Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
357 PM AST Sat Jul 15 2017

.SYNOPSIS...Tropical wave passed to the south of the local area
and is now over the Hispaniola. Strong SFC high pressure across
the Central Atlantic is keeping moderate easterly winds across the
local area. TUTT low to the northwest of the local area will stay
in the area for the rest of the weekend then a weak upper high
will move over the local area. Tropical wave is expected to move
south of the local islands on Tuesday into Wednesday.

&&

.SHORT TERM...Today through Monday...
The tropical wave that passed Puerto Rico today and entered the Mona
channel this afternoon has weakened considerably. Few showers were
seen in the forecast area and the only thunderstorms as of 15/1730Z
were well south of 15 north. Some limited convection is forming over
the Cordillera Central and more is expected, but Saharan dust
appears to be playing a large role in limiting the development of
convection this afternoon. That dust will diminish very slowly
through Tuesday. Currently it limits visibilities in the area to 7 to
15 miles. The GFS shows precipitable water diminishing slowly
through Monday morning when it will be around 1.77 inches, but then
it drops abruptly to below 1.4 inches Monday evening before
recovering Tuesday morning and the upcoming tropical wave. With TUTT
lows north of 28 north, and high pressure with very weak gradients
at upper levels around the local area and no significant divergence
aloft through Monday, and after some high values pass over western
Puerto Rico this evening, upper levels will contribute little to the
local convergence-driven afternoon shower activity Sunday or Monday.
Since trade winds from a strong quasi-stationary high in the eastern
and central Atlantic Ocean will be easterly that shower activity
will be mostly along the Cordillera Central and western Puerto Rico.
Some shower activity will be seen on the eastern coast of Puerto
Rico during the night and early morning hours, but accumulations
where rain occurs will be minimal.

.LONG TERM...Tuesday through Sunday...
A wind surge with an increase in moisture is expected briefly on
Tuesday due to an easterly wave that is expected to pass through
the local area. At this time it looks like this wave will leave
most of the moisture and rainfall to the south of the local
islands from Tuesday to Wednesday. This will be followed by
Saharan dust and drier conditions through Thursday morning. Normal
to above normal temperatures will continue across coastal areas
of the islands through at least mid week. Another increase in
moisture is expected late in the week into the weekend as another
tropical wave moves across the local area.


&&

.AVIATION...SHRA/TSRA forming in interior PR along Cordillera
Central and expect isold TSRA by 15/1830Z with mtn obscurations
and MVFR conds til 15/22Z near TJMZ/TJBQ. Elsewhere expect VFR
conds at all TAF sites thru 16/18Z with limited visibilities of
7-15 miles in Saharan dust and even lower slant ranges. Winds alf
east 5-15 kt up thru FL200. Max winds S arnd 30 kt btwn FL200-320.



&&

.MARINE...


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
415 AM AST Sun Jul 16 2017

.SYNOPSIS...Surface high pressure across the Central Atlantic
waters will maintain moderate trades through the forecast period.
Upper ridge will continue aloft through Monday. Afternoon
convection should prevail each day due to local effects. SAL is
forecast to move over the FA by mid week. Next disturbance is
forecast to remain south of the area on Wednesday.


&&

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

The tropical wave that affected the region yesterday is now over
Hispaniola. This wave will continue to move away from the region
today. GFS model guidance indicates that PWAT values are expected
to diminish today through at least Monday. At the same time, an
upper level ridge is expected to remain across the region today
and Monday limiting the development of widespread showers and
thunderstorms. However, moisture embedded in the trades is
forecast to move across the region from time to time both days.
This moisture in combination with daytime heating and local
effects will be sufficient to induce the development of showers
and thunderstorms but mostly along the Cordillera Central and
western sections of Puerto Rico each afternoon. Some shower
activity is also expected on the eastern coast of Puerto Rico as
well as across the U.S. Virgin Islands, Vieques and Culebra during
the night and early morning hours, but rainfall accumulations
will be minimal.

Model guidance indicates that a surge of moisture is expected to
move over the region on Tuesday, slightly increasing the chance of
showers across the local islands especially Tuesday afternoon. A
tropical wave now along 45 W will continue to move westward at 15 to
20 mph during the next several days. Accordingly to the National
Hurricane Center, some slow development of this system is possible
over the next few days. GFS model guidance indicated that the wave
will pass south of the region by mid week.

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

At the moment, a low pressure area is forecast to pass well to
the south of the islands on Wednesday. A Saharan air layer is
expected to encompass the region creating hazy skies and drier
conditions through Thursday. However, weather conditions could
change from now to then, depending on the development of the low
pressure area. Normal to above normal temperatures will continue
across coastal areas of the islands through at least Thursday.
Two tropical waves are expected to affect the islands, one on Friday
and the other one between Sunday and Monday.


&&

.AVIATION...Mostly VFR conditions are expected across the local
flying area with VCSH across the Leeward, USVI and TJSJ TAF sites
during the rest of the morning hours. SHRA/TSRA expected after
16/16z and may result in MVFR conditions in and around TJMZ and
TJBQ. ESE winds of 10-15 knots expected after 16/13Z with some sea
breeze variations.


&&

.MARINE...Small crafts should exercise caution across the Atlantic
waters just north of PR due to winds up to 20 knots. Elsewhere,
seas should range between 2-5 feet and winds from the east will
prevail between 10-15 knots. Sea breeze variations across the
western coastal waters of PR are also expected. There is a
moderate risk of rip currents for the north, east and southern
beaches of PR and St. Croix.


&&

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

[cycloneye]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Sun Jul 16 2017

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

A low pressure trough located about 1000 miles east-southeast of
of the Windward Islands is producing disorganized showers and
thunderstorms. Although this system is close to dry air, some
slow development is possible over the next few days while the
system moves westward at 15 to 20 mph. An Air Force Reserve
reconnaissance aircraft is scheduled to investigate the
disturbance Monday afternoon, if necessary.
* Formation chance through 48 hours...low...20 percent.
* Formation chance through 5 days...medium...40 percent.

Forecaster Brown

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
409 PM AST Sun Jul 16 2017

.SYNOPSIS...Strong surface high pressure across the Central
Atlantic will continue promoting easterly winds across the local
area for the next few days. Upper high pressure will remain over
the local area through Monday. A tropical wave now at about 48W
is forecast to move south of the local area on Wednesday.

&&

.SHORT TERM...Today through Tuesday...
Shower activity has just begun over Puerto Rico and downstream from
the U.S. Virgin Islands with low level flow only slightly south of
east. Tops have not yet reached 22 Kft as of 16/1745Z, but further
development is expected.

The GFS continues to show a north-south band of moisture in
northeast flow at 700 mb and there is some evidence for it in the
satellite imagery and the MIMIC product, but it appears to be a
little farther away than the model indicates. Nevertheless it should
be sufficient and close enough to cause some night and early
morning shower activity around the northern U.S. Virgin Islands
and eastern Puerto Rico by 17/12Z. Do not expect much more than
isolated showers at this time. On Monday columnar moisture begins
to fall and some dry air parcels move through above the moist
marine layer. Although this will limit showers in most areas,
still expect showers and possibly a thunderstorm or two in western
Puerto Rico. Then on Tuesday a narrow band of moisture moves
through the area in time for the afternoon heating and better
showers are expected. Although that moisture band was associated
with a tropical wave that is expected (by the GFS) to generate a
tropical system that will cross through the ABC islands Tuesday
evening through early Wednesday morning, it will become very
stretched and almost disassociated with the system since it has
moved out so far ahead of it. That system will move into the
eastern Caribbean south of 15 degrees north latitude Tuesday
night. With good easterly flow to the north this will begin the
entrance of more Saharan dust, drier air and stronger winds later
on Wednesday.

.LONG TERM...Wednesday through Monday...From Previous discussion.

At the moment, a low pressure area is forecast to pass well to
the south of the islands on Wednesday. A Saharan air layer is
expected to encompass the region creating hazy skies and drier
conditions through Thursday. However, weather conditions could
change from now to then, depending on the development of the low
pressure area. Normal to above normal temperatures will continue
across coastal areas of the islands through at least Thursday.
Two tropical waves are expected to affect the islands, one on Friday
and the other one between Sunday and Monday.

AVIATION...Mostly VFR conditions are expected across the local
flying area with VCSH across the Leeward, USVI and TJSJ TAF sites
during the rest of the morning hours. SHRA/TSRA expected after
16/16z and may result in MVFR conditions in and around TJMZ and
TJBQ. ESE winds of 10-15 knots expected after 16/13Z with some sea
breeze variations.


&&

.AVIATION...VFR conditions now prevail everywhere in the FA, but,
afternoon convection has begun and will cause areas of mtn
obscurations and MVFR conditions--mainly in the central part of
wrn PR. Sfc winds E 10-15 kt with strong sea breeze variations
becoming less than 10 kt with land breezes aft 16/23Z. Winds alf
blo FL200 ENE-E 10-25 kt, but bcmg more ESE after 17/12Z. Max
winds blo FL500 are 065/25 kt at FL140 at 17/00Z.


&&

.MARINE...Seas will be up to 5 feet with 15 knot winds through
Monday. Then as tropical wave approaches seas may increase up to
6 to 8 feet across the offshore waters on Wednesday, with small
craft advisories likely depending on the development of the wave
currently near 48W.

&&

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

[cycloneye]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 PM EDT Sun Jul 16 2017

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

1. A weak area of low pressure located about 900 miles east-southeast
of the Windward Islands continues to produce disorganized showers
and thunderstorms. Environmental conditions are marginally
conducive for some development of this system before it reaches the
Lesser Antilles in two to three days. After that time, less
favorable upper-level winds are expected to hinder additional
development. An Air Force Reserve reconnaissance aircraft is
scheduled to investigate the disturbance Monday afternoon, if
necessary.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...medium...40 percent.

Forecaster Pasch

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
509 AM AST Mon Jul 17 2017

.SYNOPSIS...Typical afternoon showers are expected each afternoon.
Saharan dust will affect the region between Tuesday afternoon and
Thursday...limiting the shower activity and the visibility across
the local area. The next tropical wave will likely remain south of
the area by midweek.

&&

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

Satellites images as well as GFS model guidance indicates patches of
moisture embedded in the trade wind flow moving westward across the
surrounding waters. This moisture will continue to produce isolated
to scattered passing showers across the U.S. Virgin Islands,
Vieques, Culebra as well as across eastern Puerto Rico during the
rest of the morning hours. This moisture in combination with daytime
heating and local effects will be sufficient to induce the
development of showers and thunderstorms mostly along the Cordillera
Central and western sections of Puerto Rico this afternoon.

A relatively drier air mass is expected to move across the region
tonight before a north-south narrow band of moisture moves through
the area on Tuesday just in time for the afternoon heating. Thus,
showers and thunderstorm are expected Tuesday afternoon but mainly
across western and interior sections of Puerto Rico. Some shower
activity is also expected on the eastern coast of Puerto Rico as
well as across the U.S. Virgin Islands, Vieques and Culebra Tuesday
morning hours, but rainfall accumulations will be minimal. Another
area of relatively drier air with Saharan dust is expected to
encompass the region Tuesday night, Wednesday and beyond,
limiting the showers and thunderstorms activity.

A tropical wave and its associated low pressure located near 45 west
this morning will continue to move westward across the tropical
Atlantic today and tomorrow. Accordingly to the National Hurricane
Center, some slow development of this system is possible over the
next few days. GFS model guidance indicated that this system will
pass south of the region on Wednesday.

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

Drier and stable conditions are forecast to continue across the
Northeast Caribbean region Thursday and early Friday. Moderate
concentrations of Saharan Dust will limit the shower activity and
visibility in some parts of Puerto Rico and the Virgin Islands.
An area of disturbed weather monitored by the National Hurricane
Center will likely move northeast of the region on Friday.
Moisture in the periphery of this disturbance will bring scattered
showers over Puerto Rico and the U.S. Virgin Islands late Friday
into Saturday. Conditions will remain somewhat moist and unstable
during the weekend and early next week...favoring scattered
showers at times.

&&

.AVIATION...Mostly VFR conditions are expected across the local
flying area with VCSH across the Leeward, USVI and TJSJ TAF sites
during the rest of the morning hours. SHRA/TSRA expected after
17/16z and may result in MVFR conditions in and around TJMZ and
TJBQ. ESE winds of 10-15 knots expected after 16/13Z with sea breeze
variations.

&&

.MARINE...Winds of 10-20 knots and seas of 3-5 feet will prevail
through tonight. As a result...small craft operators should
exercise caution due to fresh winds. Marine conditions will
deteriorate somewhat by midweek as a tropical wave moves across
the Eastern Caribbean. Therefore...seas will gradually build to
4-6 feet or greater late Tuesday into Wednesday. Conditions will
likely return to normal late Thursday into Friday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 80 90 81 / 30 30 30 10
STT 87 81 88 81 / 30 30 30 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
447 AM AST Tue Jul 18 2017

.SYNOPSIS...A seasonal weather pattern with passing showers embedded
in the trades at times and locally induced afternoon thunderstorms
across west Puerto Rico will continue to prevail during the next
few days. Tropical Storm Don, about 250 miles ESE of Barbados is
forecast to pass well south of the region on Wednesday. A tropical
wave over the central tropical Atlantic is monitored by the
National Hurricane Center for signs of development. This
disturbance is expected to pass northeast of the region Fri- Sat.

&&

.SHORT TERM...Today through Thursday...
Satellites images are showing a line of showers and thunderstorms
moving west approaching the U.S. Virgin Islands this morning.
This activity is associated with the leading edge of a Tropical
Wave which was located across the Lesser Antilles early this
morning. This moisture in combination with daytime heating and
local effects will be sufficient to induce the development of
showers and thunderstorms mostly along the Cordillera Central and
western sections of Puerto Rico this afternoon. For tonight, a
drier airmass will encompass the region which will result in less
shower activity.

Tropical Storm Don was located less than 300 miles east of Barbados
this morning. It was moving west at around 18 mph. Don is expected
to affect the Windward islands tonight. On the current forecast
track by the National Hurricane Center, Don is expected to pass well
south of the local islands late Wednesday into early Thursday.

.LONG TERM...Friday through Wednesday...
A tropical wave over the tropical central Atlantic monitored by
the National Hurricane Center will likely move northeast of the
region Friday and Saturday. Accordingly to model guidance,
moisture in the southern periphery of this disturbance will
produce and increase in cloudiness and showers across Puerto Rico
and the U.S. Virgin Islands late Friday into Saturday. A short-
lived relatively drier and stable air mass is forecast to move
across the region on Sunday, before a narrow band of moisture
north-south oriented reach the Northeast Caribbean Monday
increasing again the chance of showers and thunderstorms. Weather
conditions will remain somewhat moist and unstable during the rest
of the forecast period, favoring the development of isolated to
scattered showers across the U.S. Virgin Islands and eastern PR
during the nights and early in the morning followed by the typical
afternoon convection each afternoon across western and interior
sections of Puerto Rico.

&&

.AVIATION...Mostly VFR conditions are expected across the local
flying area with VCSH across the Leeward, USVI and TJSJ TAF sites
during the rest of the morning hours. SHRA/TSRA expected after
18/16z and may result in MVFR conditions in and around TJMZ and
TJBQ. ESE winds of 10-15 knots expected after 18/13Z with sea breeze
variations.

&&

.MARINE...Seas are expected to briefly increase up to 7 feet with
occasional seas up to 9 feet late tonight and Wednesday as
tropical storm Don moves across the Caribbean sea well south of
the region. Small Craft Advisory will be in effect for most of the
local waters from late tonight through late Wednesday night.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 80 92 81 / 40 10 10 10
STT 90 81 91 80 / 40 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
432 AM AST Wed Jul 19 2017

.SYNOPSIS...A strong surface high pressure across the Central
Atlantic will continue to promote easterly winds for the next
several days. A tropical wave, remnants of Tropical Storm Don,
is expected to pass well south of the local area today and
tonight. Another tropical wave, currently being monitored by the
National Hurricane Center, is expected to move northeast of the
region this weekend increasing the showers and thunderstorms over
the region. A Saharan air layer is forecast to encompass the
region today and Thursday.

&&

.SHORT TERM...Today through Friday...
Clear skies prevailed across Puerto Rico and the U.S. Virgin
Islands overnight. Very light passing showers were noted across
the eastern half of Puerto Rico. A very dry airmass will continue
to dominate the local region today. Only some showers are expected
to develop this afternoon mainly across the west section of
Puerto Rico, but overall will remain dry. Meanwhile, the remnants
of Tropical Storm Don will pass south of the local area today. No
weather is expected associated with this system. Also, hazy
conditions are expected as Saharan dust encompass the region. This
hazy conditions are expected to prevail through at least
Thursday. For Friday, An increase in cloudiness and showers are
expected as low level moisture moves across the region.

.LONG TERM...Saturday through Wednesday...
A tropical wave over the tropical central Atlantic to the east of
the Lesser Antilles monitored by the National Hurricane Center
will likely move northeast of the region Saturday and Sunday.
Accordingly to model guidance, moisture associated with this
disturbance is expected to produce and increase in shower and
thunderstorm activity across Puerto Rico and the U.S. Virgin
Islands during the upcoming weekend. GFS model guidance suggests
that PWAT values will increase above 2.00 inches Saturday and
Sunday, decreasing to about 1.70 on Monday. After the passage of
the wave, the region will return to a typical summer weather
pattern Monday through at least Wednesday, with isolated to
scattered passing showers across the U.S. Virgin Islands, Vieques,
Culebra and eastern sections of Puerto Rico, followed by
afternoon showers and thunderstorms across western and interior
section of Puerto Rico. A surge of moisture associated with
another tropical wave is forecast to move across the region
Thursday and Friday.

&&

.AVIATION...VFR conditions are expected across the local flying area
through the forecast period. Low level winds will be mainly east at
10 to 15 kts with higher gusts. Hazy conditions are expected, but
visibilities will remain P6SM across all TAF sites.

&&

.MARINE...Seas will remain deteriorated today and tonight. Small
Craft Advisories are in effect for most of the local waters due to
increasing seas up to 8 feet with occasional seas up to 10 feet
and easterly winds at around 20 knots with higher gusts. There is
a high risk of rip current for the northwest to north central and
southwest to southeast beaches of Puerto Rico and for beaches of
St Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 81 89 78 / 20 20 50 50
STT 91 80 91 79 / 20 20 50 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
527 PM AST Wed Jul 19 2017

.SYNOPSIS...Saharan air layer will continue through at least late
Thursday over the forecast area. Weak perturbation moves over the
islands from the east on Friday. Next disturbance is expected to
increase shower and thunderstorm activity through the weekend.
Surface high develops north of the islands on Saturday promoting
east to northeast trade winds. Mid level ridge will continue to
promote drier air and trade wind cap until at least Friday.


&&

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

Saharan air layer and mid level ridge will continue to limit
shower development over the islands through at least Thursday.
However on Thursday afternoon, short wave trof above could aid
into the development of afternoon convection over the southwest
quadrant of PR. Streamers are expected to develop each day over
the USVI. However, no significant rainfall amounts are expected
as the mid level ridge seems to be quite strong to inhibit
widespread rain activity. On Friday, a weak easterly perturbation
is expected to increase the available moisture over the islands
and therefore should aid in the development of shower and possible
thunderstorm development during the afternoon hours across the
northwest quadrant of PR. Scattered showers should also increase
across the Anegada passage into the Caribbean and Atlantic waters
later during the day on Friday.



.LONG TERM...Saturday through Wednesday...From previous
discussion issued at 432 AM AST Wed Jul 19 2017...

A tropical wave over the tropical central Atlantic to the east of
the Lesser Antilles monitored by the National Hurricane Center
will likely move northeast of the region Saturday and Sunday.
Accordingly to model guidance, moisture associated with this
disturbance is expected to produce and increase in shower and
thunderstorm activity across Puerto Rico and the U.S. Virgin
Islands during the upcoming weekend. GFS model guidance suggests
that PWAT values will increase above 2.00 inches Saturday and
Sunday, decreasing to about 1.70 on Monday. After the passage of
the wave, the region will return to a typical summer weather
pattern Monday through at least Wednesday, with isolated to
scattered passing showers across the U.S. Virgin Islands, Vieques,
Culebra and eastern sections of Puerto Rico, followed by
afternoon showers and thunderstorms across western and interior
section of Puerto Rico. A surge of moisture associated with
another tropical wave is forecast to move across the region
Thursday and Friday.


&&

.AVIATION...VFR conditions with hazy skies but with VIS P6SM
expected though the FCST prd. VCSH still possible at TJMZ/TJBQ
thru 22z and trade wind showers near TIST/TISX/TNCM/TKPK at
times. Easterly winds at 15 to 20 kt with higher gusts and sea
breeze variations, then around 10 kt overnight increasing once
again at 15 to 20 kt and gusty aft 20/13z.


&&

.MARINE...Latest buoy data are indicating seas between 4-6 feet
and east winds under 20 knots across the surrounding waters of the
islands. Seas should gradually continue to improve through
Thursday morning and small craft advisories are expected to be
discontinued by then. Small crafts should continue to exercise
caution due to seas up to 6 feet and east winds up to 20 knots.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 80 89 78 89 / 20 20 30 50
STT 80 91 79 90 / 20 20 40 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
415 AM AST Thu Jul 20 2017

.SYNOPSIS...A mid level ridge will hold over the region until
early Friday. Saharan air layer will remain across the region
today. Mid level ridge expected to erode on Friday as a narrow
surge of moisture moves over the region. A tropical wave along 50
West will reach the region Saturday and Sunday increasing the
shower activity across the local islands. Surface high pressure
expected to build over the Atlantic, north of the islands during
the weekend inducing an easterly wind flow over the northeast
Caribbean.

&&

.SHORT TERM...Today through Saturday...
Partly cloudy skies prevailed across Puerto Rico and the U.S.
Virgin Islands overnight. Very light passing showers were noted
across the Caribbean coastal waters and also north of the local
islands. Some of these showers moved quickly over land, affecting
the northern U.S. Virgin Islands and the north coast of Puerto
Rico. A very dry airmass will continue to dominate the local
region today, as an upper level ridge remains across the region. A
big change from previous days will be that winds have shifted
from the east to northeast overnight and early this morning. As a
result, temperatures along the northern slopes of Puerto Rico will
remain at or below average this afternoon. Only some showers are
expected to develop this afternoon mainly across the southwest
section of Puerto Rico, but overall will remain dry.

Hazy conditions are expected to diminish today. In fact, latest
model guidance indicated most of the dust will be out of our area by
this afternoon. For Friday, An increase in cloudiness and showers
are expected as low level moisture moves across the region. A moist
environment is also expected for Saturday. As a result, showers and
thunderstorms are expected to affect the region both days.

.LONG TERM...Sunday through Thursday...
A tropical wave over the tropical central Atlantic to the east of
the Lesser Antilles is expected to move over the region during the
weekend. Accordingly to model guidance, this feature is expected
to produce only a slight increase in moisture across the local
islands. GFS model guidance suggests that PWAT values will remain
close to 2.00 inches Saturday and Sunday, decreasing to about
1.70 on Monday through Wednesday as a Saharan Air Layer encompass
the region. No significant weather feature are forecast to affect
the region until at least Wednesday with a typical summer weather
pattern expected. During that period, isolated to scattered
passing showers will affect the U.S. Virgin Islands, Vieques,
Culebra and eastern sections of Puerto Rico during the night and
early morning hours, followed by afternoon showers and
thunderstorms across western and interior section of Puerto Rico
each day. Another tropical wave is forecast to reach the eastern
Caribbean on Thursday.

&&

.AVIATION...VFR conditions are expected across the local flying area
through the forecast period. Some VCSH can be expected around TJMZ
from 20/16z through 20/22z. Low level winds will be mainly
northeast at 10 to 15 kts with higher gusts. Hazy conditions are
expected, but visibilities will remain P6SM across all TAF sites.

&&

.MARINE...Seas will continue to subside today. The Small Craft
Advisories expired or were cancelled. However small craft should
continue to exercise caution across most of the local waters due
to seas up to 6 feet and winds up to 20 knots.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
433 PM AST Thu Jul 20 2017

.SYNOPSIS...Bands of moisture in minor troughs will cross through
the local area tonight, Friday and Friday evening, and Saturday.
A tropical wave will move across the area Saturday night followed
by generally drier air with patches of low level moisture through
most of next week.

&&

.SHORT TERM...Tonight through Saturday
A band of moisture has moved through the area and spawned a few
showers off of the coast at Cabo Rojo. There are also weak
streamers dissipating off of Vieques and Saint Croix. Another band
of moisture is moving toward Saint Croix out of the Leeward
Islands and will arrive overnight tonight with scattered showers.
Another patch of moisture will move through the area late Friday.
A dry area follows Friday night although low-level moisture will
bring the usual late night and early morning showers to the
northeast coast and slopes. Moisture begins to increase on
Saturday and will continue through Saturday night when the next
tropical wave moves through.

At upper levels...flow from the southwest will bring in an area of
divergence aloft overnight across western Puerto Rico, but with no
convection present to enhance, it will be of little effect. Upper
level flow then shifts to the southeast and becomes less than 15
knots. However some divergence aloft over the northwest third of
Puerto Rico will enhance the afternoon convection ahead of the
tropical wave and thunderstorms should be expected.


.LONG TERM...Sunday through Wednesday
After the passage of the tropical wave on Saturday night, moisture
will diminish through Tuesday evening. This will keep shower
activity limited during the period. Moisture patches at lower
levels will continue to pass through the area both Monday morning
and Monday evening in the easterly flow as high pressure at the
surface continues to dominate the central Atlantic. Moisture
returns Wednesday and Wednesday night for another increase in
showers.

&&

.AVIATION...VFR conditions expected, but -SHRA in the VCTY of
TJSJ/TIST and TISX/TNCM/TKPK are possible at times. Although hazy,
conditions with P6SM VIS continue, the Saharan air particles are
expected to diminish across the flying area through the rest of
the FCST Period. VCTS are expected after 21/00z at TNCM/TKPK, and
SHRA/+SHRA will affect E-PR/USVI terminals after 21/06z. Northerly
winds at 15 to 20 kt with higher gusts, decreasing at 10 to 15 kt
aft 20/22z.


&&

.MARINE...Highest seas will pass through the area tonight with
subsiding seas through Thursday of next week. Hence no small craft
advisories are expected for the next 7 to 10 days.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 78 88 81 89 / 40 30 30 30
STT 80 88 80 90 / 50 50 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
522 AM AST Fri Jul 21 2017

.SYNOPSIS...A band of moisture with showers and gusty winds will
pass across the area through the early morning hours today before
a patch of slightly drier air moves in for the rest of the day.
Moisture will increase starting tonight as a tropical wave moves
in, which will pass over the area on Saturday into Sunday,
bringing deeper moisture and additional shower and thunderstorm
activity to the local area.

&&

.SHORT TERM...Today through Sunday...
Showers with periods of moderate to heavy rain as well as gusty
winds are affecting portions of the U.S. Virgin Islands and
Puerto Rico during the morning hours. Most of these showers are
expected to affect St Croix and the east and south sections of
Puerto Rico, but most of the local islands should observe at least
a few showers. Then, showers and thunderstorms are expected to
develop over the west and interior municipalities of Puerto Rico
during the afternoon hours.

A tropical wave is forecast to bring a moist and unstable atmosphere
during the weekend increasing the potential for frequent showers and
thunderstorms Saturday and Sunday. Model guidance suggest the
arrival of a dry air mass with Saharan air particles which can limit
showers across the region by late Sunday night into Monday.

.LONG TERM...Monday through Saturday...
Near normal moisture is expected across the local area through
most of the upcoming week. A surface high pressure across the
Atlantic will keep winds mainly from the east to the east
southeast. This general pattern should cause seasonable
temperatures and weather pattern for most of this week with
passing showers in the overnight and morning hours across the
local waters, USVI, and eastern PR, then showers and thunderstorms
developing over PR due to local effects and showers possibly
streaming off the USVI. There is an enhanced chance of showers on
Thursday or Friday as a tropical wave approaches the local area
and an upper level low develops and settles over Hispaniola, which
will give us enhanced ventilation for thunderstorms to persist if
the long range models are correct. Near normal moisture and
seasonable conditions are forecast to return late Friday into
Saturday.


&&

.AVIATION...As a weak disturbance continues to move westward across
the Caribbean waters...scattered showers will continue to result in
brief periods of RA/VCSH through at least 12z across the USVI and PR
terminals at times. Surface winds expected to continue mainly from
the east at 10-15 kts with higher gusts near SHRA...gusty winds with
sea breeze variations expected after 13z. SHRA w/possible isolated
thunderstorms could develop over west PR between 16z-22z.

&&

.MARINE...Small craft operators should exercise caution as winds
will be up to 20 knots sustained with higher gusts near the
showers and the seas will be up to 6 feet. There is also a
moderate risk of rip currents across many of the local beaches.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 80 89 79 / 30 30 50 60
STT 89 80 89 80 / 50 30 50 60

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
416 PM AST Fri Jul 21 2017

.SYNOPSIS...Moisture will ramp up during the day Saturday ahead of
a tropical wave expected to cross through the U.S. Virgin Islands
Saturday evening and Puerto Rico overnight Saturday into Sunday.
Then somewhat drier air and some Saharan dust will move over the
area early next week. Moisture will increase on Wednesday and
again Thursday afternoon and evening with the passage of the next
tropical wave.

&&

.SHORT TERM...Tonight through Monday
At upper levels, winds remain light as low pressure over the
Bahama Islands gives way to a high pressure north northeast of the
area on Sunday.

The main features in the met picture today are the high pressure
that continues driving moderate to fresh easterly trade winds
across the area and the approaching tropical wave now just east of
60 west as evidenced by an area of convection at its apex near 22
north 58 west. Moisture will increase ahead of the wave on
Saturday increasing showers and thunderstorms, and then cross
through the area on Saturday night. The best divergence aloft will
also occur over Puerto Rico between midnight Sunday and Sunday
morning before 10 AM AST. Therefore we may have some atypical (at
least for this season so far) thunderstorms in the early morning
hours across eastern Puerto Rico and possibly the U.S. Virgin
Islands.

Although drier air follows on Sunday, enough residual moisture is
expected to keep good shower activity going in western Puerto
Rico until Sunday evening. Showers will begin to taper off in the
morning for the U.S. Virgin Islands and in the afternoon in
eastern Puerto Rico. Although moisture reaches a minimum for the
next several days on Monday evening, showers will continue since
that minimum columnar moisture is still around 1.65 inches.

.LONG TERM...Tuesday through Friday
Moisture will wrap around a 700 mb high north of us on Sunday and
return to the area from the northeast early Tuesday morning. Then
a brief dry slot on Wednesday night will herald the arrival of
another tropical wave from the east southeast Thursday and
Thursday afternoon. Moisture associated with this wave will
continue into the following weekend.

Although the TUTT low forming to our northeast next week will
move west, it will generally be too far away to be of much effect.
However a very weak low will move in early next weekend and could
increase the frequency of thunderstorms Friday and Saturday of
next week as it interacts with the increased moisture from the
tropical wave.

&&

.AVIATION...Mount obscurations expected to cont across the
interior and western sections of PR til 21/23z. SHRA expected at
TJMZ and in the VCTY of TJBQ til 21/23z. Dry air expected to move
in over the USVI, with VCSH elsewhere. Northerly winds at 15 to 20
knots with gusty winds in/near SHRA, then decreasing at 10 kts or
less btwn 21/23z-22/12z, but increasing once again at 15kt aft
22/13z. Winds alf less than 20 knots aft 21/21Z and e to ESE blo
FL280.


&&

.MARINE...After tonight maritime conditions are expected to remain
at 5 feet or less through the last weekend of July. And during
that time no small craft advisories are expected. However,
vigorous thunderstorms will be capable of generating, in their
immediate vicinity, local seas of 7 feet or better during the
passage of the tropical waves.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 80 88 78 90 / 40 60 50 40
STT 80 90 80 87 / 40 70 40 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
445 AM AST Sat Jul 22 2017

.SYNOPSIS...Tropical wave will move across the region this
afternoon into Sunday. TUTT low will develop and moves across the
southwest Atlantic early next week.

&&

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

Although a mid to upper level ridge will prevail throughout the
forecast period; there is a chance for showers and thunderstorms
across the local islands this afternoon into Sunday as a tropical
wave moves across the northeast Caribbean.

Mostly fair weather conditions will continue to prevail this morning
across Puerto Rico and the U.S. Virgin Islands. However, as a
tropical wave which is now located over the Lesser Antilles moves
closer to the forecast area, precipitable water is expected to
increase above the normal range. This will assure locally induced
showers and thunderstorms across the interior and western areas of
Puerto Rico this afternoon followed by passing showers with isolated
thunderstorms across the USVI and E PR this evening throughout
Sunday morning.

Lingering moisture combined with local effect will result in another
round of showers and thunderstorms over and north of the Cordillera
Central Sunday afternoon. As the wave moves away, a drier air mass
will encompass the forecast area Sunday night into Monday. Urban and
small stream flooding is likely with the heaviest showers.

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

At upper levels...TUTT low will dominates the northeast Caribbean
through Sunday. At low level, a tropical wave will move across
the region Thursday. The combination of these features, with
daytime heating and local effects will result in high chances for
showers and thunderstorms across the local islands during most of
the period.

&&

.AVIATION...VFR conds are expected to prevail at all TAF sites
through the early morning hours. However, as a tropical wave moves
over the Leeward Islands, brief MVFR conds are possible at TKPK/TNCM
late this morning as well as into the afternoon hours. Aft 22/16z
SHRA/TSRA expected near JMZ/JBQ with MVFR conds possible through
22/22z. Easterly winds 10-15 knots aft 22/13z with some sea breeze
variations.

&&

.MARINE...Seas up to 6 feet and winds up to 20 knots are expected
to prevail across the local waters. Small craft should exercise
caution across the offshore Atlantic waters.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 90 81 / 30 40 50 20
STT 90 80 89 81 / 50 60 60 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
308 PM AST Sat Jul 22 2017

.SYNOPSIS...A tropical wave with good moisture will move through
the area early tonight followed by drier air Sunday and Monday.
Moisture wrapping around a high pressure will reach the area on
Tuesday. A second tropical wave will follow on Thursday and better
moisture will follow it. Moisture tapers off slightly over the
following weekend.

&&

.SHORT TERM...Tonight through Tuesday
Winds shifted shortly after noon from a prevailing northeast flow
to an east southeast flow suggesting that the tropical wave or a
weaker trough may have passed through the area. The MIMIC product
shows the best moisture hanging back at about 61.5 degrees west as
of 22/13Z and present calculations suggest that it should cross
Saint Thomas at 23/05Z and San Juan at about 23/09Z--or earlier,
since there are indications that it is accelerating somewhat.
Currently tops have exceeded 50kft in western Puerto Rico, but
convection has been weaker in eastern Puerto Rico. Better rainfall
is expected overnight but it will likely be confined to the
southeast third of Puerto Rico with scattered showers around the
U.S. Virgin Islands.

With east to east southeast flow and a definite drop in
columnar moisture the first half of Sunday, maximum temperatures
should again broach the 90s on most of the north coast. Limited
moisture to counteract this heating on the south coast may also
allow high temperatures to resist the sea breezes and be
predominantly in the lower 90s. Monday will continue this trend.

Early Tuesday morning moisture arrives from the northeast that had
traveled around a high pressure north of the area and by Tuesday
afternoon precipitable water will be close to 2 inches again. This
will begin a wetter trend.


.LONG TERM...Wednesday through Saturday
Areas of moisture with a few dry slots move through the area
through Saturday on mostly easterly low level flow that will
sustain our seasonal summer pattern of showers and thunderstorms
each day. First around the U.S. Virgin Islands in the early
mornings and into eastern Puerto Rico, and then in the western and
interior portions of the Puerto Rico during the afternoons. No
strong features are currently seen in the models through the end
of July, but seasonal showers and thunderstorms often do produce
urban and small stream flooding in the afternoons.

&&

.AVIATION...SHRA/TSRA expected to continue over PR this afternoon
until around 22/22Z. This will cause VCSH or VCTS near the
terminals in PR. VCSH is expected for the remaining local
terminals as SHRA move in with the tropical wave that is bringing
plenty of moisture. Winds will continue from the east at about
10-15KT with higher gusts this afternoon, then decrease overnight
to around 10KT. Overnight weather will likely cause VCSH across
the local terminals except for TJMZ Limited MVFR and mtn
obscurations will likely continue through at least 23/16Z. Winds
alf easterly 10-20 kt up thru FL320 becmg easterly at all levels
by 24/00z. Winds strongest blo FL100.

&&

.MARINE...Seasonally tranquil seas of 5 feet or less are expected
in most of the local waters through the end of July. Small craft
advisories are not expected to be issued this month under the
current forecast. But winds up to 20 knots are possible in exposed
waters and small craft will need to exercise caution.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 79 90 81 90 / 40 50 20 20
STT 80 89 81 90 / 60 60 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
510 AM AST Sun Jul 23 2017

.SYNOPSIS...Lingering moisture associated with a departing
tropical wave will prevail early this morning followed by a
drier air mass moving into the forecast area. The proximity
of an upper level trough will assure shower and thunder
development each afternoon Tuesday through the upcoming
weekend.

&&

.SHORT TERM...Sunday through Tuesday...

Although a tropical wave continues to move farther away and
a drier mass will encompass the forecast area; the chance for
shower and thunderstorm development remains possible across the
local islands today.

As a drier mass encompass the local islands, mostly fair weather
conditions as well as an increase in Saharan dust particulate are
expected across the forecast area. However, lingering low-level
moisture combined with the local and diurnal effects will result
in the development of showers and thunderstorms across the interior
and western PR, as well as over the San Juan Metropolitan area
within the San Juan streamer in the afternoon. Limited shower
activity expected Monday and early Tuesday.

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

Weak ridge pattern aloft is expected to erode by Thursday as a
mid to upper level trough which is now located across the central
Atlantic shifts westward. The aforementioned through is expected
to prevail north of the local islands through the upcoming weekend.
The proximity of this feature combined with precipitable water
values near or slightly above the normal range will assure afternoon
showers and thunderstorms across the interior and west sections
of Puerto Rico each day. A broad surface high pressure across the
central Atlantic will yield east southeast winds through the
forecast period to result in above normal temperatures particularly
across the northern slopes of Puerto Rico.

&&

.AVIATION...Mainly VFR conditions expected to prevail across all
terminals. However, brief RA/VCSH periods possible at times
through 12z across the USVI/Eastern PR terminals. SHRA/TSRA
possible between 16z-22z across the northwest sections of PR,
impacting mainly TJBQ/TJMZ. Low level winds expected to prevail
ESE at 8-15 kts with sea breeze variations after 14z.

&&

.MARINE...Tranquil marine conditions are expected to prevail
during the next several days with seas 3 to 5 feet and easterly
winds 15 to 20 knots.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 81 89 81 / 30 10 10 30
STT 90 79 90 79 / 30 10 20 40

[cycloneye]

000
FXCA62 TJSJ 232011
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
411 PM AST Sun Jul 23 2017

.SYNOPSIS...Dry air is following the tropical wave which is now
departing the area. Moisture will return to the area overnight
Monday. A weak tropical wave will pass through on Wednesday to
continue the showers and isolated thunderstorms. Then, areas of
moisture will continue moving through the area into next weekend.
No major weather features are expected in the next 7 days.

&&

.SHORT TERM...Tonight through Wednesday.
High pressure remains across the central Atlantic while low
pressure holds in the southwest Caribbean driving moderate to
fresh easterly trade winds across the area through the period. A
tropical wave passed through the area overnight and is now
breaking over Hispaniola. Drier air is following and is already
evident from the shower activity which grew over west and central
Puerto Rico but is now dissipating, except for one area over
Utuado, Hatillo and Camuy as of 3:30 PM AST. Only broken streamers
were seen east of there off of Saint Croix and Saint Thomas and
these should be gone before sunset. The driest air and the driest
day will occur Monday though some showers and thunderstorms will
occur over western Puerto Rico during the maximum heating of the
afternoon. By Tuesday afternoon moisture from the east northeast
will have moved into the area to raise precipitable water values
to almost 2 inches again. A tropical wave will move into this area
of moisture on Wednesday. This will create showery conditions
both Tuesday and Wednesday, with the possibility of urban and
small stream flooding--mainly in western Puerto Rico both days.
Although moisture will rise in the U.S. Virgin Islands, flooding
is unlikely there, as this moisture and the wave invading it will
be of no great strength.

.LONG TERM...Thursday through Sunday
Areas of moisture and patches of drier air will pass thorough the
local area in the southeasterly flow behind the tropical wave
Wednesday night through Saturday. A ridge over the weekend will
bring dry air and patches of moisture to continue a pattern of
scattered showers. Northerly flow over the area at upper levels
will be light Thursday through Sunday as a TUTT low migrates to
the west, north of the area, at around 25 north latitude.
Although flow will be cyclonic, little divergence during the
period will exist to aid the formation of the seasonal showers
and thunderstorms expected to form each day in western and central
Puerto Rico. Nevertheless, they will be able to generate locally
heavy rain capable of producing urban and small stream flooding.
The U.S. Virgin Islands will have streamers each afternoon and a
few passing showers during the nighttime hours, but no major
features are expected across the area for the rest of this month.

&&

.AVIATION...Saharan dust is moving in and it is causing some haze,
but visibilities will be P6SM. VFR conds are expected across the
local terminals with VCSH possible this afternoon. VCTS at TJBQ
and TJMZ should end by 23/21Z. Winds from the ESE with sea breeze
variations this afternoon at about 10 to 15 kt with occasional
gusts, decreasing overnight to 10kt or less but continuing from
the east. Winds alf easterly 15 to 20 knots up to FL280.


&&

.MARINE...A wind surge--strongest in the Caribbean--will cause
seas to reach 6 feet in some areas Monday through Tuesday.
Otherwise seas should remain below 6 feet. Small craft advisories
are not expected in the local waters through the end of July.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 79 89 81 89 / 10 10 40 40
STT 79 90 79 89 / 10 20 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
454 AM AST Mon Jul 24 2017

.SYNOPSIS...Drier and more stable air mass is forecast today as
Saharan Dust particles spread over the Northeast Caribbean. As a
result...limited shower activity is anticipated today. Moisture
content will increase Tuesday and Wednesday as a tropical wave
approaches from the east and an upper level trough retrogress
across the Western Atlantic.

&&

.SHORT TERM...Monday through Wednesday...

Ridge pattern aloft will continue to erode through the forecast
period as TUTT low which is now located across the central Atlantic
shifts westward and relocates north of the local islands. This
feature will then promote moisture advection from the east northeast
on Tuesday. The next tropical wave passage is expected on Wednesday
with bulk of moisture remaining south of the area. Therefore, under
weakening ridge and moisture near or slightly above the normal range
which is 1.75 inches, expect trade wind showers across USVI and E PR
at times as well as afternoon showers and thunderstorms across the
interior and west sections of Puerto Rico Tue-Wed.

Meanwhile for today, expect a fair weather pattern with hazy skies
and warm to hot temperatures. Showers if any will be focused across
Mayaguez and vicinity.

.LONG TERM...Thursday through Sunday

Upper level trough/TUTT northeast of the region will be the dominant
weather feature Thursday and Friday...dissipating as it moves
northward during the weekend. The proximity of the TUTT combined
with slightly above normal moisture will enhance somewhat the
afternoon showers and thunderstorms each afternoon. In addition...
bands of low level moisture embedded in the trade winds will
bring light showers over the U.S. Virgin Islands and Eastern
Puerto Rico especially at night and early in the morning. After
the wave passage on Wednesday, southeasterly flow will establish
across the Northeast Caribbean Region leading to above normal
temperature once again across the northern half of Puerto Rico the
second part of the week. Operational models suggest breezy and
more stable conditions for early next week.

&&

.AVIATION...VFR conds are expected to prevail at all TAF sites
through the forecast period. However, Aft 24/16z SHRA expected to
develop near JMZ with MVFR conds possible through 24/22z. Easterly
winds 10-15 knots aft 24/13z with some sea breeze variations.
Although hazy skies are expected to prevail across the forecast
area, visibilities expected to remain P6SM.

&&

.MARINE...Fresh winds of 15-20 kts will create wind waves of 4-6 feet
across the regional waters today. Therefore...Small craft should
exercise caution across the coastal waters of Puerto Rico through
tonight. Winds will subside to 10-15 kts the rest of the week giving
way to typical seas of 3-5 feet over the next several days.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
505 AM AST Tue Jul 25 2017

.SYNOPSIS...Ridge aloft will continue to erode as a TUTT low
which is now located across the central Atlantic shifts westward
and relocates northeast of the area. A broad surface high will
continue to hold across the central Atlantic. There is a tropical
wave east of the Lesser Antilles which is expected to move across
the Caribbean waters Wednesday.

&&

.SHORT TERM...Tuesday through Thursday...

A humid air mass displaced the dry air mass with Saharan Dust
Particles. This patch of moisture brought showers and clouds across
the islands overnight. Under a northeasterly wind flow, shower
activity is expected to continue into the morning hours mainly
across the surrounding waters and the windward sections of the
U.S. Virgin Islands and Puerto Rico. Afternoon convection is
expected across the interior and southwestern sections of Puerto
Rico. As a result, ponding of water in roads and low lying areas
as well as urban flooding are possible this afternoon.

Moisture pooling will continue as a tropical wave is forecast to
move across the islands Wednesday. Also, instability is forecast
to increase due to the proximity of an upper level trough/ TUTT
low, which combined with a drop in the regional winds, diurnal
heating and local effects will provide a favorable environment for
the development of T-storms and showers during the afternoon hours.
Under a humid environment, the typical showers are expected to
continue each night and early morning.

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

A weak mid level ridge is expected to hold across the forecast
area Saturday through Wednesday. At lower levels, a broad high
pressure across the central Atlantic will yield east to east
southeast winds through the forecast period. Precipitable water
is expected to remain near the normal range which is 1.75 inches
Friday through at least late Monday. As an easterly disturbance
moves across the eastern Caribbean on Tuesday, deep tropical
moisture is expected to reach the local islands. However, deep
tropical moisture across the area will be short-lived as a drier
air mass moves into the forecast area on Wednesday.

Therefore under the lack of upper level forcing and moisture
content near the normal range; continue to expect a seasonable
weather pattern with trade wind showers across the USVI and E PR
at times, as well as showers and thunderstorms developing across
west sections of Puerto Rico each afternoon. At this time, the
day with the highest chance for showers and thunderstorms is
Tuesday associated with the disturbance moving across the area.

&&

.AVIATION...VFR conds expected through 25/16Z. Winds will
continue to be from the East to ESE for the rest of today with
sea breeze variations at about 15KT with occasional gusts. VCSH
possible at TJMZ between 25/18Z and 25/22Z. Some SHRA/TSRA
possible around TJMZ after 25/16Z.

&&

.MARINE...Tranquil marine conditions will continue to prevail
across the forecast area with seas 3 to 5 feet and occasional
seas up to 6 feet. Winds 15 to 20 knots to continue.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
530 AM AST Wed Jul 26 2017

SYNOPSIS...TUTT low northeast of the area will prevail through
the end of the workweek. As this feature weakens Friday and into
the upcoming weekend, a weak mid level ridge will build in and
hold through much of the next week. A broad surface high pressure
Will continue to hold through the forecast period. A tropical
wave will continue to move across the area today, increasing the
chance for showers and thunderstorms.

&&

.SHORT TERM...Wednesday through Friday...

A tropical wave brought showers across the local waters, the
northern U.S. Virgin Islands and East Puerto Rico. Little or no
shower activity was detected over the interior sections of Puerto
Rico and St Croix overnight. As tropical moisture pools over the
islands, shower activity is expected to continue across these
areas through the morning hours. Some moderate to heavy rainfall
is possible with this activity and commuters can expect ponding
of water on roads and in low lying areas.

Showers and thunderstorms are expected along and to the northwest of
the Cordillera Central during the afternoon hours. Periods of
moderate to heavy rainfall are expected across these areas. Also,
model guidance continues to indicate favorable conditions for
strong thunderstorms. In addition, winds are expected to shift
from the east-southeast increasing the potential for showers and
thunderstorms in the form of streamers into the San Juan Metro
Area. Across the U.S. Virgin Islands, showers are expected to
form mainly downwind from the islands. Shower activity, on the
other hand, is expected to be limited across the south coast of
Puerto Rico.

As the tropical wave exits the area, a dry air mass is expected
to reach the islands resulting in mostly clear skies but with
Saharan dust particles, as the model guidance is indicating.
Another tropical wave is forecast to reach the islands on Friday.
At this time, moisture seem to be less abundant on Friday, but
showers and thunderstorms are still expected to form across most
of the islands.

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

A weak mid level ridge is expected to hold across the area through
the forecast period. At lower levels, a broad high pressure across
the central Atlantic will continue to prevail, resulting in east to
east southeast winds through Tuesday. Precipitable water is expected
to remain near the normal range which is 1.75 inches Saturday through
early next workweek. Moisture advection is expected by midweek as an
easterly disturbance moves across the area. Therefore, under the
lack of upper level forcing and moisture content near the normal
range; continue to expect a seasonable weather pattern with trade
wind showers across the USVI and E PR at times, as well as showers
and thunderstorms developing across west sections of Puerto Rico
in the afternoon. The highest chance for widespread shower activity
with thunderstorms looks possible at the end of the forecast
period.

&&

.AVIATION...SHRA are expected to continue across the Flying area
as a tropical wave moves through the region. SHRA/TSRA are
expected to develop across the interior and NW quadrant of PR as
well as downwind from El Yunque. As a result, VFR or even IFR
conditions are possible aft 26/15z across TJBQ/TJSJ. SHRA/TSRA are
possible in the VCTY of TIST/TISX/TJPS. Wx conds will improve aft
26/23z. Calm to light/VRB winds increasing at 10 to 15 kt with
higher gusts in and near SHRA/TSRA aft 26/14z.

&&

.MARINE...Tranquil marine conditions will continue to prevail
across the forecast area with seas 3 to 5 feet and occasional
seas up to 6 feet. Winds 10 to 15 knots to continue. Passing
tropical wave will continue to bring periods of showers and
isolated thunderstorms across the local waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 80 90 80 / 50 30 30 20
STT 89 80 90 80 / 50 60 30 30