Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
432 AM AST Wed Jan 20 2021

.SYNOPSIS...

A moist air mass will promote passing showers across the windward
sections through the morning hours. Shower activity is then
forecast to diminish by this afternoon into the evening hours when
a drier air mass is forecast to arrive. Although stable weather
conditions will continue through the forecast period, pockets of
moisture embedded in the trades will reach the islands from time
to time.

&&

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

Latest GOES-16 Total Precipitable Water imagery shows an area of
enhanced moisture moving across Puerto Rico. This has resulted in
passing shower activity affecting mainly the northern half of Puerto
Rico during the overnight hours. This pocket of moisture is expected
to quickly move out of the area during the early morning hours, with
an area of drier air quickly following behind and remaining over the
area through tonight. Therefore, from the mid-morning hours onwards,
mainly fair weather conditions with very little shower activity are
expected. A few showers cannot be ruled out across western Puerto
Rico this afternoon.

At mid to upper-levels, a polar trough is forecast to move across
the western Atlantic later today into tomorrow, weakening the mid-
level ridge somewhat. The polar trough will drive a surface low-
pressure and an associated front across the western Atlantic,
weakening the pressure gradient and thus the low-level steering
flow. Another patch of low-level moisture is expected to move across
the area on Thursday and combined with a lighter steering flow,
there is a better potential to observe afternoon convection across
interior, western and southwestern portions of Puerto Rico as the
available moisture will combine with diurnal heating and local
effects. Below normal moisture then moves across the area for Friday
and thus limited shower activity can be expected once again.
However, some afternoon convection cannot be ruled out across
portions of western Puerto Rico.

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

The mid-level high will remain in place, promoting subsidence and
dry air aloft. At the surface, pockets of moisture embedded in the
trades will bring clouds and showers from time to time. However,
due to the mid-level high, do not anticipate organized convection
across the region.

A surface-high pressure, moving from the Eastern Seaboard into the
Atlantic, will sink southward the remnants of an old boundary,
keeping it to the north of the islands Sunday through mid-week.
Model guidance has been very inconsistent with the moisture field
through the long-term period.

&&

.AVIATION...

Mainly VFR conditions expected across the local terminals. Passing
SHRA will continue to affect portions of the northern half of PR
through 20/12z, resulting in VCSH across TJSJ and TJBQ. Brief MVFR
conditions cannot be ruled with these passing SHRA. Thereafter,
mainly fair wx conditions expected through the rest of the period.
Winds will continue from the E-ENE below 10 kts through 20/12z,
increasing to up to 15 kts with sea breeze variations after
20/14z.

&&

.MARINE...

The northerly swell is subsiding across the local waters. However,
moderate to locally fresh easterly winds will create choppy seas
of up to 6 feet today. Therefore, small craft operators should
exercise caution across most of the local waters.

A surface-low moving across the western Atlantic will loosen the
local pressure gradient, promoting light to moderate trades across
the local islands. As a result, the seas will also improve.

Beachgoers, there is a high risk of rip currents along the north-
facing beaches of Puerto Rico and Culebra. It`s moderate for most
of the north and east-facing coasts.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 73 84 74 / 30 30 30 30
STT 85 73 84 72 / 10 30 30 10

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
441 AM AST Thu Jan 21 2021

.SYNOPSIS...A patch of low-level moisture will enhance cloudiness
and a slightly higher chance for showers today, but significant
wetting rains are not anticipated. Although intermittent patches
of drier air and low-level moisture will continue to stream across
the region, mainly fair weather conditions will prevail during the
next few days. Light to moderate winds will also prevail, along
with generally tranquil marine and coastal conditions.


&&

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

Drier air has been moving over Puerto Rico tonight, but a patch of
moisture is present over the USVI. This is causing fair weather over
Puerto Rico, while the USVI observes isolated and brief shower
activity. This small patch of moisture over the USVI is expected
to continue through the morning hours, but the moisture over
Puerto Rico will increase as the day progresses. This increase in
moisture will result in a gradual increase in shower activity over
PR, especially across the higher elevations and the southwestern
quadrant of PR. That said, the showers are not expected to be
heavy or persistent enough to cause flooding, though some ponding
of water will not be ruled out. The daytime temps are expected to
be near normal, with the lower elevations being in the low to mid
80s while the higher elevations will be in the mid 70s to low 80s.

At mid to upper-levels, a polar trough is forecast to move across
the western Atlantic early today as it moves away. A mid and upper
level ridge will gradually move over the area by Friday. Below
normal moisture will move in over the local area on Friday and
through the weekend, causing only a slight chance of rain for the
local area. However, scattered showers in the afternoon is forecast
across the interior sections and western Puerto Rico on Friday.

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

Model guidance suggests that mainly fair and stable weather
conditions will dominate the region through the long-term
forecast period. However, patches of low- level moisture embedded
in the trade winds will bring brief periods of cloudiness and
isolated to scattered shower activity from time-to-time. A slight
enhancement of moisture along with increased cloudiness and
shower activity may be expected between Tuesday and Thursday as the
remnants of an old frontal boundary move into the forecast area.
However, model guidance does not suggest significant moisture
content, with model- estimated precipitable water vapor briefly
fluctuating from less than an inch on Monday to 1.30 inches by
Thursday afternoon. Mid-level ridging will promote subsidence and
drier air aloft, conditions that will limit any chance for
organized convective development, even with the highest available
moisture. That said, significant wetting rains are not
anticipated, which will enhance further dryness of soil and
fuels, while promoting favorable fire weather conditions.

&&

.AVIATION...Mainly VFR conditions expected across the local
terminals. Passing SHRA will continue to affect the vicinity of the
USVI terminals this morning. Light and VRB winds will be observed
until around 21/12Z, with East winds with sea breeze variations at
around 10 KT thereafter until around 21/22Z.


&&

.MARINE...Small craft operators are urged to exercise caution due
to choppy seas up to 6 feet across the outer Atlantic waters today.
Elsewhere, tranquil marine conditions with seas up to 5 feet will
prevail through early next week. Another northerly swell will
invade the regional waters by Friday into the weekend, but seas
will remain below Small Craft Criteria. Light to moderate winds
will also prevail, fluctuating between 5 and 15 knots from the
east to northeast during the next few days. In Puerto Rico, a
moderate risk of rip currents continues for beaches along the
north and southeast coast of Puerto Rico, eastern-half of Vieques
and all beaches in Culebra. In the USVi, a moderate risk of rip
currents continues for beaches along the northwest coast of Saint
Thomas and eastern Saint Croix.


&&

.FIRE WEATHER...Since a patch of low-level moisture is forecast
to stream across the region, relative humidity should remain above
fire danger thresholds, while surface winds are forecast to
remain below 15 mph. Although KBDI values are quickly approaching
fire danger thresholds and significant wetting rains are not
anticipated, low fire danger conditions will hold today.

Nonetheless, lack of significant wetting rains in both short- and
long- term periods will support further dryness of soils and
fuels, while promoting favorable fire weather conditions during
the upcoming days. That said, an elevated to critical fire danger
threat can be expected in the near future.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 74 85 72 / 30 30 30 20
STT 84 72 84 72 / 30 10 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
430 AM AST Fri Jan 22 2021

.SYNOPSIS...Mainly fair weather conditions with patches of low-
level moisture enhancing cloudiness and isolated to scattered
shower activity from time-to-time will be the dominant weather
pattern during the next few days. Remnants of a cold front will
drift across the area by midweek, but significant rainfall
accumulations are not anticipated. Winds will remain light to
moderate from the east to northeast, while choppy marine
conditions along with a moderate to high risk of rip currents
will continue through Saturday.


&&

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

At mid to upper levels, a polar trough is moving east and away from
the local islands, while a ridge starts to gradually move in over
the local islands. Below normal moisture will move in over the local
area today and persist through the weekend, causing only a slight
chance of rain for the local area. However, scattered showers in the
afternoon is forecast across the interior sections and western
Puerto Rico this afternoon.

Drier than normal air is present over Puerto Rico. This is causing
mainly fair weather over Puerto Rico and the USVI, but isolated
light showers are occurring over the local waters. That said,
slightly higher moisture is being observed over the local waters,
and is expected to continue over the waters through the day, which
may cause a continuation of isolated waters over the waters. Also,
slightly higher moisture is expected this afternoon across the
western half of Puerto Rico, and thus scattered showers are forecast
across central to western PR this afternoon. According to the hi-res
guidance, some areas may observe enough rain to cause ponding of
water on roadways and poor drainage areas. The daytime temps are
expected to be near normal, with the lower elevations being in the
low to mid 80s while the higher elevations will be in the mid 70s to
low 80s. For Saturday and Sunday, even drier air is expected for the
weekend, and little to no shower activity is expected across the
local islands. Fair weather will prevail this weekend. The wind will
remain moderate but the easterly winds will become more
northeasterly on Sunday. Daytime and nighttime temps will be near
normal.

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

Model guidance continues to suggest that mainly fair and stable
weather conditions will dominate the local weather conditions
through most of the long-term forecast period, with patches of
low-level moisture generating brief periods of cloudiness and
isolated to scattered shower activity from time-to- time. The
frequency of patches of low-level moisture may increase by
midweek as the remnants of an old frontal boundary drift into the
forecast area. However, model guidance does not suggest
significant moisture content, with model- estimated precipitable
water vapor briefly peaking around 1.30 inches by Thursday
afternoon. Mid-level ridging will promote subsidence and drier
air aloft, conditions that will also limit any chance for
organized convective development. That said, significant wetting
rains are not anticipated through at least Friday afternoon,
which will continue to support further deterioration of soils and
fuels moisture, while promoting favorable fire weather conditions.

Thereafter, model guidance suggests that the remnants of yet
another frontal boundary will drift into the forecast area by
Friday night. Under somewhat favorable conditions aloft and
enhanced moisture content, there may be a higher chance for significant
wetting rains. However, it is too soon and there is low
confidence in the impacts, if any, this feature could bring to our
area.


&&

.AVIATION...Mainly VFR conditions expected across the local
terminals. Brief -SHRA will continue near the vicinity of the USVI
terminals this morning. VCSH possible at TJPS and TJSJ after 22/16Z
as SCT SHRA develop over portions of PR. Light and VRB winds will be
observed until around 22/12Z, but East winds and sea breeze
variations at around 10 KT are expected thereafter until around
22/22Z. FEW to SCT SKY expected today.


&&

.MARINE...Light to moderate winds at 5-15 knots are expected
across the local waters during the next few days. Fairly tranquil
marine conditions will prevail across most of the local waters
through the end of the week. However, a small northerly swell will
invade the Atlantic waters today into early Saturday, creating
choppy seas across the outer Atlantic waters where small craft
operators are urged to exercise caution. There is a moderate risk
of rip currents for beaches along the north coast of Puerto Rico,
eastern coast of Vieques, all coasts of Culebra, and western coast
of Saint Thomas. The risk will elevate to high for beaches along
the north coast of Puerto Rico this evening.


&&

.FIRE WEATHER...KBDI continues to approach fire danger thresholds,
with a potential to surpass 550 for Camp Santiago today. Although
significant wetting rains are not anticipated and relative
humidity may drop into the mid to upper 40s across the southern
coastal plains of Puerto Rico, winds are forecast to remain below
15 mph. Overall, the expected weather pattern appears marginal
for fire weather conditions, but the threat should remain low
today. Nevertheless, lack of wetting rains will continue to
support further deterioration of soils and fuel moisture, with a
chance to favor an elevated to critical fire danger threat within
the next few days.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 73 85 75 / 30 20 20 20
STT 83 72 83 72 / 30 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
430 AM AST Sun Jan 24 2021

.SYNOPSIS...Fair and stable weather conditions with limited
shower activity are expected through early next week. The
remnants of a weak cold front are forecast to linger across the
region Tuesday through Thursday, merging with the remnants of yet
another, but stronger frontal boundary by the end of the workweek
into the upcoming weekend, supporting a higher chance for
showers. Winds will remain light to moderate from the east to
northeast through Monday, increasing thereafter. Tranquil marine
conditions along with a moderate risk of rip currents will
continue today.


&&

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

There is a weak area of high pressure at the surface north of the
local islands, which is causing light to moderate northeasterly
winds across the local area. For Monday and Tuesday, a stronger SFC
high pressure will be present across the southwestern Atlantic,
causing stronger northeasterly winds across the local islands.
Stable conditions are currently observed as a ridge dominated the
mid and upper levels. According to the latest forecast soundings,
near to below normal moisture are still expected over the local area
for the next few days, with the limited moisture available mainly
being in the lower levels. This combination of patterns is causing
mainly fair weather over Puerto Rico and the USVI, with only
isolated light showers occurring over the local waters during the
night and early morning hours. However, for today, the hi-res models
seem to be much more bullish in the rainfall forecast compared to
the global models, mainly due to the local effects and diurnal
heating over Puerto Rico. The NMM model was so bullish in the
afternoon rainfall over W-SW PR, that it was difficult to ignore and
thus scattered showers are in the forecast across central to the
southwestern quadrant of PR for this afternoon. The other hi-res
model, the ARW agrees with the NMM on the location of rain, but it
has less amount of rain in the solution.

As winds become stronger on Monday, the shower activity is expected
to be mainly isolated and brief through the day. There is only a
slight chance of rain on Monday afternoon, as the stronger NE winds
should reduce the chances of sea breeze convergence over the SW
portions of PR. Isolated and brief showers are forecast elsewhere in
the local area through the day on Monday. However, on Tuesday, the
remnants of a frontal boundary will be approaching the local area.
Cloudiness and rainfall as well as available moisture is expected to
increase. That said, the area with higher moisture and rainfall is
limited to a narrow band, which will move through the local area
during the day on Tuesday. At this time, it looks like there will be
an increase in shower activity, but the rainfall accumulations are
not looking like it would cause hazardous conditions more than some
ponding of water in poor drainage areas.

The daytime temps are expected to be near normal for the next few
days, with the lower elevations observing daytime temps in the low
to mid 80s and lows in the upper 60s to low 70s; while the higher
elevations will have high temps in the mid 70s to low 80s, and
overnight lows in the upper 50s to mid 60s.

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

Model guidance continues to suggest that a relatively moist
weather pattern will dominate, particularly by the end of the
workweek into the weekend. A surface high pressure streaming
across the western Atlantic will push the remnants of an old
frontal boundary southward across the local islands into the
northeastern Caribbean on Wednesday into Thursday, promoting
periods of increased cloudiness and isolated to scattered shower
activity from time-to-time. As the aforementioned high moves away
into the north central Atlantic and a frontal boundary approaches
the region from the northwest, winds are to decrease and turn
from the east to southeast, trapping an area of near normal
moisture over the local islands through Friday. Further increase
in moisture is expected thereafter as the remnants of the
aforementioned frontal boundary move in along with the weakening
of the trade wind cap that results from the passage of a deep
polar trough. The combination of favorable conditions aloft with
above normal moisture, with model-estimated PW values ranging
from 1.5 inches on Friday morning to around 1.8 inches by Saturday
night, will support 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 rain event of the year.


&&

.AVIATION...VFR conditions expected across the local terminals for
the next 24 hours. Brief ISOL -SHRA is possible over the local
flying area this morning, which could cause light and brief VCSH.
VCSH possible at TJPS after 24/18Z as SCT SHRA develop over portions
of south and west PR. Light and VRB winds will be observed until
around 24/12Z, but NE winds and sea breeze variations at around 10
KT are expected thereafter until around 24/22Z. FEW to SCT SKY
expected today.


&&

.MARINE...Tranquil marine conditions with seas up to 5 feet are
expected today, turning choppy up to 6 feet for the outer
Atlantic waters tonight into Monday. Thereafter, another swell is
expected to invade the regional waters, generating choppy to
hazardous seas that may require the issuance of Small Craft
Advisories. Winds will remain light to moderate from the east to
northeast through Monday, increasing to 10-20 knots by Monday
night. There is a moderate risk of rip currents for beaches along
the north coast of Puerto Rico, all beaches in Culebra, eastern
beaches of Vieques, north beaches of San Thomas and northwestern
beaches of Saint Croix.


&&

.FIRE WEATHER...Drier air will continue to move into the region,
limiting any chance for wetting rains and causing relative
humidity to drop into the mid 40s to near 50 percent, while
promoting further deterioration of soils and fuel moisture across
the southern coastal plains of Puerto Rico. Although winds are
expected to remain generally light, sea breeze variations will
cause winds to peak around 15 mph between the late morning and
early afternoon hours. Both KBDI and 10-Hour Fuel Moisture values
at Camp Santiago have reached already elevated thresholds during
the previous day with 558 and 8 percent, respectively. Based in
the expected weather conditions and recent drying pattern, a Fire
Danger Statement has been issued for elevated fire danger conditions
expected across the southern coastal plains of Puerto Rico today.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 73 83 73 / 10 20 20 30
STT 83 73 83 72 / 10 20 30 10

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
430 AM AST Mon Jan 25 2021

.SYNOPSIS...
Quick passing showers will continue over the morning hours, mostly
over windward sections of Puerto Rico and the U.S. Virgin Islands.
In the afternoon hours, diurnal shower activity is forecast across
the interior and western portions of Puerto Rico. Tranquil marine
conditions today with seas up to 5 feet in all the local waters.
However, more choppy marine conditions are expected on Tuesday as
a northerly swell invade the Atlantic waters.

&&

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

A broad surface high pressure ridge spread across the west and
southwest Atlantic and a weak frontal boundary and associated
troughiness across the central Atlantic, will continue to induce
light to moderate northeasterly winds across the region through the
forecast period. This pattern will help to create an area of low
level convergence which in turn will aid in transporting occasional
patches of trade wind moisture from old frontal boundaries across
the region from time to time.

The first patch of moisture was now crossing the region and will
continue to bring periods of passing showers to the north and east
coastal areas of Puerto Rico and adjacent islands, as well as the
northern U.S. Virgin Islands. Expect this cloudiness and quick
passing shower activity to diminish by late morning, leading to
partly cloudy to mostly sunny skies for much of the islands during
the rest of the day. Available moisture along with local and diurnal
effects will however support isolated to scattered afternoon shower
development over parts of the central interior and southwest
sections of Puerto Rico, and mainly downwind of the remaining
islands...except for Saint Croix where there is a better chance for
isolated afternoon showers. No significant rainfall accumulations
are anticipated at this time except for ponding of water on roadways
and in poor drainage areas.

On Tuesday , recent model guidance continued to suggest yet another
solid band of moisture along an old frontal boundary/shearline will
sink southwards and reach the islands by early Tuesday. This will
bring an increase in cloudiness as well as better chance for shower
activity with potential for periods of moderate to locally heavy
rains along the north and east coastal areas during the morning
hours. This band of of moisture is to linger across the region
during the day, but moisture will gradually erode late Tuesday into
Wednesday, as the surface high builds north of the region and the
northeasterly wind flow increase in response to the strengthening
surface high pressure ridge across the western Atlantic.
Consequently, expect improving conditions and a drier and stable
weather pattern again on Wednesday, with limited afternoon
convection which should be focused to mainly over parts of the
central and southwest sections of Puerto Rico. Mostly fair weather
skies and seasonal conditions will prevail for the rest for the
islands.

Daytime temperature are expected to be near normal during the
period, with the lower elevations and coastal areas observing temps
in the low to mid 80s and lows in the upper 60s to low 70s. while
the higher elevations will have high temps in the mid 70s to low
80s, and overnight lows in the upper 50s to mid 60s.

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

A surface-high pressure located over the central Atlantic will
dominate the local weather under drier mass filtering across the
region until early Friday. In general, expect fair weather
conditions with the typical morning showers over eastern Puerto
Rico and the U.S. Virgin Islands and the diurnal afternoon
showers. As the ridge moves eastward, a low pressure located well
north in the Atlantic will push a frontal boundary more into the
area. On Saturday, another high building pressure over the Florida
Peninsula will move the frontal boundary remnants over the
region. According to model guidance, an increase of moisture at
700-850 MB is expect over the local area for the upcoming weekend.
This increase in low level moisture will result in shower
activity over the local waters and the U.S. Virgin Islands in the
morning and evening hours. Then, in the afternoon hours, scattered
showers are expected over Puerto Rico. On Monday, as the ridge
moves eastward, a change in winds is expected, turning more to the
east- southeast. This change in the wind direction will result in
warmer mostly over the coastal sections of Puerto Rico and the
USVI. Shower activity could be possible on late Monday as
lingering moisture embedded in the winds reach the local islands
and combine with the local effects.


&&

.AVIATION...
Prevailing VFR at all terminals durg prd. SCT ocnl BKN
lyrs nr FL025...FL050...SHRA/-SHRA ovr regional waters and en route
btw islands til 25/14Z. VCSH mainly at TJSJ/TIST/TISX/TNCM 25/14z...
and at TJMZ fm 25/17Z-25/22Z. Sfc wnds fm E-NE at 10 kts or
less..bcmg fm NE 10-15 kts w/ocnly hir gust aft 25/14Z.

&&

.MARINE...
Expect for today, tranquil marine conditions with seas up to 5
feet or less across all the regional waters. On Tuesday, a
northerly swell is forecast to invade the Atlantic offshore waters
and local passages with seas between 5 to 7 feet and winds up to
15 knots. Therefore, small craft advisories are in effect, and a
high risk of rip current for the north-facing beaches of Puerto
Rico, all the beaches on Culebra and San Thomas. These conditions
will last until mid-week before another vigorous northerly swell
invade the local waters on the upcoming weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 74 81 72 / 30 70 70 30
STT 83 73 82 71 / 30 60 60 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
543 AM AST Tue Jan 26 2021

.SYNOPSIS...
A broad high pressure over the southwestern Atlantic will push the
remnants of a frontal boundary over the region. This increase in
moisture will result in more potential for shower development over
the local islands. Expect isolated to scattered showers in the
morning hours over the north and eastern sections of Puerto Rico
and the U.S. Virgin Islands` windward sections. With the
combination of moderate wind flow and a northerly swell invading
the local waters, hazardous marine conditions will prevail for the
Atlantic waters and local passages.

&&

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

A broad surface high pressure ridge across the west Atlantic will
shift eastwards into the central Atlantic today through Wednesday to
maintain a light to moderate east northeast low level wind flow.
This will aid in pushing the remnants of an old frontal
boundary/shearline southwards across the region resulting in an
increase in low level cloudiness as well as increasing potential for
periods of passing showers by late morning and into the early
afternoon hours. Recent satellite imagery and the doppler weather
radar showed the associated band of frontal moisture over the local
Atlantic waters, just north of the Puerto Rico and the northern U.S.
Virgin Islands. Expect showers to affect the northern and eastern
section of Puerto Rico and mainly the northern U.S. Virgin Islands
later this morning, then shifting to portions of the central
interior, southwest and southern slopes of Puerto Rico, including
around the island of Saint Croix later in the afternoon. While
significant and widespread rainfall is not anticipated, periods of
moderate to locally heavy rains will be possible. This may cause
ponding of water on roadways in poor drainage areas as well as a
slight chance for minor urban flooding in isolated spots.

This band of moisture is forecast to gradually erode and diminish by
late afternoon and into Wednesday, as the surface high reestablishes
north of the region and the northeasterly winds increase in response
to the strengthening surface high pressure ridge. Expect improving
conditions and a much drier and stable airmass again on Wednesday,
with limited afternoon convection. The showers should be focused to
mainly over parts of the central and west to southwest sections of
Puerto Rico. Mostly fair weather skies and seasonal conditions will
prevail for the remainder of the islands. Similar weather conditions
are expected for Thursday, however a slight shift in the prevailing
low level wind flow as it briefly becomes more from the east
southeast will bring a small patch of moisture across the region
once again by early Thursday. Therefore there will be sufficient
pockets of moisture present for locally and diurnally induced
isolated to scattered afternoon convection mainly over the west
interior sections of Puerto Rico and mainly around the islands of
Saint Croix or just downwind of the remaining islands. Elsewhere
mostly fair weather skies are forecast to prevail.

During the period more seasonal temperatures can be expected, with
the coastal areas observing temps in the low to mid 80s and lows in
the upper 60s to low 70s,while higher elevations will have high
temps in the mid 70s to low 80s, and overnight lows in the upper 50s
to mid 60s.

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

A surface-high pressure located over the central Atlantic will
dominate the local weather under drier mass filtering across the
region on Friday. As the drier air mass moves over the area,
precipitable water values will remain below normal, resulting in
less shower activity over the local islands. As the broad surface
high pressure moves eastward, this will push the remnants of a
frontal boundary over the forecast area. This low level moisture
in combination with tropical moisture embedded in northeastern
winds will result in a wet weather pattern for the weekend.
According to model guidance, precipitable water values will range
above normal values. That said, isolated to scattered showers
could affect Puerto Rico and the U.S. Virgin Islands windward
sections in the morning and evening hours. In the afternoon hours,
the shower activity will focus on the interior and southwestern
portions. If the model guidances are correct, the upcoming weekend
looks with moderate flood potential, mainly over interior
portions of Puerto Rico.

As the ridge moves eastward to the central Atlantic on late
Monday, a southeasterly component is expected. Therefore, expect
an improvement in weather conditions as the low-level moisture
exit the area due to the wind change. However, on Tuesday, some
tropical moisture patches will reach the local islands and,
combined with the local effects, could result in afternoon
showers. This change in the wind direction will also result in
warmer temperatures, mostly over the coastal sections of Puerto
Rico and the USVI.

&&

.AVIATION...
VFR conds will prevail at local terminals but expect
incr in low level cloudiness with SCT-BKN lyrs nr FL025...FL050, as
remnants from old frontal boundary sinks southwards across the
region. Wdly sct SHRA along frontal boundary just N of Puerto Rico
with VCSH mainly at TJSJ/TJBQ/TIST til 26/15Z. Sfc wnds less than 10
kts but incr to 10-15 knots with ocnly higher gusts after 26/14z.
Isold-SCT SHRA ovr ctrl interior section of PR later in the day may
cause brief Mtn Top Obscr in SHRA/Low cld lyrs BTW FL025-FL040.
Otherwise no sig operational wx impact at local terminals.


&&

.MARINE...
A northerly swell will invade the local waters resulting in
hazardous marine conditions. Therefore, mariners can expect seas
up to 8 feet over the Atlantic waters and local Caribbean waters,
and for the rest of the area, seas will remain up to 6 feet or
less. Winds will continue from the northeast at 10 to 20 knots.
Therefore, small Craft Advisories are in effect for the Atlantic
Offshore waters and local passages through mid-week. There is a
high risk of currents for all the local beaches on the north,
east, and west of Puerto Rico, Culebra, and San Thomas. These
conditions will last until mid-week before another northerly swell
invade the local waters on the upcoming weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 73 83 72 / 70 30 20 20
STT 83 72 83 72 / 60 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
503 AM AST Wed Jan 27 2021

.SYNOPSIS...
A high surface pressure located over the west-central Atlantic
will dominate the weather pattern for the next several days. This
aforementioned feature will result in drier conditions aloft,
limiting the shower activity over the local Islands. However, some
quick passing showers will be possible during the afternoon hours
over the interior and western sections of Puerto Rico, mainly due
to the local effects. Hazardous marine conditions will prevail
today, with small craft and high surf advisories in effect and
high risk of rip currents for the north-facing beaches of Puerto
Rico, Culebra and San Thomas.

&&

.SHORT TERM...Today through Friday

Mid-upper level ridge centered over the west and central Caribbean
will maintain its hold across the region today into Thursday. This
will result in a dry and stable airmass aloft, along with a fairly
strong cap inversion. In the low levels, a broad surface high
pressure north of the region, will shift farther east into the
central Atlantic while maintaining a moderate east to northeast wind
flow through Thursday. The prevailing winds a forecast to become
light and more easterly by Friday as the Atlantic ridge north of the
region weakens and the local pressure gradient relaxes. This is also
in response to a cold front forecast to enter and move across the
west Atlantic Thursday through Friday.

Model guidance as well as recent satellite imagery, doppler weather
radar and the satellite derived precipitable water products, all
suggest an overall dry airmass with precipitable water values below
one inch. Therefore, an overall dry weather pattern and mostly sunny
skies can be expected for today and into Thursday with little or no
precipitation forecast in and around the islands. However, later
tonight into early Thursday, patches of shallow low-level moisture
associated the remnants of the frontal boundary south of the region
may return and affect mainly the island of Saint Croix and parts of
eastern Puerto Rico. This may result in brief periods of light to
moderate showers in isolated areas. However, no significant
rainfall accumulations are anticipated.

For Thursday, the low-level winds are expected to weaken and become
more east to southeast, as a surface low pressure and the associated
cold front moves across the western Atlantic. This along with the
aforementioned surface high pressure shifting into the central
Atlantic, will promote light trade winds and weak low-level
troughiness across the region. Therefore, a dry airmass and mostly
sunny skies with limited shower activity can be expected in most
areas, with precipitable water values forecast to remain at or below
1.0 inch.

By Friday as the cold front weakens across the Atlantic and north of
the region, expect a frontal boundary and associated shear line to
set up and gradually sink southwards towards the area. In the
meantime, the upper level ridge is to erode in response to a polar
tough crossing the west Atlantic while becoming amplified across the
forecast area. This overall change in the weather pattern will
result in increasing instability aloft, along with good low level
convergence. As the frontal boundary/shear line approaches the
region expect increasing low level moisture pooling and consequently
better chance for early morning and afternoon shower development, as
well as better potential from urban and small stream flooding in
isolated areas during the day.

.LONG TERM...Saturday through Wednesday

A broad surface high pressure located over the western Atlantic
will continue to dominate the local weather pattern for the long
term period. As the ridge moves eastward will push the remnants of
a frontal boundary over the region. Simultaneously, the northeasterly
wind flow will drive tropical moisture over the area and combine
with the frontal remnants on Sunday. That said, Sunday looks like
the best day for widespread shower activity for the local Islands.
Therefore, scattered to numerous showers are forecast for the
interior and western sections of Puerto Rico in the afternoon
hours. If the model guidances are correct, Sunday will have a
moderate potential for urban and small stream flooding, mainly
over the eastern and western portions of Puerto Rico.

As the high surface pressure moves eastward into the central
Atlantic drier airmass will filter in across the area, bringing
stable conditions aloft for the rest of the long term period.
Therefore, mainly fair weather conditions are expected, with a few
passing showers over interior and northwestern sections of Puerto
Rico in the afternoon hours. Additionally, a southeasterly component
in winds is forecast for Monday through Tuesday. This wind flow
will promote slightly warmer temperatures over the region on
Monday through Wednesday.


&&

.AVIATION...

VFR durg prd. Sfc wnds fm northeast at lass than 10
kts...bcmg 15 to 20 knots with higher gusts after 27/14z. wdly SCT
lyrs nr FL030...FL050. Isold SHRA ovr regional waters btw islands.
No sig operational wx impacts.


&&

.MARINE...

Hazardous marine conditions will continue across the Atlantic
waters and local passages today, as the combination of a northerly
swell continues to invade the local waters. Mariners can expect
seas up to 7 feet across Atlantic waters and local Caribbean
passages and up to 6 feet elsewhere. There is a high surf advisory
for the north facing Puerto Rico and Culebra`s local beaches with
large breaking waves between 8-10 feet until early this morning.
Additionally, there are a high risk of rip current or north-facing
Puerto Rico beaches for the next several days. These conditions
will improve on Thursday, and seas between 3 to 5 feet will
dominate the local waters before another northerly swell invade
the local waters on the upcoming weekend.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 82 73 85 73 / 20 20 20 20
STT 82 72 81 71 / 20 10 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
522 AM AST Thu Jan 28 2021

.SYNOPSIS...
Broad high pressure spread across the Atlantic and north of the
region, together with an overall dry and stable airmass in place
will continue to promote a mostly fair and sunny weather pattern
across the forecast area today through Friday. Winds will continue
from the east-northeast with sea breeze variations today and for
the rest of the work week. Weather conditions are forecast to
deteriorate by Saturday and through the weekend with the approach
of a frontal boundary and the erosion of the upper level ridge,
as a polar trough and associated frontal boundary will cross the
western Atlantic.

&&

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

A broad mid-upper level ridge now located over the central Atlantic
will dominate the local pattern today. Goes-16 satellite imagery
derived data continues to suggest for today, low values for
precipitable water below 1.0 inches. Therefore, mainly fair weather
conditions are expected, with a few passing showers, if any, over
northwestern sections of Puerto Rico in the afternoon hours.
Additionally, as the elongated ridge exit the area, a more
southeasterly component in winds is forecast this afternoon. In
combination with clear skies, this wind flow will promote slightly
warmer temperatures over the coastal sections today.

On Saturday, another building surface ridge will move eastward,
creating a northeasterly wind over the area. This wind flow will
carry some patches of moisture over the region. Still, no
significant rainfall activity expected due to the drier conditions
aloft, limiting the potential for long-live showers. However,
typical afternoon activity could be possible over the north sections
of Puerto Rico. As the high surface pressure moves eastward,
remnants of an old frontal boundary will reach the local islands.
These remnants combined with more tropical moisture between 700-850
MB will reach the local Islands at advanced afternoon hours on
Saturday. Given these patches of cloudiness and showers are present
in the forecast area, there is a potential for more shower activity.
That said, Saturday evening will be the best wet day for the short
term period. Therefore, scattered to numerous showers are forecast
for the eastern sections of Puerto Rico and the U.S. Virgin Islands.

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

The broad surface high pressure over the west and central Atlantic
will continue to dominate the local weather pattern during the period.
As the ridge moves eastward, it will continue to push remnants of
a frontal boundary across the area bringing an increase in low level
cloudiness. Simultaneously, the northeasterly wind flow will aid in
creating good low level moisture convergence across the region.
In addition, the broad polar trough will settle across the region
through Sunday and thus maintain unstable conditions aloft and
providing sufficient ventilation and upper level divergence.

Consequently a wet weather pattern is expected through at Sunday
with a gradual improvement in the overall weather conditions by
the early part of the following week. Sunday still has good potential
for widespread shower activity across much of the islands based on
recent model guidance. Scattered to numerous afternoon showers
are forecast for the interior and western to northwest sections of
Puerto Rico, including the San Juan metro area, as winds are
forecast to become more east-southeast. Therefore there will be a
moderate potential for urban and small stream flooding through
Sunday, mainly over the aformentioned areas.

As the surface high pressure moves farther eastward into the central
Atlantic, and the upper trough lifts farther northwards, a drier
airmass will filter in as winds become more southeasterly across
the area. This will cause an erosion of low level moisture and
bring stable conditions aloft for the rest of the long term
period. Therefore, mostly fair weather conditions are expected
with slightly warmer daytime high temperatures at least from
Monday through mid-week. A few passing showers will remain
possible during the overnight and early morning hours on the
windward side of the islands, followed by isolated to scattered
locally and diurnally induced afternoon showers over parts of the
interior and northwest-north sections of Puerto Rico.

&&

.AVIATION...
Mostly VRF conditions are expected across all the TAF sites
between 28/06z to 27/06z. Sfc winds will be mainly fm the E at
less than 10 kt....becoming E-NE at 10 to 15 kts aft 28/14Z with
sea breeze variations. VCSH could be mainly possible at TJBQ and
TJMZ fm 28/18Z-28/22Z.

&&

.MARINE...
Marine conditions will continue to improve throughout the day but
due to the gradually fading northerly swell and moderate to locally
fresh trade winds, small craft operators should continue to exercise
caution. Fairly tranquil seas overnight into early Friday.

A more vigorous northerly swell is forecast to invade the Atlantic
waters beginning Friday night and continuing into early next week.
This will result in very hazardous seas through the upcoming weekend.

High risk of rip currents continues across the north facing beaches
of Puerto Rico and Culebra, as well over St Thomas until this afternoon.
There is a moderate risk of rip currents for much of the other local
beaches.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 72 83 74 / 10 10 30 60
STT 81 71 82 72 / 20 20 30 50

[cycloneye]

Area Forecast Discussion...DELAYED
National Weather Service San Juan PR
537 AM AST Fri Jan 29 2021

.SYNOPSIS...A drier than normal air mass dominated the local area
overnight and will continue through the day as the region will
remain wedged between a surface high pressure ridge across the
southwest Atlantic, an approaching frontal boundary sweeping across
the west central Atlantic, and an old frontal boundary/shear line
south of the islands. Overall fair skies and sunny weather is forecast
for today with limited or no rainfall expected. The weather pattern
as well as marine and surf zone condtions is however expected to
rapidly deteriorate overnight and through the upcoming weekend due
to the increasing instability aloft, as the upper ridge erodes
and the aforementioned frontal boundaries and associated moisture
field merges and crosses the region resulting in increased low
level moisture convergence.

&&

.SHORT TERM...Tonight through Sunday...

As a high building pressure moves out from the western Atlantic into
the Central Atlantic, a more east-northeasterly wind flow will
dominate the local pattern. Once again, satellite imagery derived
layered precipitable water data continues to suggest, a much drier
airmass filtering into the area with PWAT(precipitable water
values) between 0.9 to 1.0 inches. That said, mostly fair weather
conditions and sunny skies will prevail over the local islands,
with only a chance for a few passing showers mainly over the local
waters. In the meantime, a pulse of low- level moisture from
remnants of an old frontal boundary south of the region, and the
arrival of the next frontal boundary northwest of the area, is
expected to merge across the region starting early Saturday. This
combination is expected to significantly increase the potential
for widespread shower activity over the area. For the U.S Virgin
Islands, the shower activity should start by early Saturday as
fragments of cloudiness and low-level moisture moves over the
area. The risk of moderate urban and small stream flooding will be
possible, especially on Sunday for all the local islands. The
daytime temps are expected to be slightly cooler today, due to
the east-northeast wind flow. That said, for today and the next
few days, the lower elevations could observe daytime temps in the
upper 70s the to mid 80s and lows in the mid 60s to low 70s; while
the higher elevations will have high temps in the low 70s to low
80s, and overnight lows in the upper 50s to mid 60s.

.LONG TERM...Monday through Friday...
An overall and gradual improvement in the weather conditions is
expected by Monday and through most of the following workweek with
only occasional fragments of low level moisture forecast to move
across the area carried by the trade winds which are expected to
be more east to southeast by the early part of the week then
become more east to northeast once again during the latter part
of the period. However for now, seas are forecast to remain choppy
and hazardous into the early part of nest week.

As the surface high pressure moves farther eastward into the
central Atlantic, and the upper trough lifts farther northwards, a
drier airmass will filter in as winds become more southeasterly
across the area. This will cause an erosion of low level moisture
and bring stable conditions aloft for most of the long term
period. Therefore, mostly fair weather conditions are expected
with slightly warmer daytime high temperatures at least from
Monday through mid-week as previously mentioned. A few passing
showers will remain possible during the overnight and early
morning hours on the windward side of the islands each day,
followed by isolated to scattered locally and diurnally induced
afternoon showers over parts of the interior and northwest-north
sections of Puerto Rico.Elsewhere mostly fair weather and sunny
skies will prevail.

&&

.AVIATION...Mostly VRF conditions are expected across all the TAF
sites between 29/06z to 29/14z. Sfc winds will be mainly fm the E at
less than 15 kt.... with sea breeze variations. VCSH and SHRA are
forecast mainly at TKPK,TNCM, TIST, TISX, and TJPS fm 29/18Z-30/06Z.

&&

.MARINE...Seas will be fairly tranquil most of the day. However,
rapid deterioration is expected later this evening and through
the weekend, with at arrival of a significant northerly swell, as
well as increasing northerly winds. For this reason a Small Craft
Advisory which will go into effect from 8 PM this evening for the
offshore Atlantic. Most of the remaining local waters and passages
will likely need Small Craft Advisories as well starting later
tonight or early Saturday morning. In addition, based on recent
model guidance, the significant northerly swell will arrive and
spread across the regional waters creating dangerously large
breaking waves, and perhaps even minor coastal flooding across the
north coast of PR and Saint Thomas starting as early as Saturday.
For the latest and most up to date information, please refer to
the Coastal Waters Forecast (CWFSJU), Marine Weather Message
(MWWSJU), and the Coastal Hazard message(CFWSJU) issued by the
National Weather Service WFO San Juan, as we will be closely
monitoring this expected event.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 82 74 80 73 / 10 50 60 70
STT 83 72 82 73 / 20 50 70 70

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
554 AM AST Sat Jan 30 2021

.SYNOPSIS...

An increase in clouds and showers is expected through tomorrow as
lingering moisture from an old frontal boundary combines with
moisture from an arriving frontal boundary. Weather conditions
will gradually improve by the beginning of the workweek. A
moderate to fresh east to northeast wind flow will prevail.
Hazardous marine and coastal conditions are expected today into
early next week as a vigorous northerly swell continues to invade
the local waters.

&&

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

Strong lows pulling northeast out of the north Atlantic will allow a
modest high to form on Sunday around 30 west north of Puerto Rico.
This in turn will hold a cold front now entering the northwestern
local Atlantic waters in the forecast area. The front has limited
moisture and current Total Precipitable Water product is showing no
more than 1.3 inches in the frontal band and less than one inch
ahead of the band over Puerto Rico. A band of moisture entering the
southeast portion of the forecast area will move into the islands
today and increase showers and across the area with the heaviest
amounts over the windward side of Puerto Rico tonight. Amounts of
one quarter to one half inch during the next 36 hours could be
common, but amounts over one inch may be seen in isolated areas of
eastern Puerto Rico. The U.S. Virgin Islands should see somewhat
less in any case. The frontal band is expected to return to the
Atlantic waters by Sunday, but low level flow will shift to east
southeast or southeast by Monday and this will bring other bands of
moisture and scattered showers through the area.

An upper level trough is positioned to move through this morning
then flow will generally shift to the west northwest. Areas of
divergence and convergence will move through the area during the
period, but convection will likely not be able to get much above 15
kft.

.LONG TERM...

Weather conditions will gradually improve through much of the
workweek as drier air filters in and the high surface pressure
stalls over the central Atlantic. Winds are expected to turn more
southerly and temperatures will become slightly warmer during the
first half of the workweek. By the second half of the workweek,
expect winds to be more to the east northeast once again.

Although mostly fair weather conditions are forecast, patches of
low level moisture embedded with the trade winds will arrive to
the forecast area from time to time. Thus, passing showers are
expected over portions of eastern PR and USVI during the
mornings. Afternoon convection will lead to scattered showers over
parts of north and northwestern Puerto Rico. This activity is not
expected to lead any significant rainfall accumulations. For the
rest of the islands, expect mostly sunny skies with fair weather
conditions.

&&

.AVIATION...

A cdfnt across the local waters is apchg NW PR and will
stall vcnty PR and the nrn USVI or btwn TIST/TISX. Mstr forming
ahead of the cdfnt will invade waters arnd TISX and mov twd PR thru
30/22Z. This will spread some MVFR conds and mtn obscurations into
USVI and ern PR by 30/18Z. Sfc winds NE incrg to 10-20 kt with gusts
to 26 kt along the north coasts and nrn USVI. Sea breeze influence
along S coast PR til 30/23Z. Overnight winds tonight not expected to
subside as much. Max winds WSW-W 45-60 kt btwn FL380-490.


&&

.MARINE...

A vigorous northerly swell is forecast to continue to invade the
Atlantic waters today, generating hazardous seas up to 12 feet
through early next week. As a result, Small Craft Advisories were
issued for most of the local waters and passages.

Conditions along coastal and surf zone areas will quickly
deteriorate today due to the aforementioned swell event. A High
Risk of Rip Currents is in effect for the north-, east-, and
west- facing beaches of Puerto Rico, including Vieques and
Culebra, and the northern US Virgin Islands. While conditions
deteriorate further today, with breaking waves up to 20 feet,
high surf and coastal flooding can be expected. As a result, a
High Surf and Coastal Flood Warnings will go in effect for
northern Puerto Rico, Culebra, and northern US Virgin Islands.
Please refer to the latest Coastal Hazard Message (CFWSJU), Surf
Zone Forecast (SRFSJU) and Marine Weather Message (MWWSJU) for
detailed information.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 80 74 81 72 / 80 90 80 30
STT 83 74 83 74 / 60 80 60 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
530 AM AST Mon Feb 1 2021

.SYNOPSIS...The shearline that brought copious widespread rain on
Sunday has moved northwest of the area. Only isolated to scattered
showers are expected for the next few days. Winds and seas will
subside during the next several days, but hazardous seas will
persist through at least Tuesday for most of the area and through
the rest of the week for the outer Atlantic waters. High surf and
the high risk of rip currents continue through at least tonight.

&&

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

Showery weather and windy conditions will continue through early
today. A surface high pressure in northeastern Atlantic and a mid-
level ridge will dominate the area thereafter to maintain the trade
wind inversion. This, combined with a drier air mass, will cause
precipitable water values to drop below an inch, according to model
estimates. However, patches of moisture embedded in the trades
cannot be ruled out and are expected to affect the forecast area
from time-to-time. Therefore, relatively stable weather
conditions will begin later today, under the influence of moderate
to fresh east-southeast wind flow. Showers that do develop will
produce light rainfall amounts. Temperatures are expected to be
slightly warmer, reaching the high 80s mainly along the coastal
and urban areas.

.LONG TERM...Thursday through Sunday...
At upper levels a long wave trough will pass through the area on
Thursday, followed by a ridge that will continue to affect the
area through the end of next weekend. At lower levels a moderately
strong high pressure in the northeast central Atlantic ocean will
be joined on Friday by another high pressure in the western
Atlantic that will maintain moderate to fresh tradewinds over the
area. A cold front from the northwest will approach the area
Thursday and fade just northwest of the area on Friday. Winds will
be lightest on Thursday then stronger Friday over the weekend. The
period will mostly be characterized by passing patches of moisture
punctuated by bands of drier air that will bring passing showers
yielding relatively light amounts of rainfall each day.

&&

.AVIATION...Mainly VFR conds expected across the terminals drg the
24 hr period. Drier air moving in will reduce cloud coverage and
limit rainfall activity. Therefore no major wx impacts are expected
to affect operations. The local winds will be generally light
from the ESE tonight, increasing after 01/12Z.

&&

.MARINE...Seas with northerly swell continue between 12-14 feet
at the outer Atlantic waters buoy and around 9-10 feet at the
inner buoy, leaving seas hazardous into Tuesday afternoon for most
of the local waters. Small craft advisory conditions are expected
through Friday in the outer Atlantic waters and are possible
there through the following weekend as well. Seas have subsided
sufficiently to drop the warning but breaking waves of 10 to less
than 18 feet are expected across most of the exposed coasts. And a
high rip current risk goes without saying.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 73 88 73 / 20 20 10 20
STT 83 74 85 75 / 20 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
528 AM AST Tue Feb 2 2021

.SYNOPSIS...Isolated showers in drier air will dominate the
weather pattern today and tomorrow. On Thursday a cold front will
approach the area from the northwest and increase the chances for
light showers. A pattern of passing moisture bands and drier air
will continue into the weekend.

&&

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

As the drier air mass continues to affect the area and the high
pressure ridge maintains influence aloft, limited shower activity
is expected for the forecast area. Precipitable water values are
forecast to be below normal through Wednesday. Overall, fair
weather conditions with sunny skies are forecast for much of the
day, with brief showers over the northwestern coastal areas of
Puerto Rico and downwind from the U.S. Virgin Islands in the
afternoon hours. This activity is due to the combination of
moisture being confined between 1000 to 700 MB with diurnal
heating and sea breeze convergence. Winds will continue from the
southeast at 10-15 mph over land areas. This windflow pattern will
promote somewhat warmer high temperatures, as they will reach the
high 80s mainly along the coasts and urban areas. San Juan may
approach its record high for the date of 88 degrees.

Model guidance suggest another frontal boundary approaching the
forecast area by Wednesday and impacting the islands by Thursday.
This will increase cloud coverage and shower activity for the rest
of the short term period. Precipitable water values are expected to
be near to above normal. Therefore, a more typical seasonal weather
pattern could be expect by the end of the short term period. Showers
will be brief and accompanied by pockets of drier air. Therefore,
light amounts of rainfall are expected.

.LONG TERM...Friday through Monday...
The passage of a long wave upper level trough on Thursday will
usher in higher pressure aloft through Saturday. High pressure
will still dominate Sunday and Monday, but the flow aloft will be
more zonal. The approaching cold front on Thursday will shunt the
moist tropical air entering the southeastern Caribbean to the
west and it will have little impact on the area. However another
trough will enter the area on Saturday night and bring better
moisture behind it at 700 mb. Very patchy moisture at lower
levels, however, will only bring limited shower activity to the
area through the weekend and into early next week. During this
time fluctuations in the precipitable water values are expected to
be greater than one half inch, from less than one inch to a
little more than 1.5 inches, but stability will also be generally
greater. The model is not showing any skill at timing these areas
so only general determinations can be made.

&&

.AVIATION...VFR conditions are expected to prevail across all
terminals drg the 24 pd. Therefore, no significant wx impacts are
expected to affect operations. Also, mostly sunny skies will
cause the local terminals to not have CIGS through most of the
forecast prd. SFC winds will continue ESE at 15-20 kts with higher
gusts thru 22z, winds decrease to 8-12 kt overnight. Maximum winds
WSW-WNW 45-65 knots btwn FL360-480.

&&

.MARINE...Seas are subsiding. Seas at the outer buoy were running
around 8 feet, while seas at the inner buoy were running less than
7 feet. Winds at the outer buoy, however, were exceeding 20
knots from the south southeast. Seas in all waters except those of
the outer Atlantic will be generally below 7 feet by this evening.
Seas in the outer edges of the local outer Atlantic waters may
stay at or above 7 feet so small craft advisories were continued.
Another swell set moves in Wednesday night to prolong the 7 foot
seas into the following weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 73 85 74 / 10 20 30 10
STT 85 75 82 72 / 20 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
455 AM AST Wed Feb 3 2021

.SYNOPSIS...A weak front will stall over the Dominican Republic,
then begin retreating as low level ridging extending over the
area from the northeast blocks its progress. Southeasterly flow
will continue one more day before becoming more easterly. This
will bring above normal temperatures for the northern coast of
Puerto Rico today.

&&

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

A frontal boundary associated with a low pressure system in the far
northwestern Atlantic is located near Hispanola. The latest model
guidance holds the frontal system north of us, not directly
impacting our forecast area. However, low level moisture
associated with this feature will interact with local effects to
enhance shower activity across the islands by Thursday. Winds will
continue from the east southeast and gradually shifting to the
east tonight through the rest of the short term period. Thus, a
typical weather pattern is expected during the next few days with
isolated to scattered showers occurring over parts southeastern
Puerto Rico and U.S. Virgin Islands followed by diurnally induced
afternoon showers over parts of interior and northwestern PR.
Rainfall accumulations are not estimated to be significant, but
ponding of water on roadways at most could be possible with the
most persistent rains.

.LONG TERM...Saturday through Tuesday...
An old frontal boundary will linger northwest of the area until
Saturday with High pressure at the surface in the northeast
Atlantic and at 700 mb from the windward passage to the northeast
Atlantic. This will maintain easterly flow over the area in the
lower levels after Saturday. Moisture at 700 mb remains east of
the area where it fades. The GFS shows an area of moisture forming
to the northeast of Puerto Rico and the U.S. Virgin Islands and
moving across the area on Sunday. Patches continue to form
upstream Monday and Tuesday and move west across the area.
Precipitable water values vary from 0.8 to 1.6 inches during the
period with Sunday bearing the best moisture over the area. Dry
air bands move in tandem with the wettest patches of air. this
will result in scattered showers of uncertain timing moving with
the trade wind flow. Although most of the rain should fall over
the eastern slopes of Puerto Rico, showers in western Puerto Rico
during the afternoons cannot be ruled out. The U.S. Virgin Islands
will see only a few showers during the period with most
accumulations being less than 0.05 inches. At upper levels, the
main trough will have already moved through by Friday, with a
ridge migrating through on Saturday. A second weaker short-wave
trough will pass through on Monday. These are not expected to have
much affect on the moisture over the area which, except for
Sunday, will be confined to the lowest 8000 feet of the atmosphere.

&&

.AVIATION...VFR conditions are expected across all terminals
drg the 24 hr period. Brief MVFR/-SHRA at TNCM bfr 03/14Z. Brief
VCSH possible across TJPS/TIST/TISX, but no major impacts to
operations are anticipated. Winds will continue from the SE
between 10 and 15 knots with some higher gusts. Maximum winds
WSW-W 80-100 kt btwn FL360-440.

&&

.MARINE...Seas have subsided considerably overnight with the outer
buoy reporting slightly less than 6 feet and the inner buoy
reporting less than 4 feet. The buoy at Ponce was just under 4
feet. A new northwesterly swell will enter the forecast area today with
seas rising to 6 to 8 feet in the local outer Atlantic waters
tonight. By Friday seas will be close to 7 feet in the northern
most local waters. Small craft advisories are not expected in the
Caribbean for the remainder of the week.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 73 85 73 / 10 10 40 30
STT 84 75 84 73 / 20 20 30 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
458 AM AST Thu Feb 4 2021

.SYNOPSIS... A weak front will continue to promote pooling of
low-level moisture in a light southeasterly wind flow across the
local area today. An induced surface trough is forecast to move
later today from the east, increasing the potential for scattered
to locally numerous showers over the region. Hazardous seas will
persist for several days. Small Craft and High Surf advisories
and high risk of rip currents are in effect.


&&

SHORT TERM...Today through Saturday...

A deep polar trough over the northwestern Atlantic and associated
front at the surface, will continue to promote pooling of low-level
moisture in a light southeasterly wind flow across the local area
today. An induced surface trough is forecast to move later today
from the east, increasing the potential for scattered to locally
numerous showers over mainland PR and mostly scattered activity
across the USVI. The 500 mb temp is forecast to drop to around -8
degrees C as the upper-level trough moves further east over the
western Atlantic, this should provide unstable conditions aloft to
support locally heavy showers this afternoon over portions of
eastern, north-central and northwestern PR. Urban and small stream
flooding is possible with this activity due to slow moving showers.

An upper-level ridge is forecast to build quickly on Friday from the
west and a hold through the long term period. This will promote
drier air aloft and more stable conditions with 500 mb temps warming
to -4.5 degrees C by early Saturday. Meanwhile, a building ridge at
the surface over the central Atlantic will promote a more east to
northeast trade wind flow. Embedded in this flow, a few shallow
areas of low-level moisture will stream from time to time across the
region, aiding in the development of mostly light showers over the
islands. Therefore, fair weather conditions are expected in general
on Friday and Saturday.

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

The strong surface high pressure northeast of the forecast area will
continue to support a moderate to fresh easterly flow and advect the
remnants of an old frontal boundary into the area on Sunday.
According to model guidance, precipitable water values will be at
or below 1.20 inches mainly confined within 700 mb. Although this
could produce some shower development, a mid level ridge will
maintain a strong subsidence cap causing any shower activity to
develop to be shallow and in short duration. Therefore, expect an
increase in cloudiness on Sunday with isolated showers over U.S.
Virgin Islands and eastern Puerto Rico. Also expect some light
streamers and shallow rainfall over interior and western portions
of Puerto Rico in the afternoon hours with minimal accumulations.

Afterwards, the mid level ridge is expected to remain in place over
the region supporting the easterly trade wind cap for the rest of
the long term period. Max precipitable water content is forecast to
range between 0.9-1.2 inches on Monday. GFS suggests that the best
chance for showers is on Tuesday, with precipitable water values
around 1.40 inches before decreasing again on Wednesday. To
summarize, a typical seasonal weather pattern is expected through
the end of the forecast period but the frequency and intensity of
showers will depend in the timing of pockets of moist air embedded
in the trades streaming across the region. Shower enhancement due
to locally induced effects and sea breeze convergence could
develop over interior and western portions of Puerto Rico during
each afternoon, especially on Tuesday.

&&

.Aviation...Mainly VFR conditions are expected across all terminals
early in the fcst period. However, SHRA will increase gradually
across the USVI/eastern PR terminals during the morning hours and
over the NW quadrant of PR this afternoon. This could cause tempo
MVFR conditions. Winds ESE at 8-12 kt with sea breeze variations at
TJBQ/TJSJ.


&&

.MARINE...

A northwesterly swell is pushing into the regional waters, bringing
hazardous marine conditions. In the offshore Atlantic waters,
hazardous conditions have persisted, and will continue into the
weekend. The nearshore Atlantic waters of Puerto Rico and the
Mona Passage have become hazardous with Small Craft Advisories in
effect.

There remains a high risk of rip currents for north-facing beaches
of Puerto Rico and Culebra, as well as eastern beaches of St.
Croix. and St. Thomas. High Surf Advisories are also in effect
for the northwest to northeast coast of Puerto Rico, including
Rincon, due to the likelihood of large, dangerous breaking waves
of 10 to 12 feet; there is the potential for occasionally higher
breaking waves, especially for beaches of northwestern Puerto
Rico.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 74 85 74 / 40 30 20 20
STT 84 74 84 73 / 40 40 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
436 AM AST Fri Feb 5 2021

SYNOPSIS...

Conditions will improve today as the prefrontal trough continues
moving away from the area. However, lingering showers can be
expected over western Puerto Rico with mostly sunny to partly
cloudy skies and possible isolated shower activity elsewhere.
Generally fair weather is expected for the weekend, with isolated
to locally scattered showers and breezy conditions. Hazardous
marine conditions will persist for the local waters, especially
the offshore Atlantic waters, likely through Monday.

&&

SHORT TERM...Today through Sunday...

Lingering low-level moisture across the region and diurnal effects
will result in afternoon showers mainly over western Puerto Rico.
Elsewhere, mostly sunny to partly cloudy skies are expected with
possible isolated shower activity in diurnal cycle. An upper-level
ridge is forecast to build during the day from the west, and drier
air aloft and more stable conditions are expected to prevail through
the weekend as the ridge continues to build over the region.

A surface high pressure over the central Atlantic will increase the
trade winds and promote breezy conditions during the weekend.
Saturday seems to be the driest day in the forecast period, with
only shallow convection developing over the islands in the
afternoon. However, a weak easterly perturbation in the trades is
forecast to increase shower activity from Saturday evening into
early Sunday. Therefore, scattered shower activity is expected
across the USVI and eastern sections of PR during this period. This
should be short lived, as another drier air mass quickly fills from
the east on Sunday morning. Day time temperatures should remain in
the mid 80s or less across the lower elevations during the weekend.

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

Both GFS and ECMWF continue to forecast an upper ridge over the
forecast area with drier air aloft and a surface high pressure in
central Atlantic dominating the long term period. This will
maintain an easterly trade wind inversion over the region. GFS
suggests that precipitable water values will oscillate between an
inch and inch and a quarter between Monday through Thursday with
variations due to passing patches of moisture embedded in the
trades within the 700 mb level. Hence, expect mainly fair weather
conditions with shallow areas of moisture embedded in the easterly
wind flow reaching the islands from time to time. This will cause
increased cloudiness and light passing showers across PR and the
USVI dependent on moisture availability. Shower enhancement due to
locally induced effects and sea breeze convergence could develop
over interior and western portions of Puerto Rico during each late
afternoon.


&&

.Aviation...Mainly VFR conditions are expected across all terminals
through the forecast period. East winds 10-15 kt with sea breeze
variations and higher gusts after 14z.

&&

.MARINE...

Conditions continue to improve as the influence of the northwesterly
swell subsides across the region. However, hazardous conditions
are forecast to continue for the offshore Atlantic waters, as
increasing winds by Saturday will build seas, replacing the swell
with shorter-period wind seas. These hazardous conditions will
continue to impact that portion of the waters through Monday
morning, at least.


The high risk of rip currents persists at northwestern to
northeastern beaches of Puerto Rico, northern beaches of Culebra,
northwestern beaches of St. Thomas, St. John and adjacent islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 73 84 75 / 20 10 30 50
STT 83 73 84 74 / 30 30 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
456 AM AST Sat Feb 6 2021

.SYNOPSIS...

A trend towards drier conditions, with generally fair weather, will
continue this weekend. A patch of moisture could bring some
additional passing showers tonight into early tomorrow morning,
though. Hazardous marine conditions are expected for portions of the
local waters this weekend. Therefore, small craft advisories and
high risk of rip currents are in effect.

&&

SHORT TERM...Today through Monday...

For today, breezy conditions and quick passing showers are expected
across the U.S. Virgin Islands and the eastern sections of Puerto
Rico. Limited afternoon shower development is possible over western
PR due to local effects, however, no significant rainfall
accumulations are expected. Weather conditions will change this
evening and through Sunday morning due to the arrival of an easterly
perturbation in the trade wind surge. This will bring frequent
showers across the USVI and eastern half of PR, increasing the
potential for urban and small stream flooding. Although a drier air
mass is forecast to move quickly during the day on Sunday, residual
moisture should aid in the development of afternoon showers over
western PR. For Monday, another surge in low-level moisture from the
east is forecast to move by midday across the region. This will
increase trade wind shower activity once again across the
USVI/Eastern half of PR during the morning hours, and as it is
expected to move later in the day, it will provide better moisture
to support afternoon shower activity over mainland PR.

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

No major changes to the long term forecast with models still
suggesting a mid level ridge over the forecast area and a surface
high pressure in central Atlantic dominating the region for most of
the workweek. This will maintain an easterly trade wind inversion
over the area. GFS suggest that precipitable water values will
oscillate between 0.70 inches to 1.44 inches on Tuesday through
Friday with variations due to passing patches of moisture embedded
in the trades within the 700 mb level. The maximum precipitable
water values are forecast for Thursday.

As the mid level ridge continues evolving throughout the week,
500 mb northerly winds will cause cold air advection into the area
cooling down temperatures between -7 to -8 degrees celsius on
Thursday and Friday increasing instability aloft. Therefore,
expect mainly fair weather conditions with shallow areas of
moisture embedded in the easterly wind flow reaching the islands
from time to time. This will cause increased cloudiness and
passing showers across PR and the USVI dependent on moisture
availability. Shower enhancement due to locally induced effects
and sea breeze convergence could develop over interior and western
portions of Puerto Rico during each late afternoon. Expect
somewhat greater shower activity embedded in the trades between
Thursday and Friday due to greater instability aloft. As a result,
ponding of waters on roadways and in poor drainage areas will
remain possible in isolated areas.



&&

.Aviation...Mainly VFR conditions are expected across all terminals
through the forecast period. However, SHRA is expected to increase
from this evening and through early Sunday morning from the east.
This may cause tempo MVFR conditions across the USVI terminals and
TJSJ. East winds increasing around 15 kts with sea breeze variations
and higher gusts after 14z.


&&

.MARINE...

Increasing winds will help to sustain hazardous marine conditions
for the offshore Atlantic waters. For the offshore Caribbean waters,
as well as in and around the local passages, the winds will lead to
the development of hazardous conditions by this evening.
Hazardous condition will last into tomorrow afternoon at least,
and likely into Monday morning for the offshore Atlantic waters
and waters in and around the Anegada Passage.

There remains a high risk of rip currents for most north-facing
beaches of Puerto Rico, as well as beaches of Culebra and
northwestern beaches of St. Thomas.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 85 73 / 40 50 50 10
STT 85 74 84 73 / 50 50 40 30

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
408 AM AST Sun Feb 7 2021

.SYNOPSIS...

A ridge of high pressure will hold over the local area for most of
the workweek. At the low-levels a wind surge is bringing in patches
of moisture from time to time and will continue during the morning
hours with a drying trend afterwards. Hazardous marine conditions
are expected for portions of the local waters today. Therefore,
small craft advisories and high risk of rip currents are in
effect.

&&

SHORT TERM...Today through Tuesday...

Ridge at the surface and at upper-levels will dominate the short
term period. Although, this will promote drier air and stable
conditions aloft, shallow areas of cloudiness with showers will move
from the Tropical Atlantic at times across the region. Breezy
conditions are expected today, with a few trade wind showers moving
early in the morning across portions of the U.S. Virgin Islands and
across the eastern half of Puerto Rico. A drier air mass moving from
the Leewards islands and the Anegada Passage should arrive around
noon across the local area, this air mass and the wind surge should
keep afternoon shower development at a minimum through the afternoon
hours.

For Monday, no significant change from previous forecasts as
another surge in low-level moisture is expected to move from the
east by midday across the region. This will increase trade wind
shower activity once again across the USVI/Eastern half of PR during
the morning hours, and provide better moisture content to support
afternoon shower activity over mainland PR. Similar conditions are
expected on Tuesday, but the trade winds will shift more from the
east to northeast as a surface ridge moves across the western
Atlantic, this will cause showers to focus mainly across the
northeastern sections of PR and northern USVI during the overnight
and early morning hours and over the southwestern quadrant of PR
during the afternoon hours.

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

Model guidance continue to be consistent regarding the mid level
ridge over the forecast area with a surface high pressure in central
Atlantic dominating the region between mid-week and early weekend.
Throughout the forecast period an easterly trade wind cap will
hold over the region. GFS suggests that precipitable water values
will oscillate between 0.8 inches to 1.4 inches with variations
due to passing patches of moisture embedded in the trades confined
between 1000 to 700 mb levels. As the mid level ridge continues
evolving throughout the week, 500 mb northerly winds will cause
cold air advection dropping temperatures between -7 to -8 degrees
on Thursday through Saturday which could increase rainfall
development. One thing to note is that the pockets of dry air in
between will contain precipitable water values at or below 0.9
inches, which is near two standard deviations below normal for
this time of the year.

To summarize, expect mainly fair weather conditions with shallow
areas of moisture embedded in the easterly wind flow reaching the
islands from time to time. This will cause increased cloudiness and
passing showers across PR and the USVI subject to moisture
availability. Shower enhancement due to locally induced effects and
sea breeze convergence could develop over interior and western
portions of Puerto Rico during each late afternoon. For the latter
part of the workweek and Saturday, expect somewhat greater shower
activity due to greater instability aloft when pockets of moisture
embedded in the trades reaches the area. As a result, ponding of
water on roadways and in poor drainage areas will remain possible
in isolated areas.


&&

.Aviation...Mainly VFR conditions are expected to prevail across all
terminals through the forecast period. Winds are expected to
continue from the east at 15-20 kts with higher gusts at times.
Quick passing showers may result in brief areas of MVFR conds across
the USVI/Eastern PR terminals.


&&

.MARINE...Choppy wind driven seas will continue today across most of
the offshore waters and passages. Fresh to locally strong winds will
gradually decrease through tonight. Hazardous seas between 5-7 feet
will continue through this evening across most of the local waters,
except across the offshore Atlantic waters where seas up to 8 feet
may continue through at least Monday afternoon. There is a high risk
of rip currents across the eastern beaches of Culebra and St. Croix,
and a moderate risk across the rest of the islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 73 85 73 / 40 20 30 30
STT 84 72 84 73 / 40 20 30 30

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
447 AM AST Mon Feb 8 2021

.SYNOPSIS...

Generally fair weather will prevail across the region over the next
several days, as a relatively dry air mass sits over the area, along
with stable air aloft. Occasional patches of moisture will pass
through the region, supporting isolated to scattered showers in a
typical pattern. Showers will be relatively quick-moving, carried
along by brisk winds, due to a tight pressure gradient associated
with surface high pressure to the north. Marine conditions have
improved somewhat, and seas of up to 6 feet are expected, with a
moderate risk of rip currents for the majority of local beaches.

&&

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

A mid-level ridge is expected to prevail through the period,
resulting in dry and stable weather conditions aloft. This will
inhibit any potential of organized convective activity across the
local area. Meanwhile, at lower-levels, a surface high pressure
located across the central Atlantic will maintain a brisk easterly
wind flow. Currently, a pocket of dry air is over the area, which
has resulted in dry weather conditions over the local islands during
the overnight period. However, an area of shallow moisture is
expected to move across the USVI during the early to mid-morning
hours and across Puerto Rico during the late morning into the
afternoon hours. As this area of moisture moves across, isolated to
scattered shower activity is possible. Given the strong low-level
flow, any showers will be brief with only minor rainfall
accumulations expected. Another area of drier air is expected to
move across by late this afternoon and last through most of the
overnight hours, resulting in mainly dry weather conditions across
the local islands once again.

Similar weather conditions are expected to prevail for Tuesday and
Wednesday. Another surface high pressure moving into the western
Atlantic will continue to maintain a brisk easterly wind flow and
with it pockets of low-level cloudiness and moisture will be
advected into the area from time to time. This will result in
isolated to scattered shower activity across portions of the local
waters during the overnight and morning hours, with some of the
activity possibly affecting portions of the USVI and eastern Puerto
Rico. Then, some activity may develop mainly over mainland Puerto
Rico during the afternoon hours. Once again, any activity should be
brief with only minor rainfall accumulations expected.

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

Generally dry air persists across the region; as such, generally
fair weather is expected to dominate for much of the long-range
period. Patches of moisture will push across the area from time
to time, helping to develop showers in a typical pattern. Further
contributing to the fair weather is ridging aloft. A deep layer
ridge in the mid-levels will provide stability, suppressing
convective activity and therefore inhibiting development. Some
weakening in this mid-level ridge is forecast for the weekend,
likely late Saturday into Sunday. Meanwhile, a more substantial
patch of moisture is also expected to push into the region
Saturday night into Sunday. An increase in shower activity is
therefore expected for Saturday afternoon into Sunday evening.
Scattered showers are expected in northwestern and interior Puerto
Rico during the afternoon, with a secondary peak possible in
eastern Puerto Rico, downwind of orographic features. Scattered
passing showers are also expected for windward portions of the
local islands during the overnight and morning hours. A return to
generally fair weather is forecast for the start of the work week
next week, likely lasting into at least midweek.

&&

.AVIATION...

Mainly VFR conditions expected through the period. Some passing
SHRA are possible across the USVI and eastern PR terminals between
08/12Z and 08/18Z, resulting in VCSH. However, no impacts to
operations are expected at this time. Winds will be from the E at
less than 10 kts through 08/12z, increasing to around 15 kts with
higher gusts and sea breeze variations after 08/14z.

&&

.MARINE...

Conditions have improved across the local waters, and hazardous seas
are not expected for today. Buoy data supports this assessment, with
the offshore buoy, 40143, showing seas of less than 7 feet since
2Z/10 PM AST last night, and the San Juan buoy showing seas of
around 3.5 to 4 feet. However, a tight pressure gradient, associated
with a surface ridge to the north, is bringing stronger than normal
winds to the region, which will maintain choppy seas of up to around
6 feet, especially for the offshore waters in both the Atlantic and
Caribbean, as well as the local passages.

For the beachgoers, there is a moderate risk of rip currents for the
majority of the local beaches; the main exceptions being western
Puerto Rico and south central Puerto Rico.

&&

.FIRE WEATHER...

Despite the patch of moisture approaching the region, dry air will
persist into midday, at least, for the southern coastal plains of
Puerto Rico. Additionally, the KBDI for Camp Santiago is 629, with
the 10 hour fuel moisture being 7.18%. Though relative humidity
values may not fall below critical thresholds today, it is likely
that the 10 hour fuel moisture will remain below the critical
fire weather threshold of 8%. Furthermore, winds will remain
brisk across the region, around 15 to 20 mph, with stronger gusts
likely. As such, a Red Flag Warning has been issued for the
southern coastal plains of Puerto Rico for today.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 74 83 74 84 / 20 30 30 40
STT 74 84 73 84 / 20 30 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
437 AM AST Tue Feb 9 2021

.SYNOPSIS...

Generally fair weather will persist over the next several days,
under the influence of a drier than normal airmass and stability
aloft from mid- to upper-level ridging. Patches of moisture will
help to develop showers in a typical pattern, with passing showers
overnight and into the morning in eastern Puerto Rico and the USVI,
and afternoon showers in western and interior Puerto Rico.
Significant rainfall is not anticipated, especially as showers
will likely be quick-moving, whisked away by the brisk winds
across the region.

&&

.SHORT TERM...Tuesday through Thursday...

A mid to upper-level ridge will promote stable weather conditions,
with subsidence and dry air at those levels. While at low-levels,
trade-wind perturbations will bring patches of moisture, which
enhanced by local effects will result in passing showers across the
eastern half of Puerto Rico, the U.S. Virgin Islands, and
surrounding waters each day. By afternoon, the rain activity will
spread into the western sections of Puerto Rico.

That said, expect stable weather conditions with just the advection
of pocket of moisture from time to time, producing isolated to
scattered showers across the windward sections, followed by limited
afternoon convection over the western portions. This activity will
not represent any hazard that could put at risk the life and
property of the residents of Puerto Rico and the U.S. Virgin
Islands.

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

A pattern of dry air with below average precipitable water values
punctuated by patches of moisture streaming across the region from
time to time is expected into at least midweek next week. These
patches of moisture are forecast to bring near-normal levels of
moisture to the region, which will help to support a typical
weather pattern across the area. A mid- to upper-level ridge is
forecast to be just north of the region through most of the
period, providing stability aloft, and inhibiting shower
development; organized convection is unlikely. Brief weakness in
the mid-level ridge is forecast for the weekend, decreasing
somewhat the stability over the area. Meanwhile, on Saturday night
into Sunday, a substantial patch of moisture, likely enhanced by
moisture being pulled up from the south in a weak surface
disturbance, will push across the region. Near-normal precipitable
water values are likely, and above normal values are possible. An
increase in shower activity is expected during that time period
because of this combination of factors. Even so, there will remain
sufficient stability aloft such that organized convection is
unlikely. On the whole, generally fair weather, with isolated to
locally scattered showers, is expected for the duration of the
long-term period. Confidence in the forecasted weather pattern is
high.

&&

.AVIATION...

VFR conditions will prevail thru the forecast period. The E-NE winds
will push clouds and ISOL-SCT rain (at times) in the VCTY of
IST/JSJ/ISX/NCM/KPK. Then, clouds and showers will develop over the
interior/W-PR between 09/16z-23z. Winds will continue calm to light
and variable, augmenting around 15-20 kt with higher gusts and sea
breeze influence after 09/13z.

&&

.MARINE...

Moderate to fresh winds continue across the local waters over the
next several days, under the influence of a tight pressure gradient
caused by a surface high to the north of the region. This will
maintain choppy marine conditions across much of the local waters,
especially the offshore waters and local passages. Later in the
week, there is the potential for hazardous conditions to develop in
response to the extended duration of stronger-than-normal winds, and
further increases to winds are possible, as well.

For the beachgoers, there is a moderate risk of rip currents for the
majority of local beaches. Beaches sheltered from the east, such as
those of western and south central Puerto Rico, have a low risk of
rip currents.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 74 84 73 / 30 40 40 30
STT 84 74 84 72 / 30 40 40 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
418 AM AST Wed Feb 10 2021

.SYNOPSIS...

Generally fair weather is expected to persist for at least the
next week, under the influence of a dry airmass and stability
aloft. Patches of moisture will stream across the region from time
to time, supporting isolated to scattered showers in a typical
pattern. Significant rainfall amounts are not presently
anticipated.

&&

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

Satellite imagery shows an area of clouds that are moving in,
associated with a trade wind perturbation. This perturbation will
increase moisture and the potential for shallow rain activity across
the islands throughout the day. Meanwhile, a mid to upper-level
ridge will limit vertical development by promoting subsidence and
dry air at those levels. Once again, rain activity will spread into
the western sections of Puerto Rico by late this morning into the
afternoon hours. Therefore, expect no threat of flooding.

Stable weather conditions will persist through the rest of the short
term. However, the advection of low-level moisture will produce
isolated to scattered showers across the windward sections overnight
and during the morning, followed by limited afternoon convection
over the western portions each day.

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

There hasn`t been much in the way of change to the expected overall
pattern for the weekend through next week. Generally fair weather is
expected, with a drier than normal air mass in place over the
region. Aloft, a mid- to upper-level ridge will provide stability,
inhibiting convective development. Various patches of moisture will
bring moisture to near-normal levels from time to time during the
period, and will support shower activity across the local islands,
in a typical pattern.

The mid- to upper-level ridge is forecast to weaken its hold over
the area slightly for Saturday into Sunday, with a weak trough
developing, pushing into the area, and then dissipating. This, along
with a somewhat large patch of moisture that will be in the general
vicinity, could lead to an increase in shower activity. However,
model guidance on the timing of any potential moisture has changed
somewhat, quickening its arrival. The area of maximum impact of the
combination of these features will depend on timing. The most likely
timing is between late on Saturday night and midday on Sunday.
Otherwise, the only other day during this period that looks a little
bit more favorable for rain is Wednesday. Significant rainfall
amounts are unlikely, especially given that brisk winds will also
persist for much of the next week.

&&

.AVIATION...

VFR conditions will prevail thru the forecast period. The E-NE winds
will push clouds and ISOL-SCT rain (at times) in the VCTY of
IST/JSJ/ISX/NCM/KPK. SCT-BKN between FL020-FL050 is possible at
times. Then, clouds and showers will develop over the interior/W-PR
between 10/16z-23z. Winds will continue at less than 10 kt thru
10/13z, increasing at 15 to 20 kt with higher gusts and sea breeze
influence after that.

&&

.MARINE...

The surface ridge to the north is maintaining a tighter than normal
pressure gradient across the region, leading to the persisting
moderate to fresh easterly winds. These winds are, in turn, fueling
the building seas for the local waters, with choppy conditions
across much of the region. For the offshore Atlantic waters,
hazardous conditions are forecast to develop by as soon as late
tonight. For now, this is the only Small Craft Advisory in effect,
as the development of hazardous conditions is expected to take more
time in other portions of the local waters. The most likely timeline
has hazardous conditions spreading beyond the offshore Atlantic
waters late tomorrow night or early Friday morning; affected areas
will include the offshore Caribbean waters and the local passages.
Considering how stable the weather pattern has been and is forecast
to remain, there is the potential that these conditions could
persist through the weekend and into the next workweek.

For the beachgoers, there remains the moderate threat of rip
currents for most local beaches. Some beaches of south central and
western Puerto Rico have a low risk. At beaches not sheltered to the
east, though, the moderate (or potentially higher later this week)
risk will be sticking around for a while.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 73 83 72 / 40 40 40 50
STT 84 72 83 73 / 40 30 40 50