential for flooding rains across portions of the islands, and
gusty winds in general. A Saharan Air Layer is expected to move
over the region during the end of the workweek, promoting hazy
skies and limited shower activity. Moisture increases again during
the weekend with the passage of a tropical wave.


&&

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

A drier airmass is making its way into the region. Total
Precipitable Water imagery from GOES-16 indicates that this airmass
is significantly drier than seasonal normals, with PWAT of 1.2 to
1.3; these values are currently just east of the Virgin Islands,
likely to arrive there in the coming hours, and eastern Puerto Rico
by mid-morning. This will suppress shower activity over the region,
and relatively calm weather is expected today. That being said, a
few showers are possible, due to local effects and daytime heating
interacting with the available low-level moisture, mostly in western
and interior Puerto Rico. High forecast confidence today and tonight.

On Tuesday, a tropical disturbance, specifically Invest 94L, will
make its way into the region. Currently, the National Hurricane
Center has the potential for development into a tropical depression
at 50% in the next two days. Regardless of development, significant
moisture will make its way into the region during the day on
Tuesday; enhanced moisture will persist through Wednesday.
Widespread shower activity and isolated to scattered thunderstorms
are expected. Periods of moderate to heavy rainfall and gusty winds
are likely. In southern and eastern Puerto Rico, rainfall totals in
excess of 2-3 inches are possible; elsewhere, amounts in excess of 1-
2 inches. As such, there is significant potential for urban and
small stream flooding, with the risk of flash flooding in some
areas, as well as mudslides in areas of steep terrain. Forecast
confidence is moderate to high; this is mostly for uncertainty in
details, not in the potential for significant heavy rainfall and
hazardous conditions.

Updates on development potential, as well as any track and intensity
forecasts, should they become necessary, will come from the National
Hurricane Center. Anyone with interests in and around Puerto Rico
and the U.S. Virgin Islands should carefully monitor future
forecasts and products from this office and from the National
Hurricane Center for updates.

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

A Saharan Air Layer is expected to move on Thursday and linger
through at least Friday across the region. This will cause a drop
in precipitable water content and promote hazy skies, as well as
limited shower development in diurnal activity over western Puerto
Rico. Therefore, expect mainly fair weather conditions across the
islands, with a few light passing showers at times across the
USVI and eastern sections of PR during the night and early
morning hours, followed by measurable rainfall amounts over the
west coast of PR each afternoon.

For the weekend, a tropical wave with plenty of moisture is forecast
to move across the region on Saturday, increasing shower and
thunderstorm development across the local waters and islands.
However, model guidance from the GFS and ECMWF differs on the
timing of another tropical wave, passing mostly south of the
region, but increasing moisture content across the local area.
The ECMWF has a faster solution for Sunday, and the GFS a slower
solution for Monday.


&&

.AVIATION...Generally VFR conditions are expected for the next 24 hours. Showers
likely to be limited to western and interior PR, with VCSH
conditions possible for TJBQ this afternoon; no operational impacts
expected. Winds increase this morning, remaining out of the east
with speeds to near 15 knots, with sea breeze variations. Winds
subside again overnight tonight.


&&

.MARINE...Small crafts should exercise caution today across the
offshore Caribbean waters and both Anegada and Mona Passage due to
winds up to 20 knots and seas up to 6 feet(Anegada Passage).
Elsewhere, seas should remain around 4 feet or less, and winds up
to 15 knots from the east are expected to prevail. Winds and seas
are expected to gradually deteriorate on Tuesday and Wednesday
as a surface low pressure system moves close or across the region.
Shower and thunderstorm activity will also increase in general
across most of the waters. Small Craft Advisories will be in
effect on Tuesday morning.


&&

.FIRE WEATHER...Limited shower activity and drier conditions are
expected along the southern coast of Puerto Rico today. In
addition KBDI values remain well above critical fire weather
values. Please refer to the latest Fire Danger Statement(RFDSJU)
and Fire Weather Planning Forecast for Puerto Rico(FWFSJU) for
detailed information, especially for the southern coastal plains
of Puerto Rico.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 78 85 76 / 20 40 70 60
STT 90 78 86 79 / 10 70 70 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
459 AM AST Thu Aug 12 2021

.SYNOPSIS...Drier air with Saharan dust will cause hazy skies and
limited shower activity across the islands today. Moisture content
will gradually increase on Friday into the weekend, ahead of a
tropical wave, that is expected to move across the region on
Saturday. A more vigorous tropical wave is expected to follow
between Sunday/Monday. A Saharan Air Layer with drier air is
forecast to move across the region by early next week.


&&

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

A drier airmass is pushing into the region from the east. Based on
Total Precipitable Water imagery from GOES-16, moisture is below
seasonal normals already in some parts of the east. This will
spread westward through the morning. Though lingering low-level
moisture will likely support some showers, activity will be
significantly inhibited. The moist layer is expected to be
relatively shallow, likely less than 6000 feet, which will also
prevent significant convective development. Similar conditions
are expected tomorrow.

On Friday night, a tropical wave is forecast to enter the region,
bringing enhanced moisture. Weak troughing at the mid- and upper-
levels will also promote instability over the region. Moisture and
instability will lead to the return of an active weather pattern
into the weekend.

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

A vigorous tropical wave over the central tropical Atlantic is
expected to bring showers and thunderstorms across the region
between Sunday and Monday. Currently, NHC is forecasting this wave
to develop into a tropical depression by early next week. As of now,
the main risk associated to this wave is flooding, and a Flash Flood
Watch could be required on Sunday for PR and the USVI. Please
continue to monitor the development of this tropical wave.

A Saharan Air Layer with suspended dust and drier air is expected
to move by Tuesday, and linger through much of the workweek.
Overall fair weather conditions are expected from Tue-Thu, before
the next tropical wave enters the eastern Caribbean on Friday,
increasing shower and thunderstorm activity across the local
waters and islands.


&&

.AVIATION...Generally VFR conditions are expected across all
terminals for the next 24 hours. VCSH conditions possible at TJBQ,
with SHRA likely remaining south of the terminal, during the
afternoon. Winds generally out of the east, increasing to 10 to 15
knots during the day, then subsiding after sundown.


&&

.MARINE...Choppy wind driven seas will continue across the
offshore and eastern waters of the islands today. Seas should
remain at 6 feet or less and winds up to 20 knots can be expected
in general. Winds and seas will gradually improve on Friday and
Saturday, increasing once again on Sunday with the tropical wave
passage. There is a moderate risk of rip currents for most of the
eastern, northern and southern beaches of the islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 78 88 78 / 20 20 20 30
STT 90 78 90 79 / 20 20 20 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
424 AM AST Fri Aug 13 2021

.SYNOPSIS...East to northeast trades are expected today, as well
as drier air ahead of a tropical wave that is expected to move
across the area from late tonight into Saturday. Invest 95L is
expected to move between Sunday and Monday across the region,
increasing shower and thunderstorm activity with strong gusty
winds.


&&

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

Generally fair weather is expected during the day today. A Saharan
Air Layer persists over the region, maintaining dry mid levels. This
will inhibit convective development. Local effects and daytime
heating will combine with the available moisture in the low levels
to generate some showers, mostly in western and interior Puerto RIco
into southwestern Puerto Rico. Cannot entirely rule out a
thunderstorm or two, but thunderstorms are generally not likely.
High confidence in forecast for day one.

Overnight tonight into tomorrow morning, a tropical wave is forecast
to arrive. This will bring increasing moisture to the region and a
return of generally unsettled conditions. There is some disagreement
from the models on the timing for this system; at present, the GFS
lags a little behind current conditions. The Euro, on the other
hand, looks to be a bit too quick. This timing trend is maintained
through the end of the short term period. Regardless, expect active
conditions starting during the night tonight and through much of the
day, if not all day, tomorrow. Forecast confidence moderate to high,
largely because of the timing, though the effects of the system
behind the wave cannot be discounted, and there is a fair bit of
uncertainty there.

And on time marches into Sunday. Confidence in Sunday`s forecast is
not great. Well, the general idea that it`s going to be wet for much
of the day is a pretty high confidence forecast. I`ll even grant
that it`s fairly likely to be a bit gusty. Beyond that - the details
remain hazy. What is presently Invest 95L is expected to be
affecting the region on Sunday. According to the National Hurricane
Center, this invest currently has a 70% chance of forming into a
tropical depression within the next 48 hours. Currently, however, it
remains a disorganized low pressure system with lopsided convective
activity. Obviously, the forecast for Sunday is highly dependent on
what happens with this invest, and that remains uncertain. With a
70% chance of forming a tropical cyclone, however, it would be
prudent to take that as the most likely scenario, and plan
accordingly. And, regardless of development, or lack thereof, there
will be substantial moisture brought into the region by this system,
and sufficient instability to aid in the development of widespread
shower activity.

All individuals with interests in Puerto Rico and the USVI should
monitor closely future forecasts from this office, as well as from
the National Hurricane Center for updates on Invest 95L.

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

Weather conditions on Monday will depend on the development of the
current low pressure system (95L) that is located about 1000
miles east of the Leeward Islands. The ECMWF has a faster
solution(Sunday) and westward track than the GFS, with the GFS
bringing the disturbance on Monday and tracking northwestward.
Regardless, an increase in showers and thunderstorms, as well as
strong gusty winds is likely across the region from Sunday into
Monday.

Thereafter, a building ridge northeast of the region should
promote an east to southeast wind flow, and a drier air layer
between 700MB-500MB. However, precipitable water content is
forecast to remain at near normal levels through the workweek,
providing the necessary moisture content to aid in the development
of afternoon showers each day across portions of the interior and
western PR, and from shallow passing showers during the night
across the USVI and eastern sections of PR. A Saharan Air Layer
could move across the eastern Caribbean late in the workweek.


&&

.AVIATION...Generally VFR conditions are expected for the next 24
hours. VCSH possible TJBQ this afternoon for SHRA that are
expected to stay to the south of the terminal. After around
14/01Z, conditions could deteriorate for eastern terminals with
arrival of tropical wave. VCSH likely for TIST/TISX/TJSJ/TNCM/TKPK
by end of period, with potential for MVFR or worse.


&&

.MARINE...Seas will continue to improve today and Saturday.
Easterly winds should remain around 15 kt or less today. A low
pressure system is expected to increase winds and seas across the
regional waters, as well as shower and thunderstorm activity from
Sunday through Monday. There is moderate risk of rip currents
across most of the east, north and southern beaches of the
islands.


&&

.FIRE WEATHER...There is an elevated fire danger potential along
the southern coastal plains of PR, due to the expected low
relative humidity, breezy conditions along the coast due to the
sea breeze, and high KBDI values. Please refer to the latest Fire
Danger Potential (RFDSJU) for more information.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 78 89 80 / 20 40 40 40
STT 90 80 88 79 / 30 50 50 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
338 AM AST Wed Aug 18 2021

.SYNOPSIS...

A strong trade wind cap with dry air at mid-levels and African
dust particulate will promote stable weather conditions and hazy
skies across the islands through at least Thursday. A tropical
wave will increase the available moisture and the chance for
showers and thunderstorms by Thursday, though the bulk of the
moisture is forecast to remain well south across the Caribbean
Sea. The lingering moisture will stay with us until Friday. Once
again, maximum temperatures will range in the low 90s across the
coastal and urban areas.

&&

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

A mid and upper-level ridge and Saharan dust will remain over the
area through the short-term period. Saharan dust will increase on
Thursday when a wind surge ahead of a tropical wave advects a robust
plume of Saharan dust over the region. Hazy conditions will persist
now through the end of the week. As for moisture and showers during
the short-term period, easterly winds will advect shallow moisture
over the area during the early morning over portions of eastern and
northern Puerto Rico and the local waters. Then during the
afternoon, sea-breeze and surface heating will promote shower
development mainly across the western areas of Puerto Rico. The best
rain chances will be Thursday afternoon through Friday when a weak
tropical wave moves over the local waters and increase low-level
moisture. Although low-level moisture will increase in the low-
levels of the atmosphere, the GFS and ECMWF keep the deep moisture
confined to 1000 to 850 MB and has relatively modest moisture in the
mid-level of the atmosphere. Nevertheless, local and diurnal effects
will aid in the development of single cell thunderstorms mainly
across the western and interior areas of Puerto Rico that could
cause brief flooding. High-res and ensemble models show very little
rainfall through Friday due to the high-pressure and limited mid-
level moisture.

Daytime high temperatures across the region will be near the upper
80s to lower 90s in lower elevations and the upper 70s to lower 80s
in higher elevations due to easterly wind flow during the short-term
period.

.LONG TERM...SATURDAY THROUGH TUESDAY...

A drier than average air mass will remain across the islands on
Saturday morning, limiting rain activity. However, a tropical
wave is forecast to interact with a retrograding TUTT-low Saturday
afternoon into Sunday, increasing instability across the
Northeast Caribbean, especially Sunday afternoon.

As the tropical wave moves eastward into the Hispanola, a dry air
mass is forecast to arrive, limiting moisture across the U.S.
Virgin Islands and Puerto Rico. This dry air will cause that
above-average moisture content return across the region with an
extensive African dust event Monday through mid-week.


.MARINE...

Calm marine and weather conditions will persist across the local
waters through at least tomorrow. Mariners can expect seas at 5
feet or less and winds around 15 knots, except across the Anegada
Passage where easterlies will fluctuate between 15 and 20 knots. A
tropical wave will increase the chance to observe isolated to
scattered showers and isolated thunderstorms across the local
waters Thursday through Friday.

Beachgoers, there is a moderate risk of rip currents across some
beaches of northwest and southeast PR, eastern Vieques and Culebra
and the south and east coast of St Croix.

&&

.AVIATION...

VFR conditions are expected at all TAF sites during the forecast
cycle. VCTS possible in and around JBQ between 18/17z and 18/22z.
Easterly winds at 10 to 15 knots with higher gusts and sea breeze
variations aft 18/13z.

&&

.MARINE...


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 79 88 78 / 20 20 40 50
STT 89 79 90 79 / 20 20 40 40