Caribbean - Central America Weather

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cycloneye
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Re: Caribbean - Central America Weather

#20261 Postby cycloneye » Tue Jul 14, 2020 4:53 am

Area Forecast Discussion
National Weather Service San Juan PR
458 AM AST Tue Jul 14 2020

.SYNOPSIS...Drier air along with Saharan dust will support
relatively fair weather conditions with limited shower activity
favoring portions of southwestern Puerto Rico under a generally
east-northeast steering flow. A wet and unstable weather pattern is
expected by Wednesday and continue through the weekend as a TUTT
and associated surface induced trough, followed by an easterly
disturbance stream across the region. Both features are expected
to enhance the potential for shower and thunderstorm development.


&&

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

A vertical stack high pressure and a dry air mass will inhibit rain
activity across the islands today. Under this weather pattern,
warming will happen once again across the islands with heat indices
between 100-107 degrees Fahrenheit. African dust particles still in
the atmosphere and somewhat hazy skies. Rainfall activity, if any,
will be wind-driven during the morning, and limited afternoon
convection over the southwest quadrant of mainland PR and downwind
from the U.S. Virgin Islands.

The high pressure system will erode with the arrival of a TUTT-Low
Wednesday into the rest of the work-week. A moist air mass is
forecast to replace the current air mass. This pattern will slowly
increase the frequency of showers and thunderstorms Wednesday and
Thursday. Based on the current model guidance, a wet and unstable
weather pattern is likely after today. However, the best chance for
organized convection in the short-term seems to be late Wednesday
night into early Thursday.

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

Model guidance continues to suggest that a relative wet weather
pattern will dominate the long-term forecast period. Increased
low-level moisture and somewhat favorable conditions aloft are
expected as a retrogressive TUTT and induced surface perturbation
streams across the area by Friday. Drier air will briefly move in
by late Friday night, but an easterly disturbance and associated
plume of moisture is forecast to arrive on Saturday afternoon and
affect the area through Monday. Both features will enhance the
potential for shower and isolated thunderstorm development across
the region, following the typical seasonal shower pattern.
However, the best chance for organized convection in the long-
term is expected between Sunday afternoon and Monday afternoon
with peak moisture content around 2.0-2.2 inches and 500 mbar
temperatures ranging between -5 and -7 degrees Celsius. Drier air
will quickly move in by Monday night into Tuesday, resulting in
fair and stable weather conditions with limited shower activity
thereafter.


&&

.AVIATION...VFR conds expected across the local terminals.
Although hazy skies will continue, P6SM vis will prevail. Passing
-SHRA/SHRA will affect the terminals of JSJ/IST/NCM/KPK at times.
Because winds are from the NE, SHRA/isol-TSRA will develop over
the southwest quadrant of PR and downwind from the USVI terminals
btwn 14/17-23z. NE winds will increase at 15 to 20 knots with
higher gusts and sea breeze variations after 14/13z.


&&

.MARINE...Small craft operators are urged to exercise caution due
to choppy seas up to 6 feet and/or winds up to 20 knots across the
offshore Atlantic waters, coastal waters of southern Puerto Rico
and the Mona Passage. Elsewhere, relative tranquil marine
conditions are expected with seas up to 5 feet and winds up to 15
knots. A moderate risk of rip currents continues for beaches
along the north and south coast of Puerto Rico, eastern half of
Vieques, and most beaches in Culebra and Saint Croix.

&&

.FIRE...A Fire Danger Statement has been issue for elevated
fire danger conditions across the southern coastal plains of
Puerto Rico today. Although wetting rains are expected across
southwestern Puerto Rico this afternoon, the timing of showers
affecting the area may occur after relative humidity drop to fire
danger thresholds. Elsewhere in the southern coastal plains,
limited to no shower activity is expected with relative humidity
expected to drop into the mid 40s to low 50s today. Winds will
favor a east-northeast flow at 15-20 mph with higher gusts. Based
on the forecast and current soil/moisture conditions, elevated
fire danger criteria is expected today.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 79 91 77 / 40 50 40 60
STT 90 78 91 78 / 30 30 40 60
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Re: Caribbean - Central America Weather

#20262 Postby cycloneye » Wed Jul 15, 2020 4:56 am

Area Forecast Discussion
National Weather Service San Juan PR
512 AM AST Wed Jul 15 2020

.SYNOPSIS...A typical seasonal weather pattern with passing
showers moving over eastern Puerto Rico and the USVI, followed by
afternoon convection over western sections of the island is
expected today and Thursday. Favorable conditions aloft and an
increase in moisture content is expected enhance shower and
thunderstorm development by Friday. The next rain events are
expected during the weekend with the arrival of an easterly
disturbance and associated plume of moisture, followed by a
surface induced trough early next week.


&&

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

Satellite-derived precipitable water products shows an approaching
surge of moisture, bringing clouds and showers from the east to
northeast over the islands. Therefore, expect passing showers across
U.S. Virgin Islands, surrounding waters and the north, east and
southeast portion of PR throughout the morning. Local effects,
diurnal heating and sea breeze will allow the development of showers
and thunderstorms over the interior and southwest portion of PR and
downwind from the Virgin Islands during the afternoon. The mid- to
upper-level ridge will erode as a TUTT-Low move into the region
later today. Although the islands will be on the subsidence side of
it, the chance for thunderstorm development will increase as the
ridge erodes.

As the TUTT-Low migrates westward over the Hispanola, instability
will increase over the region. The weather pattern seems to be
more unstable and wet through at least Friday afternoon when model
guidance is suggesting the erosion of the available moisture.
That said, late Wednesday night into early Thursday afternoon
looks like the period with the best chance for convective activity
in the short term period.

.LONG TERM...Saturday through Wednesday...

Although model guidance continues to suggest that a relatively
wet and unstable weather pattern will dominate of the long- term
forecast period, drier air will support fair weather conditions
with limited shower activity on Saturday. Favorable conditions
aloft and enhanced low-level moisture convergence will elevate
the potential for shower and thunderstorm development by Saturday
evening and continuing through midweek with the passage of an
easterly disturbance through the weekend, followed by a surface
induced trough during the first part of next week. So far, the
best chance for organized convection in the long-term is expected
between Sunday afternoon and Monday afternoon with model-
estimated precipitable water peaking at 2.0-2.2 inches and 500
mbar temperatures ranging between -5 and -7 degrees Celsius.


&&

.AVIATION...Mainly VFR conditions will continue. SHRA will move
across the local flying area without impacts to operations.
SHRA/TSRA will develop and intensify over the interior and SW-PR
between 15/17-23z and could impact JPS. USVI terminals can expect
more intense SHRA during that period too. Winds will continue from
the E-ENE at 10 kt or less, and will increase between 15 and 20
kts with higher gusts and sea breeze variations after 15/13z.


&&

.MARINE...A surface high pressure north of the region will
maintain moderate winds up 15 knots. Tranquil marine conditions
with seas up to 5 feet are expected. Passing showers are expected
across the local waters today, but a higher shower frequency is
expected by Wednesday through the weekend. A moderate risk of rip
currents continues for beaches along the north coast of Puerto
Rico, as well as the eastern-most beaches of Culebra, Vieques and
Saint Croix.


&&

.FIRE...A Fire Danger Statement has been issue for elevated
fire danger conditions across the southern coastal plains of
Puerto Rico today. Recent KBDI and 10-hour fuel moisture continue
to hold within elevated to critical thresholds above 700 and
around 9-10%, respectively. Although winds are expected to
diminish today, sea breeze may enhance winds to around 15-18 mph
by the late morning into the early afternoon hours. Wetting rains
are forecast to affect the area, but this activity is expected
late in the afternoon after relative humidity drop into the mid
40s to low 50s. Based on the forecast and current soil/moisture
conditions, elevated fire danger criteria is expected today.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 79 89 79 / 30 70 60 30
STT 90 79 88 79 / 40 60 30 20
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Re: Caribbean - Central America Weather

#20263 Postby cycloneye » Thu Jul 16, 2020 4:46 am

Area Forecast Discussion
National Weather Service San Juan PR
448 AM AST Thu Jul 16 2020

.SYNOPSIS...

A TUTT-Low and a surface induce trough will increase the chance
of showers and thunderstorm formation across the islands today.
The trough aloft will linger near the Hispanola through the
upcoming weekend, increasing instability across the region.
Although brief slots of dry air will limit activity at times, a
moist and unstable weather pattern will dominate the conditions
through at least Monday next week.

&&

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

An upper-level trough and associated surface induced trough have
moved into the northeastern Caribbean, as indicated by both
satellite imagery and Doppler radar. Somewhat favorable conditions
aloft, as well as an increase in low-level moisture convergence
while surface winds gradually turn from the east to southeast, is
expected as these features cross the forecast area today. This
combination will enhance the potential for organized shower and
thunderstorm activity. Showers and possible isolated thunderstorms
will favor the eastern half of Puerto Rico and the US Virgin Islands
throughout the morning hours. As the day progresses, the bulk of the
activity is expected to focus over the northwestern quadrant of
Puerto Rico, while showers and isolated thunderstorms develop
downwind from El Yunque and the local islands into the San Juan
metropolitan area and eastern Puerto Rico in the afternoon. Since a
weak steering flow is expected, resulting in slow-moving showers and
higher rainfall accumulations, there is a potential for urban and
small stream flooding.

A similar wet and unstable weather pattern is expected on Friday.
However, conditions aloft will favor a higher potential for
organized shower and thunderstorm activity as the upper-level trough
continues to migrate further west, with its divergence side moving
over the local islands. By Saturday, model guidance suggest the
erosion of the available moisture with the entrance of drier air.
Nevertheless, locally induced convective development is still
expected, particularly over northwestern Puerto Rico in the
afternoon.

.LONG TERM...Sunday through Thursday...

The proximity of a TUTT-Low, over the Hispanola, will promote
favorable atmospheric conditions aloft on Sunday. An easterly
disturbance is forecast to move over the islands that day,
interacting with the TUTT-low and promoting the development of
showers and thunderstorms, especially during the afternoon. There
is a discrepancy between the GFS and the ECMWF in terms of the
available moisture, but conditions seem favorable for convective
activity. Although the TUTT-low will move over the Bahamas on
Monday, the available tropical moisture will be combined with
local effects to result in showery weather.

GFS is suggesting that an east-southeast wind flow will lift
tropical moisture over the region by Tuesday. Under this wind
flow, warm to hot temperatures will prevail through at least
Wednesday. Therefore, heat indices above 100 degrees Fahrenheit
will be possible. A seasonal weather pattern will prevail on
Thursday.

&&

.AVIATION...

Sfc induced trough and favorable conditions aloft will favor
SHRA/TSRA activity. TSRA/SHRA are expected at TSJU/TJPS/USVI
terminals thru 16/14Z. Then, TSRA/SHRA are expected to affect
TSJU/TJBQ from 16/16-22Z and 17/02Z, respectively. This could
result in brief MVFR conditions with SCT-BKN btwn FL020-040. VCSH
expected at TNCM/TKPK throughout the day. Light and var winds
will continue through 16/14Z, turning from the E-ESE at 10-15
knots with higher gusts and sea breeze variations thereafter.

&&

.MARINE...

Mainly tranquil marine conditions with seas between 2 and 5 feet
will prevail through the forecast period. Mariners can expect
easterly winds around 15 knots. However, local effects may
increase winds in portions of the local waters at time.

For the beachgoers, there is a moderate risk of rip currents
across the northern beaches of Puerto Rico and Culebra as well as
the eastern most beaches of Vieques and St Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 90 78 / 60 30 40 30
STT 88 79 88 78 / 30 30 30 20
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Re: Caribbean - Central America Weather

#20264 Postby cycloneye » Mon Jul 20, 2020 5:26 am

Area Forecast Discussion
National Weather Service San Juan PR
434 AM AST Mon Jul 20 2020

.SYNOPSIS...

Patches of moisture embedded in the trade winds will stream across
the area for the start of the workweek. Passing showers are
expected during the overnight and morning hours; afternoon
showers and thunderstorms are also anticipated, especially in
western and interior Puerto Rico. Conditions will become less
favorable aloft for shower development, and drier air will move in
during midweek, bringing more stable conditions. A tropical wave
is forecast to push across the region near the end of the week,
bringing an increase in showers. For the local waters, locally
choppy conditions are expected in areas where stronger winds are
seen, mostly associated with shower activity.

&&

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

An weak upper level trough located west-northwest of Puerto Rico
will continue weakening until it is replaced by another weak upper
trough by Wednesday. That said, this upper trough will cause some
instability over the local area today. There is slightly drier than
normal moisture at the moment, but slightly higher moisture will
move in over the local islands late this morning and this afternoon.
This increase in moisture will combine with the instability and
diurnal heating to cause showers and thunderstorms over the local
islands. The heaviest showers are expected to be across the
northwestern quadrant of Puerto Rico, where urban flooding can be
expected, while ponding of water in areas of poor drainage can be
expected across the north and east sections of Puerto Rico and the
USVI.

The upper trough is expected to weaken further on Tuesday. However,
the available moisture will remain near normal This moisture will be
near normal across northwestern Puerto Rico, which will help in the
development of afternoon convection. Patches of moisture will linger
over the area into Wednesday, which will cause scattered showers
across the local waters, USVI and eastern Puerto Rico in the early
morning hours, while the western sections of PR once again may
observe thunderstorms on Wednesday afternoon. It is worth noting
that the forecast models are being somewhat inconsistent in timing
and in the areas of deeper moisture, as the pattern is somewhat
disorganized. In addition, and also the different models are having
very different solutions, in particular the hi-res models, so the
forecast confidence is moderate at this time. In terms of
temperatures, the guidance insists that high temps will be in the
upper 80s, although some areas could easily surpass 90 degrees
across south and SW-PR, while the USVI will also be near 90 degrees.

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

A dry airmass is expected to be affecting the area on Thursday. Some
patches of moisture carried in, embedded on the trade winds, could
help to sustain some shower activity, including the typical
afternoon showers due to local effects and diurnal heating; however,
this activity is likely to be inhibited.

On Friday morning, a tropical wave is forecast to press into the
region. This will provide enhanced moisture levels, which, in turn,
will lead to more vigorous and widespread shower activity. That
being said, conditions aloft are not expected to be favorable for
convective activity, with a ridge dominating over the region in the
upper levels, and that will likely put an upper bound on the
increase in showers. The peak in activity will be in northwestern
and interior Puerto Rico, with a secondary peak in the east in areas
impacted by streamer development, which is likely to include the San
Juan metro area. Behind the wave, some drying is expected overnight.
The GFS has become much more zealous in bringing the secondary glut
of moisture behind the wave into our area with the more recent runs.
The dynamic setup aloft will still not be conducive for convective
development, and uncertainty with respect to moisture content is
high. Should the moisture setup not materialize for the local
islands, the normal shower activity is still likely. If the drier
air mass stays over the area and keeps the moisture to the south,
then decreasing showers would be seen. Sunday appears likely to be a
relatively dry day, and comparatively more stable and drier weather
is forecast, though local effects and diurnal heating will still
cause afternoon showers in western and interior Puerto Rico.

Another wave is forecast to follow behind the one at the end of the
workweek, around the start of the next work week. This wave will
likely arrive late Monday or Tuesday. This time, conditions aloft
will be conducive for convective development; a deep trough aloft
will help to provide instability across the area starting on
Monday. As such, the arrival of the wave will herald substantial
widespread shower activity during the early part of next week.

&&

.AVIATION...

VFR conds expected across the local terminals today.
ISOL to SCT SHRA in the morning may cause VCSH at TJSJ as well as
TIST/TISX. After 20/16Z, SHRA/TSRA could develop across NW-PR, which
could cause VCSH/VCTS at TJBQ, though they could observe MVFR conds
as the TSRA could affect the actual terminal. There is also a chance
TJSJ may observe VCSH in the afternoon hours. Winds will be mainly
easterly at around 10-15kt, with sea breeze variations and a few
gusts.

&&

.MARINE...

Seas up to around 5 feet persist across the region through the first
half of the week. Winds of up to 15 knots are anticipated for most
of the local waters, with winds to 20 knots possible, especially in
areas near the north coast of Puerto Rico. Passing showers are also
expected to continue, with isolated thunderstorms, and locally
stronger winds and higher seas are possible associated with these
showers and thundershowers. There is a moderate risk of rip currents
at beaches of northern Puerto Rico, as well as Culebra,
eastern Vieques, and St. Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 89 78 / 50 20 30 30
STT 89 79 89 79 / 50 40 30 30
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Re: Caribbean - Central America Weather

#20265 Postby cycloneye » Tue Jul 21, 2020 5:31 am

Area Forecast Discussion
National Weather Service San Juan PR
456 AM AST Tue Jul 21 2020

.SYNOPSIS...

A typical pattern of isolated to scattered passing showers during
the mornings and nights, and afternoon showers and thunderstorms,
especially in the west, is anticipated today and tomorrow. On
Thursday, drier and more stable conditions are anticipated as a
dry slot ahead of a tropical wave affects the area. The tropical
wave is forecast for Friday, and shower activity will increase.

&&

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

Widely scattered showers are affecting the local waters, USVI and
eastern PR this morning. This is due to near normal moisture and a
weak upper level low and associated trough located north and west of
Puerto Rico will move west through Wednesday. This upper trough will
cause some instability over the local area today and Wednesday.
There is a slightly drier air mass expected to move in for this
afternoon, but the available moisture, diurnal effects and marginal
instability will combine to cause some showers and thunderstorms
this afternoon, especially across the same areas that observed
significant rain yesterday, which are the western sections and some
sections of north and eastern PR as well as portions of the San Juan
Metro. The USVI will remain observing isolated to scattered brief
showers through the day. Slightly higher moisture is expected on
Wednesday, but otherwise the overall pattern is expected to be
similar, so similar rainfall pattern is expected. On Thursday, an
upper level high pressure will move just north of the local area,
stabilizing the atmosphere a little bit. There will also be drier
air moving in, ahead of a Tropical Wave that is expected for Friday.
Therefore the shower activity should be much less for Thursday
compared to Today and Wednesday.

The forecast models continue being somewhat inconsistent, and the hi-
res models are indicating much more rainfall than the global models.
That said, the hi-res models seem to be initializing a bit better
and seem to have a more representative solution, so we leaned a bit
more towards the high res models for todays`s and Wednesday`s
forecast. In terms of temperatures, the guidance continues
indicating that high temps will be in the upper 80s, although some
areas could easily surpass 90 degrees across south and SW-PR, while
the USVI will also be near 90 degrees.

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

A tropical wave is forecast to arrive by Friday morning, bringing
increased moisture to the region. An increase in shower activity
is expected, with the typical pattern of showers and isolated
thunderstorms due to local effects and diurnal heating. This
increase will be somewhat subdued, however, as conditions aloft
are expected to be unfavorable for convective development, with a
ridge in the upper levels. The tropical wave`s visit will likely
be relatively brief, as it speeds across the region, which could
further limit rainfall amounts seen from it, and conditions will
begin to dry out somewhat late in the day on Friday.

Saturday remains somewhat vexing. The GFS has once again backed
off on moisture reaching the area with the two most recent runs,
which is better supported by foreign guidance. It does still
suggest that southern portions of the forecast region will see
some moisture from this feature on Saturday, largely for the
Caribbean waters, though some southern portions of the islands and
possibly into western Puerto Rico could be impacted. Moisture
levels for the rest of the region will be near normal or possibly
just below normal. As such, the typical pattern of afternoon
showers and isolated thunderstorms and passing showers during the
overnight and morning is anticipated. Whether or not the moisture
makes it across the islands, conditions aloft are forecast to
remain unfavorable for development, which would limit somewhat
any impacts that might be anticipated.

A dry airmass is forecast to enter the region Sunday. As such,
drier, more stable weather is expected for the day. Some patches
of moisture will likely stream across the region embedded in the
trade winds, which could help sustain afternoon showers due to
local effects and diurnal heating.

Another wave is expected for Monday. Moisture associated with this
wave will help to fuel afternoon showers and thunderstorms, which
will likely be relatively widespread. Also helping to sustain this
activity is a more favorable environment aloft for convection. An
upper level low is forecast to push across the area on Sunday,
lingering over or near the area into midweek. Model guidance has
been relatively consistent with this feature and its potential
impact, though timing remains relatively uncertain; any changes to
expected arrival time of this feature over the local islands would
likely be to push it back, possibly even into the day on Tuesday.
Behind the wave, some moisture will linger, keeping precipitable
water values around climatological normal values or higher. As
such, another day of active weather is expected for Tuesday,
though slightly diminished compared to Monday.

&&

.AVIATION...

Mainly VFR conditions are expected to prevail across all
terminals. VCSH will be observed through the forecast period for
TIST and TISX, especially in the morning. VCTS/VCSH may affect
portions of TJSJ/TJBQ after 21/16Z, with brief MVFR conditions
possible at TJBQ. Winds will be from the East at 10 to 15 knots
with a few gusts and sea breeze variations.

&&

.MARINE...

Seas of up to 5 feet continue across the local waters for the
first half of the week. Associated with a ridge to the north,
moderate to locally fresh winds persist across the area as well.
Locally stronger winds are also possible with showers. Seas are
forecast to build to around 6 to 8 feet late this week due to a
wind surge associated with a tropical wave, due to arrive on
Friday. There is a moderate risk of rip currents today at beaches
along the north coast of Puerto Rico, as well as eastern beaches
of St. Croix, Vieques, and Culebra.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 79 88 78 / 40 40 40 30
STT 89 78 89 78 / 30 40 40 40
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Re: Caribbean - Central America Weather

#20266 Postby cycloneye » Wed Jul 22, 2020 5:02 am

Area Forecast Discussion
National Weather Service San Juan PR
527 AM AST Wed Jul 22 2020

.SYNOPSIS...

Similar conditions are expected today as we saw yesterday. Local
effects and diurnal heating will lead to the development of
showers and thunderstorms, especially in northwestern and interior
Puerto Rico, with streamers likely to affect areas in the east,
including portions of the San Juan Metro. More stable weather
conditions are expected tomorrow, followed by a tropical wave
bringing an increase in showers.

&&

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

Widely scattered showers are affecting the local waters, USVI and
eastern PR this morning. This is due to near normal moisture and a
weak upper level low and associated trough located north and west of
Puerto Rico will remain west of the local area through Thursday.
This upper trough will continue causing some instability over the
local area today and Thursday. There is near normal moisture and the
available moisture, diurnal effects and marginal instability will
combine to cause showers and thunderstorms this afternoon,
especially across the western sections and across portions of the
San Juan Metro. The USVI will remain observing isolated to scattered
brief showers through the day, but improving weather in the
afternoon. Slightly drier air mass is expected on Thursday, but a
brief patch of moisture will move through on Thursday afternoon,
which will help in the local development of showers and
thunderstorms over PR. A narrow band of moisture is forecast to move
though on Friday, although narrow, it does have deep moisture, and
the latest guidance has showers and isolated thunderstorms over the
local islands, including the USVI early on Friday, then eastern
Puerto Rico by the late morning and early Friday afternoon, then
western PR on Friday afternoon.

The forecast models continue being somewhat inconsistent with its
moisture patterns, and the hi-res models continue to indicate more
rainfall than the global models. That said, the past few days we
have observed areas with significant rainfall, so we kept the high
POPs for this afternoon. In terms of temperatures, the guidance
continues indicating that high temps will be in the upper 80s,
although some areas could easily surpass 90 degrees across south and
SW-PR, while the USVI will also be near 90 degrees.

.LONG TERM...Saturday through Wednesday...

A relatively dry airmass is expected to be in place over the area,
and moisture levels are forecast to be below normal. There will be
patches of moisture carried into the region, embedded in the trade
winds, which will aid in the development of afternoon showers. On
the whole, however, conditions will be relatively dry and stable.

The forecast for Sunday is much less certain. What happens on Sunday
is heavily dependent on what happens with Tropical Depression 7. The
system is forecast to be a tropical storm by the time it passes by
the area, well to the south; the forecast track puts it about 300
miles away, at closest. While the track forecast has high certainty,
the intensity forecast is much the opposite, and has quite low
certainty, especially by this weekend. There is the potential that a
stronger storm could cause more significant impacts for the area.
One notable possibility is that the storm could push moisture
northward, bringing it to the local islands. A weaker storm, though,
would have very little in the way of impacts for the CWA. With it
looking likely that conditions aloft will be favorable for
convective development, and the likelihood that at least some
patches of moisture make their way across the islands, widespread
shower activity seems a reasonable expectation at this time. Until
there is better certainty with respect to how strong the tropical
cyclone will be when it passes by the region, the confidence for
what we will see here for the weekend is going to remain fairly low.
It is worth noting that, at this time, we are not expecting direct
impacts from this system here.

A wave is forecast to push its way into the region by Monday
morning, bringing enhanced moisture to the area. Conditions aloft
will also be favorable for convective development; the upper level
low remains in place over the area, and there is some troughing in
the mid-levels, as well. As such, there will be an increase in
passing showers during the overnight and morning hours, and
widespread shower activity is expected for the afternoon, with
isolated thunderstorms likely. This will continue through much of
the night, followed by a dry slot that briefly dries out the area on
Tuesday morning, before a large patch of moisture streams into the
region during the second half of the day. Shower activity will be
diminished on Tuesday, especially during the early part of the day,
though there will remain sufficient moisture to support the typical
shower activity during the afternoon. The arrival of the moisture
will lead to an uptick in passing showers during the late evening
and into Wednesday morning. Lingering moisture during the afternoon
on Wednesday should also help to support afternoon showers,
especially in northwestern and interior Puerto Rico, with the
typical pattern placing the peak activity there bolstered by the
moisture lingering a little later in the day there.

&&

.AVIATION...

Mainly VFR conditions are expected to prevail across all
terminals through 22/16Z. VCSH will be observed through the forecast
period for TIST and TISX, especially in the morning. VCTS/VCSH may
affect portions of TJSJ/TJBQ/TJPS after 22/16Z. Winds will be from
the East at 10 to 15 knots with a few gusts and sea breeze
variations.

&&

.MARINE...

Seas of up to 6 feet are anticipated through tomorrow. A wind
surge ahead of a tropical wave will lead to building seas, and
hazardous conditions are expected starting tomorrow night. Winds
up to 20 knots are expected for portions of the local waters, and
locally stronger winds are possible in areas affected by showers.

It is worth noting that, due to uncertainty in the forecast
strength of Tropical Depression 7, that there is some uncertainty
in the forecast seas for Sunday. A stronger storm could bring a
brief period of higher seas to the region as it passes by, well to
the south.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 78 88 79 / 30 40 50 50
STT 89 78 90 81 / 30 40 30 40
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Re: Caribbean - Central America Weather

#20267 Postby cycloneye » Thu Jul 23, 2020 4:38 am

AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
441 AM AST Thu Jul 23 2020

.SYNOPSIS...Upper trough will continue to promote instability
aloft through the end of the week. The forecast for Sunday and
Monday is heavily dependent on Tropical Storm Gonzalo. Regardless,
the trajectory and intensity of Gonzalo, there is an increasing
potential for squally weather conditions as well as hazardous
marine conditions. Residents and visitors should closely monitor
the progress of this system.

&&

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

Variably cloudy skies and isolated to scattered passing trade
wind showers will continue to affect the regional waters as well
as parts of the north and east coastal sections of the islands
through the early morning hours. This is due to the interaction of
a weakly induced low level trough moving across the region, along
with the proximity of an upper level trough which will linger
across the forecast area through early Friday, before shifting
just west of the region. This upper trough will continue to
promote instability aloft through today and into early Friday.

For the rest of today, expect sufficient available moisture to
combine with local and diurnal effects and the instability aloft to
produce enhanced afternoon showers and possibly isolated thunderstorms,
especially across the western sections and portions of the San Juan
Metro. The USVI may also experience some brief afternoon showers
in isolated areas as well, but mostly improving weather is forecast
for the afternoon hours in those areas. By Friday afternoon, a slightly
drier airmass is expected to filter in across the region. However,
occasional patches of moisture will continue to move through the
region steered by the increasing trade winds, as a surface Atlantic
high pressure will remain anchored across the central Atlantic.
This pattern will aid in the development of afternoon showers and
possibly thunderstorms mainly over Puerto Rico. In addition, on
Friday a wind surge and accompanying band of moisture is to quickly
sweep though the region. This will also provide sufficient instability
for showers and isolated thunderstorm development over the local
islands, including the USVI.

By late Friday into Saturday, condition are forecast to gradually
improve as a slot of drier air will cross the region in advance of
the approaching Tropical Storm Gonzalo which at this time is forecast
to approach and cross the southern Windward Islands into the southeast
Caribbean late Friday night through Saturday. Therefore, on Saturday,
local and diurnal effects will still lead to the development of brief
early morning and afternoon showers in and around the islands. The
overall shower activity should however be of short duration as
the overall steering winds are forecast to increase during that
time, resulting in lesser rainfall accumulation.

.LONG TERM...Sunday through Friday...

The forecast for Sunday and Monday is heavily dependent on Tropical
Storm Gonzalo. Based on the latest forecast from the National
Hurricane Center, the system is forecast to move over the
Caribbean waters at about 250 miles south of the local islands on
Sunday. There is a higher than normal degree of uncertainty in
terms of the intensity forecast as the cyclone moves over the
Caribbean waters. Therefore, the confidence for what we will see
across the local islands remains low. At this time, the mostly
likely scenario is expected to be hazardous marine conditions as
well as squally weather conditions across the Caribbean waters and
the local passages late Sunday into early Monday. Squally weather
could reach as well the outlying islands and the east and south
coast of Puerto Rico. Additional moisture is forecast to push its
way into the region on Tuesday. Therefore, regardless the
trajectory and intensity of Gonzalo, there is an increasing
potential for a wetter pattern with periods of showers and
thunderstorms as well as hazardous marine condtions early next
week. Residents and visitors should monitor the progress of this
system. A seasonable weather pattern is then expected to prevail
across the local islands Wednesday onwards with trade wind showers
across the US Virgin Islands and eastern Puerto Rico during the
overnight and early morning hours, followed by locally induced
afternoon thunderstorms across western Puerto Rico each day.

&&

.AVIATION...VFR conds will prevail at all terminals durg prd.
However, Isold-SCT passing SHRA/-SHRA can be expected across the
regional waters with VCSH at most TAF sites til 23/14Z. VCTS/VCSH
will be psbl at TJSJ/TJBQ btw 23/16Z-23/22Z. SFC Wnds will be fm
East at 10 to 15 knots with ocnl hir gusts and sea breeze variations
aft 23/14z.

&&

.MARINE...Winds and seas are expected to deteriorate tonight into
Friday as a tropical wave approaches local islands along with a
wind surge. Based on the latest forecast from the National Hurricane
Center, Tropical Cyclone Gonzalo is expected to move across the
Caribbean waters and south of the local islands on Sunday. Therefore,
hazardous marine conditions will continue to prevail with seas up
to 8 feet and squally weather conditions possible the upcoming
weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 89 80 / 40 50 50 30
STT 90 81 88 82 / 30 40 40 40
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Re: Caribbean - Central America Weather

#20268 Postby cycloneye » Sat Jul 25, 2020 5:21 am

Area Forecast Discussion
National Weather Service San Juan PR
557 AM AST Sat Jul 25 2020

.SYNOPSIS...

Improving weather conditions is expected across the region
today as drier air and an area of Saharan Dust will moves filter
in across the region. However, the trade winds will continue to
increase due to a wind surge moving across the region in response
to the tightening of the local pressure gradient as the Atlantic
high pressure ridge reestablishes north of the area. Based on the
latest Tropical Storm Advisory, Tropical storm Gonzalo is projected
to pass well to our south, and is now expected to pass as a Tropical
depression. There is still the possibility that some peripheral moisture
associated with this feature may make its way northwards across the
forecast area, producing periods of passing shower and thunderstorm
activity by Sunday into Monday mainly over the offshore waters.

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

Mostly clear skies prevailed across the local islands during the
overnight hours with a few sprinkles noted over the local waters.
The overnight low temperatures ranged from the upper 70s to around
80 degrees at lower elevations. Winds were from the east at 10 MPH.

A mid to upper level ridge will prevail across the forecast area
through at least Sunday. A retrogressing TUTT is then expected to
enter the northeast Caribbean late Sunday into Monday. At lower
levels, a surface high pressure across the central Atlantic will
continue to promote brisk easterly winds.

Latest guidance continues to suggest precipitable water near the
normal range today and tomorrow, increasing above 2 inches by
Monday. Therefore, a seasonable weather pattern is still expected
through the weekend with trade wind showers across the US Virgin
Islands and eastern Puerto Rico as well as afternoon thunderstorms
across the western sections of the island. Hazy skies will continue
to prevail throughout the day today due to suspended African dust
particles. Breezy. The latest forecast from the National Hurricane
Center shows Gonzalo staying well south of the forecast area on
Sunday. The main impact of this system should be hazardous marine
conditions with showers and thunderstorms moving over the Caribbean
offshore waters. Nevertheless, the chance for shower and
thunderstorm activity is expected to increase on Monday as the
increasing moisture combines with the retrogressing TUTT.

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

Moisture advection and instability is forecast to increase across
the forecast area Tuesday through Wednesday accompanying a tropical
wave and induced low level trough. This moisture combined with a
retrogressing TUTT entering the northeast Caribbean will promote
periods of showers and thunderstorms across the local islands,
particularly across the interior and western sections of Puerto
Rico and west end of the USVI during the afternoon hours. Thereafter,
drier air and more Saharan dust will filter in across the region
,leading to a more seasonable weather pattern on Thursday. However,
this is so far expected to quickly change by Friday and into the
following weekend, as recent model guidance continued to suggest
the approach of a vigorous tropical wave across the eastern Caribbean.
Some development of this system is still possible when it reaches
the western tropical Atlantic. If this pattern unfolds, expect a
very moist and unstable weather pattern with good potential for
widespread convection during the latter part of the period. This
however is still some ways out and confidence so far is low due to
inconsistencies in the model guidance. Therefore, until then expect
trade wind showers across the US Virgin Islands and eastern Puerto
Rico during the overnight and early morning hours as well as isolated
to scattered afternoon showers and thunderstorms mainly across western
Puerto Rico each day during the early part of the period. Breezy
conditions is expected for much of the upcoming work week. Stay
tuned.

&&

.AVIATION...VFR conds are expected to prevail at all TAF sites
through the forecast period. Winds will continue from the E at
around 10-15 knots, increasing 15-20 knots with higher gusts and
sea breeze variations aft 25/13z.

&&

.MARINE...Mariners can expect rough seas between 6 and 8 feet
across the expose waters, and choppy seas between 2 and 5 across
the protected waters. The winds will continue between 15 and 20
knots across most of the regional waters and local passages.
Therefore, small craft advisories will be in effect for most of
the local waters and passages, small craft operators should
exercise caution elsewhere. A high risk of rip currents is
expected for the north- facing beaches of Puerto Rico and Cramer
Park in St Croix, while a moderate risk exist for most of the
remaining local beaches.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 81 88 78 / 40 40 20 50
STT 92 80 89 79 / 40 40 20 50
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Re: Caribbean - Central America Weather

#20269 Postby cycloneye » Sun Jul 26, 2020 5:15 am

Area Forecast Discussion
National Weather Service San Juan PR
416 AM AST Sun Jul 26 2020

.SYNOPSIS...Mostly fair weather and hazy conditions are expected
across the region through today, as Saharan dust and a drier airmass
will linger across the forecast area. Afternoon shower development
is still however expected mainly over central and southwest sections
of Puerto Rico,with lesser activity forecast for the U.S. Virgin
Islands. By late Monday through Tuesday an easterly wave will move
across the region and increase the chance for showers and thunderstorm
activity over the islands. By Friday and into the weekend, a strong
tropical wave(Invest- 92L) is still forecast to further develop over
the Tropical Atlantic and approach the region based on recent model
guidance and the overall weather pattern. Stay tuned to future forecast
and updates on this feature in the upcoming days.

&&

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

A retrogressing TUTT is expected to enter the northeast Caribbean
late tonight into early Monday. Meanwhile ridge aloft is expected to
hold. Precipitable water is still expected to increase across the
forecast area by late Monday as an easterly perturbation reaches the
forecast area. At lower levels, a broad surface high pressure across
the central Atlantic will continue to yield easterly winds 15 to 20
knots with occasionally higher gusts.

As a result, no major changes were introduced to the short term forecast.
Continue to expect a seasonable weather pattern through Monday with trade
wind showers across the US Virgin Islands and eastern Puerto Rico as
well as afternoon thunderstorms across the western sections of the island.
Hazy skies will continue to prevail throughout the day today due to
suspended African dust particles. Breezy. The chance for shower and
thunderstorm activity is expected to increase on Monday night into Tuesday
morning as moisture associated with the easterly disturbance combines with
the retrogressing TUTT. This will result in frequent passing showers and
isolated thunderstorms across the outlying islands and eastern Puerto
Rico Monday night into Tuesday morning, spreading across western Puerto
Rico in the afternoon hours. There is an increasing potential of urban
and small stream flooding.

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

Moisture advection and instability aloft is forecast to erode and
diminish by Wednesday as the aforementioned easterly wave is
expected to exit the region as a drier air mass and a low
concentration of Saharan dust will filter in across the region.
This will lead to a seasonable weather through a least early
Thursday. However by Thursday afternoon an into the following
weekend, conditions are still forecast to rapidly change as
recent model guidance continued to suggest the approach of a
vigorous tropical wave across the northeastern Caribbean. Further
development of this system is still quite possible as is moves
across the Tropical Atlantic where conditions appear to be favorable
at this time. There still remain uncertainties as to the intensity
and track of this feature. However, if in fact this pattern unfolds,
expect a very moist and unstable weather environment across the
forecast area, with high potential for widespread convection and
heavy rainfall during the latter part of the period at least through
Saturday. This however is still some ways out and model guidance
is expected to chance and adjust as the feature crosses the Tropical
Atlantic. In the meantime, will continue to closely monitor and
make the necessary adjustments in the forecast during the next few
days. Until then, expect the seasonal trade wind showers across
the U.S. Virgin Islands and eastern Puerto Rico during the overnight
and early morning hours, followed by isolated to scattered
afternoon showers and thunderstorms mainly across interior and
west sections of Puerto Rico and parts of the U.S. Virgin Islands
during the early part of the period. Breezy conditions are so far
expected to continue for much of the upcoming work week.

&&

.AVIATION...VFR conds are expected to prevail at all TAF sites
through the forecast period. Winds will continue from the E at
10-15 knots, increasing 15-20 knots with higher gusts and sea
breeze variations aft 26/13z.

&&

.MARINE...Hazardous and rough marine conditions due to a wind
surge will continue through the morning hours but will gradually
improve throughout the day. Choppy seas will however continue
through most of the period, with seas between 5 to 7 feet and
winds up to 20 knots over portions of the regional waters and
local passages. Small craft advisories are in effect for most of
the local offshore waters and passages, Small craft operators
should exercise caution elsewhere. Marine conditions a forecast to
again deteriorate by the end of the work week due to the an
approaching tropical wave. Please refer to the latest Coastal
Waters Forecast (CFWSJU) and Marine Weather Message (MWWSJU)
issued by the the NWS WFO San Juan PR.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 78 88 80 / 30 40 20 60
STT 90 80 91 81 / 30 40 50 60

&&
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Re: Caribbean - Central America Weather

#20270 Postby cycloneye » Mon Jul 27, 2020 6:03 am

Area Forecast Discussion
National Weather Service San Juan PR
501 AM AST Mon Jul 27 2020

.SYNOPSIS...A seasonable weather pattern will prevail across the
local area for today, with some passing showers across eastern
areas during the morning hours followed by the development of
afternoon convection across western PR. A tropical wave will move
over the area late tonight into early Tuesday resulting in an
increasing shower and isolated thunderstorm activity. Then, a
vigorous tropical wave with a high probability of tropical cyclone
development will be near the vicinity by the second half of the
work week.

&&

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

An upper level low about 600 miles north northeast of San Juan,
Puerto Rico with a reflection at mid levels will come to within 425
miles tonight and Tuesday. Temperatures at 500 mb will drop to below
minus 7 degrees by Tuesday. The low is forced to the west northwest
by an approaching tropical system on Wednesday.

A vigorous, but narrow tropical wave is now near 59 west
longitude. Its moisture is expected to reach the U.S. Virgin
Islands by tonight at 28/00Z and Puerto Rico about 3 hours later.
Lower level moisture will last about 24 to 27 hours. The moisture
from the wave will move out of the area overnight on Tuesday. Both
the GFS and the ECMWF have low pressure around 12 north and between
42 and 44 degrees west longitude. The ECMWF does not develop this
low very much and causes it to pass through the northern Windward
Islands by 12Z Wednesday and across Puerto Rico overnight Wednesday
as an open wave with considerable rain. The GFS is forecasting a
strong tropical storm to develop and move to the north of the
Leeward Islands by 12Z on Thursday. The ECMWF solution would bring
the most rain to Puerto Rico and the U.S. Virgin Islands and some
fresh and gusty winds, likely beginning the afternoon and evening of
Wednesday. The GFS delays most the rain until Thursday. Our current
forecast calls for significant rain to begin Wednesday night with
urban and small stream flooding possible--mainly in eastern Puerto
Rico and possibly in the U.S. Virgin Islands.

There is a chance of thunderstorms with the first wave passage, but
considerable warming occurs at 500 mb afterwards, so thunderstorms
may be confined to western Puerto Rico on Wednesday. Thunderstorms
are expected today and Tuesday in western and interior Puerto Rico
due to local effects.

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

A very active long term period appears to be on tap. The
aformentioned tropical wave located halfway between the west
coast of Africa and the Lesser Antilles is being monitored by the
National Hurricane Center for tropical cyclone development. At
this time, the wave has been given an 80% chance of development
during the next 2 days and a 90% chance of development during the
next 5 days. As mentioned, this system is expected to track west
to west-northwestward into the Lesser Antilles and the northeast
Caribbean and will be near the vicinity of the local area during
the second half of the work week. Model guidance, however,
continues to diverge greatly on the intensity and track of this
system. For instance, the GFS model develops this wave into a
fully bonafide tropical storm with a track north of the area
while the ECMWF model, on the other hand, barely develops this
wave into a tropical cyclone with a track just south of the area.
The eventual track of this system will be crucial in determining
how significant the impacts will be. With the system tracking just
south of the region as the ECMWF model suggests, widespread very
heavy rainfall activity with some significant flooding would
occur. With the system tracking north of the region as the GFS
model suggests, the heaviest rainfall activity would stay north of
the local islands with the local islands experiencing the outer
bands. This scenario would result in not as much rainfall. Due to
the significant divergence in the model guidance, uncertainity is
very high of how impactful this system will be over the local
area. Therefore, please continue to monitor the latest forecasts
during the next couple of days as the model guidance reach a
consensus.

Weather conditions are expected to improve by the upcoming weekend
as the system moves away, with a return to a more typical diurnal
weather pattern. Model guidance is indicating that another strong
tropical wave could impact the area early next week, bringing
additional heavy rainfall activity.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
the terminals during the next 24 hours. However, SHRA/TSRA are psbl
aft 27/21Z with periods of MVFR conds mainly for CIGs. SHRA/TSRA
expected to develop over western PR btw 27/16z-22z which may cause
tempo MVFR conds across the western terminals of PR. East winds will
continue and increase to 15-20 kt with higher gusts by 27/14Z thru
27/22z. Maximum winds NW 25-35 kt btwn FL385-480.

&&

.MARINE...Choppy seas between 3 and 6 feet are expected across the
local waters during the first half of the work week, with the
highest seas expected across the offshore waters and local
passages. Marine conditions are expected to become hazardous by
the second half of the work week with increased seas and winds as
a vigorous tropical wave with a high chance for tropical cyclone
formation moves over the eastern Caribbean.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 80 89 80 / 30 60 60 30
STT 87 81 88 81 / 40 60 60 30

&&
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Re: Caribbean - Central America Weather

#20271 Postby cycloneye » Wed Jul 29, 2020 5:37 am

Area Forecast Discussion
National Weather Service San Juan PR
359 AM AST Wed Jul 29 2020

.SYNOPSIS...Weather conditions will be gradually deteriorating
throughout the day as a vigorous tropical disturbance, with a high
probability of becoming a tropical storm later today, continues
to approach the area. Widespread heavy rains and winds up to
tropical storm force are expected, with the heaviest activity
expected overnight tonight and Thursday. As the tropical
disturbance moves away by Friday, weather conditions are expected
to improve. Another active tropical wave may affect the area late
Sunday and Monday.

&&

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

At upper levels, high pressure is ridging in from the northeast
and pushing a low further north. This high is associated with the
outflow from the strong tropical disturbance that will pass
through the area Wednesday night. This high will be in place just
to the north of the forecast area at the end of the period.

The lower and mid levels of the atmosphere are dominated by a strong
tropical disturbance, with winds up to 35 knots in the last
scatterometer pass and winds of up to 60 knots at 700 mb. This
disturbance, which up to now has been highly elongated and without
any discernible center of circulation typical of tropical storms,
has its strongest winds in its northern quadrant. In this
configuration the best convective activity, and there has been
considerable and consistent lightning activity, is advancing at
about 20-25 knots toward the local area with the convection about
150 miles northwest of the axis of the disturbance.

The GFS delays the formation of a solid circulation until Thursday
night when the center begins spinning just north of Hispaniola. The
ECMWF has a broad but transient circulation developing later this
afternoon in the eastern Caribbean.

The GFS brings the best moisture over the area early Thursday
morning (30/09Z). And, although the GFS shows better rainfall well
to the northeast of the area, it also carries substantial rain
amounts in southeast flow that night. This still bodes well for
heavy and prolonged rain fall Wednesday night and Thursday morning
with storm totals estimated to be 3 to 6 inches with isolated areas
of 10 inches. For this reason we will continue the flash flood watch
for Puerto Rico and the U.S. Virgin Islands Wednesday night through
Friday morning.

Winds are generally east or northeast ahead of the tropical
disturbance, but will become southeast as it passes through
Wednesday night. Since 500 mb temperatures will remain between minus
3.5 and minus 5.5 through beyond Friday, thunderstorms outside of
the main convective area associated with this disturbance will be
isolated, even as they now are both ahead and behind the main
convection area ahead of the axis of the disturbance.

Moisture is expected to decrease rapidly from peak values of over
2.6 inches after tonight and continue to diminish through late
Friday night, nevertheless precipitable water values will remain
above 1.7 inches during the period. Showers will also decrease
considerably in area and coverage on Friday.

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

A return to a more seasonable weather pattern is expected on
Saturday with rainfall activity expected to be limited to the
western half of Puerto Rico due to afternoon convection. An
active tropical wave is expected to affect the area late Sunday
through Monday with an increase in shower and thunderstorm
activity. In addition, an upper-level low north of the area could
aid in enhancing the activity. Weather conditions will improve
for both Tuesday and Wednesday of next week as the tropical wave
and the upper-low lift away and a drier air mass moves overhead.
However, afternoon convection is still possible across western
Puerto Rico due to local and diurnal effects. Latest model
guidance is indicating that for the latter half of next week a
retrogressing upper-level low will be moving over the area. If
model guidance is correct with this scenario, then enhanced
afternoon convection is possible, especially across the western
half of Puerto Rico.

&&

.AVIATION...The tropical disturbance will bring SHRA/TSRA over/near
NCM/KPK, producing BKN/OVC btwn FL015-FL030. MVFR/IFR or even worse
conds are likely with the strongest activity. SHRA/TSRA will begin
at USVI/E-PR around 29/16z, and they will slowly increase in
coverage/intensity thru the rest of the period. IST/ISX/JSJ can
expect MVFR/IFR conditions. Inclement wx will increase after 29/18z,
and continuing until at least 30/12z. Expect E/NE winds at 10-15
kt increasing at 30-40 kt with higher gusts after 09/16z.

&&

.MARINE...Marine conditions will rapidly deteriorate through the
day as the tropical disturbance approaches the area with seas
greater than 10 feet, with up to 18 feet possible across the
offshore Atlantic waters along with Tropical storm force winds.
As a result, life threatening rip currents, localized coastal
flooding and beach erosion are possible across most of the beaches
of Puerto Rico and the USVI. Please refer to the Coastal Hazards
Message (CFWSJU) and Coastal Waters Forecast (CWFSJU) for more
information.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 77 86 77 / 100 100 100 50
STT 90 79 86 82 / 90 100 90 40
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Re: Caribbean - Central America Weather

#20272 Postby cycloneye » Thu Jul 30, 2020 8:53 am

Area Forecast Discussion
National Weather Service San Juan PR
355 AM AST Thu Jul 30 2020

.SYNOPSIS...Tropical Storm Isaias will continue west northwest and
is expected to be north of Hispaniola by this afternoon. A minor
tropical wave will move through the area on Saturday followed by
another weak disturbance on Sunday night. East southeast flow will
then bring warmer than normal temperatures to the northeast coast
with patches moisture spawning showers and afternoon thunderstorms
for the remainder of next week.

&&

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

Rainbands with heavy rain associated with Tropical Storm Isaias
will continue to affect most of Puerto Rico through the morning
hours, with the heaviest accumulations expected across the
southern and eastern half of Puerto Rico. These rainbands will be
capable of producing winds gusts as high as 50 mph. In addition,
the most persistent rainbands will also be capable of producing areas
of flooding. Across the USVI, occasional rainbands will also be
possible through the morning hours, however, the activity should
not be as widespread there as it will be across Puerto Rico. By
this afternoon into this evening, as Isaias continues to move
away, rainfall activity will gradually diminish across the area.

Much more tranquil weather conditions are expected on Friday as much
drier air moves over the area. Therefore, shower activity is
expected to be limited. Winds will also be lighter. Afternoon
convection cannot be ruled out across northwest Puerto Rico due to
local and diurnal effects.

A band of low-level moisture will move over the area on Saturday.
This will result in some passing showers over eastern PR and the
USVI during the morning hours followed by the development of
afternoon convection across western PR. However, the mid to upper-
levels will be dominated by a ridge, therefore, any afternoon
convection that develops is not expected to be intense.

.LONG TERM...Sunday through Saturday...
The TUTT low that digs down into the Atlantic northeast of Puerto
Rico moves west, but stays north of the forecast area in the
latest run. After it passes on Sunday, high pressure moves into
the area Monday and Tuesday. Another TUTT develops in the western
tropical Atlantic and sweeps through the Caribbean sea adjoining
Puerto Rico late Wednesday and Thursday followed by weak high
pressure on Saturday.

The tropical wave that follows Isaias, will be exiting the area
by early Sunday morning, but will be followed closely by a
disturbance presently near 40 degrees west longitude. It is
expected to brush by the area Sunday night. East southeast to
southeast flow follows this disturbance Monday and Tuesday with
precipitable water values from 1.8 to 2.2 inches. After Tuesday
patches of good moisture move through surrounded by slightly below
normal moisture. These east to southeast winds will also bring
warmer than normal temperatures to the Greater San Juan and
Bayamon metropolitan areas

Sunday through Wednesday 500 mb temperatures range from minus 5 to
minus 6.5 providing the back drop for modest thunderstorms to
develop in the patchy moisture. Some warming occurs Wednesday and
Thursday, but 500 mb temperatures return to even lower values
afterwards. These thunderstorms will be mainly in western and
interior Puerto Rico during the afternoons. Isolated nocturnal
thunderstorms are also possible over the local waters.

&&

.AVIATION...SHRA/TSRA activity and BKN/OVC ceilings with areas of MVFR
conds and mtn obscurations will continue across all terminals
through at least 30/18z due to rainbands associated with Tropical
Storm Isaias with improvements expected across the Leeward Islands
and USVI terminals afterwards and across PR terminals after
30/22z. Winds will be from the ESE- SE between 15 and 25 kts with
peak gusts as high 45 kts in the rainbands.


&&

.MARINE...Tropical Storm Isaias has strong winds that extend well
away from its center and these winds have generated seas of 22-23
feet at Buoy 41043 just north of our outer Atlantic waters winds
and seas will begin to improve as TS Isaias move west northwest
and away from the local area this morning. Small craft advisory
conditions are expected to end early Saturday morning. The second
of the next several waves to pass through the area may bring
sufficient winds to bring a brief episode of 7 foot seas to our
northern local outer Atlantic waters on Sunday night.

&&

.HYDROLOGY...Several rain bands from TS Isaias have entered
southern Puerto Rico. Since these have been fairly fast moving,
accumulations have generally not yet brought anything more than
ponding in poorly drained areas and as of 4 AM AST were less than
one inch. At this time river and streams have been able to handle
the run-off without rising above normal flows. Nevertheless,
additional rainfall will likely cause some rivers to approach
bankfull in southeast and central Puerto Rico this morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 78 91 79 / 100 70 20 30
STT 87 82 89 79 / 90 60 20 40
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Re: Caribbean - Central America Weather

#20273 Postby tolakram » Thu Jul 30, 2020 9:10 am

How's PR handling the rain?
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Re: Caribbean - Central America Weather

#20274 Postby cycloneye » Thu Jul 30, 2020 9:26 am

tolakram wrote:How's PR handling the rain?


A good deal of flooding going on and some dams are being open their doors to let water go. So far no fatalities.

 https://twitter.com/ACUEDUCTOSPR/status/1288815745485414400


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Re: Caribbean - Central America Weather

#20275 Postby cycloneye » Fri Jul 31, 2020 5:32 am

Area Forecast Discussion
National Weather Service San Juan PR
503 AM AST Fri Jul 31 2020

.SYNOPSIS...A tropical wave will move north of the area on Sunday
with some of its moisture affecting Puerto Rico. A tropical
disturbance moving north of the area will pull up some moisture on
Tuesday for additional showers. Only patch moisture is expected
Wednesday through Friday of next week.

&&

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

Much more tranquil weather conditions are expected today across the
area. Drier air behind the moisture field of Hurricane Isaias will
significantly limit shower activity. However, some afternoon
convection can still be expected across portions of western and
northwestern Puerto Rico due to local and diurnal effects.
Localized urban and small flooding is still possible in northwest
and interior Puerto Rico due thunderstorms from lingering
moisture and strong daytime heating. An increase in shower
activity is expected for Saturday as a weak trade wind
perturbation crosses the region. This could result in some passing
showers in and around the USVI and eastern Puerto Rico during the
morning hours followed by afternoon convection across the
northwestern quadrant of Puerto Rico. However, conditions aloft
are that not favorable for any enhanced activity due to a ridge.

On Sunday, a tropical wave currently located about 1000 miles
east of the Lesser Antilles is expected to move northeast of the
area with some of the moisture associated with the wave affecting
the area. Conditions aloft will turn more favorable as an upper-
level low retrogresses to a position north of the Islands.
Therefore, afternoon convection is expected to be more enhanced
with the heaviest expected across the northwestern quadrant of
Puerto Rico.

.LONG TERM...Monday through Friday...

At upper levels a TUTT low north of the area will move west and a
ridge will move in Monday night for a brief stay. Currently the
GFS shows an upper level low forming in the western tropical
Atlantic Monday night. It will move into the Caribbean south of
the area Tuesday and Wednesday and into the central Caribbean on
Friday.

A tropical disturbance will form east of the area on Sunday and
move northwest across 20 north. The tail of this moisture may
affect the local area Sunday. This same system also appears to
pull up moisture out of South America to arrive on Tuesday for an
area-wide increase in showers and a return to southeast flow and
slightly warmer temperatures. Somewhat drier conditions are
expected Wednesday through Friday, but patches of moisture will
provide the necessary ingredient for scattered showers and
afternoon thunderstorms especially on Wednesday when 500 mb dip
to as low as minus 7 degrees.

&&

.AVIATION...Mainly VFR conditions expected to prevail during the
forecast period. Sct SHRA and a few TS may affect western and
northwestern PR between 31/16z and 31/22z. Winds will continue from
ESE at less than 10 kts, increasing to around 15 kts with some
higher gusts and sea breeze variations after 31/14z.

&&

.MARINE...Seas have subsided considerably and all small craft
advisories are expected to be down by 8 PM AST tonight. Seas are
expected to remain below 7 feet Saturday and next week. East to
east southeast trade winds will continue.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 91 79 93 79 / 20 30 60 20
STT 89 79 89 80 / 20 40 40 30
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Re: Caribbean - Central America Weather

#20276 Postby cycloneye » Fri Jul 31, 2020 5:57 am

Very high rainfall totals.

Image
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Re: Caribbean - Central America Weather

#20277 Postby cycloneye » Sat Aug 01, 2020 4:56 am

Area Forecast Discussion
National Weather Service San Juan PR
443 AM AST Sat Aug 1 2020

.SYNOPSIS...
A surface trough will move across the area today, enhancing
moisture levels over the area. This will aid in the development of
showers and thunderstorms in the afternoon across western Puerto
Rico. Since soils are saturated, any additional rain could lead to
flooding and mudslides. Additional showers are expected as an
active tropical wave moves north of the area on Sunday and Monday.

&&

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

A retrogressing upper level low will continue to weaken the upper
level ridge to our northwest today and hold through the short term
period. This will let a weak surface trough currently over the
Leeward Islands to cross the region today. In addition, a short wave
trough associated to the low is forecast to move later this
afternoon to enhance the diurnally induced convection, mainly over
the western interior and northwestern sections of Puerto Rico. As
soils are saturated across these area, any heavy rainfall could
trigger mudslides and localized flash flooding as well as rapid
river rises. Across the rest of PR, under a 10-15 kt E-ESE steering
wind flow and PWAT near 2 inches, expect showers that develop over
El Yunque area around noon to stream over portions of the eastern
interior and over the SJU metro area. Somewhat drier conditions are
expected overnight.

For Sunday and Monday, an active tropical wave is forecast to bring
an increase in moisture across the northeastern Caribbean. Guidance
suggest that this wave could develop into a tropical depression and
NHC is currently giving a medium chance of development in the next 5
days but near 0 percent during the next 48 hours. Regardless, as the
upper level low moves west of the area and low-level moisture
increases over the region, expect showers and thunderstorms to
develop each afternoon over portions of the interior and northwest
quadrant of PR. Scattered showers and isolated thunderstorms could
develop over the Anegada Passage and the Atlantic waters as the wave
moves close to the region, with some reaching portions of the USVI
and eastern sections of PR between Sunday night and early Monday
morning.

.LONG TERM...Tuesday through Saturday...
A deep layer trough will be positioned north of the islands, while a
cut-off low moves across the islands on Tuesday and Wednesday. This
is expected to cool down temperatures at 500 mb between -7 to -8
degrees Celsius. A relatively tranquil pattern is expected to
prevail through the long-term forecast period. On Tuesday, a
tropical system well north to the area will continue to pull
moisture over the area. However, this moisture will be replaced by a
drier air mass that will filter from the east on Wednesday. In
facts, the guidance is showing precipitable water value falling from
1.7 on Tuesday to 1.2 inches on Wednesday. However, due to
instability aloft and local effects, showers and thunderstorms are
expected to form, especially over the interior and western Puerto
Rico in the afternoon hours. By the end of the workweek, a few
easterly perturbations are forecast to advance into the area,
bringing an increase in showers and isolated thunderstorms to the
area.


&&

.AVIATION...Mainly VFR conditions expected to prevail during the next
24 hours. However, SHRA/TSRA over western PR this afternoon could
cause tempo MVFR conds at TJBQ. Elsewhere, mostly VCSH expected.
East winds at 10-15 kts with sea breeze variations and higher gusts
aft 14z.


&&

.MARINE...
Seas are still choppy today across the offshore Atlantic and
Caribbean waters and the passages, up to 6 feet. Conditions are
expected to improve by tonight. A moderate rip current risk
continues for most of the local beaches, except for western Puerto
Rico.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 93 79 90 79 / 50 30 20 40
STT 89 80 88 80 / 50 50 50 50
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Re: Caribbean - Central America Weather

#20278 Postby cycloneye » Sun Aug 02, 2020 5:38 am

Area Forecast Discussion
National Weather Service San Juan PR
455 AM AST Sun Aug 2 2020

.SYNOPSIS...
Unsettled weather conditions are expected to continue today with
showers developing this afternoon over western Puerto Rico and off
El Yunque across the San Juan metro area. A tropical wave will
move to the northeast of the area later today and tomorrow,
adding more moisture to the forecast area.

&&

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

An upper level low will promote unstable conditions today across the
region. This will enhance afternoon showers and thunderstorms over
central and west-northwest PR. Also, under a weak to moderate ESE
steering wind flow, showers developing off el Yunque will move over
nearby municipalities into the San Juan area. This afternoon
rainfall activity over mainland PR could lead to urban and small
stream flooding as soils continue to be saturated. A tropical wave
currently east of the Leeward Islands is forecast to move west-
northwest through early in the week. This wave has the potential to
develop into a tropical depression by midweek as it moves north of
the region. However, moisture associated to this wave and a deep
southeasterly wind flow will cause shower and thunderstorm activity
to develop along the north-central and northwestern sections of PR
each afternoon. Across the USVI, scattered shower activity is
possible in early morning convection and isolated thunderstorms are
expected to remain mainly offshore across portions of the Anegada
Passage and the offshore Atlantic waters.

.LONG TERM...Wednesday through Sunday...
At the upper levels, a cut-off low approaches from the east on
Wednesday, crossing the islands by Thursday. This will result in 500
mb temperatures cooling down to about -8 degree Celsius. At the
surface, however, moisture is lacking with precipitable water values
ranging between 1.3 to 1.4 inches. Then, by late Wednesday into
Thursday, an easterly perturbation is expected to reach the islands,
hence increasing the available moisture and the potential for
showers and thunderstorms. Therefore, expect a better chance of rain
on Thursday, with passing showers affecting the eastern half of
PR/USVI early in the day, followed by additional activity developing
over western Puerto Rico in the afternoon, due to instability aloft
and local effects. By the end of the week and into Saturday, a
tropical wave and another easterly perturbation are expected to
approach the area, with another round of showers forecast to affect
the local islands, but then again, mainly enhancing afternoon
activity over the area. On Sunday, as another mass of drier air
filters in, weather conditions are expected to improve with limited
shower activity anticipated.


&&

.AVIATION...Mainly VFR conditions expected to prevail during the next
24 hours. However, SHRA/TSRA over western PR this afternoon could
cause tempo MVFR conds across the western terminals. Elsewhere,
mostly VCSH expected. Low level winds will continue east-southeast
will prevail at 10-15 kts with sea breeze variations and higher gusts
aft 14z.


&&

.MARINE...
Seas up to 5 feet with winds up to 15 knots are expected across
most of the local waters. Conditions should remain relatively
tranquil for the next several days. For the beaches, a moderate
rip current risk continues for the northern coast of Puerto Rico.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 79 91 80 / 30 40 40 50
STT 89 81 88 81 / 50 50 50 30
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Re: Caribbean - Central America Weather

#20279 Postby cycloneye » Tue Aug 04, 2020 5:33 am

Area Forecast Discussion
National Weather Service San Juan PR
443 AM AST Tue Aug 4 2020

.SYNOPSIS...An upper level low will move just to our south on
Wednesday and linger over the region through Friday. A weak Saharan
Air Layer(SAL) and drier air will continue to filter today and
tomorrow across the region. A trough associated to the upper level
low should increase afternoon convection on Thursday. A tropical
wave will bring additional shower and thunderstorm activity across
the islands on Friday and through Friday night. Another SAL with
drier air is expected during the weekend.


&&

.SHORT TERM...Today through Thursday...
A mid-level ridge will hold north of the region through Wednesday,
while an upper level low approaches from the east to be positioned
just south of the islands at least through Thursday. At the surface,
a drier air mass has filtered in from the east. Satellite-derived
precipitable water products show values dropping to near 1.5 inches
today, while an even drier air mass is expected tomorrow. However,
small patches of moisture will cause a few showers over eastern
Puerto Rico and the U.S. Virgin Islands early in the day, followed
by afternoon convection, especially over northwestern Puerto Rico.
Additionally, some Saharan dust is forecast to turn skies hazy
through the short-term forecast period.

In terms of temperatures, a tropical wave well to the north of the
region and a surface high pressure will continue to induce
southeasterly winds today. As a result, highs will soar into the low
and mid-90s, but with heat indices ranging between 100 to 106
degrees in low elevations areas. By tomorrow, the wind flow will
shift more from the east, easing heat indices a bit, but still
approaching the 100 degree mark.

Then, on Thursday, a mid-level trough develops north of the area.
Moisture is expected to increase a bit too as small patches of
clouds move over the islands. This should result in an enhanced
chance of shower and thunderstorm development, especially during the
afternoon hours over western Puerto Rico.

.LONG TERM...Friday through Tuesday...
A tropical wave is expected to enter the eastern Caribbean on
Friday and move across the local area between Friday afternoon
into Saturday morning. This wave will increase shower and
thunderstorm activity across the islands and local waters,
especially across the eastern and Caribbean waters as it
interacts with the mid to upper level trough to our northwest.
Urban and small stream flooding is expected with the heaviest
showers on Friday. As the wave exits the region on Saturday
morning, showers and thunderstorms are expected to develop once
again over portions of central and western PR due to lingering
moisture. At the same time, a Saharan Air Layer with drier air
will move over the region and promote more stable conditions
through at least Tuesday. Another tropical wave is forecast to
increase shower activity by late Tuesday night into Wednesday.


&&

.AVIATION...Mainly VFR conditions are anticipated through the
forecast period. TSRA could result in TEMPO groups across TJBQ
after 04/16Z due to reduced VIS and low ceilings. VCSH will be
possible at TJSJ also. Low level winds will be out of the
southeast at 10 to 15 knots.

&&

.MARINE...Seas are forecast to range between 3-5 feet in general
across the regional waters through the end of the week, with seas
up to 4 feet across the western waters of PR. East to southeast
trades will continue between 5-15 kts for the next several days.
Locally higher winds are expected across the offshore Atlantic
waters today. A moderate risk of rip currents will continue mainly
for the north and east facing beaches of PR and St. Croix.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 93 79 89 78 / 40 20 30 30
STT 90 80 90 79 / 30 30 40 40
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Re: Caribbean - Central America Weather

#20280 Postby cycloneye » Wed Aug 05, 2020 5:17 am

Area Forecast Discussion
National Weather Service San Juan PR
253 AM AST Wed Aug 5 2020

.SYNOPSIS...An upper level low will move today over the eastern
Caribbean and linger over the region through Friday. A tropical
wave will move quickly on Friday, increasing shower activity
across the islands. A mid to upper level ridge with a weak
Saharan Air Layer will promote more stable and drier conditions
during the weekend. Another tropical wave is forecast to move
across the region by midweek next week.


&&

.SHORT TERM...Today through Friday
An upper level low is currently located over the Lesser Antilles and
will be moving over the local islands today into Thursday. At the
mid-levels, there is a ridge to the north holding over the area. At
the surface, satellite imagery confirms a mass of drier air already
filtering from the east. Saharan dust is embedded in this air mass,
which should turn skies a bit hazy. Under this pattern, rainfall
activity should be confined to afternoon convection due to local
effects and diurnal heating, which should result in showers and
isolated thunderstorms over western Puerto Rico. Due to the limited
moisture, only moderate amounts of rain are expected.

Since the tropical wave that moved north of the area on Tuesday lost
its influence over the local winds, a more easterly flow was
established. As a result, temperatures are not expected to be as
hot, but highs will still approach the 90 degree mark, with heat
indices near 100 degrees.

Conditions are expected to change on Friday, as a tropical wave
approaches the islands. Although this feature does not look too
strong at the moment, the increase in moisture should result in
showers affecting the eastern half of the forecast area during the
daytime, and then additional activity developing over western
Puerto Rico later in the day.

.LONG TERM...Saturday through Wednesday...
Lingering moisture associated with a tropical wave passage across
the islands will aid in the development of diurnally induced
afternoon showers between the USVI and eastern PR, as well over
the western sections of PR. Trade winds are forecast to increase
as a surface ridge builds just north of the region. A Saharan Air
Layer with drier air will move during the weekend and promote
more stable and fair weather conditions across the islands.
However, the combination of the available low-level moisture with
daytime heating and local effects will cause afternoon showers to
develop, mainly over western PR each day through Tuesday. For
Wednesday, latest guidance indicates that precipitable water
content will increase near 2.25 inches, as a broad tropical wave
moves across the region. Therefore, showers and isolated
thunderstorms are expected to increase through the day across the
local waters and over portions of the islands.


&&

.AVIATION...Mainly VFR conditions are expected to prevail through
06/06Z. VCSH are expected to affect TJSJ and TJBQ after 06/16Z with
brief reduction in VIS and low ceilings possible. Some HZ due to
Saharan dust is expected today, but VIS will remain P6SM. Low level
winds are expected from the east today, at 10 to 15 knots.


&&

.MARINE...Relative tranquil marine conditions are expected through
the end of the workweek, as seas between 2 and 5 feet and winds
up to 15 knots prevail across the regional waters. There is a
moderate risk of rip currents for the northern beaches of Puerto
Rico and eastern beaches of St. Croix. Winds and seas will
increase during the weekend, but they are expected to remain below
small craft advisory criteria.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 78 89 78 / 20 40 40 20
STT 90 79 89 79 / 20 40 40 20

&&
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