Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
521 AM AST Sun Dec 2 2018

.SYNOPSIS...The remnants of an old frontal boundary will bring
fragments of low level clouds and passing showers through early
next week. A mid level ridge will continue over the western
Caribbean through Tuesday. Another front is forecast to remain
north of the area and another mid level ridge is expected to build
from the western Caribbean during the second part of the week.


&&

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

A weak upper level trough passed through overnight from the west
northwest. A weak high was over Jamaica. Upper level flow over the
area will quickly become northwesterly. High pressure at mid levels
will dominate the local area with the main center being over the
western Caribbean. This will keep the mid levels almost completely
dry.

High pressure at the surface, north of Puerto Rico, at 29 degrees
north and another southeast of Nova Scotia will join over the
western Atlantic today, and move east into the central Atlantic
Tuesday. An old frontal band, near 21.5 north, is now showing signs
of stalling for the next several days. As the high moves farther
east part of the front may rupture and move toward the local area in
fragments that will create scattered showers Monday and Tuesday in
our typical pattern of night and early morning showers across the
U.S. Virgin Islands and eastern Puerto Rico, followed by showers in
western and interior Puerto Rico during the afternoon. Moisture
continues Sunday night, when precipitable water peaks near 1.6
inches which is less than expected yesterday, but it fades on
Monday. Moisture will recover overnight Tuesday. Although scattered
showers will continue, amounts will generally be light. The
atmosphere will be more stable than usual with lifted indices of
minus 1 to minus 4. Slightly more unstable conditions are expected
Monday and Tuesday afternoons.

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

A frontal boundary is forecast to remain well to the north of the
region during the end of the workweek. A surface high pressure
behind the front will increase winds and moisture transport across
the region during the weekend as it moves from the western
Atlantic into the central Atlantic. A weak mid level ridge is
forecast to build from the western Caribbean into the region from
Friday through Sunday. A surge in moisture through 700mb is
expected on Wednesday, this will be associated to the remnants of
the current frontal boundary north of the area. A similar peak in
moisture is forecast during the weekend with the remnants of the
next frontal boundary and a northeast wind flow. However, lacking
any upper level support, scattered afternoon showers are expected
each day over western PR and trade wind showers during the night
and early morning hours across the USVI and the eastern sections
of PR.


&&

.AVIATION...Bubbles of moisture in ENE flow south of a cold front
just north of 21 N continue moving through the area with -SHRA
mainly ovr the lcl waters and ern PR. Conds are expected to remain
VFR with brief MVFR in passing SHRA. SHRA will re-dvlp in wrn PR
with areas of mtn obscurations and brief MVFR for TJMZ and psbly
TJBQ btwn 02/17-23Z. The front will make little progress
southward drg the next 24-48 hrs. Sfc winds ENE 8-16 kt with sea
breeze influences aft 02/14Z--less inland. Max winds NW 35 kt at
FL410. LLVL wind max E 25 kt at FL059 by 03/12Z.


&&

.MARINE...Northerly swell will keep seas between 5-7 feet across
the offshore Atlantic waters through late Monday. Portions of the
local passages will reach 7 ft on Monday and small craft
advisories are in effect for these waters. Winds are expected to
increase between 15-20 knots through Monday night. Small crafts
should exercise caution across the rest of the local waters. A
high risk of rip currents along the Atlantic beaches of PR,
Culebra and St. Thomas will continue through at least early next
week.



&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 88 75 / 40 50 50 40
STT 86 76 87 75 / 40 40 40 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
503 AM AST Mon Dec 3 2018

.SYNOPSIS...East northeast flow continues through Saturday and
will carry patchy moisture. Dry air aloft at mid levels will
keep showers shallow and moderate to fresh trade wind flow will
keep passing showers brief and accumulations--if any--light. The
cold front to the north will not be able to move farther south
until stronger reinforcements arrive sometime beyond the next 10
days.

&&

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

A surface high pressure across the central Atlantic will promote
trade wind showers across the regional waters. Therefore, passing
showers are expected through the short term period across portions
of the USVI and the eastern and northern sections of Puerto Rico.
Rainfall accumulations should be generally light across the
islands during the next few days. An upper level ridge will
continue to dominate the central Caribbean through at least
Tuesday, promoting drier air aloft. Precipitable water content
peaks on 05/06z at 1.54 inches but by 05/18z it drops to 1.12
inches according to the latest GFS forecast sounding. Lacking any
upper level support, vertical development of afternoon showers
over western PR will be limited. Breezy trades will continue
through at least Tuesday morning, with steering winds between
15-20 kt. Daytime temperatures across the islands should range
between the mid to high 80s. Minimum temperatures are expected in
the low 60s across the higher elevations.

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

High pressure forms a protective wedge between the local area and
an approaching cold front. Under only weak forcing from a surface
high that migrates across the western Atlantic over the weekend,
it is unable to drop much farther south than about 24 north
latitude, however patches of moisture will continue to traverse
the area out of the central Atlantic. This air will arrive after
traveling around a low that forms in the eastern Atlantic not far
from the Cape Verde Islands to maintain a weather scenario of
scattered showers that sees little change during the next 4 to 8
days. Beyond that, the next surge of cold air is presently
assessed as being stronger and will push more aggressively toward
the northeast Caribbean. It is still too early to say if there
will be a frontal passage by mid December-- but the possibility
exists.

&&

.AVIATION...Mainly VFR conditions are expected to prevail during the
next 24 hours across all terminals. However, trade wind showers
could move at times across TIST/TJSJ through the day. Brief SHRA
are possible in the afternoon in and around TJMZ. ENE winds will
continue between 10-20 kt. Maximum winds E 25-30 kt btwn FL050-090
and NW 25-35 kt btwn FL310-460.

&&

.MARINE...Seas will increase during the day today in the local
Atlantic waters and passages. Seas will then diminish rapidly
Tuesday and Tuesday night and small craft advisories will be taken
down then. Seas are expected to remain below 7 feet until Sunday,
when small craft advisories may be needed in the outer Atlantic
waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 75 85 75 / 40 20 40 50
STT 86 75 85 75 / 30 20 20 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
517 AM AST Tue Dec 4 2018

.SYNOPSIS...Surface high pressure will dominate the sub-tropical
mid latitudes through the period driving east northeast trade wind
flow. Patches of moisture will bring clusters of shallow showers
across the U.S. Virgin Islands and Puerto Rico. Flow will turn
southeast on Sunday as a cold front approaches the area.


&&

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

A surface high pressure, northeast of the local islands, will
continue to dominate the low level flow, promoting moderate to
locally fresh east to northeast trade winds across the region. A
similar weather pattern will persist through the short term period.
That is, the occasional patch of moisture embedded in the trade
winds will result in cloud and shower clusters moving over the U.S.
Virgin Islands and portions of northern and eastern Puerto Rico.
Local and diurnal effects will support the development of showers
over portions of the interior and western Puerto Rico in the
afternoon. However, the presence of a mid to upper level ridge will
limit the intensity and coverage of any shower activity, resulting
in minimal rainfall accumulations. Daytime high temperatures across
the islands should range between the low 70s to high 80, whereas the
overnight minimum temperatures are expected in the low 60s to low
80s.

.LONG TERM...Friday through Tuesday

At upper levels, a weak short wave will cross through the area on
Friday. Then, high pressure will build over the area through the
rest of the period with west northwest flow through the period. At
mid levels dry air will dominate the area from a ridge of high
pressure that remains near or over the area through Tuesday
providing subsidence.

At lower levels, an approaching cold front will be about 430
miles northwest of San Juan on Friday. It will stall there, but
some rotation in high pressure at 700 mb will bring the boundary
to within 330 miles north of San Juan by Saturday night. Low level
flow will be east northeast through Sunday and this flow will
carry patches of moisture that form showers upstream and drag them
across the area. Then, Sunday, the flow turns to the southeast
for several days as the center of the 700 mb high pressure moves
east into the central sub-tropical Atlantic. Overall moisture
peaks during the weekend, but is highly variable in a diurnal
pattern. This will bring scattered showers and periods of mostly
clear or sunny weather throughout the period. With dry mid-levels,
rain amounts will continue to be modest, but some heavy rains
could occur for short periods.

&&

.AVIATION...VFR conds are expected across the local terminals for
the next 24 hours. Brief showers may cause VCSH across TJSJ,
TIST, TISX, TNCM and TKPK through at least 04/14Z. Areas of mtn
obscurations. Winds of 10-15kt from the E and sea breeze
variations through 04/22Z, decreasing to 5-10kt during through
05/06Z. Maximum winds WSW 40-50 kt btwn FL340-500.

&&

.MARINE...The seas at the outer buoy have subsided to below 7 feet
and even the winds have been only 8 to 10 knots since about 2 AM
AST. This will allow seas in the local forecast area to continue
to subside, and they are expected to do so through Thursday. At
this time small craft advisory conditions are not expected through
early next week.

&&

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

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
449 AM AST Wed Dec 5 2018

.SYNOPSIS...A seasonal weather pattern is expected during the next
few days under mostly clear to partly cloudy skies and the
occasional patch of moisture embedded in the trade winds
streaming across the forecast area. As a result, trade wind
showers may affect the U.S. Virgin Islands and the windward
sections of Puerto Rico each night and early morning hours.
Limited afternoon convection is expected across the interior and
western Puerto Rico each day. However, due to unfavorable mid to
upper level conditions, minimal rainfall accumulations are
expected throughout most of the forecast period.


&&

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

High pressure in the east central Atlantic will recede to the east
northeast leaving only gentle to moderate east northeast trade wind
flow that will carry patches of moisture and light to moderate
showers through Friday. Mid layers remain dry and will cap any
convection to keep showers shallow. High pressure at upper levels
will dominate the Caribbean and flow aloft will remain west
northwest and slightly convergent. Although the atmosphere is
marginally unstable the drier air at mid levels will stifle
convection that tries to initiate over western Puerto Rico.

This means that although there will be showers from time to time
during the period, amounts will be light and generally follow the
typical diurnal pattern of night and early morning showers over the
U.S. Virgin Islands and eastern Puerto Rico then some inland showers
over western Puerto Rico during the afternoons. Periods of isolated
showers will continue over the local waters through Friday.

Temperatures will continue near or slightly above normal.


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

Model suggests that a frontal boundary will stall far to the north
of the forecast area while it gradually weakens and dissipates on
Saturday into Sunday. At the same time, a dominant east northeast
wind flow will shift from the east southeast on Sunday through
midweek as a 700 mb high pressure travels eastward into the
central sub-tropical Atlantic. Regardless of the direction of the
low-level wind flow, patches of moisture are expected to move
across the forecast area from time-to-time. Although the time of
arrival of these patches vary significantly among the global
models, clusters of clouds and showers are expected to stream over
the waters into coastal areas of the local islands with
throughout the forecast period. Due to local and diurnal effects,
showers development remains possible over the interior and western
sections of Puerto Rico each afternoon. However, the presence of
unfavorable mid to upper level conditions will limit the intensity
and coverage of any shower activity, resulting in modest rainfall
accumulations.

Overall, a seasonal weather pattern is expected to prevail through
late Wednesday night before another frontal boundary approaches
the forecast area from the northwest and stall north of the local
islands. No shower development enhancement is expected with this
feature, but the forecast confidence is low at this time. The
low-level wind flow is expected to shift once again from the east
northeast on Wednesday.


&&

.AVIATION...VFR conds expected across the local terminals for the
next 24 hours except btwn 05/17-21Z when LCL mtn obscurations and
brief MVFR is psbl at TJMZ and hir trrn. Brief showers will pass
near TJPS and TJMZ drg the same period, and then brief -SHRA aft
06/00Z arnd TIST/TISX. ENE winds incrg to 10-15kt with sea breeze
variations through 05/22Z, becoming light overnight with land
breeze influences. Maximum winds WNW 20-25 kt btwn FL380-480.


&&

.MARINE...Small craft operators should exercise caution across the
outer Atlantic and Caribbean waters, as well as the local passages
due to seas up to 6 feet. These conditions should persist through
Thursday afternoon, when seas are expected to drop below 6 feet. A
small northeast swell will continue to move across the Atlantic
waters through Friday morning, but will increase up to 6 feet on
Friday afternoon through the weekend. As a result, small craft
advisories may be issued due to seas up to 7 feet on Saturday and
Sunday.


&&

.FIRE WEATHER...Although recent observations of KBDI values and
10-hour fuel moisture across the southern plains of Puerto Rico
have been at critical values (>550 and <10%, respectively), winds
and relative humidity values are forecast to remain below critical
conditions (<15mph and <55%, respectively) today. Given the case,
the fire danger risk has been set to moderate and thus, no
RFD/RFW product will be issued at this time. However, a slight
change of these variables could result in an elevated fire danger
risk, particularly across the southern coastal plains and hills of
Puerto Rico.


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
528 AM AST Thu Dec 6 2018

.SYNOPSIS...A seasonal weather pattern is expected through
midweek with a mixture of clear skies, passing clouds and
occasional trade wind showers especially overnight and during the
morning hours. Afternoon convection should not be ruled out across
the interior and western Puerto Rico each afternoon. An increase
in moisture advection and the potential for showers is expected
late Wednesday through the end of next week as a frontal boundary
approaches the local area.


&&

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

Mid to upper level ridge will slightly erode today through early
Friday as a short wave trough will continue to move across the west
and central Atlantic. Ridge aloft is to then build overhead and once
again increase the trade wind cap inversion. Surface high pressure
ridge across the north central Atlantic, and a frontal trough
extending across the west and southwest Atlantic will maintain a
moderate east northeast wind flow through early Friday. By late
Friday and into the weekend, a surface ridge is to build across the
west Atlantic and north of the region resulting in a gradual
increase in the easterly trade winds as the local pressure gradient
tightens.

During the overnight hours, fragments of low to mid level clouds
with embedded showers continued to develop and move quickly across
the local waters and brush parts of the north and east coastal
sections of Puerto Rico and the remainder of the islands. Due to the
fast movement of the showers, estimated rainfall accumulations were
less than a half of an inch. A drier airmass is forecast to move
into the region by late morning resulting in mostly sunny skies.
However, local terrain effect and daytime heating will give way to
afternoon shower development mainly over parts of the interior, and
west to southwest sections of Puerto Rico. Fewer showers are
forecast for the USVI today as mostly fair weather should prevail
during the afternoon hours. On Friday and Saturday, the building
surface ridge north of region will promote overall fair weather
conditions, however the increasing easterly trade winds will bring
more frequent passing low level clouds and showers to the coastal
area especially during the overnight and early morning hours.


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

Model suggest that as the center of a 700 mb high pressure system
moves eastward over the local area into the central sub-tropical
Atlantic the wind flow will shift direction. The east northeast
low-level wind flow is expected to turn from the southeast while
subsiding as the local pressure gradient relaxes on Monday through
Wednesday afternoon. Regardless of the direction and intensity of
the low-level wind flow, patches of moisture accompanied by
clusters of clouds and showers are expected to move across the
forecast area from time-to-time. This will result in showers
moving over windward areas of the islands during the overnight and
morning hours, followed by afternoon convection over the interior
and western sections of Puerto Rico each afternoon. However, the
presence of unfavorable mid to upper level conditions will limit
the intensity and coverage of any shower activity, resulting in
light to moderate rainfall accumulations.

The weather pattern previously described will persist through
Wednesday afternoon, when a frontal boundary approaches the
forecast area from the north late Wednesday night into Thursday.
As this occurs, surface winds are expected to turn from the
northeast and increase as the local pressure gradient tightens in
association to a low to mid level high pressure building and
moving over the western Atlantic. This will increase moisture
advection and the potential for shower activity across the
forecast area. However, significant discrepancies exists between
global models on the location of the frontal boundary. The ECMWF
model suggest that this feature will stall just north of the
islands, while the GFS solution has it moving over the local area
on Thursday. Although there is low confidence on the evolution of
these features due to the timing within the long term range, it
was agreed that the current forecast should follow the GFS
solution.


&&

.AVIATION...VFR conds durg fcst prd. -SHRA/SHRA embedded in clds
lyrs btw FL025..FL050 ovr regional waters and en route btw local
islands til 06/14z. Mtn Top obscr in low clds and -SHRA ovr E PR. Fm
06/16z-06/22z...SHRA ovr ctrl mtn range of PR with VCSH at
TJMZ/TJBQ/TJSJ. SFC wnds of 10-15kt with ocnl gust with sea breeze
variations til 06/22z...then becoming light/vrbl.


&&

.MARINE...Small craft operators should exercise caution across the
outer Atlantic and Caribbean waters, as well as the local passages
and coastal waters of southern and western Puerto Rico due to
seas up to 6 feet and/or winds up to 20 knots. Although seas will
drop below 6 feet, caution should be exercise as winds up to 20
knots will prevail. Seas are forecast to increase once again
Friday night through the weekend as a northerly swell invades the
local waters. As a result, small craft advisories may be required.
There is a high risk of rip currents for beaches along the
northwestern coast of Puerto Rico. Elsewhere, a moderate to low
risk of rip currents will continue.


&&

.FIRE WEATHER...Recent KBDI and 10-Hour Fuel Moisture observations
confirms that the soil and fuels continue to dry out across the
region, particularly across the southern plains of Puerto Rico
with values below 550 and 10%, respectively. No significant
changes are expected in the weather pattern today. Given that no
wetting rains are expected, and the forecast calls for relative
humidities to fall below critical levels (40-45% at Camp Santiago
and 50-55% at Cabo Rojo) with patchy areas of winds between 15-20
mph moving across these areas, an elevated fire danger is
expected for the southern plains of Puerto Rico today and a Fire
Danger Discussion has been issued.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 75 85 75 / 30 60 60 60
STT 86 75 86 75 / 20 60 50 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
430 AM AST Fri Dec 7 2018

.SYNOPSIS...A stable weather pattern will continue to prevail
across the region through at least the first half of next week as
a ridging pattern continues to hold serve. A wetter weather
pattern is possible by the middle to latter half of next week as a
frontal boundary approaches the local area.

&&

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

A surface high pressure across the central Atlantic and a frontal
boundary extending across the western Atlantic Ocean will maintain
the islands under an advective pattern through the short term
period. Therefore, a winter weather pattern will prevailed with a
mixture of clear skies, passing clouds and occasional trade wind
showers especially overnight and during the morning hours. The
interior and western sections of Puerto Rico should not ruled out
the development of afternoon convection each day. Temperatures will
continue near or slightly above normal each day.

Overall dry and stable air mass aloft will continue to limit shower
development across the region for the next several days. However
with the strengthening high pressure ridge north of the region expect
the moderate to fairly strong easterly trades to continue to advect
occasional surges of low level moisture across the region with this
pattern being most frequent today and Saturday. Showers embedded in
prevailing east north east trades will therefore continue to affect
the coastal waters, parts of the Virgin Islands and north and east
sections of Puerto Rico overnight into the morning hours. Afternoon
cloudiness and shower development should be focused over the
interior and west section of Puerto Rico, with partly cloudy to
mostly sunny conditions expected elsewhere and limited shower
activity. Similar conditions expected for Saturday as another surge
of trade wind moisture will make its way across the region.

By Sunday, the dominant surface high pressure is to reestablish
across the central and eastern Atlantic resulting in a slight shift
from northeasterly to easterly trades winds. By then the mid to
upper ridge is to also build across the region reinforcing the stable
conditions aloft. The typical seasonal weather pattern is expected
with mostly fair weather skies and a mixture of clear skies, passing
clouds and occasional trade wind showers especially overnight and
during the morning hours. The interior and western sections of
Puerto Rico should not ruled out the development of afternoon
convection on Sunday. Temperatures will continue near or slightly
above normal each day.

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

Not much change to the overall weather pattern is expected through
the first half of the upcoming week as the ridging pattern will
continue to maintain stable weather conditions across the forecast
area. Surface high pressure across the east-central Atlantic will
continue to transport patches of low-level moisture across the
region at times. Therefore, some brief passing trade wind showers
can be expected across portions of eastern Puerto Rico, the USVI,
and surrounding waters, especially during the overnight and early
morning hours. Limited shower activity is possible across the
western half of Puerto Rico during the afternoon hours.

Model guidance continues to indicate that a frontal boundary will
be approaching the local area by later Wednesday into Thursday,
increasing the moisture content. Therefore, if the current model
trend continues to hold, expect an increase in shower activity
across the forecast area. In addition, winds will also decrease as
the pressure gradient between the surface high pressure across
the eastern Atlantic and the frontal boundary relaxes.


&&

.AVIATION...VFR conds durg prd. Passing trade wind clds will lead to
SCT-BKN lyrs nr FL025...FL050 and SHRA across the regional waters
and en route btw islands. Brief MVFR in SHRA/Low clds w/Mtn Top
obscr ovr E PR til 07/12z. Sfc wnd lgt/vrb...bcmg 10-15kt with ocnl
gusts and sea breeze variations aft 07/14z. Wnd fm E-NE 15-20 kts
Blo FL250. No six WX impacts Attm.


&&

.MARINE...Choppy seas up to 6 feet expected across the offshore
Atlantic waters with seas between 3 to 5 feet expected across the
rest of the regional waters. The combination of a small northerly
swell and locally fresh trade winds is expected to increase seas
across the regional waters through the weekend. There is a moderate
risk of rip currents for several of the local beaches of the
region through this afternoon. A high risk of rip currents is
expected for the northwest to north central beaches of Puerto Rico,
including San Juan Vicinity beginning tonight.


&&

.FIRE WEATHER...Recent KBDI and 10-Hour Fuel Moisture observations
indicate that the soil and fuels continue to dry out across the
region, especially across the southern coastal Plains of Puerto
Rico. With no wetting rains expected for today, KBDI and 10-Hour
Fuel Moisture will continue to be within critical threshold levels
with the potential for patchy areas of winds exceeding 15 mph at
times. Therefore, an elevated fire danger threat is expected to
continue for today for the southern coastal plains of Puerto Rico
and a Fire Danger Discussion has been issued.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 76 84 73 / 50 40 40 40
STT 87 76 88 75 / 30 40 40 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
515 AM AST Sat Dec 8 2018

.SYNOPSIS....
A surface high pressure across the northeast Atlantic and a weakening
cold front and associated frontal boundary extending across the west
and central Atlantic, will maintain moderate northeast winds and an
advective moisture pattern through the weekend. Mid to upper level
ridge will hold across the area to limit daytime convection. A stable
weather pattern will therefore prevail through at least the first
half of next week as a ridging pattern is expected to hold. A wetter
weather pattern is possible by the latter half of next week as a
frontal boundary is forecast to approach the local area.

&&

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

Surface high pressure across the northeastern Atlantic and a
stationary front north of the local area will keep easterly winds
across the area today. A patch of moisture is expected to move in,
especially for the late morning and through this afternoon, which
will cause an increase in shower activity once combined with local
effects and diurnal heating. This means that cloudiness is expected to
develop across the higher elevations of the islands and some showers
could stream off the islands. Scattered showers are forecast to
linger a bit across western PR in the afternoon but the rainfall
amounts are not expected to cause hazardous conditions since the
column of moisture is not particularly deep and there is a ridge in
he mid to upper levels. For Sunday, the patch of moisture is
expected to have passed already and drier air should be over the
local area. Therefore the shower activity is expected to be isolated
and brief. Monday looks like another path of moisture is going to
move through the local area while a surface low moves into the
central Atlantic, causing the local winds to become a bit more
southeasterly. This may cause showers on Monday afternoon across the
northwestern sections of PR. Through the next few days the local
temperatures are expected to remain near normal.

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

The weather pattern is expected to remain the same through at least
Tuesday as the overall dominant ridge pattern will maintain stable
weather conditions across the forecast area. Surface high pressure
across the east- central Atlantic will however continue to transport
patches of low-level moisture across the region at times. Therefore,
brief passing trade wind showers can be expected across portions of
eastern Puerto Rico, the USVI, and surrounding waters, during the
overnight and early morning hours. Limited shower activity during
the day will follow but will be possible mainly across parts of
the interior and the western half of Puerto Rico during the afternoon
hours.

By the latter part of the upcoming week, model guidance continued
to suggest that a frontal boundary will be approaching the local area
by late Wednesday into Thursday. This additional moisture convergence
will increase the chance for shower development across the forecast
area. The mid to upper ridge is to also erode as a short wave trough
moves across the west and central Atlantic thereby weakening the
trade wind inversion and increasing instability aloft. If in fact
the current model trend continues to hold, expect an increase in
shower activity across the forecast area at least through Thursday.
In addition, the local winds are forecast to decrease as the pressure
gradient relaxes between the Atlantic surface high pressure and
the aforementioned frontal boundary. Improving conditions expected
by Friday through Saturday as the high pressure ridge reinforces once
again across the region and becomes the dominant weather feature.

&&

.AVIATION...VFR conds are expected for the next 24 hours. SHRA
activity today is expected to cause at least VCSH through the day.
TEMPO SHRA and a reduction of visibility is possible for brief
periods of time. MTN obscurations could occur today as cloudiness
develops over the higher elevations after 08/14Z. Winds will be
mainly from the east at around 10KT through 08/13Z, increasing to
about 15kt and gusty thereafter. Sea breeze variations expected to
develop after 08/14Z.


&&

.MARINE...Seas across most of the area are 3 to 5 feet, but are
forecast to increase to 5 to 7 feet late tonight across the outer
Atlantic waters with east to northeast winds between 10 to 20 knots.
A small craft advisory is now in effect due to the arrival of a
northerly swell and gradually increasing winds. Elsewhere seas
will range from 4 to 6 with east to northeast winds of 10 to 20
knots with higher gusts possible. Therefore small craft should
exercise caution due to the hazardous and choppy marine conditions.
There is a high risk for rip currents for the northern beaches of
Puerto Rico, and Culebra. These conditions are expected to continue
through Sunday morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 74 86 74 / 40 20 20 10
STT 84 75 86 75 / 30 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
513 AM AST Sun Dec 9 2018

.SYNOPSIS... Mid to upper level ridge as well as the surface ridge
across the northeast Atlantic will continue to build and hold across
the forecast area through the middle of the upcoming week. The moderate
wind flow will persist but will become more southeasterly Monday through
Wednesday, then return to a more east to northeast flow during the
latter part of the work week. While mostly fair weather skies should
prevail during the period, expect the overall advective pattern to
continue resulting in periods of passing clouds and occasional trade
wind showers especially during the overnight and early morning hours.
Daytime convection should remain limited to isolated areas with
no widespread rainfall anticipated at this time.

&&

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

The mid and upper levels will have high pressure, cause for a fairly
stable atmosphere locally. As far as the surface, a high pressure
across the northeastern Atlantic will keep a mainly easterly wind
flow today, but a surface low moving across the southeastern US into
the western Atlantic will cause a shift in the local winds early in
the workweek to a more southeasterly direction.

For today, drier air should be over the local area, causing mainly
fair weather with limited shower activity during the day, mainly due
to orographic lifting combining with the wind flow and diurnal
heating. So any shower that does occur is expected to be mainly
brief. Monday still looks like another path of moisture is going to
move through the local area while the aforementioned surface low
moves into the Western Atlantic, causing the local winds to become
southeasterly. This may cause showers on Monday afternoon across the
northwestern sections of PR. Tuesday looks similar to Monday, with a
patch of moisture moving in and the southeasterly winds causing the
NW portions of PR to have the highest chance of significant showers
in the afternoon.

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

The dominant mid to upper level ridge pattern is to hold and maintain
stable weather conditions across the forecast area through Wednesday.
By Thursday a short wave trough is forecast to move across the west
Atlantic and erode the upper ridge. However, surface high pressure
across the central and northeast Atlantic will hold and continue
to aid in transporting patches of low- level moisture across the
region. Consequently, the prevailing easterlies will bring periods
of passing showers to the local waters and over portions of the
islands especially during the overnight and early morning hours.
Limited convection is forecast during the rest of the day but
shower development will remain possible mainly across parts of the
interior and the western half of Puerto Rico during the afternoon.

By Friday and into the weekend, recent guidance have been persistent
in suggesting that a frontal boundary/shearline will stall northwest
and north of the region. However, as surface high pressure builds
across the west Atlantic and spreads north of the region, expect
the local pressure gradient to tighten once again. This in turn
will increase the easterly trade winds resulting in more frequent
transport of trade wind showers Friday through Saturday. A gradual
improvement and lesser frequent shower activity is expected by Sunday.

&&

.AVIATION....VFR conds are expected for the next 24 hours. Some SHRA
activity today could cause VCSH at TJSJ, TJMZ, and TJBQ after
09/16Z. MTN obscurations could occur today as cloudiness develops
over the higher elevations after 09/14Z. Winds will be mainly from
the east at around 10KT through 09/13Z, increasing to about 15kt and
gusty thereafter. Sea breeze variations expected to develop after
09/14Z.

&&

.MARINE...Seas will range between 4 to 6 feet over the offshore
Atlantic waters and local passages ,and 3 to 5 feet elsewhere.
Winds will be from the east between 10 to 20 kts with occasionally
higher gusts. A northerly swell will continue across portions of the
local waters today while slowly subsiding. Due to the choppy seas
and fading swell action, small craft operators should continue to
exercise caution across most of the local waters.

A high risk of rip currents for the northern beaches of Puerto
Rico, and Culebra today. A moderate risk of rip current will
continue for most of the remaining local beaches. Please refer to
the latest Surf Zone Forecast issued (SRFSJU) issued by WFO San
Juan Puerto Rico.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 73 87 74 / 20 30 30 30
STT 85 76 86 75 / 20 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
414 AM AST Mon Dec 10 2018

.SYNOPSIS...Surface low pressure across the western Atlantic is
moving to the east northeast. This low pressure will shift the
local wind flow to a southeasterly direction for the first part
of this workweek. Thereafter a surface high pressure will keep an
easterly wind flow for the rest of the week into the weekend.
Patches of moisture will pass through the local area most
afternoons this week, which will help in the development of some
showers across the local area.

&&

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

Mid and upper level high pressure ridge will continue to dominate
the local weather conditions through Tuesday, resulting in a fair
weather pattern across Puerto Rico and the U.S. Virgin Islands.
Easterly trade winds will push a few showers over the windward areas
at times especially at night and early in the morning, but no
significant rainfall is expected with these brief showers. Diurnal
convection will be limited as high pressure suppress the vertical
development of the showers, but if it develops will be focused
mainly over the west and northwest Puerto Rico in the afternoon.
This stable pattern will likely continue through Tuesday.

Then, a pre-frontal trough/shearline will approach the region on
Wednesday, increasing the moisture and instability. Under this
scenario, scattered to numerous showers are possible across portions
of Puerto Rico and the U.S. Virgin Islands. With additional
instability the afternoon showers over western Puerto Rico will be
more intense and should persist through the evening hours on
Wednesday.

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

The long term forecast does not suggest like much active weather
is to be expected. The mid to upper levels will keep a ridge over
the local area for most of the latter part of the week and
weekend. However, by the end of the forecast period, the global
models are suggesting some slight troughiness in the upper levels
but to the east of the local islands, which normal does not cause
inclement weather over the local islands. High pressure will be
to the north of the local islands late in the week and early
weekend, keeping an easterly wind flow, but from Sunday through
Tuesday a surface low will move across the western Atlantic,
causing the local winds to decrease and turn more southeasterly.
Near normal moisture is expected with some days having slightly
more moisture than others. A frontal boundary appears to stall to
the northwest for the local area late in the forecast period but
far enough to not cause issues locally. So the bottom line is that
a normal weather pattern is expected in the log term, with some
brief showers in the morning across the local waters, USVI and
eastern PR, then a few showers possible in the afternoon across
portions of western PR.

&&

.AVIATION...VFR conditions will continue thru the forecast period.
No major concerns expected over the next 24 hours. Passing SHRA may
affect the terminal at times but cigs and vis will likely remain VFR
most of the time. ESE winds around 10-20 kts will prevail below
FL100.

&&

.MARINE...Small craft operators are urged to exercise caution
across the Caribbean eaters, offshore Atlantic, and local
passages due to winds up to 20 knots or seas up to 6 feet. There
is a moderate risk of rip currents across most of the local
beaches.


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
445 AM AST Tue Dec 11 2018

.SYNOPSIS...
The combination of a surface high pressure across the East
Central Atlantic and a surface low pressure across the
Northwestern Atlantic will help promote a more southeasterly wind
flow today, becoming more easterly as the surface low continues
to move northeast. Mid and upper level ridges will continue to
create a relatively stable atmosphere. Patches of moisture and
dry air will be observed today.

&&

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

Mid to upper level ridge is strong enough to limit the shower
activity across the northeast Caribbean. The ridge pattern will
favor a fair weather pattern across the local region though at least
midweek. Trade winds generated by a surface high pressure over
northeast Atlantic will push a few showers over the local islands at
times, but no significant rainfall is expected with these passing
showers. Diurnal convection, if any, will be focused mainly over the
northwest Puerto Rico each afternoon.

An area of high moisture content associated with a shearline is
forecast to approach the region Wednesday night, bringing additional
showers to the U.S. Virgin Islands and Puerto Rico. This feature
will move quickly across the area, therefore the fair weather
pattern will return on Thursday.

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

The long term forecast still does not suggest like much active
weather is to be expected. Long range guidance is still suggesting
that the mid to upper levels will keep a ridge over the local
area for most of the latter part of the week and weekend. However,
by the end of the forecast period, the global models are
some slight troughiness in the upper levels could be observed on
Tuesday and Wednesdays, but the location of this weak trough has
shifted in the forecast given by the long range models. Near
normal moisture with patches of slightly higher moisture is
expected from Friday through the weekend, drying up a little bit
early next week. A frontal boundary still appears to stall to the
northwest for the local area early next week but far enough to
not cause issues locally. Therefore, a relatively normal weather
pattern is expected in the log term, with nothing more than brief
showers in the morning across the local waters, USVI and eastern
PR, then a few showers possible in the afternoon across portions
of both eastern and western PR, as well as the USVI.


&&

.AVIATION...VFR conditions will prevail thru the forecast period,
with no major concerns expected at this time. VCSH possible near the
USVI and Leeward terminals from time to time. ESE winds around 10-20
kts will prevail below FL100.

&&

.MARINE...Seas are expected to be mainly between 3 and 5 feet
with winds generally in the range of 10 to 15 knots today and
Wednesday, slowly increasing waveheights on Thursday into the
upcoming weekend as a northerly swell invades the local waters.



&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 74 86 75 / 10 30 40 40
STT 84 74 84 73 / 20 30 30 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
444 AM AST Wed Dec 12 2018

.SYNOPSIS...Drier than normal air mass is expected over the local
area today. Ridge in the mid and upper levels will keep a fairly
stable atmosphere. Surface low across the western Atlantic will
cause light to moderate winds while lowly turning easterly and
becoming slightly stronger by this evening.

&&

.SHORT TERM...Today through Friday..

A stable air mass remains in place, but a weak shearline to the
northwest of Puerto Rico is forecast to pull moisture across
Puerto Rico this afternoon. The moisture will produce light to
moderate showers mainly across portions of northern, interior and
western areas of Puerto Rico this afternoon. Then Thursday through
Friday patches of low-level moisture is progged to move across
the area periodically, which could induce scattered showers mainly
during the early morning hours across the eastern forecast areas,
and during the afternoon across the northern, interior and
western areas of Puerto Rico. However, recent model guidance has
flipped on the drier pattern and shows a wetter pattern during the
short-term period, but several factors go against recent model
guidance.

First analysis of TJSJ Skew-T shows a strong inversion at 850 mb
today through Friday as well as drier air at the middle to upper-
levels of the atmosphere. The drier air as well as the inversion
will keep deep convection from developing, and moving across the
islands over the next several days. In addition, with the mid to
upper-level being so dry it will take deep tropical moisture to
produce area wide pops that the GFS ARW and NMM are producing, and
at this time deep tropical moisture will remain to the south of the
islands. Due to the aformentioned factors pops were decreased
considerably from current guidance with only isolated to scattered
showers in forecast.

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

The mid to upper levels will have a ridge of high pressure through
Monday, which will provide a relatively stable atmosphere. In
addition, the available moisture will be near or below normal
which will limit the coverage and intensity of possible showers,
especially when in most cases the moisture will be confined to
the lower levels. However, the global models are still suggesting
some troughiness in the mid and upper levels on Tuesday and
Wednesday, but the location of this trough is still shifting
slightly between model runs, so the jury is still out on a more
precise location of this trough. Even with this troughiness in the
mid and upper levels, the models do not seem to be impressed and
the precipitation solution for those days is nothing more than
scattered showers once again over the waters, USVI, and Puerto
Rico. A frontal boundary still appears to stall well to the
northwest for the local area early next week, likely far enough to
not cause issues locally. Therefore, a relatively normal weather
pattern is expected in the log term, with nothing more than brief
showers in the morning across the local waters, USVI and eastern
PR, then a few showers possible in the afternoon across portions
of both eastern and western PR, as well as the USVI.

&&

.AVIATION...Mainly VFR conditions are expected across all terminals
through the forecast period. Sfc winds out of the east to southeast
will continue at 10-15 kt. -SHRA possible mainly across TJSJ,
TIST, and TISX by 12/18Z, then showers should diminish by 13/00Z.


&&

.MARINE...Seas of 3 to 5 feet are expected today with winds
generally below 15 knots. The winds and seas will gradually
increase starting on Thursday with seas increasing up to 6 feet
and winds up to 20 knots, then seas increasing even more, becoming
hazardous by Friday with wave heights up to 7 feet as stronger
winds and a northerly swell combine, causing said hazardous seas
by Friday and through the weekend.


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
354 AM AST Thu Dec 13 2018

.SYNOPSIS...
A stable weather pattern will continue to prevail through the
middle of next week. Winds will increase from the east due to a
ridge of high pressure that will strengthen across the central
Atlantic late tonight. The strong winds created by the building
ridge of high pressure will transport moisture across the area
periodically over the next several days, but due to the dry mid to
upper levels of the atmosphere any showers that develop will be
brief.

&&

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

Mainly stable weather conditions will continue as a mid to upper-
level ridge pattern continues to hold across the region. This will
continue to keep the atmosphere above 700 mb extremely dry with
relative humidity values at less than 10%. Therefore, no significant
rainfall is expected during the foreseeable future.

At lower-levels, a patch of moisture moved just north of Puerto Rico
during the overnight, producing a few showers over the Atlantic
waters and northeastern sections of the island. As this patch of
moisture moves away, an area of drier air will filter in from the
east during the morning hours, keeping most of the forecast area
dry. By this afternoon, another patch of moisture will move in from
the east and move over the USVI and eastern PR during the afternoon
and evening hours. Therefore, a few brief showers could affect these
areas as well as across western portions of Puerto Rico due to local
and diurnal effects.

By Friday and Saturday, strong surface high pressure moving across
the western and central Atlantic will increase the winds across the
forecast area. Therefore, breezy conditions are expected. At the
same time, more frequent passing showers are expected to affect the
local area as the strong low-level trade wind flow will transport
patches of low-level moisture at times with the highest
accumulations expected across eastern Puerto Rico and the USVI.

&&

.LONG TERM...Sunday through Friday...
The long-term period will be defined by strong ridging at the mid
to upper levels of the atmosphere, which will create stable
weather conditions through most of the extended period. Relative
humidities values at the middle to upper level of the atmosphere
will range from 20 to 40 percent, which means moisture will be
limited; but at 850 mb the relative humidities values will range
from 50 to 80 percent. The moisture at the surface is sufficient
enough to cause scattered showers mainly during the early
mornings across portions of eastern Puerto Rico as well as the
U.S. Virgin Islands, then showers could develop across other areas
as a result of the sea breeze. The development of the seas breeze
depends on the speed of the surface winds; at this time guidance
shows winds ranging from 15 to 20 mph as a result of the strong
ridge of high pressure to the east of the Islands. Winds greater
than 15 mph could cause the sea breeze not to develop during the
afternoon.

The middle of next week another trough will stall to the north of
Puerto Rico, with little to no affects to the local islands.
However, patches of moisture embedded in the strong tradewinds
will move across the area from time to time during the period.

&&

.AVIATION...
Mainly VFR conditions are expected to prevail across all
terminals throughout the forecast period. Some brief passing SHRA
may affect the Leeward terminal sites through the morning hours and
extend into the USVI terminals after 13/16z. VCSH cannot be ruled
out across western PR near TJMZ after 13/16z. Light and variable
winds will prevail through 13/13z, increasing from the east between
10 to 20 knots with sea breeze variations developing after 13/14z.

&&

.MARINE...
Winds will increase later today through early Saturday across the
Atlantic and Caribbean waters. A small craft advisories will go
into effect early Friday morning and will remain through late
Sunday night. Seas are forecast to range from 5 to 7 feet with
occasional seas up to 9 feet. Easterly winds are forecast through
Monday ranging from 10 to 15 kts with higher gusts up to 25 is
possible. A high risk of rip currents for the northern beaches of
Puerto Rico today through Friday afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 76 85 76 / 20 40 40 50
STT 85 75 86 75 / 30 30 30 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
401 AM AST Fri Dec 14 2018

.SYNOPSIS...
A stable weather pattern will prevail through the middle of next
week as well as strong easterly trade winds that will bring
patches of low-level moisture over the region. The low-level will
induce scattered showers across portions of eastern, and northern
Puerto as well as the U.S. Virgin Islands.

&&

.SHORT TERM...Today through Sunday...
A typical winter time pattern is expected to encompass the
forecast area through the short term period. Strong surface high
pressure moving off the northeast coast of the United States into
the Atlantic will tighten the local pressure gradient and increase
the low-level flow to produce breezy conditions at times across
the local area through the weekend. At the same time, the strong
low- level wind flow will periodically bring patches of low-level
moisture across the islands, therefore increasing the frequency of
passing showers. As a result, expect wetter conditions compared
to the last several days. These passing showers, however, should
be brief and lead to light rainfall amounts.

Through the weekend, the highest rainfall accumulations will be
concentrated mostly across the eastern half of Puerto Rico and the
USVI. Across western Puerto Rico, very limited rainfall activity is
expected as the strong low-level wind flow, which according to
forecast model soundings is progged at near 20 kts, should limit the
sea breeze influence and therefore the development of significant
showers.

&&

.LONG TERM...Monday through Saturday...
A strong ridge of high pressure is forecast to hold northwest of
Puerto Rico through the extended period. The ridge will generate
trade wind showers over the area with easterly winds ranging from
15 to 20 mph. On Tuesday the GFS shows a weak jet stream moving
through Puerto Rico, then the ridge is expected to strengthen over
the region again. The middle to upper levels of the atmosphere
will remain devoid of significant moisture, thus only scattered
showers are forecast mainly over portions of northern, eastern,
interior areas of Puerto Rico, and the U.S. Virgin islands.
Showers that develop will be brief and only produce light rainfall
amounts. Otherwise stable weather is forecast through the long-
term period with an occasional passing shower.

&&

.AVIATION...
VFR conditions expected to prevail throughout the
forecast period. Brief passing SHRA, however, are expected to affect
most of the terminal sites periodically during the forecast period.
Low-level winds are expected to increase between 15 to 20 knots with
higher gusts from the east after 14/14z.

&&

.MARINE...
A ridge of high pressure in the northwest Atlantic will create
strong easterly winds of 15 to 20 kts with higher gusts across the
local and outer waters today through the weekend. Seas are
forecast to range from 5 to 7 feet with seas occasionally
reaching up to 9 feet. A small craft advisory is in effect for the
north Atlantic waters this morning, while the Caribbean and the Mona
Passage will go into effect later this afternoon. A high risk of
rip currents for the northern beaches of Puerto Rico and Culebra
today.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
517 AM AST Sat Dec 15 2018

.SYNOPSIS...Surface high pressure moving across the Atlantic will
continue to produce breezy conditions and transport patches of
low-level moisture, resulting in occasional passing trade wind showers
through the rest of the weekend. Mid to upper-level ridge pattern
will continue to hold through most of next week, producing mostly
fair weather conditions across the region.

&&

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

A mid to upper level ridge will continue to dominate the
local area through the short term period. This will promote dry
air aloft and limit vertical development of afternoon showers.
However, a strong surface high pressure moving into the central
Atlantic, will bring passing trade wind showers in an east to
southeast wind flow across the islands. Breezy conditions are
expected to continue today and a model guidance indicates that the
best chances for showers today are across the Atlantic waters and
across portions of the USVI and northeastern PR. Winds will
gradually diminish between Sunday and Monday and sea breeze
influence over northwestern PR should result in better chances for
diurnally induced afternoon showers over western PR. However,
mostly light to moderate rainfall amounts are expected at this
moment.

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

As it has been the case throughout most of this month, the
synoptic pattern through most of next week will continue to
feature a mid to upper-level ridge continuing to hold across the
eastern Caribbean. As a result, the atmosphere above 700 mb will
continue to be very dry with relative humidity values at less than
10%. This will continue to prevent the development of deep
and organized convection. Therefore, mainly fair weather
conditions will continue to prevail across the area. Occasional
patches of moisture embedded within the trade wind flow, however,
will move over the islands. This will result in brief trade wind
showers from to time with only light rainfall amounts expected. As
it is usually the case with this trade wind pattern, the highest
rainfall accumulation is expected over portions of the eastern
half of Puerto Rico and the USVI as well as across the surrounding
waters. Across western Puerto Rico, some locally and diurnally
induced showers may develop during the afternoon hours, however,
given the very dry air present in the mid to upper-levels the
showers that do develop should be short-lived and only lead to
light rainfall accumulations.

&&

.AVIATION...Mainly VFR conditions are expected to prevail during the
next 24 hours across all terminals. However, trade wind showers
could move at times across the Leeward/USVI and eastern PR terminals
through the day. Brief shra possible in the afternoon in and around
TJBQ. ESE winds will continue between 15-20 kt.

&&

.MARINE...The combination of moderate to fresh trade winds and a
northerly swell with result in seas between 5 and 8 feet across
the local waters throughout the weekend. Therefore, small craft
advisories are in effect across most of the local waters through
the rest of the weekend. High risk of rip currents is in effect
for the northern beaches of Puerto Rico, Culebra, and Saint
Thomas.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 75 84 73 / 50 50 50 20
STT 82 75 81 76 / 50 50 50 10

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
440 AM AST Sun Dec 16 2018

.SYNOPSIS...Mid to upper-level ridge is expected to be the
dominant synoptic feature throughout the forecast period,
resulting in mainly stable weather conditions across the region.
Some brief showers, as a result of patches of low-level moisture
embedded within the trade wind flow, could affect portions of the
islands from time to time during the period.

&&

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

An area of showers and low level clouds will continue to move from
the east across the U.S. Virgin Islands and over the eastern half of
Puerto Rico through the morning hours. Some of these showers during
the overnight produced light to moderate rainfall amounts,
particularly over southeastern Puerto Rico. This activity is being
pushed over the region by a surface high pressure over the central
Atlantic. A moderate east to southeast wind flow will continue today
with sea breeze variations expected over western Puerto Rico just
before noon. This will aid in the development of afternoon showers
over portions of northwestern Puerto Rico. However, under the
influence of a mid to upper level ridge, mostly light to moderate
rainfall accumulations are expected.

An even drier air mass is expected on Monday and Tuesday as the
upper level ridge continues to hold over the region. Winds diminish
by Tuesday as a frontal boundary stalls over the Atlantic waters
above 22N and the surface high over the central Atlantic weakens.
Fair weather conditions are expected each day, with the exception of
isolated showers developing over northwestern Puerto Rico during the
afternoon hours.

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

Benign weather pattern is expected to continue during the long
term period as the aformentioned mid to upper-level ridge will
continue to hold firm across the eastern Caribbean. This will
continue to devoid most of the atmosphere above 700 mb of
moisture. As a result, fair weather conditions will prevail across
the region most of the period. Having said that, patches of low-
level moisture embedded within the trade wind flow could move over
the region from time to time. This could result in brief episodes
of showers over the region, however, any rainfall accumulations
should be light.

&&

.AVIATION...Mainly VFR conditions are expected to prevail during the
next 24 hours across all terminals. However, trade wind showers
could move at times across TIST/TJSJ/TJPS through 15z. Brief shra
possible in the afternoon in and around TJBQ. ESE winds will
continue between 10-15 kt with sea breeze variations after 14z.


&&

.MARINE...Rough seas between 5 and 8 feet will continue through
tonight across the regional waters due to fresh trade winds.
Therefore, small craft advisories will continue across most of the
regional waters. Seas below 7 feet are expected across all of the
regional waters by early Monday as the trade winds weaken. High
risk of rip currents will continue across most of the north
facing beaches of Puerto Rico, Culebra, and Saint Thomas.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 86 73 / 40 10 0 10
STT 86 75 87 73 / 50 20 10 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
458 AM AST Mon Dec 17 2018

.SYNOPSIS...Ridge aloft will keep a dry air mass over the region
throught the week. This will promote fair weather conditions
across Puerto Rico and the U.S. Virgin Islands. No significant
rainfall is expected during the next several days. Winds will
diminish through mid week as a frontal boundary stalls north of
the region and a surface high over the central Atlantic moves
further east. Another surface high behind the front will increase
winds once again during the second part of the week.


&&

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

A dry and stable air mass is expected to prevail across the forecast
area today and Tuesday. Precipitable water values are expected to
range between 0.80 and 1.00 inches, which would be near 2 standard
deviations below normal for this time of the year. In addition,
relative humidity values between the 850 and 700 mb layer are
expected to be below 50%. These two factors alone suggest that the
environment will be very hostile for shower development. Therefore,
most areas across the region should experience rain-free conditions.
If any showers do manage to develop, the area that would most likely
see some activity would be across northwest PR during the afternoon
hours due to sea breeze influence and diurnal heating. Either way,
with the very dry air mass in place, any showers that do manage to
develop should be brief and lead to very light accumulations.

On Wednesday, a patch of low-level moisture embedded within the
trade wind flow is set to move over the region. Therefore, an
increase in shower activity is possible. However, given that the
synoptic pattern continues to feature a mid to upper-level ridge
maintaining the mid to upper-levels of the atmosphere very dry, any
showers that do develop should be brief and lead to minor rainfall
accumulations.

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

An upper level ridge will continue to dominate the region through
the long term period. Another drier air mass is expected to move
from the east on Thursday and linger through Saturday morning,
keeping moisture below 850 mb. This will limit shower activity
across the islands. Moisture increases to 700 mb on Saturday
afternoon and continues through early next week. A return to light
passing showers across the USVI and eastern PR during the night
time and early morning hours, followed by diurnally induced
afternoon showers over western PR can be expected during this
period. However, no significant rainfall accumulations are
expected at the moment.


&&

.AVIATION...VFR conditions are expected to prevail across all
terminals throughout the forecast period. A few SHRA may affect
TJBQ and TJMZ terminals after 17/16Z. Low-level winds will be
mainly from the SE between 10 and 15 knots with sea breeze
variations developing after 17/14z.


&&

.MARINE...Small crafts should exercise caution today due to seas
up to 6 feet across the Atlantic waters and Caribbean Passages.
East to southeast winds will prevail between 10-15 kt. Winds and
seas will gradually diminish through Wednesday. A long period
northerly swell is expected to enter the Atlantic waters during
the end of the work week. A surface high pressure will increase
winds once again on Thursday.

There is a risk o rip currents for the northern beaches of Puerto
Rico and Culebra today due to a fading northerly swell.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 73 85 74 / 10 0 0 20
STT 87 72 87 74 / 10 0 10 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
411 AM AST Tue Dec 18 2018

.SYNOPSIS...A mid level high pressure will dominate the local
weather conditions through next week. Precipitable water content
is forecast to remain well below normal values for the next
several days. Although patches of low level clouds and associated
moisture could move at times across the islands, a fair weather
pattern will prevail.


&&

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

Dry weather conditions will once again prevail for today as
precipitable water values will be near 1 inch, if not slightly
lower, with relative humidity values in the 850-700 mb layer below
50%. Therefore, most areas should observe rain-free conditions.

On Wednesday, a patch of low-level moisture will arrive allowing for
better moisture profile in the low-levels. Therefore, compared to
today and yesterday, more shower activity is expected with the USVI
and the northern half of Puerto Rico having the best chance of
observing some showers. No significant rainfall accumulations are
expected as the mid to upper-level of the atmosphere will continue
to be very dry and thus the showers that do form should be short-
lived. Therefore, only expecting light rainfall amounts.

By Wednesday night into the day on Thursday, another area of drier
air will move over the region with precipitable water values once
again dropping to near 1 inch. Therefore, shower activity will once
again be very limited with mainly fair weather conditions expected.

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

Mid level ridge will remain over the region through the weekend
while slowly moving into the western Caribbean by Tuesday. This
will keep a fairly stable atmosphere and limit shower activity
across Puerto Rico and the U.S. Virgin Islands. However, a ridge
over the central Atlantic will push trade wind showers across the
region from time to time. This low level moisture combined with
daytime heating and sea breeze variations over western PR could
lead to isolated showers developing during the afternoon hours.
Regardless, no significant rainfall amounts are expected at this
moment during the long term period.


&&

.AVIATION...VFR conditions are expected to prevail across all
terminals throughout the forecast period. Low-level winds will
continue from the E-SE between 10 and 15 knots with sea breeze
variations developing after 18/14z.


&&

.MARINE...Tranquil marine conditions are expected for the next
few days. Light to moderate east to southeast winds will continue
across the region. Seas will increase on Thursday and Friday due
to a northerly swell. Also, a surface high pressure moving into
the central Atlantic will increase the trade winds during this
period and choppy seas are expected across most of the waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 74 86 74 / 0 20 40 20
STT 84 74 85 74 / 10 30 40 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
358 AM AST Wed Dec 19 2018

.SYNOPSIS...Although a high pressure system will continue to
transport occasional patches of low-level moisture across the
forecast area, mostly fair weather conditions are expected to
prevail through next week. Cloud clusters and showers streaming
over the waters into windward areas during the overnight and early
morning hours, as well as shower development over the interior
and western Puerto Rico each afternoon remains possible.
Nevertheless, no significant rainfall accumulation is expected.


&&

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

A broad mid level high pressure over the region will promote fair
weather conditions through the short term period. A weak front will
linger north of the region while a surface high continues to move
further into the eastern Atlantic. This will promote light winds
today. Winds are expected to increase on Thursday and Friday as a
surface high pressure exits the mid-Atlantic coast of USA later
today and moves into the central Atlantic by Friday morning.

An area of showers and low level cloudiness is currently moving
between the Leeward Islands and the U.S. Virgin Islands. This brief
surge in moisture will lead to passing showers across the USVI and
the eastern sections of PR through the morning hours and aid in the
development of afternoon showers over el Yunque area and across
portions of the interior and western PR. Rainfall amounts should be
light to moderate. Drier air will move overnight before another
pulse of moisture moves across the Caribbean waters on Thursday
afternoon. Under a more east to southeast wind flow, light showers
are expected to develop from streamers off the USVI and over
northwestern PR. A drier air mass will once again encompass the
region from the east on Friday and mostly rain free conditions will
prevail across the islands.


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

A mid level high pressure will remain north of the islands through
late Saturday before slowly moving and extending westward over
Bahamas and Greater Antilles by Sunday into Monday. This system
will then remain and dominate the region through midweek,
maintaining a trade wind cap and supporting mostly fair weather
conditions and limited shower activity across Puerto Rico and the
U.S. Virgin Islands. At the surface, a high pressure over the
central Atlantic will continue to transport patches of low- level
moisture into the region. This will result in trade wind showers
streaming over the waters into windward areas of the islands
during the overnight and morning hours, followed by isolated
shower activity developing across the interior and western Puerto
Rico due to local and diurnal effects each afternoon. No
significant rainfall accumulations are expected with any shower
activity that develops or affects the local islands.


&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals through the forecast period. However, SHRA possible this
afternoon in and around TJSJ/TJMZ/TJBQ. East winds will continue
near 10 kt with sea breeze variations after 14z.


&&

.MARINE...Tranquil marine conditions are expected today and
tonight with winds between 10-15 knots and seas ranging between 1
to 5 feet. Winds and seas are forecast to increase on Thursday, as
a northerly swell invades the local waters and a high pressure
builds over the region on Thursday through Friday. As a result,
Small Craft Advisories may be required. Tranquil marine
conditions will return on Saturday.


&&

.FIRE WEATHER...Although recent observations show that KBDI and
10-hour fuel moisture continue at critical levels (>=550 and <=10,
respectively) and relative humidities are forecast to drop in the
low 40%, winds are expected to remain below critical levels
today. As a result, a moderate fire danger risk is expected today,
particularly for the southern plains of Puerto Rico. If this
drying pattern continues, a high fire danger risk can be expected
and a Fire Danger Statement or Fire Danger Warning may be issue
during the next few days.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 74 86 74 / 30 20 0 20
STT 84 74 84 74 / 30 10 10 30

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
435 AM AST Thu Dec 20 2018

.SYNOPSIS...Patches of low-level moisture embedded in moderate to
locally fresh easterly trade winds will continue to move across
the forecast area from time-to-time. This will result in cloud
clusters and passing showers streaming over the waters into
windward areas of the islands. The presence of a mid/upper level
high pressure will limit the intensity and coverage of any shower
activity, resulting in mostly fair weather conditions and minimal
rainfall accumulations across the local islands through the
forecast period.


&&

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

A pocket of moisture moving across the islands will continue to
result in passing showers across the local waters and windward
sections through early this morning. However, satellite imagery
depicted a dry airmass filtering from the east across the islands,
which is expected to limit shower activity throughout the day.

Easterly trades are expected to increase somewhat as a surface high
pressure drift into the central North Atlantic Ocean through the
upcoming weekend. A frontal boundary which is forecast to move
across the western Caribbean and Atlantic ocean by Friday, will
linger off to the west and northwest of the local islands. But, a
drier than normal airmass and a mid/upper level high pressure will
promote fair weather conditions through the short term period.
However, the trade winds will bring pockets of moisture from time to
time, which will lead to fast moving passing showers across the
windward sections of Puerto Rico and the U.S. Virgin Islands.
Meanwhile, the high pressure aloft will make difficult afternoon
convection over the western and interior sections of Puerto Rico.
Rainfall amounts should be light to moderate.

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

Although a surface high pressure system moving eastward into the
north central Atlantic will continue to bring patches of low-
level moisture into the forecast area from time- to- time, a mid
level high pressure will remain over the region. As a result,
mostly fair weather conditions will prevail across Puerto Rico and
the U.S. Virgin Islands. Clusters of clouds and showers streaming
over the waters into windward areas of the islands, as well as
limited shower activity developing over the interior and western
Puerto Rico due to local and diurnal effects each afternoon
remains possible. Nevertheless, no significant rainfall
accumulations are expected.


&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals through the forecast period. However, -SHRA/SHRA possible
this afternoon in and around TJSJ/TJMZ/TJBQ/TIST/TISX. Light to calm
and variable winds, increasing at 10 to 15 knots out from the east
with higher gusts and sea breeze variations after 20/13z.


&&

.MARINE...Choppy marine conditions are expected across the
Atlantic waters and local passages today with seas up to 6 feet
and east winds up to 15 knots. Elsewhere, seas up to 5 feet are
expected. Winds and seas are forecast to increase this evening,
as a northerly swell invades the local waters and a high pressure
builds over the region. As a result, Small Craft Advisories are in
effect, particularly for the offshore Atlantic waters where seas
between 5 and 7 feet are expected. A high rip current risk is in
effect for beaches along the north coast of Puerto Rico, Culebra,
and Saint Thomas. Marine conditions will improve during the
weekend.


&&

.FIRE WEATHER...A drying weather pattern is expected to continue
today. The forecast calls for mostly clear skies with no
significant shower activity and relative humidity to drop into the
upper 40s and low 50s. Although winds are forecast to barely meet
fire weather criteria, recent KBDI and 10-hour fuel moisture
values suggest that elevated fire weather conditions can be
expected today, particularly across the southern coastal plains of
Puerto rico where KBDI values range between 590 and 650. As a
result, a Fire Danger Statement has been issued.


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
435 AM AST Fri Dec 21 2018

.SYNOPSIS...Patches of low-level moisture embedded in moderate
easterly trade winds will continue to move across the forecast
area from time-to-time. However, the presence of a mid level high
pressure will limit the intensity and coverage of any associated shower
activity, resulting in mostly fair weather conditions through the
forecast period. A slight increase in moisture content and shower
activity is expected during the weekend, but no significant
rainfall accumulations are expected. A seasonal and relatively
dry weather pattern will return next week.


&&

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

Seasonal weather pattern had prevailed this week and will continue
through much of the forecast period. Mid/upper level ridge pattern
will hold aloft inducing a strong trade wind cap through the short
term period. At the surface, a high pressure drifting into the north
central Atlantic Ocean will promote a breezy trade wind flow across
the region. In addition, a frontal boundary which is forecast to
move across the western Caribbean and Atlantic ocean today, will
linger off to the west and northwest of the local islands.

Model guidance continue to suggest a drier than normal airmass
through the short term period. However, trade wind perturbations
will bring pockets of moisture/clouds at times, which will lead to
fast moving passing showers across the windward sections of Puerto
Rico and the U.S. Virgin Islands each day. However, moisture content
and shower activity should increase somewhat by the upcoming
weekend. Meanwhile, the high pressure aloft will make difficult
vertical development and afternoon convection over the western and
interior sections of Puerto Rico, but should not be ruled out.
Rainfall amounts should be light to moderate.

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

Patches of low-level moisture embedded in the trade winds will
continue to move across the forecast area through the long term
period. As a high pressure system exists the eastern coast of the
United States and moves over the western Atlantic late Wednesday
night into Thursday, there will be a slight increase in the
moisture transported with these patches. However, a mid level
high pressure that is forecast to hold over the region will limit
the intensity and coverage of any shower activity that develops
over the forecast area. As a result, mostly fair weather
conditions will prevail across Puerto Rico and the U.S. Virgin
Islands. No significant rainfall accumulations are expected.


&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals through the forecast period. However, -SHRA/SHRA possible
this afternoon in and around TJSJ/TJMZ/TJBQ/TIST/TISX. Light to calm
and variable winds, increasing at 10 to 15 knots out from the east
with higher gusts and sea breeze variations after 21/13z.


&&

.MARINE...Choppy/Rough marine continue will continue through at
least this evening across the offshore Atlantic waters and the
Anegada Passage with seas up to 7 feet. Thus, Small Craft
Advisories remain in effect. Small craft operators should exercise
caution across nearshore Atlantic waters and Mona Passage due to
seas up to 6 feet. Elsewhere, seas up to 5 feet are expected.
Moderate easterly winds will prevail today and on Saturday, but
are forecast to increase on Sunday into early next week. A high
rip current risk is in effect for beaches along the north coast of
Puerto Rico, Culebra, and Saint Thomas. Marine conditions will
improve during the weekend.


&&

.FIRE WEATHER...Relative humidity values are expected to drop
into the mid 40s to low 50s today. Although winds are forecast to
range between 10-15 mph, recent KBDI and 10-hour fuel moisture
observations show that a drying pattern continues to dominate the
local islands and given that no significant wetting rains are
expected, elevated fire weather conditions can be expected. As a
result, a Fire Danger Statement has been issue for today,
particularly for the southern coastal plains of Puerto Rico where
KBDI values are near or above 600.


&&

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