Caribbean - Central America Weather

[cycloneye]

8 PM TWO: 10%-40%

A large and complex area of disturbed weather to the south and
southwest of the Cabo Verde Islands is associated with a broad
trough of low pressure and a tropical wave. These systems are
forecast to merge over the next day or two, and environmental
conditions are then expected to be conducive for development of
this disturbance later this week while it moves westward at about
15 mph over the tropical Atlantic.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...medium...40 percent.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
517 AM AST Mon Aug 14 2017

.SYNOPSIS...Available moisture will gradually increase today just
ahead of a tropical wave that will reach the local islands late
tonight into Tuesday morning. Saharan dust will follow the
tropical wave on Tuesday.

&&

.SHORT TERM...Today through Wednesday...
A tropical wave just east of the Lesser Antilles is forecast to
move across the region later today. Trade wind showers will
continue to move from time to time across the regional waters and
over portions of the islands through the morning hours. Scattered
to locally numerous showers and isolated thunderstorms are
expected this afternoon mainly over the interior and western
portions of Puerto Rico. Then in the evening hours, scattered to
numerous showers with isolated thunderstorms cant be ruled out
across the regional waters and over portions of the USVI and the
eastern half of PR as the wave moves across the local area.

By Tuesday morning, as the wave exits the local area, a drier air
mass with Saharan dust is forecast to move over the area from the
east. This will result in hazy skies and limited shower activity
across the islands. Similar conditions should prevail through
Wednesday morning. However, as the Saharan air layer diminishes,
diurnally induced afternoon showers and isolated thunderstorms are
expected mainly over the southwest quadrant of PR under a northeast
steering wind flow.

.LONG TERM...Thursday through Tuesday...
The long term forecast is highly uncertain at this time and the
long range models varied substantially between the 13/18Z and the
14/00Z model runs, especially the GFS model, the ECMWF did not
change much. There is a broad trough of low pressure and a
tropical wave that are currently in the eastern Atlantic close to
each other which could potentially approach the local area late
this week or weekend. The impact in the local area will depend on
the development, if any. The 14/00Z model run of both the ECMWF
and the GFS models have a tropical wave bringing deep moisture and
shower activity for Thursday and Friday but they differ on the
feature that could approach the local area on Saturday or Sunday.
Having said that, the models do not differ as much now as they
did with the GFS 13/18Z run. The National Hurricane Center is
monitoring the possible Tropical Cyclone development coming out of
what they are calling "A large an complex area of disturbed
weather". At this time, the latest forecast is for moisture and
shower activity to increase on Thursday and Friday, after that
there is simply too much uncertainty to go into too much detail as
the forecast for the weekend will likely change significantly
over the next few days.

&&

.AVIATION...Mainly VFR conditions are expected to prevail early in
the forecast period. Trade wind showers ahead of a tropical wave,
now just east of the Leeward islands, can result in RA/SHRA at times
across TNCM/TKPK/TIST/TISX. SHRA/TSRA expected between 16z-22z
across western PR, impacting mainly TJMZ/TJBQ. Tempo MVFR possible
after 22z across the Leeward/USVI terminals. East winds should
prevail around 15 kt with higher gusts and sea breeze variations
after 14z.


&&

.MARINE...Small craft operators should exercise caution as winds
will be up to 20 knots. Seas will be generally 3 to 5 feet today,
increasing briefly up to 6 feet on Tuesday. There is a moderate
risk of rip currents today across many of the beaches of Puerto
Rico, including Vieques and Culebra, as well as most of Saint
Croix, however, Saint John and Saint Thomas both have a low risk
of rip currents.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 91 80 92 80 / 40 50 10 30
STT 90 81 91 81 / 50 60 20 30

[cycloneye]

Shower and thunderstorm activity associated with a broad trough of
low pressure southwest of the Cabo Verde Islands has increased
since last night. Environmental conditions are expected to be
generally conducive for development of this disturbance for the next
several days while it moves westward at about 15 mph over the
tropical Atlantic.
* Formation chance through 48 hours...low...20 percent.
* Formation chance through 5 days...medium...60 percent.

[cycloneye]

Showers and thunderstorms associated with an elongated area of low
pressure located several hundred miles west-southwest of the Cabo
Verde Islands have changed little in organization since this
morning. Environmental conditions are expected to be generally
conducive for development during the next several days while the
disturbance moves westward at about 15 mph over the tropical
Atlantic.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...medium...60 percent.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
423 PM AST Mon Aug 14 2017

.SYNOPSIS...
A TUTT low over the Atlantic Ocean will displace a Sub-equatorial
Ridge by Tuesday. Moisture ahead of the tropical wave is moving
across the islands today. The tropical wave axis is expected to
reach the U.S. Virgin Islands tonight. Saharan dust will follow
the tropical wave on Tuesday into Wednesday. Another tropical wave
is expected to reach the islands by Wednesday into Thursday.

&&

.SHORT TERM...
Leading moisture associated with the tropical wave near the
Leaser Islands increased showers across the U.S. Virgin Islands
this afternoon. Some of these showers reached the eastern sections
of Puerto Rico including Vieques and Culebra. In addition, the
available moisture combined with the local effects and diurnal
heating aid in the development of showers and thunderstorms across
the interior and western sections of Puerto Rico.

The tropical wave axis, which is now near the Leeward Islands,
should arrive near the U.S. Virgin Islands this evening and in
Puerto Rico later tonight. Therefore, showers and thunderstorms
are expected to affect the U.S. Virgin Islands, east half section
of Puerto Rico and the local waters. This tropical wave will be
followed by a dry air mass with suspended particles which is
forecast to move Tuesday and Wednesday. Then, another tropical
wave is forecast to interact with a TUTT low Wednesday and
Thursday, increasing once again the potential for showers and
thunderstorms across the islands.

.LONG TERM...Thursday through Tuesday...
The long term forecast is highly uncertain at this time and the
long range models varied substantially between the 13/18Z and the
14/00Z model runs, especially the GFS model, the ECMWF did not
change much. There is a broad trough of low pressure and a
tropical wave that are currently in the eastern Atlantic close to
each other which could potentially approach the local area late
this week or weekend. The impact in the local area will depend on
the development, if any. The 14/00Z model run of both the ECMWF
and the GFS models have a tropical wave bringing deep moisture and
shower activity for Thursday and Friday but they differ on the
feature that could approach the local area on Saturday or Sunday.
Having said that, the models do not differ as much now as they
did with the GFS 13/18Z run. The National Hurricane Center is
monitoring the possible Tropical Cyclone development coming out of
what they are calling "A large an complex area of disturbed
weather". At this time, the latest forecast is for moisture and
shower activity to increase on Thursday and Friday, after that
there is simply too much uncertainty to go into too much detail as
the forecast for the weekend will likely change significantly
over the next few days.

&&

.AVIATION...
Trade wind SHRA/isold TSRA are causing some MVFR CIGS at
TNCM/TKPK. These will advance thru USVI aft 14/22Z and thru ern PR
aft 15/04Z with mtn obscurations SHRA/isold TSRA and MVFR conds.
Afternoon convection has begun across Rincon in wrn/interior PR with
same conditions until 14/22Z with lingering SHRA byd. Sfc winds E-
ESE 10-20 kt diminish to 5 to 10 kt with land breezes by 15/01Z.
Winds alf ENE-ESE up thru FL240. 10-20 kt bcmg up to 30 kt at
FL100.

&&

.MARINE...
Small craft operators should exercise caution as winds and seas
are forecast to increase at 15 to 20 knots and 4 to 6 feet,
respectively. A tropical wave will bring showers and thunderstorms
across the regional waters tonight into early Tuesday morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 80 92 80 89 / 50 10 30 30
STT 81 91 81 91 / 60 20 30 30

[cycloneye]

An elongated area of low pressure located several hundred miles
west-southwest of the Cabo Verde Islands is producing a large area
of cloudiness and showers. Environmental conditions are expected
to be generally conducive for development during the next several
days while the disturbance moves westward at about 15 mph over the
tropical Atlantic.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...medium...60 percent.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
521 AM AST Tue Aug 15 2017

.SYNOPSIS...A tropical wave will exit the area during the morning
hours. Hazy skies due to Saharan dust are expected later this
morning and should continue through early Wednesday. Another
tropical wave is forecast to move across the islands on Thursday
and increase shower and thunderstorm activity.


&&

.SHORT TERM...Tuesday through Thursday...A weak mid level ridge
will prevail through Thursday with some strengthening expected by
the end of the workweek. At upper levels, as a TUTT low shifts
westward on Wednesday, an upper level ridge will then build across
the forecast area. A broad surface high pressure across the
central Atlantic will continue to yield moderate to fresh easterly
winds. A tropical wave will continue to move away throughout the
day, with the next tropical wave passage expected on Thursday.

Showers with isolated thunderstorms which are associated with a
tropical wave moving across the eastern Caribbean are still possible
across the local waters as well as portions of USVI and E PR early
this morning. Although the tropical wave and associated low level
moisture is expected to move away by the afternoon hours, lingering
moisture will continue to prevail to result in locally induced
showers and thunderstorms across west Puerto Rico in the afternoon.
Fair weather is then expected tonight through at least early
Thursday when the next tropical wave is expected to move across the
local isles. As the drier air mass moves in this afternoon, hazy
skies are likely.

.LONG TERM...Friday through Wednesday...In the long range there
are a couple of areas of interest...there is an area of low
pressure, located several hundred miles west-southwest of the
Cabo Verde Islands that is forecast to move across the Caribbean
Sea between Friday and Saturday. The National Hurricane Center is
currently giving a 60% chance of formation during the next 5 days.
Then, two tropical waves are expected to follow between
Sunday/Monday and the other one on Wednesday. However, this is too
far in the future to know exactly the potential impacts and
possible tropical development of these systems.


&&

.AVIATION....Mostly VFR conds expected at all TAF sites with some
-RA/VCSH at JSJ as well as USVI terminals early this morning. As
a tropical wave moves away throughout the day, VFR conds to
continue with hazy skies likely. However, visibilities expected to
remain P6SM. Easterly winds 15-20 knots aft 15/13z.


&&

.MARINE...Seas should range between 4-6 feet across most of the
local waters and east winds at 15-20 knots should prevail today.
Therefore, small crafts should exercise caution across the local
waters and passages. Small craft advisories could be required by
late Wednesday night as seas up to 7 feet are possible across the
offshore waters and the Anegada Passage. There is a moderate risk
of rip currents for much of the coastal areas of the
islands...except in the protected west facing beaches.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 79 88 78 / 20 20 20 30
STT 91 80 91 80 / 20 20 20 50

[cycloneye]

Shower and thunderstorm activity associated with an elongated area
of low pressure located more than a thousand miles east of the
Lesser Antilles remains disorganized. This system is expected to
move westward at 15 to 20 mph across the tropical Atlantic Ocean,
crossing into the Caribbean Sea on Friday. Some slow development
of this system is possible before it moves into the Caribbean Sea,
where environmental conditions are expected to be less conducive
for tropical cyclone formation.
* Formation chance through 48 hours...low...20 percent.
* Formation chance through 5 days...medium...40 percent.

[cycloneye]

.SYNOPSIS...
A TUTT low moving westward over the region. A relative dry air
mass with Saharan dust particles is filtering across the islands.
Another tropical wave is expected to reach the local waters by
Wednesday afternoon into Thursday.

&&

.SHORT TERM...
Fair weather conditions with hazy skies are expected to prevail
across most of the islands as a dry air mass with Saharan dust
particles filter in. However, showers with isolated thunderstorms
across the interior and west sections can not be ruled out this
afternoon. In additions, streamers of clouds downwind from the
U.S. Virgin Islands, Vieques and Culebra could result in showers
across the east sections of Puerto Rico. But, in general warm
temperatures and hazy skies are expected to prevail the rest of
this afternoon and during the overnight hours.

The leading moisture of a tropical wave is expected to reach the
islands by Wednesday afternoon move across the islands by
Wednesday afternoon into Thursday interacting with the TUTT low.
Under this weather pattern showers and thunderstorms are expected
to increase in coverage and intensity across the islands during
this period.

.LONG TERM...Friday through Wednesday...
In the long range there are a couple of areas of interest, there
is an area of low pressure, Invest 91L, located several thousand
miles east of the Lesser Antilles that is forecast to move across
the Caribbean Sea between Friday and Saturday. Another area of low
pressure have become a little better organize and is now invest
92L. The National Hurricane Center is currently giving a 40%
chance of formation during the next 5 days to both systems. Then,
invest 92L is forecast to move near the local Atlantic Ocean
between Sunday/Monday. Then another tropical wave is forecast to
reach the region on Wednesday. However, this is too far in the
future to know exactly the potential impacts and possible tropical
development of these systems.

&&

AVIATION...VFR conds expected across the local terminals. Saharan
dust is expected to continue today but visibility should remain
P6SM. Winds mainly from the east at about 15KT with occasional gusts
and some sea breeze variations until 15/22Z. SHRA/TSRA possible near
TJMZ after 15/18Z so VCTS was put in TAF. Winds will remain from the
east at 10kt or higher across most of the local terminals during the
overnight hours with little to no rainfall expected.

&&

MARINE...Small craft should exercise caution across the local
waters due to seas up to 6 feet and winds up to 20 knots. Marine
guidance continues to suggests increasing seas and winds across
the regional waters. As a result, small craft advisories will be
required by Wednesday afternoon as seas up to 7 feet are expected
across the offshore waters and the Anegada Passage.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 79 88 78 88 / 20 20 30 30
STT 80 91 80 89 / 20 20 50 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
542 AM AST Wed Aug 16 2017

.SYNOPSIS...A tropical wave just east of the Lesser Antilles will
move across the forecast area later tonight through Thursday.
Tutt low will continue just to the west-northwest of the forecast
area through Friday as an upper ridge builds from the north.
Saharan air layer will gradually diminish today ahead of the
tropical wave.


&&

.SHORT TERM...Today through Friday...A mid to upper level ridge
is expected to build across the forecast area Thursday night, as a
trough aloft/TUTT low which is now located across the northeast
Caribbean shifts westward. However, the ridge pattern aloft is
expected to be short-lived as trofiness returns to the local isles
on Sunday. At lower levels, a broad high pressure across the
central Atlantic will continue to yield moderate to fresh easterly
winds through the forecast period. The next tropical wave passage
is expected as soon as late tonight into Thursday.

Under this evolving pattern, expect fair weather conditions through
the morning hours followed by locally induced showers and
thunderstorms across southwest Puerto Rico in the afternoon. The
chance for showers and thunderstorms -squally weather type- will
increase across the forecast area late tonight into Thursday due to
the proximity of TUTT low and a tropical wave moving across the
eastern Caribbean.

At this time, the most active convection and the best chance for
heavy rainfall is across US Virgin Islands and eastern Puerto Rico
Thursday morning. Urban and small stream flooding likely. Shower and
thunder development across west Puerto Rico Thursday afternoon will
be dependent on cloud cover. As the tropical wave moves away and an
upper level ridge builds, a fair weather pattern is then expected to
prevail on Friday.

.LONG TERM...Saturday through Wednesday...In the medium range, an
area of low pressure near 46W longitude, which the National
Hurricane Center is giving a 40% chance of formation during the next
5 days...is forecast to move across the Caribbean Sea between Friday
and Saturday...and remain south of the islands. Another area of low
pressure near 34W longitude, that NHC is also giving a 40% chance of
formation during the next 5 days, is currently expected to move
close to the forecast area as an open trough late in the weekend. In
the long range, both GFS and ECMWF 16/00z runs indicated a surface
low pressure area passing well to the northeast of the forecast area
by midweek.


&&

.AVIATION...VFR conds are expected at all TAF sites in the morning
with brief MVFR conds possible at JMZ/JPS in SHRA/TSRA btw 16/16-
22z. As a tropical wave moves across the eastern Caribbean,
SHRA/TSRA and MVFR conds are expected in and around the Leeward
terminals late this afternoon, spreading across the USVI terminal
and JSJ late tonight. Easterly winds 15-20 knots aft 16/13z.


&&

.MARINE...Seas are expected to increase later today ahead of the
tropical wave between 6-8 feet across the Anegada Passage and across
both Atlantic and Caribbean offshore waters through at least
Thursday. Small craft advisories are in effect. East to northeast
winds between 15 to 20 knots will prevail today. Squally weather is
possible early on Thursday as the wave exits the local area. A
moderate to high risk of rip currents is expected for the next few
days across PR, Culebra, Vieques and St. Croix.

[cycloneye]

A low pressure system located about 900 miles east of the Lesser
Antilles continues to produce disorganized showers and a few
thunderstorms. This system is moving westward at 15 to 20 mph,
and it is expected to cross into the Caribbean Sea on Friday.
Upper-level winds are forecast to become a little more conducive
for development during the next several days, and interests in the
Lesser Antilles should monitor the progress of this system.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...medium...40 percent.

[cycloneye]

A low pressure system located about 800 miles east of the Lesser
Antilles has become a little better defined since yesterday, but
most of the associated shower and thunderstorm activity is
displaced to the west of the center of circulation. Upper-level
winds are forecast to become more conducive for development during
the next day or so while the low moves westward at 15 to 20 mph
across the tropical Atlantic Ocean, crossing into the Caribbean Sea
on Friday. An Air Force Reserve reconnaissance aircraft is
scheduled to investigate this system on Thursday, if necessary, and
interests in the Lesser Antilles should monitor the progress of the
disturbance.
* Formation chance through 48 hours...medium...40 percent.
* Formation chance through 5 days...medium...50 percent.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
438 PM AST Wed Aug 16 2017

.SYNOPSIS...A tropical wave just across the eastern Caribbean
will move across the forecast area tonight through Thursday. TUTT
low will continue just to the west- northwest of the forecast area
through Friday as an upper ridge builds from the north. Saharan
air layer will gradually diminish tonight ahead of the tropical
wave.

&&

.SHORT TERM...Tonight through Friday...
A mid to upper level ridge is expected to build across the
forecast area Thursday night, as a trough aloft/TUTT across the
northeast Caribbean shifts westward. At lower levels, a broad
high pressure across the central Atlantic will continue to produce
a moderate to fresh easterly winds through the forecast period.
An active tropical wave across the Lesser Antilles this afternoon
will continue to move westward moving across the local islands
tonight and Thursday. The moisture associated with the leading
edge of the wave in combination with daytime heating and local
effects will continue to induce the development of shower and
thunderstorm activity across the U.S. Virgin Islands, Vieques,
Culebra, Puerto Rico and the surrounding waters for the rest of
this afternoon and evening. The chance for showers and thunderstorms
will increase across the forecast area tonight into Thursday due
to the proximity of TUTT low and the tropical wave moving across
the local islands.

Urban and small stream flooding likely. Shower and thunder
development across west Puerto Rico Thursday afternoon will be
dependent on cloud cover. As the tropical wave moves away and an
upper level ridge builds, a fair weather pattern is then expected
to prevail on Friday.

.LONG TERM...Saturday through Wednesday...PREVIOUS DISCUSSION...
In the medium range, an area of low pressure near 48W longitude,
which the National Hurricane Center is giving a 40% chance of
formation during the next 5 days...is forecast to move across the
Caribbean Sea between Friday and Saturday...and remain south of
the islands. Another area of low pressure near 35W longitude,
that NHC is also giving a 40% chance of formation during the next
5 days, is currently expected to move close to the forecast area
late in the weekend. In the long range, latest runs of both GFS
and ECMWF runs indicated a surface low pressure area passing well
to the northeast of the forecast area by midweek.

&&

.AVIATION...Approaching tropical wave is bringing SHRA/TSRA to the
local area. Intermittent brief moment of SHRA/TSRA over the local
terminals is expected, some of which could cause at least MVFR conds
for brief moments at a time. Mainly VCSH/VCTS written on TAF due to
uncertainty on timing, AMD with TEMPO as necessary. Winds will
remain at about 15-20KT with occasional gusts. CIGS will be at about
FL040 but lower in SHRA/TSRA. Wx conditions across the local
terminals to be unsettled through Thursday night.

&&

.MARINE...Seas are expected to increase tonight between 6-8 feet
across the Anegada Passage and across both Atlantic and Caribbean
offshore waters through at least Thursday. Small craft advisories
are in effect. East to northeast winds between 15 to 20 knots will
prevail tonight. Squally weather is possible tonight and Thursday
as the wave moves across the local area. A high risk of rip
currents is in effect for northwest and north central beaches of
Puerto Rico and for St. Croix.

&&


.PRELIMINARY POINT TEMPS/POPS...
SJU 79 88 80 87 / 60 60 20 20
STT 80 89 80 92 / 60 60 30 20

[cycloneye]

8 PM TWO up to 50%-60%

Showers and thunderstorms associated with a low pressure system
located about 650 miles east of the Lesser Antilles have become
a little more concentrated this afternoon. Upper-level winds are
forecast to become more conducive for development during the next
day or so while the low moves westward at 15 to 20 mph across the
tropical Atlantic Ocean, crossing into the Caribbean Sea on Friday.
Regardless of development, locally heavy rainfall and gusty winds
are expected to spread across portions of the Lesser Antilles on
Thursday night and Friday, and interests there and elsewhere in
the eastern Caribbean should monitor the progress of this
disturbance. An Air Force Reserve reconnaissance aircraft is
scheduled to investigate this system on Thursday, if necessary.
* Formation chance through 48 hours...medium...50 percent.
* Formation chance through 5 days...medium...60 percent.

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
342 PM AST Thu Aug 17 2017

.SYNOPSIS...A very active tropical wave now moving across the forecast
area will continue to produce showers and thunderstorms across parts
of the islands and local waters during the rest of today and overnight.
A TUTT low will shift farther west of the forecast area overnight,as
an upper ridge will gradually build from the north through Saturday.
An area of low pressure east of the Lesser Antilles is expected to move
across the eastern Caribbean late Friday through Saturday. This will
increase the potential for squally conditions and thunderstorms mainly
across the Caribbean waters. The National Hurricane Center is issuing
advisories on this Potential Tropical Cyclone Nine and an Air Force
Reserve Hurricane Hunter aircraft is currently enroute to investigate
the disturbance.

&&

.SHORT TERM...Overnight through Saturday...The combination of the
tropical wave passing through the local area and the proximity of
the upper trough west of the region will maintain unstable weather
conditions over the forecast area overnight through early Friday.
Showers and thunderstorms over the islands should diminish by early
evening, but is expected to again redevelop across the coastal waters
and reach portions of PR and the USVI by early morning. Somewhat drier
conditions is expected by Friday afternoon as the Tropical wave will
have exited the region, and the upper level ridge gradually builds
over the area along with an intrusion of suspended Saharan dust
expected to move across the region. On Saturday The chance for showers
and thunderstorms will again increase as invest 91L/potential Tropical
cyclone nine moves south of the area and peripheral moisture is expected
to propagate northward and affect the forecast area.

.LONG TERM...Sunday through Friday...The area of low pressure Invest
92L, currently has a 60 percent chance of formation through the next
5 days. Based on recent info from the National Hurricane center, this
system is expected to encounter unfavorable upper level winds for further
development and should move northeast of the islands on Sunday as a
tropical wave. However, recent model guidance continued to suggest
that the overall layered precipitable water/moisture content will
remain high through the early part of next week. This should support
showers and isolated thunderstorm development each day across the
islands. Another tropical wave and Tutt low is forecast to approach
the local area by Tuesday. This should bring increased instability
and favorable conditions for enhanced convective development through
at least Wednesday. So far, a gradual improvement in the overall weather
pattern is expected across the region by Thursday and Friday.

&&

.AVIATION...BKN-OVC skies expected through the afternoon across the
terminals in PR while the USVI and TNCM/TKPK observes mainly FEW_SCT
clouds. CIGS across terminals in PR will be at Fl080 to about FL110.
Wx improving this afternoon and tonight. Winds will remain mainly
easterly at 10-15KT with occasional higher gusts for the rest of
today, decreasing winds tonight. Mainly VFR conds expected starting
this afternoon into Friday, winds increasing after 18/13Z at about
15KT from the east.

&&

.MARINE...Showers and isolated thunderstorms will affect parts of
the regional waters during the rest of the overnight hours, as the
tropical wave will continue to exit the region. Small craft advisories
will continue in effect across much of the local waters, due to winds
of up to 20 knots and seas up to 8 feet.

Moderate to high risk of rip currents across the local islands
today.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 76 88 78 88 / 30 20 60 40
STT 75 92 80 89 / 20 20 50 50

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
520 AM AST Fri Aug 18 2017

.SYNOPSIS...Tropical Storm Harvey is forecast to move westward
across the Caribbean Sea and pass south of the forecast area late
tonight into Saturday. A generally fair weather pattern is expected
to prevail today with the chance for showers and thunderstorms
increasing across the local isles during the weekend as the peripheral
moisture of TS Harvey reaches the forecast area as well as invest
92L likely to move northeast of the area on Sunday.

&&

.SHORT TERM...Friday through Sunday...

The available moisture is forecast to erode today, as a mid to
upper level ridge builds from the northeast, strengthening the
cap inversion over the region through early Saturday. In addition,
model guidance is indicating the arrival of more Saharan dust
particles today. Under the aforementioned weather pattern, little
or no shower activity is expected across the region today. Maximum
temperatures are expected in the low 90s along the coastal areas
and in the mid 80s across the interior sections.

The center of Tropical Storm Harvey is forecast to move well south
of the islands and across the Caribbean waters late tonight into
Saturday. Although no direct impact of Harvey is expected across
the County Warning Area, the available moisture is expected to
increase by early Saturday morning. As a result, shower and
thunderstorm activity is expected to increase in frequency and
intensity through Saturday. Soils are already saturated,
especially across east and southeast Puerto Rico, and any
significant or persistent shower or thunderstorm activity would
lead to flooding or even mud slides during the weekend.

Another area of low pressure, invest 92L, located about 900 miles
east of the Leeward Islands is forecast to move near the region by
Sunday. Based on the latest information of the NHC, this system
has a 70 percent chance of formation in the next 48 hours and
should move northeast of the islands on Sunday as a tropical wave.
Regardless of the formation of a tropical cyclone, model guidance
suggested a wet pattern across the region. Is important to
monitor the progress of this disturbance.

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

Although the aforementioned area of low pressure, invest 92L,
should be located west of the area by Monday, associated moisture
will continue to prevail across the northeast Caribbean.
Therefore, the potential for showers and thunderstorms across the
local isles continues.

An overall wet pattern is expected to prevail Tuesday through
Thursday as a broad surface trough develops across the tropical
Atlantic and into the northeast Caribbean promoting moisture
convergence with PW values near two inches. A drier air mass is
then expected Friday through Sunday.

&&

.AVIATION...VFR conds with limited SHRA activity expected across
PR/USVI today. A few -SHRA are expected across TJSJ/TIST/TISX at
least until 18/12z, then FEW or SCT ceiling at FL025-FL050 expected
across the terminals in PR/USVI. On the other hand, TKPK/TNCM can
expect passing SHRA with SCT-BKN ceilings at FL018-FL100, as well as
VCTS due to the proximity of TS-Harvey aft 18/15z. Winds increasing
around 15 kts with occasional higher gusts aft 18z/12z.

&&

.MARINE...Tropical Storm Harvey is forecast to move westward
across the Caribbean Sea and pass south of the forecast area late
tonight into Saturday. This will result in hazardous seas 8 to 10
feet and winds 20 to 25 knots particularly across the Caribbean
waters and local passages. An area of low pressure about 900 miles
east of the Leeward Islands will reach the forecast area early
next week, regardless development, winds and seas are also likely
to increase across the offshore Atlantic waters Sunday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 80 90 79 / 20 40 40 50
STT 91 80 90 79 / 10 50 50 50

[cycloneye]

Area Forecast Discussion...DELAYED
National Weather Service San Juan PR
550 PM AST Fri Aug 18 2017

.SYNOPSIS...Fair weather skies prevailed across the region today as
drier air continued to spread across the region today. Only a few
isolated showers were so far noted over the coastal waters with no
significant accumulations expected to affect the islands the rest
of today. The moderate to strong east to northeast prevailing winds
continued to push most of the clouds quickly to the west southwest
and therefore limited significant development. Based on the latest
advisory from the National Hurricane Center at 500 PM ast...Tropical
Storm Harvey was located near LAT 13.4N... LON 62.9W...is forecast
to move westward across the Caribbean Sea and pass well south of the
forecast area tonight through Saturday.

&&

.SHORT TERM...Rest of today through Sunday...
Moisture will continue to erode with precipitable water expected
to drop to less than 1.50 inches by early Saturday, as drier air
will filter in from the northeast and a mid to upper level ridge
will build across the region from the northeast. In addition,
aerosol products and model guidance all suggests the presence of
Saharan dust particulates across the region. Therefore, fairly dry
and sable conditions should prevail through Saturday morning.

By Saturday afternoon, expect increasing cloudiness and moisture
once again due to peripheral moisture from Harvey propagating
northwards across the region. The center of Tropical Storm Harvey
is forecast to move well south of the islands and across the
Caribbean waters overnight through Saturday. Although no direct
impact of Harvey is anticipated across the region, a gradual
increase in moisture is likely by Saturday afternoon. As a result,
shower and thunderstorm activity is expected to increase during
the afternoon hours.

Increasing moisture and instability aloft is expected to continue
on Sunday, as an area of low pressure/invest 92L...located east
of northern Leeward Islands is forecast to move just northeast of
the region. Based on the latest information of the National Hurricane
Center, this system has a 60 percent chance of formation in the next
48 hours and should continue to move northeast of the islands as a
tropical wave. Model guidance all suggest a moist and unstable weather
pattern across the region into early next with good potential for early
morning and afternoon convection across the islands. Some of this activity
may produce periods of locally heavy rainfall in isolated areas.

.LONG TERM...Monday through Saturday...Although by Monday, the axis
of the Tropical wave/92L should be west and northwest of the region,
expected an elongated plume of moisture to be lifted across the region
in the prevailing east to southeast wind flow. Therefore, the potential
for showers and thunderstorms across the region will continue at least
through the middle of next week. A gradual drying trend and stable conditions
is expected by Thursday and into the weekend.

&&

.AVIATION...VFR conds expected through the forecast period. Winds
will continue from the east to ENE at about 15kt through the
afternoon. Slight chance of SHRA at TJMZ after 18/18Z could cause
VCSH but it should be brief. Winds to remain at 10 to 15KT overnight
with SHRA increasing after 19/00Z around the USVI.

&&

.MARINE...Small craft advisory in effect through Monday Morning
due to increasingly hazardous coastal winds and seas. Tropical
Storm Hervey will pass well to our south, but the winds will increase
across the local offshore Caribbean waters on Saturday and seas could
increase to 9 feet and occasionally up to 10 feet.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 80 90 79 89 / 40 40 50 50
STT 80 90 79 88 / 50 50 50 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
520 AM AST Sat Aug 19 2017

.SYNOPSIS...Tropical Storm Harvey will continue to move westward
across the Caribbean Sea, passing well south of the forecast area
throughout the day. The chance for showers and thunderstorms are
expected to increase across the local isles during the weekend as
the peripheral moisture of TS Harvey reaches the forecast area as
well as invest 92L likely to move northeast of the area on
Sunday-Mon.

&&

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

Partly cloudy skies prevailed across Puerto Rico and the U.S.
Virgin Islands overnight. Some showers affected mainly the
northern U.S. Virgin Islands and the eastern half of Puerto Rico.
Some of these showers produced brief periods of moderate to heavy
rainfall.

An increase in shower activity is expected today as trade winds will
transport patches of low level moisture across the region. This
moisture in combination with daytime heating and local effects will
produce scattered showers with isolated thunderstorms this afternoon
mainly across the Cordillera Central of Puerto Rico. In the meantime,
Tropical Storm Harvey will continue to pass well south of the region
today.

By Sunday, an area of low pressure is expected to pass mainly north
of the area. However, plenty of moisture associated with this system
will aid in the development of showers and thunderstorms once again
Sunday afternoon and will continue into the early morning hours on
Monday. By Monday afternoon, at this time, showers and thunderstorms
are expected to develop mainly north of the Cordillera Central of
Puerto Rico. Rest of the area, some passing showers are expected.

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

As moisture associated with invest 92L moves away, a drier air
mass in expected to encompass the forecast area on Tuesday. This
drier air mass is expected to be short-lived as a mid to upper
level trough establishes north enhancing moisture advection Wed-
Thu. By the end of the workweek and into the upcoming weekend, a
mid level ridge is then expected to build across the central
Atlantic and into the northeast Caribbean to result once again in
moisture erosion. Therefore a seasonal weather pattern is expected
to prevail much of the forecast period with locally induced
showers and thunderstorms each day. At this time, the best chance
for shower and thunder activity is expected Wed-Thu due to
moisture advection as the proximity of the upper trough.

&&

.AVIATION...Mainly VFR conditions will prevail across all TAF sites
through at least 19/16Z. Periods of MVFR conditions with mountain
obscurations will prevail across TJBQ and TJMZ from 19/16Z through
19/22Z in SHRA/TSRA. VCSH can be expected elsewhere.

&&

.MARINE...Tropical Storm Harvey will continue to move westward
across the Caribbean Sea, passing well south of the forecast area
throughout the day. This will result in hazardous seas 8 to 10
feet and winds 20 to 25 knots particularly across the Caribbean
waters and local passages. Hazardous seas will continue to prevail
across the offshore Atlantic waters through Monday as an area of
low pressure east northeast of the Leeward Islands moves to the
northeast of the forecast area.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 90 80 / 40 40 50 30
STT 91 81 88 81 / 40 50 50 60

[cycloneye]

Area Forecast Discussion...DELAYED
National Weather Service San Juan PR
531 PM AST Sat Aug 19 2017

.SYNOPSIS...Doppler radar and Satellite images continued to
depict areas and clusters of showers/thunderstorms on the
periphery of what is now Tropical Depression Harvey, propagating
northwards across the forecast area. This added moisture along
with good forcing and unstable conditions aloft aided in the
development of scattered to numerous showers and isolated
thunderstorms across the islands and coastal waters especially
over and around Puerto Rico. Expect this trend to continue through
at least the early evening hours, with a gradual diminishing of
the convective activity over much of the land areas by late
evening.

&&

.SHORT TERM...Overnight though Monday...Showers and thunderstorm
activity across the region should continue to diminish over land
areas and the coastal waters by late evening, as the recently
downgraded Tropical Depression Harvey will move farther westward
into the Central Caribbean waters. The trade winds are then expected
to become more east to southeast but will continue to transport an
elongated plume of low level moisture across the region, as another
tropical wave/area of low pressure lifts northwards and just northeast
of the region. This additional moisture and accompanying shower activity
will reach parts of the north and east sections of the islands during
the early morning hours on Sunday. For the rest of the day on Sunday,
expect good moisture convergence, in combination with daytime heating
and local effects, as well as the marginal instability aloft to support
periods of scattered to numerous showers with isolated thunderstorms
during the afternoon. The activity should be focused mainly across the
Cordillera Central and northwest sections of Puerto Rico including
parts of the San Juan metro area. By Monday afternoon, at this time,
showers and thunderstorms are expected to develop mainly north of the
Cordillera Central of Puerto Rico with only quick passing streamer like
shower activity expected elsewhere.

.LONG TERM...Tuesday through Sunday...As moisture associated with
area of low pressure/invest 92L moves away, a drier air mass in expected
to encompass the forecast area on Tuesday. This drier air mass is expected
to be short-lived as a mid to upper level trough is forecast to establish
just north of the forecast area. This along with available moisture
will enhance convective development across the region Wednesday through
Thursday. By Friday and into the upcoming weekend, a mid level ridge
is then expected to build across the central Atlantic and into the
northeast Caribbean to result once again in moisture erosion and stable
conditions across the region. Therefore a more seasonal weather pattern
is expected to prevail with locally induced showers and thunderstorms
each day.

&&

.AVIATION...Mostly VFR conditions are expected overnight across the
local flying area. However, brief periods of SHRA will affect the
Leewards, USVI and TJSJ TAF sites. Winds from the ESE are expected
to decrease at 10-15 knots after 19/23Z, increasing again at 15-20
Knots with higher gusts after 20/13Z. Periods of MVFR conditions
with mountain obscurations are expected across TJBQ and TJMZ from
20/16Z through 20/22Z in SHRA/TSRA.

&&

.MARINE...Recently downgraded Tropical depression Harvey will
continue to move westward and exit the eastern Caribbean waters
later tonight. However expected hazardous seas between 6 to 8 feet
and winds between 15 to 20 particularly across the Caribbean waters
and local passages. Hazardous seas will continue to prevail across
the offshore Atlantic waters through Monday as an area of low pressure
east northeast of the Leeward Islands moves to the northeast of the
forecast area.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 79 90 80 89 / 40 60 40 30
STT 81 88 81 90 / 50 50 50 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
515 AM AST Sun Aug 20 2017

.SYNOPSIS...Weak waves will continue to pass through the area even
as high pressure weaken after Monday. High pressure will return to
the northeast central Atlantic to reinvigorate the easterly trade
winds. Bands of good moisture will accompany the tropical waves
bringing scattered showers to the area. The best moisture of the
week is expected today.

&&

.SHORT TERM...Today through Tuesday...
Scattered showers were observed across the U.S. Virgin Islands,
Vieques, Culebra as well as across the eastern and northern
sections of Puerto Rico during the overnight hours. This activity
was associated with the leading edge of an area of low pressure
which was located north of the U.S. Virgin Islands early this
morning. This area of low pressure is producing a big area of
showers and thunderstorms extending for a few hundred miles
eastward. Latest satellites images indicated plenty of moisture
associated with this system and that will continue to propagate
westward throughout the day. As a result, the combination of the
available moisture with strong daytime heating and orographic
effects will be sufficient to produce scattered to numerous
showers with thunderstorms this afternoon across most of the
islands. The heaviest activity will occur across the San Juan
metropolitan area and across the Cordillera Central of Puerto
Rico. As prevailing winds shift more southeasterly, the shower
and thunderstorm activity will move northwest affecting mainly the
northern half of Puerto Rico later in the afternoon hours.
Periods of heavy rainfall with frequent lightning and strong gusty
winds can be expected. Urban and small stream flooding will be
likely this afternoon across these areas.

By late tonight into Monday, a drier air mass is expected to move
across the region from the east. Therefore, limited shower activity
is expected to occur during this period. Shower and thunderstorm
development can be expected once again Monday afternoon, but only
across the western interior and west sections of Puerto Rico. At
this time, looks like the rest of Puerto Rico will only see some
passing showers from time to time. An area of low level moisture is
expected to affect the region Tuesday.

.LONG TERM...Wednesday through Sunday...
A north-south oriented TUTT will move through the southern
Caribbean during the last part of the week but winds aloft will
remain mostly below 20 knots in the forecast area. The next
tropical wave moves through on Wednesday and another band of
moisture moves through on Saturday followed by another wave on the
Sunday after. This, local effects, and generally favorable low-
level moisture will keep scattered showers and thunderstorms in
the forecast area-wide with showers and thunderstorms likely each
afternoon in western Puerto Rico, but upper level dynamics will
remain limited through the period, offering little support for
more organized convection. Current GFS does not develop any more
tropical cyclones east of the forecast area through Sunday.

&&

.AVIATION...Mainly VFR conditions will prevail across most TAF sites
through at least 20/16Z. Periods of MVFR conditions can be expected
in and around TNCM and TKPK through at least 20/18Z. Meanwhile,
Periods of MVFR conditions with mountain obscurations can be
expected across TJSJ, TJMZ and TJBQ from 20/16Z through 20/22Z in
SHRA/TSRA. VCSH can be expected elsewhere. Winds becoming east
southeast below FL130 til 21/00Z. Max winds till then E at 25 kt
from FL320-400.

&&

.MARINE...Seas still at or above 7 feet at the outer buoy and
likely extending south in the forecast area this morning, but will
subside this afternoon. Seas will reach a minimum by Thursday and
are expected to be below 4 feet everywhere then. Winds increase
somewhat behind a passing ridge on Thursday causing seas to
increase.



&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 79 89 79 / 70 40 30 30
STT 88 81 90 81 / 50 50 40 40