Caribbean - Central America Weather

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cycloneye
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Re: Caribbean - Central America Weather

#19361 Postby cycloneye » Mon Apr 16, 2018 5:49 am

Area Forecast Discussion
National Weather Service San Juan PR
538 AM AST Mon Apr 16 2018

.SYNOPSIS...Shallow marine moisture and brief passing showers will
be augmented by better moisture on Wednesday and Thursday with a
weak low-level trough passage late Tuesday. The cold front that
left Florida last night will not be able to reach the local area
before it is forced to retreat on Wednesday.

&&

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

An easterly perturbation and associated low level moisture just
east of Guadeloupe will enter the eastern Caribbean during the
next day or so. A cold front entering the western Atlantic is
forecast to remain well to the north of the region as a broad
surface high pressure builds over the east central Atlantic by
midweek. PWAT content is expected to increase from 1.45 inches
today to 1.8 inches by Wednesday evening. East to southeast
steering winds will prevail each day between 10-15 kts. Diurnally
induced afternoon showers and isolated thunderstorms are expected
to develop each day...mainly over the northwest quadrant of Puerto
Rico. Streamers are also expected to develop across the USVI and
over the San Juan metro area from the eastern mountains. Localized
urban and small stream flooding is expected with this activity
each afternoon but mainly in western Puerto Rico. An upper level
trough is expected to enhance convective development over the
region by Wednesday. This trough and the expected increase in
moisture will favor the development of scattered to numerous
showers and thunderstorms across portions of the local waters and
the islands.

.LONG TERM...Thursday through Monday

The conditions bringing the showers and thunderstorms to most
areas of the islands Wednesday will increase slightly and reach a
maximum of Thursday. Most indicators including precipitable water
(PWAT) and the GDFI (Galvez-Davidson Index) will favor the best
chance of thunderstorms and heavier showers on Thursday. This
would also be the day of the most widespread urban and small
stream flooding though, even then, it should be localized to the
most favored areas. On Friday and Saturday the divergence aloft is
no longer favorable and the jet moves east with the passage of a
weak shortwave trough on Saturday. Moisture diminishes after
Saturday as winds at 700 mb turn northeasterly and even surface
flow becomes a little north of east. Precipitable water values
return to those of yesterday or between 1.2 and 1.5 inches for
the rest of the period. This will yield scattered showers
overnight on the windward slopes and coasts and isolated
thunderstorms in the west and interior during the afternoons, but
there should be little more than that until Tuesday of next week.


&&

.AVIATION...Mainly VFR conditions expected to prevail across all
terminals through 16z. However, passing shra could move at times
across TNCM/TKPK/TIST/TISX through the day, causing brief MVFR cigs.
Across the PR terminals, shra/tsra is expected btw 17z-23z across
the NW portions of PR, impacting mainly TJBQ/TJMZ with mtn
obscurations and tempo MVFR conds. ESE winds expected at 10-20
kts blo FL100 with sea breeze variations at the sfc after 14z.
Maximum winds NNW 50-65 kt btwn FL320-470 strongest at FL400 at
16/12Z.

&&

.MARINE...Seas are gradually subsiding with the winds and all
small craft advisories should come down by 2 PM AST this
afternoon. Rip current risk will remain moderate and small craft
will need to exercise caution in some waters. Seven foot seas are
forecast to return to the local outer Atlantic waters by Thursday
afternoon but for no more than 24 hours.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 74 87 75 / 50 40 40 40
STT 85 76 86 76 / 40 40 40 50
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Re: Caribbean - Central America Weather

#19362 Postby cycloneye » Mon Apr 16, 2018 4:56 pm

Area Forecast Discussion
National Weather Service San Juan PR
451 PM AST Mon Apr 16 2018

.SYNOPSIS...An increase in low level moisture is expected
Wednesday and Thursday across the local islands. Moderate to fresh
trade winds will continue to dominate the local region through the
end of the work week.

&&

.SHORT TERM...Tonight through Wednesday...Partly cloudy skies
prevailed across Puerto Rico and the U.S. Virgin Islands late this
morning. Some showers were observed across the eastern section of
Puerto Rico. Low level moisture, combined with daytime heating
and orographic effects produced scattered showers with
thunderstorms across the western interior and northwest sections
of Puerto Rico. In addition, a streamer developed and extended
towards the San Juan metropolitan area, through toa Baja and
Dorado. The heaviest rainfall occured in Bayamon and Toa Baja were
rainfall estimates were between two to three inches in localized
areas.

For tonight, most of this activity is expected to dissipated.
Partly cloudy skies are expected across the local islands. For
Tuesday, A slightly drier air mass is expected to encompass the
region. However, low level moisture will be good enough to
enhance the development of showers and thunderstorms once again,
mainly across the western interior and northwest sections of
Puerto Rico.

By Wednesday, an easterly perturbation is expected to move across
the region. A sharp increase in low level moisture is then
expected, which will enhance the development of showers and
thunderstorms. Wednesday`s activity is expected to be more
widespread, affecting most of the local area.

.LONG TERM...Thursday through Monday...The easterly perturbation
will continue to affect the local region Thursday. By Friday, a
slot of dry air is expected to encompass the region. For the
weekend and beyond, no significant weather events are forecast to
affect the local region.

&&

.AVIATION...SHRA/TSRA expected to develop thereafter. TJMZ and TJBQ
may have moments of MVFR conds with the afternoon convection. TJSJ
could have VCSH as well as TJPS. Winds will be mainly from the east
at 10-15KT and gusty with sea breeze variations. Winds to decrease
after 16/22Z and weather to improve thereafter as well. THe local
winds will increase to 10-15KT after 17/13Z.

&&

.MARINE...Seas up to 6 feet and winds up to 20 knots are expected
to continue across the local waters through at least Wednesday.
Small craft should exercise caution across most local waters.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 74 87 75 86 / 40 40 40 70
STT 76 86 76 85 / 40 40 50 50
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Re: Caribbean - Central America Weather

#19363 Postby cycloneye » Tue Apr 17, 2018 5:17 am

Area Forecast Discussion
National Weather Service San Juan PR
508 AM AST Tue Apr 17 2018

.SYNOPSIS...Moisture will increase through Thursday. This afternoon
a weak easterly wave will move through followed by showers and
thunderstorms with help from upper levels Wednesday and Thursday.
Drying will occur on Friday and Sunday but showers will be active
through the weekend in mostly east flow.

&&

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

Showers persisted during the overnight hours across portions of
eastern and southern Puerto Rico. Up to a quarter of an inch of rain
was observed with these showers. Early morning passing showers will
continue to move across the islands at times . Diurnally induced
afternoon showers and thunderstorms are expected this afternoon
over the interior and northwestern sections of Puerto Rico.
Streamers are also expected to develop across the USVI and over
the San Juan metro area from the eastern mountains. Urban and
small stream flooding is expected with this activity. A wet
pattern is then expected on Wednesday and Thursday as an easterly
perturbation moves across the forecast area. Scattered to numerous
showers and thunderstorms are expected to develop over the
Caribbean waters and across the USVI and Puerto Rico during this
period.

.LONG TERM...Friday through Tuesday
After the wettest period of the week, a brief drying period will
occur on Friday although residual low-level moisture will keep at
least scattered showers in western and interior Puerto Rico.
Weaker upper level trough passage and the presence of a jet on
Friday will also favor showers and thunderstorms on Friday even
though moisture is greatly reduced above 850 mb. A patch of
moisture will move in Saturday to make up for much of the support
that will be lost during the day at upper levels. Then moisture
will subside again Sunday and shower activity will diminish.
Another upper level trough will move through on Sunday night that
may cause showers to linger later in the evening than on previous
days. Moisture and southeasterly flow returns on Monday and
Tuesday with another shortwave passage currently forecast for
Monday night. Although no major features are foreseen moisture
does increase into the rest of next week.

&&

.AVIATION...Mainly VFR conditions expected to prevail across the
USVI/PR terminals through at least 16z. SHRA/TSRA are expected
from 17z-23z across interior and western PR, impacting mainly
TJBQ/TJMZ with MVFR conditions. RA/VCSH at TJSJ and mtn obscd early
this afternoon. MVFR possible at times today at TNCM/TKPK due to
SHRA/TSRA. ESE winds expected at 10- 20 kts blo FL100 with sea
breeze variations at the sfc after 14z. Maximum winds NW 25-34 kt
btwn FL270-520 diminishing thru 18/00Z.

&&

.MARINE...Seas will subside slowly through Wednesday evening.
Another long period northeast swell will arrive then and the outer
portion of the local outer Atlantic waters will likely require a
small craft advisory Thursday. Current forecasts call for seas
less than 7 feet into next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 87 74 / 50 50 70 70
STT 86 75 84 76 / 50 70 70 70
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Re: Caribbean - Central America Weather

#19364 Postby cycloneye » Tue Apr 17, 2018 6:40 am

a vigorous upper trough moving across the eastern
Caribbean into the tropical Atlantic was supporting areas of
heavy showers and a few thunderstorms across the northern Windward
Islands late yesterday. An earlier scatterometer satellite pass
indicated fresh to strong easterly winds between Saint Vincent and
Martinique. Media sources on Martinique reported small hail
Monday in scattered thunderstorms from this disturbance. An
associated surface trough west of the Lesser Antilles and
diffluent flow aloft from the upper trough is continuing to
enhance clouds and showers in the Windward Islands. Gusty winds
and higher seas are possible near these thunderstorms through
early morning as the supporting upper trough shifts slowly east of
the area. Meanwhile, NE to E swell to 8 ft is still present in
the tropical Atlantic waters east of the Windward Islands.
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Re: Caribbean - Central America Weather

#19365 Postby cycloneye » Wed Apr 18, 2018 7:02 am

Area Forecast Discussion
National Weather Service San Juan PR
536 AM AST Wed Apr 18 2018

.SYNOPSIS...A surface trough will move across the region today.
Showers with periods of heavy rainfall and thunderstorms are
expected today and on Thursday afternoon. Drier mid levels are
expected Friday through early next week. However, diurnally
induced afternoon showers with possible isolated thunderstorms are
expected each day across western PR. Elsewhere, passing showers
and light rainfall amounts are expected.


&&

.SHORT TERM...Today through Friday...
A weak trough is over Puerto Rico and moisture behind it is spawning
SHRA mainly over Atlantic waters, and, earlier, pockets of TSRA
south southwest of Ponce and east of the Leeward Islands. Showers
are moving northwest in the low level flow. The MIMIC product shows
better moisture crossing the Leeward Islands and is expected to ride
into Puerto Rico and the U.S. Virgin Islands by the time of maximum
heating. Right now these areas have mostly clear skies overhead and
upstream, but clouds and showers are expected to develop during the
day. The best chances for rain will be in the west and interior
portions of Puerto Rico but showers over the local waters are more
likely than yesterday. A weak jet will pass north of Puerto Rico
today and tomorrow ahead of an eastward moving upper level trough
that will pass on Friday. Some general support is therefore expected
from the divergence aloft today. Moisture will also continue to
increase during the day while 500 mb temperatures remain low (less
than minus 8 C) and lifted indices will fall to minus 6. This will
support isolated to scattered thunderstorms and local urban and
small stream flooding in the west, (generally north of the
Cordillera Central) and the interior portions of Puerto Rico. A
streamer off of the high points of the Luquillo range is also
possible and will be the main source for heavy rainfall in the
greater San Juan and Bayamon Metropolitan Areas. Moisture continues
overnight and showers will be slow to move out of the area. However
dry air will be edging into the USVI by 19/18Z and into Puerto Rico
by 20/00Z and showers will diminish dramatically. This drier air
will move through in about 24 hours and by Friday afternoon there
should be enough moisture to bring scattered showers, isolated
thunderstorms and localized urban and small stream flooding to
western and interior Puerto Rico as well as scattered showers to
areas southeast of the main islands, including Saint Croix.

Dynamics will be better on Thursday so areas of urban and small
stream flooding should be greater and more intense Thursday. Friday
will be similar or slightly weaker than Wednesday for much the same
reason as well as the steep decline in moisture at all but the
lowest levels of the atmosphere.

.LONG TERM...Saturday through Wednesday...
A broad surface high pressure will continue across the eastern
Atlantic promoting moderate trades. Drier mid level air is
expected to prevail during the long term period. However, a
typical weather pattern will prevail each day with afternoon
convection developing over the western interior sections of Puerto
Rico and streamers forming off the smaller islands. A short wave
trough will move close on Sunday, enhancing shower and
thunderstorm development during the afternoon and some showers
will linger through the evening hours across portions of western
coastal waters.

&&

.AVIATION...Moisture behind a weak trop wave will bring SHRA and
Isold TSRA. VFR conds to cont til arnd 18/15Z xcp arnd TNCM/TKPK
where ocnl MVFR CIGS are psbl. Aft 16Z MVFR CIGs psbl TIST/TISX in
SHRA til aft 19/06Z. Aft 18/15Z areas of SHRA/iso-sct TSRA will dvlp
mainly across wrn and interior PR with mtn obscurations. Sfc winds
ESE 10-15 kt with sea/land breeze variations. Max winds W 50-60 kt
btwn FL350-430 by 18/18Z.


&&

.MARINE...A long period northeasterly swell will move across the
local waters on Thursday. This will cause seas to increase around
7 feet mainly across the offshore Atlantic waters and the Anegada
Passage. Therefore, small craft advisories will be in effect.
Also, life threatening rip currents are expected along the
Atlantic beaches of Puerto Rico and portions of the southern coast
of the island as well across St. Croix. Meanwhile seas will
continue to range between 3-6 feet today and winds will prevail
from the east to southeast at 10-15 knots.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 74 86 75 / 70 70 40 20
STT 84 76 85 75 / 70 70 20 10
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