Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
503 AM AST Wed Dec 18 2019

.SYNOPSIS...

East to southeast wind flow will continue through Thursday. A
surface ridge of high pressure will strengthen over the region
during the evening on Friday, and increase the trade wind cap
through the weekend. Also, the ridge will pull in a drier air mass
from the eastern Atlantic; the drier air and trade wind cap will
create relatively tranquil weather with a few showers. Early next
week moisture and rain chances are forecast to increase as a
frontal boundary moves near Puerto Rico on Wednesday or Thursday.

&&

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

A broad surface high pressure, located over the North Atlantic
Ocean, will promote breezy conditions, especially across the local
waters and coastal areas. Satellite images identify an area of dry
air over and approaching the islands. Therefore, sunny skies with
passing clouds will dominate today`s weather. However, trade wind
showers cannot be ruled out across the local waters, the U.S. Virgin
Islands and south and east Puerto Rico. Isolated afternoon
convection will remain possible across the northwest quadrant of
mainland Puerto Rico. Under a southerly wind flow, above normal
maximum temperatures will continue across St Croix, and northern
Puerto Rico this afternoon.

A cold front moving across the Eastern Seaboard will move into the
Western Atlantic Ocean Thursday, sinking well north of the islands
by Friday. The pressure gradient is expected to relax and winds will
return from the east by Thursday evening. A somewhat drier air mass
will persist through the short term period. However, passing showers
should not be ruled out each day.

&&

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

Ridging at the mid to upper-levels of the atmosphere will hold firm
through the weekend, and bring relatively fair weather. However,
locally and diurnally induce showers are forecast to develop during
the afternoons. Also, the surface and mid-level ridge will usher in
a relatively drier air mass as well as strengthen the trade wind cap
over the U.S. Virgin Islands and Puerto Rico. The 00Z GFS shows
precipitable water values decreasing throughout the day on Saturday,
before falling to .98 inches late Sunday night. The adverse effects
above will inhibit the development of frequent showers during the
weekend.

After the weekend the forecast becomes convoluted due to the
uncertainty in the synoptic setup over the Eastern U.S. and the
Atlantic waters. On Monday a low begins to develop across the
Maritimes, this low is forecast to continued to deepen through
Tuesday near the Bay of Fundy/northern mainland Nova Scotia. Both
the GFS and ECMWF show this solution. As the low deepens a
shortwave trough is forecast to develop over the eastern Atlantic
waters, and continue to move to northeast of the area, however, the
trough will bring a frontal boundary through Puerto Rico either late
Wednesday or early Thursday. As the trough impinges on the surface
ridge; the ridge will slide to the east, which will turn the winds
to a southerly direction and usher in moisture from the southern
Caribbean waters.

Tuesday and Wednesday, are where the GFS and GFS diverge on the
timing of the frontal passage and how deep the shortwave trough
becomes. Nevertheless, both models show the front moving through
Puerto Rico sometime during the middle of the week. The proximity of
the trough and a moist southerly wind flow will increase rain
chances during the middle of the week. This increase in moisture is
depicted by the GFS cross-section, which shows a plethora of
moisture through the entire atmospheric column late Wednesday
through Thursday. Also, precipitable water values will range from
1.8 to 2.1 inches on Tuesday and Wednesday.

Thursday, guidance shows ridging at the surface and aloft over the
area, as the ridges continue to build an easterly wind flow will
resume and pull in a drier air mass over the area.

&&

.AVIATION...

ESE to SE winds at 10 to 15 knots with occasional gusty
winds will persist through the fcst period. VFR conditions expected,
although showers will move at times across the terminals of USVI,
E/S-PR and TNCM/TKPK throughout the day, developing over NW-PR
between 18/18z-20z.

&&

.MARINE...

A surface high pressure across the Atlantic is creating hazardous
seas across the local waters. Seas up to 8 feet are expected
across most of the local waters, seas could occasionally reach 10
or 11 feet today. Winds will be from the east southeast at 15 to
20 kts with higher gusts. A high risk of rip currents for the northern,
eastern, and southeastern beaches of Puerto Rico. Also, there is
a high risk of rip currents for the beaches of Saint Croix, the
eastern and southern coast of Vieques, and the northern beaches
of Culebra.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 75 87 75 / 20 30 30 30
STT 85 75 86 75 / 10 20 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
509 AM AST Thu Dec 19 2019

.SYNOPSIS...
A relative dry air mass combined with a mid- to upper-level ridge
will promote stable weather conditions across the islands through
at least next week. However, the advection of pockets of moisture
will result in trade wind showers from time to time. An upper-
level trough and a frontal boundary is forecast to deteriorate
weather conditions the first half of next week.

&&

.SHORT TERM...Thursday through Saturday...
The short-term period will see relatively tranquil weather with a
few passing showers, mainly during the afternoon. This weather is a
result of a staunch ridge of high pressure centered across the
central Atlantic waters.

A drier air mass filtered over the area yesterday, and is
currently in place. The ridge will continue to draw in a
relatively drier air mass as well as strengthen the trade wind cap
over the U.S. Virgin Islands and Puerto Rico through Friday. The
TJSJ 19/00Z sounding showed a large inversion ion between 700 to
500 mb, with modest moisture today and Friday. The strong
inversion will limit the development of wide spread showers across
the region. However, small patches of moisture will work into the
area from time to time causing a few isolated showers to develop.
If they develop, will be short-lived as a result of sinking air
provided by the ridge.

Saturday, another round of drier air is forecast to work into the
region from the east; this will cause precipitable water values to
fall, and limit shower development. By Saturday, afternoon a frontal
boundary across the western Atlantic will press against the ridge
positioned across the Atlantic waters. The trough will cause the
ridge to relocated to the northeast of Puerto Rico and allow east to
southeast wind flow. The east southeast wind flow will pull moisture
from the Caribbean across the U.S. Virgin Islands and Puerto. The
return in moisture will cause precipitable water values to rebound
quickly during the late afternoon. Therefore, expected an increase
in showers during the afternoon and evening.

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

Ridging at the mid- to upper-levels of the atmosphere will hold
firm through at least Monday, resulting in relatively stable
weather conditions. However, the typical trade wind showers will
continue to move at times across the local waters and windward
sections each day.

Model guidance is suggesting a change in the weather pattern by
Christmas Eve with the arrival of an mid- to upper-level low and
a frontal boundary. The guidance had shown inconsistency
associated with the timing and location of these features.
However, if this unstable and wet pattern holds, showers and
thunderstorms would be observed during the Eve and the Day of
Christmas.

A ridge pattern and the typical easterly winds are forecast to
return across the Northeast Caribbean as the TUTT-Low moves into
the Central Atlantic Thursday and Friday.

&&

.AVIATION...
Mainly VFR conditions expected across all terminals
over the next 24hr. However, a few VCSH may develop across USVI and
eastern PR terminals sites by 19/15Z. Similar a few VCSH may affect
TJMZ and TJBQ between 19/16-22Z. Sfc winds from east southeast at 15
to 20 kts with higher gusts possible. Max winds bcmg by 19/12Z NW
40-55 kt btwn FL380-460.

&&

.MARINE...

Winds are forecast to slowly diminish today, therefore marine
conditions although hazardous are expected to improve. A Small
Craft Advisory still in effect for the Atlantic Offshore Waters
throught this evening, and for the Caribbean Offshore Waters and
the Mona Passage through 8 a.m. this morning. Elsewhere small
craft operators are urge to exercise caution due to seas up to 6
feet. The winds will be from the east to east southeast at 10 to
15 kt, but in some locations could reach up to 20 knots. Marine
conditions will continue to improve through at least Saturday,
when seas are forecast to increase Saturday and Sunday.

For the beach goers, the risk of rip currents is now moderate for
most of the local beaches, except across the western coastal areas
of the islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 75 86 73 / 30 30 30 20
STT 85 76 85 73 / 40 40 30 20

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
508 AM AST Fri Dec 20 2019

.SYNOPSIS... Surface high pressure across the eastern Atlantic and
another surface high pressure entering the western Atlantic will
keep a moderate easterly wind flow through the weekend. Below
normal moisture expected today, but a surge of moisture with a
short wave trough is expected on Saturday, causing an increase in
shower activity. Frontal boundary expected to approach and remain
north of the local area on Tuesday and Wednesday, bringing
another increase in moisture and shower activity. Choppy seas
expected for the next several days, northerly swell will cause
hazardous seas starting on Saturday.


&&

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

Fair weather is expected to prevail with a few isolated showers
this morning across eastern Puerto as well as The U.S. Virgin
Islands; and a few showers over portions of western and interior
areas of Puerto Rico this afternoon. A prominent surface ridge is
promoting the above conditions, by towing in a drier air mass from
the eastern Atlantic as well as strengthening the trade winds
across the region. However, patches of moisture are forecast to
move underneath the ridge and pool over the U.S. Virgin Islands
and Puerto Rico. A patch of moisture is currently 290 miles east
of the U.S. Virgin Islands, and should arrive near the eastern
areas of Puerto Rico in the next 5 hours or by 10:30Z.

Saturday, recent guidance shows a plethora of moisture moving into
the area from the east. The increase in low-level moisture is a
result of the short-wave trough that will displace the ridge to our
northeast, and turn surface winds to the east southeast direction
across the Caribbean, and east northeast over and north of Puerto
Rico. The GFS has precipitable water values ranging from 1.7 to 1.8
inches by Saturday afternoon. Analysis of GFS cross-section for TJSJ
has the moisture confined to the 1000 to 700 mb, with modest
moisture showing from 500 to 200 mb. Although, the atmospheric
column is not significantly moist throughout, we still can expect
frequent passing showers on Saturday for the U.S Virgin Islands and
Puerto Rico. Numerous showers where put into the forecast for
Saturday as a result of the plume of moisture, which will cause
frequent showers on Saturday. Also, something to keep an eye on is
if the short-wave digs further south than what current guidance
shows; this will increase instability as well as increase rain
chances on Saturday and pop will need to be readdressed.

Sunday, the short-wave is expected to lift to the northeast, which
will turn the winds in an easterly direction. The east northeast
winds will advect a drier air mass over the U.S. Virgin Island and
Puerto Rico throughout the day. The GFS shows precipitable water
falling to 1.0 inches by Sunday evening. Additionally, the drier air
will erode the lingering moisture left over the area. Nevertheless,
a few isolated to scattered showers can`t be ruled out during the
afternoon.

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

The following workweek will begin with below normal moisture
across the local area with winds gradually shifting to a
southeasterly direction. The winds will be southerly by Wednesday
and Thursday. This is due to a surface low pressure that is
expected to develop across the western Atlantic, then move east
and pass north of the local area, causing winds to become
southerly and also lighter. This SFC low will have a frontal
boundary which is expected to remain just north of the local
islands, but will cause an increase in moisture, cloudiness and
rainfall on Tuesday and Wednesday. The jury is still out on just
how strong this frontal boundary will be since the models have
been inconsistent over the past few days, but it appears as though
there will be at least an increase in shower activity across the
local area as well as an increase in cloud cover. That said, the
latest GFS model is forecasting a strong upper trough approaching
the local area late Tuesday into Wednesday, which could be a
factor in developing thunderstorms across the local area, for that
reason we added isolated thunderstorms to the forecast on Tuesday
and through Wednesday. The moisture will linger for the rest of
the workweek but the upper trough will weaken and move east, so
scattered showers are still expected, but thunderstorms are not in
the forecast after late Wednesday night.


&&

.AVIATION...VFR conds will prevail through 20/02Z. VCSH are
possible across terminal sites TIST and TISX through 19/12Z. A few
ISO/SCT SHRA are possible across terminals TJBQ, TJMZ and TJSJ by
19/18Z with showers diminishing by 20/00Z. SFC wnds fm E-SE 15-20
kts. Max winds WNW 40 to 50 kts ABV FL350.


&&

.MARINE...Seas are now up to 6 feet, and are expected to remain up
to 6 feet until early Saturday. The winds will be from the east at
10-15 knots with occasional gusts. However, a small craft advisory
will go into effect at 8 AM AST Saturday because a northerly swell
will cause seas to increase up to 7 feet, starting with the
offshore Atlantic waters, then invading the local passages
starting Saturday night. There is a low to moderate risk of rip
currents today, but a high risk of rip currents is expected on
Saturday across the northern beaches of Puerto Rico.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 74 83 73 / 30 60 60 20
STT 85 73 85 74 / 30 60 60 30

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
547 AM AST Sun Dec 22 2019

SYNOPSIS...An improvement in the overall weather conditions is
expected through the beginning of the upcoming workweek as drier
air continues to move into the region. Winds will be shifting
to a more southerly direction by mid-week. Moisture will increase
once again by Christmas Day and, therefore, an increase in shower
activity is expected together with isolated thunderstorms in the
afternoon hours. Across the local waters, a northerly swell will
continue to generate hazardous marine conditions, possibly through
Tuesday.

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

Overall, the weather is improving as drier air is moving in.
Scattered showers still linger across the local waters, some of
which are reaching the eastern sections of Puerto Rico, leaving
minimal accumulations. These showers are expected to dissipate or
move away by the late afternoon hours. However, locally induced
showers are expected to develop across the western interior and
western sections of Puerto Rico this afternoon. The rainfall
accumulations could surpass 1 inch in some areas, causing at least
ponding of water on roadways and poor drainage areas, but minor
urban flooding will not be ruled out. After today, even drier air is
expected to move in, as the local winds start to have more of a
southeasterly direction. In fact, the latest guidance solutions
suggests very little to no rainfall across most of the forecast
area. For that reason the forecast is mainly for isolated and brief
showers that would cause little to no rain accumulations on Monday
and most of Tuesday. By late Tuesday, an approaching frontal boundary
could cause an increase in clouds and shower activity to the local
waters. There is also a slight chance of thunderstorms across the
local waters late on Tuesday as an upper low will be approaching and
increasing instability across the area.

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

According to the latest GFS model run, Christmas Day seems to be
the wettest of the long-term period. Mid to upper level dynamics
and potential temperature at 500 mb suggest a good change for
isolated thunderstorms mainly across the Atlantic waters and
northern portions of Puerto Rico. Advective showers embedded in
the southerly wind flow can not be ruled out elsewhere. The
moisture will hold through the rest of the of the long-term period
due to the presence of what will then be remnants of the frontal
boundary. However the GFS indicates that the moisture will not be
significant enough in the mid and upper levels to generate any
isolated thunderstorms in the area after Wednesday. By late
Friday, model guidance suggests a shift of wind direction and will
be more from the east through the end of the long term period.
Hence, a more seasonal weather pattern is possible for the
upcoming weekend.


&&

.AVIATION...Prevailing VFR at all terminals with VCSH in the morning
hours at the USVI terminals as well as TJSJ and TJPS. SHRA
development across western PR could cause TEMPO MVFR conds at TJMZ
after 22/17Z. Easterly winds up to 10KT through 22/13Z, increasing
to about 15KT and occasional gusts thereafter.


&&

.MARINE...A northerly swell continues to affect the local Atlantic
waters and passages. Winds at 10-15 knots will contribute to rough
seas at 5 to 8 feet with occasionally seas up to 10 feet.
Therefore, small craft advisories are in effect for the Atlantic
waters and local passages at least until Tuesday. The high risk of
rip currents continue across the northern and western beaches of
Puerto Rico, Culebra and the USVI through at least Tuesday
afternoon.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 73 87 72 / 40 30 30 20
STT 84 73 84 74 / 20 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
549 AM AST Mon Dec 23 2019

.SYNOPSIS...Drier air is moving in and fair weather is expected
today and most of Tuesday. A frontal boundary is expected to
approach the local area by Wednesday into Thursday causing an
increase in clouds and shower activity. Upper low approaching will
cause an increase in instability and may enhance convection ahead
of the frontal boundary on Wednesday and Thursday, causing a few
thunderstorms over the local waters. Winds will be easterly today,
but will gradually become east southeast and southeast starting
late today, continuing through the rest of the week.

&&

.SHORT TERM...Today through Wednesday

Dry conditions with easterly winds generally between 5 to 15 mph
will prevail through this evening, becoming southeasterly on
Tuesday. Isolated to scattered showers could be expected today
over eastern portions of PR and USVI with the highest activity
over the local waters, mainly during the afternoon hours. However,
the expected rainfall amounts are not expected to be significant.
By late Tuesday night, an increase in moisture at all levels is
expected over the region due to an approaching frontal boundary
and upper-level trough. This surge in moisture, together with a
change in wind direction more to the southeast will provide enough
instability to produce some convection in the area. Hence, this
weather scenario could produce shower activity and isolated
thunderstorms, mainly across the local Atlantic waters by
Wednesday afternoon.

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

By Thursday the frontal boundary is expected to be weakening as it
approaches the local area. The upper low north of the local area
would also be weakening as it continues to move east, flattening
out by late Thursday, which would lower the chances of
thunderstorms late Thursday and through the rest of the week. The
wind flow will be from the south southeast and the available
moisture will be higher than normal. This setup will allow for
scattered to locally numerous shower across the local area,
especially across the local Atlantic waters which is where the
global models put the enhanced convection associated with the
frontal boundary. Given that this front should be weakening by
then, and the models have been inconsistent in showing the same
area of enhanced convection from model run to model run, the
confidence is a bit on the low side. That said, the one thing that
has been consistent is that the frontal boundary will get very
close to Puerto Rico and moisture will increase significantly,
which would cause an increase in shower activity across the local
area, although more for PR than the USVI. After Thursday, the
deeper moisture is expected to linger over the area, but ridging
will develop in the mid and upper levels. For that reason, mainly
scattered passing showers are to be expected for the rest of the
week, with the possibility of enhanced convection across the areas
of sea breeze convergence over PR in the afternoon hours, while
the USVI would continue to have brief isolated to scattered
showers.

&&

.AVIATION...Mainly VFR conditions at all terminals are expected
during the next 24 hours. Fair weather will prevail across the local
area for the rest of the forecast period. Surface winds will be from
the east at 10-15 kts with occasional higher gusts in the afternoon
hours.


&&

.MARINE...The local seas are improving slightly, bu the northerly
swell will continue to affect the local waters today and possibly
on Tuesday. The buoy 41043 north of PR is still showing wave
heights of 7 to 8 feet, with a wave direction from the north,
therefore the offshore Atlantic waters are still expected to have
seas of around 7 feet. However, the Rincon and San Juan buoys are
both reporting seas of under 7 feet and for that reason the small
craft advisory may be allowed to expire at 8 AM for the nearshore
Atlantic waters. That said, the local passages will still be
observing seas of over 7 feet today into Tuesday. There is also a
high risk of rip currents for many of the local beaches,
especially northern PR, Culebra and Saint Thomas.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 73 90 74 / 30 20 20 30
STT 84 75 84 77 / 20 20 20 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
517 AM AST Tue Dec 24 2019

.SYNOPSIS...Surface low pressure and associated frontal boundary
continues to move east, approaching the local area by midweek. As
the surface low approaches, the wind flow will become south to
southeasterly, causing an increase in moisture starting late
today. The frontal boundary will approach and convection
associated with it will affect the local islands from Wednesday to
Thursday. An approaching upper low will cause an increase in
instability and may cause some thunderstorm development over
portions of the forecast area on Wednesday and Thursday. Latest
guidance suggests a significant increase in shower activity on
Thursday over the islands.

&&

.SHORT TERM...Today through Thursday

Mainly fair weather conditions with southeasterly winds generally
between 5 to 15 mph today, becoming more southerly on Wednesday.
Diurnally induced afternoon showers will be limited and mostly
isolated. This activity will be focused mainly over the
northwestern quadrant of PR and across the local waters. However,
rainfall amounts are not expected to be significant. A gradual
surge in moisture at all levels is forecast to start on Wednesday
over the region due to a vigorous upper level trough and
a frontal boundary that will approach the area. These features
will promote instability that, combined with the moisture, will
result in enhanced convection for the area on Wednesday and
Thursday. Latest model guidance suggest Thursday to be the
wettest day for the short-term period. The models seem to be
having a tough time solving this frontal boundary once it reaches
the local area, and each model run seems to be different than the
one before, but it is evident that it is likely to have a
significant increase in shower activity for Wednesday into
Thursday with at least isolated thunderstorms over the local area.

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

By Friday, the upper trough is expected to have weakened and
flattened, but another upper trough could develop to the east of
the local area late in the weekend into the following week.
Therefore the instability is expected to decrease on Friday and
then increase again in the weekend, but mostly across the eastern
sections of the forecast area and the Caribbean waters. For the
long term period, the higher than normal moisture is expected to
linger into the weekend, then a break in the moisture on Monday
and Tuesday, but late Tuesday into Wednesday the moisture could
increase once again. What the current guidance suggests would
mean that there could be widely scattered showers across much of
the local area, but the chances of thunderstorms or significant
rainfall amounts seem to be small. Also, the global models have
been less than stellar the past few days, showing great changes
from day to day, and therefore the confidence in the long range
forecast is low.

&&

.AVIATION...Mainly VFR conditions across all terminals during the
next 24 hours. However, expect few clouds layers from FL025 to
FL050. Approaching frontal boundary will promote westerly winds in
the afternoon at TJMZ/TJBQ. For the rest of the terminals, light
easterly winds are expected for the forecast period with sea
breeze variations at TJPS after 24/13Z.

&&

.MARINE...The latest guidance seem to be underestimating the wave
heights by about a half a foot to a foot when compared to the
observations. However, small adjustments were made to account for
the latest buoy observations. The winds across the local waters
will be between 10-15 knots from the south to southeast today with
seas up to 6 feet across most of the local waters. That said, a
fading northerly swell is still causing hazardous seas across the
offshore Atlantic waters, where seas up to 7 feet are expected.
Therefore a small craft advisory continues in effect for today
across the offshore Atlantic waters. There is also a high risk of
rip currents across the north beaches of PR, Culebra and
northwestern St Thomas.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 74 90 76 / 20 30 20 20
STT 83 79 83 78 / 20 40 40 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
511 AM AST Wed Dec 25 2019

.SYNOPSIS...Surface low is moving east and will be north of the
local islands by tonight. This surface low and its associated
frontal boundary will cause the local winds to be from the south
today, and potentially cause near record high temperatures across
the north coastal municipalities. An approaching upper level low,
will also approach the local area tonight and Thursday, which
will increase instability over the area, combined with the frontal
boundary and the increase in moisture, will bring an increase in
shower and thunderstorm activity tonight and Thursday. Moisture
will linger into the weekend, causing scattered showers across the
local area, but instability decreases so thunderstorm potential
decreases after Thursday. Seas are improving but another northerly
swell is expected late Friday into the weekend, causing hazardous
seas once again.

&&

.SHORT TERM...Today through Friday

Winds from the south will will cause above normal temperatures
across the northern coastal areas. Near record to record breaking
high temperatures as well as heat index ranging from 98 to 102
degrees are possible today. Advective showers embedded in this
southerly wind flow are expected to continue at least until the late
morning hours. Diurnally induced afternoon showers can not be
ruled out but are not expected to leave significant rainfall
amounts. The surface low and its associated frontal boundary is
approaching and could cause an increase in shower and thunderstorm
activity across Puerto Rico tonight. The thunderstorm potential is
enhanced by increasing instability as an upper low approaches the local
area. Latest model guidance suggest Thursday as the wettest day
of the forecast period since it shows strong divergence aloft and
temperature at 500 mb of about -6 Celsius. This also results in a
good chances for thunderstorms over the area local area, both over
the waters and land areas. Remnants of the frontal boundary will
leave enough moisture over the area on Friday. Therefore showers
will continue over the islands for the rest of the short term
period.

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

By Saturday, an upper ridge will start developing just west of the
local area, with an upper trough developing late in the weekend,
strengthening in the following workweek east of the Leewards.
Therefore the instability is expected to decrease this weekend.
However, higher than normal moisture is expected to linger this
weekend, especially for Sunday, when a SFC high pressure moves to
the north of the local area, bringing a boundary with higher
moisture and shower activity. An increase in winds from the ENE is
expected as well. A break in the higher than normal moisture is
then forecast on Monday and Tuesday, but late Tuesday into
Wednesday the moisture could increase once again. What the current
guidance suggests would mean that there could be widely scattered
showers across much of the local area, especially on Sunday, then
Wednesday and Thursday, but the chances of thunderstorms or
significant rainfall amounts seem to be small. Also, the global
models have been questionable for the past few days, although
there was a bit more consistency from yesterday to today, that
said, the confidence in the long range forecast is low.


&&

.AVIATION...VFR conditions will continue to prevail at all TAF sites
through the forecast period. Southerly winds to continue at 10 to
15 knots with higher gusts. Conditions are expected to
deteriorate late Wednesday as a frontal boundary approaches the
forecast area from the west. A westerly wind component is expected
at TJMZ/TJBQ after 25/13z.


&&

.MARINE...Local seas are choppy and are expected to be up to 6
feet across the offshore waters and local passages with winds
increasing up to 20 knots from the south. Therefore, small craft
operators are urged to exercise caution. The choppy seas will
continue for the rest of the week, but by late Friday and this
weekend, a northerly swell could cause hazardous seas. An increase
in wind speed is also expected this weekend. As far as rip
currents, there is a high risk of rip currents for the
northwestern to northeastern beaches of Puerto Rico, Culebra, and
for Cramer Park in Saint Croix through late tonight.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 91 76 85 75 / 20 30 80 60
STT 83 78 85 74 / 20 10 60 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
451 AM AST Thu Dec 26 2019

.SYNOPSIS...
A frontal boundary with scattered showers and isolated
thunderstorms located over the west of Aguadilla will continue
moving through the area. The weather conditions are expected to
deteriorate early in the morning across the northern sections of
Puerto Rico and continue al least until evening hours. The chance
of potential for urban and small stream flooding will continue to
increase as well ponding of water on roadways and in poor drainage
areas.

&&

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

The vigorous upper level low and associated trough will continue
to move east southeast and pass just north of the forecast area
today through early Friday. This feature will provide good
ventilation and instability aloft as it crosses the region. In the
low levels, increasing moisture along the associated frontal
boundary sinking southwards across the region, and an induced
surface trough crossing the area will help to promote a very moist
and unstable environment today through at least early Friday. The
overall low level pattern will favor a moist southerly winds flow
with increased moisture convergence and pooling across the
forecast area. This along with latest model guidance, recent
satellite imagery and radar products all suggest high potential
for increased convection and for shower and thunderstorm
development across the region. That said expected enhanced showers
and isolated thunderstorm development across much of the islands
and regional waters today, with good potential for urban and small
stream flooding as well as ponding of water on roadways and in
poor drainage areas.


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

By Sunday, a high pressure at mid and upper levels will bring much
drier air and northerly winds into the area. This high pressure
will continue moving eastward into the Atlantic for the following
days providing a easterly wind flow enhanced the shower activity
across the region. For Wednesday night, a change in wind direction
from the east southeast will increase the low level moisture
across the region. This will enhanced the shower activity in some
sections of the island, especially in the north due to the
direction of winds. Then, a new surface high pressure moving from
west of the Atlantic will bring once again drier air into the area
decreasing the instability and limiting the shower activity for
Friday in the morning hours.


&&

.AVIATION...

An approaching frontal boundary and an upper level trough
will increase the potential for convective activity across the local
flying area durg the prd. A line of TSRA with FQT LTG was located
ovR ATL waters Nw-N of PR mov E 20-25 kts. SCT-bkn lyrs nr
FL025...FL050...FL080. SHRA/Isold TSRA fcst to increase from the W
ovr ATL waters and spread eastwards ovr the islands and regional
waters during the morning the rest of prd. TEMPO MVFR conds psbl due
to SCT SHRA/Isold TSRA at TJBQ/TJMZ til 26/14z and at TJSJ aft
26/14Z. VCSH at all other local terminals durg prd. Winds will
continue fm S at 10 kt or less increasing to 10-20 kt with higher
gusts after 26/14z.


&&

.MARINE...
Across the regional water, seas up to 6 feet across the offshore
waters and local passages. Therefore, small craft operators are
urged to exercise caution.Then, by Saturday another northerly
swell will arrive into the Atlantic waters with seas up to 9 feet.
The high risk of rip current still for North central Puerto Rico,
Culebra and St. Croix until this afternoon.



&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 77 82 74 / 90 50 10 20
STT 83 74 84 74 / 60 60 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
539 AM AST Fri Dec 27 2019

.SYNOPSIS...
Moisture associated with a passing frontal boundary may linger
over the area and can result in cloudiness and shower activity
across the U.S. Virgin Islands and regional waters in the morning
hours. Then, by late morning the development of new showers across
interior sections of the main Island are expected. These showers
will be driven by the winds across the southwestern sections of
Puerto Rico. Therefore, not significants rainfall accumulations
are expected. In the upper and mid levels for the next days look
quite fair as a drier air mass move into the region by Saturday
night. By Sunday, another band of moisture will arrive into the
region and will result in scattered showers mainly northern and
eastern Puerto Rico and the U.S. Virgin Islands. Generally drier
air will then enter the area until the next front approaches on
Tuesday late in the evening.

&&

.SHORT TERM...Today through Sunday...
Frontal boundary and associated band of low to mid level cloudiness
will linger across the region through at least early Saturday but
will continue to gradually erode as a mid to upper level ridge
builds and spreads eastward across the region. This in turn will
strengthen the trade wind cap inversion during the next few days as
a surface high pressure ridge builds north of the region over the
upcoming weekend into the early part of next week. In the meantime
the upper level trough axis now over the northern Leewards, will
continue to lift northwards while filling. This has now placed the
forecast area on the subsident and more stable side of the upper
trough axis. However expect a low level convergent zone between the
building surface high across the western Atlantic and the frontal
boundary to maintain a shallow moist layer which will aid in the
development of scattered to occasionally broken cloud layers and
isolated to scattered showers across the region today through
Saturday. The fairly thick low to mid level cloud layer should limit
convective development today along with the improving stable and dry
conditions aloft. Continued improvement in the overall weather
conditions is forecast on Saturday and through Sunday as high
pressure builds and become the dominant weather feature across the
forecast area.

As a result of the changing weather pattern, expect light northerly
winds to become more northeasterly by Saturday; then more easterly
on Sunday and increasing as the local pressure gradient tightens in
response to the surface high pressure building north of the region.
Quick passing late evening and early morning showers will remain
likely over the regional waters waters and north and east coastal
areas each day through the weekend. This will be followed by only
isolated to scattered afternoon showers of short duration in and
around the islands for the weekend as mostly fair weather skies
should prevail.

.LONG TERM...Monday through Saturday
The long term period start with a surface high pressure located
across the North Atlantic. The surface high pressure could bring
drier air across the region and this could limit the shower
activity. However, a moisture band are forecast to move into the
area on Sunday and will result in shower activity across the
islands. By Monday, the same high pressure will increase the winds
and push residual moisture from the previous frontal boundary
into the region increasing the potential for shower development.
By Thursday, another surface high pressure enter into the west
Atlantic and change the wind direction from southeast. This could
result in increase of chance of rain due to a moisture across the
region from a new weak frontal boundary around the area. However,
much drier air in the region should limit the shower development
for Saturday.


&&

.AVIATION...
Frontal boundary extends across the northern Leeward
Islands into the northeast Caribbean btwn USVI and PR. SCT-BKN lyrs
nr FL025....FL050. BKN-OVC Btw FL090-FL100. Mostly -RA en route btw
PR and USVI with Mtn TOP Obscr ovr E PR due to -SHRA/low cld lyrs
til 27/12Z. VFR at all terminals durg prd. Few top nr FL120 w/SHRA
en route btw islands. Sfc wnds calm to lgt/vrb bcmg fm N-NE 5-15 kts
aft 27/14z.


&&

.MARINE...
Across the regional waters, seas up to 6 feet across the offshore
waters and local passages. Therefore, small craft advisory remains
in effect for the Atlantic Waters until Monday afternoon. The
northerly swell will arrive late this evening into the Atlantic
waters with seas between 8-10 feet. There is a moderate risk of
rip current for North central Puerto Rico, Culebra and St. Croix
until this this morning when become high. A second pulse, only
slightly weaker, will move into the northern waters from the
northeast on Sunday. Conditions should remain below small craft
advisory conditions Tuesday through Thursday of next week.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 82 75 84 74 / 30 30 50 50
STT 84 75 84 74 / 30 30 50 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
537 AM AST Sat Dec 28 2019

.SYNOPSIS...
A drier air mass is forecast to move into the area and limit shower
activity, but isolated to scattered showers cannot be ruled out
today. A band of moisture in advance of a building high pressure
ridge across the west Atlantic, will move over the area on Sunday
while lingering moisture from the recent passage of a frontal
boundary will return late Monday and increase the potential for
shower activity. Another frontal boundary will enter the Atlantic
waters by mid next week and may again result in increased shower
development across the region. Drying conditions will commence
next Friday.

&&

.SHORT TERM...Today through Monday...
A drier and more stable air mass will continue to filter in behind a
weakening frontal boundary which continued to drift south of the
islands this morning. This will result in mostly fair weather conditions
in and around the islands today. However, some late morning and
afternoon showers will remain possible across parts of the interior
sections and southwestern portions of Puerto Rico. A few showers
may also develop and affect parts of the U.S. Virgin Islands today
but no significant rainfall amounts are anticipated at this time.

By Sunday, another band of low-level moisture along an old frontal
zone is still forecast to slow sink southwards across the region
through Monday as a strong surface high pressure ridge builds and
spreads across the west and southwest Atlantic. This will result in
an augmentation of advective moisture, as the trade winds increase
across the region in response to the tightening of the local
pressure gradient. This will eventually lead to breezy conditions by
Monday. The expected shower activity will affect parts of the north
and east coastal sections but may move further inland by the early
morning as the trade winds increase. Periods of late evening and
early morning passing showers can also be expected in and around the
USVI on Sunday and Monday. During the afternoon hours, additional
showers to affect the central interior and southwest sections of
Puerto Rico, as well as on the west end and downwind of the U.S.
Virgin Islands. Although increasing low to mid level cloudiness is
expected with the passage of the frontal zone by Sunday and Monday,
the mid to upper-levels will be dominated by a building ridge of
high pressure. That said, expect stable/subsident and dry conditions
aloft with lesser chance for significant convective development and
mostly quick passing shower activity across the region. Consequently,
no significant rainfall accumulations are anticipated although there
may be brief periods of moderate to heavy rains.

.LONG TERM...Tuesday through Sunday...
At mid and upper levels, the building high pressure will result
in stable conditions and a drier air mass across the area. This
pattern will prevail through the middle of next week. However,
fragments of moisture from the previous frontal boundary will
return over the region dragged by the prevailing moderate to
strong trade winds and increasing the potential for shower
development and cloudiness. Thursday through Friday early in the
morning, the surface high pressure is forecast to move into
southwestern Atlantic and consequently change the wind direction
from northeast. This could result in cooler temperatures over
coastal areas and passing showers across the northern section of
the islands in the early morning and evening hours. Model guidance
suggest a drier air mass moving across the region by Friday, this
could further enhance the drying pattern for the weekend.

&&

.AVIATION...VFR cond thru fcst prd. Few SHRA with SCT-BKN lyrs nr
FL030...FL050 en route btw islands and along remnants of frontal
boundary btw E PR and northern Leeward islands. Wnds Lgt/Vrb to
calm bcmg fm the E-ENE at 10-15 kt with higher gusts and sea breeze
variations after 28/14z. No sig operational wx impacts attm.

&&

.MARINE...
The combination of a northeasterly swell and wind driven seas
will result in choppy and hazardous seas through the weekend.
Additionally, a building surface high pressure across the western
Atlantic will result in east to northeast wind flow around 15
knots. Today`s seas will range between 8 and 10 feet across the
Atlantic Water. Therefore, small craft advisories will are in
effect for most of the local waters. There is a high risk of rip
currents for some of the northern beaches of Puerto Rico, Vieques
and Culebra through the weekend. Conditions should remain below
small craft advisory conditions late Tuesday through Friday of
next week.


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
532 AM AST Sun Dec 29 2019

.SYNOPSIS...
A high pressure will build over the western Atlantic through next
week. This can promote fair weather conditions across the islands
with some passing showers for the next several days. However,
lingering moisture from the old frontal boundary will return on
sunday and this could increase the potential for shower activity
across the forecast area. In general, fair weather conditions are
expected during the next few days.

&&

.SHORT TERM...Today through Tuesday...
Mid to upper level ridge will continue to build aloft through early
next week while a strong surface high pressure ridge with continue to
spread across the southwest and western Atlantic. As this ridge
builds north of the region, still expect the remnants of a frontal
boundary to sink southwards across the region pushed by the fairly
strong north northeasterly wind flow. The bands of moisture along
this boundary is to then move over the area later today through
Monday with lingering shallow moisture to persist across the region
at least until Tuesday. For the period, overall fair weather is
expected with periods of passing early morning showers in some
areas. The increasing trade wind will give way to somewhat breezy
conditions by Monday and Tuesday.

Presently,isolated to scattered showers were observed across the
regional waters carried by the dominant east northeast trade winds.
Some showers were occasionally reaching parts of the islands from
time to time and producing brief downpours of mainly light to
moderate intensity. However during the rest of the overnight and
early morning hours periods of locally heavy rains will remain
possible isolated areas, but mainly along the north and east coast of
the islands. Later today through Monday expect an increase in
advective moisture as the aforementioned frontal boundary crosses
the area. This will provide sufficient moisture in the low levels to
aid in the development of evening and early morning shower activity
across the coastal waters and islands. Local forcing and daytime
heating will also aid in the development of afternoon showers each
day. Some of the rainfall may be locally heavy at times and could
lead to minor ponding of water on roadways and in poor drainage
areas. Afternoon shower activity over Puerto rico should be focused
mainly over the central and south to southwest section of PR and
well as on the west end and down wind of the USVI steered by the
prevailing east to northeast wind flow. By Monday and Tuesday shower
activity should be more in the form of streamers as winds are
forecast to increase as the Atlantic high builds and moves north of
the region.

.LONG TERM...Wednesday through Monday...
Mainly fair weather conditions are expected for the long term
period across the region due to a building a high pressure over
the western Atlantic. This dry pattern will prevail through the
middle of next week. Thursday through Friday, the surface high
pressure is forecast to move into central Atlantic and
consequently change the wind direction from northeast. This could
result in cooler temperatures over coastal areas and passing
showers across the northern section of the islands in the early
morning and evening hours. Model guidance suggest a drier air mass
moving across the region by Friday. This could further enhance
the drying pattern for the weekend and beginning of the next week.
However, isolated showers cannot be ruled out in the early morning
and evening hours across the northern sections of Puerto Rico and
the U.s. Virgin Islands.




&&

.AVIATION...VFR at all terminals thru fcst prd. Sfc wnds Lgt/Vrb
bcmg ENE around 15 knots with ocnl hir gust and sea breeze
variations aft 29/14Z. Passing trade wind -SHRA/SHRA in and around
the Leeward Islands and en route btw PR and USVI. SCT-BKN lyrs nr
FL025...FL050. No sig operational wx impacts attm.


&&

.MARINE...
Generally the combination of wind driven seas and a northerly swell
will continue to result in hazardous seas across the regional waters
and rough surf conditions along the northern exposed beaches of the
islands through the remainder of the weekend and at least early next
week. While wind speeds may periodically increase, the small craft
advisories still in effect for seas between 8-10 feet, with the
highest seas expected across the Atlantic waters. Life threatening
rip currents will continue across most of the northwest to eastern
beaches of Puerto Rico including Culebra and Vieques as well in St.
Thomas and St.Croix. Winds will continue from the east-northeast
between 10-15 knots and increasing between 15-20 knots on
Sunday/Monday across the Atlantic waters and eastern waters of the
islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 84 74 / 50 50 50 30
STT 84 74 84 76 / 50 50 50 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
520 AM AST Mon Dec 30 2019

.SYNOPSIS...

A wet pattern continues across the region as an old frontal
boundary slowly migrates westward. High pressure in the central
Atlantic is driving breezy winds and hazardous seas for most of
the local waters. However, seas are expected to get below Small
Craft Advisory criteria by tomorrow. A drier weather pattern will
prevail later this week as a large area of high pressure builds
over the region. However, passing showers are still possible
during this period.

&&


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

High pressure at mid and upper levels will spread east over most of
the Caribbean today through Wednesday. At upper levels flow will be
mostly northwest until Wednesday when it will turn to the north. Mid
levels above 600 mb will remain almost completely dry through
Wednesday as high pressure just east of the Bahama islands passes
over the area on Wednesday.

Very moist and easterly low level flow will continue to bring
showers --frequent at times-- across the area. Although eastern
Puerto Rico will have the most showers during the period,
afternoon showers in western Puerto Rico are expected each
afternoon and some showers will pass over and around the U.S.
Virgin islands. Moisture is best today and much of Puerto Rico
will see at least some rain. Winds are also increasing today as
mid latitude high pressure migrates into the central Atlantic.
Winds should diminish on Tuesday and Wednesday, but 10 to 15 knots
are still expected during the daytime hours and along the coasts.
The passing showers are not expected to yield more than three
quarters of an inch today nor one half inch in any one place
Tuesday and Wednesday except in very localized areas as the
moisture becomes more shallow then.


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

A fairly quiet period is expected in the longterm forecast. A strong
upper level ridge with an associated surface high pressure will move
out over the western Atlantic and create calm weather across the
region into the next week. There will still be pockets of
moisture around to drive some showers across the region. Without
the upper-level support needed to drive thunderstorm activity,
these showers will likely be weak some move along fairly quickly.
Low level flow looks generally easterly or east northeasterly so
the best chance for showers will be on the east side of Puerto
Rico as showers move inland and rise up the terrain of the island.
This appears especially true for Thursday and Friday, but less so
for the weekend as less moisture is expected. Into the next week,
an upper level trough with a cold front is forecasted to approach
the region, but not quite arrive into the forecast area before
breaking up. However, with plenty of time until this event,
confidence is low in this forecast.

&&


.AVIATION...

Periods of brief MVFR will increase across PR as a
band of moist air moves across the area with SHRA. Areas of mtn
obscurations will also dvlp. Wind 10-15 kt with gusts to 15-25 kt
vcnty SHRA. Tops btwn FL100-200. Max winds NW 35-45 btwn FL420-540.


&&


.MARINE...

Hazardous seas continue associated with strong pressure in the
central Atlantic, driving moderate to fresh winds across the
region. However, as this area of high pressure moves eastward,
these winds are expected to relax a bit, leading to calmer seas.
Thus, Small Craft Advisories will expire tomorrow. No swells are
expected thereafter for the rest of the week. Passing showers are
possible across local waters, with very minimal thunderstorm
activity.


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
449 AM AST Tue Dec 31 2019

.SYNOPSIS...

Slightly warmer temperatures are expected today, as well as the
continuation of a showery pattern. Scattered showers are possible
for later tonight during New Years celebrations. Thereafter, a
drying trend will occur for the rest of the week as high pressure
takes hold. Showers will still be possible however. Seas are
coming down and Small Craft Advisories will expire later today.

&&


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

High pressure at upper levels will continue over the central
Caribbean with northwest to north flow during the period. The mid
level high will drift from just north of Puerto Rico toward the
southeastern Bahama Islands during the period. Mid and upper levels
are completely dry during the period.

Lower levels continue very moist below 850 mb in easterly flow
that will bring showers--frequent at times-- across the area,
mainly on the eastern coasts and slopes. Although eastern Puerto
Rico will have the most showers during the period, afternoon
showers in western Puerto Rico are expected each afternoon and
some showers will also pass over and around the U.S. Virgin
islands. Showers and moisture will be best on Thursday afternoon
over most of Puerto Rico.

With a little more sun temperatures will be a little warmer over the
area. San Juan should reach the mid 80s under partly cloudy skies
today. A cooling trend will return on Thursday. Since 500 mb
temperatures will also increase overall stability will be better on
Thursday and so despite better moisture rain amounts will be quite
modest.


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

High pressure is expected to dominate the region from the lower to
upper levels of the atmosphere for Friday. This will reduce the
thunderstorm threat and lead to drier conditions. There will still
be showers around, but they will likely be weak and only isolated
to scattered. Steering flow at around 15-25 knots will keep any
showers moving along quickly, so impacts will be minimal. Both the
American and European models predict even drier conditions for
Saturday as the high pressure ridge really takes hold. As the high
continues its eastward progression for Sunday, bits of moisture
from an old frontal boundary are projected to move in, that could
lead to an increase in shower activity. The ridge begins to have
less of an impact as we move into the next workweek. However, no
major fronts or other weather systems are projected to arrive in
the long term forecast. Models hint at an increase in moisture for
next Monday through Wednesday that could facilitate similar
conditions to what we are seeing now, with a showery pattern
under easterly flow.

&&


.AVIATION...

Brief MVFR is expected til 31/22Z at TNCM/TKPK
otherwise SCT SHRA to prevail in easterly flow with some mtn
obscurations ovr mtn of PR. Wind 10-15 kt with gusts to 15-20 kt.
Tops btwn FL100-200. Max winds NNW-N 30-40 btwn FL330-540 strongest
nr FL400.

&&


.MARINE...

Seas across the region are dropping as easterly winds continue to
slow down. Wave heights are at around 5-6 feet for the near shore
Atlantic bouy, and 6-7 feet for the outer bouy, with both in a
declining trend. Thus, Small Craft Advisories will expire later
this morning, though small craft operators are urged to exercise
caution for the remainder of today. Calmer seas will prevail for
the next several days.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 75 86 75 / 50 40 40 40
STT 84 75 85 74 / 50 30 50 70

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
512 AM AST Wed Jan 1 2020

.SYNOPSIS...

More shower activity is expected for the next few days, and this
is especially true for tomorrow. Thereafter a drying trend is
expected with a ridge aloft and high surface pressure taking hold
across the region. Thus, minimal rainfall is expected over the
weekend. An increase in moisture and showers is forecasted for the
next workweek. Seas have come down as winds have weakened across
the region. Calmer seas will prevail for the next few days.

&&


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

High pressure at upper levels will continue over the central
Caribbean with northerly flow during the period. The mid level high
will drift from just north of Puerto Rico toward the southeastern
Bahama Islands during the period. Mid and upper levels are
completely dry during the period although moisture extends up to 600
mb though Thursday night.

Lower levels, continue mostly moist below 850 mb in easterly flow
that will bring showers--frequent at times-- across the area mainly
on the eastern coasts and slopes. Although eastern Puerto Rico will
have the most showers during the period, afternoon showers in
western Puerto Rico are expected each afternoon and some showers
will also pass over and around the U.S. Virgin islands. Showers and
moisture will be best on Thursday afternoon over most of Puerto
Rico due to the passage of a weak trough.

Temperatures will continue above normal today. San Juan should reach
the mid 80s under partly cloudy skies today. A cooling trend will
return on Thursday. Since 500 mb temperatures will also increase
overall stability will be better on Thursday and so despite better
moisture rain amounts will be quite modest except in southwestern
Puerto Rico where urban and small stream flooding could occur.


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

High pressure will still be firmly in control for Saturday, though
the surface high associated with the ridge aloft will be moving
quickly eastward. With this movement, pressure gradients will relax
from Saturday into Sunday, meaning weaker easterly trade winds. As
for shower chances, the weekend looks fairly dry, with only weak
patches of moisture expected that could lead to some isolated to
scattered shower activity. Low level steering winds will keep the
showers moving quickly for Saturday, but less so for Sunday. Minimal
to no thunderstorm threat is likely.

Our region gets clipped by an upper level trough for Monday, and the
cold front is not forecasted to make it to our region before
weakening and breaking up, so impacts will be minimal. However,
as high pressure leaves the area, higher levels of moisture will
move in, giving us a better chance for rainfall. We will still be
under the influence of upper level ridging which will keep the
thunderstorm threat down. Tuesday looks wetter, as a more
organized band of moisture is forecasted to move in, with
continued moisture advection for the rest of the week. Generally
easterly flow will favor showers for the northeast to southeast
coast of Puerto Rico.

&&


.AVIATION...

SHRA ovr the local waters to cont but TAF stations
expected to remain VFR this morning. Some areas of 5 SM in smoke to
cont thru 01/12Z in PR. +SHRA to dvlp ovr SW PR aft 01/16Z with
periods of MVFR/IFR CIGS/VSBYS and mtn obscurations. Wind ENE 10-15
kt with gusts to 15-20 kt. Max winds NW-N 20-30 btwn FL280-450
strongest nr FL400.

&&


.MARINE...

Seas across the region have really come down with wave heights
now around 4-5 feet for the nearshore Atlantic buoy, and 5-6 feet
for the outer Atlantic buoy. Seas will remain fairly calm for the
next several days. Long range models are hinting at another swell
event for the middle of next week. Showers will continue over the
local waters, particularly tomorrow, with a drying trend expected
into the weekend.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 84 75 / 80 80 80 80
STT 84 73 83 74 / 40 50 50 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
456 AM AST Thu Jan 2 2020

.SYNOPSIS...

More rainfall is expected to continue across the region,
particularly for eastern Puerto Rico as showers move inland from
the Atlantic. Drier conditions will prevail for the weekend, as
high pressure establishes itself across the central Atlantic. More
moisture moves in for the next workweek, in what appears will be a
fairly typical winter weather pattern. Seas will remain calm for
today, though increase minimally for tomorrow.

&&


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

High pressure at upper levels over the central Caribbean will drift
north over the Windward Passage and Hispaniola during the period
with northerly flow today and Friday over the forecast area that
will turn northeast on Saturday. The mid level high will remain
fairly close under the upper level high. Mid and upper levels are
completely dry during the period although some moisture extends up
to 650 mb though Friday morning.

Lower levels continue mostly moist below 850 mb in easterly flow
that will bring showers--frequent at times-- across the area mainly
on the eastern coasts and slopes. Although eastern Puerto Rico will
have the most showers during the period, afternoon showers in south
western Puerto Rico and along the Cordillera Central are expected
each afternoon and some showers will also pass over and around the
U.S. Virgin islands. Showers and moisture will be best this
afternoon over most of Puerto Rico due to the passage of a weak
trough and moisture associated with it and behind it.

Temperatures will continue at or slightly above normal today. San
Juan should reach the mid 80s under variably cloudy skies. A cooling
trend has begun. Since 500 mb temperatures have increased overall
stability will be better today, and so despite better moisture later
today and tonight, rain amounts will be quite modest except in
southwestern Puerto Rico where urban and small stream flooding could
occur. A dry slot is noted in the GFS at 700 mb and will pass
through the area on Friday to diminish the showers then.


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

High surface pressure will begin to quickly move out of the area by
Sunday, though we will continue to feel the effects of the ridge
aloft for a bit longer as it decouples from the surface high. This
will keep the upper levels of the atmosphere with unfavorable
conditions for thunderstorms. However, with the low-level flow
generally from the northeast for Sunday into Monday, this wind
direction is usually conducive for showers across the region for
the north and east coasts of Puerto Rico. An increase in moisture
will occur heading into the next workweek that will help to
increase showers across the region. Though no major fronts or
other weather systems are expected, patches of moisture riding in
on the easterly trade winds will bring periods of rainfall across
the region, again favoring the north and east coast.

Heading into the middle to end of the workweek, high surface
pressure will once again take hold across the region, favoring
strong easterly winds over the forecast area. These forecasted winds
of roughly 25 mph will certainly have an impact on marine
conditions. Decent moisture advection through the workweek will
continue the showery pattern, with upper levels never really
becoming very favorable for thunderstorms. Low level steering flow
will be stronger as the next week progresses.

&&


.AVIATION...

SHRA ovr the local waters will diminish slowly but TAF
stations are expected to remain VFR except for +SHRA to dvlp ovr SW
PR and over the Cordillera Central aft 01/18Z with periods of
MVFR/IFR CIGS/VSBYS and mtn obscurations. Wind ENE 10-15 kt with
gusts to 15-20 kt. Max winds NW 25-35 kt btwn FL380-500 strongest nr
FL400.

&&


.MARINE...

Seas will continue below 5 feet today, but increase slightly for
tomorrow. This slight increase won`t last long, as calm seas will
continue into next week. The next swell event appears to begin
next Tuesday as projected by mid-range forecast models, though it
does not appear to be a major event. Isolated to scattered showers
will continue across local waters.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 76 83 74 / 40 60 30 40
STT 84 74 84 74 / 50 80 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
504 AM AST Fri Jan 3 2020

.SYNOPSIS...

We are waking up to showers this morning, and more scattered
showers are expected throughout the day. Somewhat drier
conditions will prevail over the weekend as a ridge aloft and high
surface pressure take hold across the region. However, isolated to
scattered showers are still possible. These conditions will not
last long as higher moisture and a wetter pattern will persist
throughout the next workweek. A swell is expected for next Tuesday
and Wednesday.

&&


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

High pressure at upper levels over the Windward Passage will
continue through the period generating northeasterly flow over
Puerto Rico and the U.S. Virgin Islands. The mid level high will
remain fairly close under the upper level high. Mid and upper levels
are completely dry during the period.

A weak low level trough is moving into Puerto Rico and is keeping
lower levels quite moist. That moisture has increased since
midnight. This will bring another day of showers and limited
sunshine to the area. The GFS shows moisture at 850 mb diminishing
considerably after 6 PM AST this evening beginning at San Juan and
spreading through the majority of the forecast area by 2 AM on
Saturday. Shower activity will therefore decrease overnight.
Scattered showers are still expected to remain on the upslope side
of Puerto Rico and the U.S. Virgin Islands through Sunday. High
pressure passing north of the area this morning will bring several
bands of moisture through the area and maintain a northerly
component in the easterly flow. This will bring cooler air in from
the mid Atlantic that will still have moist lower levels.


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

Heading into the next workweek, the northeastern Caribbean will be
under a weak ridge at mid to upper levels with a large trough to the
north. Associated with this trough, a cold front will stall to
our northwest and eventually break up, with its moisture being
pushed back westward on Tuesday. However, as the front approaches
for Monday, we will see an increase in low-level moisture over
the region from the east, with a favorable wind flow from the
east-northeast to produce showers over the region. As usual, the
northern and eastern coasts of Puerto Rico will take the brunt of
these showers, along with the islands to the east of Puerto Rico.
For Tuesday and Wednesday, the wind flow appears to be more
easterly or east-southeasterly, putting the wettest conditions to
the eastern and southern coasts of Puerto Rico.

Wind will pick up for Tuesday as high surface pressure builds over
the Central Atlantic. This will help showers to move along a bit
faster and thus be less impactful. A similar showery pattern will
continue for the rest of the workweek. The aforementioned high
surface pressure will quickly move off to the east Tuesday night and
into Wednesday, but will be followed by a stronger high pressure
system. This one is expected to bring much windier conditions to
the region, and will likely result in a wind driven swell, as
described in the marine section.

&&


.AVIATION...

SHRA cont ovr the local waters and much of the local
islands in northeast flow. Areas of MVFR and mtn obscurations will
cont thru 03/21Z. +SHRA to dvlp ovr SW PR and over the Cordillera
Central aft 03/18Z with periods of MVFR/IFR CIGS/VSBYS and mtn
obscurations. Wind NE 10-15 kt with gusts to 15-20 kt. Max winds N
30-40kt btwn FL310-540 strongest nr FL460.

&&


.MARINE...

As expected, seas are increasing a bit this morning. However, wave
heights will stay below 6 feet for the next few days. Small craft
operators are still urged to exercise caution given the seas and
breezy winds. The next swell event is expected for Tuesday and
Wednesday as a northwesterly swell, induced by a low pressure system
in the Atlantic, moves into the region. Following this event, a wind-
driven swell is forecasted for late in the next workweek. Isolated
to scattered showers will also continue across the local waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 75 83 74 / 70 30 40 50
STT 84 74 84 73 / 60 30 30 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
440 AM AST Sat Jan 4 2020

.SYNOPSIS...
Mid to upper level ridge will promote a mainly fair weather
pattern across the region. Diurnally induced showers should be
limited today, but showers could increase by the start of the
workweek as a pre-frontal trough approaches the islands. Winds
will pick up by the latter part of the week.

&&

.SHORT TERM...Today through Monday...
A mid level to upper level ridge is forecast to hold through the
short term period across the Caribbean basin. This will promote
stable conditions and mostly fair weather conditions across the
islands through at least Sunday. The best available moisture will
be confined below 800 mb today and increase to 750 mb on Sunday
and Monday. A surface high north of the region will move into the
central Atlantic tonight and weaken. This will promote a moderate
to locally fresh trade wind today, and diurnally induced afternoon
showers should be limited to the mountain ranges and southern
sections of PR with mostly light rainfall amounts. On Sunday,
winds diminish and a col develops north of the region between late
Sunday and Monday, as a front approach the region from the
northwest. Afternoon showers should develop and linger mainly over
the Cordillera Central and southern slopes of Puerto Rico on
Sunday. For Monday, a weak pre-frontal trough is forecast to
develop just east/northeast of the local area and is forecast to
cross the region from east to west. This will increase the chances
for scattered to locally numerous showers to develop across the
region.

.LONG TERM...Tuesday through Sunday...
High pressure system is expected to hold over the eastern
Caribbean for the earlier part of the long-term forecast period.
However, at the low levels, fragment of moisture are expected to
be dragged by the trade winds over the islands, with showers
being advected across portions of eastern Puerto Rico and over the
U.S. Virgin Islands. By Thursday, another stronger high pressure
will migrate into the area, resulting in a tight pressure
gradient, and therefore, an increase in winds over the region. In
fact, the latest guidances are suggesting very gusty conditions
through at least the second half of the weekend over the area. As
a result of these winds, marine conditions are expected to
deteriorate. In addition, an increase in low level moisture is
also expected by the second half of the workweek as these winds
carry more groups of clouds and showers over the region.


&&

.Aviation...Mainly VFR conditions expected to prevail across all
terminals during the next 24 hours. However, light trade wind
showers in a 10-15 kt northeast wind flow could cause RA/VCSH at
Leeward/USVI/Northern PR terminals during the morning hours. Then,
afternoon SHRA developing over central/southern PR could cause brief
MVFR cigs at TJPS.


&&

.MARINE...
Seas below 6 feet are expected for today. However, winds up to 20
knots are expected for the local passages and the Caribbean
waters. Therefore, small craft operators are urged to exercise
caution in this area. For the workweek, a northerly swell is
expected to arrive on Tuesday, followed by a wind-driven swell on
Thursday. Seas are expected to be above 7 feet during this period.
For the beachgoers, there is a moderate risk of rip currents for
the northern coast of Puerto Rico, Vieques, Culebra, St. Thomas
and St. Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 73 83 74 / 40 20 50 60
STT 84 73 84 73 / 30 30 50 60

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
514 AM AST Sun Jan 5 2020

.SYNOPSIS...
Lighter winds with passing showers are expected for today. A weak
trough is expected to reach the islands on Monday, resulting in an
increase in shower activity. For the latter part of the workweek
and into the weekend, winds will pick up as a strong high pressure
system moves north of the area.

&&

.SHORT TERM...Today through Tuesday...
An upper-level ridge over the Caribbean basin will prevail
through the short term period. This will continue to promote
stable conditions and cap moisture below 700 mb. Light steering
winds are expected today, as a col forms north of the region
between a front over the western Atlantic and a weak surface high
over the eastern Atlantic. Fragmented clouds and passing showers
across the Atlantic waters will be carried by a weak northeasterly
wind flow today, reaching portions of the northern half of Puerto
Rico and across the U.S. Virgin Islands. Overall, showers should
be of light to moderate intensity with the best measurable
rainfall amounts expected across the northern coast of PR. For
this afternoon, daytime heating and the sea breeze convergence
over south/southwest PR will cause showers to develop over the SW
quadrant of PR and linger through the evening hours over the
Caribbean waters.

Meanwhile, a weak trough is forecast to develop south of the col and
move across the local Atlantic waters on Monday. This will maintain
a northerly component on the steering winds and scattered showers
are expected to develop over the Atlantic coastal waters and affect
the northern and eastern sections of PR as well the northern USVI
through Monday morning and then enhance afternoon showers over the
interior and western sections of PR. A weak surface high pressure
rolls eastward off the Florida coast on Tuesday, increasing the
local winds and trade wind shower activity across the regional
waters. However, drier air is expected on Tuesday and showers will
be limited to the west coast of PR in diurnally induced isolated
showers.

.LONG TERM...Wednesday through Monday...
The main story for the long-term forecast will be the strong winds
that will establish over the area for most of the period. A strong
high pressure system is expected to move from the west toward the
central Atlantic Ocean. This will tighten the pressure gradient
over the islands, creating very gusty conditions. Winds will
start to pick up on Thursday, but they will maintain through the
weekend. Under this windy pattern, seas will deteriorate and will
become hazardous. In addition, fragment of moisture embedded in
the trade winds will move across the area from time to time,
bringing passing showers mostly to the east half of Puerto Rico as
well over the U.S. Virgin Islands and surrounding waters. However,
due to the strong winds, no significant rainfall accumulation is
anticipated.


&&

.Aviation...Mainly VFR conditions expected across all terminals.
However, SCT-BKN cigs btw FL030-FL070 with passing -SHRA will
continue through the morning hours across the USVI and northern PR
terminals. Northeast winds around 10 kt are forecast to prevail
today. Sea breeze variations expected after 14z mainly at TJPS/TJMZ.

&&

.MARINE...
Seas at 5 feet or less with wind at 5 to 15 knots are expected for
today. On Tuesday, a northerly swell will reach the Atlantic
waters and passages, resulting in hazardous seas. Another wind-
driven swell is expected for the latter part of the workweek. For
the beachgoers, the risk of rip currents is moderate for the
beaches along the northern coast of Puerto Rico and Culebra and a
few beaches along northern St. Thomas and eastern St. Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 75 82 72 / 40 40 60 20
STT 84 73 83 72 / 40 50 60 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
454 AM AST Thu Jan 9 2020

.SYNOPSIS...

A strong surface ridge will cause windy conditions across the
region now through early next week. The easterly trade winds will
transport frequent showers across Puerto Rico and the U.S. Virgin
Islands over the next several days. Rough and hazardous wind
driven seas across the regional waters and life threatening rip
currents across most of the beaches of all the islands.


&&

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

A frontal boundary will moves eastward across the Atlantic basin off
to the north of the islands. Surface high pressure, behind this
feature, will exit the U.S. Eastern Seaboard tightening the local
pressure gradient and promoting windy easterly across the northeast
Caribbean. Under this weather pattern, patches of moisture embedded
in the trades will bring clouds and showers across the islands at
times. However, a mid- to upper-level high pressure will confined
moisture to the low levels, limiting the accumulations of these
showers.

The main concern should be in coastal areas of the northern U.S.
Virgin Islands and north and east Puerto Rico, where it is expected
hazardous coastal conditions through the forecast period. Beachgoers
should monitor the Coastal Hazard Message (CFWSJU) text product for
additional information.

&&

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

A strong surface ridge anchored across the western Atlantic will
promote breezy conditions and surface winds of 20 to 30 kts with
higher gusts Sunday through early next week. Also, the converging
winds over the region pull patches of moisture into the region,
which will lead to fast-moving isolated to scattered showers, over
Puerto Rico as well as the U.S. Virgin Islands. At, the mid-
levels a ridge is expected to hold over the area through Monday,
then the ridge is expected to weaken and become elongated from the
northeast to the southwest. The mid-level ridge is forecast to
strengthen again on Wednesday. At, the upper-levels both the GFS
and ECMWF models develop an upper-level low over the eastern
Atlantic on Monday this will create weak troughiness in the upper-
levels across the region. The upper-level low east of the area
progged to weaken and lift northeast on Thursday, with an upper-
level ridge moving overhead. Although, frequent showers are
forecast to move over the area through the long-term period, light
rainfall accumulations are progged; as a result of fast surface
winds, which will keep showers moving quickly through the region.

&&

.AVIATION...

Mainly VFR conditions are expected to continue through the forecast
period. Winds will be out of the E-ENE at 10 to 15 knots, increasing
between 15 and 25 kt with gusty winds up to 35 kt aft 09/13z. Under
this wind flow, occasional SHRA and clouds moving across local
terminals could momentarily lower VIS.

&&

.MARINE...

Small craft operators are urged to exerise caution across the
local and regional waters due to choppy seas up to 6 feet and
winds 20 to 25 kts with higher gusts. Winds will continue to
increase today across the local and regional waters, the
increasing winds will cause Small Craft Advisory conditions this
afternoon through the weekend. Therefore, Small Craft advisories
will be in effect this afternoon. A high risk of rip currents
continues for beaches along the north coast of Puerto Rico,
Culebra and Saint Thomas.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 73 84 73 / 50 60 50 30
STT 85 73 85 72 / 50 40 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
557 AM AST Fri Jan 10 2020

.SYNOPSIS...

A high pressure moving across the Atlantic waters will cause
windy conditions and frequent showers across the area now through
the weekend. Additionally, the high will create wind-driven swell
across the Atlantic and Caribbean waters through early next week.
Winds are forecast to range from 20 to 25 kts with higher gusts
likely, due to the tightening pressure gradient over the area.

&&

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

The surface high pressure across the western Atlantic is promoting
windy easterlies across the northeast Caribbean. Therefore, patches
of moisture embedded in the trades will bring clouds and showers
across the islands from time to time. A mid- to upper-level high
pressure will limit vertical development and confined moisture to
the low-levels of the atmosphere, reducing rainfall accumulations.

The main concern should be in coastal areas of the U.S. Virgin
Islands and Puerto Rico, where it is expected hazardous coastal
conditions through the forecast period. Beachgoers should monitor
the Coastal Hazard Message (CFWSJU) text product for additional
information.

&&

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

Recent model guidance has remained consistent with the evolution
of the long-term period. A strong surface ridge will control the
western Atlantic waters and cause breezy conditions through the
middle of the work, with winds ranging from 20 to 30 mph with
higher gusts. Also, the strong easterly trade winds are forecast
to converge over the region and pull moisture across Puerto Rico
and the U.S. Virgin Islands. Therefore, expect transient showers
Monday through the middle of the workweek. These showers will
produce light to moderate rainfall; however, at this time, light
rainfall accumulations are progged, as a result of the fast
surface winds that will keep showers hurrying through the region.

The GFS and EURO shows a mid-level ridge weakening and retreating
to the northwest of Puerto Rico on Monday as a result of a mid-
level trough; the mid-level trough will pull a weak cold front
close to the area late monday into Tuesday. Then the mid-level
ridge is progged strengthen again over the region by Wednesday. At
the upper-levels, both the GFS and ECMWF models develop an upper-level
low over the eastern Atlantic on Monday; this will create weak
troughiness in the upper-levels across the region. The upper-level
low east of the area is forecast to weaken and lift northeast on
Thursday, with an upper-level ridge moving overhead. At the time,
late Monday and Tuesday will be the wettest days due to added
moisture from the weak front, which is forecast to sink north of
Puerto Rico late Monday into Tuesday, as well as the moisture
transport from the easterly trade winds. Thursday and Friday
guidance shows the bulk of the moisture abating; however, small
pockets of moisture are still forecast to move over the area.

&&

.AVIATION...

Mainly VFR conditions are expected to continue through the forecast
period. Winds will be out of the E-ENE at 10 to 15 knots, increasing
between 15 and 25 kt with gusty winds up to 35 kt aft 10/13z. Under
this wind flow, occasional SHRA and clouds moving across local
terminals could momentarily lower ceiling and VIS.

&&

.MARINE...

Fresh to strong winds up to 25 knots will generate hazardous seas
up to 10 feet across most of the local waters. As a result, Small
Craft Advisories are in effect. Marine conditions will continue
to deteriorate during the next few days with seas increasing up to
14 feet by Saturday. There is a high risk of rip currents for
beaches along the north and southeast coast of Puerto Rico,
northwest coast of Saint Thomas, and most beaches in Vieques,
Culebra and Saint Croix. The high risk will extend to most beaches
along the south to southwest coast of Puerto Rico this morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 84 74 / 60 60 50 50
STT 86 77 85 78 / 30 50 50 50