Caribbean - Central America Weather

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cycloneye
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Re: Caribbean - Central America Weather

#20721 Postby cycloneye » Wed Jan 12, 2022 4:51 am

Area Forecast Discussion
National Weather Service San Juan PR
427 AM AST Wed Jan 12 2022

.SYNOPSIS...A patchy weather pattern will prevail, with
intermittent patches of shallow moisture and relatively drier air
streaming across the area. Somewhat favorable upper-level
conditions during peak higher moisture and/or daytime heating
periods will enhance shower and possible thunderstorm activity.
Thus, increasing the potential for ponding of water to localized
urban and small stream flooding. A southerly component in the
general wind flow will result in above-normal seasonal
temperatures by the end of the workweek into early next week.


&&

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

The mid- to upper-level ridge will continue to erode as a short wave
trough crosses the west Atlantic just north of the area. This will
create an unstable divergent pattern aloft today through Thursday.
This increased instability along with cooler 500 millibar
temperatures will aid in enhancing the advective morning showers
over the regional waters and also during the afternoon hours in
isolated areas.

A stalled cold frontal boundary will continue to cross into the west
central Atlantic and gradually weaken, as a high pressure ridge will
build across the west and southwest Atlantic. This pattern will
induce a weak surface trough across the northeast Caribbean and
consequently induce a light northeasterly wind flow. This in turn
will continue to transport occasional patches of shallow moisture
across the region from time to time during the next several days.
However, the local steering winds are forecast to become more east-
southeast later today, then south-southeasterly by Thursday into
Friday.

The available pockets of moisture along with local effects and the
instability aloft, will aid in afternoon shower development mainly
over the central and west to northwest sections of Puerto Rico.
There is also a chance isolated thunderstorms later in the afternoon
and therefore areas of locally heavy rains may cause minor ponding
of water on roads and in poor drainage areas today.

Increased potential of early morning and afternoon shower activity
is expected on Thursday into Friday, resulting in scattered to
numerous showers over the region. There is also increased potential
for thunderstorm activity due to the proximity of the upper trough,
with isolated thunderstorms possible each afternoon. With winds more
east-southeasterly, expect the most likely affected areas to be the
north central to northwest and interior sections of Puerto Rico,
with a chance of minor Urban and small stream flooding in isolated
areas. Some brief afternoon showers will also be possible in and
around the U.S. Virgin islands, but significant accumulations and
flooding is so far not anticipated over the islands. By Friday, with
the low level steering flow forecast to become more south-southeast,
isolated to scattered showers will be likely in and around parts of
the San Juan metro areas as well, However widespread rainfall
accumulations and significant flood impacts are still not
anticipated at this time.

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

The most recent model guidance suggests a generally east to
southeast wind flow dominating the long-term forecast period,
supported by a surface high pressure extending into the
northeastern Caribbean. A slightly drier pattern is also
suggested, with low-level moisture convergence driving patches of
moisture across the area and model-estimated precipitable water
vapor ranging between 1.2 and 1.4 inches through late Monday
night. After that, a set of easterly disturbances will increase
the available moisture, with precipitable water values peaking
around 1.5 inches by Monday night and gradually increasing to 1.6
inches by Wednesday into Thursday.

The bulk of the resulting shower activity should remain over the
local waters, but evening-early morning showers will over southern
and eastern sections of the local islands at times. Afternoon
convective development should be limited. However, somewhat
favorable conditions aloft, with 500 mbar temperatures between -7
and -10 degrees Celcius, during peak daytime heating and/or
higher moisture periods could result in enhanced showers and
possible isolated thunderstorm activity across portions of the
interior into western and northern sections of the local islands.
Thus, an increase in the potential of ponding of waters to
localized urban and small stream flooding is likely, especially
with the afternoon activity during the weekend and Wednesday
onwards. A southerly component in the general wind flow could
result in above-seasonal temperatures early next week.


&&

.AVIATION...VFR conds at all terminals with SCT ocnl BKN lyrs nr
FL025...FL050...and wdly sct SHRA ovr regional waters and en route
btw the local islands til 12/14Z. Mtn top obscr psbl ovr E PR til
12/14Z due to low clds and -SHRA. SHRA expected ovr wrn PR and VCTY
TJMZ/TJBQ/TJSJ fm 12/16Z-22Z. Sfc winds calm to lgt/vrb bcmg fm E-NE
10-15 kts with some hir gusts and sea breeze variations aft 12/14Z.
Low/lvl wnds fm NE BLO FL200...then backing and bcmg fm WSW and incr
w/ht. Max wnds of 60-70 kts btwn FL330-450.


&&

.MARINE...Light to moderate east to northeast trade winds will
prevail today, becoming light and more southerly to southeasterly
on Thursday and Friday. Seas will remain at 5 feet or below
through the workweek, but a small northerly swell will cause
choppy seas up to 6 feet during the upcoming weekend. Brief
isolated to scattered showers will affect the local waters at
times.

There is a high risk of rip currents for beaches across the north
coast of Puerto Rico, while a moderate risk remains in place for
most of the remaining local beaches.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 72 84 74 / 30 40 30 30
STT 85 74 85 75 / 30 50 50 40

&&
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Re: Caribbean - Central America Weather

#20722 Postby cycloneye » Thu Jan 13, 2022 5:13 am

Area Forecast Discussion
National Weather Service San Juan PR
528 AM AST Thu Jan 13 2022

.SYNOPSIS...
Mid to upper level trough crossing the west central Atlantic and
extending across the northeast Caribbean, will continue eastward
while weakening. A frontal boundary with associated shearline
moisture will shift farther east but remain well north of the
region. Meanwhile, surface high pressure ridge remains the dominant
feature across the central Atlantic and will continue to extend
southward into the northeastern Caribbean. This will maintain
light to moderate southeasterly winds today and through the end
of the week. Fragments of tropical moisture along a low level
convergent zone will cross the area today. This will favor periods
of passing clouds with occasional showers across the region. The
overall southerly flow will favor slightly warmer daytime highs at
least today and Friday.

&&

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

A broad low level high to the east will yield a generally light to
locally moderate southeasterly wind flow up to 15 mph this morning,
veering more to the south-southwest this afternoon into Friday.
Under this flow, a patch of above-normal seasonal moisture, with
satellite-estimated precipitable water values up to 1.6 inches, will
continue to stream across the forecast area, but the changing
steering flow will keep the bulk of the moisture over eastern Puerto
Rico and the US Virgin Islands. As a result, isolated to scattered
showers will affect these areas throughout the day. The combination
of favorable conditions aloft with cooler than average mid-level
temperatures, forcing due to daytime heating and local effects, and
near- to above-normal moisture levels will support afternoon showers
and possible isolated thunderstorm development. Southerly winds
combined with sea breeze convergence will place the bulk of the
afternoon activity over the interior and northern sections of Puerto
Rico. At the same time, showers may also develop downwind from the
local islands and El Yunque. Given the expected weak steering flow,
moderate to locally heavy rains from slow-moving showers could lead
to ponding of water on roadways and poorly drained areas to possibly
localized urban and small stream flooding.

Even lighter winds of 10 mph or below are expected later on Friday
into Saturday morning. Yet, somewhat drier conditions and limited
shower activity are anticipated, with model-estimated precipitable
water values falling to around 1.2 inches. As a pre-frontal trough
settles to the north, enhanced low-level moisture convergence will
again bring moisture levels to above-seasonal normals, remaining at
1.4 to 1.5 inches through the weekend. Since winds will gradually
become more east to southeast, this trend will support afternoon
convective development across the interior to northwestern Puerto
Rico, followed by evening-early morning showers over eastern Puerto
Rico and the Virgin Islands through late Saturday night. A southerly
component in the general wind flow will promote warmer than average
temperatures, with daytime highs peaking into the upper 80s to
nearly 90 degrees and overnight lows falling into the mid-70s across
coastal areas.

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

The most recent model guidance suggests continued to suggest a
generally east to southeast wind flow prevailing during the forecast
period, dominated by a surface high pressure ridge extending into
the northeastern Caribbean. However a weakly induce low level trough
will linger across the region on Sunday to favor low level moisture
convergence and chance for early morning and afternoon shower
activity. This may lead to minor ponding of water on roads and in
poor drainage areas but should be mainly over portion of the
interior and northwest sections of Puerto Rico and on the west-
end or downwind of the U.S. Virgin Islands. A slightly drier
pattern is forecast by late Sunday through Monday and possibly
into early Tuesday, with decreasing moisture pooling expected as
the tradewinds increase across the area. Model guidance estimated
precipitable water values to range between 1.0 to 1.5 inches by
Monday therefore lesser shower activity is expected.

By late Tuesday and through the Thursday, models suggest increasing
instability aloft as the upper ridge erodes, and an induced surface
trough crosses the region in response to a frontal boundary approaching
the region. By then precipitable water values are forecast to range
between 1.5 to 1.8 inches, suggesting better chance for nocturnal
showers and afternoon convection across portions of the islands
and local waters, with potential for isolated thunderstorm development
and minor urban flooding in isolated areas. While most of the shower
activity should remain over the local waters, late evening and early
morning showers will affect the south and east coastal sections at
times and may produce periods of moderate to locally heavy rains.
Afternoon convective development should be focused over parts of
the central and west sections of Puerto Rico. Thus, an increase in
the potential for ponding of waters to localized urban and small
stream flooding will be likely, especially with the afternoon activity.
Condition will gradually improve and return to a more seasonal and
drier weather pattern by Friday with lesser morning and afternoon
convection expected.

&&

.AVIATION...Mainly VFR conditions are expected. However, increased
cloud cover and SHRA could result in brief MVFR conditions across
the USVI and Leeward Islands through at least 13/22Z. Afternoon
TSRA/SHRA could also result in MVFR conditions across most PR
terminals between 13/14-22Z. Surface winds will remain light and
variable through most of the day, increasing to 10-15 knots due to
sea breeze variations between 13/14-22Z.

&&

.MARINE...Mariners may experience passing showers and isolated
thunderstorms across the local waters for the next few days. Local
buoys continue to suggest a slowly subsiding northerly swell.
However, models continued to suggest yet another small NNW swell
arriving across the local Atlantic waters later this morning. Winds
will have a more southerly component today and persist through at
least the upcoming weekend. Winds will be up to 15 knots over the
offshore waters and passages with seas up to 6 feet over the
offshore Atlantic waters. The next significant swell event is
forecast to reach our local waters on Monday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 72 86 73 / 40 20 50 40
STT 81 73 82 74 / 40 40 30 20
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Re: Caribbean - Central America Weather

#20723 Postby cycloneye » Fri Jan 14, 2022 5:22 am

Area Forecast Discussion
National Weather Service San Juan PR
434 AM AST Fri Jan 14 2022

.SYNOPSIS...
Recent Satellite imagery and the Nws Doppler weather radar suggests
a south southeasterly steering flow as patches of low level moisture
and few showers were being lifted northwards across the region. Most
of the showers were now focused between eastern Puerto Rico and the
U.S. Virgin Islands with some brushing parts of the islands from
time to time. The upper level ridge continued to erode as a short
wave trough and associated frontal boundary crosses the western
Atlantic. The southerly winds will become fairly light today but
is expected to become more easterly and slightly increase by Sunday.
Limited afternoon convection is expected over the islands, but should
be focused mainly over the central interior and north- northwest
sections of Puerto Rico. Marine and surf zone conditions will again
deteriorate by Sunday into early next week.

&&

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

Low pressure in the western Atlantic is expected to develop
explosively as it moves north northeast during the next 24 hours.
The col between this low and the one over Colombia will move
northeast through the Mona Channel and will mark the southern extent
of the cold front which will technically not reach Puerto Rico or
the U.S. Virgin Islands. In fact the airmass around the area will
remain fairly homogenous with minor variations of moisture in the
flow moving through the area that will provide a decent environment
for the growth of moderate to heavy showers that will move slowly
across the area. This could provide up to half an inch in local
areas in west northwest Puerto Rico, the southeast coast and may
even provide a some rain for Saint Croix. Low level winds in this
pattern remain mostly south until late tonight. Late Saturday they
become easterly, but by Sunday afternoon east southeast winds return
at least through Monday. High temperatures reached 86 degrees in San
Juan Thursday afternoon, and with a spike in thickness values and a
continuation of very light southerly flow, expect that temperatures
could be a degree warmer on the north coast of Puerto Rico today
even if only briefly. This warming trend may even be reflected in
slightly warmer temperatures area-wide today. When the winds shift
back to the east this should allow temperatures to be slightly
cooler again on Saturday.

At mid and upper levels, the atmosphere remains mostly dry. High
pressure at 500 mb remains east of the area as a ridge which yields
southwest flow for the forecast area. At upper levels a ridge slowly
builds over the area at the expense of the ridge to our east, but
conditions are still dominated by high pressure there as well. This
will limit the chance of thunderstorms for the time being, but have
left a slight chance over western Puerto Rico today through Sunday.

.LONG TERM...Monday through Saturday...

Model guidance continued to suggest a dominant east to southeast
wind flow to prevail during the forecast period as a surface high
pressure ridge will remain anchored across the central Atlantic while
extending southwards over the northeastern Caribbean. On Monday and
at least into early Tuesday a slightly drier pattern is forecast with
decreasing moisture expected as the tradewinds increase across the
area and precipitable water values range between 1.0 and 1.5 inches.
Therefore, lesser shower activity is forecast except for a nocturnal
showers over the local waters and mainly on the windward side of
the islands. This will be followed by limited afternoon showers over
land areas.

By late Tuesday and through Thursday, models suggest increasing
instability aloft as the upper ridge gradually erodes in response
to a polar trough crossing the Atlantic, and an induced surface
trough crosses the region. This is in response to a frontal boundary
and associated shearline approaching the region. By then precipitable
water values are forecast increase to between 1.5 to 1.8 inches
across the forecast areas, suggesting better chance for more frequent
nocturnal showers and afternoon convection across portions of the
islands and local waters. The potential for isolated thunderstorm
development and minor urban flooding in isolated areas will increase
mainly over the interior and west sections of Puerto Rico during
the afternoon hours. While model guidance continue to suggest that
most of the low level moisture and shower activity should remain
over the local waters, late evening and brief early morning showers
may still will affect the south and east coastal sections at times.
As a result periods of moderate to locally heavy rains in isolated
areas cannot be ruled out. Afternoon convection should continue
to be focused over parts of the central interior and west sections
of Puerto Rico most of the period.

Condition will gradually improve and return to a more seasonal and
drier weather pattern by Friday and Saturday with lesser morning and
afternoon convection expected, as the local surface pressure gradient
loosens and the upper ridge gradually builds in across the
region.

&&

.AVIATION...Mainly VFR conditions are expected. However, increased
cloud cover and SHRA could result in brief MVFR conditions across
the USVI through at least 14/22Z. Afternoon TSRA/SHRA could also
result in MVFR conds across the wrn PR terminals btwn 14/17-22Z.
Surface winds will remain light and variable through most of the day
as sea breezes and southerly flow battle for influence. Winds will
become 10-15 knots btwn 13/14-22Z. Max winds WSW-W 75-100 knots btwn
FL350-480.

&&

.MARINE...Light to moderate southeasterly to southerly winds will
prevail into the weekend. Another northerly swell will arrive and
spread across the Atlantic waters and local passages Sunday and
into early next week. This will again deteriorate marine and surf
zone conditions. In the meantime expect seas between 2 to 5 feet
and southerly winds between 5 to 15 knots today. High risk of rip
currents will continue for northwest to northeastern beaches of
PR and Culebra until this afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 72 85 72 / 30 30 40 30
STT 84 73 84 73 / 50 30 20 20
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Re: Caribbean - Central America Weather

#20724 Postby cycloneye » Sat Jan 15, 2022 5:06 am

Area Forecast Discussion
National Weather Service San Juan PR
450 AM AST Sat Jan 15 2022

.SYNOPSIS...Frontal boundary will stall north of the area through
the weekend. Light winds are expected today, therefore conditions
should be favorable enough to generate afternoon showers with
isolated thunderstorms possible over Northwest Puerto Rico. Marine
conditions will deteriorate once again by Sunday as another
northerly swell arrives.

&&

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

A trailing front from the strong low pressure east of Massachusetts
has triggered thunderstorms as far south as Santo Domingo overnight
and its associated shearline is expected to pass through Puerto Rico
today before weakening in the local area. This and moisture out of
the Caribbean will bring showers to parts of Puerto Rico and a
chance of thunderstorms to the western and central sections of the
island. Because of this, better rainfall is expected today than
yesterday. Southwesterly low level flow is becoming disorderly as a
col between the front and the shearline passes close by and flow
then returns to east southeast during the day today. Tonight
moisture drops as drier air moves in and shower activity will
diminish for a short while until another area of moisture moves
through during the day on Sunday. Wet and dry patches move through
for the remainder of the period as winds increase Sunday night and
Monday.

At mid and upper levels, the atmosphere remains mostly dry. High
pressure at 500 mb remains east of the area as a ridge, which yields
west southwest flow for the forecast area. This mid-level ridge then
holds closely to the eastern half of the forecast area through
Monday. At upper levels, a ridge slowly builds over the area at the
expense of the ridge to our east, but conditions are still dominated
by high pressure there as well. A 90 knot jet can be found just
north of the forecast area Sunday night and Monday.

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

A frontal boundary is expected to stall north of the area early in
the cycle while dissipates. As this feature dissipates, a mid level
ridge will build in from the south. The ridge aloft is then expected
to hold across the central and east Caribbean through at least the
end of the forecast cycle. At lower levels, a surface high north of
the area will yield moderate to fresh easterly winds Wednesday
through Friday. In response to the frontal boundary and associated
shearline approaching the region...moisture advection is
anticipated, suggesting a better chance for frequent passing showers
across east and north coastal areas as well as some afternoon
convection across west Puerto Rico Tue-Thu. Nevertheless, weather
condition will gradually improve and return to a more seasonal and
drier pattern by the end of the workweek with showers, if any,
mainly across coastal areas of northern and eastern Puerto Rico as
well as the US Virgin Islands as the result of the building
ridge.

Maximum temperatures will continue to range from the mid 80s
across coastal areas to the low 70s across the higher elevations.

&&

.AVIATION...Mainly VFR conditions are expected. However, increased
cloud cover and SHRA will result in brief MVFR conditions across
TISX through about 15/15Z. Afternoon TSRA/SHRA ovr wrn and interior
PR will also result in areas of MVFR conds and mtn obscurations btwn
15/16-22Z. Surface winds will remain light and variable through most
of the day as sea breezes and east southeasterly flow battle for
influence. Winds will become 10-15 knots btwn 15/14-22Z. Max winds
WSW 65-85 knots btwn FL315-465.

&&

.MARINE...Seas will continue to gradually diminish today. However,
by Sunday and into early next week, another northerly swell will
arrive, resulting in choppy to hazardous marine conditions for the
Atlantic waters and passages. Therefore, a Small Craft Advisory
for the Atlantic offshore waters and a High Risk of Rip Currents
will be in effect for the latter part of the weekend into next
week. See MWWSJU and CFWSJU for additional details.

Meanwhile, winds up to 10 knots are expected to prevail today,
increasing up to 15 knots tomorrow.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 72 85 72 / 40 30 30 30
STT 82 74 84 74 / 20 20 20 20
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Re: Caribbean - Central America Weather

#20725 Postby cycloneye » Sun Jan 16, 2022 5:24 am

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Sun Jan 16 2022

.SYNOPSIS...A seasonal weather pattern is expected to prevail
during the next few days with showers moving over eastern Puerto
Rico and the U.S. Virgin Islands as well as some locally induced
afternoon showers across west Puerto Rico. Hazardous marine and
coastal conditions are expected to prevail today and Monday as a
northerly swell spreads across the Atlantic waters and local
passages.

&&

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

High pressure at low levels is present northeast of the area and
extends weakly west over the Atlantic waters north of the area. This
high pressure will be squeezed between the low that has already
crossed through the northwestern central Atlantic and a newly
forming low exiting the New England states Monday. This will be
sufficient to maintain moderate east to east southeast trade winds
across the area. This pattern will bring alternating moist and dry
parcels out of the east central Atlantic ocean with the result of
passing showers in the eastern portion of Puerto Rico and over the
local waters and U.S. Virgin Islands and somewhat heavier showers
over western Puerto Rico each afternoon.

At mid and upper levels, the atmosphere remains mostly dry. High
pressure at 500 mb remains east of the area as an eastward-leaning
ridge which yields west flow for the forecast area today. As a high
pressure center over the southern Caribbean migrates westward, winds
at mid levels shift to the northwest. Overall, however, 500 mb
heights will continue near seasonal normals. At upper levels, a
ridge slowly builds over the area at the expense of the ridge to our
east, but conditions are still dominated by high pressure there as
well.

There was one report of lightning in the area on Saturday when
the parcel was free to rise to nearly 33 kft. That is still the case
today, but less moisture is expected, therefore have left the chance
of thunderstorms out of the forecast for the period.

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

The long term forecast is still on track. As a frontal boundary
dissipates north of the area, a mid level ridge will build across
the local area. This feature is expected to hold through the end
of the cycle. At lower levels, a surface high across the central
Atlantic will yield moderate to fresh easterly winds. In response
to the dissipating frontal boundary and associated moisture,
there is a better chance for frequent passing showers across the
east and north coastal areas of the local islands and some
afternoon convection across west Puerto Rico Wed-Thu. Nevertheless,
weather condition will gradually improve and return to a more
seasonal and drier pattern by the end of the workweek with passing
showers, if any, across eastern coastal areas under building ridge.

Maximum temperatures will continue to range from the mid 80s
across coastal areas to the low 70s across the higher elevations.

&&

.AVIATION...Mainly VFR conditions are expected. Isolated SHRA will
form owing to a drier air mass passing through. Sct SHRA to dvlp wrn
and interior PR aft 16/16Z with MVFR conds not expected at TAF
sites. Sfc winds 12-18 knots with gusts to 24 kt psbl alg N and S
coasts of PR, diminishing aft/16/22Z. Max winds W 55-75 kts btwn FL
285-455 and increasing bynd 16/18Z.

&&

.MARINE... Hazardous marine and coastal conditions are expected to
prevail today and Monday as a northerly swell spreads across the
Atlantic waters and local passages. Building seas 5 to 7 feet are
expected later today with breaking waves between 9 and 11 feet.
A Small Craft Advisory and a High Surf Advisory will go into
effect this afternoon. See MWWSJU, CFWSJU and SRFSJU for details.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 73 85 73 / 30 20 20 20
STT 83 73 83 73 / 20 20 20 20
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Re: Caribbean - Central America Weather

#20726 Postby cycloneye » Mon Jan 17, 2022 4:45 am

Area Forecast Discussion
National Weather Service San Juan PR
448 AM AST Mon Jan 17 2022

.SYNOPSIS...High pressure north of the area will maintain moderate
to fresh east southeast trade winds that will carry alternating
bands and patches of moist and dry air across the region. After a
brief period of dry air this evening, moisture will return to
seasonal normals or slightly better through Monday of next week.
This will generally contribute to night and morning showers across
eastern Puerto Rico, the local waters and occasionally over the
U.S. Virgin Islands and afternoon showers in western or
northwestern Puerto Rico during the afternoons. Northerly swell is
generating hazardous marine conditions.

&&

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

A mid level ridge is expected to hold across the local islands
through the forecast cycle. At lower levels, migratory surface highs
will continue to yield moderate east southeast winds today and
Tuesday, becoming more easterly on Wednesday. A frontal boundary
which is now located across the western tropical Atlantic will
approach the local islands late Tuesday into Wednesday while it
dissipates. Nevertheless, the bulk of moisture associated with this
feature is expected to remain north of the islands. As a matter of
fact, latest guidance continued to suggest low level moisture
remaining near or below climatological values, with PWAT values
around 1.0 to 1.3 inches.

Therefore, a seasonal weather pattern is still expected with
showers moving over eastern Puerto Rico and the U.S. Virgin
Islands at times as well as some locally induced afternoon showers
across western Puerto Rico. Maximum temperatures will continue to
range from the mid 80s across coastal areas to the low 70s across
the higher elevations.

.LONG TERM...Thursday through Monday...
By Thursday high pressure at the surface will dominate the central
Atlantic Ocean while moving northeast. This will keep east to east
southeast trade winds moderate to fresh across the area. It will
also cause the alternating bands and patches of moist and dry air
to move rapidly across the forecast area bringing showers of
minor to modest amounts each day. Mid and upper levels are mostly
dry with the exception of slightly deeper than usual moisture on
Friday. Upper levels will continue to see moderate to strong jet
action over and just north of the local area as an upper level
ridge continues over the Caribbean and northern South America. On
Sunday and Monday winds at 850 mb will turn southeast to south
southeast as high pressure sinks a little further south in the
Atlantic. This will bring slightly drier weather and warmer
temperatures to the north coast should the forecast hold.

&&

.AVIATION...VFR conds are expected to prevail at all terminals.
VCSH possible at TJSJ and the USVI sites through at least 17/15z.
Wind from the ESE at 15 KT with sea breeze variations at the TJPS,
TJBQ, and TJSJ after 17/13Z. VCSH expected at TJBQ after 17/17Z with
possible CIG at around FL050. Maximum winds W 70-85 knots btwn
FL310-440, diminishing during the next 24 hours.

&&

.MARINE...Seas are expected to peak this morning at around 8 feet and
then slowly subside through Tuesday night as northerly swell
moves through the area. This will hold high surf through Tuesday
and a high rip current risk through at least Wednesday. Small
craft advisories are expected to come down later tonight, but may
return by Wednesday as a new swell train enters from the north.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 72 84 72 / 20 30 20 40
STT 83 72 83 72 / 20 30 20 40
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Re: Caribbean - Central America Weather

#20727 Postby cycloneye » Tue Jan 18, 2022 4:40 am

Area Forecast Discussion
National Weather Service San Juan PR
507 AM AST Tue Jan 18 2022

.SYNOPSIS...High pressure north of the area will maintain moderate
to fresh east southeast trade winds that will carry alternating
bands and patches of moist and dry air across the region. After
the brief period of dry air overnight, moisture will return to
seasonal normals or slightly better through Friday of this week.
This will generally contribute to night and morning showers across
eastern Puerto Rico, the local waters and occasionally over the
U.S. Virgin Islands and afternoon showers in western or
northwestern Puerto Rico during the afternoons. Northerly swell is
diminishing. On Sunday, the surface high will build over the
western tropical Atlantic causing flow to become more southerly
and raising temperatures over the northern half of Puerto Rico
Sunday and Monday. Moisture then will be sporadic.


&&

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

Mostly clear to partly cloudy skies prevailed across the local
islands during the overnight hours with passing showers observed
across the local waters. Minimum temperatures ranged from the low to
mid 70s in the lower elevations to the 60s in the mid and higher
elevations. Winds became light and variable overnight.

Overall, the short term forecast is still on track. A mid level
ridge will continue to prevail across the local islands through the
forecast cycle. At lower levels, a moderate east southeast wind flow
is expected today, becoming moderate to fresh and out of the east
Wednesday and Thursday. The latest guidance continued to suggest
patches of low level moisture, which are associated with a
dissipating frontal boundary north of the area, moving across Puerto
Rico and the US Virgin Islands at times. This will result in near-
normal moisture, with precipitable water values of around 1.3 to
1.5 inches.

Therefore, near normal moisture and stability provided by the
ridge aloft, a seasonal weather pattern is still expected with
showers moving over eastern Puerto Rico and the U.S. Virgin
Islands at times as well as some locally induced afternoon showers
across western Puerto Rico. Maximum temperatures will continue to
range from the mid 80s across coastal areas to the low 70s across
the higher elevations. Breezy on Thursday.

.LONG TERM...Friday through Tuesday...
The cold front that was approaching the area during the short term
period will have reached its closest approach to our north early
on Friday of about 50 miles north of the forecast area. This also
tends to mark the beginning of a warming trend--slight at first
and then more marked Sunday through Tuesday. The models show
precipitable water also reaching a high point early on Friday
morning, with moisture plummeting late Friday, recovering by
Saturday evening and then falling even lower on Monday, before
returning to Friday`s high on Tuesday afternoon. Timing and
intensity are questionable but this scenario fits with the
general scenario of alternating moisture patches that has been the
story for a while now. The return of the good moisture on Tuesday
is actually from the old frontal boundary that was just north of
us Friday as it circulates around the high pressure at 700 mb.
More remarkable than the weather generated is the stability of the
air mass over us Saturday through Tuesday as 500 mb temperatures
warm from a low near minus 10 degrees on Thursday to around minus
6 Saturday through Tuesday. This leaves diminishing showers
Saturday through Tuesday offset only by the variation in moisture
described earlier and meshes well with the climatology of the
latter half of January.

The ridge at mid levels will remain over or close by the area
through the period while the broad ridge of high pressure remains
generally west or over the area. This will generally weaken most
shower activity over the area as is natural for the season.

&&

.AVIATION...VFR conds are expected to prevail at all terminals.
Wind from the ESE at 15 KT with sea breeze variations at the TJPS,
TJBQ, and TJSJ after 18/13Z. VCSH expected at TJBQ after 18/17Z with
possible CIG at around FL050. Maximum winds WNW-NW
60-80 kt btwn FL 290-410 greatest at FL375.


&&

.MARINE...Swell from the north is subsiding and high surf is
expected to end on the forecast area this afternoon. It is
surmised that the high surf still left in Culebra is due to the
swell there being the last to clear the area. Rip currents remain
a problem for many beaches with a northern exposure as winds
increase during the week and in some areas possibly reaching 20
knots. A second swell from the northwest will move through our
Atlantic waters on Wednesday, but will be short lived. Seas will
then be mostly 3 to 5 feet through the beginning of next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 72 84 72 / 20 40 40 40
STT 83 72 84 73 / 20 40 40 40
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Re: Caribbean - Central America Weather

#20728 Postby cycloneye » Wed Jan 19, 2022 4:34 am

Area Forecast Discussion
National Weather Service San Juan PR
427 AM AST Wed Jan 19 2022

.SYNOPSIS...
Passing showers will continue to move across the area today. A
building high pressure will then dominate the weather pattern
through early in the weekend, with stable conditions expected.
Hazardous marine conditions are expected tonight through the end
of the week due to a northwesterly swell and increasing winds.

&&

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

Clear to partly cloudy skies prevailed across Puerto Rico and the
U.S. Virgin Islands during the overnight hours. Some cloudiness with
a few showers persisted over portions of northwestern PR and over
western waters of PR, while a broad area of shallow moisture and
mostly cloudiness moved from the Anegada Passage into the USVI.
Minimum temperatures ranged from the low to mid 70s across coastal
areas to the high 50s across the higher elevations. Light easterly
winds prevailed through the night.

A polar trough segment is forecast to remain north of the region
today, and move further east by early Friday. This will keep 500 mb
temps colder than normal(around -9C) until at least Thursday, and a
strong westerly jet aloft. However, a mid-level ridge is forecast to
slowly build over the southwestern Atlantic during the next few days
and this should promote more stable conditions during the end of the
short term period. Trade winds are forecast to increase as the ridge
tightens the pressure gradient later on Thursday and Friday.
Precipitable water content is expected to fluctuate between 1.10-
1.50 inches, with peaks in nighttime and early morning convection
each day. Therefore, expect trade wind showers to move during this
period across portions of the USVI and eastern PR. During the
afternoon and early evening hours, scattered shower development is
expected over western PR, particularly today and tomorrow.

.LONG TERM...Saturday through Wednesday...
High pressure centered just north of the islands will dominate
the atmosphere for the upcoming weekend. This will translate into
dry air at the mid-levels, with relative humidities at 1.0 inch or
even less. Additionally, a trade wind cap inversion around 750 mb
will trap any available moisture at the lower levels. Therefore,
no significant rainfall is expected on Saturday. By Sunday, the
mid-level ridge should weaken as a polar trough exits the eastern
coast of the United States. This will allow columnar moisture to
increase, as patches of moisture are carried by the trade winds
across the eastern Caribbean. No major rainfall event is
anticipate, but a more typical pattern, with advective showers
affecting eastern Puerto Rico and the U.S. Virgin Islands through
the day and afternoon showers over western Puerto Rico, is then
expected.

For the workweek, a frontal boundary well to the northwest of the
region and a surface high pressure over the central Atlantic will
maintain a steering wind flow mainly out of the east or slightly
from the southeast at about 10 to 15 knots. This will result in
intermittent areas of moisture infiltrating from the east, which
should bring irregular periods of scattered shower activity across
the region.


&&

.AVIATION...
Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, SHRA is expected to
develop this afternoon over western PR, which may cause tempo MVFR
cigs at TJBQ. Low level winds will increase btw 10-15 kt with higher
gusts and sea breeze variations aft 14z.

&&

.MARINE...
A northwesterly swell is expected to invade the local waters
today, with seas 4 to 6 feet for today, and 5 to 7 feet tonight
across the offshore Atlantic waters. Winds are also expected to
pick-up by tonight, creating choppy conditions along most of the
waters.

For the beaches, a high rip current risk is in effect for most of
the north, east, and western coasts of the local islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 72 84 73 / 40 40 40 40
STT 83 73 84 73 / 30 40 40 40
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Re: Caribbean - Central America Weather

#20729 Postby cycloneye » Thu Jan 20, 2022 4:35 am

Area Forecast Discussion
National Weather Service San Juan PR
417 AM AST Thu Jan 20 2022

.SYNOPSIS...
Winds will pick-up through early in the weekend, mainly impacting
marine and coastal conditions due to choppy seas and high rip
current risk along many of the local beaches. Areas of showers
will move from time to time across the islands, but no significant
rainfall events are in the forecast through the next seven days.

&&

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

Clear to partly cloudy skies were once observed across Puerto Rico
and the U.S. Virgin Islands through the overnight. Trade wind
showers increased across the regional waters, with a few moving over
land areas. Minor rainfall accumulations were observed with this
activity. Observed minimum temperatures ranged from the high 60s to
low 70s across the lower elevations to the low 60s in the higher
elevations. Gusts between 15-20 mph were observed with the passing
showers.

A ridge pattern at all levels will continue to promote breezy
conditions across the region through at least early Saturday
morning. Shallow areas of moisture embedded in the trade winds will
bring occasional passing showers across the USVI and eastern
sections of Puerto Rico. Latest model guidance continues to suggest
that below normal precipitable water content should prevail through
the short term period, with small surges in moisture this afternoon
and during the overnight/early Friday morning hours. Furthermore, a
drier air mass and more stable conditions are expected from Friday
afternoon through Saturday. Therefore, overall fair weather and
breezy conditions should prevail through much of the short term
period, with light rainfall amounts over land areas.

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

The forecast remains on track for Sunday, with the mid-level ridge
weakening in response of a polar trough exiting the eastern coast
of the United States. One difference from yesterday analysis is
that now Sunday looks much drier, since the patch of moisture
appears to move faster and should clear the local islands by
Saturday. The GFS forecast sounding show precipitable water values
of 1.0 inch or less, and therefore, the Probability of
Precipitation was decreased for this day.

On Monday, the surface steering flow is expected to shift from the
east-southeast in response of a cold front near the Bahamas and a
high pressure over the Central Atlantic. The flow should be on the
light side for this day, but winds will pick-up once again by
Tuesday as another surface high pressure builds just north of the
area. This high pressure should migrates toward the east as
another cold front begins to exit the eastern coast of the United
States, making winds shift from the east-northeast. Through the
workweek, intermittent periods of enhanced moisture are expected
to reach the area. As a result, advective showers may still impact
the eastern half of the forecast area from time to time, with some
convection developing over western Puerto Rico each afternoon. No
significant rain events are in the forecast at this moment.

&&

.AVIATION...
Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, SHRA is expected to
develop btw 20/16z-22z over western PR, which may cause tempo MVFR
cigs at TJBQ. East winds are expected to increase btw 12-18 kt with
sea breeze variations and higher gusts 20/14z.

&&

.MARINE...
A northwesterly swell is invading the local Atlantic waters today.
The outer buoy had observations of 6.2 to 6.6 feet at 11 seconds,
while the nearshore buoys have seas below 5 feet. Seas could
increase a little bit more for the offshore Atlantic, and a Small
Craft Advisory is in effect for this area. Elsewhere, choppy seas
4 to 6 feet and winds out of the east at 15 to 20 knots are
anticipated.

For the beaches, a High Rip Current Risk statement is in effect
for the beaches of northern, western, eastern and southeastern
Puerto Rico, as well as Vieques, Culebra and all beaches of the
U.S. Virgin Islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 73 84 73 / 40 40 30 20
STT 84 73 84 72 / 50 50 30 30
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Re: Caribbean - Central America Weather

#20730 Postby cycloneye » Fri Jan 21, 2022 5:11 am

Area Forecast Discussion
National Weather Service San Juan PR
428 AM AST Fri Jan 21 2022

.SYNOPSIS...
Breezy conditions will prevail across the region through the end
of the week. This will drag some passing showers over the local
islands, and will also result in choppy to hazardous seas across
the local waters. Fair weather conditions are expected for Sunday
Monday, followed by an increase in passing showers for the rest of
the workweek.

&&

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

Trade wind showers moved over portions of the U.S. Virgin Islands
and across the eastern half of Puerto Rico during the overnight
hours. The doppler radar estimated around half an inch of rain over
the eastern interior and southeastern coast of PR. Minimum
temperatures ranged from the high 60s to low 70s across the lower
elevations to the low 60s in the higher elevations. Gusty winds
between 20-30 mph were observed across coastal areas of the islands.

A mid- to upper-level ridge over the region will continue to promote
dry air above 800 mb and warming of the 500 mb temperatures through
the short term period. Breezy trades will continue through at least
early Saturday. Thereafter, winds will decrease as the ridge over
the central Atlantic is forecast to weaken under pressure from a
surface front moving across the western Atlantic. This should
coincide with the arrival of an area of better columnar moisture
(through 700 mb) from the northeast, and latest model guidance
suggest better chances of measurable rainfall on Saturday than
previous guidance. For Sunday, precipitable water content is still
forecast to drop below normal levels, and this absence of moisture
in combination with light steering winds should result in fair
weather conditions across the islands, with limited shower
development over the western interior of PR.

.LONG TERM...
The surface high pressure over the north-central Atlantic will
continue to lose its grip over the area in response to a cold
front near the Bahamas. This will result in lighter low level
winds, at less than 10 knots. Although the mid-level ridge
continue to weaken, it will maintain a dry air mass in the mid-
levels, with relative humidities below 20%. This should result in
generally fair weather for the islands. By Tuesday, as the frontal
system becomes disorganized well to the north of the area, another
surface high will build north of the region, bringing slightly
stronger winds, but out of the east. A surface trough appears to
develop east of the Leeward Islands, enhancing moisture content
and low level convergence over the area. This should increase the
frequency of showers through the day, although the feature will
not be strong enough to generate significant rainfall
accumulation.

For the latter part of the workweek, the surface high will migrate
toward the east as another cold front exits the eastern coast of
the United States. The wind flow will turn from the east-
northeast, which should promote an advective pattern affecting the
U.S. Virgin Islands, northern and eastern Puerto Rico through the
day, and then fueling some activity over the western or
southwestern sections of Puerto Rico each afternoon.


&&

.AVIATION...
Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, trade winds showers
could move at times across the USVI/Eastern PR terminals through the
period causing brief MVFR cigs. East winds will continue at 15-20 kt
with with sea breeze variations and higher gusts after 21/14z.


&&

.MARINE...
Winds and seas have increased across the offshore buoy, with
readings in the overnight over 7 feet. These conditions are
expected to continue through tomorrow. Seas across the offshore
Atlantic and Caribbean and the passages will remain above small
craft advisory criteria through tomorrow.

A high rip current risk will continue for the north, west and
eastern coast of Puerto Rico, Vieques, Culebra, and for the U.S.
Virgin Islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 72 85 71 / 30 20 30 30
STT 84 74 84 73 / 30 30 40 30
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Re: Caribbean - Central America Weather

#20731 Postby cycloneye » Sat Jan 22, 2022 5:35 am

Area Forecast Discussion
National Weather Service San Juan PR
518 AM AST Sat Jan 22 2022

.SYNOPSIS...Patches of moisture embedded in the trade winds will
bring passing showers today across the islands. Breezy conditions
should continue today. Ridge pattern aloft will prevail through
the long term period, limiting the vertical development of showers
and total rainfall accumulations. Winds are expected to decrease
on Sunday/Monday before picking up again during the rest of the
workweek. The main hazard today will be the high risk of rip
currents along the north and east-southeast facing beaches of the
islands.


&&

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

Satellite imagery from GOES-16 shows an area of slighter higher
moisture content filtering over the islands. This will cause some
showers this morning across the U.S. Virgin Islands and the northern
and eastern municipalities of Puerto Rico. At the mid-levels, a
ridge of high pressure continues to be the dominant feature across
the northeastern Caribbean. This feature results in dry air at the
mid-levels, with relative humidities below 30%, and a trade-wind cap
around 750 mb. Therefore, the moisture will remained trapped at the
lower levels. The mid-level ridge should be strong enough to suppress
strong activity, local effects should trigger scattered shower
activity across the interior and western Puerto Rico.

For Sunday, the pressure gradient will weaken a little bit,
resulting in lighter winds. The mid-level ridge will keep it hold
over the area, although it will begin to move toward the east.
Additionally, the global models show a pocket of dry air moving into
the islands, with precipitable water values below 1.0 inch and a
stronger trade wind cap inversion at 850 mb. This will translate
into fair weather conditions for the local islands. Moving into
Monday, the mid-level ridge will begin to weaken in response of a
polar trough exiting the eastern coast of the United States. At the
surface, the winds will become even lighter, below 10 knots, and out
of the east-southeast. This wind flow will drag patches of moisture
associated with old frontal boundaries north of the region. Moisture
will go up to the 700 mb layer, which should result in some showers
reaching the islands from time to time.

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

Trade winds are expected to increase between 10-20 kt through the
workweek, as a surface high pressure builds north of the region.
Winds will turn more from the east to northeast and this is
expected to promote moisture advection across the region through
the long term period. Therefore, showers are expected to favor
nighttime/early morning convection across the USVI and eastern
sections of PR. Then in the afternoon, small surges in low-level
moisture should allow for showers to develop over west/southwest
PR. At the mid- to upper-levels, a ridge pattern will remain in
place promoting drier air and overall stable conditions aloft and
rainfall amounts in general should be light to moderate at times.


&&

.AVIATION...Mainly VFR conditions are expected to prevail through
the forecast period. VCSH are expected for the Leeward terminals,
which could briefly reduce VIS and cause low ceilings. Winds will
be out of the east at 10 to 15 mph, with stronger gusts and sea
breeze variations.

&&

.MARINE...Choppy seas up to 6 feet and easterly winds up to 20
knots are expected to continue today across most of the local
waters. Therefore, small crafts should exercise caution. Winds and
seas will improve briefly on Sunday and early Monday, before
increasing once again during the first part of the workweek. A
high risk of rip currents will continue today across most of the
north and east-southeast facing beaches of the islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 72 86 72 / 30 30 10 20
STT 85 70 85 72 / 40 30 30 30
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Re: Caribbean - Central America Weather

#20732 Postby cycloneye » Sun Jan 23, 2022 5:22 am

Area Forecast Discussion
National Weather Service San Juan PR
506 AM AST Sun Jan 23 2022

.SYNOPSIS...A mid-level ridge will continue to promote drier air
aloft and overall stable conditions. At lower levels, patches of
moisture will bring the occasional passing shower across the USVI
and eastern sections of PR, followed by diurnally induced
afternoon showers over western PR. Light to moderate trade winds
are expected to prevail through next week.


&&

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

A mid-level ridge continues to hold over the eastern Caribbean. This
feature is creating a trade wind cap around 850 mb, with very dry
air at the mid-levels (relative humidities around 10%). At the
surface, Total Precipitable Water from GOES-16 also shows a pocket
of dry air, with values around 0.7 inches, approaching from the
northeast. Taking all these factors into consideration, pleasant
conditions, with very limited shower activity is anticipated for
today. The mid-level ridge is expected to weaken and moves toward
the east in response of a polar trough and associated front leaving
the eastern coast of the United States. Therefore, the surface high
pressure over the north-central Atlantic will weaken as well, and so
will be the trade winds, with a low level steering flow below 8
knots. These weather pattern is expected to stretch into Monday as
well. However, by the end of the day and into Tuesday, the latest
guidance show an area of enhanced moisture crossing the local
islands. As a result, an increase in shower frequency can be
anticipated. As is usual under these conditions, advective showers
will affect the eastern half of Puerto Rico and the U.S. Virgin
Islands through the day, followed by afternoon convection for the
interior and western Puerto Rico.

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

A similar weather pattern is expected to prevail through the long
term period. Another mid-level ridge is forecast to build from the
west and linger over the northeastern Caribbean through Saturday.
The ridge is then expected to weaken by Sunday under pressure from
a polar trough across the western Atlantic. At lower levels, winds
are forecast to increase slightly by mid-week, and decrease during
the weekend as a col area develop west and northwest of the
region due to the approaching polar front. East to northeast
steering winds should last through the long term period. The ridge
will continue to promote drier air aloft and overall stable
conditions. The best moisture content will remain trapped below
800 mb until the ridge collapses later in the weekend. Therefore,
patches of moisture will move at times through the overnight/early
morning hours across the USVI and east/northeast sections of PR,
followed by shallow afternoon convection developing over
west/southwest PR.


&&

.AVIATION...VFR conditions are expected to continue through the forecast
period. VCSH may impact the Leeward terminals at times, causing
brief reductions in visibility and low ceilings. Winds will be out
of the east at less than 10 knots through 20Z.


&&

.MARINE...Gentle to moderate trades are expected to prevail during
the next several days. Seas will continue to improve today, with
seas up to 5 feet mainly across the Atlantic waters. There is a
moderate risk of rip currents across all the beaches of PR and the
USVI.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 72 85 72 / 10 10 10 30
STT 84 71 83 72 / 30 30 30 50
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Re: Caribbean - Central America Weather

#20733 Postby cycloneye » Mon Jan 24, 2022 4:30 am

Area Forecast Discussion
National Weather Service San Juan PR
503 AM AST Mon Jan 24 2022

.SYNOPSIS...

Generally fair weather is expected this morning. Later today,
increasing moisture is likely to result in an increase in shower
activity, lasting through tomorrow. Patchy moisture will continue
to affect the islands through the week. This weekend, a frontal
boundary is forecast to stall out north of the islands, leading to
a gradual increase in moisture over the region.

&&

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

Today, calm weather conditions will prevail early this morning,
associated with a dry air mass over Puerto Rico and the U.S. Virgin
Islands. Therefore, expect pleasant temperatures and minimal rain
activity with mostly sunny to partly cloudy skies. However, GOES-E
Total Precipitable Water-derived imagery detected a disturbance in
the trades with values between 0.99 and 1.35 inches of precipitable
water. This perturbation will replace the dry air, arriving around
mid-morning and early this afternoon, bringing clouds and showers
first across the Virgin Islands (especially St Croix) and eastern
Puerto Rico, and then across interior and northwestern PR by the
afternoon and evening hours.

Winds will have an east-southeasterly component due to a shear line
associated with an old frontal boundary moving eastward across the
Western Atlantic (north of the islands) today and Tuesday. Moisture
will increase even more as the perturbation moves across the islands
by Tuesday, increasing cloud cover and the frequency of passing
showers, as well as afternoon convection. Moisture content will
rapidly erode late Tuesday afternoon into Wednesday as the trade
winds push a somewhat cooler, dry air mass, limiting rain
activity.

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

Conditions will continue much as they have, as patches of moisture
support seasonally typical conditions. Generally fair weather is
likely, especially for the end of the workweek, though isolated to
scattered showers are anticipated, in a typical pattern. Some
weakening in the mid-level ridge is anticipated this weekend into
early next week, in response to a deep-layer trough swinging off the
coast of North America, associated with an Arctic low over Hudson
Bay moving to the Labrador Sea. Gradual increases in moisture aloft
are expected, but significant improvement above 850 to 700 hPa is
not likely during the forecast period.

A frontal boundary will approach the region from the northwest late
in the weekend, stalling out north/northwest of the islands. Winds
will weaken over the region and become more variable, while moisture
gradually increases, with some weak convergence over the area as
patches push over, then slow and interact with the frontal boundary.
A modest increase in shower activity is possible during the early
week.

Late on Monday, there is the potential for a jet around 200 hPa to
be impacting the region, which would increase ventilation, and
therefore increase shower activity.

Forecast confidence is near normal. Sources of uncertainty include
how close the frontal boundary gets to the islands before stalling
out during the forecast period, as well as the timing and magnitude
of moisture patches.

&&

.AVIATION...

VFR conditions will persist across the local flying area. SHRA/-SHRA
will move near ISX through this morning, spreading into E-PR/IST
later this morning into the afternoon. Clouds will increase somewhat
across the local flying area after 24/15z, and SHRA could develop
across interior and NW-PR btwn 24/15-23z. Surface winds will
continue calm to light and VRB thru 24/13z, then, increasing at 10-
15kt from the ESE and with sea breeze variations.

&&

.MARINE...

Light to gentle winds of up to around 8 to 12 knots are expected
today, generally out of the east to east-southeast. Some light chop
is possible. Seas of up to around 4 feet are anticipated this
morning, with building seas later in the day into tonight; wave
heights of up to around 5 to 6 feet are possible, especially for the
offshore Atlantic waters.

There is a moderate risk of rip currents for most local beaches
today. Tonight, increasing risk is anticipated, with a high risk of
rip currents for beaches along the north coast of Puerto Rico,
including Aguada and Rincon, as well as beaches of Culebra, northern
and western St. Thomas and St. John, and eastern St. Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 73 86 73 / 20 50 40 20
STT 84 72 84 71 / 10 50 10 10
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Re: Caribbean - Central America Weather

#20734 Postby cycloneye » Tue Jan 25, 2022 4:50 am

Area Forecast Discussion
National Weather Service San Juan PR
503 AM AST Tue Jan 25 2022

.SYNOPSIS...

An area of increased moisture over the area will continue to promote
passing showers across the waters this morning, with a few pushing
onshore from time to time. Scattered to numerous showers are also
expected this afternoon in the west. Generally fair weather is
likely to prevail through much of the week, with a persisting
advective weather pattern bringing some showers to the area. A
frontal boundary could bring an increase in shower activity to the
region early next week into midweek.

&&

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

A mixture of sunshine and clouds will prevail today across most
portions of the islands. But keep in mind that a trade wind
perturbation will increase moisture across the islands today. Values
detected with the GOES-E derived Total Precipitable Water ranged
between 0.99 and 1.37 inches, and this air mass is moving across the
region. The mid to upper-level ridge will continue over PR and USVI,
promoting dry air aloft and a trade wind cap limiting rain
activity`s intensity and vertical development. Despite this, do not
rule out periods of moderate rain, producing ponding of water in
roads and poorly drained areas, especially during the afternoon
hours across western PR. East-southeasterly winds will continue in
response to the shear line associated with an old frontal boundary
moving eastward across the Western Atlantic, off to the northwest of
the islands.

Moisture content will rapidly erode late this afternoon into the
evening as the trade winds push a somewhat cooler, dry air mass,
limiting rain activity by Wednesday. However, the advective pattern
dominating the region will continue on Thursday, and cool air
advection will promote isolated to scattered showers late Wednesday
night into Thursday. Clouds and showers will increase even more by
the morning and afternoon of Thursday when scattered to numerous
showers could be possible.

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

A seasonally typical pattern, with patches of moisture streaming
through the area from time to time, will persist through at least
the end of the week. The ridge persists at the mid- and upper-
levels, and will continue to inhibit significant shower development,
especially during the afternoons. A frontal boundary is expected to
slowly approach the region from the northwest, stalling out north of
the region. Monday into Tuesday, there will be some moisture
convergence over the area, as a relatively large patch of moisture
makes its way into the region from the southwest and then
interacts with the frontal boundary to the north. It appears
likely that the frontal boundary will push towards, if not over,
the islands later Tuesday as it begins to deteriorate.

Surface and low-level winds will start the forecast period generally
out of the east to east-northeast, becoming more southeasterly, and
then tending towards southerly Monday. Depending on whether or not
the frontal boundary actually makes it over the area, winds will
shift again - winds will likely become more northerly and then
northeasterly behind any frontal passage. Above around 700 hPa,
though, winds will be more westerly, especially starting early next
week, which will make shear a likely inhibitor of strong shower
development.

The mid- to upper-level ridge will begin to weaken, first at the
lower mid-levels and then progressively upward, in response to a
polar trough swinging off of the coast of North America. Stability
will decrease somewhat because of this. By Tuesday, the deep-layer
trough is expected to extend to just west or maybe northwest of the
area. The decreasing stability will support an increase in shower
activity from whatever moisture is available. However, as mentioned
previously, shear could counteract this somewhat. On Monday, a jet
is expected to be affecting the area at around 200 hPa, lasting into
early Wednesday, which could provide increased ventilation,
supporting additional convective potential then.

Expecting showers in a typical pattern. Friday will be among the
wetter days during this forecast period, considering the decreasing
stability, the patch of moisture that is expected to be in the
vicinity of the area, and the fact that the vertical wind shear is
not expected to be as strong, with winds staying more easterly to
northeasterly to around 600 hPa or so, based on guidance from the
GFS, with similar suggested by the Euro. Typical to drier-than-
normal conditions are expected for the weekend into early next week.
And another increase in shower activity is likely by Tuesday, due to
moisture convergence, the approaching deep-layer trough, and the
influence of the upper-level jet.

Forecast confidence is normal to below-normal. Uncertainties
continue to be largely based on the moisture patches - both the
timing and strength, as well as the frontal boundary. Frontal
passage is still far from certain, and its influence on the
conditions over the region is likely to be felt for much of the
first half of the week next week.

&&

.AVIATION...

VFR conditions will persist across the local flying area. SHRA/-SHRA
will spread from the east over E-PR/IST/ISX, then across the
interior and western sections by the afternoon. Cloudiness will
diminish across the USVI by mid-morning. On the other hand, it
should increase across PR. Surface winds will continue calm to light
and VRB thru 25/13z, then, increasing at 10-15kt from the ESE and
with sea breeze variations.

&&

.MARINE...

Winds continue out of the east at up to 15 knots, helping to sustain
seas of up to 5 feet, especially for the offshore Atlantic waters,
where a fading weak swell continues to affect the area. These
conditions will continue, with gradual improvement possible in the
second half of the week.

There remains a high risk of rip currents for many local beaches,
including all of the north coast of Puerto Rico (including Aguada
and Rincon), northern and northwestern portions of the northern
USVI, beaches of Culebra, as well as beaches of northern, western,
and eastern St. Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 73 84 73 / 50 20 20 60
STT 83 72 83 73 / 20 20 10 50
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Re: Caribbean - Central America Weather

#20735 Postby cycloneye » Wed Jan 26, 2022 5:01 am

Area Forecast Discussion
National Weather Service San Juan PR
506 AM AST Wed Jan 26 2022

.SYNOPSIS...

An advective weather pattern will persist across the region for the
second half of the week. Generally fair weather is expected, with
patches of moisture supporting occasional showers in a typical
diurnal pattern over the area. A frontal boundary is expected to
approach the region early next week. Though exact impacts remain
uncertain, increasing shower activity next week is likely.

&&

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

Cool air advection resulted in passing showers across the local
waters overnight, and some of them moved inland. Rain activity
should diminish as a cooler and dry air mass filters from the east
during the morning hours, leaving a mixture of sunshine and clouds.
Pleasant tropical winter temperatures will continue across the
region this afternoon.

A mid to upper-level ridge will hold aloft, promoting stable weather
conditions today and tomorrow. However, the advective pattern
dominating the region will continue through Friday, and cool air
advection will again bring isolated to scattered showers each night.
Thursday seems to be the best chance to have showery weather due to
a surge of moisture embedded in the trades.

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

A seasonally typical pattern will continue, with patches of moisture
streaming across the region from time to time. Moisture levels in
these patches will be near climatological averages, with below- to
near-normal moisture levels for the drier air in between. Isolated
to scattered showers are expected.

A frontal boundary is expected to be approaching the region from the
northwest this weekend into next week. This front is associated with
a strong low pressure system that is forecast to develop as a
nor`easter off the coast of North America, tracking along the coast
through the Canadian Maritimes. Model guidance is in good agreement
with the general scenario with this system, tracking it into New
England, continuing north-northeastward through the Canadian
Maritimes. The GFS shows a slightly faster trajectory that is ever-
so-slightly east/north of the Euro. Both also suggest that the
boundary will make its way near or over the islands by around
midweek next week. Even with good inter-model agreement, the
consistency between model runs is less than stellar, in terms of
conditions affecting the local islands. As such, there is some
uncertainty that continues with respect to when the frontal boundary
will be nearest, if it will pass over the islands, and how much
moisture will be brought into the area, either by the front itself
or due to moisture convergence over the area ahead/southeast of the
front.

The most likely scenario is that the deep-layer trough associated
with this frontal boundary will erode the ridge that has been in
place at the mid- and upper-levels, likely as soon as Saturday or
Sunday in the lower mid-levels. Stability will therefore decrease.
The timing and strength of any patches of moisture will be the
determinant of whether there will be a significant increase in
shower activity over the area, as well as the magnitude of change
and location most affected. Early next week, moisture convergence
will occur over the region. The most likely timing is late Monday
into Tuesday for this. The erosion of the ridge will combine with an
upper-level jet that is still expected to affect the region Monday
midday through Tuesday to increase instability. As such, an increase
in shower activity is likely. The frontal boundary will be near or
over the islands on Wednesday, bringing a further increase in shower
activity. The full impacts of said frontal boundary remain unclear.
Shifting winds will affect the location of the strongest shower
activity, and the shifting of the winds will depend greatly on
whether or not a frontal passage occurs.

A typical weather pattern, if possibly a little drier, especially to
start, is expected for the weekend. Increasingly active weather
conditions are expected early next week. By midweek, there is the
potential for frontal passage causing widespread shower activity.
Forecast confidence is below normal, however, due to significant
uncertainties with the frontal boundary, which has not yet even
begun to develop. Increasing instability is also expected next week,
and thunderstorms cannot be ruled out by midweek.

&&

.AVIATION...

VFR conditions will persist across the local flying area. Clouds and
SHRA/-SHRA will spread from the east over E-PR/IST/ISX. SHRA/-SHRA
will develop across the interior and western PR by 26/16-23z.
Surface winds will continue calm to light and VRB thru 26/13z, then,
increasing at 10-15kt from the E and with sea breeze variations.

&&

.MARINE...

Seas of 5 feet or less are expected across the local waters. Winds
remain out of the east, generally up to around 15 knots, though
winds of up to 20 knots are possible locally, mostly for offshore
waters south of the islands.

There is a high risk of rip currents for beaches along the north
coast of Puerto Rico, including Aguada and Rincon, as well as for
beaches of Culebra, northern Vieques, northern and northwestern St.
Thomas, and most beaches of St. Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 73 83 72 / 20 40 50 30
STT 83 72 84 72 / 20 40 30 10
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Re: Caribbean - Central America Weather

#20736 Postby cycloneye » Thu Jan 27, 2022 5:14 am

AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
521 AM AST Thu Jan 27 2022

.SYNOPSIS...

Generally, a stable weather pattern will prevail for the rest of
the week, with isolated to scattered showers in a typical way
across the islands and local waters due to the arrival of patches
of moisture. Model guidance suggests the possibility to move to a
more unstable and wet pattern by around next Tuesday and onward,
due to the proximity of trough aloft and frontal boundary at low
levels.

&&

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

A patch of moisture is moving into the area; with it, there has been
a modest increase in shower activity, with a few isolated showers
affecting the local waters and pushing onshore in northern Puerto
Rico. This general trend will continue, with areas of drier-than-
normal air punctuated by occasional patches of moisture supporting
varying levels of shower activity. As such, isolated to scattered
showers are expected from time to time, in a typical pattern across
the islands and local waters.

Prolonged periods of moist air are unlikely over the region
through the short term period, and moisture levels are expected to
stay within or below seasonal normals. There is still good
stability aloft over the region, as well. Though the ridge that
has held over the area at the mid- and upper-levels is expected to
slowly erode, in response to a deep-layer trough off the coast of
North America, the impacts are not likely to be very significant
during the rest of this week. On Saturday, moisture levels are
expected to be below normal, with precipitable water values at
around 0.9 to 1.2 inches, for much of the region, except over the
Caribbean, until the arrival of additional moisture from the east
in the evening/early night hours.

So, on the whole, generally fair weather is expected for the rest of
the week, with isolated to scattered showers possible. Forecast
confidence is medium to high. The main source of uncertainty is the
potential for small changes in the details of the moisture pattern
and/or timing to coincide with the diurnal pattern to align (or
unalign) moisture with forcing. Confidence is high that the overall
pattern will be seasonally typical, and that rainfall totals are
unlikely to be significantly high.

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

An approaching frontal boundary/shear line moving eastward across
the Western Atlantic will weaken a surface high pressure across
the Western Atlantic. This frontal boundary should approach the
northeast Caribbean and remain off to the northwest Sunday through
Tuesday. While at the mid to upper levels, a polar trough with a
strong jet will weaken the ridge aloft. Both GFS and ECMWF suggest
the frontal boundary slowly sinks southward by mid-week. In
addition, the polar trough could promote colder temperatures at
500 MB and the 200 MB heights to fall. Other factors indicating
the possibility of observing an unstable wet pattern by mid-week
are increased humidity from the surface to upper levels and
somewhat steep lapse rates at mid-levels.

The full impacts of the frontal boundary and the trough aloft
remain unclear. However, both GFS/ECMWF are converging to a more
consistent solution, which is an unstable wet pattern by around
mid-week. Therefore, conditions will become increasingly more
active next week, peaking by mid-week. This forecast still has
some uncertainty because it is tight to the frontal boundary final
position. However, this increment in instability will also allow
the potential of observing thunderstorms during the event`s peak.

&&

.AVIATION...

Generally VFR conditions expected through next 24 hours. VCSH
conditions are expected this morning for TJSJ, and brief MVFR
conditions associated with -SHRA cannot be ruled out. Afternoon
convection is expected to be over western/southwestern and interior
Puerto Rico, likely remaining away from aerodromes. Winds pick up
this morning, generally out of the east to east-northeast, with
speeds of around 8 to 12 knots, subsiding after sunset.


&&

.MARINE...

Mariner can expect seas between 1 and 3 feet across the coastal
waters and up to 5 feet offshore. A northeast swell will arrive by
late Friday, but seas will remain with the same values. A
northwesterly swell will spread late Sunday night to early Monday
morning, increasing the risk of having dangerous breaking waves at
the Atlantic Coastline.

Beachgoers, there is a high risk of rip currents from Aguadilla to
Dorado. The rest of the Atlantic Coastline, Vieques and the U.S.
Virgin Islands have a moderate risk.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 72 84 73 / 40 30 30 30
STT 83 72 83 74 / 30 30 20 30
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Re: Caribbean - Central America Weather

#20737 Postby cycloneye » Fri Jan 28, 2022 5:47 am

Area Forecast Discussion
National Weather Service San Juan PR
505 AM AST Fri Jan 28 2022

.SYNOPSIS...

An advective pattern will dominate local weather conditions
through at least the end of the weekend, resulting in a mixture of
clouds and sunshine. However, patches of moisture will give way to
isolated to scattered showers in a typical way across the islands
and local waters. Consistency between model guidance suggests the
possibility of moving to a more unstable and wet pattern by around
next Tuesday and onward, due to the proximity of trough aloft and
frontal boundary at low levels.

&&

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

The advective pattern will continue through the weekend, as dry air
is punctuated by patches of moisture making their way across the
region from time to time. Moisture levels will be well below
seasonal normals between these moisture patches. Throughout the
period, precipitable water values will not exceed seasonal normals,
varying from between 0.9 and 1.1 inches to 1.2 to 1.4 inches.
Isolated to scattered showers are expected, in a typical pattern,
with passing showers overnight over the local waters and pushing
onshore, and afternoon convection. Even as the ridge aloft is eroded
at the mid-levels, decreasing stability, the lack of available
moisture and the nature of the gradual increase in instability is
likely to result in underwhelming convection today, and likely
tomorrow as well.

Low-level wind flow over the region slows tomorrow and become more
variable, as the influence of ridging over the central Atlantic
decreases. The ridge that was over the northeastern US is now east
of Nova Scotia and will continue poleward ahead of a developing
system along the eastern seaboard of the United States. Meanwhile,
the high over the eastern central Atlantic will shift slightly
eastward. This, along with the approach of the southern part of the
frontal boundary off of the aforementioned nor`easter, will slacken
the pressure gradient over the region. Any convective development
that does occur tomorrow is likely to be mostly over the interior of
Puerto Rico. It is worth noting that there is still some lingering
uncertainty with the development and trajectory of this low that
could have impacts even as soon as tomorrow. A further east
trajectory is less likely than a further west one; should the
trajectory be more to the west, the effects on the winds over the
region via the pressure gradient could be slightly overstated, or
the timing could be a little later than presently anticipated. This
would also likely have an impact on the timing of moisture patches.
That being said, model guidance is giving better inter-run
consistency over the last 2-3 runs than it has been in previous
days, so uncertainty with the details of this system is decreasing.

Some moisture convergence is expected for Sunday. The dry slots will
slowly compress and erode as moisture builds over the region ahead
of the frontal boundary. Shower activity will increase, even as
lingering stability maintains generally unfavorable conditions for
widespread development. So, expect a modest increase in shower
activity, maintaining the typical pattern, for Sunday, which is
likely to be the wettest/most active day of the short term period.

Forecast confidence is high today, decreasing a little tomorrow,
though mostly just in the details. The general trend of generally
fair weather with a few isolated to scattered showers is forecast
with high confidence through the end of the week, with the only
slightly less confidence in the timing of the increase in moisture
over the area. The main source of uncertainty is the frontal
boundary as it approaches, and its indirect impacts ahead of it,
which are mentioned above.

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

A frontal boundary/shear line will slowly approach from the
northwest of the Northeast Caribbean by Monday, inducing a pre-
frontal surface trough over Puerto Rico and the U.S. Virgin
Islands. While at the mid to upper levels, a polar trough with a
strong jet will begin to increase instability. Once again, both
GFS and ECMWF favor the frontal boundary to slowly sinks southward
by mid-week. This polar trough could promote colder temperatures
at 500 MB and the 200 MB heights to fall, increasing the chance
for thunderstorm formation as early as Monday afternoon and
through at least Thursday. Plenty of moisture was also depicted by
models, increasing the likelihood of observing an unstable wet
pattern by mid-week.

Next week, the latest GFS/ECMWF are converging to an unstable wet
scenario. Although the full impacts of the frontal boundary and
the trough aloft remain unclear, conditions will become
increasingly more active next week, peaking after mid-week and
possibly drying after Thursday night or early Friday morning. As
mentioned yesterday, this forecast still has some uncertainty
because it is tight to the frontal boundary final position.

&&

.AVIATION...

Generally VFR conditions are expected across all aerodromes for the
next 24 hours. VCSH are possible for TJSJ/TIST/TISX until around
28/14Z, but operational impacts are unlikely. Some afternoon
convection is expected for western and interior PR, likely to remain
away from aerodromes. Winds generally out of the east after sunrise,
with speeds increasing to around 10 to 15 knots, with sea breeze
variations, then subsiding after sunset.

&&

.MARINE...

Mariner can expect seas between 1 and 3 feet across the coastal
waters and up to 5 feet offshore. A northeast swell will arrive by
late tonight. A northwesterly swell will spread late Sunday night
to early Monday morning, increasing the risk of having dangerous
breaking waves at the Atlantic Coastline.

Beachgoers, there is a moderate risk of rip currents for the
north, east and southeast coast of Puerto Rico, the island of
Culebra, Vieques, St Thomas, St Croix, and the northern and
southern coast of St John. The risk of rip currents will become
high by Saturday and onward.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 73 86 72 / 20 20 10 10
STT 83 74 84 73 / 20 10 20 20
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Re: Caribbean - Central America Weather

#20738 Postby cycloneye » Sat Jan 29, 2022 6:28 am

Area Forecast Discussion
National Weather Service San Juan PR
435 AM AST Sat Jan 29 2022

.SYNOPSIS...Surface low pressure will move north along the east
coast of the US this weekend, causing light winds locally. There
is also a mid and upper level ridge over the local area, which
will keep stable conditions and fair weather today. Better chance
of rain is expected for the mid to latter part of the upcoming
workweek. The main hazard we have currently is the high risk of
rip currents across the north coast of Puerto Rico and eastern
Saint Croix.


&&

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

Water vapor imagery shows a broad ridge of high pressure centered
over the Central Caribbean. This mid-level ridge extends over the
northeast Caribbean promoting dry air aloft. Low-levelmoisture is
trapped in the boundary layer betweenthe surface and the trade wind
cap thatis around 6,000 feet. The overall moisture will remain
below normal during the weekend as operational models suggest
precipitable water values of less than 1.25 inches. Therefore, a
fair-weather pattern with mostlysunny skies will prevail most of
the time. However, patches of moisture embeddedin the trade winds
producing a few passing showers can not be ruled out. Convection
over western Puerto Rico will be limited this afternoon mainly
because of the lack of moisture.

An intense polar troughthatis currently affecting the east coast
of the United States will swing justnorth of the area late Sunday
intoMonday. As a result, the aforementioned mid-level ridge will
gradually weaken across the local area promoting deeper convection,
especially Sunday and Monday afternoon over western Puerto Rico.
Also, the steering flow will be lighterallowing slightly higher
rainfall accumulations with the convection each afternoon. On
Monday, the shear line/prefrontal trough approaches the area from
the northwest increasing the low-level convergence across Puerto
Rico and this may lead to additional passing showers over the
regional waters and portions of the islands.

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

A surface low pressure across the central Atlantic, and a surface
high pressure across the western Atlantic just north of the local
islands, will dominate the local wind flow from midweek into next
weekend. The precipitable water is expected to be near 1.5 inches
through the workweek, which is near to slightly above normal, but
will quickly decrease to below normal values during the weekend. In
the upper levels, there will be a trough that will sink down and
position itself in a favorable location for local instability,
normally causing thunderstorm development over the local area.
However, the low to mid levels are not as conducive or favorable for
a deep convective pattern, as there is a high pressure at 700mb, and
only a very weak low pressure is seen at 500mb. Other parameters
such as lapse rates and 500mb temperatures are forecast to be near
near normal according to the GFS model.

As far as rainfall, a mix of sun and clouds with brief periods of
rain is forecast for Tuesday, but the situation gets a little more
complicated in the mid to latter part of the workweek. A frontal
boundary could be close to the local area, but most of the shower
activity associated with it could stay over the local waters. That
said, scattered showers with isolated thunderstorms could be
observed at times during this latter part of the workweek both
over the waters and land areas. The latest model run does not
show quite as much instability compared to previous runs. The
upper levels do seem favorable for deep convection, but the mid
levels not so much. The precipitation solution of the models are
also on the modest side. Therefore some adjustments were made to
the forecast, reducing the coverage of shower activity and also of
thunderstorms.


&&

.AVIATION...VFR conditions will persist across the TAF sites through the
forecast period. SCT showers are moving over the Caribbean waters
south of PR with no showers affecting the terminals this morning.
SHRA possible across western interior and NW-PR btwn 18-22z. ESE
winds around 10 kt with sea breeze variations can be expected
today.


&&

.MARINE...Seas up to 4 feet expected today. However, a northerly
swell coming in late this weekend will cause seas across the
Atlantic waters to be between 6 and 7 feet. The local winds will
be generally gentle this weekend, up to 10 knots or so. There is a
high risk of rip currents today for northern PR and eastern St
Croix, while a moderate risk is expected for some beaches of
northeastern and northwestern PR, Most of Vieques and Culebra as
well as many beaches of the USVI.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 72 85 72 / 10 10 30 30
STT 82 73 82 73 / 10 20 30 40

&&
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Re: Caribbean - Central America Weather

#20739 Postby cycloneye » Sun Jan 30, 2022 6:34 am

Area Forecast Discussion
National Weather Service San Juan PR
438 AM AST Sun Jan 30 2022

.SYNOPSIS...
Today, mainly fair weather conditions are expected to prevail
for the most part, followed by an increase in moisture and a
better potential for afternoon showers through the workweek. A
northwesterly swell will arrive on Monday, resulting in hazardous
marine and coastal conditions.

&&

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

Light winds are expected today as a surface low pressure moves along
the northeastern coast of the US today. Then, another surface low
pressure will develop into the west central Atlantic, and a weak
high pressure will move into the SW Atlantic early in the workweek,
to cause winds to remain easterly, but relatively light. A frontal
boundary to the west of Hispaniola will slowly move east as it
weakens, fragmenting by Tuesday as it gets close to the local
islands. An increase in available moisture is expected today, which
will cause a narrow band of showers to slowly move across the local
area, starting from the USVI this morning, then making it to eastern
PR by the early afternoon hours. Locally induced showers are
forecast across the western interior into western PR this afternoon
as well. As the frontal boundary moves closer and breaks down on
Monday, patches of deeper moisture could move into the local area,
but these areas of moisture with the expected light winds are
expected to mainly cause disorganized scattered showers across the
local area on Monday, though central PR has a higher chance of
significant rainfall than elsewhere in the local area. That said,
the increase in moisture for Tuesday is expected to be more
significant, with precipitable water surpassing 1.6 inches. In
additions, the local winds are expected to have a more defined
direction from the east to ENE by Tuesday afternoon. This will cause
showers across the local Atlantic waters and afternoon convection to
occur across central to western and southwestern Puerto Rico.

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

Model guidance is now better coinciding that a relatively moist
weather pattern will dominate for most of the long-term period,
particularly by the end of the workweek into the weekend. Between
Wednesday through Thursday, the remnants of an old frontal
boundary across the Atlantic waters will maintain low-level
moisture content at normal levels. The proximity of a shortwave
trough on Wednesday will provide some instability aloft. This will
aid in the development of convective activity across the area
with the possibility of isolated thunderstorms, although most of
the activity is expected across the Atlantic waters. Therefore,
expect periods of increased cloudiness and shower activity from
time-to-time with the possibility of isolated thunderstorms
across western Puerto Rico each afternoon and over the local
waters.

As we approach the end of the workweek into the weekend, a more
active weather pattern is looking more plausible. In the last
model cycles, GFS has been more bullish as a TUTT develops from
the shortwave trough and lingers over the area from early Friday
through at least early Sunday. Instability aloft will increase as
500 mb temperatures will drop below -10 degree celsius. At lower
levels, an induced trough will combine with the lingering moisture
further increasing precipitable water to above normal values at
times. GFS Galvez-Davison Index indicates the potential for
scattered thunderstorms, some capable of producing heavy rain as
moisture content and instability aloft increases. Friday afternoon
through Saturday is looking like the most active time period with
eastern Puerto Rico and U.S. Virgin Islands most affected.

ECMWF is less bullish, however, latest run is now much closer to the
GFS solution than previous model cycles although still showing a
smaller window of unstable wetter weather conditions. Given the
consistency of the GFS model and the ECMWF slowly converging to the
GFS solution, POPs for Friday into the weekend have been slightly
increased. Therefore, from this setup, the combination of
favorable condtions aloft with above normal moisture, will
enhanced cloud coverage and prolonged shower activity across the
forecast area. Although it is too soon to determine potential
impacts, if this forecast materializes, we could have the first
significant rainfall accumulation event of the year. Stay tuned as
we monitor these features.


&&

.AVIATION...

VFR conditions expected across the local TAF sites through the
forecast period. SCT showers will move into the local flying area,
causing VCSH at the IST and ISX terminals after 30/12Z. VCSH is also
possible at JSJ and JBQ after 30/18Z. East to ESE winds around 10 kt
with sea breeze variations can be expected today.


&&

.MARINE...Large swell currently spreading across the western
Atlantic is forecast to build seas up to 7 feet from late Sunday
night into Monday morning. This swell will likely result in High
Surf Advisory conditions along the northwest to northeast coast of
Puerto Rico, and maintain the rip current risk across the western
to northeastern beaches of PR and the USVI.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 72 84 72 / 30 30 40 20
STT 82 73 81 73 / 40 30 50 20

&&
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cycloneye
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Re: Caribbean - Central America Weather

#20740 Postby cycloneye » Mon Jan 31, 2022 5:22 am

Area Forecast Discussion
National Weather Service San Juan PR
443 AM AST Mon Jan 31 2022

.SYNOPSIS...An increase in moisture is expected today as a strong
frontal system approaches the local area. This will increase the
potential of showers throughout the week. Seas will be the main
concern this week, due to the presence of a northwesterly swell
that will arrive today and a second one on late Tuesday,
resulting in hazardous marine and coastal conditions. Small Craft
and High Surf Advisories along with High Rip Current Risk are in
effect through at least Tuesday.

&&

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

Light winds are expected once again today as a frontal boundary over
Hispaniola weakens, and a surface low starts developing to the NNE
of the local islands. Also, a weak high pressure will move into the
SW Atlantic later today, and a surface low will move into the
western Atlantic, just north of the SFC high. Even though the winds
will be light, and generally variable today, they will become
easterly starting tonight, and will remain easterly through midweek,
getting slightly stronger with each passing day. There is a strong
upper trough that will gradually approach the local area as the week
progresses, but the best position for instability is on Wednesday.
The same goes for the mid levels, even though the mid level trough
appears a bit weak at the moment, with the stronger impact in the
latter part of the week and beyond the short term period.

An increase in available moisture is expected today, which will
cause scattered showers to affect the USVI and eastern starting this
morning. This afternoon, locally induced showers are forecast across
the central to western PR, with some showers moving north later in
the afternoon. That said, the winds will be rather light over PR, so
the shower activity could be disorganized and more persistent in
some areas compared to others, even though central PR is expected to
have the more persistent shower activity.

The latest guidance has backed off a bit on the moisture that is
expected on Tuesday, with Precipitable Water values remaining under
1.4 inches. However, shower activity is still expected to develop
over the local area, and in more organized and predictable fashion
that is the case today since there is a more defined wind direction
expected, from the east to ENE, and at 10 to 15 KT. This will cause
showers across the local Atlantic waters and afternoon convection to
occur across central to western and southwestern Puerto Rico. For
Wednesday, the local waters will have plenty of moisture, and shower
activity is expected over the local waters and the USVI. However,
relatively deep moisture could move into PR on Wednesday afternoon
from the south, helping the development of scattered showers over
southern PR.

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

Model guidance persists on a wetter unstable weather pattern by
the end of the workweek into the weekend. GFS continues to be more
bullish with ECMWF lagging behind but slowly converging with GFS
solution. Latest ECMWF run has now an increased window of time
for this wetter unstable event coinciding with GFS from Thursday
through the end of the weekend. Thursday starts with a mid to
upper level trough just northwest of the forecast area and an
upper-level jet with winds of 70 to 80 kts over the northeast
Caribbean basin. The trough will strengthen and move closer to
the region through the weekend promoting favorable conditions
aloft for development of deep convection. Temperatures at 500 mb
are expected to plummet to below -10 degree celsius with steeper
850-700 mb lapse rates.

At low-levels, remnants from an old frontal boundary will
combine with the surface induced trough. Moisture in the atmospheric
column is expected to increase reaching values two standard
deviations above normal for this time of year by Thursday evening
through Sunday. Uncertainty remains regarding the positioning of
this induced trough which continues to change between model cycles
with most solutions putting it over the offshore Atlantic waters but
some recent runs bringing it closer to Puerto Rico and U.S.
Virgin Islands. This will determine moisture convergence across
the area enhancing the potential for heavy rain. GFS latest run
has winds between 30 to 35 knots across portions of the offshore
Atlantic waters related to the strengthening of the surface
induced trough by late Thursday night into early Friday. ECMWF has
it farther north with lower winds across the CWA. Therefore,
winds have been capped to 20 knots but will need to be monitored
as we get closer to the forecast period.

If this forecast persists, expect widespread shower and thunderstorm
activity across the area with the possibility of those
thunderstorms to be scattered at times. Forecast confidence on the
specific impacts this feature will bring to the CWA is low due to
significant model variability on positioning of the trough. That
said, a wetter unstable weather pattern and the potential for
significant rainfall accumulations are becoming more likely as we
approach the end of the workweek into the weekend. Thus, continue
to monitor our forecasts over the next couple of days.

By early next week, a gradual transition into a more stable
weather pattern can be expected as the mid- to upper-level trough
moves eastward and gets replaced by ridging aloft. Lingering
moisture could still produce shower activity each afternoon as it
gets enhanced by surface heating and sea breeze convergence.


&&

.AVIATION...

VFR conditions expected across the local TAF sites through the
forecast period. ISOL/SCT showers will move into the local flying
area, causing VCSH at the TIST and TISX terminals through the day.
VCSH is also possible at TJSJ and TJBQ after 31/10Z and 31/17Z
respectively. Light winds of 10KT or less are expected with a strong
sea breeze variation in PR, but SE winds expected across the USVI
today.

&&

.MARINE...A northwest swell will move across the local Atlantic
waters today through Tuesday. Seas are forecast to build around 7
feet, and small craft advisories are in effect. Light to gentle
winds are forecast through early in the week. The swell will cause
rough surf and life-threatening rip currents across the Atlantic
exposed coastlines of the islands during the next couple of days.
For detailed information please refer to the latest Coastal Hazard
Message (CFWSJU), and Surf Zone Forecast (SRFSJU).


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 72 84 73 / 40 30 30 20
STT 81 73 80 73 / 40 40 30 20
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