Caribbean - Central America Weather

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cycloneye
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Re: Caribbean - Central America Weather

#20201 Postby cycloneye » Tue May 12, 2020 5:48 am

Area Forecast Discussion
National Weather Service San Juan PR
414 AM AST Tue May 12 2020

.SYNOPSIS...Surface high pressure over the Atlantic will continue
to promote an east to southeast wind flow for the next several
days. Near or below normal moisture is expected for the next
several days, but brief patches of moisture will move in
occasionally. Mid and upper level ridge is expected to prevail
through the rest of the workweek as well. Mostly stable
conditions are expected for the rest of this week, but brief
isolated to scattered showers in the mornings and overnight hours
can be expected across the local waters, eastern Puerto Rico and
the USVI. Locally induced afternoon showers can be expected across
western to northwestern Puerto Rico. Temperatures are expected to
be slightly above normal, in the upper 80s to low 90s across the
lower elevations for the next several days.


&&

.SHORT TERM...Today through Thursday.

Surface high pressure to the northeast of the local area will
continue to cause east to southeasterly winds over the region. As
a result, warm temperatures are expected today and Wednesday over
the lower elevations of the local islands. Also, passing showers
will move into the eastern sections of Puerto Rico and over the
U.S. Virgin Islands from time to time this morning. Afternoon
convection will be focused over the northwestern and interior
sections of Puerto Rico. On Wednesday, drier air is expected to
filter over the region, providing fair weather conditions,
especially in the nighttime hours. A slight increase in moisture
is expected once again on Thursday, increasing the probability of
shower activity in the morning and evening hours over the local
waters, eastern sections of Puerto Rico and the U.S. Virgin
Islands. Also, locally induced afternoon shower activity over the
western sections of Puerto Rico is expected.

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

Near or below normal moisture is expected in the long term. The
long range guidance has been consistent in showing that mainly
stable conditions will continue through the weekend. However, the
latest model run is showing an upper level low to the north of the
local area on Monday, moving south and causing divergence and
increasing instability for the first half of next week, which
would translate to more significant shower activity, especially
across the northern sectors of our local area. That said,
confidence is low and more consistency between the different model
runs should be achieved before confidence increases.
Nevertheless, brief isolated to scattered showers are expected
across the local waters, eastern Puerto Rico and the USVI, with
locally induced showers developing across western Puerto Rico in
the afternoons. The days with higher moisture are expected to be
on Friday, but the mid to upper levels are not conducive for
widespread heavy showers. Therefore, any significant showers
should be somewhat limited with moderate showers having more
coverage. The drier than normal conditions and the east to
southeast winds will cause the high temperatures to also be above
normal, reaching the upper 80s to low 90s across the lower
elevations.


&&

.AVIATION...VFR conditions will continue to prevail at all TAF sites.
Some Brief -SHRA to Isolated SHRA are possible in and around
TJSJ, TJMZ and TJBQ between 12/14z and 12/20z. ESE winds to
continue at around 15 knots with some wind gusts up to 25kt and
sea breeze variations.

&&

.MARINE...Small craft operators are urged to exercise caution
today due to choppy seas up to 6 feet and winds up to 20 knots.
The local seas are expected to improve slightly on Wednesday, with
seas up to 5 feet, but the local winds will still be up to 20
knots. There is a moderate risk of rip currents for most of the
local beaches today.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 76 89 75 / 30 20 30 40
STT 87 77 87 76 / 10 20 30 30
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Re: Caribbean - Central America Weather

#20202 Postby cycloneye » Wed May 13, 2020 5:43 am

Area Forecast Discussion
National Weather Service San Juan PR
444 AM AST Wed May 13 2020

.SYNOPSIS...Surface high pressures over the western Atlantic and
over the east-central Atlantic will continue to promote an east
to east-southeast wind flow over the next several days. Near or
below normal moisture continues to be expected for the next
few days, but brief patches of moisture will move in
occasionally. Mid and upper level ridge is expected to prevail
through the rest of the workweek as well. Isolated to scattered
showers are expected in the mornings and overnight hours across
the local waters, eastern Puerto Rico and the USVI. Locally
induced afternoon showers can be expected across western to
northwestern and central Puerto Rico. Daytime high temperatures
are expected to be slightly above normal, in the upper 80s to low
90s across the lower elevations for the next several days.

&&

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

A surface high pressure over the western Atlantic and another
surface high pressure across the east-central Atlantic will cause
an east to east-southeast wind flow across the region for the
next few days. Patches of low-level moisture will continue to move
across the region, causing brief showers in the morning and
evening hours for the eastern sections of Puerto Rico and over the
US Virgin Islands. Also, afternoon convection is expected to
develop across the interior and western sections of Puerto Rico,
which will result in scattered to locally numerous showers, some
of which could be moderate to locally heavy at times. This shower
activity could produce ponding of water on roadways and poor
drainage areas as well as some urban flooding. Another warm day
is expected today across the coastal sections of the islands with
highs in the low 90s.

GFS model guidance suggest a little more moisture across the region
for Thursday into Friday with precipitable values between 1.3 to 1.7
inches, but the deeper moisture is expected across northern Puerto
Rico and the Atlantic waters. This moisture in combination with
the local effects will result in afternoon showers across
northwestern Puerto Rico today. On Thursday and Friday, a similar
weather pattern is expected, but there is slightly less available
moisture, and therefore the afternoon shower activity is expected
to be less than that expected for today.

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

Near or below normal moisture is expected in the long term. The
long range guidance has been consistent in showing that mainly
stable conditions will continue through the weekend. However,
there is now an indication of an upper level low to the northwest
of the local area on Tuesday, moving south and causing divergence
and increasing instability on Tuesday and Wednesday, which would
translate to more significant shower activity and perhaps a few
thunderstorms across the northern sectors of our local area. That
said, confidence is low and more consistency between the
different models should be achieved before confidence increases.
Nevertheless, isolated to scattered showers continue to be
expected across the local waters, eastern Puerto Rico and the
USVI, with locally induced showers developing across western
Puerto Rico in the afternoons. The days with higher moisture are
expected to be on Tuesday into Wednesday of next week. The overall
drier than normal conditions and the east to southeast winds will
cause the high temperatures to also be above normal, reaching the
upper 80s to low 90s across the lower elevations.

&&

.AVIATION...VFR conditions will continue to prevail at all TAF sites.
Brief -SHRA/SHRA possible in and around TJMZ and TJBQ between
13/12Z and 13/18Z. ESE winds to continue at around 15 knots with
some wind gusts up to 25kt and sea breeze variations.


&&

.MARINE...Seas are expected to be choppy today, with seas up to 6
feet and winds up to 20 knots. Small craft operators are urged to
exercise caution. There is a moderate risk of rip currents today
across most of our local beaches.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 76 87 77 / 30 20 20 30
STT 87 78 87 76 / 20 20 30 30
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Re: Caribbean - Central America Weather

#20203 Postby cycloneye » Thu May 14, 2020 5:34 am

Area Forecast Discussion
National Weather Service San Juan PR
439 AM AST Thu May 14 2020

.SYNOPSIS...
A surface high pressure across the north-central Atlantic and another
entering the western Atlantic behind a weakening cold front, will
maintain a moderate east to east-southeast winds across the region
into the upcoming weekend. Weak ridging and high zonal flow will
persist for the next several days to maintain dry and stable conditions
aloft. Patches of low level moisture will generate passing showers
across the region in the prevailing trade wind flow through most of
the period. However, better moisture transport and convergence is
expected for the latter part of next week, due to an easterly wave
forecast to approach and move across the region.

&&

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

A drier air mass is filtering in from the east, causing the
available moisture to be below normal for the next several days.
This will limit the potential of rain activity across the islands,
that said, brief isolated to scattered showers are possible and
expected over eastern Puerto Rico and the U.S. Virgin Islands during
the overnight and early morning hours these next few days. During
the daytime hours, mainly fair weather is expected by the mid-
morning hours, but in the early afternoon hours, showers can start
developing across portions of western and northwestern Puerto Rico.
However, these showers are not expected to be too heavy over large
areas. A surface high pressure over the western Atlantic will maintain
an east to east-southeast wind flow over the area for the next few
days. A mid to upper level ridge over the area will make it difficult
for convection to occur over the local islands. In terms of temperatures,
under this pattern, slightly above normal temperature should persist
across the islands with high temps in the upper 80s to lower 90s,
but heat indices are not expected to surpass 100 degrees due the
drier air mass.

.LONG TERM...Sunday through Saturday...

A mid to upper high pressure ridge along with the surface ridge across
the north central Atlantic will continue to dominate the the local
weather pattern through at least the early part of next week. That
said, expect the continued pattern of passing early morning showers
across the regional waters with some brushing parts of the islands
from time to time. Locally and diurnally induced afternoon showers
will remain possible each day, but should be focused mainly over
parts of the west interior and northwest sections of Puerto Rico.
No significant or widespread rainfall accumulations are forecast
across the islands at least through Tuesday. However by the middle
of next week and into Saturday an increase in low level moisture
convergence is so far expected. This is due to the arrival of the
aforementioned easterly wave forecast to move cross the region;
along with the gradual erosion of the upper level ridge in response
to a polar trough expected to develop and amplify across the western
Atlantic. Confidence however remains low as there is still some
inconsistencies between model guidance and the timing may be a bit
off. All in all, expect overall dry and stable conditions for the
early part of the period follow by a somewhat wetter and more
unstable pattern during the latter part of next week.

&&

.AVIATION...Prevailing VFR conds can be expected across the local
terminals for the next 24 hours. ISOL/SCT SHRA across the local area
may cause VCSH in the morning across the USVI and TJSJ terminals,
while VCSH is possible at TJBQ and TJMZ after 14/17Z. The local
winds will be from the East To ESE with sea breeze variations at
around 15 KT with occasional gusts today, decreasing after 14/23Z.

&&

.MARINE...Choppy seas up to 6 feet are expected to continue across
portions of the local waters. Mariners can expect winds from the
east-southeast at 10 to 20 knots. A few passing showers can be
expected during the rest of the early morning hours across the
local waters between Puerto Rico and the U.S. Virgin Islands, and
mainly over the western offshore waters of the islands during the
afternoon hours.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 77 88 77 / 20 40 40 30
STT 87 77 87 77 / 30 20 20 30
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Re: Caribbean - Central America Weather

#20204 Postby cycloneye » Fri May 15, 2020 5:32 am

Area Forecast Discussion
National Weather Service San Juan PR
505 AM AST Fri May 15 2020

.SYNOPSIS...
Surface high pressure over the north central Atlantic will maintain
a moderate east to southeast wind flow across the region today.
However, low level winds will become more south southeasterly over
the weekend as a developing surface low moves into the west and
northwest Atlantic. Under this pattern, intermittent patches of
shallow moisture with pockets of drier air embedded in the trade
winds will stream across the region from time to time. The mid to
upper level will remain dry and stable for the next several days,
and therefore limit and suppress any significant convection. Warm
daytime temperatures and local and diurnally induced showers can
be expected each day across portions of the islands through at
least the beginning of next week. Otherwise, mostly sunny skies
should prevail across much of the islands through the weekend.

&&

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

A surface high pressure over the north central Atlantic will
maintain a generally moderate to locally fresh east to southeast
wind flow across the region today. However, winds will briefly favor
a more southeasterly direction as a deepening surface low moves
into the western Atlantic across the Bahamas during the weekend.
Under this flow pattern, intermittent patches of moist and drier
air embedded in the trade winds will stream across the region.
First, relatively drier air and unfavorable conditions aloft will
influence the local weather conditions today. Although this
combination would inhibit shower development, overnight and early
morning isolated showers are expected to move inland across
portions of eastern Puerto Rico and over the USVI. As the day
progresses, limited afternoon convection is expected to develop
across the extreme northwestern portion of Puerto Rico. Streamer-
like showers downwind from El Yunque and the local islands cannot
be ruled out. Nevertheless, significant rainfall accumulations nor
flooding is expected with this activity.

Model guidance suggests that although the mid-level ridge is
expected to strengthen during the next few days, a slight
enhancement in shower activity can be expected later today into
Saturday. This is the result of a 700 mb layer perturbance that
will briefly weaken the trade wind cap, resulting in somewhat
favorable conditions aloft. The timing of a patch of low-level
moisture will coincide with this event, providing sufficient
moisture to support enhanced shower activity across the area,
particularly across eastern Puerto Rico and the US Virgin Islands.
Hostile environmental conditions for shower development with the
strengthening of the trade wind cap and a decline in available
moisture content will gradually return on Sunday and continue
through early next week. Warmer daytime temperatures are expected
during the weekend under the southeasterly wind flow.

.LONG TERM...Monday through Sunday...

A mid to upper high pressure ridge along with the surface ridge across
the north central Atlantic will continue to dominate the local weather
pattern through the early part of next week with a similar pattern
of passing early morning showers across the regional waters and some
brushing parts of the islands from time to time. Locally and diurnally
induced afternoon showers will remain possible each day, but should
be focused mainly over parts of the west interior and northwest
sections of Puerto Rico. No significant or widespread rainfall
accumulations are forecast across the remainder of the islands at
least through Tuesday. However by the middle of next week and
into the weekend model guidance still suggest a slight increase
in low level moisture convergence and better chance for early
morning ahd afternoon shower activity. This is mainly due to the
arrival of an easterly wave forecast to move cross the region
along with the gradual erosion of the upper level ridge as a
polar trough is expected to develop and become amplified across
the western Atlantic. At this time, confidence still remains low
for the latter part of the period but for now expect overall dry
and stable conditions for the early part of the period, followed
by a slightly wetter and more unstable pattern during the latter
part of next week.

&&

.AVIATION...Mainly VFR conditions expected the next 24 hours.
However, SHRA will result in VCSH at TJSJ, USVI and Leeward
terminals through at least 15/10Z. Then, afternoon convection will
bring VCSH to TSJU, TJMZ, and TJBQ between 15/14-23Z. Light and
variable winds expected at PR terminals through around 15/10Z,
turning from the E-SE at 10-15 knots with higher gusts there after.
An E-SE wind flow will persist at USVI/Leeward terminals through the
period.

&&

.MARINE...Choppy marine conditions due to east-southeast winds
between 15 and 20 knots. Seas will range between 2 and 5 feet
with occasional seas up to 6 ft mainly offshore and in the local
passages. Mariners should continue to exercise cautions.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 77 90 77 / 30 30 30 20
STT 88 78 87 79 / 30 30 20 20
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Re: Caribbean - Central America Weather

#20205 Postby cycloneye » Sat May 16, 2020 5:11 am

Area Forecast Discussion
National Weather Service San Juan PR
508 AM AST Sat May 16 2020

.SYNOPSIS...A generally moderate to fresh east to southeast wind
flow will prevail through most of the forecast period. Although
fragments of low-level moisture will enhance shower activity from
time-to-time, a mostly dry and stable weather pattern is expected.
By the latter part of the week, the passage of a weak tropical
wave will result in a slight increase in moisture and thus, a
better chance for shower activity. Choppy marine conditions will
continue during the weekend into early next week.


&&

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

Recent satellite derived precipitable water product and the National
Weather Service doppler radar imagery depicted a surge of moisture
with some embedded showers moving across the region steered by the
moderate to fairly strong east southeast wind flow. A few showers
will continue to affect parts of the south and east coastal areas of
the islands from time to time into the early morning hours. Rainfall
accumulations are not expected to be significant at this time.
However, some minor ponding of water on roadways and in poor
drainage areas will be possible with the isolated areas of heavy
downpours. By late morning and into the afternoon expect a drier
airmass to spread across the region leading to mostly sunny skies
with overall fair weather conditions for much of the islands. The
exception will be in the northwest sections of Puerto Rico and some
areas downwind of EL YUNQUE rainforest where brief showers will be
possible in the form of streamers. So far expect afternoon showers
over the islands to be of short duration an will be diurnally and
locally induced. Daytime high temperatures are again expected to
soar to around 90 degrees today and through the weekend under the
prevailing south southeast low level wind flow. Afternoon shower
activity will quickly move off and dissipate over land areas by
sunset leaving partly cloudy to mostly clear skies.

For Sunday and through Monday, the surface high pressure will
continue to spread across the western and central Atlantic and thus
maintain a southeasterly wind flow over the area. Therefore, warmer
temperatures are expected to continue across the islands into early
next week, with daytime highs expected to continue around 90 degree
for the coastal areas. The mid-upper level ridge will continue to
hold over the eastern Caribbean through Monday, acting as a limiting
factor for significant convective development. However, do expect
periods of shallow moisture embedded in the trade winds to continue
to stream across the region. This will result in occasional showers
over portions of the local waters and coastal areas of the islands
especially overnight and during the early morning hours. Daytime
convection will be limited to [portions of the northwest and north
sections of Puerto Rico, as well as mainly downwind and on the west
end of the U.S Virgin Islands. That said, significant rainfall
accumulations are not anticipated through the weekend. In addition,
a low concentration of suspended saharan dust particulates will
linger across the region at least through early Sunday promoting
somewhat hazy conditions.


.LONG TERM...Tuesday through Monday...

A generally moderate to fresh east to southeast surface wind flow
will prevail through the long-term forecast period. This is the
result of two independent surface high pressure streaming across
the north central Atlantic. In the meantime, a mid-level ridge is
expected to remain over the area, creating unfavorable conditions
aloft for convective development. Nevertheless, intermittent
fragments of relatively drier air and low- level moisture embedded
in the trades will dictate the timing, intensity and extend of
showers affecting the area. Overall, a seasonal weather pattern
with overnight and morning showers moving inland across portions
of eastern and southern Puerto Rico and the USVI, followed by
locally and diurnally induced afternoon showers across
northwestern Puerto Rico is expected each day, even in the driest
day. Streamer-like showers downwind from El Yunque and the local
islands into the San Juan metropolitan area and eastern Puerto
Rico cannot be ruled out each afternoon. Model guidance suggests
that a weak tropical wave will stream across the region by the
latter part of the week, while the mid-level ridge briefly
weakens. The wave is expected to enhance low-level moisture
convergence and thus, a wetter and more unstable weather pattern
with a better chance for shower activity is expected under
somewhat favorable conditions aloft. However, uncertainties are
high and there is low confidence in this forecast.


&&

.AVIATION...VFR at all terminals and to and from the local islands.
SCT lyrs nr FL030...FL050 ocnl BKN nr FL080 en route btw PR and the
Northern Leewards with isold passing SHRA til 16/14Z. Low level
winds will be fm ESE 15-20 kts BLO FL100, bcmg fm W and incr with ht
abv FL200. Sfc wnd light and variable bcmg mainly ESE around 15 kts
and ocnl hir gusts and sea breeze variations aft 16/14z.


&&

.MARINE...Small craft operators are urged to exercise caution due
to seas up to 6 feet and winds up to 20 knots across the local
waters, except for the Mona Passage and coastal waters of
northwestern Puerto Rico where seas are expected to remain at or
below 5 feet. There is a moderate risk of rip currents for beaches
along the north, south central, and southeast coast of Puerto
Rico, as well as most beaches in Culebra and beaches along the
south coast of Vieques. Beaches along the south coast of Saint
Thomas and Saint John, and beaches along the south and extreme
east coast of Saint Croix are also under a moderate risk of rip
currents.



&&

.FIRE WEATHER...KBDI and 10-hour fuel moisture values continue to
support a drying trend across the southeast coastal plains with a
recent observation of 720 and 9% in the Camp Santiago area,
respectively. Today`s forecast calls for a mass of relatively
drier air to move into the area, suppressing shower activity while
relative humidity values drop into the low to mid 40s between the
late morning and early afternoon hours. Given current
soil/vegetation conditions and the expected weather pattern,
elevated fire weather conditions are anticipated, particularly
across the southeast coastal plains of Puerto Rico. As a result, a
Fire Danger Statement has been issue for this area. Although a
similar weather pattern with relative humidity dropping into the
low to mid 50s and winds up to 18 mph is expected across the
southwestern coastal plains of Puerto Rico, KBDI values have
remain below fire danger thresholds.



&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 91 78 91 78 / 20 30 30 30
STT 88 80 88 78 / 20 30 20 30
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Re: Caribbean - Central America Weather

#20206 Postby msbee » Sat May 16, 2020 5:25 pm

Hi Luis
thanks as always for the updates. Tis the season once again, so time to start watching more closely.
Hope you are safe in PR.
Barbara
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Re: Caribbean - Central America Weather

#20207 Postby cycloneye » Sat May 16, 2020 5:28 pm

msbee wrote:Hi Luis
thanks as always for the updates. Tis the season once again, so time to start watching more closely.
Hope you are safe in PR.
Barbara


Another year to watch for us. Let's see how the Caribbean fares this season but hopefully all is calm.
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Re: Caribbean - Central America Weather

#20208 Postby cycloneye » Sun May 17, 2020 5:02 am

Area Forecast Discussion
National Weather Service San Juan PR
504 AM AST Sun May 17 2020

.SYNOPSIS...A moderate to locally fresh east to east-southeast
wind flow will prevail during the next few days. Although mostly
fair and stable weather conditions are expected, fragments of low-
level moisture embedded in the trades will support shower
activity from time-to-time. An increase in moisture with the
passage of a weak tropical wave and somewhat favorable conditions
aloft are forecast to enhance shower activity by the latter part
of the week into the weekend. Breezy conditions will maintain
choppy seas during the next few days.


&&

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

Surface high pressure anchored across the north central Atlantic and
Tropical Storm Arthur moving north northeast across the west and
northwest Atlantic will continue to promote an overall southeasterly
wind flow across the region through the period. This low-level flow
will cause warmer than normal temperatures mainly along the northern
half of Puerto Rico, where high temperatures will continue to reach
the low 90s. During the entire period expect a continued dry and
stable airmass to prevail as a mid-level ridge will linger overhead
and result in mostly fair weather conditions for most of the local
area. However, occasional patches of low-level moisture embedded
within the trade wind flow will continue to move across the area
from time to time. This may result in brief showers across portions
of eastern and southern Puerto Rico and the USVI during the
overnight and early morning hours. This will be followed by the
development of isolated to scattered showers across northwestern
Puerto Rico during the afternoon hours due to local and diurnal
effects. Given the limited moisture content and the overall stable
conditions aloft, no significant rainfall is expected during the
afternoon hours for the entire period. A low concentration of
suspended Saharan Dust particulates is expected to affect the area
at least until today resulting in somewhat hazy skies. Improving and
less hazy conditions is forecast for Monday and Tuesday but periods
of early morning and afternoon showers will remain possible each
day.


.LONG TERM...Wednesday through Tuesday....

The reasoning behind the long-term forecast hasn`t change much in
the last few days. Overall, a generally moderate to locally fresh
east to east-southeast wind flow will prevail. However, winds are
expected to diminish and gradually turn from the southeast during
the upcoming weekend into early next week. Under a southeasterly
wind flow, above normal temperaturas can be expected. At mid-
levels, a ridge is hold over the region, generating unfavorable
conditions for convective development. However, fragments of low-
level moisture embedded in the trades will dictate the timing,
intensity and extend of showers affecting the area. This activity
will favor a seasonal weather pattern with overnight and morning
showers moving inland across portions of eastern and southern
Puerto Rico and the USVI, followed by locally and diurnally
induced afternoon showers across northwestern Puerto Rico and
downwind from El Yunque and the local islands each day. Model
guidance continues to suggest that the passage of a weak tropical
wave will enhance low-level moisture convergence and thus, a
better chance for shower activity by the latter part of the week
into the weekend. Somewhat favorable conditions aloft, resulting
from the weakening of the trade wind cap, may also play an
important role in the extent of this activity. Deep moisture and
favorable conditions may continue through early next week with the
bulk of the showers favoring northwestern sections of Puerto Rico
each afternoon. However, uncertainties are high and confidence
remains low for this forecast.


&&

.AVIATION...VFR conds will prevail across the region during the
period with only SCT lyrs nr FL025...FL050. Isold passing -SHRA/SHRA
ovr regional waters and en route btw islands til 17/14Z. Low level
winds fm SE 10-20 kts BLO FL200, bcmg fm W and incr with ht ABV. Sfc
wnd calm to light and variable bcmg fm SE around 15 kts and ocnl hir
gusts and sea breeze variations aft 17/14z.


&&

.MARINE...Small craft operators are urged to exercise caution due
to seas up to 6 feet and winds up to 20 knots across the Atlantic
waters, offshore Caribbean waters and local passages. Elsewhere,
tranquil marine conditions with seas up to 5 feet and winds up to
15 knots will persist. There is a moderate risk of rip currents
for most of the local beaches, except beaches along the west and
east coast of Puerto Rico, as well as along the north coast of
Saint Croix and Saint John.

&&

.FIRE...Although recent KBDI and fuel moisture observations
continue to support a drying trend within critical fire danger
thresholds, an area of low-level moisture is expected to maintain
relative humidity above fire danger thresholds today. This patch
may also bring some wetting rains across eastern and southern
sections of Puerto Rico in the morning, and northwestern sections
of Puerto Rico in the afternoon. Winds will be generally from the
east to east-southeast at 10-15 mph with higher gusts and sea
breeze variations. Given these conditions, a low fire danger risk
is expected. However, if this patch of moisture moves quickly
enough, briefly elevated fire danger conditions may be triggered
early this afternoon. As a result, a Fire Danger Statement could
be issued later today, if necessary.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 91 77 90 77 / 20 20 30 30
STT 87 79 87 77 / 20 20 30 30
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Re: Caribbean - Central America Weather

#20209 Postby cycloneye » Mon May 18, 2020 5:37 am

Area Forecast Discussion
National Weather Service San Juan PR
449 AM AST Mon May 18 2020


.SYNOPSIS...East-southeasterly winds will continue over the
region, bringing dry and warm air for the next few days with some
Saharan dust. However, wetter weather will arrive for later this
week and continue into next week. Localized flooding is possible
for late this week as heavy showers are expected. Seas will
continue somewhat choppy until mid-week, after which calmer seas
are in the forecast.

&&


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

A surface high pressure located across the central Atlantic will
continue to promote a moderate east to east southeast wind flow
across the area. Within this flow, weak patches of low-level
moisture will stream across the area. Satellite pictures indicated
the best cloud coverage now in the western tropical Atlantic, but
best columnar moisture (about 1.7 inches) is across Puerto Rico and
also over the Atlantic just northeast of the Leeward Islands. The
moisture field is showing little movement for the time being, but
the latter moisture is expected to cross the U.S. Virgin Islands
overnight Monday into Tuesday and into Puerto Rico early Tuesday
morning. It will be followed by a dry slot from noon Tuesday to
midnight Tuesday night. Moisture then begins a long increase through
Wednesday and beyond. The moisture mentioned will bring the best
chances for showers during the period. Showers today are expected
mainly over northwest Puerto Rico this afternoon and over the
eastern third of Puerto Rico Monday night and Tuesday early morning.
Drier conditions are expected over eastern Puerto Rico this
afternoon, but a streamer could form downwind of El Yunque and bring
limited rainfall to parts of the Greater San Juan Metropolitan Area.

At upper levels a weak cut-off low pressure is forming just north of
us this morning and a moderate jet of 50-60 knots is wrapping around
the southern half of this low. The low will move to around 22 north
and 56 west by Tuesday and then pull northeast into the flow. On
Wednesday the ridge following the low will move across the area.
Although upper level moisture will increase somewhat and bring some
high clouds Tuesday and Wednesday, mid levels will continue very dry
through the period and any tall convection will be both brief and
weak.

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

Currently a fairly robust looking tropical wave resides to the
northeast of South America, but it is expected to fall apart by the
time it reaches our region later this week. However, its left
over moisture will begin to impact us on Thursday. Thus, Thursday
will be a transition day as our region begins to trend towards a
wetter weather pattern. Forecast models suggest precipitable water
values of around 1.3 for Thursday morning, then increasing to 1.5
by the afternoon, and 1.7 by Friday afternoon with higher amounts
nearby. Other factors will help to enhance shower activity,
especially after Thursday, with CAPE around 1500 J/kg for both
days and 500 mb temps around -7C by Friday. At this point, upper-
level atmospheric conditions doesn`t look super helpful for
thunderstorms, but some lightning looks possible. Drier air in
place for Thursday, especially at mid-levels, could inhibit shower
activity, but the drier air lessens for Friday, so that will be
the day to watch for the coming workweek for potential for urban
and small stream flooding.

Thereafter, moisture content is forecasted to increase even more
so during the remainder of the long-term period, with
precipitable water around 1.9, and with mid-levels moistening up
after Friday. There will also be plenty of CAPE to produce heavy
showers and isolated thunderstorms. Furthermore, wind speeds are
rather slow for the low to mid levels for Saturday through Monday,
and that could exacerbate the flooding threat. To summarize,
after some rather unseasonably dry weather in the short term
period, wetter weather will ensue for the latter half of this week
and continue into next week.

&&


.AVIATION...
Mainly VFR conditions expected during the next 24 hours.
Isold SHRA ovr lcl waters til arnd 18/15Z. Afternoon convection will
bring VCSH to TJMZ, TJPS and TJBQ between 27/17-23Z. This could
result in brief MVFR conditions with SCT-BKN between FL025-050.
Light and variable surface winds expected through around 18/14Z,
bcmg ESE at 10-20 knots with sea breeze variations thereafter.
Maximum winds WNW 50-65 kt btwn FL 375-485.

&&


.MARINE...

Winds will continue at 10-20 knots from the east to southeast,
resulting in seas up to 6 feet for the next few days. However,
these winds are expected to lighten up over the next few days, so
that by mid-week calmer seas will prevail. Only isolated showers
are expected across the local waters, but more active weather is
likely after Thursday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 91 77 90 78 / 10 30 30 20
STT 88 77 87 77 / 20 30 20 20
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Re: Caribbean - Central America Weather

#20210 Postby cycloneye » Tue May 19, 2020 5:12 am

Area Forecast Discussion
National Weather Service San Juan PR
448 AM AST Tue May 19 2020

.SYNOPSIS...

Fairly dry conditions will continue for the next few days, though
there still is the chance for some impactful showers each
afternoon . However, much wetter conditions are expected
beginning Friday, and especially into the weekend and early next
week. Areas of flooding are possible given the likelihood for
heavy and persistent showers, and there will also be a
possibility for isolated thunderstorms as well. Seas will
generally stay below 5 feet for the next week.

&&


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

Tropical Storm Arther along the east coast and a strong low in the
north central Atlantic will force the sub tropical ridge further
south to around 25 degrees north latitude, north of Puerto Rico and
the U.S. Virgin Islands. Arthur will weaken during the period, but
not before it spins a low off of itself that runs rapidly toward the
northeast. These lows will hold the high pressure closer to the
Canary Islands and allow east to southeast flow to continue across
the local area. Moisture is patchy and the driest air is expected
to be over us tonight with steadily wetter patches moving through
the area Wednesday and Thursday bringing slowly increasing shower
activity today through Thursday. 500 mb temperatures continue
between minus 6 and minus 7 degrees so have added a slight chance of
afternoon thunderstorms to west northwest portion of Puerto Rico
each day. 1000-850 mb thickness values forecast by the GFS indicate
a continuation of warmer than normal temperatures over the area with
many locations in the lower elevations reaching the upper 80s or the
lower 90s each day. Presently it looks like Thursday will be the
warmest day for the Greater San Juan Metropolitan area and the
coastal plains to the west.

At upper levels the weak cut-off low pressure is north of the
Leeward Islands morning and a moderate jet of 50-70 knots from the
west is wrapping around the southern half of this low. The low will
translate to the east and begin to merge with the westerly flow on
Wednesday. The ridge following the low will move across the area.
Although upper level moisture will increase somewhat and bring some
high clouds today and Wednesday, mid levels will continue very dry
through the period and any tall convection will be locally driven.

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

The long term forecast has not changed much since yesterday, in that
a trend towards wetter weather is still expected as we head towards
the weekend. It appears there will be two sources of moisture for
Friday and through the weekend. The remnants of a tropical wave will
move in Thursday through Saturday. Thereafter, models continue to
show low to mid level high pressure to just to our west over the
weekend that will push more moisture into our region from the north
for the beginning to middle of next week. With plenty of moisture in
place, and plenty of surface heating to drive sea breeze convergence
effects, the long-term period will be active, with the primary
threat being urban and small stream flooding.

Looking at Friday in more detail, there will still be plenty of dry
air at mid-levels that will be hostile to shower and thunderstorm
development. However, there will also be plenty of CAPE with
above average lapse rates to drive heavy showers, and isolated
thunderstorms are still in the forecast for northwestern Puerto
Rico. Given the east-southeasterly flow, the San Juan Metro area
will also possibly see lines of showers extending from El Yunque,
also known as streamers, producing moderate to heavy showers in
the afternoon. Urban flooding is possible, especially since low
level winds around 850-700 mb look slow, leading to persistent
showers. Interestingly, Friday might have the least potential for
impactful weather compared to the rest of the period. While
precipitable water values of around 1.7 in. are expected for
Friday, around 1.8-2.1 in. is expected for the rest of the long
term period, and model soundings look very moist after Friday.
This is not the perfect scenario, as CAPE and lapse rates only
look average, and there isn`t much of any upper-level feature to
produce divergence aloft and upward motion, with the exception of
some jet streaks that long range models don`t agree on.
Regardless, the long term period is likely to bring plenty of
rainfall, especially for northwest Puerto Rico and the San Juan
Metro given the east southeasterly flow. Impactful showers are
expected, and areas of flooding are very possible as well.

&&


.AVIATION...

Sct SHRA ovr lcl waters and ern PR thru 19/15Z. SHRA
will increase across PR with a slgt chc of TSRA WNW PR will aft
19/17Z with VCSH TJMZ, TJPS and TJBQ and mtn obscurations between
19/17-23Z. ESE sfc flow of less than 7 knots expected thru around
19/13Z, bcmg ESE at 10-20 knots with sea breeze variations
thereafter. Maximum winds NW 50-65 kt btwn FL 345-480 arnd 19/12Z.

&&


.MARINE...
One more day of choppy seas are expected today given the winds up to
20 knots across the local waters. Thereafter, winds will slow down
a bit and seas will stay below 5 feet. A weak northerly swell is
expected for Friday and into the weekend, but seas in the Atlantic
are still expected to stay below 5 feet. Scattered showers and
possibly some thunderstorms will be an increasing threat across
the local waters after Thursday and into the middle of next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 91 78 91 77 / 30 20 20 20
STT 88 77 88 78 / 20 20 30 40
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Re: Caribbean - Central America Weather

#20211 Postby cycloneye » Wed May 20, 2020 5:08 am

Area Forecast Discussion
National Weather Service San Juan PR
403 AM AST Wed May 20 2020

.SYNOPSIS...

Drier than normal conditions will continue, but are about to end as
we head into the weekend. Isolated to scattered showers are possible
for the next few days, but ample moisture will move in for the
weekend and next week. Coupling the moisture with strong surface
heating will lead to heavy rainfall and the potential for
localized flooding. A weak swell is expected this Thursday and
into the weekend, but seas will still stay below 5 feet.

&&


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

Post Tropical Storm Arthur 1100 miles north of San Juan and a strong
low in the north central Atlantic will force the sub tropical ridge
further south to around 25 degrees north latitude, north of Puerto
Rico and the U.S. Virgin Islands. Arthur will weaken during the
period, but not before it spins a low off of itself that runs
rapidly toward the northeast. These lows will hold the high pressure
closer to the Canary Islands and allow east to southeast flow to
continue across the local area. Moisture is patchy, but increasing
with steadily wetter patches moving through the area today and
Thursday bringing slowly increasing shower activity through
Thursday. Moisture will increase dramatically late on Friday.

500 mb temperatures continue between minus 6 and minus 7 degrees and
capping will not be sufficient to hold back local convection so have
continued with a slight chance of afternoon thunderstorms in the
west northwest portions of Puerto Rico each day. 1000-850 mb
thickness values forecast by the GFS indicate a a slight cooling
today but warming again on Thursday. We will continue to see warmer
than normal temperatures over the area with many locations in the
lower elevations reaching the upper 80s or the lower 90s each day.
Presently it looks like Thursday will be the warmest day for the
Greater San Juan Metropolitan area and the coastal plains to the
west.

At upper levels the weak cut-off low pressure will be 1150 miles
east northeast of Puerto this afternoon and is now far enough a way
as to allow a modest ridge to build over the area. A 60-85 knot jet
is approaching and will arch over the top of the ridge well to our
north. Although upper level moisture will increase somewhat and
bring increasing high clouds, mid levels will continue very dry
until late Friday such that any tall convection will be locally
driven.

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

Forecast models continue to agree on a trend towards much wetter
conditions as we approach the weekend and into the next week. As
discussed in the short term section, moisture will begin to ramp up
in the latter half of the workweek, and it will continue to increase
during the weekend. This time of year, average precipitable water
values are around 1.75 inches, and by Saturday the foreacst is for
around 1.9 inches, and around 2 inches into the middle of next week.
Just given those values, heavy showers are expected.

The important questions then are, where is the rain most likely, and
what is the potential for thunderstoms. Throughout the longterm
period, somewhat weak southwesterly flow is expected at low
levels, which will favor heavy afternoon rainfall for the interior
and northwestern sectors of Puerto Rico, as well as downwind of
El Yunque over the San Juan Metro area. Nighttime and morning
showers will favor the southeast coast of Puerto Rico and El
Yunque. However, it should not be assumed that these will be the
only locations that have a chance for heavy rainfall, and we will
get a better idea of what is expected as high resolution models
begin to extend into the weekend. As for lightning potential, it
doesn`t look great, but some of the stronger storms have the
potential to surprise. Models suggest that we will be on the
subsidence side of an upper level ridge throughout the long-term
period. However, soundings don`t really show much in the way of
warming aloft or any inversions, so clearly the ridge will not be
very impact. Generally, CAPE values stay above 1500 J/kg each
afternoon, and coupled with ample moisture and very moist
soundings, deep convection and lightning generation is possible.
However, the main story is the threat for localized flooding for
each day in the long term period.

&&


.AVIATION...

Sct SHRA ovr lcl waters, arnd the USVI and ern PR
are expected thru 20/15Z. SHRA will increase across PR with a slgt
chc of TSRA WNW PR aft 20/17Z. VCSH TJMZ, TJPS and TJBQ and mtn
obscurations in PR between 20/17-23Z. ESE sfc flow of less than 10
knots expected thru around 20/13Z, bcmg ESE at 10-18 knots with sea
breeze variations thereafter. Maximum winds NW 45-55 kt btwn FL 410-
480.

&&


.MARINE...

Winds are expected to slow down slightly beginning today, which
will help seas to become more tranquil. Thus, wave heights below 5
feet are expected for the most part. A weak northwesterly swell
is expected to begin Thursday and last into the weekend, but seas
will still be below 5 feet. Thereafter, calm seas will prevail.
However, active weather over the weekend and into the next week is
expected, so scattered showers are expected over the local
waters.

&&


.FIRE WEATHER...

Elevated fire weather conditions are expected today, though this
is expected to be a borderline case. Soil moisture remains low at
8% with KBDI values still above 700 at Camp Santiago. Furthermore,
winds will likely exceed 15 mph sustained this afternoon, and at
the same time RH values may drop into the low to mid 40s. There is
a low fire danger for the southwestern plains given low KBDI
values.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 91 77 92 79 / 20 40 60 60
STT 88 78 88 78 / 20 40 40 40

&&
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Re: Caribbean - Central America Weather

#20212 Postby cycloneye » Thu May 21, 2020 5:20 am

Area Forecast Discussion
National Weather Service San Juan PR
443 AM AST Thu May 21 2020

.SYNOPSIS...Moisture will increase rapidly Friday through Tuesday.
The strongest showers should be on Saturday, but wetter weather
is expected to become widespread for much of next week with the
possibility of urban and small stream flooding each day.
Temperatures will remain somewhat above normal due to
southeasterly flow today through Saturday.

&&

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

Forecast models continue to agree on a trend towards much wetter
conditions over the next week. Currently a mid to upper level ridge
resides over or just to the west of the region. At low levels, high
pressure continues to persist over the central to eastern Atlantic.
These features have helped to keep fairly dry conditions over the
region, and that dry air with a strong inversion at 700mb was
plainly evident in last nights sounding. Moisture from a weakening
tropical wave has moved into the Leeward Islands, but models project
a halt to the westward movement of the moisture before it arrives.
However, moisture will slowly filter in over the next few days that
will help to enhance shower activity. The influence of the ridge
and high pressure will weaken, which will weaken the aforementioned
inversion and further enhance the potential for rainfall.

Currently isolated to scattered showers are occurring over the USVI,
eastern Puerto Rico, and across the local waters. These showers will
continue throughout the morning. For this afternoon, the focus will
shift to northwestern Puerto Rico, where scattered showers and
isolated thunderstorms are expected. Model soundings for this
afternoon suggest ample dry air at mid-levels, which will be very
hostile for shower development. However, there will be plenty of
CAPE and decent lapse rates to combat the dry air. The ridge aloft
with the dry air is not helpful for lightning, but all things
considered, the atmosphere will probably produce a few lightning
strikes. With ESE to SE wind flow, a threat of rainfall exist over
the San Juan Metro area. However, it is also possible that the
line of showers forms to the west of town if the winds have enough
of a easterly component. The SE windflow will continue to cause
warm temperatures, but clouds might temper that a bit as they did
yesterday.

The potential for heavy rain increases for Friday, and even more for
Saturday. The mid-level dry air will moisten, and there will still
be CAPE over 2000 J/kg for both days. Winds look a bit lighter at
low levels for both days, which could produce more persistent
showers and a better chance for urban and small stream flooding.
Given the continuation of ESE winds, once again the best chances for
localized flooding will be in northwestern Puerto Rico and around
the San Juan Metro area. Showers downwind of Vieques could also
impact the El Yunque area.

.LONG TERM...Sunday through Thursday...
Low levels become rather moist, but precipitable water values are
over 2 inches through the end of the period. This moisture begins
in the western Caribbean early in the period and wraps south of a
ridge over Florida then back over the local area before being
pulled to the northeast by low pressure.

At upper levels the majority of the period is dominated by west
northwest flow. Low pressure over Tennessee now, will be pushing
into the western Atlantic by Sunday, gravitating toward a long
wave trough in the north central Atlantic. As it wraps around the
low early in the week it is absorbed, but this creates an
imbalance that will cause the long wave trough to spin off a
relatively strong upper level cut-off low about 1200 miles north
of Anegada Island on Tuesday. The low will move southwest and
then loop back until, by Thursday night, it is only 700 miles
north of Puerto Rico. This upper level low will help spin up a
lower level low in roughly the same places that will be
instrumental in maintaining considerable moisture in a band over
and north of Puerto Rico and the U.S. Virgin Islands during most
of next week.

Because mid levels are influenced by higher pressure to the south
despite a slightly cyclonic curvature from a low pressure
situated north northwest of the area, dynamics are not
particularly favorable, and CAPE values will not return to 2000
J/Kg until late in the period Thursday afternoon. Therefore
although shower activity will be fairly widespread it will not be
particularly robust though isolated thunderstorms should be able
to develop. Nevertheless, weaker flow across the area particularly
Tuesday through Thursday will cause the storms that do form to be
slow moving. Given this, daytime urban and small stream flooding
is likely in the western and interior portions of Puerto Rico each
day, and there is even a slight chance for urban and gut flooding
next week in the northern U.S. Virgin Islands where persistent
bands form and move north over the islands.

&&

.AVIATION...VFR conds will continue to prevail for most terminals.
However, VCSH are possible for TIST/TISX/TNCM/TKPK in the morning
hours, with southeast winds at 10 mph or less. After 21/16z
SHRA/TSRA likely in and around TJBQ, and psbly TJMZ/TJSJ also.
Winds increasing to around 15 knots with some sea breeze
variations after 21/14z.

&&

.MARINE...A weak swell will move into the area on Friday with a 14
second period. This will cause an increase in the rip current
risk along the north and north central coasts of Puerto Rico late
Friday and into the weekend, but seas will generally remain below
6 feet the entire period in all of the forecast area. In fact seas
will be 4 feet or less for most of next week after swell from
Post Tropical Storm Arthur fade away.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 92 79 92 78 / 40 30 50 20
STT 88 78 88 77 / 40 40 40 40
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Re: Caribbean - Central America Weather

#20213 Postby cycloneye » Sun May 24, 2020 5:00 am

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
454 AM AST Sun May 24 2020

.SYNOPSIS...

A TUTT low and a tropical wave will cause unsettled weather by
mid-week. Also, east to southeast winds will usher in moisture
from the Caribbean over Puerto Rico and adjacent Islands. Diurnal
heating and instability provided by the TUTT low and surface
trough will aid in the development of moderate to heavy rainfall
across Puerto Rico and the local waters. Therefore, expect urban
and small stream flooding as well as mudslides in higher terrain
during the middle of the week.

&&

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

A mid-level ridge will move south of Hispaniola today and further
away of the region during the next few days. A northwest flow aloft
will then prevail across the islands, with short wave perturbations
moving from time to time through the short term period. At lower
levels, a weak trough to our north and a surface high pressure over
the north-central Atlantic will continue to promote a mostly light
southeasterly steering wind flow across the northeastern Caribbean.
In addition, a layer of Saharan dust and drier 700 mb air will
continue over the region today, promoting somewhat stable conditions
through at least the morning hours across the islands. Normal to
above normal temperatures will continue with highs reaching the low
90s across coastal and urban areas. Steering winds are forecast to
remain light through the short term period; and the combination of
the available moisture with daytime heating and the sea breeze
convergence will result in showers and isolated thunderstorms
developing each afternoon, mainly over central and western PR. Urban
and small stream flooding as well as brief gusty winds can be
expected with this activity. Elsewhere, the potential for shower
development will increase each day as moisture pools across the
region.

&&

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

Global models continues to show an unsettled long-term period.
Tuesday, a TUTT low is forecast to develop and move near the
forecast area either late Tuesday or early Wednesday. The second
feature which will impact the local weather is a tropical wave
that is forecast to move into the Caribbean waters Wednesday
afternoon and move out of the area by late Friday.

The combination of the upper-level instability provided by
the TUTT, significant low-level moisture provided by the tropical
wave, and diurnal heating could lead to the development of
organized deep convection during the afternoon on Wednesday and
Thursday. The GFS shows conditionally unstable conditions at the
Sfc to 3 km with cape ranging from 6.4 to 6.9 C/km, and positive
cape ranging from 1400 to 2000 J/kg. Also, 500 mb temperatures are
forecast to cool to around -6.0 to -7.0 degrees Celsius Wednesday
and Thursday. Additionally, the GFS shows precipitable water
peaking to 2.2 inches on Thursday. As a result, of the above
conditions, thunderstorms were put into the forecast for Wednesday
and Thursday afternoon.

However, the development of widespread convection could
be hindered by the mid to upper-level clouds that could limit
surface heating and delay the development of convection.
Furthermore, the middle levels of the atmosphere are barely
conditionally unstable this could impede the vertical growth of
showers during the afternoon. Nevertheless, we expected moderate
to heavy rainfall, which could lead to urban and small flooding as
well as mudslides in higher terrain.

Friday and Saturday, the upper-level TUTT and surface low are
forecast to lift gradually northeast of the area; however,
lingering moisture will remain over the region. The lingering
moisture and diurnally heating will induce showers and possible
isolated thunderstorms during the afternoons. Saturday, guidance
shows a drier air mass filtering in from the east; the drier air
mass should bring a reprieve to the moderate to heavy rainfall.

Sunday, the GFS shows a patch of moisture racing across the area
from the east, and moving west of the area by late Sunday night.
The moisture will aid in the development of showers during the
afternoon across Puerto Rico and the U.S. Virgin Islands.

&&

.AVIATION...

Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, TSRA/SHRA over
central/western PR btw 18z-22z may cause tempo MVFR conds at
TJMZ/TJBQ. East to southeast winds will increase between 10-15 kt
with sea breeze variations after 14z.

&&

.MARINE...

Tranquil marine conditions are forecast over the next several
days with a few isolated showers possible. Seas will ranging from
3 to 5 feet across the outer Atlantic, and 4 feet or less over the
Caribbean waters. Winds will be from the east to southeast at 10
to 15 kts.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 92 78 90 78 / 30 30 40 40
STT 88 78 87 78 / 30 50 50 60

&&
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Re: Caribbean - Central America Weather

#20214 Postby cycloneye » Mon May 25, 2020 4:52 am

Area Forecast Discussion
National Weather Service San Juan PR
530 AM AST Mon May 25 2020

.SYNOPSIS...Diurnally induced afternoon showers and isolated
thunderstorms are expected each day, mainly over central and
western Puerto Rico. An upper level low will gradually build by
midweek just to the north-northeast of the region. At the same
time a tropical wave is forecast to move across the region and
increase low-level moisture through at least Thursday. Southeast
winds will prevail through the end of week.


&&

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

The mid-level ridge south of Hispaniola will continue to slide away
from the area today as a trough begins to deep across the western
Atlantic. As the mid-level ridge continues to move further away from
Puerto Rico, the trade wind cap will continue to weaken and allow
the mid to upper-levels of the atmosphere to moisten. At the
surface, east to southeast winds will pull moisture over Puerto Rico
and adjacent Islands this morning. Additionally, the east to
southeast winds will increase low-level moisture today and bring
precipitable water values up to 2.0 inches this afternoon. The east
to southeast wind flow and local effects will place the heaviest
afternoon shower activity in western, northwestern, and interior
Puerto Rico today through Wednesday. Also, showers that develop this
afternoon will move slowly due to light low-level wind flow. Thus,
allowing moderate to heavy rainfall to accumulate which could cause
urban and small stream flooding.

The current global models show a TUTT low developing across the
Western Atlantic on Wednesday, and a closed low just north of Puerto
Rico. The features above will keep the atmosphere unstable and
assist in shower and thunderstorm development on Wednesday.

.LONG TERM...Thursday through Monday...

By Thursday, deep tropical moisture is forecast to pool across
the region due to the passage of a tropical wave interacting with
the upper level low to our north. Precipitable water content is
currently forecast to peak around 2.25 inches by Thursday
afternoon, therefore the potential for heavy rainfall and flooding
will be high, mainly across the eastern, interior and northern
sections of Puerto Rico.

The TUTT low and an associated surface low are forecast to pull
slowly further north over the central Atlantic through the
weekend and a 700mb-500mb ridge builds from the tropical Atlantic
into the eastern Caribbean. This ridge will increase trade winds
and promote drier air at this layer. However, 500 mb temperatures
are forecast to drop at minus 8 degrees Celsius late in the weekend
into early next week. This will keep the potential for thunderstorms
to develop over the western portions of Puerto Rico in diurnal
activity each afternoon.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals until 25/15Z. Then TSRA/SHRA across terminals TJSJ,TJMZ,
TJBQ,and over central/western. TSRA/SHRA may cause tempo MVFR conds
at the above terminal sites. Sfc winds from the east to southeast
at 10-15 kt with sea breeze variations after 14z.


&&

.MARINE...Seas will continue in general at less than 5 feet for
the next several days. Light to moderate southeasterly winds will
prevail through the end of the work week. A tropical wave will
increase shower and thunderstorm activity between late Wednesday
and Thursday. There is a moderate risk of rip currents for the
eastern and northern beaches of the islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 91 78 90 78 / 40 40 40 50
STT 87 79 87 78 / 40 40 50 60

&&
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Re: Caribbean - Central America Weather

#20215 Postby cycloneye » Tue May 26, 2020 4:45 am

AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
509 AM AST Tue May 26 2020

.SYNOPSIS...Diurnally induced afternoon showers and isolated
thunderstorms are expected each day, mainly over central and
western Puerto Rico. An upper level low will gradually build by
midweek just to the north-northeast of the region. At lower
levels, a tropical wave is forecast to move across the region and
increase low-level moisture between Wednesday and Thursday. A
Saharan Air Layer is expected to move over our area during the
weekend. East to southeast winds will prevail through the long
term period.


&&

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

A wet and unsettled pattern will persist through the short-term
period. A trough will continue to deepen across the central
Atlantic, as TUTT low develops later this evening across the western
Atlantic, followed by a close low just north of Puerto Rico. The
TUTT is forecast to drift south through Thursday. The mid-level
ridge that has provided relatively stable weather will shift to the
west to southwest of Puerto Rico now through Thursday. As the mid-
level ridge moves away, it will erode the trade wind cap and slowly
moisten the mid-levels of the atmosphere. At the surface, east to
southeast winds will usher in an influx of low-level moisture over
the next several days across Puerto Rico and adjacent islands. The
low-level moisture will keep precipitable water values near 1.9 to
2.1 inches for the next several days. The GFS and EURO show modest
divergence aloft; however, low-level convergence and upper-level
instability should be enough to produce isolated thunderstorms today
and early Wednesday. Thursday scattered thunderstorms are forecast
for most of Puerto Rico and the U.S. Virgin Islands as a result of
increased instability provided by a tropical wave that will move
into the Caribbean waters.

Analysis of the skew-T for the short-term period shows the 700 to
500 MB lapse rates being conditionally unstable, and cape ranging
from 1400 to 2000 J/kg, with the higher values on Wednesday and
Thursday.

Thursday, the concern is for the possibility of flooding occurring
across Puerto Rico and the adjacent islands. At this time,
conditions are favorable as a result of light low, mid and upper-
level winds, as well as precipitable water values close to 2
standard deviations above normal due to the tropical wave. Not to
mention strong low-level forcing, and relatively weak upper-level
winds. The 72 hour precipitation total shows the highest rain
totals over northwestern Puerto Rico with rainfall amounts ranging
from 2.00 to 3.00 inches, the interior 1.5 to 2.0 inches, and the
San Juan metro area 1.0 to 1.5 inches of rain. However, the
skew-T profile shows a saturate atmosphere from the mid to upper-
levels. The relatively saturated levels could delay the initiation
of convection during the afternoon and produce light rainfall
amounts across the area.

A positive outcome is for light to moderate rainfall accumulations
for portions of northeastern, central, and southern Puerto Rico,
which are experiencing abnormally dry and moderate drought
conditions.

FORECAST CONFIDENCE: Medium.

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

A TUTT induced surface low is forecast to develop on Friday about
800 miles to our northeast and pull slowly further north over the
central Atlantic through early Monday. Meanwhile a broad surface
high pressure will build across the central Atlantic. This will
continue to promote an east to southeasterly wind flow through the
long term period. As the low pulls away, lingering moisture will
remain across the region on Friday. The 500 mb temperatures are
forecast to drop through the weekend and into early next week, as
the TUTT lingers to our north and as a polar trough amplifies
over the western Atlantic by Monday. This will continue to provide
some instability aloft for thunderstorm development in diurnal
activity each afternoon over western PR.

Having said that, a building low to mid level ridge across the
tropical Atlantic will bring a Saharan Air Layer(SAL) across the
islands during the weekend. Therefore, hazy skies are expected
during this period. Drier air filtering with the SAL will limit
rainfall activity across the USVI and the eastern sections of PR,
however, patches of moisture embedded in the trade winds will
bring the occasional passing showers across these areas through
early next week.


&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals until 26/16Z. Then TSRA/SHRA across terminals
TJSJ,TJMZ, TJBQ,and over central/western. TSRA/SHRA may cause
tempo MVFR conds at the above terminal sites. Sfc winds from the
east to southeast at 10-15 kt with sea breeze variations after
14z.


&&

.MARINE...Seas will continue in general at less than 5 feet for
the next several days. Moderate southeasterly winds will prevail
through the end of the work week. A tropical wave will increase
shower and thunderstorm activity between late Wednesday night and
through Thursday across the regional waters. There is a moderate
risk of rip currents for the eastern and northern beaches of the
islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 78 89 77 / 40 60 60 60
STT 87 78 87 76 / 50 60 60 60
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Re: Caribbean - Central America Weather

#20216 Postby cycloneye » Wed May 27, 2020 5:38 am

Area Forecast Discussion
National Weather Service San Juan PR
457 AM AST Wed May 27 2020

.SYNOPSIS...An upper level trough and a tropical wave will
increase shower activity and the potential for flooding through at
least Thursday across all islands. A Saharan Air Layer is
forecast to move across the region during the weekend. East to
southeast winds will prevail through the long term period. Diurnally
induced afternoon showers can be expected each afternoon through
next week over western Puerto Rico.


&&

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

The digging mid to upper-level trough aided in the development of
isolated thunderstorms across the Atlantic and Caribbean waters
during the overnight. Showers are forecast to continue to develop
through the rest of the morning, producing light rainfall amounts.
This afternoon the showers and thunderstorms will move to the
northwest and the northern areas of Puerto Rico. A southerly wind
flow will keep showers and thunderstorms across the northern,
central, and the metro areas of Puerto Rico. However, I can`t rule
out thunderstorms developing in other areas of Puerto Rico and the
adjacent islands, especially with moisture and instability
increasing this afternoon across most of the region. A light
steering flow will cause showers and thunderstorms to move slowly,
leading to urban and small stream flooding. Rainfall amounts of 1
to 2 inches with isolated amounts up to 3 inches fell over the
northwestern areas of Puerto Rico yesterday. If Additional rainfall
amounts of 2 to 3 inches fall across portions of northwest Puerto
Rico this afternoon, flooding will occur.

Thursday, the tropical wave talked about in the previous forecast
discussions this week, finally moves into the Caribbean waters late
tonight into Thursday. Guidance shows precipitable water peaking to
the highest total this week at 2.05 inches on Thursday morning. The
forcing provided by the mid to upper-level trough coupled with the
instability provided by the tropical wave will induce numerous
showers and thunderstorms across the region. The moderate to heavy
rainfall could cause flooding for many areas across Puerto Rico.

Friday, the wave moves west of the area; however, moisture is
forecast to linger over Puerto Rico and the adjacent islands. The
lingering moisture plus diurnal and local effects will lead to the
development of showers and thunderstorms during the afternoon.

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

A building 700-500 mb ridge over the Tropical Atlantic will
gradually move west into the eastern Caribbean and is expected to
move over the region by Thursday. A Saharan Air Layer is expected
to filter during the weekend and possibly into early next week,
creating hazy skies and limiting widespread shower activity across
the islands. A deep layered low over the central Atlantic, just
to our northeast will merge with a polar trough over the
northwestern Atlantic by early next week. This will keep 500 mb
temperatures between minus 8-10 degrees Celsius through the long
term period. At lower levels, shallow patches of moisture will
move at times and this will result in seasonal rain shower
activity across the islands, with passing showers across the USVI
and eastern PR during the overnight/early morning hours...followed
by diurnally induced afternoon convection over western Puerto
Rico each day.


&&

.AVIATION...Mostly VFR conditions expected until 27/16Z. Then
TSRA/RA is forecast across terminals TJBQ,TJMZ AND TJSJ through
27/22Z. The TSRA/SHRA could cause brief MVRF conds over the above
terminal sites. Elsewhere, Iso/sct SHRA are possible across other
areas of the island through 27/18Z. Sfc winds from the east to south
to southeast at 10 to 15 kts with seas breeze variations after
27/15Z.


&&

.MARINE...Seas will continue at less than 5 feet for the next
several days. East to southeast winds will prevail between 5-15
knots. A low to moderate risk of rip currents is expected each day
across the islands. Shower and thunderstorm activity will continue
to increase today and tomorrow across the regional waters.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 77 88 75 / 60 40 60 60
STT 88 77 87 75 / 50 60 60 50

&&
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Re: Caribbean - Central America Weather

#20217 Postby cycloneye » Thu May 28, 2020 4:52 am

Area Forecast Discussion
National Weather Service San Juan PR
359 AM AST Thu May 28 2020

.SYNOPSIS...
Unsettle conditions will continue today due to the combination of
a tropical wave and a mid to upper-level trough. Urban and small
stream flooding are possible with the strongest activity. A drying
trend is then anticipated for Friday and the weekend, along with
Saharan dust resulting in hazy skies and warm temperatures.

&&

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

Mid to upper level trough will continue become amplified across the
northeastern Caribbean today into Friday, then gradually lift
northward by Saturday while weakening across the region. In the
meantime, expect the unstable conditions aloft to combine with the
available moisture accompanying a tropical wave to promote the
development of enhanced showers and thunderstorm activity across the
region today. Rainfall accumulations are expected to cause localized
urban and small stream flooding across some sectors especially
during the afternoon hours with the most enhanced rainfall activity.
Scattered to numerous showers and isolated thunderstorms should be
focused across much of the northern and west sections of Puerto
Rico. The remainder of the islands including the U.S. Virgin Islands
should see lesser activity during the afternoon as the tropical wave
moves further west of the area.

By Friday and Saturday expect a gradual drying tend with increasing
stability aloft as the tropical wave departs the region and the
upper upper trough lifts northwards while weakening. However,
lingering moisture and the prevailing southeasterly wind flow may
still support periods of passing early morning showers, followed by
diurnally induced isolated to scattered afternoon showers each day.
The activity should be focused mainly on the west interior sections
of Puerto Rico with improving an mostly fair weather conditions
expected elsewhere and for the U.S. Virgin Islands. In addition,
recent satellite imagery along with the latest aerosol analysis and
forecast products all suggest a moderate to high concentration of
suspended Saharan dust particulates will spread across the region
trailing the tropical wave. This will again aid in promoting warmer
temperatures and hot and hazy conditions for the weekend.

.LONG TERM...Sunday through Friday...
A low to mid level ridge east of the islands will begin to
advance toward the west by the start of the next workweek. In the
meantime, a layer of Saharan dust will continue to affect the
area. These factors will combine to inhibit widespread formation
of shower and isolated thunderstorms. However, a deep layer
trough will dominate over the western Atlantic through the
workweek. This will keep temperatures at 500 mb between -7 to -9
degree Celsius. Along with the aforementioned dust, drier air at
the mid- levels will arrive. However, patches of moisture confined
to the lowest 850 mb will bring groups of showers and clouds from
time to time. As a result, still expect periods of passing
showers affecting eastern Puerto Rico and the U.S. Virgin Islands
through the overnight and early morning hours. Additionally, in
the afternoon, with the aid of local effects, showers could
develop over the interior and western Puerto Rico. Since cold mid-
level temperatures are forecast, isolated thunderstorm activity
will remain possible. At the surface, high pressure over the
eastern Atlantic will strengthen between Tuesday and Thursday,
tightening the gradient over the islands. Therefore, winds are
expected to pick-up during this time period.


&&

.AVIATION...
Prevailing VFR durg prd, except for VCSH til 28/14Z at most
terminals except TJBQ/TJMZ. SCT SHRA/Isold TSRA ovr regional waters
and en route btw Ern PR and the northern Leewards brief MVFR psbl.
SCT-BKN cld lyrs nr FL025...FL050...FL080. Few tops btw FL250-FL300
w/Isold TSRA. SHRA/Isold TSRA likely at TJBQ/TJMZ/TJSJ fm 28/17Z-
28/22Z with mostly VCSH at TIST/TISX/TNCM/TKPK. SFC winds generally
fm ESE at 5-15 mph with sea breeze variations.


&&

.MARINE...
Generally tranquil marine conditions are expected to prevail for
the next few days. However, seas could become dangerous near
thunderstorms due to strong winds and frequent lightning. In
general, seas will remain at 5 feet or less. There is a low risk
of rip currents for the islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 76 88 78 / 60 40 40 40
STT 87 77 86 79 / 50 50 40 30
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Re: Caribbean - Central America Weather

#20218 Postby cycloneye » Sat May 30, 2020 4:56 am

Area Forecast Discussion
National Weather Service San Juan PR
522 AM AST Sat May 30 2020

.SYNOPSIS...Mostly sunny, hot and hazy weather conditions are
expected today and generally through the weekend across much of
the local area as a drier air mass and a Saharan Air Layer will
spread across the region. This should limit shower activity and
afternoon convection over the islands. However, showers and isolated
thunderstorms are still expected to develop across portions of western
and northwestern Puerto Rico during the afternoon hours due to local
effects and intense daytime heating. As a result of the Saharan Air
Layer, hazy skies can be expected at least until Monday.

&&

.SHORT TERM...Today through Monday... Hazy skies are expected to
prevail through the forecast area as a drier air mass along with
Saharan dust filtered into the islands. A surface high pressure over
the eastern Caribbean is generating an east-southeast wind flow.
Under this pattern, above normal temperatures are expected to
continue. In the central Atlantic, a mid to upper level trough will
hold north of the area, while maintaining 500 mb temperatures at -7
to -8 degrees. However, precipitable water values are expected to
fluctuate between 1.3 to 1.4 inches, which is below normal. In fact,
moisture is expected to remain confined to the lower levels of the
atmosphere and will mostly depends on fragmented group of clouds
carried by the trade winds. As a result, a few passing showers
cannot be ruled out across eastern Puerto Rico and the U.S. Virgin
Islands during the overnight and early morning hours. Then, in the
afternoon, the northwestern quadrant of Puerto Rico should
experience shower and isolated thunderstorm activity, aided by the
local effects and diurnal heating. Except for isolated areas, the
activity is not expected to be as widespread and intense due to the
drier air mass over the region. A gradual increase in low level
moisture is however forecast by Monday resulting a better chance
for afternoon convection.

.LONG TERM...Tuesday through Saturday...

Recent model guidance continued to suggest a broad polar trough will
move across the western Atlantic and become amplified while sinking
southwards across the the region Tuesday through the end of the
work week. This will result cooler temps aloft with the 500 mb
temperatures to range between -8 to -10 degree Celsius. In addition
to this increasing instability aloft, a tropical wave will move across
the region Tuesday through Wednesday and therefore increase low level
moisture pooling and convergence across the forecast area. Therefore
there is increased potential for early morning and afternoon showers
and thunderstorm activity across the islands and coastal waters
at least during the early part of the period with enhanced afternoon
convection and rainfall possible over portions of the islands.

By late Wednesday through the end of the work week, a surface
high pressure ridge will build across the central and northeast
Atlantic to increase the easterly trade winds. This will tighten
the local pressure gradient over the eastern Caribbean resulting
in increasing trade winds and somewhat breezy conditions over the
islands. Consequently, expect more frequent passing overnight and
early morning shower activity to affect the east coastal areas of
the islands. The aforementioned upper trough (TUTT) is expected
to lift northeastward across the islands by Friday, accompanied by
a jet segment which will again destabilize the upper levels during
the afternoon hours. This feature along with available moisture
across the islands will increase the chance for enhanced afternoon
thunderstorms activity in and around the islands with periods of
locally heavy rains. A gradual improvement is forecast by the
following weekend as the upper trough pulls away and the pressure
gradient relaxes while local winds become more east northeast.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals. HZ due to Saharan air will reduce VIS through the
forecast period, although remaining at P6SM. After 17Z, VCTS will
affect TJBQ/TJMZ with MVFR TEMPO conditions possible. Rain should
taper off by 23Z. Winds remain out of the east southeast at around
10 knots with stronger gusts and sea breeze variation.

&&

.MARINE...Fairly tranquil marine conditions with seas ranging
between 2 and 5 feet across the regional waters through the
weekend. A moderate risk of rip currents is expected across the
northern coast of Puerto Rico as well as the northeast coast of
Culebra and the eastern coast of Saint Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 92 79 90 79 / 20 20 20 30
STT 88 79 88 78 / 10 20 30 40

&&
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Re: Caribbean - Central America Weather

#20219 Postby cycloneye » Sun May 31, 2020 5:52 am

Area Forecast Discussion
National Weather Service San Juan PR
457 AM AST Sun May 31 2020

.SYNOPSIS...
A surface high pressure across the north central Atlantic and an
area of low pressure over the central Atlantic, will maintain a
light to moderate east to southeast wind flow across the region
through Tuesday. Another surface high pressure will cross the western
Atlantic into the central Atlantic by midweek, promoting an increase
in the easterly trades winds through the end of the workweek. Few
passing clouds and trade wind showers will affect the coastal waters
surrounding the U.S. Virgin Islands and eastern PR during the rest
of the morning hours. The proximity of a lingering upper trough
along with local forcing and daytime heating will support afternoon
showers and isolated thunderstorms development mainly over the west
sections of Puerto Rico. Elsewhere mostly sunny and hazy conditions
will prevail today with only a slight chance of an isolated shower.

&&

.SHORT TERM...Sunday through Tuesday...
Saharan dust will continue across the area, resulting in hazy skies
through the short-term forecast period. A mid to upper level trough
continues over the central Atlantic, with its axis located just to
the east of the local islands. This feature is resulting in 500 mb
temperatures at -8 to -10 degree Celsius. At the mid levels, high
pressure is located to the northeast of the Caribbean, while at the
surface, a high pressure is supporting trade winds out of the east
to east-southeast. For today, precipitable water values are expected
to remain near or below normal, around 1.5 inches, trapped into the
lower levels of the atmosphere. With some support from the trough,
and in combination with local effect and diurnal heating, showers
and isolated thunderstorms should develop in the afternoon across
the interior and western Puerto Rico. Streamers may also form
downwind from El Yunque and from the U.S. Virgin Islands, Vieques
and Culebra. Due to the presence of dry air, widespread significant
rainfall accumulation is not anticipated. For Monday, a little more
moisture is expected as a patch of clouds approaches from the east.
As a result, afternoon convection is expected to cover more ground,
focusing over the interior and northwestern quadrant of Puerto Rico.
On Tuesday, a similar pattern is forecast. However, Saharan dust
concentration will somewhat diminish. In terms of temperatures, a
predominant east-southeast wind flow will cause highs above the
climatological value, surpassing the 90 degree mark for the next
several days over the coastal areas of Puerto Rico, and also near
90 degrees over the U.S. Virgin Islands.

.LONG TERM...Wednesday through Sunday...
Latest model guidance continued to suggest that the polar trough
will be reinforced across the western Atlantic and become amplified
while sinking southwards across the northeast Caribbean through Friday.
This will favor cooler temps aloft with the 500 mb temperatures
ranging between -8 to -10 degree Celsius. This instability aloft
along with moisture accompanying a tropical wave, will affect the
region through Wednesday and increase low level moisture pooling
and convergence. Therefore increased potential for more frequent
early morning and afternoon showers and thunderstorm development
can be expected across the islands and coastal waters at least
through Thursday. Some explosive and enhanced convection with heavy
rainfall will remain possible over portions of the islands each
afternoon but especially over parts of Puerto Rico.

By Thursday through the end of the work week, a surface high pressure
ridge will spread across the central and northeast Atlantic to
increase the easterly trade winds. This will tighten the local
pressure gradient over the forecast area and increase the trade
winds, resulting in somewhat breezy conditions over the islands.
Therefore expect more frequent passing shower activity over the
east coastal areas of the islands and surrounding waters during
the overnight and early morning hours. The aforementioned upper
trough (TUTT) is expected to lift northeastward across the islands
by Friday, accompanied by a jet segment which should again destabilize
the upper levels during the afternoon. This feature along with available
moisture will increase the chance for isolated areas of enhanced
afternoon thunderstorms mainly over the west sections of Puerto
Rico. A gradual improvement is forecast by the weekend and latter
part of the period as the upper trough pulls away, and the pressure
gradient relaxes while local winds become more east northeast on
Sunday then more east southeast by Monday and Tuesday.


&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals. HZ due to Saharan air will reduce VIS through the
forecast period, although remaining at P6SM. After 17Z, VCTS will
affect TJBQ/TJMZ with brief MVFR conditions possible. FL050 winds
will be out of the east at 10 to 20 knots.

&&

.MARINE...Seas will continue between 1-5 feet across the regional
waters. East to southeast winds up to 15 knots will prevail through
Tuesday , increasing to 15-20 knots by midweek. A moderate risk of
rip currents will continue across most of the northern and some
eastern and southern beaches of the islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 78 90 79 / 10 30 30 30
STT 89 79 87 79 / 20 40 20 40
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Re: Caribbean - Central America Weather

#20220 Postby cycloneye » Mon Jun 01, 2020 5:38 am

Area Forecast Discussion
National Weather Service San Juan PR
441 AM AST Mon Jun 1 2020

.SYNOPSIS...Surface high pressure across the north-central
Atlantic will maintain an east to east-southeast wind flow across
the area through mid-week. Another surface high pressure is
expected to move from the western to central Atlantic during the
second half of the week, resulting in breezy conditions. A
seasonable weather pattern is expected across the area during the
next several days with isolated to scattered brief showers
expected across portions of eastern Puerto Rico and the USVI
during the overnight and early morning hours followed by the
development of more significant shower and thunderstorm activity
across the western half of Puerto Rico during the afternoon hours
due to local and diurnal effects and an upper-level trough
overhead.

&&

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

The saharan dust and drier than normal air have moved away, and near
normal to slightly higher than normal moisture is expected for the
next few days during the daytime hours, but lower than normal
moisture is still expected during the overnight hours. For that
reason, showers and thunderstorms are expected, particularly for
western Puerto Rico each afternoon. A mid to upper level trough
is present over the local islands, and while it is moving off to
the east, putting us in the subsident side, another trough will be
moving in Tuesday, which will be favorable for producing
thunderstorms. Very cold air aloft associated with these features,
with 500mb temperatures of around -8 to -10C from Monday through
Wednesday, with Wednesday having the coolest 500mb temps. In
addition, CAPE will be between 2800 to 3600 J/kg between today and
Wednesday, with Wednesday also having the higher CAPE. As an
added detail, the Lifted Index also indicates good potential for
thunderstorms with an index of -8 to -10 from today (-8) and
Wednesday (-10). If this were to verify as the models suggest, we
will have a good chance for significant thunderstorms each
afternoon. The prevailing wind flow is east-southeasterly at low
levels today with warmer than normal temperatures continuing, but
turning more easterly on Tuesday and Wednesday.

.LONG TERM...Thursday through Monday...

A surface high pressure moving from the western to central
Atlantic will result in a tightening of the local pressure
gradient during the latter half of the work week. This will result
in breezy conditions. Moisture content for the most part is
expected to remain mostly below average during the latter half of
the work week into the upcoming weekend with precipitable water
values expected to remain at or below 1.5 inches. This will the
limit the potential for any widespread significant rainfall
activity from materializing. Nevertheless, the stronger wind flow
will result in patches of low-level moisture to move over the area
from time to time throughout the period. This will result in some
brief passing showers across portions of eastern Puerto Rico and
the USVI during the overnight and early morning hours followed by
the development of afternoon showers and isolated thunderstorm
activity across the western half of Puerto Rico due to local and
diurnal effects. In fact, the afternoon convection across western
Puerto Rico may become somewhat enhanced both on Thursday and
Friday as there will be an upper-level trough overhead, resulting
in strong instability aloft with 500 mb temperatures expected to
range between -8 and -10 Celsius. As the upper-level low lifts
away during the upcoming weekend, more stable weather conditions
are expected.

&&

.AVIATION...VFR conditions expected through 01/16Z. Thereafter,
SHRA/TSRA is expected near TJBQ and TJMZ, some of which could
affect the terminals, while ISOL/SCT SHRA is expected elsewhere,
causing brief VCSH. Winds will continue from the E-ESE at 10 to 15
knots with occasional gusts and sea breeze variations, becoming
calm to light and vrb aft 01/23Z.

&&

.MARINE...Fairly tranquil marine conditions with seas generally
less than 5 feet are expected to continue through mid-week.
Choppier seas are expected by the latter half of the work week as
winds increase. There is a moderate risk of rip currents for most
of the the north and east-facing beaches of the islands for today.

&&

.FIRE WEATHER...KBDI values across Camp Santiago and Cabo Rojo
remain above critical levels at 731 and 590, respectively. Due to
the lack of wetting rains across the southern coastal plains, 10-hour
fuel moisture continues at around 9%. Relative humidity values
are expected to briefly drop into the mid 40s and sustained winds
may peak close to 15 mph with higher gusts. Therefore, there is an
elevated fire danger for the southern coastal plains once again
for today and a Fire Danger Statement (RFDSJU) has been issued
accordingly.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 78 90 79 / 30 20 20 10
STT 87 80 88 80 / 10 30 30 40
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