Caribbean - Central America Weather

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cycloneye
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Re: Caribbean - Central America Weather

#18721 Postby cycloneye » Sun Mar 19, 2017 5:25 am

Area Forecast Discussion
National Weather Service San Juan PR
516 AM AST Sun Mar 19 2017

.SYNOPSIS...Increasing moisture, the presence of a cold front to
our north, a subtropical jetstream that holds just to our north
leaving us under favorable upper level dynamics will all
contribute to an increasingly wet scenario for Puerto Rico and the
U.S. Virgin Islands. Rainfall amounts should be highest on
Saturday, but rain is expected in many areas both early and late
in the week.

.SHORT TERM...Today thru Tuesday...
For the rest of the overnight and early morning hours, passing
showers with brief gusty winds can be expected across the local
waters, as well as along portions of the north and east coastal
sections of the islands. During the afternoon hours, the
prevailing east southeast winds should steer diurnally induced
shower activity across the interior and northern half of Puerto
Rico including portions of the San Juan Metro area. Some areas of
heavy rainfall will also be possible in the northwest. Mainly
isolated showers are expected across the U.S virgin islands during
the afternoon.

The mid to upper level ridge will continue to erode as a broad
polar trough will become amplified and move eastward across the
west and central Atlantic through Tuesday. The subtropical jet
will round the base of this trough Monday through Tuesday placing
the region on the divergent and unstable side of the jet max.
Gradually increasing pooling of moisture and low level convergence
is still forecast beginning later this evening through the early
part of the upcoming week. This is in response to the frontal
boundary northwest of the region and an associated induced trough
which will develop and lift across the region Monday through
Tuesday. This overall pattern will result in the easterly winds
becoming more south southeasterly by Monday, then east southeast
once again on Tuesday. Weather conditions will become fairly moist
and unstable on Monday through Tuesday, with favorable conditions
aloft for increased shower activity and enhanced convective
development across the forecast area.

&&

.LONG TERM...Wednesday through Monday 27 March
On Wednesday a weak high pressure ridge will be found in place
enabling easterly trade winds of moderate to fresh intensity to
continue. That ridge will give way before a strong high pressure
moving out of the eastern United States late Thursday. It will
give another push to the front to our northwest and reinvigorate
the easterly trade winds again through the upcoming weekend. This
will maintain the flow of moisture over the area. An upper level
trough will move from Cuba on Wednesday to just north of Puerto
Rico on Sunday but will flatten out considerably as it does so.
The associated sub-tropical jet just north of us will remain
north of us during the entire period but will destabilize the
atmosphere around us on account of our being in the divergent
right entrance region. Moisture will have peaked on Tuesday but
diminishes only a little on Wednesday and Thursday and will rise
considerably late Thursday and early Friday due to the moisture
flow mentioned earlier. The GFS has been consistent in bringing
precipitable water with values of 1.8 to 2.0 inches early Friday
through beyond Monday of the following week. This will bring a
considerable amount of rain to the area should the forecast hold.
It is too early to determine if conditions are conducive for flash
flooding but localized urban and small stream flooding are
certainly possible with the forecast conditions. We continue with
isolated thunderstorms during the week as the inversion is
expected to be removed by Wednesday. The atmosphere becomes very
moist in nearly the entire column beginning Thursday and cloudy or
mostly cloudy conditions should prevail into early next week.

&&

.AVIATION...Mostly VFR conds at all terminals til 19/15Z. SFC
wnds lgt/vrb becmg E-SE 10-15 kts aft 19/14z...except for local
sea breeze variations. Til 19/15z...Isold to Sct passing SHRA ovr
the coastal waters btwn PR and the nrn Leewards islands...SCT-BKN
lyrs nr FL025...FL050... FL100...with VCSH at most of the local
terminals except TJMZ. Mtn top obscr ovr E PR til 19/14z. Fm
19/17z-19/22z... SHRA dvlpmnt psbl ovr ctrl mtn range and NW PR
with VCSH at TJBQ/TJMZ/TJSJ with MVFR psbl.


&&

.MARINE...Winds and seas are diminishing and all small craft
advisories should be down by 2 AM AST Monday. The system now in
the western Atlantic and its associated cold front will send
northerly swell into the area on Wednesday. Seas may reach 7 feet
in the Atlantic waters and passages. Then the newly refreshed cold
front to our north will begin to send much stronger swell into
the area Friday night. Seas of 10 feet or more are still possible
with this system.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 73 85 75 / 30 40 50 50
STT 83 73 82 72 / 50 50 50 50

&&
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Re: Caribbean - Central America Weather

#18722 Postby cycloneye » Sun Mar 19, 2017 2:48 pm

Area Forecast Discussion
National Weather Service San Juan PR
345 PM AST Sun Mar 19 2017

.SYNOPSIS...The chance for showers and thunderstorms are still
expected to increase this week under plenty of moisture and
favorable upper level dynamics.

&&

.SHORT TERM...Tonight thru Wed Morning...

Moisture will continue to pool across the local islands Mon-Tue
as a surface front and associated prefrontal trough approaches
the forecast area. This feature will also result in winds shifting
south southeast by Mon, becoming more east southeast on Tue.
Therefore,the chance for showers and isolated thunderstorms will
increase across the forecast area with passing showers expected to
prevail across the USVI and eastern Puerto Rico. Shower activity
and locally induced thunderstorms are also expected across the
north and west sections of Puerto Rico each afternoon. As the
induced surface trough dissipates Tue into Wed. Moisture is expected
to erode somewhat across the eastern Caribbean. Although the same
weather pattern is expected with showers across the USVI and E PR
in the morning followed by showers with isolated thunderstorms
across west PR in the afternoon, intensity and areal coverage
should decrease.

.LONG TERM...Wed Night thru Day 8 /issued 516 AM AST Sun Mar 19 2017

A sub-tropical jet will remain north of area during the entire
period, destabilizing the atmosphere around us. Moisture will also
rise considerably late Thursday and early Friday. In fact, the GFS
has been consistent in bringing precipitable water with values of
1.8 to 2.0 inches early Friday through beyond Monday of the following
week. This will bring a considerable amount of rain to the area
if the forecast holds. It is too early to determine if conditions
are conducive for flash flooding but localized urban and small
stream flooding are certainly possible with the forecast conditions.

&&

.AVIATION...Mostly VFR conditions expected across the local flying
area overnight with VCSH across the Leeward, USVI and TJSJ taf
sites. Latest TJSJ sounding indicated an east southeast wind flow
from the SFC to around 6K feet, becoming light and variable between
6-20K feet and then westerly and stronger aloft. Until 19/22z...SHRA
will develop over central mountain range and NW PR with possible
MVFR conditions over TJBQ and TJMZ and TJSJ. Shower activity will
decrease after 19/22Z.

&&

.MARINE...Winds and seas will continue to diminish tonight. However,
a northerly swell will reach the area by Wednesday with seas up
to 7 feet expected across the offshore Atlantic waters. A cold
front to our north will begin to send much stronger swell into the
area Friday night. A high risk of rip currents continues along
the Atlantic shoreline overnight, with a moderate risk expected
tomorrow.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 73 85 75 85 / 20 40 40 40
STT 73 82 72 84 / 50 50 50 50

&&
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Re: Caribbean - Central America Weather

#18723 Postby cycloneye » Mon Mar 20, 2017 5:23 am

Area Forecast Discussion
National Weather Service San Juan PR
320 AM AST Mon Mar 20 2017

.SHORT TERM...Monday thru Wed Morning... Localized low level moisture
convergence will continue across region through Tuesday in response
to approaching frontal boundary northwest of the area and associated
prefrontal trough which will move across the forecast area. This
weather pattern will create light and variable winds which are
expected to become more south southeast today, then east southeast
on Tuesday. The increasing moisture as suggested by recent PWAT
satellite analysis product and model guidance as well as instability
in the upper levels, all support better chance for showers and
possibly isolated thunderstorms today and Tuesday. Expect cloudiness
to increase across the region with periods of passing showers to
continue across the coastal waters and portions of the islands
during the early morning hours.

A brief break in cloud cover and shower activity is expected by late
morning, however sea breeze variations and diurnal effects will lead
to increasing cloudiness and afternoon convection across the
interior, north and west sections of PR. Favorable upper level
instability will support enhanced afternoon showers and isolated
thunderstorms. Expect periods of locally heavy rainfall with little
steering winds, so minor urban and small stream flooding will be
possible today and Tuesday. As the induced trough weakens late
Tuesday thru Wednesday, expect decreasing moisture convergence and
lesser chance for enhanced convection across the region.

.LONG TERM...Unstable conditions will continue through the end of
week as a sub- tropical jet will prevail to be north of the local
forecast area. A significant on moisture it is expected late
Thursday and early Friday. The GFS models suggest large amounts of
moisture across the region from Friday through at least Monday.


&&

.AVIATION...Mostly VFR conds durg prd ovr local flying area. SCT-BKN
lyrs nr FL025...FL050...BKN-OVC FL100 en route btw PR and Nrn
Leeward Islands with passing SHRA and Few tops nr FL120. Til 20/12z
tempo MVFR at TJNR/TJSJ/TIST/TISX with MTN Top obscr ovr E PR due to
low clds and passing SHRA. L/Lvl wnds lgt/vrb blo FL200 and mostly
calm at all terminals...bcmg lgt/vrb aft 20/14z except for local sea
breeze variations. Fm 20/17z-19/22z...incr low to mid lvl cld cover
with SHRA/psbl TSRA fcst to develop over central mountain range and
W PR with possible MVFR conditions ovr and vcty TJBQ/TJMZ/TJSJ.


&&

.MARINE...The high rip current risk is cancelled as winds and
seas continued to subside through the overnight hours. A northerly
swell will reach the area by Wednesday with seas up to 7 feet
across the offshore Atlantic waters. Another pulse of a larger
northerly swells will reach our local waters on Friday night.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 85 75 / 40 40 40 30
STT 82 72 84 74 / 50 60 60 50

&&
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Re: Caribbean - Central America Weather

#18724 Postby cycloneye » Mon Mar 20, 2017 3:07 pm

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
400 PM AST Mon Mar 20 2017

.SYNOPSIS....A wetter pattern is expected to prevail across the
local islands this week, particularly Friday and into the
upcoming weekend.

&&

.SHORT TERM...Tonight thru Thu Morning...

Moisture will continue to pool across the local islands through Tue
as an induced surface trough holds across the northeast Caribbean.
South southeast winds will prevail this afternoon and overnight
becoming more easterly Tue as this feature weakens. Under this
evolving pattern, the chance for showers and isolated thunderstorms
continues across the forecast area with passing showers expected
to prevail across the USVI and eastern Puerto Rico with locally
induced afternoon Tstorms over and north of the Cordillera and
Sierra de Luquillo.

.LONG TERM...Thu Night thru Day 8

Unstable condition are expected Thu night through early next week
as a sub-tropical jet remains north of the forecast area during
the entire period and close enough to destabilize the local atmosphere.
Moisture will also rise considerably late Thursday into early Friday.
Therefore, if the forecast holds, this will bring a considerable
amount of rain to the area late this week and early next week. It
is too early to determine if conditions are conducive for flash
flooding but localized urban and small stream flooding are
certainly possible with the forecast conditions.

&&

.AVIATION...VCSH will affect TJSJ, USVI and Leeward islands TAF sites
tonight. Latest TJSJ sounding indicated a very light and variable
wind flow from the SFC to around 13k feet, becoming westerly up to
70 knots aloft. SHRA will continue to develop over central mountain
range and western sections of Puerto Rico with periods of MVFR
conditions over TJMZ and possible over TJBQ until 20/22Z.

&&

.MARINE...Seas below 5 feet will continue to prevail across the
local waters through Tuesday. A northerly swell will reach the
area by Wednesday with seas up to 7 feet across the offshore
Atlantic waters. Another pulse of a larger northerly swells will
reach our local waters on Friday night.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 84 75 86 / 20 50 30 30
STT 72 84 74 84 / 60 60 40 40
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Re: Caribbean - Central America Weather

#18725 Postby cycloneye » Tue Mar 21, 2017 5:20 am

Area Forecast Discussion
National Weather Service San Juan PR
447 AM AST Tue Mar 21 2017

.SHORT TERM...Tuesday-Thursday...Overnight showers were mainly
observed over the Atlantic waters and over portions of eastern PR.
However, no significant rainfall accumulations were observed. It was
mostly clear across the USVI with temps in the low 70s across
coastal areas. An induced surface trough moving across the Caribbean
waters will enhance afternoon convection along the mountain ranges
of PR this afternoon. As soils are already saturated due to
yesterday`s rains, any period of heavy or prolonged rainfall across
the interior and north of the Cordillera will lead to urban and
small stream flooding. Upper level trough will weaken and associated
sfc front will linger across the Atlantic waters. Afternoon
streamers and passing showers are expected mainly across the USVI.

Forecast soundings are indicating light steering winds from the east-
southeast around 10 kts through Thursday. In addition, another mid
to upper level trough will move from the west late Wednesday into
Thursday enhancing upper level dynamics across the region. So any
additional afternoon shower development over land areas will continue
to pose a threat of at least urban and small stream flooding through
the short term period. Associated low level shearline is forecast
to enhance more moisture and favorable conditions for more rainfall
late in the week and into the weekend.

.LONG TERM...late Thursday-next Tuesday...High amplitude trough
is forecast to deepen and extend across the Greater Antilles into
the west and central Caribbean Thursday through Friday. This will
gradually increase instability aloft and enhanced upper level
divergence across the region. A subtropical jet max is forecast to
round the base of the upper trough and lift northeastward just
north of the forecast area. In the low levels, a broad inverted
surface trough will linger across the central and eastern
Caribbean. As a result, a moist southeasterly flow will persist
through Friday and into the weekend. Therefore a much wetter
pattern with enhanced tropical moisture advection is forecast for
the next several days. Good moisture convergence along the
approaching frontal boundary, and surface trough along with the
upper level instability will favor increased potential for
enhanced convection across the region through the weekend and at
least until Tuesday of next week. Thereafter winds are forecast to
become more northeasterly as surface high pressure ridge will
spread across the west Atlantic. Until then, expect periods of
late evening and overnight passing showers along portions of the
north and east coastal sections of the islands,followed by afternoon
convection with enhanced shower activity particularly across the
interior and northern half of Puerto Rico. The potential for periods
of locally heavy rainfall with minor urban and small stream flooding
in isolated areas will therefore remain high across portions of the
islands especially Puerto Rico.

&&

.AVIATION...Mostly VFR early in the forecast period across all
terminals. However, weak trough moving fm the Leeward islands into
the eastern Caribbean will create SCT-BKN cigs and enhance diurnal
convection across the islands in the afternoon. Therefore, tempo MVFR
conds possible mainly over mainland PR terminals between 16z-22z.
Low level winds will continue at 6-15 kts with sea breeze variations
after 14z.

&&

.MARINE...Seas generally 3 to 5 feet are expected overnight but increasing
gradually during the rest of today. Small craft advisory will go into
effect later tonight for the offshore Atlantic waters as seas will approach
7 feet due to increasing trade winds and a northerly swell reaching
the local waters. A larger northerly swell is still forecast to arrive
and spread across the Atlantic waters and local passages will by late
Friday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 74 86 75 / 30 30 30 20
STT 85 75 84 75 / 30 30 30 30
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Re: Caribbean - Central America Weather

#18726 Postby cycloneye » Tue Mar 21, 2017 3:19 pm

Area Forecast Discussion
National Weather Service San Juan PR
355 PM AST Tue Mar 21 2017

.SYNOPSIS...Environmental conditions are expected to become more
favorable and conducive to deep convection later in the week and
throughout the weekend.

&&

.SHORT TERM...Tonight thru Thu Morning...

As expected, showers developed over and north of the Cordillera
Central and Sierra de Luquillo this afternoon. The atmosphere still
conductive for additional shower development through at least the
early evening hours. With the heaviest showers continue to expect
ponding of water in low lying areas and minor flooding. Rises
along Manati and Cibuco Rivers are likely tonight due to excessive
runoff.

Although the induced surface trough across the forecast area will
continue to weaken overnight and Wed; low level moisture will
continue to pool across the eastern Caribbean. Moisture advection
across the local islands is in response to another surface front and
associated induced/prefrontal trough which is expected to exit the
eastern USA Wed morning. The aforementioned surface front and
associated induced/prefrontal will continue to promote east
southeast winds. As a result, there is a high chance for showers
across USVI and E PR at times with locally induced showers and
even thunderstorms with heavy rainfall over the central and
northern areas of Puerto Rico.

.LONG TERM...Thu Night thru Day 8/issued 447 AM AST Tue Mar 21 2017...

High amplitude trough is forecast to deepen and extend across the
Greater Antilles into the west and central Caribbean Thursday through
Friday. This will gradually increase instability aloft and enhanced
upper level divergence across the region. A subtropical jet max is
forecast to round the base of the upper trough and lift
northeastward just north of the forecast area. In the low levels, a
broad inverted surface trough will linger across the central and
eastern Caribbean. As a result, a moist southeasterly flow will
persist through Friday and into the weekend. Therefore a much wetter
pattern with enhanced tropical moisture advection is forecast for
the next several days. Good moisture convergence along the
approaching frontal boundary, and surface trough along with the
upper level instability will favor increased potential for enhanced
convection across the region through the weekend and at least until
Tuesday of next week. Thereafter winds are forecast to become more
northeasterly as surface high pressure ridge will spread across the
west Atlantic. Until then, expect periods of late evening and
overnight passing showers along portions of the north and east
coastal sections of the islands,followed by afternoon convection
with enhanced shower activity particularly across the interior and
northern half of Puerto Rico. The potential for periods of locally
heavy rainfall with minor urban and small stream flooding in
isolated areas will therefore remain high across portions of the
islands especially Puerto Rico.

&&

.AVIATION...VFR conditions are expected to continue across most
of the local flying area for the forecast period. However, sea
breeze convergence and other local effects will continue to produce
the development of SCT-BKN ceiling with SHRA along Cordillera
Central and northwest PR between until at least 21/22Z, inducing
tempo MVFR conditions over TJMZ and TJBQ. Latest TJSJ sounding
indicated a very light wind flow up to 17K feet, becoming west
southwest and stronger, up to 70 Knots, above 17K feet.

&&

.MARINE...Seas will continue to increase overnight as northerly
swell reaches the local waters. Seas up to 7 feet are expected
across the offshore Atlantic waters with a moderate to high risk
of rip currents along the Atlantic shoreline. A larger northerly
swell is still forecast to arrive and spread across the Atlantic
waters and local passages will by late Friday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 74 86 75 / 30 30 40 30
STT 85 75 84 75 / 30 50 50 40

&&
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Re: Caribbean - Central America Weather

#18727 Postby cycloneye » Wed Mar 22, 2017 5:13 am

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
507 AM AST Wed Mar 22 2017

.SHORT TERM...Today thru-early Fri...
An east to southeasterly wind flow between 5-15 mph will prevail
for much of the forecast period. Max temps should reach the high
80s across coastal areas. A few showers will reach areas of eastern
PR and the USVI through the morning hours, which can result in minor
ponding of water on roadways and in low lying areas.

Upper ridge southeast of the area will continue to weaken as trough
pattern aloft builds from the west through the end of the week. At
low levels a prefrontal trof is forecast to move over the islands on
Friday. As this trough pattern unfolds moisture will continue to
pool across the area and the intensity and coverage of showers and
isolated thunderstorms will increase each day. Therefore, diurnally
induced afternoon convection with some favorable upper level
conditions will lead to periods of moderate to heavy rainfall along
and to the north of the Cordillera Central each day. This will continue
to pose a threat of at least urban and small stream flooding through
the short term period.

.LONG TERM...Late Fri thru Wed...
Expect frequent periods of late evening and overnight passing
showers along portions of the north and east coastal sections of
the islands,followed by afternoon convection with enhanced shower
activity particularly across the interior and northern half of
Puerto Rico each day. The potential for periods of locally heavy
rainfall with minor urban and small stream flooding in isolated
areas will remain high across portions of the islands especially
for the northern and eastern half of Puerto Rico.

Long wave trough across the western Atlantic is still forecast to
deepen and extend southwards into the west and central Caribbean
Thru the end of the week . This will increase instability over the
northeastern Caribbean leading to enhanced upper level divergence
across the region. The subtropical jet and associated maxima will
continue to strengthen and to round the base of the upper trough which
will lift northeastward to just north of the region. The inverted
surface trough is to continue to amplify and lift northwards across
the region with a weak surface low now forecast to develop just north
Hispaniola by Monday. As a result, a moist south to southeasterly
flow should persist through Friday and into the weekend. All model
guidance support a very moist and unstable pattern across the region
for the next several days with good tropical moisture advection. Moisture
convergence along a frontal shear line, along with the lingering surface
trough and instability aloft will all favor high potential for enhanced
convection across the region at least through Tuesday of next week.
Winds are forecast to become more easterly by Wednesday as the surface
trough weakens and the upper trough fills and lifts north of the
region. This should then support a gradual decrease in moisture
transport. However, moisture along the old frontal shearline
should return across the region to allow for nocturnal shower
activity, and diurnally induced afternoon convection which should
be focused over the interior and west sections of PR.

&&

.AVIATION...Mainly VFR conditions expected to prevail across all
terminals. However, afternoon SHRA development north of the mountain
ranges of PR can impact the flying area of TJSJ and TJBQ with tempo
MVFR conds. Mainly VCSH expected across the Leeward/USVI terminals,
this can result brief -RA and BKN cigs. Winds from the ESE at 10-15
knots below FL100...then SW-W and increasing with height. Sea breeze
variations expected across NW Puerto Rico btw 14z-22z.

&&

.MARINE...Local buoys continued to suggest seas building seas across
the local Atlantic waters. Seas will continue to increase as northerly
swell reaches the local waters. Seas up to 7 feet are expected across
the offshore Atlantic waters. A larger northerly swell is still forecast
to arrive and spread across the Atlantic waters and local passages by
late Friday with deteriorating conditions though the weekend.
&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 75 86 76 / 40 30 40 50
STT 84 75 84 73 / 50 40 40 50

&&
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Re: Caribbean - Central America Weather

#18728 Postby cycloneye » Wed Mar 22, 2017 3:18 pm

Area Forecast Discussion
National Weather Service San Juan PR
245 PM AST Wed Mar 22 2017

.SYNOPSIS...A nearly stationary frontal boundary extending from
the north-central Atlantic southwest to the Windward Passage
between Hispaniola and Cuba. An Atlantic high pressure ridge
slowly moving east.


&&

.SHORT TERM...Tonight through Friday morning...Widely scattered
showers currently affecting the local area should diminish once
diurnal heating diminishes. Surface flow will continue from
southeast tonight and Thursday but will become more southerly and
lighter Thursday night and Friday as a strong low pressure system well
north over the northern Atlantic pulls a trough north from the
eastern Caribbean and over the area. This southeast to south flow
will bring increased moisture through the end of the work week. A
weak frontal boundary will hover to the north to enhance this
situation. A deepening upper level trough over cuba and jet north
of us will hold favorable divergence aloft. This will maintain
partly to mostly cloudy conditions with scattered showers.
Although heavy rains may occur in northwest Puerto Rico during the
afternoons, rains in general will be more probable on Friday with
isolated urban and small stream flooding possible.

.LONG TERM...Friday night through day 8/issued 455 AM AST Wed Mar
22 2017...
Expect frequent periods of late evening and overnight passing
showers along portions of the north and east coastal sections of
the islands,followed by afternoon convection with enhanced shower
activity particularly across the interior and northern half of
Puerto Rico each day. The potential for periods of locally heavy
rainfall with minor urban and small stream flooding in isolated
areas will remain high across portions of the islands especially
for the northern and eastern half of Puerto Rico.

Long wave trough across the western Atlantic is still forecast to
deepen and extend southwards into the west and central Caribbean
Thru the end of the week . This will increase instability over the
northeastern Caribbean leading to enhanced upper level divergence
across the region. The subtropical jet and associated maxima will
continue to strengthen and to round the base of the upper trough which
will lift northeastward to just north of the region. The inverted
surface trough is to continue to amplify and lift northwards across
the region with a weak surface low now forecast to develop just north
Hispaniola by Monday. As a result, a moist south to southeasterly
flow should persist through Friday and into the weekend. All model
guidance support a very moist and unstable pattern across the region
for the next several days with good tropical moisture advection. Moisture
convergence along a frontal shear line, along with the lingering surface
trough and instability aloft will all favor high potential for enhanced
convection across the region at least through Tuesday of next week.
Winds are forecast to become more easterly by Wednesday as the surface
trough weakens and the upper trough fills and lifts north of the
region. This should then support a gradual decrease in moisture
transport. However, moisture along the old frontal shearline
should return across the region to allow for nocturnal shower
activity, and diurnally induced afternoon convection which should
be focused over the interior and west sections of PR.

&&

.AVIATION...Mountains obscurations with isolated areas of MVFR conds
with CIGS 020-030 are expected in central and northern PR affecting
mainly TJBQ/TJMZ. Elsewhere VFR conds will prevail. Winds sfc to
FL050 SE 10 to 15 kts. Maximum winds WSW 75 knots at FL400.


&&

.MARINE...Seas up to 7 feet are expected across the offshore
Atlantic waters tonight. Seas will diminish by thursday morning
however a larger northerly swell is expected to impact the
Atlantic waters and local passages by late Friday with
deteriorating conditions though the weekend.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 87 77 85 / 20 40 50 50
STT 75 85 74 84 / 30 30 50 50

&&
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Re: Caribbean - Central America Weather

#18729 Postby cycloneye » Thu Mar 23, 2017 5:32 am

Area Forecast Discussion
National Weather Service San Juan PR
509 AM AST Thu Mar 23 2017

.SHORT TERM...Today thru Saturday...Deep southerly wind flow will
continue to pool moisture across the forecast area. As a prefrontal
trof establish over the islands and an upper level trof pattern
evolves from the west in the short term period. For today...through
the morning hours, showers will continue to develop over the Caribbean
waters and move over the USVI and the southern/eastern portions of
PR. During the afternoon hours, high res models are indicating shower
development over the north/northwest quadrant of PR. Shower activity
will remain high through the forecast period across the Atlantic waters
due to a meandering shearline between Hispaniola and the Mona Passage.

Better moisture advection over the islands is expected on Fri
through Saturday and in combination with good divergence aloft...
scattered to numerous showers and isolated thunderstorms are expected
each day. Forecast soundings are indicating a gradual increase in
PWAT from around 1.70 inches today to near 2 inches on Saturday.
Localized urban and small stream flooding is very likely these two
days.

.LONG TERM...Sunday-next Friday...The mid to upper level trough is
forecast to deepen and extend southwards into the west and central
Caribbean through early Sunday. The trough will then lift further
north into the west and central Atlantic. A developing surface low
north of Hispaniola with the associated trough will continue to induce
a moist southerly flow and unstable weather pattern across the region
until Monday or early Tuesday. Winds are to become more northerly
by late Tuesday through the end of the week, as surface high pressure
will build across the western Atlantic and north of the region. By
Wednesday of next week through Friday, north to northeast winds
should prevail and this should bring much drier and stable condition
to the region. However brief early morning passing showers cannot
be ruled along the north coastal areas due to the prevailing northerly
winds. This will be followed by isolated to scattered afternoon shower
activity each day.

In the meantime...Deep layered moisture advection and instability
aloft due to upper trough and subtropical jet maxima will persist
over the northeastern Caribbean through Sunday. Enhanced early
morning and afternoon convection will be likely across the islands
and coastal waters. The upper trough and subtropical jet maxima will
fill and lift north of the region by late Monday and Tuesday resulting
in less favorable conditions aloft for enhanced convection and a gradual
decrease in morning and afternoon shower activity. The potential for
periods of locally heavy rainfall with minor urban and small stream
flooding as well as quick rising of water levels along rivers and
guts will remain high across portions of the islands at least until
Monday of next week due to saturated soils and the expected unstable
weather conditions.

&&

.AVIATION...SHRA will continue across the regional waters and btw
the eastern PR and the USVI. These showers can result in tempo MVFR
conds at TIST/TISX. Sct-bkn cigs btw FL030-060 expected to continue
with mountain obscd over PR through the fcst period. Additional SHRA
is expected during the afternoon and periods of MVFR conds cant be
ruled out at TJSJ/TJBQ/TJMZ. Iso TSTMs possible after 24/00z over
the offshore waters. Southerly winds around 10 kts expected blo
FL100...bcmg SW-W above and increasing w/height. VFR expected for
much of the fcst period at TNCM/TKPK.

&&

.MARINE...Recent buoy observations continue to suggest seas up to
7 feet across the offshore Atlantic waters. As a result, the Small
Craft advisory has been extended until 10 am AST this morning. A larger
northerly swell generated by the developing low is expected to impact
the Atlantic waters and local passages by late Friday. This will again
create hazardous and building seas over the weekend. Please refer to
the latest Coastal Waters Forecast (CWFSJU) and Marine Weather Message
(MWWSJU) issued by WFO San Juan PR for additional information on the
local marine hazards.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 74 85 75 / 40 50 70 50
STT 83 73 82 73 / 30 60 60 60
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