Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
151 PM AST Mon Nov 7 2016

.SYNOPSIS...A shear line over the area will weaken as the frontal
boundary to the northeast continues east. Good moisture levels
will continue to decline ever so slightly during the next 10 days,
allowing showers and thunderstorms to persist--mainly in the
afternoons over the interior.

At mid and upper levels...A long wave trough will pass over the
area on Tuesday night. High pressure will then ridge into the area
and dominate the Caribbean yielding northwest flow over the local
area. Mid level moisture will diminish beginning Tuesday night

At lower levels...A weak trough will persist over the local area
until Friday when a weak easterly wave will move through. By the
weekend easterly trade winds will resume and high pressure will
ridge over the area by mid week next week.

&&

.DISCUSSION...The area was mostly cloudy early this morning and
showers and thunderstorms persisted over the caribbean waters
associated with a shearline extending out of a strong low in the
western Atlantic. The shear line will make a little easterly
progress but ultimately dissipates and reforms well northwest of
the local area in 48 to 72 hours. Moisture remains rich and this
will continue showers and thunderstorms over the local waters and
during the afternoons and evenings over Puerto Rico. Some showers
will also affect the U.S. Virgin Islands. Currently the GFS
depicts a dry band moving in from the southeast across Saint Croix
Tuesday night and over Puerto Rico on Wednesday. Nevertheless some
shower activity is still expected Wednesday with lesser coverage
and accumulations.

Currently showers are forming and dissipating fairly rapidly in
slow moving bands. This will bring urban and small stream flooding
to both northeast and northwestern Puerto Rico. Showers will reach
the northern Virgin Islands later this evening, but may stall
before moving into Saint Croix owing to the advance of drier air
from the southeast as forecast by the GFS and observed in the
MIMIC product.

Other than the trough moving through at lower levels Friday
morning, few significant features are noted, other than the
persistent boundary that remains north and northwest of the area
separating the moist tropical air from the modified polar air. New
fronts enter the area and reinforce the boundary without
significant progress of the boundary toward Puerto Rico and the
U.S. Virgin Islands.

&&

.AVIATION...Brief MVFR due low cig and SHRA/Isold TSRA ovr and vcty
TJBQ/TJSJ/TJNR/TJPS til 07/22z. SCT-BKN cld lyrs nr FL020...FL040...
FL100 across the entire flying area with BKN-OVC cigs en route btw
PR and Nrn Leewards. Isold max tops FL350-FL400 W/TSRA. Winds blo
FL200 fm S-SE at 5-15 kts bcmg westerly and incr w/ht abv to MAX
WND 50-60 kts nr FL350. Sfc wnd mainly lgt/vrb except for sea
breeze variations.

&&

.MARINE...Tranquil seas in the Atlantic will be invaded by medium
period swell from the low currently in the western Atlantic and
will bring 7 to 8 foot seas, a high risk of rip currents and surf
up to 8 or 9 feet. Seas will return to 5 feet or less by Friday.
Small craft advisories are expected by Wednesday 9 November.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 77 86 77 89 / 40 20 20 20
STT 77 86 77 87 / 40 30 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
538 AM AST Tue Nov 8 2016

.SYNOPSIS...Upper level trough will continue affecting the local
area through Wednesday. Upper level ridge will build across the
area Thursday. Another trough will approach the local area Friday
and Saturday.

&&

.DISCUSSION...Another active day is in store for Puerto Rico,
mainly this afternoon. An upper level trough continues across the
local area. This trough is producing scattered to numerous showers
with thunderstorms across the local waters. For this afternoon,
daytime heating and local effects will combine with favorable
upper level atmospheric conditions (the trough) to produce
scattered to numerous showers with thunderstorms across most of
the area. Due to light winds at the surface, some urban flooding
can be expected.

This trough is expected to move away from the area Thursday, which
will lead to a decrease in shower activty across the area.
However, this relatively drier air will not last for too long. For
Friday, another mid to upper level perturbation is expected to
approach the local area from the east. As a result, periods of
showers and thunderstorms can be expected for Friday and Saturday
afternoon.

&&

.AVIATION...Unstable/humid conds continues. SHRA expected across
TIST/TISX/TNCM/TKPK. SHRA/TSRA are expected to increase late in the
morning into the afternoon over mainland PR/USVI. Some of this SHRA
can produce brief MVFR or even IFR conditions between 08/16-22z at
TJSJ/TJMZ/TJPS/ TJBQ/TIST. Across the rest of the local flying area
VCTS/VCSH are expected. Winds will continue very light but mostly
from the east, increasing at around 10 knots with higher gusts and
sea breeze variations after 08/13Z.

&&

.MARINE...Seas up to 5 feet and winds up to 10 knots are expected
over the coastal waters. Moderate risk of rip current are expected
along the north facing beaches of Puerto Rico and Saint Thomas in
the U.S. Virgin Islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 76 87 78 / 40 30 30 40
STT 87 77 87 78 / 30 30 30 40

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
206 PM AST Tue Nov 8 2016

.SYNOPSIS...Upper trough will continue to move west to east over
the forecast area through Wed afternoon. Upper ridge builds across
the eastern Caribbean through the weekend. At lower levels,
a frontal boundary north of the area and moisture across the
eastern Caribbean will linger for the next several days. A weak
easterly wave east of the leeward islands will continue to move
east and increase moisture on Friday.


&&

.DISCUSSION...Scattered to numerous showers and thunderstorms
developed early in the afternoon hours across the northern half of
PR and around the northern U.S. Virgin Islands. This activity was
induced by the combination of the upper trough and local effects.
As ridge builds aloft tomorrow, convection is not expected to be
as widespread as previuos days. However, diurnally induced
afternoon showers and thunderstorms are expexted each day.

A pulse in moisture is expected on Friday as a short wave trough
over the Atlantic waters and easterly perturbation moves across
the forecast area. A southeasterly steering wind flow is expected
for the next several days as frontal boundary lingers just over
the offshore Atlantic waters.


&&

.AVIATION...Aftn convection still fcst over the central mountain
range and nrn half of PR to produce periods of SHRA/TSRA with brief
MVFR/psbl IFR conds til at least 08/22z. Sct-Nmrs convective
Activity in and around TJSJ/TJMZ/TJPS/TJBQ/TIST with isold SHRA/or
TSRA psbl vcty TISX. Across the rest of the local flying area
VCTS/VCSH are expected btw islands. Winds will light and variable
except for local sea breeze variations til 08/23z.


&&

.MARINE...A large and long period northerly swell due to a surface
low pressure over the Western Atlantic will affect the local
waters on Wed-Thu. Small craft advisories will be in effect for
much of the Atlantic exposed waters due to hazardous seas between
7-8 feet and occasionally higher. This swell will result in large
breaking waves along the Atlantic coastline of the islands that
will cause life threatening rip currents and rough surf
conditions. Seas will slowly subside late Thursday into Friday.
Winds will continue east-northeast across the Atlantic waters at
5-15 knots overnight into Wednesday and east-southeast across the
Caribbean waters...becoming more easterly through the rest of the
week.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 87 78 88 / 30 30 40 40
STT 77 87 78 87 / 30 30 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
606 AM AST Thu Nov 10 2016

.SYNOPSIS...
A mid-upper level ridge is expected to build across Eastern
Caribbean today into Friday. An upper level trough is forecast to
move across Western Atlantic and off to the North of the islands
Friday through Saturday. At lower levels, A surface trough will
move across the region this afternoon into early Friday,
increasing cloud cover and the potential for shower and
thunderstorm activity. A frontal boundary will move eastward
across the Atlantic Ocean and will lingered to the north of the
region during the weekend. Plenty of tropical moisture will pool
over the region during the next few days.

&&

.DISCUSSION...
Limited shower activity was observed over Mainland Puerto Rico
and the U.S. Virgin Islands overnight. Most of the showers were
detected across the surrounding waters, and a few of them affected
the windward areas from time to time. In general, calm weather
conditions with pleasant temperatures prevailed overnight and
early this morning across the U.S. Virgin Islands and Puerto Rico.

A surface low will continue its way into the region this morning,
passing mostly south of the local islands this afternoon into
early Friday. As this feature moves near the region, an overall
moist environment will persist for the next couple of days.
This moisture combined with local and diurnal effect will lead to
afternoon convection mainly along and to the west of the
Cordillera Central and downwind from the Islands of Vieques,
Culebra and the U.S. Virgin Islands. In addition, due to the
previous rainfall events the soils are already saturated, and any
persistent heavy rainfall will lead to Urban and Small stream
flooding across parts of the island, as well as quick rises in
water level along rivers and streams.

Although, atmospheric conditions does not represent the best
dynamic for enhance convection, plenty of tropical moisture will
combined each day with the local and diurnal heating to produce
afternoon convection across the islands.

&&

.AVIATION...
SHRA/TSRA are expected to increase late in the morning into the
afternoon over western interior and northwestern PR. As a result,
brief MVFR or even IFR conditions between 10/16-22z at TJMZ and
TJBQ with mountain obscurations can be expected. Across the rest
of the local flying area VCSH are expected. Winds will continue
mostly from the east, increasing at around 10 to 15 knots with
higher gusts and sea breeze variations after 10/13Z.

&&

.MARINE...
Seas up to 10 feet will continue across the Atlantic waters and
Anegada Passage, as a long period northerly swells will continue
to affect the regional waters today. Therefore, mariners can
expect hazardous seas, life threatening rip currents and rough
surf across these waters and along the Atlantic coastline of the
islands through at least this evening. Additional information is
provided in the local marine products produced by your Weather
Forecast Office-San Juan.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 77 88 78 / 30 20 20 20
STT 87 78 87 78 / 30 20 20 20

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
548 AM AST Fri Nov 11 2016

.SYNOPSIS...Polar trough across the western Atlantic will continue
to move eastward and north of the forecast area today and Saturday.
As this feature pulls away, the ridge aloft is expected to briefly
strengthen during the upcoming weekend. An easterly disturbance/
tropical wave will continue to move away from the local islands
throughout the day. The next surface boundary will reach the
local islands early next week.

&&

.DISCUSSION...Partly cloudy skies prevailed across the local islands
overnight and early this morning. Passing showers were observed
across the local waters with a few of them affecting land areas.
Minimum temperatures ranged from the upper 60s to low 70s in the
mountains to the mid to upper 70s in lower elevations. Winds were
light and variable.

The proximity of a trough aloft and plenty of low level moisture
associated with departing easterly disturbance/tropical wave will
continue to result in passing showers across windward areas in the
morning followed by locally induced showers and thunderstorms along
the northern slopes of Puerto Rico including portions of the San
Juan Metro Area this afternoon under an east southeast wind flow.

As the trough pulls away, the ridge aloft is expected to briefly
strengthen. However this feature is not strong enough to suppress
diurnal convection during the upcoming weekend. Therefore under
easterly winds and precipitable water values back in the normal
range, expect showers and isolated thunderstorms across the
western interior and west Puerto Rico Saturday and Sunday. At
least through early next week, a few passing showers are expected
across the U.S. Virgin Islands from time to time as well as
downwind of local islands.

The chance of showers and thunderstorms are expected to increase
across the forecast area Monday and Tuesday as a surface boundary
reaches the local islands.

&&

.AVIATION...Mostly VFR conditions expected across most of the local
taf sites with VCSH across TJSJ as well as the USVI and Leeward
islands TAF sites. Brief periods of MVFR conditions possible across
TJMZ and TJBQ in SHRA/TSRA from 11/16z through 11/22z. SFC winds
will remain from the east southeast at less than 10 knots early
morning, increasing to around 15 knots after 11/13Z with sea breeze
variations.

&&

.MARINE...Marine conditions will continue to improve across the
local waters as swell action subsides. The local buoy network
indicates seas around 6 feet and subsiding. As a result the Small
Craft Adv has been cancelled but the high risk of rip currents
continues along the Atlantic shorelines of Puerto Rico.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 88 79 / 30 20 20 30
STT 88 78 88 78 / 40 10 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
206 PM AST Fri Nov 11 2016

.SYNOPSIS...A moist air mass continues over the area. A weak and
slow moving frontal boundary will shift over the area on Monday or
Monday night. Slight drying mid-week but we return to more
showers later.

At upper levels...High pressure over the Caribbean will prevent
short waves passing from west to east to our north from reaching
Puerto Rico and the U.S. Virgin Islands. A weak trough will pass
through on Saturday morning. When a strong trough digs into the
western Caribbean next Tuesday, the high pressure ridging north
into the U.S. Virgin Islands will keep the trough from reaching
the area through at least 21 November.

At mid levels...High pressure continues over the Greater Antilles
through mid week next week, then high pressure dominates Puerto
Rico while a trough digs into the Western Caribbean. Mid-levels
become modestly moist with a drier period intervening between
Tuesday and Thursday of next week.

At lower levels...A saddle is found just north of Puerto Rico
where high pressure meets the trough extending north out of the
Caribbean across the local area. The focus of the trough shifts to
the east over the weekend causing the winds to become east
northeast. Cooler air from the north attempts to enter the area
but the boundary stalls over us Monday or Monday night bringing
more showers. High pressure then noses into the northeast
Caribbean and Hispaniola mid week next week.

&&

.DISCUSSION...An area of showers is spreading east across much of
Puerto Rico this afternoon while flow moves the cells to the
northwest across the area. Moisture continues over the area, but
the showers will become more frequent over the local waters
tonight. Winds will shift to the northeast on Monday and some
showers will form more on the northeast side of the islands Monday
morning. A frontal band associated with the low pressure in the
western Atlantic and hovering to our north and northwest, will
return Monday and Tuesday to bring showers and possibly
thunderstorms--mainly to Puerto Rico. Moist flow from the east
will continue to bring scattered passing showers through the
remainder of the upcoming week.

&&

.AVIATION...Mostly VFR conditions expected across all terminals.
However, SHRA/TSRA across the interior and NW quadrant of PR could
create MVFR conds at TJBQ/TJMZ through 22z. Isolated TSTM near TJSJ
could still develop this afternoon. Showers over the waters are
expected to continue overnight with tops around FL150-200. Sfc winds
overnight light and variable increasing from the east aft 12/13
around 10 kts.

&&

.MARINE...Northerly swell will diminish through Saturday night in
the Atlantic. Then seas will gradually increase through Tuesday.
At this time small craft advisories are not expected, but models
may be under-forecasting by a foot so there is a possibility in
the Atlantic on Tuesday for 7 foot seas. The Caribbean remains
generally tranquil with seas of 5 foot or less.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 79 87 79 88 / 40 20 30 30
STT 78 88 78 88 / 20 20 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
525 AM AST Sat Nov 12 2016

.SYNOPSIS...A seasonable weather pattern is expected to prevail
across the local islands during the next several days with trade
wind showers in the morning and late evening hours across E PR/USVI
and locally induced showers and thunderstorms in the afternoon
across W PR.

&&

.DISCUSSION...Partly cloudy skies prevailed across the local
islands overnight and early this morning with passing showers
observed across the local waters as well as windward areas.
Minimum temperatures ranged from the upper 60s to low 70s in the
mountains to the mid to upper 70s in lower elevations. Winds were
light and variable.

A ridge aloft will hold across the forecast area during the next
several days. However, at least through early next week, this
feature is not strong enough to suppress afternoon shower/thunder
development. A significant strengthening is expected next week,
and therefore could delay the onset of afternoon showers and
thunderstorms or even suppress shower/thunder development. As a
result, continue to expect passing showers across eastern Puerto
Rico and the U.S. Virgin Islands in the morning and late evening
hours, followed by locally induced showers and thunderstorms
across western sections of Puerto Rico under easterly winds and a
relatively moist airmass Sat-Tue. In fact, precipitable water
values are expected to remain near or slightly above the normal
values through midweek next week. Moisture advection Mon-Tue is
mainly associated with a weakening surface front north of the
area.

As the aforementioned ridge aloft strengthens, available moisture
is expected to erode. This will result in a fair and stable
weather pattern across the local islands Wed-early Fri. Showers
and thunderstorms are expected to increase across the forecast
area by the end of the next week as a surface boundary reaches
the local islands.

&&

.AVIATION...VFR conds expected to prevail across all TAF sites
through at least 16z. Cloud cover is expected to increase aft 15z
across PR/USVI. Mnt obsc as well as SHRA/TSRA are expected btwn 15z-
23z over the Interior and W-PR, affecting TJBQ/TJMZ. Also, showers
are possible downwind from El Yunque to affect TJSJ. Sfc winds
increasing from the east-southeast aft 14z around 10 kts and with
sea breeze variations.

&&

.MARINE...Tranquil marine conditions will continue to prevail
across the local waters during the next several days with seas
below 5 feet and a moderate easterly wind flow.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 78 87 78 / 30 30 30 20
STT 88 78 86 78 / 30 30 30 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
211 PM AST Sat Nov 12 2016

.SYNOPSIS...East southeast flow will turn east northeast to
northeast by Monday. A weak shearline just north and northwest will
hold moisture over the area, but overall moisture will diminish
through Wednesday. No major features are expected through late
next week.

At upper levels...High pressure over the western and central
Caribbean will shift over the area and ridge northward.

At mid levels...High pressure over the Greater Antilles will
become oriented toward the northeast-southwest Tuesday through
Wednesday and remain over or south of the area through mid week
the following week. Mid levels will have limited moisture and
light flow through the next 10 days.

At lower levels...Low pressure to the south and a weak ridge
across the sub-tropical Atlantic will continue through next week
with moderate trade wind flow. A broad trough over the western
tropical Atlantic on Monday will move westward, but low pressure
developing north of Hispaniola on Thursday will absorb it as it
moves through the area.

&&

.DISCUSSION...Showers have formed over the southwestern portion of
the island over higher terrain. High clouds have blocked some of
the heating in western Puerto Rico and further development may be
delayed and diminished. More showers are expected however as
moisture continues at fairly rich levels. The 12/12z sounding came
in at 2.04 inches and this is up for 24 hours, even though it is
down for the last 12 hours.

Low level flow will gradually become more northeasterly. The GFS
has been changing its solution and the latest solution may not
verify. Nevertheless the boundary to the north does approach the
area even as the moisture with it is now being depicted as
declining. The GFS is also developing a weak low just above the
surface that will also help anchor the boundary just north of us
for a while. With no major features and shifting model solutions
the best forecast is for scattered showers becoming more prevalent
on the north coast early next week. Slightly cooler temperatures
during the day are also expected in the greater San Juan
Metropolitan area. Afternoon convection will continue at reduced
levels.

As a result of the removal of a strongly digging long wave trough
over the western Caribbean, the GFS is now strongly developing a
tropical storm in the southwest Caribbean. This feature seems to
be a more reasonable solution.

&&

.AVIATION...Mainly VFR conditions to prevail through the forecast
period. Afternoon SHRA/TSRA focus has changed more to the western
interior/southwest quadrant of PR. Therefore the flying area
impacted should be between TJPS/TJMZ. Streamers developing off the
USVI created VCSH and tempo -RA during the past hour and are
expected to continue for the next 2-3 hours. VCSH expected mainly
at TJSJ now. Low level east winds should continue at 8-15 kts,
light and variable winds expected at sfc overnight.

&&

.MARINE...No strong features for a while in the Atlantic that will
drive swell into the local area so seas on both sides of Puerto
Rico and the U.S. Virgin Islands are expected to remain 5 feet or
less through 18 November.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 78 87 78 87 / 30 30 20 20
STT 78 86 78 86 / 30 30 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
530 AM AST Sun Nov 13 2016

.SYNOPSIS...Trade wind showers during the morning hours across
E PR/USVI followed by locally induced afternoon showers and
thunderstorms across W PR and downwind of the USVI will continue
to prevail through Tuesday. A stable weather pattern is expected
to prevail across the forecast area Wednesday through Friday under
strengthening ridge aloft. A surface boundary will reach the local
islands the upcoming weekend.

&&

.DISCUSSION...A mid to upper level ridge will hold across the
forecast area during the next several days. However, at least
through Tuesday, this feature is not strong enough to suppress
shower/thunder development. A significant strengthening is expected
by the end of the week, and therefore could delay the onset of
afternoon showers and thunderstorms or even suppress it. As a
result through Tuesday, continue to expect passing showers across
eastern Puerto Rico and the U.S. Virgin Islands in the morning and
late evening hours, followed by locally induced showers and
thunderstorms across western sections of Puerto Rico under
easterly winds and a relatively moist airmass. In fact,
precipitable water values are expected to remain near or slightly
above the normal values through midweek. As the aforementioned
ridge aloft strengthens, available moisture is expected to erode.
This will result in more stable weather conditions across the
local islands Wed-Fri. Showers and thunderstorms are expected to
increase across the forecast area the upcoming weekend as a
surface boundary reaches the local islands.

Based on NHC, A broad area of low pressure is expected to gradually
form over the southwestern Caribbean Sea during the next few
days. Environmental conditions are forecast to be conducive for
slow development of this system, and a tropical depression could
form later this week while the low drifts northward or northeastward.

&&

.AVIATION...VFR conditions to prevail at least through 13/13z
across the local terminals with VCSH due to ISOLD/SCT SHRA.
SHRA/TSRA developing across PR after 13/16Z to affect the vcnty of
TJSJ, TJPS, TJMZ, and TJBQ. TJMZ may observe TEMPO MVFR conds. Low
level east winds should continue at around 5 kts through 13/13Z,
increasing to 10-15 kts after 13/13Z with sea breeze variations
developing.

&&

.MARINE...Pulses of a moderate NNW swell will reach the local
Atlantic waters through today. This will keep seas 3-5 feet the
rest of the weekend. Then...seas will subside to 2-4 feet on
Monday. Tranquil marine conditions will prevail the rest of the
work week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 78 87 78 / 30 40 40 40
STT 88 78 86 78 / 20 40 40 40

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
158 PM AST Sun Nov 13 2016

.SYNOPSIS...easterly trade winds with moisture and troughiness
will continue in the local area with scattered showers. A cold
front is likely to drop into the forecast area next weekend to
increase shower activity and lower temperatures a few degrees.

At upper levels...High pressure will dominate the Caribbean Sea
until Friday night. A moderately strong trough will move off the
Atlantic coast of the United States this Wednesday. A low will
cut-off Thursday night or Friday and drop south causing the sub-
tropical jet to dip within 80-160 miles of Puerto Rico by Sunday.

At mid levels...High pressure over the Caribbean Sea will become
centered over Saint Thomas by Wednesday. A low will form as a
trough leaves the Atlantic coast of the United States near
Washington DC and dip to as close as 31 north Friday through
Sunday. Mid-level moisture is quite limited except for a
boundary-layer passage on Saturday.

At lower levels...A weakening trough/tropical wave near 52 west
will approach the Lesser Antilles early this week causing local
flow to remain mainly easterly. Low pressure just off of the
Florida coast will move quickly north in the western Atlantic.
Moderately strong high pressure will become stalled over the
eastern coast of the Untied States Thursday while that low
pressure returns to the south in the vicinity of 50 west. This and
the mid level low mentioned above will cause a cold front to move
into the forecast area on Saturday with increased moisture and
shower activity.

&&

.DISCUSSION...Moisture continued in easterly flow causing showers
to form from Humacao to Toa Baja. Some areas will receive more
than one inch in a narrow band. Other showers formed along the
Cordillera Central from Mayaguez to Coamo. Up to now thunderstorms
had not been observed.

Easterly flow will continue and prevailing moisture will drive
early morning passing showers as well as more active convection
over higher terrain and areas of local convergence during the
afternoons. A few thunderstorms will also remain possible.
Moisture continues over the area through Monday, decreases
slightly the first half of the work week and then increases
through Saturday with the approach of a cold front. The driest
weather of the next 10 days is promised Monday morning of next
week when precipitable water drops below 1 inch.

This is a likely scenario, but confidence in the models is
medium-low. The GFS has changed from a strong trough deepening
over the western Caribbean to a strong tropical low advancing on
Hispaniola late in the 15 day period to a tropical low moving
into the Pacific (13/06z run) and back to a weak tropical low
that approaches Jamaica. This leads to considerable uncertainty as
to whether the features necessary to bring the cold front this far
south will materialize. That said, although these are considerable
changes for the western Caribbean, they have not been
particularly significant for the local area as moisture and modest
instability will continue to bring scattered showers and warm
temperatures though much of the week.

&&

.AVIATION...SHRA/TSRA will continue to impact the flying area
of TJSJ/TJPS/TJBQ/TJMZ for the rest of the afternoon hours.
Mtn top obscd and tempo MVFR conds possible through 22z. Streamers
off the USVI will continue to create mainly VCSH with possible -RA at
TIST. Mainly VFR conditions expected after 23z through at least
14/16z. ESE low level winds are expected to become ENE after
14/00z around 9-15 kts. However, light and variable winds are
expected at sfc overnight.

&&

.MARINE...Seas will continue to diminish slowly through Monday,
increase slightly and then decrease until Friday. The approach of
a cold front will increase winds and seas, but small craft
advisories are no longer as certain.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 79 87 78 87 / 40 40 40 40
STT 77 86 78 86 / 40 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
459 AM AST Mon Nov 14 2016

.SYNOPSIS...Another round of locally induced showers and
thunderstorms are expected this afternoon across central and
western PR with a chance across southern PR as well.

Weakening tropical wave near 53W is expected to reach the Lesser
Antilles late Tuesday but the bulk of the moisture associated
should stay South of the local area. Overall pattern is expected
to keep easterly winds through this week until Saturday when a
frontal boundary approaches the area but stays to our north. High
pressure in the upper levels is dominating and will continue
through the workweek.

&&

.DISCUSSION...Scattered showers will continue to be expected
through the morning hours, mainly affecting the local waters, USVI
and eastern PR, but not leaving significant amounts of rainfall.
However, the available moisture and diurnal heating will once
again combine with the local effects and prevailing wind flow to
cause the development of showers and thunderstorms in the
afternoon across central and western PR with some of the showers
possibly affecting south and southwestern PR since there is a
slight NE component to the wind expected this afternoon...albeit a
weak wind. The soils are very saturated and any significant
showers will quickly become runoff, likely causing at least some
urban and small stream flooding.

There is so much available moisture that afternoon convection is
likely every afternoon mainly across the central and western
sections of PR. This means that little relief is seen in terms of
drying up the soils across these sectors. The pattern should
remain fairly constant until maybe this weekend when a frontal
boundary approaches the local islands from the north. At this time
it looks like the boundary will stay just to our north but the
long range models indicate that it will get close enough to
disrupt the easterly wind pattern and cause a shift to NE winds as
well as bring cloudiness to the local area, possibly bringing some
light to moderate rain and causing a decrease in daytime maximum
temperatures a few degrees.

&&

.AVIATION...VFR conditions to prevail at least through 14/12z across
the local terminals with VCSH due to ISOLD/SCT SHRA. TSRA developing
across West and South PR after 14/16Z to affect the vcnty of TJPS
and TJMZ. As a result...Brief MVFR conds are possible at TJMZ/TJPS
with mountain obscurations. Low level ENE winds should continue at 5-
10 kts overnight, increasing to 10-15 kts after 14/13Z with sea
breeze variations.

&&

.MARINE...Tranquil marine conditions expected to prevail for the
next several days with seas up to 4 feet today and Tuesday.
Winds over the local waters generally between 5 and 15 knots.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 78 87 78 / 40 40 40 40
STT 86 78 86 79 / 40 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
202 PM AST Mon Nov 14 2016

.SYNOPSIS...Ample moisture in east northeast to easterly flow will
keep passing showers during the nights and early mornings with
afternoon convection and heavier rain showers in the interior of
Puerto Rico during the afternoons and downstream from the larger
islands east of Puerto Rico, including Saint Croix, through the
next 7 days. Moisture reaches a minimum on Wednesday.

At upper levels...High pressure in the western Caribbean will
shift into the eastern Caribbean by Wednesday night. The ridge
will flatten out by Saturday as a jet brushes the area on Sunday
and strong low pressure deepens well north of the local area
Wednesday of the following week.

At mid levels...High pressure centered over Cuba will shift to
Puerto Rico and the Windward Islands by Wednesday as a strong
trough deepens off the coast of New Jersey and passes through
Florida. By the beginning of next week this low which moved as far
east as 65 west, will become absorbed into a much larger low
moving off the coast of the Eastern United States and will
dominate most of the western Atlantic.

At lower levels...Low pressure continues across the southern
Caribbean through much of the next 10 days. Higher pressure
remains north but a weak trough moves east through the area on
Thursday night and stalls over the Leeward Islands over the
weekend. Copious moisture will continue through much of the period
increasing toward the end of the week and into early next week.

&&

.DISCUSSION...Showers formed south of San Juan and in eastern
Puerto Rico around noon followed closely by showers over the
Cordillera Central in southwestern Puerto Rico. A few weak
streamers were noted downstream from Saint Croix and Saint
Thomas. Other showers were also noted in the outer Atlantic
waters. Showers are not expected to affect the Culebrinas basin
today as much as they did yesterday on account of the slight
backing of low level flow to the east. Similar conditions will
appear over the area tomorrow as moisture remains relatively rich
and morning heating will be possible for much of the rest of the
week.

The GFS model still wants to place a strong tropical cyclone up
to hurricane strength in the southwest Caribbean by early next
week. It has however been offering somewhat divergent solutions in
the last 24 hours, taking the system either into Nicaragua (14/06Z
run) or north toward the passage to the Gulf of Mexico (14/12Z
run). The final solution will likely bring a boundary that has
persisted to the northwest within a few hundred miles of Puerto
Rico and the U.S. Virgin Islands toward the end of the forecast
period on 24 November closer if not over the area. Until that
time we will remain in a more or less homogenous tropical airmass
with attendant diurnal showers.


&&

.AVIATION...SHRA/TSRA will affect the southern side of PR
resulting in MVFR conds and mountain obscurations in and around
TJPS and TJMZ thru 14/22z. VFR conditions will prevail at all TAF
sites from 15/02z through 15/14Z with VCSH due to ISOLD SHRA at
JSJ/IST/ISX. Easterly winds around 10 knots with sea breeze
variations.

&&

.MARINE...A slight rise in seas will abate Tuesday through Friday.
Northerly swell will cause seas to rise again on Saturday. Small
craft advisories may be needed in the outer Atlantic waters then.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 78 87 77 87 / 40 40 40 40
STT 77 87 77 87 / 30 30 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
408 AM AST Tue Nov 15 2016

.SYNOPSIS...Another round of locally induced showers and
thunderstorms are expected this afternoon across central and
western PR with possible isolated thunderstorms across portions of
the San Juan metropolitan area as well.

Weak tropical wave near 59W is expected to reach the Lesser
Antilles today but the bulk of the moisture associated should stay
South of the local area until late Thursday where the available
moisture is expected to increase over the local islands. Overall
pattern is expected to keep easterly winds through this week until
Saturday into Sunday when a frontal boundary approaches the area
but stays to our north. High pressure in the upper levels is
dominating and will continue through the workweek.

&&

.DISCUSSION...Scattered showers will continue to be expected
through the morning and late evening hours, mainly affecting the
local waters, USVI and eastern PR, but not leaving significant
amounts of rainfall. However, the available moisture and diurnal
heating will once again combine with the local effects and
prevailing wind flow to cause the development of showers and
thunderstorms in the afternoon across central and western PR with
some showers and thunderstorms also possibly affecting portions of
the San Juan metro. The soils are very saturated and any
significant showers will quickly become runoff, likely causing at
least some urban and small stream flooding. However, river
flooding is also very possible with the heaviest showers.

There is so much available moisture that afternoon convection is
likely every afternoon mainly across the central and western
sections of PR. This means that little relief is seen in terms of
drying up the soils across these sectors. The pattern should
remain fairly constant until maybe this weekend when a frontal
boundary approaches the local islands from the north. At this time
it looks like the boundary will stay just to our north but the
long range models indicate that it will get close enough to
disrupt the wind pattern and cause a shift to NE winds across the
westernmost sections of our forecast area as well as bring
cloudiness to the local area, possibly causing moderate rain and
thunderstorms due to advection and not locally induced convection.
This setup may also cause a decrease in daytime maximum
temperatures a few degrees.

&&

.AVIATION...VFR conditions will continue to prevail at all TAF sites
through 15/13z with VCSH possible at JSJ/IST/ISX. SHRA/TSRA
developing across PR after 15/16Z and this may result in MVFR conds
and mountain obscurations in and around TJPS/TJMZ through 15/22z.
Light and VRB winds through 15/13Z...becoming easterly at around
10 knots with sea breeze variations thereafter.

&&

.MARINE...Fairly tranquil seas at least until the end of the work
week, with a northerly swell expected to arrive to the local
Atlantic waters by early next week. There is a moderate risk of
rip currents across the Atlantic facing coasts of Puerto Rico,
Culebra, and Saint Thomas.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 78 88 78 / 20 40 40 40
STT 87 78 87 78 / 20 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
141 PM AST Tue Nov 15 2016

.SYNOPSIS...Another round of locally induced showers and
thunderstorms are expected this afternoon across central and
western PR with possible isolated thunderstorms across portions of
the San Juan metropolitan area as well. a moist environment will
continue through most of the week.

&&

.DISCUSSION...Showers developed this afternoon at the San Juan
metropolitan area. These showers affected also Trujillo Alto and
Guaynabo. Rainfall accumulation up to one inch was estimated by
the doppler radar. Ample moisture in the low levels of the
atmosphere will combine with local sea breezes and diurnal heating
to fuel the development of showers and thunderstorms...mainly over
the big island of Puerto Rico this afternoon. Main impact this
afternoon will be the potential for heavy rain. Due to the recent
rains of the past few days...grounds across interior and western
half of Puerto Rico are either saturated or near saturation
levels. Any additional rain this afternoon...whether heavy or
not...could result in flooding of urban and poorly drained areas
as well as rapid rise of a few of the major rivers.

For the rest of the week, local area will remain under a very
moist environment which will result in active weather each day
mainly across the Cordillera Central of Puerto Rico.

&&

.AVIATION...SHRA/TSRA will continue to develop across PR after
resulting in MVFR conds and mountain obscurations in and around
TJPS/TJMZ through 15/22z. Light and VRB winds through
15/13Z...becoming easterly at around 10 knots with sea breeze
variations thereafter.

&&

.MARINE...Fairly tranquil seas at least until the end of the work
week, with a northerly swell expected to arrive to the local
Atlantic waters by early next week. There is a moderate risk of
rip currents across the Atlantic facing coasts of Puerto Rico,
Culebra, and Saint Thomas.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 78 88 78 87 / 40 40 40 40
STT 78 87 78 87 / 40 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Wed Nov 16 2016

.SYNOPSIS...A mid to upper level ridge will hold across the forecast
area through the end of the workweek. This feature is expected to
erode during the upcoming weekend as a broad polar trough moves
across the west and central Atlantic. As the aforementioned trough
moves across the central Atlantic, its associated surface front
will approach the local islands Sat-Sun. An easterly disturbance
will continue to move mainly south of local islands today.

&&

.DISCUSSION...Clear to partly cloudy skies prevailed across the
local islands overnight and early this morning with passing showers
observed across the local waters as well as windward areas. Minimum
temperatures ranged from the upper 60s to low 70s in the mountains
to the mid to upper 70s in lower elevations. Winds were light and
variable.

A mid to upper level ridge will hold across the forecast area
through Friday. Although, this feature is not strong enough to
suppress shower/thunder development during the afternoon, could
delay the onset of showers and thunderstorms. Therefore, under east
southeast winds, precipitable water in the normal range, still
expect passing showers across the eastern third of Puerto Rico and
the U.S. Virgin Islands in the morning and late evening hours, with
locally induced showers and thunderstorms across central and
northern slopes of Puerto Rico. Due to already saturated soils,
flooding of small streams as well as sharp rises along rivers and
mudslides in areas of steep terrain are likely, particularly across
the west and interior of Puerto Rico.

As the surface front approaches, low level moisture will begin to
pool across the forecast area as soon as Friday. Plenty of
moisture will prevail across the eastern caribbean through early
next week. Therefore, as moisture increases across the area and
the ridge aloft erodes the upcoming weekend, the chance of showers
and thunderstorms will increase across the forecast area Fri-Sun.

&&

.AVIATION...VFR conditions will continue to prevail across all
terminals through at least the late morning hours. VCSH possible
across the USVI/Eastern PR area. SHRA/TSRA developing across NW PR
btwn 16/17-22Z will impact mainly the flying area of TJMZ/TJBQ with
tempo MVFR conds and mtn top obscd. Also, isolated TSRA is possible
between el Yunque and TJSJ. Low level winds from the east-southeast
at 10-15 knots with sea breeze variations aft 16/13z across the
north/northwest terminals of PR.

&&

.MARINE...Fairly tranquil seas at least until the end of the
work week, with a northerly swell expected to arrive to the local
Atlantic waters by early next week. There is a moderate risk of
rip currents across the Atlantic facing coasts of Puerto Rico,
Culebra, and Saint Thomas.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 79 87 79 / 40 40 40 30
STT 88 78 88 78 / 40 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
158 PM AST Wed Nov 16 2016

.SYNOPSIS...A broad polar trough will move across the west and
central Atlantic by the weekend. As the aforementioned trough
moves across the central Atlantic, its associated surface front
will approach the local islands Sat-Sun.

&&

.DISCUSSION...Partly sunny skies prevailed across Puerto Rico and
the U.S. Virgin Islands this morning. Very light passing showers
were observed across the eastern half of Puerto Rico. Little
rainfall accumulation was observed with this activity. Early this
afternoon, some showers with isolated thunderstorms started to
develop across the western interior and northwest sections of
Puerto Rico as well across the San Juan metropolitan area.
Showers with thunderstorms will continue to develop across these
areas through early tonight. Urban and small stream flooding is
likely across these areas.

For the rest of the week, a wetter pattern is expected for Friday
as a surface trough moves across the region from the east. As a
result, better chances for showers and thunderstorms can be
expected. For the upcoming weekend, a broad polar trough will move
across the west and central Atlantic. As the aforementioned
trough moves across the central Atlantic, its associated surface
front will approach the local islands Sat-Sun. This will result in
a very wet pattern across the region. At this time, looks like the
wettest days will be Sunday and Monday. We will continue to
monitor the evolution of this trough during the next few days.

&&

.AVIATION...VCSH possible across the USVI/Eastern PR area.
SHRA/TSRA developing across NW PR btwn 16/17-22Z will impact
mainly the flying area of TJMZ/TJBQ with tempo MVFR conds and mtn
top obscd. Also, isolated TSRA is possible between el Yunque and
TJSJ. Low level winds from the east-southeast at 10-15 knots with
sea breeze variations aft 16/13z across the north/northwest
terminals of PR.

&&

.MARINE...Seas up to 5 feet and winds up to 15 knots are expected
over the coastal waters.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 79 87 79 86 / 40 40 30 40
STT 78 88 78 85 / 40 40 40 40

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
549 AM AST Thu Nov 17 2016

.SYNOPSIS...Mid-upper level ridge will prevail over the Northeast
Caribbean Region through the end of the week. Surface trough is
moving across the forecast area today...promoting a moist and
unstable pattern across Puerto Rico and the U.S. Virgin Islands.
Then...a frontal boundary will stall over the local islands during
the weekend. The shearline/trough associated with the frontal boundary
will prolong the unsettled pattern through early next week.

&&

.DISCUSSION...Satellite derived precipitable water analysis indicated
abundant moisture over the Eastern Caribbean associated with the
aforementioned surface trough. Southeasterly flow will promote
moisture transport over the forecast area today. As a result...
showers and isolated thunderstorms will likely affect the south
and east portions of PR and the U.S. Virgin Islands during the
morning hours. Then...local island effects will combine with deep
tropical moisture to induce the development of showers and thunderstorms
across the Central Interior, West and Northwest PR. A similar pattern
is forecast for Friday.

Over the weekend, a frontal boundary will approach the local
islands from the north-northwest. The boundary and its associated
moisture is forecast to stall over the Puerto Rico between Sunday
and Monday. The shearline/trough over the local area will enhance
the moisture convergence across the local islands...resulting
in organized convection over Puerto Rico and the adjacentislands.
This unstable pattern is forecast to persist across the area
through Tuesday. Conditions will gradually improve by midweek next
week as drier and more stable air mass will move over the region.

&&

.AVIATION...VFR conditions will continue to prevail across all
terminals through at least the late morning hours. VCSH possible
across the USVI/Southeastern PR area. SHRA/TSRA developing across
the interior and western PR btwn 17/17-22Z will impact mainly the
flying area of TJMZ/TJBQ with tempo MVFR conds and mtn top obscd.
Also, isolated TSRA is possible between el Yunque and TJSJ. Low
level winds will continue east-southeast at 8-15 knots with sea
breeze variations aft 17/13z across the north/northwestern terminals
of PR.

&&

.MARINE...Tranquil marine conditions will prevail across the local
waters through Friday. Then, a short-period northerly swell will
gradually increase the seas during the weekend and early next
week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 77 87 77 / 40 30 40 40
STT 86 77 87 77 / 40 40 40 50

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
207 PM AST Thu Nov 17 2016

.SYNOPSIS...Increasing moisture will trigger more and more showers
as we move into the weekend and early next week, raising the
potential for flooding. See our Hydrologic Outlook (ESFSJU) for
more details.

At upper levels...A ridge over the U.S. Virgin Islands will shift
to Puerto Rico Saturday evening then move to the Leeward Islands
Sunday night and beyond as a trough digs toward the local area.
The sub-tropical jet will sag toward 22 north as it does so. Later
next week high pressure builds over the western Caribbean and
brings northwest flow to the area.

At mid levels...High pressure over Puerto Rico will dominate the
eastern Caribbean until mid-week. High pressure will build over
the Gulf of Mexico mid week next week with northwest flow
continuing over the area.

At lower levels...A cold front northwest of the area will approach
very slowly as high pressure over the southeastern United States
builds offshore into the western Atlantic Friday night. A second
stronger high over the southeast United States will force the
front into the local area with much above normal moisture. The
high pressure moves into the western Atlantic pushing stronger
than usual easterly flow over the local area late next week.

&&

.DISCUSSION...An atmosphere rich in moisture and relatively
unstable launched showers and thunderstorms across Puerto Rico and
downstream from the U.S. Virgin Islands beginning around noon.
Showers became very heavy and sent local rivers close to flood
stage as of 2 PM AST. Some reports of flooding have been received
for flooded roads in San Juan and Caguas. A mudslide was reported
in Morovis.

This is the beginning of a period of much higher than normal
moisture ahead of an approaching boundary--technically a
prefrontal shear line--that will cause showers and thunderstorms
to grow over the local islands each day and release more and more
rainfall as the boundary approaches--at this time supposedly
Monday and Tuesday. Heavy rain, already occurring today, will also
be seen Saturday, and is expected to increase each day Sunday
through Tuesday. Showers and thunderstorms will diminish
considerably Wednesday, as mid level moisture goes from over 90
percent relative humidity to less than 10 percent Tuesday night
or Wednesday according to the latest models.

Although showers and thunderstorms will not be continuous, but
more of a daytime phenomenon, at least over land, light winds and
the approaching boundary will align the showers and thunderstorms
that form to move over and over across specific areas,
concentrating the rainfall in certain areas over others and thus
causing some very heavy rainfall amounts that could potentially result
in flooding. The heaviest rain is indicated for Monday and Tuesday
at the present time, but heavier rains will begin to appear as
early as Saturday.

&&

.AVIATION...SHRA/TSRA will continue across the interior and western
PR through 22Z will impact mainly the flying area of TJMZ/TJBQ with
tempo MVFR conds and mtn top obscd. VCSH expected elsewhere. Low
level winds will continue southeast at 8-15 knots with sea breeze
variations aft 17/22z across the north/northwestern terminals of
PR.

&&

.MARINE...Tranquil marine condtions for now, but seas will begin
to rise Friday night and small craft advisories may be necessary
as early as Thanksgiving Day as swell from the north and northeast
move into the area. Otherwise expect showers and thunderstorms
with increasing frequency Saturday through Tuesday as a boundary
moves into the area.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 77 86 77 86 / 30 60 40 40
STT 77 87 77 86 / 40 50 50 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
555 AM AST Fri Nov 18 2016

.SYNOPSIS...A frontal boundary will stall over the local islands
during the weekend maintaining a very moist and unstable environment
through at least Tuesday. The shearline/pre-frontal trough associated
with the frontal boundary will enhance the moisture convergence across
the local islands through early next week. Drier and more stable air
mass will encompass the region by midweek next week.

&&

.DISCUSSION...Active weather was observed across the coastal
waters and portions of the South and East Puerto Rico since
midnight. High moisture content combined with good low level
convergence to produce several rounds of heavy rainfall across
Southeast Puerto Rico. Rainfall accumulations in excess of 4
inches were estimated in Maunabo and Yabucoa. Other areas of the
Southeast Quadrant of Puerto Rico received between 1-3 inches.

The rest of today...the east-southeast flow will continue to favor
moisture transport over the forecast area today. As a result...showers
and isolated thunderstorms will continue to affect the south and
east portions of PR and the U.S. Virgin Islands during the morning
hours. Then...diurnal induced showers and thunderstorms will form
along the Interior, West and Northwest PR as well as portions of
the San Juan Metro Area.

Saturday through early next week...a frontal boundary will approach
the local islands from the north-northwest. Operational models
suggest that the moisture will peak late Sunday into Monday with
precipatable water values around 2.15 inches. The shearline/pre-
frontal trough will enhance the low level convergence and focus the
abudant moisture over Puerto Rico and the U.S. Virgin Islands. In
addition...the weak steering winds will favor higher rainfall
accumulations across the islands. Due to already saturated soils
across most of PR...the potential impacts include flooding along
rivers and streams as well as mudslides in areas of steep terrain.

Conditions will gradually improve by midweek next week as drier
and more stable air mass will move over the region.

&&

.AVIATION...SHRA/Isold TSRA over the Atlantic and Caribbean waters
will continue thru the fcst period. Mtn top obscd over eastern PR
due to SHRA/low cig/Scud clds expected for the rest of the morning
hours. SHRA/TSRA is expected to develop along the interior and
western sections of PR during the afternoon. Also, isold TSRA is
possible between el Yunque and TJSJ. MVFR conds expected with this
activity across the PR terminals. Mainly VFR at the leeward
terminals and VCSH at USVI terminals with possible VCTS at times
through the forecast period. Low level winds fm E-SE at 5-15 knots
with sea breezes aft 14z.

&&

.MARINE...A relatively tranquil marine conditions will prevail
across the local waters through the weekend. Then, a short-period
northerly swell of 4-6 feet will increase the seas next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 77 86 76 / 60 40 40 50
STT 87 77 86 76 / 50 50 50 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
217 PM AST Fri Nov 18 2016

.SYNOPSIS...Persistent moisture ahead of a cold front will keep
rain chances high over Puerto Rico through Tuesday. Showers and
thunderstorms will affect some areas with very heavy rain that
could result in flooding during the period. Drying is expected to
begin on Wednesday.

At upper levels...A ridge over the Anegada passage shifts back to
Puerto Rico Saturday night, but then quickly moves east into the
tropical Atlantic late Sunday when a trough passes north of the
area. Flow becomes west northwest afterward.

At mid levels...High pressure continues over the Caribbean Sea. A
trough passes north of the area on Monday. Relative humidities
remain high through Wednesday morning.

At lower levels...A cold front northwest of the area continues
over the eastern tip of Hispaniola leaving Puerto Rico and the
U.S. Virgin Islands in moist easterly flow until at least Tuesday.
Flow continues from the east northeast afterwards with diminishing
moisture as low pressure continues across the southern Caribbean.

&&

.DISCUSSION...As of 1:30 PM AST radar showed heavy showers and
a few thunderstorms south of Puerto Rico and showers west and
northwest of Puerto Rico. More or less continuous light rain has
persisted across South east and south central coastal Puerto Rico
with minor amounts. Some thinning has occurred in the cloud cover
that, so far, has prevented convection over most of mainland
Puerto Rico. However moisture continues very high over the area,
especially in the southwest, and so some convection is still
possible. First heavy showers have begun to form over Arecibo and
Camuy.

Models are no longer bringing the boundary over the local area,
but do keep very moist and saturated air in the local area, but
mainly northwest of the islands. The ECMWF brings the moisture
ahead of the boundary over Puerto Rico on Monday and this
continues through Tuesday night. The most favorable upper level
dynamics are now portrayed Saturday night through Monday night.
Hence although the severity of the flooding originally expected
over the next 5 days is some what diminished, the threat of
flooding and mudslides still continues and appears to last through
Tuesday.

&&

.AVIATION...Mainly VFR conditions are to prevail across all
TAF sites through at least 19/00z. SHRA/TSRA could affect TJPS and
TJMZ tonight producing brief periods of MVFR conditions. The Leeward
islands should remain VFR, but may have brief periods of shra and
MVFR conds due to CIGS. Winds alf are ESE up to 12 kft then becoming
WSW to W and increasing to 35 kt near 40 kft. Conds should prevail
through 19/12Z.

&&

.MARINE...Marine conditions will remain inclement with showers and
isolated thunderstorms in the area for the next 5 days; the best
conditions being in the southeast. During this time seas in the
Atlantic will slowly rise. Seas will begin to increase on Saturday
with 6 foot seas in the outer Atlantic waters possible by Sunday
night. Small craft advisories may be necessary by Wednesday.
Caribbean waters should remain below 6 feet until Wednesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 77 87 75 86 / 40 40 40 40
STT 78 86 76 86 / 50 50 50 50