Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
436 AM AST Sun Jul 15 2018


.SYNOPSIS...
Showers will affect the windward areas as the trade winds advect
moisture into the region. Hazy skies will persist over the
islands. An area of subsidence ahead of the tropical wave will
limit shower activity during the afternoon. A tropical wave will
makes its way into the region late tonight and Monday. This wave
will aid in the development of showers and thunderstorms on
Monday. Another tropical wave is forecast to move into the region
by Thursday.

&&

.Short term...Today through Tuesday...
Moderate high pressure at the surface continues to drive trans-
Atlantic trade wind flow over the area laden with fine Saharan dust
that will continue through the period at our latitude. The tropical
wave that went through on Saturday was highly tilted with latitude
toward the east and we are only now beginning to leave the moisture
of the tip. Moisture from the wave upstream broke off in faster flow
at its vertex and is now rotating into another band that is passing
through the Leeward islands and will enhance shower activity today.
Moisture associated with the next tropical wave near 53 west will
pass through the area during the 24 hour period beginning at 16/12Z
Monday. During this period high pressure aloft will be over the
Leeward islands and will move west southwest, leaving the local
forecast area in a somewhat subsident anti-cyclonic flow. An east-
west upper level trough associated with a low now well northeast of
the local area is moving south but will not arrive in the local area
until Tuesday. Some dynamics associated with it will move over
eastern Puerto Rico and the U.S. Virgin Islands and will enhance
continued showery weather--mainly over Saint Thomas and eastern
Puerto Rico Tuesday morning. Drier air moving into the forecast area
on Tuesday will limit but not eliminate the afternoon shower
activity in western Puerto Rico.

MEX model output statistics (MOS) temperatures have been running a
little too high, possibly because of the relatively strong easterly
trade wind flow that has kept temperature along the coast well
moderated on both northern and southern Puerto Rican coasts and in
the U.S. Virgin Islands. This trend should end on Tuesday when we
begin to see more southeasterly flow over the area. Temperatures on
the north coast will then move into the lower 90s in the lower
elevations.

Winds over the area are expected to diminish somewhat over the area
on Tuesday. Until then coastal winds will run 15 to 20 mph with
gusts up to 30 mph.

.LONG TERM...Wednesday through Sunday...
A drier air mass with more Saharan dust particulate will move ones
again across the region. In addition a mid level high pressure
will build over the region by that time. Under this weather
pattern, very limited precipitation and hazy conditions are
forecast to persist once again on Wednesday.

Model guidance continues to indicate the arrival of an active
tropical wave with much better upper level support by Thursday.
Although is still too early in the forecast package, Thursday
looks as the wettest day in the Long-term forecast.

After the passage of Thursday-Tropical wave, dry air will filters
in once again across Puerto Rico and the U.S. Virgin Islands. As
a result, limit shower activity with hazy skies should return by
Friday into the upcoming weekend. However, a retrogressive TUTT
low is forecast to amplify over the region, which could provide
enough instability to create a Climatological pattern by the
second part of this week.

&&

.AVIATION...
Isold -SHRA bcmg sct-numr aft 15/16Z mainly wrn PR. Mtn
obscurations entire pd. Winds easterly 5 to 15 kt bcmg 10-20 kt aft
15/15Z with sea breeze influences exc interior PR. Max winds east
btwn FL040-200 and WSW FL390-480 both lyrs 20-25 kt.

&&

.MARINE...Breezy trade winds will continue to produce choppy seas
across the local waters. Therefore, mariners should exercise
caution due to seas between 4 and 6 feet and winds between 15 to
20 knots with higher gusts. Monday`s tropical wave could deteriorate
marine conditions enhancing shower and thunderstorm activity, especially
over the Offshore waters. Seas are forecast to build at 5 to 7
feet Monday and Tuesday. Marine community should monitor marine
conditions as model guidance continues to indicate choppy/rough
seas through much of the forecast period.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 78 88 80 / 40 60 50 50
STT 90 80 88 79 / 40 50 50 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
509 AM AST Mon Jul 16 2018


.SYNOPSIS...
A tropical wave is expected to bring showers across the U.S.
Virgin Islands and the eastern half portion of Puerto Rico
throughout the day. This activity is expected to spread along,
and to the north/west of the Cordillera Central during the
afternoon hours. The lingering moisture of this wave will remain
across the area through at least Tuesday afternoon, when a dry air
mass with Saharan dust particulates filters from the east across
the islands Tuesday and Wednesday. An active tropical wave is
expected to move across the islands on Thursday.

&&

.SHORT TERM...Today through Wednesday...
Even though some Saharan dust is present, a tropical wave with
axis currently over the U.S. Virgin Islands is bringing an
increase in moisture across the local islands. Scattered to
locally numerous showers are expected this morning across the
local waters, USVI, and eastern PR. This tropical wave has some
but not a lot of cloudiness with it, and it is expected to
continue bringing deeper moisture through the day. This means that
for the afternoon hours, the western and northwestern sections of
PR can observe showers and thunderstorms due to the combination
of the moisture with the local effects and diurnal heating, but
also eastern PR can continue to experience showers that move in
from the east, decent rainfall accumulations that can cause minor
flooding can be expected across these areas today. However, the
USVI and Vieques and Culebra seem to have a lesser chance of
significant rainfall accumulations. The wind will prevail from the
east at 10-15 mph mainly with occasional gusts. The daytime max
temperatures are expected to be in the mid to upper 80s across the
lower elevations and in the upper 70s to low 80s across the
higher elevations.

Much drier air will make a return on Tuesday and Wednesday with haze
being more obvious due to Saharan Dust. Isolated light showers can
be expected across the USVI and eastern PR during the night time and
early morning hours, with scattered showers and isolated
thunderstorms in the afternoon across western PR. However, due to
Saharan dust, the available moisture will be limited and therefore
the afternoon activity may be short lived and with limited coverage.

.LONG TERM...Thursday through Monday...
Model guidance suggests the arrival of an active tropical wave
with TPW around 2 inches, which is above the normal values for
July local climatology (percentile 75th). Although the TUTT low is
not in the best location, a sudden drop in the upper level
pressure was suggested, which could increase upper level support
during the afternoon hours. Although is still too early in the
forecast package, Thursday looks as the wettest day in the Long-
term forecast.

Drier weather conditions with suspended Saharan dust particulates
will return after the passage of Thursday-Tropical wave, limiting
shower activity and creating hazy skies through at least the
upcoming weekend. During the weekend, patches of low level
moisture will interact with a retrogressive TUTT low, which could
provide enough instability to create a Climatological pattern
through early next week.

&&

.AVIATION...Tropical wave is bringing SHRA to the local area.
Therefore VCSH is expected across most of the local terminals
through the day today. Brief periods of MVFR conds are possible as
SHRA briefly reduce visibility and also there may be occasional
brief MVFR ceilings. Winds will be mainly from the east at 10-15KT
with occasional gusts. Weather to improve after 17/00Z.

&&

.MARINE...
Choppy seas are expected to continue with wave-heights between 4
and 6 feet and winds between 15 and 20 knots. Mariners are urge to
exercise caution across most of the local waters. Shower and
thunderstorm activity is expected to increase, especially during
the afternoon hours, as a tropical wave cross the region today.
Breezy easterly winds will continue to result in choppy seas
through much of the week.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 80 90 80 / 70 40 40 40
STT 88 79 89 80 / 40 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
405 AM AST Wed Jul 18 2018

.SYNOPSIS...Strong high pressure across the north central
Atlantic will prevail for the next several days, causing a
generally easterly wind flow across the local area. Saharan dust
and haze will be evident today with relatively dry air. A tropical
wave is expected on Thursday, bringing moisture, shower and
thunderstorm activity to the local area. Drier air and Saharan
dust returns to the area on Friday. Upper low to remain to the
northeast of the local islands for the next few days.

&&

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

Partly cloudy and hazy skies prevailed across Puerto Rico and the
U.S. Virgin Islands overnight. Some showers were noted across the
offshore Atlantic and Caribbean waters. Few showers were also
observed moving across inland Puerto Rico. These showers were moving
quickly westward. Local area remains under a stable air mass. This
air mass is maintaining relatively dry weather conditions across the
region Saharan dust will continue to linger across the area through
at least Thursday.

Am increase in low level moisture is expected late tonight into
Thursday morning as a tropical wave approaches the local islands
from the east. This tropical wave will bring an increase in low
level moisture across the region. As a result, showers with
thunderstorms are expected to affect the region early Thursday
continuing through the evening hours. The heaviest activity should
occur across the western interior and northwest sections of Puerto
Rico Thursday afternoon. After the passage of this wave, a return to
hazy conditions and limited shower activity is expected on Friday.

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

A somewhat seasonal pattern is expected in the long term with
Saharan dust present across the local area through the weekend,
improving during the beginning of the following workweek. An upper
low will cause a few surface troughs which may bring patches of
moisture and some showers but at this time the rainfall and
thunderstorm activity looks limited to areas enhanced by local
effects. Deeper moisture is expected on Monday with one of the
induced surface troughs, so scattered to locally numerous showers
and isolated thunderstorms are in the forecast for Monday
afternoon and evening. Otherwise, isolated to scattered showers
are expected during the night time and early morning hours across
the local waters, USVI, and eastern PR, with scattered showers and
a few thunderstorms possible across western PR in the afternoon
hours.


&&

.AVIATION...VFR conditions expected across the local terminals with
VCSH for the USVI and TJSJ terminals in the morning. Limited afternoon
convection may cause VCSH/VCTS at TJMZ and TJBQ after 18/16Z.
Winds will be from the east at around 10KT through 18/13Z,
increasing thereafter to about 15KT with sea breeze variations
also developing around that time.


&&

.MARINE...Choppy seas up to 6 feet expected for the next several
days with winds up to 20 knots. There is a moderate risk of rip
currents across most of the local beaches of Puerto Rico, Vieques,
Culebra, and Saint Croix.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 78 87 78 / 40 70 70 20
STT 83 79 83 81 / 40 40 40 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
407 AM AST Thu Jul 19 2018

.SYNOPSIS...Tropical wave to move through the local area today,
bringing an increase in moisture, showers and isolated
thunderstorms. Strong surface high pressure across the north
central Atlantic will keep easterly winds for the next several
days. Drier air mass and Saharan dust expected to return on Friday
and Saturday. Upper low northeast of the Leeward islands may
strengthen and move west and north of the local islands for the
next few days, possibly causing some instability on Sunday.


&&

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

Increasing cloudiness with shower and thunderstorm activity was
observed across Puerto Rico and the U.S. Virgin Islands overnight.
Scattered to numerous showers with isolated thunderstorms began to
move across the region as a tropical wave approaches from the east.
Most of the activity occured across the local waters. Some showers
were moving quickly across the San Juan metropolitan area.

For today, a tropical wave will move across the local islands. As a
result, scattered to numerous showers with thunderstorms will spread
across the U.S. Virgin Islands and eastern half of Puerto Rico
during the morning hours, and across the rest of Puerto Rico this
afternoon and tonight. Moisture associated with the tropical wave
will linger across the region through late tonight into Friday
morning. By Friday morning, a very dry air mass with Saharan dust is
expected to encompass the region. This dry weather pattern will
continue into Saturday.

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

Some Saharan dust may still be lingering on Sunday morning, but a
break from the Saharan dust is expected early next week. An upper
low may combine with the available moisture to cause some showers
and isolated thunderstorms on Sunday. Then drier air expected on
Monday and Tuesday may limit shower activity before another
tropical wave approaches for Wednesday, which will cause an
increase in shower activity once again. Thereafter, drier air
returns and mainly locally induced showers across Puerto Rico are
expected, isolated and brief showers expected elsewhere.


&&

.AVIATION...Periods of MVFR conditions can be expected from time to
time across TJSJ, TIST and TISX throughout the day. Periods of MVFR
and even IFR conditions will be possible across TJMZ and TJBQ this
afternoon due to +SHRA/+TSRA. Low level winds will be mainly east to
east southeast at 10 to 15 kts with higher gusts.


&&

.MARINE...Choppy seas up to 6 feet expected today and for the next
few days with easterly winds up to 20 knots. For that reason,
small craft operators are urged to exercise caution cross many of
the local waters. The tropical wave will cause showers and
isolated thunderstorms across the local waters today.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 79 89 78 / 70 20 20 20
STT 83 81 83 79 / 40 20 20 20

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
438 AM AST Fri Jul 20 2018

.SYNOPSIS..Strong surface high pressure will continue to produce
moderate to fresh trade winds across the region. Patches of low
level moisture will affect the local region from time to time.

&&

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

Drier air and Saharan dust are making its way back into the local
area. Shower activity has been gradually diminishing overnight and
the shower activity is expected to remain fairly limited today and
Saturday as this drier air mass with a good amount of Saharan dust
remains over the local area. Having said that, the limited available
moisture should combine with the local effects and diurnal heating
this afternoon and cause a few showers across northwestern PR, but
the amounts are not expected to be enough to cause flooding, except
for perhaps a small area due to an isolated strong shower that may
cause ponding of water. But generally hazy skies and fair weather is
expected today and through Saturday morning. The high resolution
models are suggesting that a small area in southwestern PR may
observe heavy showers for a brief amount of time, otherwise the rest
of PR and the USVI should remain with fair weather and hazy skies.

Sunday looks like it has a better chance for significant showers and
thunderstorms across western PR and near the San Juan Metro area,
but the rest of PR and the USVI should still have mainly fair
weather with brief isolated showers. The afternoon showers
convection may enhanced because of an upper low that may be better
positioned to cause divergence in the upper levels and much weaker
CAP inversion, compared to Saturday, as suggested by the forecast
soundings.

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

Strong surface high pressure will maintain moderate to fresh trade
winds across the area through the forecast period. These winds
will transport patches of low level moisture through the area from
time to time. Next tropical waves will pass mainly south of the
area without any significant changes in the current weather
pattern.

&&

.AVIATION...VFR cons expected today with brief -SHRA in the morning
hours. Hazy conditions due to Saharan dust but visibility should
remain P6SM. Winds will be mainly from the east at around 15KT and
gusty after 20/13Z, sea breeze variations should develop thereafter
as well. Limited SHRA activity is possible near TJBQ and TJMZ after
20/16Z. Winds to decrease to 5-10kt after 20/23Z.

&&

.MARINE...Seas up to 6 feet and winds up to 20 knots are expected
to prevail across most local waters through at least Sunday. As a
result, small craft operators should exercise caution.


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
443 AM AST Sat Jul 21 2018

.SYNOPSIS...Strong surface high pressure will continue to produce
moderate to fresh trade winds across the region. Saharan Air Layer
will continue to move across the region today. Patches of low
level moisture will affect the local region from time to time. A
tropical wave will approach the local region mid next week.

&&

.SHORT TERM....Short term...Today through Monday...

Overall dry and stable air mass will persist across the region
through the rest of the weekend,under the influence of the strong
surface high pressure spread across the central and northeastern
Atlantic. The extensive Saharan Air Layer will continue to move
across the region today to maintain hazy conditions with moderate to
high concentrations of suspended dust particulates across the
region. The dusty layer is however expected to diminish in
concentration later this evening through Sunday. In the meantime,a
few shallow low level clouds and passing showers of light to
moderate intensity will affect the regional waters and may brush
parts of the east coastal sections of the islands from time to time.
No significant rainfall accumulation is however forecast. Local and
diurnal effects will give way to some afternoon convection mainly
over the central and west sections of Puerto Rico with mostly sunny
and hazy conditions elsewhere including the U.S. Virgin islands.

On Sunday...recent model guidance suggests no significant changes
with Tutt low to linger north of the region while associated trough
is to retrogress slight westward across the areas while providing
better ventilation aloft and slightly increasing instability aloft.
This combined with the available moisture accompanying a weak Tutt
induced easterly perturbation will give way to early morning and
afternoon showers with a better chance for isolated thunderstorms
over the west sections of Puerto Rico. Similar conditions expected
on Monday as the lingering upper trough combined with available
moisture along with local and diurnal effects will again support
afternoon showers and isolated thunderstorm development mainly over
the northwest sections of Puerto Rico as the local wind flow is
expected to become more southeasterly. Mostly sunny and fair weather
skies is forecast to prevail elsewhere including over the U.S.
Virgin islands.

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

For Wednesday, a tropical wave is expected to move across the
region. Increasing moisture and instability is forecast with the
passage of this wave. After the passage of this wave, a return to
a more stable and dry weather pattern is then expected. An upper
level trough is forecast to develop across the western Atlantic.
This trough is forecast by computer models to be located in a
favorable area for the development of showers and thunderstorms at
the end of the forecast period.

&&

.AVIATION...Few passing -SHRA/SHRA en route btw the local islands
and ovr ern PR w/brief mtn tops obscr til arnd 21/12Z. VFR will
prevail all TAF sites and across the local flying area. Wnds fm E 5-
15 kt incrg to 10-20 kts with ocnl gusts btw 25-30 kts fm 21/14Z-
21/22z.

&&

.MARINE...Seas up to 6 feet and winds up to 20 knots are expected
to continue across the local waters through at least tonight. As a
result, small craft should exercise caution.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 88 78 / 20 30 30 20
STT 89 78 88 78 / 10 30 30 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
412 PM AST Sat Jul 21 2018

.SYNOPSIS...
An increase in low level moisture can be expected on Sunday as an
upper level trough moves into the forecast area. Passing showers
can be expected in the morning across the USVI, eastern PR and
surrounding waters, followed by showers and thunderstorms
developing across the interior and western portions of PR in the
afternoon. Thereafter, weather conditions will gradually improve
through early next week with patches of moisture moving into the
area on occasion. A tropical wave is expected to move north of
the region brining in fragments of moisture across the forecast
area on Wednesday and Thursday. The GFS suggests an upper level
trough north of the region next weekend, but it is still too soon
to forecast the direct impacts for our local area.

&&

.SHORT TERM...Tonight through Monday...

Tutt low will linger north northeast of the forecast area tonight
and an associated trough will move into the area overnight and
Sunday. The surge in moisture from the trough will bring passing
showers across the eastern half of PR, USVI and the surrounding
waters in the morning hours. In the afternoon, the moisture combined
with the orographic effects will induce shower and thunderstorm
development across the interior and western portions of PR -
especially in and around the sea breeze convergence zone of western
PR. Some isolated showers are possible across some sections of
northeastern PR with the streamers formed from the eastern islands
of PR and USVI in the afternoon. A decrease in Saharan dust is
expected starting Sunday and the shower activity will also help
reduce the amount of suspended particles in our forecast area,
which will allow for better rainfall activity.

On Monday, the mid levels of the atmosphere look to remain fairly
dry according the the GFS model guidance, thus, it is possible
that the vertical development of showers may be limited in the
morning. In the afternoon, upper level trough along with the
lingering moisture will promote another round of showers and
isolated thunderstorms across the interior and northwestern
sections of PR, tapering off in the evening hours. Southeast winds
are expected on Monday, shifting to the east on Tuesday.

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

Mostly fair weather conditions can be expected Tuesday morning,
followed by showers and isolated thunderstorms in the afternoon
particularly across the interior and western portions of PR as a
patch of moisture combines with the local effects. On Wednesday,
a tropical wave will move north of the region brining in fragments
of moisture across the forecast area on Wednesday and Thursday.
This will continue to promote shower and thunderstorm development
in the afternoon hours, particularly over the interior and
western parts of PR. However, the NAAPS Aerosol model guidance
also suggest a surge in Saharan dust starting Wednesday which may
limit some of this rainfall activity.

The GFS model guidance suggests an upper level trough north of
the region, extending into our local area next weekend. Although
it is too early to forecast its exact location at this time, the
proximity of the trough may create favorable conditions for
additional convective activity.

&&

.AVIATION...
VFR conds expected thru the forecast period. SHRA still possible
near TJMZ between 18Z-21Z. Although VIS will remain P6SM, saharan
dust will continue to reduce somewhat the VIS across the flight
area. East winds of 15-25 kt below FL030 decreasing to around 10
kt tonight and overnight.

&&

.MARINE...
Seas 3 to 5 feet and winds of 10 to 15 knots can be expected
during the next few days. Locally higher seas and wind gusts are
possible in and around showers and thunderstorms. Low to moderate
risk of rip currents is expected to prevail during the forecast
period.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
444 AM AST Sun Jul 22 2018

.SYNOPSIS...Surface ridge of high pressure over the central
Atlantic will continue to produce moderate to fresh trade winds. A
surge of low to mid level moisture accompanying an induced low
level trough will continue to move across the region today through
Monday. A Tropical wave will move through the area on Wednesday.

&&

.SHORT TERM...Short term...Today through Tuesday...

The lingering Tutt low and associated trough now extending across
the forecast area into the east central Caribbean, will continue to
lift north and west of the area through Tuesday while gradually
filling/weakening. A surge of low to mid level moisture accompanying
an induced low level trough will continue to move across the region
today through Monday bringing periods of low level clouds and
occasional passing showers to the local waters and parts of the
coastal sections of the islands during the rest of the morning
hours. During the afternoon, the available moisture combined with
the local orographic effects and daytime heating will again
support shower and thunderstorm development across the interior
and western portions of PR. Elsewhere, isolated showers will
remain possible across sections of northeastern PR and around
parts of the San Juan metro. A few cloud streamers and mostly
light showers may also form and extend from the eastern islands of
PR and USVI during the afternoon hours but no significant
rainfall is expected.

Recent model guidance continued to suggest no significant changes in
the upper level pattern for Monday and Tuesday, with Tutt low to
linger north of the region while associated trough is to retrogress
slight westward across the Mona Passage. This anticipated pattern
will provide better ventilation with slightly increasing instability
aloft. This combined with the available moisture will support more
frequent early morning showers, followed by afternoon shower
development and a better chance for isolated thunderstorm activity
over the west sections of Puerto Rico. Convective development should
be focused more across the northwest sections of Puerto Rico, as the
local wind flow is expected to become more southeasterly. Mostly
sunny and fair weather skies is forecast to prevail elsewhere
including over the U.S. Virgin islands although a few showers may
develop in isolated areas. A gradual improvement and lesser moisture
advection is also forecast for Tuesday, however local and diurnal
effects will still support afternoon shower development with a
slight chance of afternoon thunderstorms over the west section of
Puerto Rico.

.LONG TERM...Wednesday through Monday

A Tropical wave will move through the area on Wednesday. As an
upper level trough linger close to the region, the combination of
both systems will enhance the development of showers and
thunderstorms across the local region. After the passage of the
wave, a slot of drier air is forecast to encompass the region on
Thursday. Trade winds will transport patches of low level moisture
through the region afterward.

&&

.AVIATION...VFR conds durg entire prd but Isold-Sct passing
-SHRA/SHRA en route btw islands with ocnl mtn top obscr ovr E PR.
SHRA/isold TSRA will dvlp ovr W PR btwn 22/16z-22/22Z especially
inland along the north coast and in wrn PR. Mtn obscurations will
then bcm widespread over ctrl and wrn PR. Sfc winds East 6 to 12 kt
til bcmg 10 to 20 kt with hir gusts with land/sea breeze influences
aft 22/14z.

&&

.MARINE...Seas between 4 to 6 feet and mainly winds up to 15 kts
are expected across all waters except across the coastal waters of
northern Puerto Rico where winds up to 20 knots are expected. As
a Result, small craft should exercise caution across these waters.



&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
449 AM AST Mon Jul 23 2018

.SYNOPSIS...Tutt low located north of the region with an associated
upper level trough extending west of the region will linger through
Tuesday while slowly weakening. East southeast winds will persist
through at least Thursday, which will help focus most of the afternoon
showers and thunderstorm activity over the interior and northwest sections
of PR. Mostly sunny skies and limited showers can be expected elsewhere
and over the USVI. A weak tropical wave will move across the region
by mid week with another surge of Saharan dust to quickly follow during
the latter part of the work week.

&&

.SHORT TERM...Today through Wednesday...
Partly cloudy skies prevailed across Puerto Rico and the U.S.
Virgin Islands overnight. Scattered showers were seen across the
local waters. Few of these showers affected the eastern half of
Puerto Rico and the U.S. Virgin Islands. Rainfall accumulations
were minimal. A strong surface high pressure system will continue
to dominates the local region. This area of high pressure will
continue to produce moderate to fresh trade winds across the
region. These trade winds will transport patches of low level
moisture across the local islands this morning into the afternoon
hours. This moisture combined with an upper level trough to our
west will result in the development of showers and thunderstorms
mainly during the afternoon hours.

Showers with thunderstorms are expected to develop across the eastern
interior section of Puerto Rico near El Yunque rainforest and across
the western interior and northwest sections of Puerto Rico. Some of
the showers and thunderstorms that could develop near El Yunque could
affect the San Juan metropolitan area and vicinity this afternoon.
Meanwhile, some streamers will form just off the west coast of the
U.S. Virgin Islands. This weather pattern is expected to repeat itself
on Tuesday as synoptic weather pattern is not expected to change
much. A weak tropical wave is still forecast to approach the region
by Wednesday.

.LONG TERM...Thursday through Tuesday...
Southeasterly winds are forecast to persist with patches of trade
wind moisture trailing a tropical wave expected to move through
the area through Thursday. Therefore locally and diurnally induced
afternoon convection will remain possible each day with model
guidance suggesting precipitable water values to linger around
1.75 inches or so. Most of the showers and isolated thunderstorm
activity should be focused mainly over the northwest quadrant of
PR but occasional showers may form and stream across parts of the
San Juan metro area during the afternoon hours. The NAAPS Aerosol
model guidance continued to suggest an increase in Saharan dust
once again by the latter part of the work week and continue through
at least Friday or Saturday. This in turn will limit shower activity
across the forecast area.

Drier air with mostly sunny and hazy skies are expected to continue
through the weekend. However, the occasional pockets of trade wind
moisture expected to move across the region will result in a few
passing morning showers across the windward areas of the islands.
This will be followed by locally induced showers with possible
isolated thunderstorms across the interior and western portions of
PR during the afternoons. Except for the local sea breeze variations,
easterly winds are expected to persist through weekend but should
shift and become more southeasterly once again late Monday or Tuesday
of next week, with the approach and passage of the next tropical
wave. By then,a gradual increase in shower and thunderstorm activity
is forecast across the islands and regional waters due to the
additional moisture accompanying the tropical wave.

&&

.AVIATION...VFR conditions will prevail across all TAF sites through
23/16z. VCSH are expected across TIST, TISX and TJSJ throughout this
period. Periods of MVFR conditions with mountain obscurations can be
expected across TJMZ and TJBQ from 23/16Z through 23/22Z.
+SHRA/+TSRA are expected to affect these terminals in the period.
Low level winds will be mainly southeast at 10 to 15 kts.


&&

.MARINE...Seas 3 to 6 feet and winds of 10 to 20 knots can be
expected during the forecast period. Locally higher seas and wind
gusts are possible in and around showers and thunderstorms and
over the near shore waters of the north and south coast of PR.
Small craft operators should therefore exercise caution. Low to
moderate risk of rip currents is expected to prevail during the
next several days.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
520 AM AST Tue Jul 24 2018

.SYNOPSIS....Meandering Tutt low continued north of the region with
associated trough axis extending southwards across Hispaniola and
the Mona passage. Meanwhile a mid to upper level ridge continued
to build and spread across the northeastern Caribbean. Strong surface
high pressure over the north central Atlantic will continue to dominate
the Atlantic basin and maintain moderate east to southeast trade winds
across the forecast area. As a result, occasion surges of trade wind
moisture will move across the region during the period. A weak tropical
wave will cross the northeastern Caribbean on Wednesday and is quickly
followed by a drier Saharan air layer during the rest of the work week.

&&

.SHORT TERM...Today through Thursday...
A surface ridge of high pressure will maintain its foot-hold over
the region with east to southeast winds over the next several days.
SJU-GFS and MIMIC product shows a patch of low level moisture currently
by the U.S. Virgin Islands this moisture is expected to move into
the eastern portions of Puerto Rico during the early morning hours
and will continue to progress west affecting other areas of the
island. The TJSJ 24/00z sounding depicts an inversion at 700 mb
and high clouds across the eastern portions of Puerto Rico. This
will limit shower and thunderstorms development for the eastern
portions of the region, but for portions of the interior and
western Puerto Rico showers and isolated thunderstorms are expected
this afternoon as a result of daytime heating, and local affects.

Wednesday a weak tropical wave moves into the U.S. Virgin Island
during the morning hours and push north of Puerto Rico during the
afternoon. Recent guidance shows a less pronounced wave as a result
of the Saharan dust across the eastern Atlantic, but still expect
showers across the U.S. Virgin Island and eastern Puerto Rico during
the morning hours and showers and isolated thunderstorms across
portions of the western Puerto Rico during the afternoon. Behind the
tropical wave is Saharan dust which will inhibit cloud development
for showers and thunderstorms for the U.S. Virgin Islands and Puerto
Rico on Thursday, but showers that do form will be the result of
locally and diurnally induced afternoon convection.

.LONG TERM...Friday through Wednesday...
Shallow patches of trade wind moisture will move through the area
through Friday and into the weekend supporting locally and diurnally
induced afternoon convection each day. Model guidance continue to
suggest precipitable water values to fluctuate between 1.50-1.70
inches for the next few days. Therefore expect periods of locally
and diurnally induced convection, with the heaviest rainfall
expected during the afternoons and mainly over parts of the
interior and west to northwest sections of Puerto Rico. A few
showers may also form and stream across parts of the San Juan
metro area and on the west end of the U.S. Virgin Islands, with
periods of moderate to heavy downpours possible. Significant
rainfall amounts are however not anticipated for these areas.

The recent NAAPS Aerosol model guidance continued to suggest increasing
Saharan dust particulates across the region once again on Friday and
into the weekend. This in turn will limit shower activity across the
forecast area with drier weather conditions forecast to prevail.
Occasional patches of trade wind moisture are expected to move
across the region and will result in a few passing morning showers
across the windward areas of the islands. This will be followed
by locally induced showers with possible isolated thunderstorms
across the interior and western portions of PR during the afternoons.

Easterly winds will persist through the weekend ,but should shift and
become more southeasterly once again Monday or Tuesday with the passage
of the next tropical wave and accompanying moisture and
instability. By then,an increase in shower and thunderstorm
activity is forecast across the islands and regional waters.
Improving conditions expected by Wednesday of next week.

&&

.AVIATION....VFR conds are expected across all terminal sites through
24/17Z. SHRA will move across terminals TIST, TISX and TJSJ through
the reminder of the morning hours and spread west across termimals TJBQ,
TJMZ. SHRA/VCTS will move across terminals TJBQ and TJMZ by 24/16Z
with gusty winds. Sfc winds will be out of the east to southeast at
15 to 20 kts with higher gust possible.


&&

.MARINE...Small craft advisories not expected next 7 days.
However, winds of 10 to 20 kt will generate choppy seas and
mariners are urged to exercise caution. Isolated thunderstorm
will remain possible over portions of the Atlantic and coastal
waters of W Puerto Rico during the afternoon hours.

&&

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

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
452 AM AST Wed Jul 25 2018

.SYNOPSIS...Tutt low will continue to meander north and west of
the region through the period. Strong surface high pressure across
the north central Atlantic will maintain moderate east to southeast
winds across the forecast area. A weak tropical wave will move across
the region today through Thursday slightly increasing moisture content
and instability. However, a surge in Saharan dust will quickly follow
and this should again limit significant shower activity across the
region. A drier air will move into the area after the passage of the
wave, promoting mostly fair weather and hazy skies through the rest
of the work week and into the weekend.

&&

.SHORT TERM...Today through Friday...
A surface and mid level ridge will hold across the region through
Friday. The surface ridge of high pressure will continue to
promote moderate to fresh east to southeast winds across the area
through Thursday. The MIMIC products shows a dry slot currently
over Puerto Rico this drier air will continue to move to the west
this morning. Right on the hills of the dry slot is moisture from
A TUTT induced wave that will move well to the north of Puerto
Rico today. Recent analysis of cross-section, SJU-GFS model
replaces the drier air with a moist environment by 25/12Z. This
also is depicted by the relative humidity and dew point at
1000-850 mb and 500-700 mb. Showers will develop over the U.S.
Virgin Islands soon and will continue to progress to the west
across Culebra and Puerto Rico later this morning and into the
afternoon. Due to the lack of upper level support thunderstorms
are not expected across the area today, and area wide heavy rain
is not expected either due to the lack of instability and dry mid
to upper levels of the atmosphere. The higher rainfall amounts
will be over the northwest and western Puerto Rico which could see
0.50 inch of rain with higher amounts possible in isolated areas.

Thursday some low level moisture mixed with Saharan dust will move
over the region this combined with the meandering TUTT low north of
Puerto Rico, will aid in the development of scattered showers
across the eastern areas of the region during the morning, then
convection will develop over western portions of Puerto Rico
during the afternoon. Friday the TUTT low continues to meander to
the southwest of the area but remains slightly northwest of Puerto
Rico. Diurnal and locally induced effects will help in the development
of showers and isolated thunderstorms across portions of northwestern
Puerto Rico, and scattered showers across the eastern areas.

.LONG TERM...Saturday through Wednesday...
Shallow patches of trade wind moisture are expected to move through
the area through the weekend supporting locally and diurnally induced
afternoon convection each day. Model guidance continue to suggest
precipitable water values to fluctuate between 1.50-1.75 inches
through Sunday but increasing by Monday and Tuesday with the
approach of the tropical wave. Therefore, expect periods of locally
and diurnally induced convection, with the heaviest rainfall expected
during the afternoons and mainly over parts of the interior and
western sections of Puerto Rico. A few showers may also form and
stream across parts of the San Juan metro area and on the west end
of the U.S. Virgin Islands, with periods of moderate to heavy
downpours possible in isolated spots.

Recent NAAPS Aerosol model guidance continued to suggest increasing
Saharan dust particulates across the region once again over the weekend.
This in turn will limit shower activity across the forecast area.
Easterly winds will persist through the weekend , but should shift
and become more southeasterly and increase again on Monday and Tuesday
with the passage of the aforementioned tropical wave and accompanying
moisture and instability. Improving conditions expected by Wednesday
of next week.

&&

.AVIATION...VFR conditions will prevail across all TAF sites through
25/16z. VCSH are expected across TIST, TISX and TJSJ this morning
will clearing likely by 25/16Z. SHRA/VCSH is expected over terminals
TJBQ and TJMZ by 25/17Z with cleaning expected by 25/22Z. Sfc winds
out of the east to southeast at 15 to 20 kts with higher gusts.


&&

.MARINE...moderate to fresh east-southeast trade winds will continue
with periods of mostly scattered showers over the regional waters.
Seas will remain choppy with seas of 3 to 6 feet in exposed waters.
Small craft advisories are not expected for next several days.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
416 AM AST Thu Jul 26 2018

.SYNOPSIS...Lingering moisture has been replaced by a drier air
mass with Saharan dust this morning. This air will remain over
the region through Friday. Showers are possible due to local and
diurnal effects through Sunday. Saturday low level moisture
embedded in the trade winds will increase the chance for showers
across the U.S. Virgin Islands and portions of eastern Puerto Rico
during the morning, then showers move to the western areas later
in the afternoon. Drier air will filter into the area on Sunday
just ahead of an approaching tropical wave. The wave is
forecasted to reach the area late Sunday and increase rain chances
on Sunday and Monday before moving away on Tuesday.

&&

.SHORT TERM...Today through Saturday... Surface and mid- upper
level ridge will remain the dominant feature across the region
through Saturday. The strong surface ridge centered across the
north central Atlantic will continue to promote moderate to fairly
strong east to southeast trade winds through the short term
period. A Tutt low now north of the region is to sink southwest
across Hispaniola by Saturday. Recent Naaps model guidance and
Satellite derived aerosol products suggest the Saharan air layer
will continue to spread across the region today through Friday
with the highest concentration of suspended dust particulates
expected today then gradually diminishing on Saturday before
increasing once again the latter part of the weekend ahead and
trailing the next tropical wave.

Locally and diurnally induced showers with slight or no chance of
isolated thunderstorms today due to lack of upper air support and the
spreading of the dry air layer and saharan dust across the region.
Similar conditions expected on Friday with mostly fair weather but
hazy conditions and chance of early morning passing showers and
isolated to scattered afternoon showers mainly over portions of
western Puerto Rico. Fewer showers in the form of streamers can be
expected elsewhere including in and around the USVI. On Saturday
guidance suggest a gradual diminishing of the Saharan dust
concentration but still still expect another surge of dust to return
ahead of and trailing the next tropical wave by late Sunday through
early next week.

The prevailing easterly trade winds on Saturday should support and
steer afternoon convection over portion of central and west PR, with
also better chance for isolated thunderstorms on Friday and Saturday
due a slight increase in low level moisture convergence, daytime
heating and forcing. Otherwise mostly fair weather but hazy
conditions for most of the short term period.

&&

.LONG TERM..Sunday through Thursday...The long-term period will
remain tranquil with patches of low level moisture embedded in the
trades will move across the region with locally and diurnally
induced afternoon convection mainly across portions of
northwestern and western Puerto Rico. A surface ridge of high
pressure in the north Atlantic will continue to promote easterly
winds of 10 to 15 mph across the Caribbean and north Atlantic
waters through Thursday. Sunday relative humidity values at 1000
to 850 mb and 700 to 500 mb will range between 70 to 80 percent by
29/18Z; and precipitable water values will range from 1.4 to 1.7
inches. As a result of moisture ahead of an approaching tropical
wave.

Sunday or early Monday a weak tropical wave is forecasted to move
into the caribbean waters south of Puerto Rico. The increase in
moisture will cause showers during the morning across the U.S.
Virgin islands and eastern areas of Puerto Rico, then the showers
will move to the western areas of Puerto during the afternoon.
After the passages of the wave, dry Saharan air will filter in
from the east and remain across the region through Thursday.
Diurnal and locally induced showers are possible during the
afternoon across portions of western Puerto Rico.

A retrograding TUTT/ trough positioned north of Puerto Rico will
be monitored during the long term period. The position of the
TUTT/trough could increase rain chances and cause isolated
thunderstorms, as a result of upper level forcing. This upper
level forcing combined with low level instability provided by the
tropical wave could cause showers and isolated thunderstorms, and
brief heavy rainfall.

&&

.AVIATION...VFR, however expect increasing suspended Saharan dust
particulates across the flying area mstly btw FL050-FL100 but Flight
vis >6sm thru prd. Few low clds -SHRA/SHRA w/mtn obscr ovr E PR til
arnd 26/14Z. SHRA dvlpg ovr W-NW PR 26/17Z-26/22z with brief MVFR
due to low clds and SHRA. Sfc winds E-ESE 5-10 kt bcmg 15-20 kt aft
26/14z. L/lvl wnds E-SE 15-25 kts blo FL150, then backing and
decreasing w/ht abv to nr FL350.


&&

.MARINE...Seas will range from 4 to 6 feet across the regional and
local water ways. Small craft operators are urged to exercise caution as
seas will be up to 6 feet and winds up to 20 knots. Winds will be
out of the east to southeast at 15 to 20 kts. There is moderate to
low rip current risk for all the local beaches.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 79 89 79 / 30 20 20 30
STT 89 80 88 79 / 30 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
414 AM AST Fri Jul 27 2018

.SYNOPSIS...An upper level trough/TUTT will continue to meander to
the north of Puerto Rico over the next several days before
eventually moving over Hispaniola during the weekend. The
proximity of the trough/TUTT conditions across the area will
remain unstable. This is also depicted in the GFS and NAM
comparison where the 200 mb heights is decreasing. The increase in
low level moisture on Sunday combined with the instability could
cause thunderstorms and heavy rainfall. A tropical wave will move
south of Puerto Rico on Monday and clear the area on Tuesday,
behind the wave is dry Saharan air with occasional moisture
embedded in the trades.

&&

.SHORT TERM...Today through Sunday...Drier and stable air mass
will continue to dominate the local weather conditions this
morning. Saharan dust particulate suspended in the atmosphere will
continue to create hazy conditions today. Trade winds will
continue to transport patches of low level moisture, bringing
passing showers across the local waters and windward portions of
the islands. An upper level low north-northwest of the region will
continue to slowly move westward through Saturday, enhancing
instability across the forecast area. This instability will
combine with the local effects to produce showers and
thunderstorms with heavy rains in the afternoon over western
Puerto Rico. Showers from streamers formed from El Yunque, the
eastern islands and USVI can affect the eastern sections of PR and
the San Juan metro area in the afternoon as well. A similar
weather pattern can be expected on Saturday and Sunday. Based on
the NAAPS Aerosol model guidance, Saharan dust content will
decrease during the weekend, which will allow for better rainfall
probabilities, particularly with the afternoon activity. Winds
from the east at 10-15 MPH with higher gusts will prevail during
the next few days. Daytime maximum temperatures will range in the
upper 80s to lower 90s across the coastal areas.

.LONG TERM...Monday through Friday...Dry Saharan air will remain
over the area with patches of moisture periodically moving in
from the east. Showers will develop due to locally and diurnally
induced convection, across northwest and western Puerto Rico
during the afternoon hours. The surface ridge of high pressure in
the northern Atlantic will continue to promote brisk east to
southeast winds over region through Friday. Sunday models
indicate a patch of moisture ahead of a weak tropical wave moving
south of Puerto Rico. This will combine with the local and
diurnal effects and increase rain chances across the U.S. Virgin
Islands during the morning, then move to the western areas of
Puerto Rico during the afternoon. Model guidance shows an area of
weak divergence aloft just to the northwest of Puerto Rico at 18Z
on Monday this combined with low level instability provided by the
tropical wave will help aid in the development of thunderstorms
across northwestern Puerto Rico on Monday. Thunderstorms were
added to the grid for northwestern Puerto Rico. After the passage
of the tropical wave the rest of the week into looks quiet with
Saharan dust and patches of moisture moving in from the east with
typical local and diurnally induced convection in the afternoon.
One caveat with the Monday and Tuesday forecast is the position of
the meandering TUTT low. If the low moves closer to the
northwestern areas of Puerto, this will enhance instability and
create showers and thunderstorms for a wider area, then what is
currently forecasted.

&&

.AVIATION...VFR, however expect increasing suspended Saharan dust
particulates across the flying area mstly btw FL050-FL100 but Flight
vis >6sm thru prd. Few low clds -SHRA/SHRA w/mtn obscr ovr E PR til
arnd 26/14Z. SHRA dvlpg ovr W-NW PR 26/17Z-26/22z with brief MVFR
due to low clds and SHRA. Sfc winds E-ESE 5-10 kt bcmg 15-20 kt aft
26/14z. L/lvl wnds E-SE 15-25 kts blo FL150, then backing and
decreasing w/ht abv to nr FL350.

&&

.MARINE...Seas in the north Atlantic waters will range from 5 to
6 feet, elsewhere seas will range from 3 to 5 feet with easterly
winds of 10 to 15 kts. Small craft operators are urged to use
cautions across the Atlantic waters. Model guidance indicates seas
of 5 to 7 feet across the Caribbean waters starting on Monday and
lasting until Tuesday, if these results come to fruition small
craft advisories will be need for the offshore Caribbean waters.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 78 88 78 / 50 50 30 20
STT 83 80 83 80 / 50 50 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
401 AM AST Sat Jul 28 2018

.SYNOPSIS...Upper low/TUTT will continue to cause unstable
conditions across the local region through Monday. Therfore,
expect showers and isolated thunderstorms with brief heavy rain
across the northwestern and western Puerto Rico during the
afternoon today through Monday. A weak tropical wave will move
over the local islands late Sunday or early Monday, this will
enhance the instability across the local area on Monday. So expect
showers across the eastern portions of the local islands, then
across the western portions of Puerto Rico during the afternoon.
Tuesday the wave moves away from the local area with dry air
filtering in from the east. A seasonal weather pattern is expected
to prevail through the end of next week.

&&

.Short Term...Today through Monday...A surface high pressure over
the north central Atlantic will continue to promote a east to
southeast wind flow across the forecast area. An upper level low
(TUTT) will continue to slowly displace southwestward, positioning
itself over Hispanola through Sunday. This will increase
instability and enhance the shower activity across the local area.
Passing trade wind showers will continue to move over the local
waters and occasionally affect the USVI and some of the eastern
sections of PR in the morning. For this afternoon, the combination
of available moisture, instability from the upper low and the
local and diurnal effects will combine to produce showers and
thunderstorms across the interior and western portions of PR.
Urban and small stream flooding is possible with the heaviest
showers across these areas. Showers are also possible across some
of the northeastern areas of PR including the San Juan metro area.


Patches of low level moisture will continue to bring in isolated to
scattered passing showers Saturday night and Sunday morning,
occasionally affecting the eastern half of PR and USVI. Another
round of showers and thunderstorms can be expected Sunday afternoon
across the interior and western portions of PR, particularly across
the sea breeze convergence area of western PR. A tropical wave is
expected to move across the region on Monday, increasing shower
activity across the local waters and portions of the local islands,
particularly across the western portions of PR in the afternoon
hours. According to the NAAPS Aerosol model guidance, an increase in
Saharan dust can be expected Monday, which could limit some of the
shower activity.

.LONG TERM...Seasonal weather is expected during the long term
period. The weather will be comprised of dry air and occasional
patches of moisture moving in from the east with local and diurnal
induced convection across the northwestern and western Puerto
Rico. Model guidance shows Saharan dust will continue to diminish
during the week until the next plume arrives sometime on Friday.
During the middle of the week the surface ridge will begin to
flatten out which will allow moisture to filter in from the
south. A TUTT in the north Atlantic will retrograde to the west
late Tuesday or early Wednesday, but will stay well north of
Puerto Rico. Daytime high temperatures will be in the middle 80s
to upper 90s with easterly winds of 10 to 15 mph with higher
gusts.

&&

AVIATION...VFR conditions expected during the forecast period.
Passing trade wind showers across the waters will affect eastern PR
and USVI on occasion in the morning. MVFR conditions are possible
over TJMZ and TJBQ from 28/17Z through 28/22Z as shwrs/tstms develop
over western and interior PR. MTN obscuration is possible across the
interior. Easterly winds at around 10-15KT with higher gusts and sea
breeze variations expected.

&&

.MARINE...Moderate to fresh winds will continue through Sunday
across the local region. Seas will range from 3 to 5 feet across
the Caribbean and Atlantic waters. Winds will be out of the east
at 10 to 15 kts with higher gusts possible. Current model guidance
shows sees increasing to 6 to 7 feet over the Caribbean waters
late Sunday or Monday due to a weak tropical wave moving through
the area on Monday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 88 79 / 20 40 40 30
STT 85 80 85 80 / 30 40 40 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
501 AM AST Sun Jul 29 2018

.SYNOPSIS...
A seasonal weather pattern is expected during the next few days
with patches of low level moisture moving across the local area on
occasion, resulting in rounds of showers with isolated thunderstorms
particularly during the afternoon hours across the interior and
western portions of PR. An upper level low pressure with an
associated trough extending southward and into the region, may
increase instability across the forecast area at the end of the
work week and into the weekend. A moisture surge will also move
across the local area during the weekend, which may further
enhance the shower activity.

&&

.SHORT TERM...
The persistent upper-level trough is still meandering over
Hispaniola and will continue to retrograde to the west. A patch of
low-level moisture moved across the region yesterday and caused
showers and thunderstorms over the northwest, and western Puerto
Rico. Infrared satellite imagery shows low-level moisture just to
the east of Puerto Rico; this moisture will continue to progress
to the west and cause isolated to scattered showers across the
eastern and interior of Puerto Rico this morning and afternoon.
The instability created by the trough to the west and diurnal
heating will aid in the development of showers and isolated
thunderstorms over western Puerto Rico today. Monday a weak
tropical wave will increase moisture over the eastern Caribbean
and north Atlantic, before reaching Puerto Rico during the
afternoon. Therefore expected showers and isolated thunderstorms
mainly across the western areas of Puerto Rico during the
afternoon. The rest of the short term period will see patches of
low-level moisture filter in from the east over the U.S. Virgin
Islands and Puerto Rico with scattered showers.

&&

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

A seasonal weather pattern can be expected through Friday with
patches of moisture moving across the region on occasion. Based on
current GFS model guidance, a surface high pressure will continue
to be displaced into western Atlantic by an upper level low
moving into the central Atlantic, slightly decreasing the wind
speeds through Friday. As the low moves deeper into western
Atlantic another upper level low will make its way into central
Atlantic maintaining the upper level high pressure over the north
central Atlantic during the end of the work week. An associated
upper level trough will extend into the area, increasing
instability and shower activity across the forecast area Friday
through Sunday. A surge in low level moisture is also expected
during this period, which will enhance shower and thunderstorm
development over the waters and local islands, particularly on
Sunday. However, this is at the end of the forecast period and
depending on the future conditions, the model guidance could have
a few changes. Daytime high temperatures will generally be in the
mid 80s to lower 90s with easterly winds of 10 to 15 mph with
higher gusts.

&&

.AVIATION...
.AVIATION...VFR conds expected through the forecast period. TSRA
expected across western PR, so VCTS expected at TJBQ and TJMZ.
TEMPO TSRA for TJMZ until 28/21Z. Easterly winds at 15kt with
occasional gusts this afternoon, decreasing after 28/23Z.


&&

.MARINE...Seas will generally range from 3 to 6 feet across the
Caribbean and Atlantic waters and local passages. Small craft
should exercise caution across these areas. Winds will be out of
the east at 10 to 20 kts with higher gusts possible. Low to
moderate rip current risk will prevail during the forecast
period.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 79 84 80 / 50 50 50 50
STT 82 81 82 81 / 20 50 30 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
454 AM AST Mon Jul 30 2018

.SYNOPSIS...
A tropical wave will move across the region today, increasing
shower and thunderstorm activity across the waters and portions of
the local islands. Tonight and Tuesday, drier air with hazy skies
is expected across the local area. Patches of low level moisture
will move across the forecast area on occasion through Friday,
resulting in passing showers during the morning hours mainly over
the local waters and windward portions of the islands, followed
by locally induced showers with possible isolated thunderstorms
over interior and western PR during the afternoon hours. Another
tropical wave is expected to move across the region on Sunday,
increasing shower and thunderstorm activity across the local
waters and portions of the islands. Weather conditions will
improve Monday and Tuesday, as drier air moves into the local
area.

&&

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

Partly cloudy skies prevailed across the local islands overnight
and early this morning with some showers noted across the
surrounding waters as well as the U.S. Virgin Islands and eastern
Puerto Rico. However, rainfall accumulations associated with these
showers were minimal. Coastal temperatures were in the upper 70s
to low 80s under easterly winds at around 10 mph.

An approaching tropical wave and its associated moisture will
result in passing showers across the U.S. Virgin Islands and
eastern Puerto Rico early this morning, spreading over and west of
the Cordillera Central in the afternoon. The available moisture
will then combine with diurnal heating and sea breeze convergence
to result in thunderstorm development across western areas of
Puerto Rico this afternoon. Heavy rain during the afternoon hours
could lead to urban flooding particularly across western Puerto
Rico.

As this wave moves away tonight, a drier weather pattern is then
expected to prevail across the local islands overnight into Tuesday
under ridge pattern aloft and PW values below the normal range.
Therefore, expect limited shower activity with even hazy skies.
Shower activity, if any, will be focused across west Puerto Rico
Tuesday afternoon. The chance for showers with thunderstorms will
increase on Wednesday as moisture is expected to advect from the
northeast.

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

Surface high pressure is expected to remain well into the
northwestern Atlantic Friday through Sunday and move into the
north central Atlantic thereafter. A patch of moisture will move
across the region Friday morning, but is quickly followed by
drier air in the afternoon. Available moisture should be
sufficient to combine with the local effects to produce showers
and possible isolated thunderstorms particularly over interior and
western PR.

GFS model guidance suggests an gradual increase in low level
moisture associated to the trailing edge of a tropical wave moving
into the eastern Caribbean on Saturday. The tropical wave is
expected to move across our local area on Sunday. The GFS also
indicates divergence aloft and good moisture extending into the
mid levels of the atmosphere with the wave, which will enhance
shower and thunderstorm activity across the waters and portions of
the local islands. Thus, showers and thunderstorms were added to
this weekend`s forecast and some of the POPs/QPF values were
increased as well. At the moment, precipitable water values range
around 2.00 inches across most of the forecast area through Sunday
night. However, this is still well into the forecast period and
the model guidance could have a few changes. Weather conditions
are expected to improve on Monday and Tuesday as a drier air mass
moves into the region.

Daytime high temperatures will generally be in the mid 80s to
lower 90s across the coastal regions with heat indices that could
reach up to around 105 degrees across some of the coastal areas.
Easterly winds of 10 to 20 mph with higher gusts can be expected
during the long term period. Based on the NAAPS Aerosol model,
Saharan dust levels are expected to remain low through at least
Saturday.

&&

.AVIATION...Mostly VFR conds are expected to prevail at all TAF
sites. However, as a weak tropical wave moves across the eastern
Caribbean, brief periods of MVFR conds in SHRA are possible across
the Leeward and USVI terminals as well as JSJ through the morning
hours. Aft 30/16z, TSRA likely across west PR and therefore
periods of MVFR conds likely at JBQ/JMZ through 22z. Easterly
winds at 15 to 20 knots with some higher gusts in SHRA/TSRA.

&&

.MARINE...Choppy seas up to 6 feet can be expected across the
Atlantic and Caribbean waters and local passages through at least
midweek. Small craft should exercise caution across these areas.
Elsewhere, seas up to 5 feet can be expected. Winds will prevail
from the east at 10 to 20 knots with higher gusts. Locally higher
seas and winds can be expected in and around strong showers and
thunderstorms. Low to moderate rip current risk can be expected
during the forecast period.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 90 79 / 40 20 20 40
STT 90 79 90 81 / 40 40 20 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
430 AM AST Tue Jul 31 2018

.SYNOPSIS...
A drier and more stable air mass is expected through Friday.
Patches of shallow moisture will bring in isolated to scattered
passing showers over US Virgin Islands, eastern PR and surrounding
waters overnight and early morning hours. Locally induced showers
and isolated thunderstorms can be expected across the interior
and western portions of PR during the afternoon hours each day. A
surge in moisture associated to the trailing edge of a tropical
wave will increase shower and thunderstorm activity across
portions of the forecast area during the weekend. The tropical
wave is now expected to move across the region on Monday, further
increasing convection over the waters and islands, but model
guidance could have a few more changes since it is well into the
end of the forecast period.

&&

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

Partly cloudy skies prevailed across the forecast area overnight
and early this morning with passing showers noted across the U.S.
Virgin Islands and the northeast coastal areas of Puerto Rico.
Temperatures were in the upper 70s to low 80s at lower elevations
under easterly winds at around 10 mph.

A ridge pattern aloft will continue to hold across the local islands
through the forecast period. At lower levels, a broad high pressure
which is located north of the area will continue to yield a moderate
to fresh easterly wind flow. Embedded in the aforementioned flow,
patches of low level moisture will continue to move across the
forecast area at times. Therefore still expect a seasonal weather
pattern with some streamers across the U.S. Virgin Islands and El
Yunque as well as locally induced afternoon showers across west
Puerto Rico each day. Isolated thunderstorms can not be ruled out.
The peak in afternoon convection is expected on Wednesday as a
patch of low level moisture moves across the area. Some haziness
could be also expected today.

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

A patch of moisture is expected to move across the region on
Friday, followed by drier air Friday night. The slight increase in
moisture should be sufficient to combine with the local effects to
produce showers and possible isolated thunderstorms particularly
over interior and western PR.

GFS model guidance continues to suggest an increase in low level
moisture on Saturday associated to the trailing edge of a
tropical wave moving into the eastern Caribbean. One change
noticed with the latest GFS run is that the wave is not expected
until Monday instead of Sunday. An upper level trough will extend
into the forecast area which will increase instability therefore,
showers and isolated thunderstorms still remain in the forecast
for the weekend but not as widespread. There is is still some
divergence aloft and good moisture extending into the mid levels
of the atmosphere at the time the wave passes our area, which will
enhance even further the shower and thunderstorm activity across
the region. GFS Precipitable water values increase to around 2.20
inches across most of the forecast area through Monday night.
POPs/QPF values were then increased for Monday`s forecast to
account for these values. However, model guidance could continue
to have a few changes since it is still well into the long term
forecast period. Weather conditions are expected to improve on
Tuesday as a drier air mass moves into the region.

Daytime high temperatures will generally be in the mid 80s to
lower 90s across the coastal regions with heat indices that could
reach up to around 105 degrees across some of the coastal areas.
Easterly winds of 10 to 20 mph with higher gusts can be expected
during the long term period. The NAAPS Aerosol model suggests an
increase in Saharan dust levels during the upcoming weekend.

&&

.AVIATION...VFR conds are expected to prevail at all TAF sites
with VCSH likely at the Leeward and USVI terminals as well as JSJ
through 31/15z. Aft 31/16z, SHRA/TSRA likely across west PR and
therefore periods of MVFR conds are possible at JMZ through 22z.
Easterly winds at 15 to 20 knots with sea breeze variations some
higher gusts.

&&

.MARINE...
Choppy seas up to 6 feet can be expected across the Atlantic and
Caribbean waters and local passages through Wednesday. Small
craft should exercise caution across these areas. Elsewhere, seas
up to 5 feet can be expected. Winds will prevail from the east at
10 to 20 knots with higher gusts. Low to moderate rip current
risk can be expected through the end of the work week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 88 79 / 20 40 40 40
STT 90 79 89 80 / 20 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
508 AM AST Wed Aug 1 2018

.SYNOPSIS...Locally induced afternoon showers and thunderstorms
across western areas through Thursday. Elsewhere, passing showers.
A tropical wave is expected to move across the region on Friday.
Another and stronger wave is expected on Monday.

&&

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

A patch of moisture will continue to move across the region today
increasing shower activity over the local area. Isolated to
scattered showers are expected to occasionally affect the US
Virgin Islands, as well as eastern and northern sections of PR
during the morning hours. The low level moisture will then combine
with local and diurnal effect to induce showers and isolated
thunderstorms over the interior and western portions of PR in the
afternoon. A few showers cannot be ruled out across San Juan and
Vicinity. Drier air will then move into the area by Wednesday
night and continuing on Thursday, improving weather conditions.

The latest GFS model guidance indicates a tropical wave passing
through the region Thursday night and Friday, increasing moisture
and instability. Shower and thunderstorm activity will generally
be focused across the Caribbean waters, US Virgin Islands as well
as eastern and northern portions of PR in the morning as the wave
moves in and then spreads into the interior and western sections
of PR in the afternoon. GFS Precipitable water values with this
wave are around 1.6 to 2.0 inches through Friday night. Urban and
small stream flooding is possible across portions of PR, particularly
across low lying and poor drainage areas.

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

A trough pattern aloft will prevail across the eastern Caribbean
Saturday through at least Monday. This will result in deeper
instability across the local islands particularly Sunday and
Monday. As this feature shifts westward, a ridge pattern aloft is
then expected to build from the east and hold through the end of
the forecast period. At lower levels, tropical wave passage is
expected on Monday.

If long term forecast holds, expect showers across eastern Puerto
Rico and the U.S. Virgin Islands Saturday and Sunday with afternoon
showers and isolated thunderstorms also developing over and west
of the Cordillera Central both days. The chance for shower and
thunderstorm activity may increase on Monday as a tropical wave
interacts with the aforementioned trough aloft. Therefore, organized
convection is possible. As the wave moves away and trough aloft
shifts westward, a drier and stable air mass is then expected to
prevail Tuesday through Thursday. However, a few locally induced
afternoon showers cannot be ruled out across west Puerto Rico each
day. Seasonable temperatures to continue under a moderate to
locally fresh easterly wind flow.

&&

.AVIATION...Mostly VFR conds expected during the forecast period
across TAF sites. VCSH at TJSJ/TJBQ/TIST/TISX early in the
morning. VCSH/SHRA and possible MVFR condtions for TJMZ/TJBQ from
18Z- 22Z. MTN obscuration possible across western interior PR.
Winds will remain mainly from the east at 10- 15KT with higher
gusts and sea breeze variations.

&&

.MARINE...Seas below 6 feet and winds between 15 to 20 knots to
continue. Therefore, small boat operators should exercise caution.
Seas and winds slightly increasing early next week with the tropical
wave passage. Small craft advisories cannot be ruled out then,
but are not expected.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 88 79 / 40 40 40 40
STT 91 80 89 80 / 40 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
349 AM AST Thu Aug 2 2018

.SYNOPSIS...High pressure will prevail today but this will slowly
fade as a low pressure moves into de central Atlantic. Weak
tropical waves are still expected on Thursday night and Monday
with the latter being the strongest and the wettest of the two.
Saharan dust will return on Saturday and persist well into next
week.


&&

.SHORT TERM...Today through Saturday...
A drier air mass will be moving over the area for today.
Therefore, mainly fair weather conditions are expected across most
of the region with the only exception across western PR, where
intense heating and sea breeze convergence will aid in the
development showers and isolated thunderstorms this afternoon,
mainly across Mayaguez and vicinity. Given the heavy rainfall over
the area Wednesday afternoon, the terrain is saturated, therefore
additional heavy rainfall can create urban and small stream
flooding in localized areas.

Later during the overnight into Friday, moisture associated with a
weak tropical wave will spread over the area with precipitable water
values increasing to between 1.7 to 1.9 across the region.
Therefore, an increase in the areal coverage in the shower activity
is expected. Passing showers are expected to affect portions of
eastern PR and the USVI during the overnight and morning hours
followed by afternoon shower and thunderstorm activity across
interior and western PR. Additional shower activity is also possible
across eastern PR.

On Saturday, an extensive area of Saharan dust will begin to
overspread the region, therefore, hazier skies are expected.
Sufficient low-level moisture will remain in place to result in some
passing shower activity across eastern portions of PR and the USVI
during the morning hours followed by afternoon convection across
western PR due to local and diurnal effects.

.LONG TERM...Tuesday through Saturday...
Moisture associated to a trough will begin to increase across the
local forecast area between late Saturday night and early Sunday
morning. Therefore expect morning showers along the eastern
portions of Puerto Rico and USVI and afternoon showers and
thunderstorms along the interior and western portions of Puerto
Rico on Sunday. After Tuesday a drier and more stable air will
prevail over the local region through most of the week.

&&

.AVIATION....AVIATION...Mainly VFR conditions expected across all terminals
throughout the period. SHRA with isolated TS expected across TJMZ
terminal from 02/17Z to 02/22Z, creating MVFR conditions at times.
VCSH possible across TJBQ terminal. Winds will be from the east at
10-20KT with higher gusts and sea breeze variations after 02/14z.


&&

.MARINE...Winds 10-20 kts and seas 5 feet or less. Small craft
operators should continue to exercise caution due to light chop.


&&

.FIRE WEATHER...A drier air mass is expected over across the local
forecast area today. The latest forecast guidance suggest an
elevated risk for fire weather for today across the South Coastal
Plains of Puerto Rico. A Fire Weather Discussion (RFDSJU) has been
issued for the South Coastal Plains of Puerto Rico. There is a
low risk of fire weather elsewhere in Puerto Rico and the U.S.
Virgin Islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 77 88 79 / 10 30 30 40
STT 90 78 90 80 / 30 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
348 AM AST Fri Aug 3 2018

.SYNOPSIS...Lingering moisture from a weak tropical wave will
increased showers today across the local forecast area. A second
stronger tropical wave will move through the area on Monday
enhanced by an upper level trough. A new episode of Saharan dust
will arrive on Saturday and intensify over the weekend. The dust
will last at least through mid week.


&&

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

Moisture associated with the passage of a weak tropical wave to
south of the region will increase across the area for today with
precipitable water values around 1.7 inches. However, due to the
lack of upper-level dynamics, widespread rainfall activity is not
expected with most of the rainfall activity being limited across
western PR due to local and diurnal effects. Given the recent heavy
rainfall during the past couple of days across western PR, the
terrain is saturated, therefore, the potential will exist for urban
flooding as well as rapid rises along rivers and streams in areas
that do receive heavy rainfall activity. Mudslides in areas of steep
terrain are also possible. Isolated showers in the form of streamers
will be possible downwind from the USVI, affecting Culebra and
eastern PR.

On Saturday, an extensive area of Saharan dust will begin to work
its way across the region. Therefore, hazier skies are expected.
This Saharan dust plume, however, will be not strong enough to
inhibit convection with locally and diurnally induced convection
expected across western and northwestern PR during afternoon.
Additional showers in the form of streamers may develop downwind
from the USVI as well as downwind from El Yunque, affecting southern
portions of the San Juan Metro area.

A more active day is expected for Sunday as a mid to upper-level
trough will be positioned in a favorable location north of the
region to result in the development of more widespread shower
activity. Latest forecast soundings show very unstable conditions
developing with lifted index values around -10 along with very cold
500 mb temperatures between -9 and -10 degrees Celsius. Therefore,
the potential will exist for the development of strong
thunderstorms, especially across the western half of PR, where the
activity will be enhanced by sea breeze convergence and
topographical effects.

.LONG TERM...A tropical wave is forecast to move across the local
region on Monday with upper level dynamics favorable for the
development of widespread showers and thunderstorms across the
local forecast area. Although conditions are expected to be
slightly more stable from Tuesday through Friday, there will be
enough available moisture to generate showers and thunderstorms
mainly over the interior and western portions of Puerto Rico each
afternoon.


&&

.AVIATION...Mainly VFR conditions expected across all terminals
through 03/16z. SHRA and isolated TS expected to develop across
western PR after 03/16z, with TJBQ and TJMZ observing VCTS from
03/18z to 03/22z. This could create MVFR conditions at times,
especially across the vicinity of TJBQ, where the heaviest activity
is expected. Winds will be from the east between 10 and 20KTS with
higher gusts and sea breeze variations after 03/14z.


&&

.MARINE... Winds will continue at 15 to 20 kts and seas mainly of
5 feet or less but occasionally up to 6 feet overnight through
Friday. Small craft operators should therefore continue to
exercise caution.


&&

.FIRE WEATHER...The latest observations and forecast guidance
suggest that there is an elevated risk for fire weather today
across the South Coastal Plains of Puerto Rico. A Fire Weather
Discussion (RFDSJU) has been issued for the South Coastal Plains
of Puerto Rico. There is a low risk of fire weather elsewhere in
Puerto Rico and the U.S. Virgin Islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 79 89 79 / 20 40 40 30
STT 91 80 90 80 / 30 40 40 30