Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
409 PM AST Tue Dec 5 2017

.SYNOPSIS...

A weak shear line and moist easterly flow will continue to spark
showers and thunderstorms today through Wednesday. Later in the
week, models indicate a backdoor front working in from the east
this front will possibly filter in drier air into the forecast
area.


&&

.SHORT TERM...

At the lower levels a frontal boundary and a weak shear line
north of the islands will continue to move southward near the
forecast area. At the upper levels weak troughiness remains. The
San Juan skew-T sounding and model data shows an upper level jet
of 50 to 60 kts over Puerto Rico and will remain until early
Thursday morning. The islands are in the right entrance of the
jet. Rising air and favorable upper level divergence is found in
this area. The easterly wind flow and favorable upper level
dynamics will lead to showers and thunderstorms today through
Wednesday. Cloudy to partly cloudy skies overnight and tomorrow.
Daytime high temperatures will reach the lower to mid 80s while
higher elevations will climb the mid to upper 70s.

.LONG TERM...

.From Previous Discussion...Friday through Monday...

Precipitable water begins to fall late Thursday afternoon and
continues through Friday evening when the shear line backs into
the area from the northeast bringing cooler and drier air behind
it. A ridge aloft will build and sharpen over the Mona Channel
Friday and Saturday to enhance this drying effect. The lowest
levels will continue to see bands of moisture riding through on
the northeast flow, however and this will bring instability and
showers to the area. The showers will mainly affect the U.S.
Virgin Islands and the windward side of Puerto Rico, however.
Another front will approach the area from the northwest with
moisture ahead of it beginning to infringe on the northwest corner
of the forecast area Sunday and Monday. The ridge aloft will
weaken and round out early next week, but remain in the area.


&&

.AVIATION...

Mostly VFR conditions at all TAF sites through the
forecast period with some mtn obscurations and SHRA/TSRA in and
around TJMZ/TJBQ/TIST/TJSJ till 05/22z. VCTS/VCSH possible at the
USVI and Leeward terminals as well as JSJ overnight. ENE winds 10-15
knots with some sea breeze variations, becoming at around 10 knots
overnight.


&&

.MARINE...

Marine conditions will continue to deteriorate as a
northerly swell continues to invade the local waters. Winds are
also expected to increase. Therefore. Hazardous marine conditions
and dangerous rip currents expected through at least the end of
the workweek.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 76 85 75 84 / 40 40 40 60
STT 76 85 75 85 / 50 20 50 60

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
501 AM AST Wed Dec 6 2017

.SYNOPSIS...Broad polar trough north of the region will continue
eastward into the central Atlantic, as a mid to upper level ridge
will move across the west Atlantic and build overhead by Friday.A
surface low over the central Atlantic and a building high pressure
ridge across the western Atlantic will create a moderate east to
northeast wind flow across the forecast area. Fragmented moisture
along an old frontal shear line will continue to be transported
in the prevailing easterlies across the region from time to time.

&&

.SHORT TERM...Today through Friday...
A frontal boundary and a weak shear line across the Atlantic waters
just north of the local islands will continue to sink southward near
or across the forecast area during the next couple of days. An upper
levels trough moving southeast of Florida will also continue to provide
good divergence aloft today. Latest TJSJ sounding and model data shows
an upper level jet of 50 to 80 knots over the region. These upper
level features will continue to provide favorable upper level dynamic
to induce the development of showers and thunderstorms across the
region. For today, under an east to east- northeast steering wind
flow, showers and possible thunderstorms are expected mainly over
the mountain ranges of PR and into the interior, western and southwest
portions of the islands. Across the USVI, under the evolving trough
pattern aloft, isolated to scattered showers are expected.

For Thursday, a more easterly wind flow will dominate the local area
and showers should focus more across the western interior portions
of PR with streamers expected to develop each day across the USVI. A
mid to upper level ridge building over the forecast area later in
the forecast period will bring drier air and fair weather conditions
across the region beginning on Friday.

.LONG TERM...Saturday through early next week...
Model guidance continued to suggest a significant decrease in
precipitable water by Saturday, as the aforementioned shear line
sinks south of the region while dissipating. This pattern will
usher a cooler and drier airmass across the forecast area by the
weekend. As the ridge builds overhead, expect increasing stability
and capping aloft. This in turn will enhance the drying effect
and limit moisture convergence in the low levels through Saturday.
The tightening of the low level pressure gradient will however
increase the east to northeast trade winds, resulting in periods
of passing showers across the local waters and north and east
coastal sections of the islands during early morning hours. This will
be followed by mostly fair weather skies during the day, except for
some showers over parts of the central and southwest sections of Puerto
Rico. A few showers may also form and quickly stream westward on the
windward side of the U.S. Virgin islands.

Some By Sunday and through Monday, expect another quick surge of northeast
trade wind moisture across the region increasing the chance for early
morning and afternoon showers. Another cold front is forecast to approach
and stall just northwest of the region by Tuesday and Wednesday of
next week, as the upper level ridge erodes and moisture pooling increases
once again across the forecast area.

&&

.AVIATION...Mostly VFR conditions are expected to prevail through
06/15z across the local flying area. Between 06/16z-22z SHRA/TSRA
are expected to affect the western and interior portions of PR with
MVFR and mountain obscuration expected with this activity. Across
the USVI terminals, SHRA expected in and around terminals. Winds from
E-ENE at 10-15 kts until 06/13Z increasing to 15-20 knots after 06/14Z
with sea breeze variations.

&&

.MARINE...Small craft advisories will be in effect for most of the
regional waters and passages beginning today due to increasing trade
winds and the arrival of a northeasterly swell, with building seas
of 7 feet or greater. Please refer to the latest Coastal Waters
Forecast and Marine Weather Message for additional info.

There is a high risk of rip currents across some of the northern
beaches of Puerto Rico,Culebra, St Thomas and St Croix today.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 76 84 73 / 40 40 40 40
STT 85 75 84 74 / 20 50 50 40

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
503 PM AST Wed Dec 6 2017

.SYNOPSIS...Mid to upper level ridge will build from the west
and hold through the end of the week. A surface high pressure
across the western Atlantic will move into the central Atlantic
and result in moderate to locally fresh trades across the forecast
area. Patches of low level clouds and showers associated to an
old frontal boundary will continue to move across the region from
time to time.

&&

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

Upper level trof will continue to exit the region to the east.
Frontal boundary will continue to result in periods of showers
through Thursday across the islands. Building surface high
pressure north of the region will result in breezy conditions
across the regional waters and over portions of the islands for
the next few days. East to northeast winds will keep pushing
showers inland across the USVI and over portions of northeastern
Puerto Rico through early Thursday morning. Ponding of water in
poor drainage areas is expected with these showers.

By Thursday afternoon, as upper ridge builds and moisture erodes
across the region...diurnally induced afternoon convection is
expected mainly along the Cordillera Central and western areas of
Puerto Rico. Streamers with light showers are expected to develop
downwind of the USVI. By Friday, drier air aloft and a more stable
atmosphere will result in fair weather conditions across the
region.

.LONG TERM...Saturday through early next week...

...FROM PREVIOUS DISCUSSION...

Model guidance continued to suggest a significant decrease in
precipitable water by Saturday, as the aforementioned shear line
sinks south of the region while dissipating. This pattern will
usher a cooler and drier airmass across the forecast area by the
weekend. As the ridge builds overhead, expect increasing stability
and capping aloft. This in turn will enhance the drying effect
and limit moisture convergence in the low levels through Saturday.
The tightening of the low level pressure gradient will however
increase the east to northeast trade winds, resulting in periods
of passing showers across the local waters and north and east
coastal sections of the islands during early morning hours. This will
be followed by mostly fair weather skies during the day, except for
some showers over parts of the central and southwest sections of Puerto
Rico. A few showers may also form and quickly stream westward on the
windward side of the U.S. Virgin islands.

From Sunday and through Monday, expect another quick surge of
northeast trade wind moisture across the region increasing the
chance for early morning and afternoon showers. Another cold front
is forecast to approach and stall just northwest of the region by
Tuesday and Wednesday of next week, as the upper level ridge
erodes and moisture pooling increases once again across the
forecast area.


&&

.AVIATION...Mostly VFR conditions at all TAF sites through the
forecast period with some mtn obscurations and SHRA/TSRA possible in
and around TJMZ through 06/22z. Periods of SHRA with MVFR conds
likely across the USVI terminals as well as JSJ. ENE winds 10-15
knots with some sea breeze variations.

&&

.MARINE...A wind surge between 15-20 kts at the surface and
a northeast swell arriving on Thursday, will result in hazardous
seas and rough surf conditions across the regional waters and
coastal areas of the islands. Small craft advisories are in
effect through Saturday. Beach goers are urged to avoid the
northern and eastern beaches exposed to the northeast swell.



&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 76 84 75 86 / 60 60 10 40
STT 75 85 74 85 / 50 50 10 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
630 AM AST Thu Dec 7 2017

.SYNOPSIS...Building surface high pressure north of the region
will continue to push the moisture remnants from an old frontal
boundary southwards across the islands and into the Caribbean
waters today through early Friday. As the mid to upper ridge
builds over the region, moisture transport will also erode
resulting in improving weather conditions by Friday and into the
upcoming weekend. Breezy conditions are still expected to persist
across the local islands and coastal waters at least through
Friday, then gradually diminish by the weekend, as the surface
high pressure ridge relaxes and the local pressure gradient
weakens.

&&

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

Weather radar detected scattered moving west southwestward across
the region overnight and early this morning with few of them
affecting the U.S. Virgin Islands, Vieques, Culebra as well as the
eastern and northern sections of Puerto Rico from time to time.
This activity was associated with a weak frontal boundary just
across the region. Upper level ridge will continue to build across
the region for the next several days. A weak frontal boundary
will continue across the region today, resulting in periods of
showers across the local islands and surrounding waters. The East
to northeast winds will continue to bring showers across Vieques,
Culebra, the USVI and over portions of northern Puerto Rico during
the rest of the morning. Ponding of water in poor drainage areas
is expected in association with these showers. For this afternoon
available moisture and local effect will produce showers and a
couple of thunderstorms along the Cordillera Central as well as
across western sections of Puerto Rico. Some streamers with light
showers are expected to develop downwind of the USVI. Building
surface high pressure north of the region will push the frontal
boundary remnants across the Caribbean waters tonight and Friday.
As the upper ridge builds over the region, moisture is also
expected to erode. As this happens, weather conditions are
expected to improve Friday and during the upcoming weekend, but
breezy conditions will remain across the local waters and the
local islands for the next few days. The east northeast trade
winds will bring small patches of low level moisture across the
local islands and surrounding waters during the upcoming weekend
but the upper ridge will inhibit the development of significant or
widespread precipitation.


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

Sunday and Monday...expect another quick surge of northeast trade
wind moisture across the region increasing the chance for early
morning and afternoon showers. A cold front is forecast to move
across the west Atlantic and stall just northwest of the region by
Tuesday and Wednesday of next week, as the upper level ridge erodes
and moisture convergence and pooling increases once again across
the forecast area under a light to moderate southerly wind flow.
The potential for shower and thunderstorm development will therefore
increase by the middle of next week, followed by a return of the
easterly winds with lesser convective activity forecast by the end
of the work week.

&&

.AVIATION...SHRA expected to continue across the local area causing
VCSH across the USVI terminals as well as TJSJ and TJBQ. Easterly
winds at about 10-15 knots this morning will increase at 15-20 knots
and gusty near SHRA after 07/13Z. There may be brief periods of MVFR
conditions but VFR conditions will prevail. SHRA/TSRA expected after
07/16Z near TJMZ.

&&

.MARINE...Small craft advisory continues in effect for most of the
local waters due to hazardous seas up to 10 feet. There is also a
high risk of rip currents for the northwest to northeast beaches
of PR as well as many beaches in Culebra and Vieques islands as
well as Saint Croix and Saint Thomas.

Recent buoy data and model guidance both suggest an increase in swell
height and period today through Friday, which can be observed already
in buoy 41043 and the distant buoy 41044 heading our way. The near shore
buoy San juan buoy was now around 8 feet. Due to the strong winds and
swell driven seas, large breaking waves and hazardous surf conditions
will be possible. Therefore a high surf advisory has been issued
for the northwest to northeast beaches of Puerto Rico, adjacent
islands and the northern U.S. Virgin Islands. Please refer to the
latest Coastal Hazard and Marine Weather Message issued by the
National Weather Service WFO San Juan PR.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 76 87 74 / 50 10 40 30
STT 85 74 84 75 / 50 10 20 30

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
511 PM AST Thu Dec 7 2017

.SYNOPSIS...Mid to upper level ridge will hold through the end of
the week. A broad surface high pressure across the central
Atlantic will continue to result in moderate to locally fresh
trades across the forecast area. A drier weather pattern is
expected during the next few days. However, showers embedded on
the trades will continue to move across the region from time to
time. Moisture content increases once again by the first part of
the next week as a cold front approaches from the western
Atlantic.

&&

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

Building surface high pressure north of the region will result in
breezy conditions across the regional waters and over portions of
the islands for the next few days. Upper level ridge will promote
fair weather conditions through the weekend. However, breezy
trades will continue to push remnants of and old front across the
region...resulting mainly in quick passing showers across the
islands. Under an east to northeast steering wind flow...the best
chance for afternoon shower development is across portions of the
interior and SW quadrant of Puerto Rico. Across the USVI, passing
showers and streamers are expected each day. Seasonal temperatures
are expected across the islands through the short term period.

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

...From previous discussion...

Sunday and Monday...expect another quick surge of northeast trade
wind moisture across the region increasing the chance for early
morning and afternoon showers. A cold front is forecast to move
across the west Atlantic and stall just northwest of the region by
Tuesday and Wednesday of next week, as the upper level ridge
erodes and moisture convergence and pooling increases once again
across the forecast area under a light to moderate southerly wind
flow. The potential for shower and thunderstorm development will
therefore increase by the middle of next week, followed by a
return of the easterly winds with lesser convective activity
forecast by the end of the work week.


&&

.AVIATION...VFR conditions at all TAF sites through the forecast
period with some mtn obscurations and -SHRA possible in and around
TJMZ through 07/22z. VCSH likely across the USVI terminals as well
as JSJ. ENE winds 10-15 knots with some sea breeze variations,
becoming at 10 knots or less after 07/22.


&&

.MARINE...Long period northeast swell will result in hazardous
seas across the regional waters through the end of the week. Small
craft advisories are in effect. Large breaking waves will result
in rough surf conditions and life threatening rip currents along
the north and east facing beaches of the islands through the
weekend. A gradual improvement is expected later on Sunday into
early next week. Moderate to fresh easterly winds will continue
through Saturday.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 76 87 74 87 / 10 20 20 20
STT 74 84 75 86 / 10 10 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
408 AM AST Fri Dec 8 2017

.SYNOPSIS...Building mid to upper level ridge aloft and strong
surface high pressure ridge across the central Atlantic will
promote dry and stable conditions and brisk east northeast trade
winds across the northeastern Caribbean through the weekend. The
upper ridge will erode by early next week as a polar trough and
associated cold front will enter and move across the western
Atlantic. By then the surface high will shift farther east and
relax the local pressure gradient resulting in light east to
southeast trade winds.

&&

.SHORT TERM...Today through Sunday...
Strong surface high pressure across the central Atlantic just to
the northeast of Puerto Rico will continue to push the frontal
boundary remnants southwards across the Caribbean waters and away
from the local islands. An upper level ridge over the region will
continue to promote relatively fair weather conditions across the
islands for the today and during the upcoming weekend. The surface
high pressure will also result in breezy conditions across the regional
waters and over portions of the islands for the next few days. Small
patches of low level moisture embedded in the breezy trades will move
across the region from time to time, resulting mainly in quick passing
showers across the islands. Under an east to northeast steering wind
flow...the best chance for afternoon shower development is across portions
of the interior and SW quadrant of Puerto Rico. However, not significant
or widespread precipitation is expected. Across the USVI, passing showers
are possible overnight and early in the morning with some streamers
expected to develop each afternoon. Seasonal temperatures are expected
across the islands through the short term period.

.LONG TERM...Monday through the end of the work week...
during the early part of the week,expect occasional quick surges
of northeast trade wind moisture across the region each day, increasing
the chance for early morning and afternoon showers. The activity is
so far forecast to be of short duration with no significant rainfall
accumulations. A cold front is still forecast to move across the
west Atlantic and stall just northwest of the region Tuesday through
Wednesday of next week. As the the upper level ridge erodes, moisture
convergence and pooling is forecast to increase once again across the
area under a light to moderate east to southeast wind flow. The potential
for shower and thunderstorm development will therefore increase by
the middle of the week, followed by a return of the easterly winds
with lesser convective activity forecast by the end of the work week.

&&

.AVIATION...Mostly VFR conditions expected across the local flying area
through the forecast period with some mountain obscurations and -SHRA
possible in and around TJMZ between 08/17Z-22Z. VCSH likely across
the USVI terminals as well as TJSJ. ENE winds at around 10 knots will
prevail until 08/14Z, increasing to 15-20 knots with higher gusts after
08/14Z.

&&

.MARINE...Hazardous seas and surf zone will continue, and Small
Craft and High Surf advisories are in effect for many of the local
waters and north coastal beaches. There is also a high risk of rip
currents across many of the local beaches. Please refer to the
local marine and surf zone forecast products for the details in
your area.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 74 87 75 / 20 20 20 50
STT 86 75 86 75 / 10 20 20 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
447 PM AST Fri Dec 8 2017

.SYNOPSIS...A mid to upper level ridge and a strong surface high
pressure ridge across the central Atlantic will promote dry and
stable conditions and brisk east northeast trade winds across the
northeastern Caribbean through at least Saturday. By early next
week a deep polar trough and associated frontal boundary will move
close the forecast area from the northwest. The surface ridge will
shift further into the northeastern Atlantic and as the frontal
boundary moves over the area the winds will relax and moisture
pooling will increase across the region.


&&

.SHORT TERM...Tonight through Tuesday...
From the surface to 700 mb low pressure in the northeast central
Atlantic will drop south and open into a trough late Saturday. A
surface high pressure almost 1000 miles northeast of San Juan will
retreat northeast into the central Atlantic ocean allowing pressure
gradients to relax considerably later Saturday and Sunday. Winds at
the surface will become more northeasterly since the trough will
approach the area early next week. The trough will become less
defined as it arrives but should cross the area on Tuesday.

As the high retreats and the trough approaches, bands of moisture in
the northeast flow will move through the area bringing scattered
light showers to the windward slopes and plains of Puerto Rico and
to a lesser degree to the U.S. Virgin Islands. On Sunday night and
Monday the instability in the cool flow will be enhanced by
increasing moisture as the precipitable water increases from a low
of around three quarters of and inch Sunday morning (10/12Z) to over
one and one half inches Sunday night (11/06Z). Owing to the shallow
and patchy nature of the moisture, however, only minor accumulations
are expected Sunday and Monday mornings and Monday and Tuesday
afternoons in southwest Puerto Rico. Fringes of the moisture ahead
of an approaching cold front will be first be seen late Tuesday
night at mid levels in the northwest corner of the forecast area.

Flow aloft will remain north or northwest through the period
although the crest of a weakening ridge will pass through Monday
night. A trough passing north of the area will not break through the
ridge and the jet beneath the trough will remain at least 750 miles
to our northwest and north as it passes. Therefore little help for
showers will be had from the upper atmosphere.

.LONG TERM...Tuesday through Saturday...From previous
discussion...
During the early part of the week, expect occasional quick surges
of northeast trade wind moisture across the region each day,
increasing the chance for early morning and afternoon showers. The
activity forecast to be of short duration with no significant
rainfall accumulations. A cold front is still forecast to move
across the west Atlantic and stall just northwest of the region
Tuesday through Wednesday of next week. As the the upper level
ridge erodes, moisture convergence and pooling is forecast to
increase once again across the area under a light to moderate east
to southeast wind flow. The potential for shower and thunderstorm
development will therefore increase by the middle of the week,
followed by a return of the easterly winds with less convective
activity forecast by the end of the work week.

&&

.AVIATION....Aviation...Mostly VFR conditions expected across the local
flying area through the forecast period with some mountain
obscurations and SHRA possible in and around TJMZ TIL 08/22Z.
Local winds east 10 to 15 kt with gusts to 25 kt psbl subsiding to
5 to 12kt with weak land breeze variations. Maximum winds WNW-NW
40 kt FL400-500 diminishing aft 09/12Z.


&&

.MARINE...Hazardous seas between 7-9 feet and up to 11 feet are
expected to continue for the next couple of days as the
northeasterly swell continues to spread across the Atlantic
waters and passages. This swell will continue to create large
breaking waves and life threatening rip currents across the north
and east facing beaches of the islands. Breezy easterlies will
continue between 15-20 kts with some higher gusts at times.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 74 87 75 86 / 20 20 50 20
STT 75 86 75 86 / 20 20 50 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
409 AM AST Sat Dec 9 2017

.SYNOPSIS...A mid to upper level ridge over the region in
combination with a strong surface high pressure across the
central Atlantic will continue to promote a dry and stable
weather pattern and a brisk east northeast trade winds across the
northeastern Caribbean through at least Sunday. By early next
week a deep polar trough and associated frontal boundary will move
across Cuba, Hispaniola and southern Bahamas from the northwest.
As the frontal boundary approaches to the region from the
northwest, the surface high pressure will shift to the northeast,
winds will relax and moisture pooling will increase across the
local islands.

&&

.SHORT TERM...Today through Monday...
Surface high pressure ridge will continue to lift east northeast
and weaken through Monday as a cold front will move across the
western Atlantic. Mid to upper level ridge will also gradually
erode through Monday as a broad polar trough moves eastwards
across the west and central Atlantic. The local pattern will favor
moderate to locally strong east northeast trade winds through at
least Sunday then become more northeasterly by Monday, as a
surface trough develops across the tropical Atlantic and
northeastern Caribbean and the cold front stalls northwest of the
region.

In the meantime expected periods of quick passing shallow low level
clouds with early morning trade wind showers across the coastal
waters and mainly east and north coastal sections of the islands.
For today mostly fair weather skies expected with limited shower
activity due to overall stable conditions. However, by Sunday and
Monday expect an increase in the northeasterly trade winds which
will lead to better change for showery conditions along the north
and east coastal areas during the evening and early morning hours.
Any afternoon shower activity will then be focused over the central
and southwest sections of Puerto Rico and mainly downwind of the
U.S. Virgin Islands.

.LONG TERM...Tuesday through Saturday...
A cold front is still forecast to move across the west Atlantic
and stall just northwest of the region Tuesday through at least
Thursday. As the boundary approaches the upper level ridge is
expected to erode, increasing the moisture across the local
islands and surrounding waters under a light to moderate east to
east-southeast wind flow. This will increase the chances for
early morning and afternoon showers. However, this activity is
forecast to be of short duration with no significant rainfall
accumulations. The potential for shower will decrease by the end
of the work week with a return to easterly winds. However, small
patches of moisture embedded in the trades will bring brief
periods of showers across the region during the upcoming weekend.

&&

.AVIATION...VFR expected across the local flying area durg the fcst
prd. SCT ocnl BKN cld lyrs nr FL025...FL040. Few Tops nr FL120 in
passing SHRA. Wnds fm E 15-20 kts blo FL200...bcmg fm N and incr
w/ht ABV. Sfc wnd fm E-SE 5-10 kts bcmg 15-20kts aft 09/14z.


&&

.MARINE...Hazardous seas up to 10 feet are expected to continue
for the next couple of days as the northeasterly swell continues
to spread across the Atlantic waters and passages. This swell will
continue to create large breaking waves and life threatening rip
currents across the north and east facing beaches of the islands.
Breezy easterlies will continue between 15-20 kts with some higher
gusts at times.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 87 75 / 20 50 20 30
STT 85 75 86 75 / 20 50 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
400 PM AST Sat Dec 9 2017

.SYNOPSIS...Fair weather will continue through the rest of the
weekend as ridge pattern will hold through Monday. This pattern
will keep the atmosphere fairly stable over the next few days.
Although a few trade wind showers will reach the local islands
from time to time...light rainfall accumulations are expected
across through at least Tuesday.

&&

.SHORT TERM...Rest of today through Monday...Surface high pressure
over the North Central Atlantic will maintain breezy conditions
across the region through Sunday. Mid level ridge will suppress
the development of heavy rain across Puerto Rico and the U.S.
Virgin Islands over the next few days. Although...light passing
showers can`t ruled out as brisk trade winds will push clouds and
showers over the islands at times.

Winds will subside as a frontal boundary moves closer to the
Northeast Caribbean early next week. As the winds decrease and
the ridge aloft weakens...a minor enhancement in the shower
activity is possible especially during the afternoon when diurnal
showers develop over western Puerto Rico.

.LONG TERM...Tuesday through Saturday...
A cold front is still forecast to move across the west Atlantic
and stall just northwest of the region Tuesday through at least
Thursday. As the boundary approaches the upper level ridge is
expected to erode, increasing the moisture across the local
islands and surrounding waters under a light to moderate east to
east-southeast wind flow. This will increase the chances for
early morning and afternoon showers. However, this activity is
forecast to be of short duration with no significant rainfall
accumulations. The potential for shower will decrease by the end
of the work week with a return to easterly winds. However, small
patches of moisture embedded in the trades will bring brief
periods of showers across the region during the upcoming weekend.

&&

.AVIATION...VFR conds expected through the forecast period. Winds
from the east to continue at 15-20 kt decreasing to around 10-15
kt tonight. Similar pattern is expected on Sunday, VFR conds and
easterly winds around 15 kt.

&&

.MARINE...Small craft advisories are still in effect. There is a
high risk of rip currents across many of the local beaches, mainly
on the northern side of the islands with some areas of the western
and eastern coasts. The local buoys confirm hazardous seas near
our coasts. Therefore, the High Surf Advisory has been extended
through 10 PM tonight. Marine conditions will gradually improve
after Sunday afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 87 75 84 / 20 20 40 40
STT 75 86 75 84 / 30 20 40 40

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
438 AM AST Sun Dec 10 2017

.SYNOPSIS...Relatively dry air expected to continue today, causing
mainly fair weather across the local islands. Ridge in the upper
levels will keep a stable atmosphere and any showers that do
affect the islands should be brief with minimal accumulations.
Winds are starting to diminish today.

&&

.SHORT TERM...TODAY THROUGH TUESDAY...
Surface high pressure ridge will continue to lift north of the area
and weaken through Monday as a cold front moves across the west
Atlantic and a surface trough develops across the northeastern
caribbean. The mid to upper level ridge will also erode through
Tuesday as a broad polar trough moves eastwards across the western
Atlantic. This unfolding pattern will favor a loosening of the local
pressure gradient resulting in light to moderate northeasterly trade
winds by Monday, as the trough develops across the tropical Atlantic
and the cold front stalls northwest of the region.

For today periods of quick passing shallow low level clouds with
embedded showers will continue to affect the coastal waters and the
windward side of the islands through the morning hours. Mostly fair
weather skies expected during the rest of the day with limited
shower activity focused mainly over parts of the central interior
and southwest sections of PR during the afternoon. Late tonight
through Monday, the arrival of a surface through will bring a surge
of moisture in the northeasterly trades. This will lead to increased
potential for showery conditions along the north and east coastal
areas during the overnight and early morning hours. Afternoon shower
activity will then be focused over the central and southwest
sections of Puerto Rico and mainly downwind of the U.S. Virgin
Islands. Drier conditions and mostly fair weather skies are forecast
for Tuesday...except for some diurnally induced afternoon showers
in isolated areas.

.LONG TERM...WEDNESDAY THROUGH MONDAY...

Strong surface high pressure across the northeastern Atlantic will
promote easterly winds to the local islands, although somewhat
light winds on Wednesday and Thursday with patches of moisture
over the area. Then later in the week, another surface high
pressure moves north of the local area, tightening the pressure
gradient and causing breezy conditions for the upcoming weekend.
Given the patches of moisture expected, there many be some brief
showers in the windward side of the islands. The upper levels do
not appear to cause any instability for thunderstorm development.

&&

.AVIATION...VFR conds expected durg the prd. SCT-BKN cld lyrs nr
FL025...FL050 btw PR and the northern Leeward islands transported by
the prevailing easterlies. Winds cont fm E at 15 to 20 kt blo
FL250...bcmg fm N and incr w/ht ABV. Sfc wnds lgt/vrb except for
brief gusts 15-20kt with passing SHRA...incr to 10-15 KTS aft
10/14Z. Brief Mtn top obscr til 10/12z ovr E PR due to passing
SHRA/Low clds. Otherwise no sig AVN hazards anticipated attm.

&&

.MARINE...Seas will start to subside today, but there is still a
small craft advisory for many of the local waters. There is also a
high risk of rip currents for the northern beaches of Puerto Rico,
Vieques, Culebra, Saint Thomas and Saint Croix. Please refer to
the local marine products for area-specific details.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 75 85 73 / 20 40 40 30
STT 86 75 85 74 / 20 40 40 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
313 PM AST Sun Dec 10 2017

.SHORT TERM...

A cold front will be pushing into the windward passage tonight and
Monday and into Hispaniola by Wednesday. Wednesday night will
represent the farthest progress that the front will make this week.
An approaching long wave trough leaving Florida will push a
weakening ridge over the local area Monday night. The ridge will
stall just east of the area however holding the activity from the
jet and the associated frontal zone well northwest. Moisture will
increase from around 1.1 inch to around 1.4 inches on Wednesday--but
this is still fairly limited.

.LONG TERM...
Strong surface high pressure across the northeastern Atlantic will
promote easterly winds to the local islands, although somewhat
light winds on Wednesday and Thursday with patches of moisture
over the area. Then later in the week, another surface high
pressure moves north of the local area, tightening the pressure
gradient and causing breezy conditions for the upcoming weekend.
Given the patches of moisture expected, there many be some brief
showers in the windward side of the islands. The upper levels do
not appear to cause any instability for thunderstorm development.

&&

.AVIATION...VFR conditions to continue til 10/22Z except for brief
cigs vcnty TKPK and TJMZ near -SHRA and ovr SE PR. SHRA ending ovr
PR by 11/00Z but chc of SHRA along NE coast of PR and nrn USVI aft
11/06Z. Maximum winds 30-40kt btwn FL400-510 til byd 11/18Z.


&&

.MARINE...Winds are diminishing and seas are expected to also
continue falling. Rip current risk should be below high everywhere
by Monday and small craft advisories come down at 2 PM AST today.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 77 85 74 85 / 30 30 30 30
STT 78 85 78 84 / 30 30 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
432 AM AST Mon Dec 11 2017

.SYNOPSIS...Upper level ridge will maintain a relatively stable
weather pattern across the region for the next couple of days.
Only brief showers with minimal rainfall accumulations are
possible. Not significant changes in the present weather pattern
are expected for the next several days.

&&

.SHORT TERM...Today through Wednesday...
A patch of moisture across the eastern sections of the Forecast Area
is causing showers over the USVI, Vieques, Culebra and the eastern
sections of PR. This small area of higher moisture is expected to
remain in the area through the morning hours and then move west and
slightly south, which will bring enhanced moisture to southern and
southwestern Puerto Rico by the afternoon hours. For this reason,
the forecast was adjusted to increase the probability of rain across
southern into western PR in the afternoon as well as some showers
that may stream off the local islands. Because the upper levels are
pretty stable, no thunderstorm development is expected today.
Isolated to locally scattered but brief showers are expected tonight
as the patch of moisture leaves the area.

Mainly isolated to scattered showers are expected again on Tuesday
and Wednesday as the local winds diminish and bringing moisture from
the south. There is a surface high pressure across the NE Atlantic
and a strong SFC low pressure across the NE-US that will cause a COL
over the local area. Because of this the local winds will diminish
and the showers over the local area will be greatly influenced by
the local factors. So expect scattered showers across various sectors
of the forecast area but mainly across the interior of PR.

.LONG TERM...Thursday through Tuesday...
An upper level ridge is expected to build across the northeast
Thursday through the upcoming weekend. This feature is expected to
maintain a relatively stable weather pattern across the local
islands during the forecast period. A dissipating frontal
boundary/shear line is expected to remain across the Atlantic
waters to the northwest and north of the local islands Thursday
and Friday. Strong surface high pressure across the northeastern
Atlantic will promote an east to east-northeast winds across the
local islands Thursday and until at least Saturday. Another
surface high pressure is expected to move just north of the local
area late in the upcoming weekend, tightening the pressure
gradient and causing breezy conditions early during the upcoming
week. Small patches of moisture embedded in the trades will bring
brief periods of showers across the windward side of the islands
especially during the nights and early in the mornings. However,
the upper level ridge over the region will inhibit the development
of widespread or significant precipitation during the forecast
period.

&&

.AVIATION...VFR conds expected across the local terminals for the
next 24 hours. Brief SHRA over the local area will cause VCSH across
TIST/TISX and TJSJ at least through the morning hours with possible
but brief moments of MVFR conds with the heaviest SHRA. Afternoon
SHRA may cause VCSH for TJPS and TJMZ. Winds from the east to NE at
10 to 15KT.

&&

.MARINE...Winds and seas will continue to diminish today. There is
a moderate risk of rip current for the northwest to northeast
beaches of Puerto Rico, Vieques, Culebra and for most beaches of
Saint Thomas, Saint John and Saint Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 74 86 76 / 30 30 30 20
STT 86 74 85 75 / 30 20 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
352 PM AST Mon Dec 11 2017


.SYNOPSIS...
The local weather conditions will be dominated by an upper level
ridge. Shower activity if any, will be wind driven due to patches
of low level moisture across the regional waters. Then, a
southerly wind flow is expected to result in afternoon showers
along and to the north of the Cordillera on Tuesday.

&&

.SHORT TERM...Tonight through Thursday...
The upper level ridge over Hispaniola will slowly weaken during
the next 3 days but will not cross PR and the U.S. Virgin Islands
definitively until Wednesday. Moisture at mid levels remains weak
through the period even though precipitable water climbs from a
minimum of 1.1 inches at 12/12Z to 1.54 inches at 14/00Z. But the
overall deciding factor in who gets rain appears to be the lower
level winds which will shift with an approaching trof, to pass the
Leeward Islands Tuesday morning and Puerto Rico shortly
thereafter after a brief passage of drier air. This will cause low
level winds to veer from easterly tonight to almost southerly
early Wednesday. Winds will be light however on Wednesday and some
sea breezes should be able to break through on the north side to
moderate what would ordinarily be a rather warm day for the north
coast of Puerto Rico. Nevertheless increasing moisture and light
winds bode well for showers, albeit shallow, over the interior of
Puerto Rico Wednesday. The cold front, now over eastern Cuba,
becomes tenuous in its advance toward the area and does not
advance beyond the highlands of the Dominican Republic which it
reaches by Wednesday night. Showers on Wednesday and Thursday will
occur mainly due to weak pre-frontal trough that tries to form
over and east of the area. For the U.S. Virgin islands, the
southerly winds on Wednesday will bring up a little moisture and
slightly warmer temperatures, but will not have as strong effect
as for Puerto Rico.

.LONG TERM...Thursday through Tuesday...
An upper level ridge is expected to build across the northeast
Thursday through the upcoming weekend. This feature is expected to
maintain a relatively stable weather pattern across the local
islands during the forecast period. A dissipating frontal
boundary/shear line is expected to remain across the Atlantic
waters to the northwest and north of the local islands Thursday
and Friday. Strong surface high pressure across the northeastern
Atlantic will promote an east to east-northeast winds across the
local islands Thursday and until at least Saturday. Another
surface high pressure is expected to move just north of the local
area late in the upcoming weekend, tightening the pressure
gradient and causing breezy conditions early during the upcoming
week. Small patches of moisture embedded in the trades will bring
brief periods of showers across the windward side of the islands
especially during the nights and early in the mornings. However,
the upper level ridge over the region will inhibit the development
of widespread or significant precipitation during the forecast
period.

&&

.AVIATION...
Isold SHRA ovr Atlantic waters movg SW into PR with brief MVFR
due to CIGS. Areas of mtn obscurations in Cordillera Central til
12/02Z. A patch of moisture will bring sct SHRA to TJSJ/TIST/TISX
btwn 12/04-10Z where brief will be MVFR psbl. For the Leeward
islands CIGS mainly abv FL030 but moisture patch btwn 11/20-12/01
to bring CIGS arnd TKPK to 018-024. SHRA aft 11/06Z should remain
south of TNCM. Apchg trof to shift winds to SE TNCM/TKPK aft
12/12Z. Maximum winds northwesterly 30-40 kt btwn FL350-470 til
11/12z.

&&

.MARINE...
Seas will continue to subside across the region waters. In
general, mariners can expect seas between 3 and 5 feet across the
Atlantic Waters and Anegada Passage, and between 1 and 4 feet
across the Caribbean Waters. A northerly swell is expected to
arrive by the end of the work-week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 74 86 76 86 / 20 30 10 30
STT 74 85 75 84 / 20 10 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
408 AM AST Tue Dec 12 2017

.SYNOPSIS...Surface high pressure across the northeastern Atlantic
and Low pressure over the northwestern Atlantic will keep the
local islands with lighter winds today until Thursday with the
winds having a southerly component and increasing moisture.
Frontal boundary will stall to the west of the local islands.


&&

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

Mostly clear skies and a few passing showers were observed across
the forecast area overnight and early this morning. Minimum
temperatures were in the low to mid 70s across the lower elevations
and in the 60s across the higher elevations. Winds were light and
variable.

A surface front to the west and a surface high to the east will
yield a light southerly wind flow today and Wed. As the front
dissipates, the surface high will then spread across the area on
Thursday to result in easterly winds at around 15 knots. Latest
guidance continues to suggest a building ridge aloft with
precipitable water values below or near the normal range.

Under the aforementioned pattern, still expect a mainly fair weather
pattern with trade wind showers at times as well as locally induced
showers due to sea breeze convergence each afternoon. Afternoon
showers will be focused across the Cordillera Central, the northwest
quadrant as well as portions of the San Juan Metro area today and
Wednesday, shifting the the western interior and western Puerto Rico
Thursday afternoon.

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

By Friday, the local winds are expected to have started
strengthening once again as the local pressure gradient tightens,
causing breezy conditions through the weekend and into early next
week. The available moisture is expected to be near normal with
patches of higher or lower moisture, which is rather typical for
the time of year. This pattern will likely cause brief passing
showers across the local area, mainly affecting the windward side
of Puerto Rico and also briefly affecting the local islands.
Typically these showers do not cause significant flooding since
they are normally brief and light to moderate. There is also high
pressure in the upper levels for late this week with an upper
trough moving in from the east by early next week, either way this
pattern should cause subsidence since even with the approaching
trough from the east, we would be in the subsident side of the
trough. Therefore no more than the aforementioned brief showers
are expected for the latter part of this week into early next
week. Having said this, remember that this is late into the
forecast period and confidence in the models is low, but moderate
overall after accounting for climatology.

&&

.AVIATION...VFR conditions are expected to prevail at all TAF sites
through the forecast period with some mtn obscurations and brief
SHRA possible in and around TJBQ/TJMZ/TJSJ between 18z and 22z.
VCSH elsewhere. A light southerly wind flow is expected to prevail
with some sea breeze variations.

&&

.MARINE...Seas will be generally 5 feet or less with winds from
the east to southeast at 5 to 15 knots. There is a moderate risk
of rip currents for the beaches of northern PR as well as some
beaches in Vieques and Culebra. For the USVI, north and eastern St
Croix and NW Saint Thomas also have a moderate risk of rip
currents.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 75 86 76 / 30 10 30 20
STT 85 76 85 75 / 10 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
404 AM AST Wed Dec 13 2017

.SYNOPSIS...Surface high pressure across the east-central
Atlantic and Low pressure over the northwestern Atlantic will
continue to cause light southerly winds today and possibly until
Thursday while moisture also increases. Frontal boundary will
continue stalled to the west of the local islands until Thursday,
before it starts to dissipate late Thursday. Local pattern will
likely cause isolated to scattered showers across portions of the
local forecast area.

&&

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

Mostly clear skies and a few passing showers were observed across
the forecast area overnight and early this morning. Minimum
temperatures were in the low to mid 70s across the lower elevations
and in the 60s across the higher elevations. Winds were light and
variable.

A surface front will continue to stall west of the forecast area
while it dissipates. The surface front to the west and a surface
high across the central Atlantic will continue to yield a light
south southeast wind flow through at least Thursday. As the surface
front dissipates, the surface high will then spread across the area,
tightening the local pressure gradient. Therefore, moderate easterly
winds are expected to return on Friday. At upper levels, a ridge
pattern will continue to slowly build, resulting in erosion of low
level moisture on Friday. Meanwhile, latest guidance continues to
indicate precipitable water values near the normal range through
Thursday under the south southeast wind flow. As a result, still
expect a mainly fair weather pattern with trade wind showers at
times as well as locally induced showers due to sea breeze
convergence across the northwest quadrant of the island today and
Thursday. Limited shower activity is expected Friday.

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

Upper level ridge will continue over the local islands through the
weekend, then an upper trough moves near the eastern Caribbean but
stays to our east, which means that we will stay in the subsident
side of the trough, inhibiting thunderstorm development over the
local area for early next week. The local pressure gradient is
expected to tighten this upcoming weekend into next week as a
surface high pressure moves north of the local islands. This setup
will cause a breezy easterly wind flow from Saturday into at least
Wednesday, winds decreasing a little thereafter. The available
moisture will be near normal with patched of higher moisture
moving in, causing a brief increase in shower activity over the
local area. Overall a seasonable pattern is expected in the
extended forecast. Temperatures also are expected to be seasonable
with highs in the low to mid 80s across the lower elevations and
in the 70s across the higher elevations, lows in the low to mid
70s across the lower elevations and in the 60s across the higher
elevations...some isolated areas possibly slightly cooler.


&&

.AVIATION...VFR conditions are expected to prevail at all TAF sites
through the forecast period with some mtn obscurations and brief
SHRA possible in and around TJBQ/TJMZ/TJSJ between 18z and 22z.
VCSH elsewhere. A light southerly wind flow is expected to prevail
with some sea breeze variations.


&&

.MARINE...Relatively tranquil marine conditions are expected until
the arrival of a northerly swell late Thursday. Seas will be up
at 5 feet today and Thursday during the day, as the northerly
swell moves in late Thursday into early Friday, the local seas
will increase up to 6 feet through Saturday then 7 feet or higher
on Sunday and into early next week.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 74 86 75 / 10 20 30 30
STT 83 75 85 74 / 20 40 40 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
423 PM AST Wed Dec 13 2017

.SYNOPSIS...Surface high pressure across the east central Atlantic and
frontal boundary northwest of the region, will maintain light east
to southeast winds across the local region overnight through Thursday.
By late Thursday and into the upcoming weekend, a high pressure ridge
will build and spread across the western Atlantic to tighten the local
pressure gradient resulting in increasing east to northeast trade winds.
Mid to upper level high pressure ridge will remain in place across the
region for the next several days.

&&

.SHORT TERM...Rest of today through Saturday...
A few clouds and light to moderate showers developed across parts
of the interior and southern slopes of Puerto Rico during the
afternoon and mainly over the coastal waters around parts of the
U.S. Virgin Islands. No significant rainfall accumulations were
however noted across the entire region as mostly fair weather
skies and sunny conditions prevailed across the forecast area.

A weakening cold front and associated frontal boundary northwest of
the forecast area will continue to stall and dissipate well north
of the region over the next several days. This will maintain light
southeasterly winds through Thursday. As the frontal boundary dissipates,
surface high pressure will build and spread across the west Atlantic,
tightening the local pressure gradient beginning on Friday. Moderate
east to northeast winds can be then be expected from then on and through
the weekend. The mid to upper level a ridge pattern will hold across
the region through the rest of the week, resulting in limited moisture
advection and shower development through the end of the week and into
the weekend. A few early morning passing showers may however reach
the coastal areas followed by limited afternoon convection each day.

.LONG TERM...Sunday through Thursday...
Upper level ridge will continue across the forecast area through
the weekend, but will slightly erode by early next week as a short
wave trough is forecast to develop and move north and east of the
region. The local region is however forecast to remain on the
west/subsident side of the upper trough, therefore limiting
convective development through early next week.

The local pressure gradient is expected to tighten by Sunday as a
surface high pressure moves north of region. This setup will cause
a increasing east to northeast winds through at least the middle of
next week. The increasing northeasterly wind flow will also increase
the chance for early morning passing showers mainly along the north
and east coastal sections each day. For the rest of the day and during
the afternoon hours, an overall seasonal and cool weather pattern can
be expected during the rest of the forecast period with mostly sunny
skies and limited shower activity each day.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals. Passing -SHRA could briefly affect the USVI/Eastern
portions of PR through the overnight/early morning hours. Low level
winds will be east-southeast at 5-15 kts. No sig AVN wx impacts
attm.

&&

.MARINE...Near shore buoys continued to suggest seas between 2-4
feet and light southerly winds up to 10 knots. No major change is
expected on the marine conditions until late Thursday into Friday
when a long period north-northwest swell arrives to the local atlantic
waters and passages.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 86 75 85 / 20 30 30 20
STT 75 85 74 85 / 30 30 30 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
430 AM AST Thu Dec 14 2017

.SYNOPSIS...A surface front will continue to stall west of the
area while it dissipates. As the surface front dissipates, the
surface high across the central Atlantic will spread across the
area tightening the local pressure gradient. At upper levels,
ridge will continue to build and hold through much of the upcoming
week. A fair weather pattern with a few passing showers at times
is expected to prevail across the local islands during the next
few days.

&&

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

Surface high pressure across the east central Atlantic will begin to
spread westward, causing the easterly winds that we expect today and
Friday, becoming ENE on Saturday before a SFC high pressure moves
north of the local islands late Saturday, starting to tighten the
pressure gradient and causing breezy conditions late in the weekend
with an ENE wind flow by Sunday.

For today, isolated showers expected across the local waters, the
USVI, and eastern PR, leaving minimal accumulations if any. The
available moisture will be below normal today but the local effects
may help in the development of scattered showers across the
northwestern quadrant of PR this afternoon. Even drier air is
expected overnight tonight into Friday and even less shower activity
is expected on Friday as the precipitable water values could be as
low as one inch or below at times, which is near 2 standard
deviations lower than normal. By late Friday the winds are expected
to start shifting to a ENE direction. A patch of moisture expected
to approach the islands on Saturday but the lack of upper level
support will likely result only in scattered showers across the area
on Saturday. An upper ridge is expected to be over the local islands
on Saturday with a trough to our east, which is not particularly
conducive for prolonged shower activity, but scattered passing
showers are expected across the local forecast area.

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

A mid to upper level ridge will hold across the forecast area
through at least midweek next week. The ridge pattern aloft is then
expected to erode Thu-Fri as an upper trough establishes across
the tropical Atlantic and into the eastern Caribbean. At lower
levels, high pressure north of the area will prevail much of the
forecast period resulting in a moderate east northeast wind flow.
With the ridge pattern from surface through the upper levels,
expect a fair and mainly stable weather pattern across the local
islands much of the upcoming week with a few passing showers
possible. Seasonable temperatures are also expected under the
east northeast wind flow.

&&

.AVIATION...Prevailing VFR conditions expected for the next 24 hours
across the local terminals. Isold/Sct SHRA through the day may cause
VCSH. However, SHRA is expected across NW-PR after 14/16Z, which may
affect TJBQ and the vicinity of TJMZ, possibly causing brief MVFR
conds at TJBQ. Winds will be generally from the east today at around
10KT with sea breeze variations.

&&

.MARINE...Seas will be 3 to 5 feet during the day, increasing
tonight as a northerly swell moves in. The local seas will
increase up to 6 feet through Saturday then 7 feet or higher on
Sunday and into early next week. There is a moderate risk of rip
currents throughout the day becoming high tonight.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 76 86 76 / 30 30 20 20
STT 86 75 86 76 / 30 30 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
433 PM AST Thu Dec 14 2017

.SYNOPSIS....Fair weather and mostly sunny conditions prevailed across
the entire region as high pressure and an overall dry and stable airmass
dominated the region. Limited or no shower activity was observed or
reported across the forecast area under a light easterly wind flow.

&&

.SHORT TERM...Rest of today through Saturday...
Mostly fair and stable season weather conditions are forecast to
prevail through Friday and into the weekend as mid to high level
ridge will remain in place and suppress/limit any convective development.
In addition...limited moisture advection is expected with under
the light to moderate easterly trade winds. Therefore, expect plenty
of sunshine and pleasant daytime and overnight temperatures during
the next few days. A few light passing showers will however remain
possible during the overnight and early morning hours followed by
limited shower activity during the daytime.

.LONG TERM...Sunday through Friday...
No significant changes to the recent model guidance which
continued to suggest mostly fair weather skies to prevail during
the entire period. A mid to upper level ridge will hold across the
area through at least Wednesday of next week. The ridge pattern
aloft is then expected to erode by the end of the work week as an
upper trough establishes across the tropical Atlantic and sinks
southwards into the eastern Caribbean. At lower levels, high pressure
north of the area will prevail much of the forecast period resulting
in a moderate east northeast wind flow. With the dominant ridge pattern
to persist expect a fair and mainly stable weather pattern across the
local region during much of the upcoming week. However, the moderate
northeasterly trade winds will bring periods of shallow clouds and passing
showers to the north and east coastal sections mainly during the morning
hours. Seasonable temperatures are also expected to continue under the
east to northeast wind flow.

&&

.AVIATION...VFR conditions will prevail through the forecast period.
Brief SHRA over western PR could affect the flying area of JMZ/JBQ.
Surface winds will continue between 10-15 kts with lighter land
breeze variations overnight.

&&

.MARINE...Buoys across the coastal waters continued to suggest seas
up to 4 feet offshore and 1 to 3 feet near shore, with easterly winds
of 10 to 15 knots. Small crafts should exercise caution tonight as
seas up to 6 feet are expected across the Atlantic waters and local
passages. Small craft advisory will be in effect for the offshore
Atlantic by early Friday due to increasing winds and seas. A long
period northwest swell will reach the local waters overnight and
will result in a high risk of rip currents along the Atlantic coast
of Puerto Rico and Culebra.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
440 AM AST Fri Dec 15 2017

.SYNOPSIS...A mid to upper level ridge will hold across the
forecast area through at least midweek next week. A surface
high across the east central Atlantic will yield east northeast
winds through the weekend. Mainly fair and stable weather
conditions are expected to prevail during the next few days.

&&

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

The local weather conditions are dominated by a strong ridge
pattern, which favors a trade wind cap across the islands. GFS
forecast soundings are indicating a relative dry air mass through
the weekend, with below normal TPW values for the month of December.
Limited moisture advection will continue with light to moderate
easterly trade winds. Therefore, expect mostly sunny skies with a
few passing clouds and pleasant daytime and overnight temperatures
during the next few days. However, a few light passing showers
will remain possible during the overnight and early morning hours
followed by limited shower activity during the afternoon.

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

A mid to upper level ridge will hold across the forecast area
through at least midweek next week. The ridge pattern aloft is
then expected to erode by the end of the upcoming week as a broad
trough establishes across the central Atlantic and into the
eastern Caribbean. At lower levels, migratory surface highs north
of the area will prevail much of the forecast period, resulting in
a moderate to fresh east northeast wind flow. Under a ridge
pattern aloft, expect a fair and mainly stable weather pattern
across the local islands much of the upcoming week with a few
passing showers possible. Seasonable temperatures are also expected.
Low level moisture is then expected to increase as the ridge
aloft collapses by the end of the forecast period to result in a
better chance for shower activity across the local islands.

&&

.AVIATION...VFR conditions will prevail through the forecast period.
Brief SHRA along and to the west of the Cordillera Central could
affect the flying area of JMZ/JPS btwn 15/19-22z. Surface winds will
continue light to calm and variable but increasing between 10 and 15
kts after 15/12z.
&&

.MARINE...A northerly swell will continue to spread across the
Atlantic waters and local passages throughout the day. Seas up
to 7 feet are expected mainly across the offshore waters.Elsewhere,
seas between 3 and 6 feet. A high pressure ridge will build and
spread across the forecast area, tightening the local pressure
gradient. This will result in a moderate to fresh east to northeast
wind flow during the next several days. There is also a high risk
of rip currents along the north facing beaches of the local
islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 76 85 77 / 10 20 30 20
STT 86 76 86 75 / 10 20 30 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
445 PM AST Fri Dec 15 2017

.SYNOPSIS...A mid to upper level ridge will hold across the forecast
area through the weekend and into early next week. Surface high pressure
ridge will continue to build and spread across the east central Atlantic
yielding moderate to strong east to northeast winds through the weekend.
Mostly fair weather skies and seasonal condtions expected to persist
for the next several days.

&&

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

The dominant high pressure ridge pattern, will continue to favor
a strong trade wind cap inversion across the region supporting
mostly fair weather skies across the islands. Model guidance,
satellite imagery and recent upper air sounding continued to suggest
a relatively dry and stable air mass to persist through Sunday.
In addition moisture advection will be limited except for that
brought in across the north and east coastal areas by the moderate
to strong east northeast trades. Expect plenty of sunshine and
few passing clouds with pleasant daytime and overnight temperatures
during the next few days. Occasional light passing showers will remain
possible during the overnight and early morning hours followed by
limited shower activity during the afternoons.

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

A mid to upper level ridge will hold across the forecast area through
at least Wednesday. The ridge pattern aloft is then expected to gradually
erode during the latter part of next week, as a polar trough will move
across the central Atlantic then sink southwards into the northeastern
Caribbean. The surface high pressure ridge pattern north of the region
is forecast to persist through the forecast period. This will result
in moderate to strong east northeast winds. Expect a fair and mainly
stable weather pattern across the islands and coastal waters through
most of next week, except for passing showers especially during the
early morning and late evening hours. Seasonable temperatures are
expected to continue. By the end of the period low level moisture
is forecast to gradually increase as the ridge aloft erodes in response
to an upper trough sinking southwards across the region. This will
result in a better chance for shower activity across the local islands.
Widespread and significant rainfall accumulations as not forecast
at this time.

&&

.AVIATION...VFR conditions will prevail across all terminals through
the forecast period. Afternoon SHRA over the SW quadrant of PR could
affect briefly TJPS/TJMZ. Winds will continue ENE at 10-15 kts with
higher gusts at times.

&&

.MARINE... A north swell between 4-6 feet will continue to affect
the Atlantic waters and passages overnight. This will result in a
high risk of rip currents across the Atlantic beaches of Puerto
Rico, Culebra and St. Thomas. Moderate to fresh east to northeast
winds will continue at 10-15 knots with higher gusts at times increasing
to 15 to 20 knots over the weekend. Small craft advisory will remain
in effect overnight through Saturday for the offshore Atlantic waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 76 85 77 84 / 20 20 30 30
STT 76 86 75 87 / 20 30 30 30