Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
458 AM AST Sun Apr 1 2018

.SYNOPSIS...Drier than normal moisture expected today and Monday
before a SFC trough moves in on Tuesday, bringing much deeper
moisture and winds from the SE. Upper level trough will be
positioned over Hispaniola by Tuesday, helping with the
development of sustained showers and thunderstorms over the local
area. Upper ridge to prevail thereafter and mainly easterly winds
with some lingering moisture through at least Thursday.

&&

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

Partly cloudy skies prevailed across Puerto Rico and the U.S.
Virgin Islands overnight. Some passing showers were noted across
the offshore Atlantic waters. Some of these showers moved inland
over the northeast section of Puerto Rico and the northern U.S.
Virgin Islands. Isolated to scattered showers will continue to
affect the north and northeast sections of Puerto Rico this
morning. For this afternoon, some showers could develop across the
western interior and southwest sections of Puerto Rico. For
tonight, a very dry air mass is expected to encompass the region.

Dry weather conditions will prevail through Monday, with limited
shower activity expected. However, for Tuesday an induce surface
trough is forecast to affect the region with an increase in
cloudiness with showers and thunderstorms expected. At this time,
looks a wet day in store for Tuesday, as this feature combined
with favorable upper level atmospheric conditions.

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

After the upper trough and induced sfc trough affect the local
area on Tuesday, lingering moisture will be present over the local
area through at least Thursday, then near normal moisture for
Friday into the weekend. The upper trough is expected to flatten
out and move away by Wednesday and an upper ridge would dominate
over the area, but this deep lingering moisture will combine with
the local effects and diurnal heating to cause the development of
afternoon showers and thunderstorms, especially across western PR
and any area that may have sea breeze convergence in the
afternoon hours on Wednesday and Thursday. Latest guidance is
indicating that drier air would move in on Friday, keeping
available moisture near normal from Friday into the weekend. With
no particular feature in the mid or upper levels to enhance
instability on Friday and the weekend, only locally induced
showers and thunderstorms would be expected in the afternoon
hours those days as well, with isolated to scattered brief showers
elsewhere.

&&

.AVIATION...VFR conditions will prevail across the forecast area
through at least 01/22z. Some showers can be expected in the vicinity
of TJMZ this afternoon. Low level winds will be mainly northeast
at 10 to 15 kts.

&&

.MARINE...Seas will be choppy today, up to 5 feet across the
Atlantic waters but relatively tranquil elsewhere with seas up to
4 feet. The local seas are expected to continue fairly tranquil
for the rest of the workweek with seas generally up to 4 feet
across all of the local waters. There is a moderate risk of rip
currents across some beaches of northern PR today.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 87 75 / 10 20 20 20
STT 84 72 83 73 / 20 10 20 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
520 PM AST Sun Apr 1 2018

.SYNOPSIS...Early morning showers on the northeast coasts and
afternoon showers in western Puerto Rico will continue Monday. On
Tuesday better moisture will move into the area triggering showers
and possibly some thunderstorms. The remainder of the week will
see showers taper back somewhat but conditions will still be more
active than were had this weekend.

&&

.SHORT TERM...Tonight through Wednesday...

Partly cloudy conditions will continue for the rest of the
afternoon with some showers lingering in the west through this
evening.Flow is east northeast at 5 to 10 mph. Drier air still
remains across the region tonight which will suppress shower
activity across most of the area except for the beaches and
coastal foothills of northeastern Puerto Rico later tonight.

Dry air will remain across the area through Monday morning. Monday
afternoon the area of tropical moisture that started over the
Windward Islands will move toward Saint Croix. Showers will
start across the U.S. Virgin Islands and will move northwest
with the low level moisture. The SJU-GFS shows precipitable
waters values climbing to 1.7 inches, this will be a significant
increase from this weekend`s values that were near 1.20 to 1.30
inches.

Tuesday, moisture will move in from the deep tropics and
cause showers with the possibility of isolated thunderstorms.
Tuesday will also likely be the wettest day of the week due to a
combination of factors, including an influx of low-level moisture,
better upper level divergence, and indications of upward vertical
motion at 700 mb. Unfortunately the trend of the GFS over the
last 24 hours has been to erode mid-level moisture which was
critical for strong convective activity, so we are not
anticipating as much rain as previously, but some urban and small
stream flooding will still be possible. Additionally, the short
wave trough from the northwest that will move northwest and north
of the islands on Tuesday, along with an upper level jet, is no
longer as strong as previously indicated. Also, the best upper
level divergence aloft looks to arrive before the low-level
moisture over Puerto Rico. The lifted index value has also
increased on the latest model run suggesting less instability.

On Wednesday, the trough lifts out, leaving behind east northeast
winds with somewhat drier air remaining across the region.

.LONG TERM...Thursday through Sunday...
Flow at upper levels turns northwest as a weak ridge passes
through. After which, broad high pressure at upper levels
prevails over the Caribbean Sea and northern South America. Areas
of low level moisture continue to transit Puerto Rico and the U.S.
Virgin Islands in what is essentially easterly flow with a few
variations right through the weekend. Mid levels, on the other
hand, remain mostly dry. This will yield late night and morning
showers along the eastern slopes of the Luquillo range with
isolated showers over the U.S. Virgin Islands, followed by mostly
scattered shower during the afternoon hours over western and
interior Puerto Rico with few showers for the USVI. The best
chances for rain during the period will be on Sunday. Amounts
should generally be quite modest.

&&

.AVIATION...VRF conditions will continue through 02/22Z.
Prevailing east northeast winds of 5 to 10 kts at lower levels
turn slowly with height to the WSW by FL300-440 and increase to
60 knots. Sfc winds bcm ESE at 5 to 10 mph aft 02/03Z with
land/sea breezes dominating, but flow reverts to ENE aft 02/21Z ahead
of a weak low-level trof psg expected 03/18Z.

&&

.MARINE...Seas will subside slowly through tonight, then remain 3
to 5 feet. Seas may reach small craft advisory conditions in the
northeast corner of the outer Atlantic waters by Monday, 08
April.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 74 85 74 84 / 30 30 40 40
STT 71 84 72 85 / 10 20 30 40

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Mon Apr 2 2018

.SYNOPSIS...A seasonable weather pattern is expected to prevail
today with some locally induced afternoon showers across west
Puerto Rico. The chance for shower and thunder activity is
expected to increase Tuesday through Thursday.

&&

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

Clear to partly cloudy skies prevailed across the local islands
overnight and early this morning. Doppler radar detected only some
isolated showers across the Atlantic waters, with few of them
briefly affecting the northern coastal sections of Puerto Rico.

An upper level ridge is expected to hold over the region today and
Tuesday. At the surface, a weak high pressure will continue across
the central Atlantic today. Another stronger surface high is
expected to move across the northwest Atlantic Tuesday and
thereafter. These features are expected to maintain an east to east
northeast low level wind flow across the region today and for the
next couple of days. Drier air will remains across the region today
and early Tuesday, which will suppress shower activity across most
of the area. However, the available moisture will combine with
daytime heating, sea breeze development and orographic effects to
induce the development of shower activity across interior and
western Puerto Rico each afternoon.

An upper level trough is expected to reach the region from the west
late Tuesday and Wednesday. This feature will result in an increase
in moisture transport across the local islands Tuesday night and
Wednesday, inducing the development of showers and isolated
thunderstorms across the local islands and surrounding waters. Model
guidance shows precipitable waters values climbing to 1.7 inches,
this will be a significant increase from previous days values that
were near 1.20 to 1.30 inches.

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

Plenty of moisture is expected to prevail across the forecast area
on Thursday to assure frequent passing showers across USVI and E
PR throughout the day as well as numerous showers with thunderstorms
across west Puerto Rico in the afternoon.

The chance for shower and thunder activity is expected to quickly
decrease Friday and into the next week as a mid level ridge
strengthens across the area. However, patches of low level
moisture embedded in the trades will continue to combine with sea
breeze and diurnal heating to result in locally induced afternoon
showers with a few isolated thunderstorms across west Puerto Rico
each day.

&&

.AVIATION...Mostly VFR conditions are expected to continue across
most of the local flying areas during the next 24 hours. Surface
winds will continue from the east to east northeast at around 10
knots with sea breeze variations after 02/14z. Local and diurnal
effects will produce the development of shower activity over western
and interior sections of Puerto Rico after 02/17z with SHRA briefly
affecting TJMZ and TJBQ.

&&

.MARINE...Tranquil marine conditions will continue through the
work week with seas at 4 feet or less and light to locally
moderate trade winds.

&&

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

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
455 AM AST Tue Apr 3 2018

.SYNOPSIS...The chance for showers and thunderstorms will continue
to increase today through Wednesday. Although trofiness is expected
to move away by Thursday, lingering moisture and therefore showers
are still expected to prevail. A more seasonable weather pattern
with locally induced showers and a few isolated thunderstorms
across west Puerto Rico each afternoon is expected Friday and into
the upcoming weekend.

&&

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

Partly cloudy skies prevailed across the local islands overnight
and early this morning. Terminal doppler radar indicated isolated
to scattered showers mostly across the Atlantic waters, with few
of them briefly affecting the northwest coastal sections of Puerto
Rico. Otherwise, not significant precipitation was observed.

Currently, an upper level ridge across the islands will continue to
provide fair weather conditions and partly cloudy skies across the
local islands through the rest of the morning hours. However, the
upper ridge is expected to erode rapidly this afternoon as an upper
level trough approaches. Thus, this afternoon will be a transition
to a wet pattern for Puerto Rico and the U.S. Virgin Islands. The
upper ridge will be replaced by an upper level trough that will
move in from the west. This feature will result in an increase in
moisture transport across the region this afternoon through
Wednesday afternoon, inducing the development of showers and
isolated thunderstorms across the local islands and surrounding
waters. Model guidance continues to indicate a modest increases in
precipitable waters values this afternoon and Wednesday, in the
range of 1.60-1.70 inches. By Wednesday and Thursday, the upper
level support that was present will lift out of the region,
leaving no upper level divergence, and drying of the low and
middle levels of the atmosphere. However, some lingering moisture
will be sufficient to induce the development of isolated to
scattered showers especially during the afternoon over central and
western Puerto Rico.

At the surface, a weak high pressure ridges will continue across the
central and western Atlantic today and Wednesday. These feature will
maintain an easterly wind flow across the region during the forecast
period. A stronger surface high is expected to develop to the
northeast of the region by Thursday.

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

A mid level ridge will hold across the forecast area Friday through
the upcoming weekend with some weakening expected by midweek next
week. Precipitable water will remain near or slightly below the
normal range under moderate easterly winds. If the forecast holds,
expect a seasonable weather pattern with locally induced showers
and thunderstorms across west Puerto Rico each afternoon. Elsewhere,
mainly fair weather is expected.

&&

.AVIATION...Mostly VFR conditions are expected to continue across
most of the local flying areas through 03/15Z. However, a surge of
moisture south, southeast of PR and the USVI will combine with
daytime heating with the aid of an approaching upper trough...
increasing SHRA across the local terminals after 03/17z. Latest TJSJ
sounding indicated east winds at 5-17 kts below FL030 and south-
southwest winds above FL050 and increasing with height.

&&

.MARINE...Tranquil marine conditions will continue through the
work week with seas at 5 feet or less and moderate trade winds.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
405 AM AST Wed Apr 4 2018

.SYNOPSIS...An upper level trough across the region in combination
with a weak surface trough across Hispaniola will increase the
shower and thunderstorm activity today and Thursday. Patches of
low level moisture embedded in the trades will produce scattered
showers Friday and for the next several days.

&&

.SHORT TERM...Today through Friday...
Variably cloudy skies prevailed across the forecast area overnight
and early this morning with isolated to locally scattered passing
showers observed across the northern USVI and NE Puerto Rico.
Temperatures were in the mid 70s along coastal areas under light and
variable winds.

As a mid to upper level trough across the northeast Caribbean shifts
northeast while weakening, a mid level ridge will build across the
local isles from the west. The mid level ridge will then hold across
the forecast area Thursday through the upcoming weekend. At lower
levels, a surface high pressure north of the area will continue to
promote easterly winds through the forecast cycle. Based on latest
guidance, precipitable water will remain near normal values...which
is 1.50 inches...with a sharp decrease Thursday into Friday under
the building ridge.

Therefore, still expect scattered passing showers across USVI and E
PR through at least Thursday with showers and thunderstorms
developing over and west of the Cordillera Central this afternoon.
Afternoon showers and thunderstorms are still expected Thursday and
Friday, but intensity and areal coverage should decrease under
the building ridge.

.LONG TERM...Saturday through Wednesday...
An upper level ridge is expected to weakly build over the region
Saturday. This feature will hold over the local islands through
the rest of the forecast period. A short wave trough is expected
to pass well to the north of the region Sunday and Monday, with
limited effects, if any, over the local islands.

A strong surface high pressure is expected to hold across the
central Atlantic through at least Tuesday, maintaining an
easterly low level wind flow across the local islands for much of
the period. Not significant weather event are expected during the
forecast period. However, patches of shallow low level moisture
embedded in the easterly trades will be sufficient to produce
isolated to scattered shower activity across the U.S. Virgin
Islands and eastern sections of Puerto Rico during the night and
early in the morning. This moisture in combination with daytime
heating, sea breeze development and other local effects will
produce showers and possible a couple of thunderstorms each
afternoon across western sections of Puerto Rico, but not
widespread precipitation is expected. .

&&

.AVIATION...VFR conds are expected to prevail at all TAF sites
through the morning hours with -SHRA possible in and around JSJ. Aft
04/16z, MVFR conds and mountain obscurations likely in and around
JMZ/JPS in SHRA/TSRA through 04/22z. Easterly winds 12 knots or less
with some sea breeze variations.

&&

.MARINE...Tranquil conditions to continue through the weekend with
seas up to 5 feet and winds up to 15 knots. Seas are expected to
increase by Tuesday, next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 76 87 76 / 40 50 20 10
STT 84 74 86 75 / 40 50 20 20

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
425 AM AST Thu Apr 5 2018

.SYNOPSIS...Trade wind flow will dominate the surface pattern from
high pressure in the central Atlantic. Patches of moisture embedded
in the trades will bring periods of showers over the U.S. Virgin
Islands during the night and morning hours, followed by some
afternoon convection over western and interior Puerto Rico.

&&

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

Mostly clear skies prevailed across the forecast area overnight
and early this morning with a few isolated passing showers noted
across the coastal waters. Temperatures were in the mid 70s at
lower elevations under light and variable winds.

Although a mid level ridge will continue to build across the forecast
area, this feature is not strong enough to suppress shower and thunder
development. Therefore, expect another round of showers with isolated
thunderstorms across the western interior and west Puerto Rico during
the afternoon hours. Soils are already saturated across these areas,
and as a result urban flooding as well as rises along small streams and
rivers are likely with the heaviest showers. Intensity and areal
coverage of afternoon showers and isolated thunderstorms across west
Puerto Rico are expected to decrease somewhat Friday and Saturday as
low level moisture erodes under building ridge. Elsewhere, fair weather
to continue with isolated passing showers.

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

An upper level ridge is expected to hold over the region through at
least Wednesday, next week. While the ridge remains over the region,
not significant weather feature is expected to affect the local
islands and surrounding waters. A short wave trough and its associated
frontal boundary at the surface is forecast to pass to the north
of the region Sunday and Monday. No significant effects are expected
over the forecast area in association with the passing of the
shortwave trough north of the region.

A strong surface high pressure is expected to hold across the central
Atlantic through at least Wednesday, maintaining an easterly low
level wind flow across the local islands through most of the forecast
period. Winds are expected to become from the southeast on occasions,
resulting in warmer than normal temperatures along the northern
coastal areas of Puerto Rico. This surface high will continue to
pull areas of shallow moisture across the local islands from time
to time. This moisture embedded in the trades will be sufficient
to produce isolated to scattered shower activity across the U.S.
Virgin Islands and eastern sections of Puerto Rico during the
nights and early in the mornings. The combination of this moisture
with daytime heating, sea breeze development and other local
effects will produce showers and possible a couple of thunderstorms
each afternoon across western sections of Puerto Rico, but not
widespread precipitation is not expected at this time.

&&

.AVIATION...VFR conds are expected to prevail at all TAF sites
through the forecast cycle. However, Aft 05/16z, MVFR conds and
mountain obscurations likely in and around JMZ/JPS in SHRA/TSRA
through 05/22z. Easterly winds 12 knots or less with some sea breeze
variations.

&&

.MARINE...Tranquil marine conditions are expected to continue
with seas up to 4 feet and winds up to 15 knots for the next
several days. However, a moderate risk of rip current is expected
across of the northern beaches of Puerto Rico and across some
beaches of St Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 75 87 76 / 30 10 10 20
STT 84 74 87 76 / 20 20 20 20

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
404 AM AST Fri Apr 6 2018

.SYNOPSIS...Surface high pressure across the Central Atlantic
will continue to promote a moderate easterly wind flow across the
local area for the next several days. An upper level ridge is
expected to weakly develop just south of the local islands early
next week. The lack of upper level dynamics and near to below
normal moisture means that any thunderstorm activity in the local
area should be isolated and the development of any significant
showers or thunderstorms through this weekend would likely be due
to local effects.

&&

.SHORT TERM...Today through Sunday...
Mostly clear skies prevailed across the forecast area overnight and
this morning with a few showers mainly over the coastal waters.

Surface and mid level ridge will continue to strengthen over the
region through Sunday with prevailing easterly winds of 5 to 10
mph. As for today due to lingering low level moisture, local
effects and daytime heating expect showers with isolated
thunderstorms mainly over portions of western interior and western
Puerto Rico. Due to saturated soils from yesterdays rainfall
urban flooding is likely for areas that receive the heaviest
rainfall today.

Saturday - Sunday,
Surface and mid level ridge will erode away most of the available
moisture across the region. As a result fair weather condition
will prevail through the weekend but, an isolated passing shower may
be possible.

.LONG TERM...Monday through Friday...
An upper level ridge is expected to remain just to the south of the
region through at least Wednesday. While the ridge remains over
the region, not significant weather feature is expected to affect
the local islands and surrounding waters. A short wave trough and
its associated frontal boundary at the surface is forecast to pass
to the north of the region Monday and Tuesday. Not significant
effects are expected over the forecast area in association with
the passing of the shortwave trough north of the region.

A strong surface high pressure is expected to hold across the central
Atlantic through at least Thursday, maintaining an easterly low
level wind flow across the local islands through most of the
forecast period. Winds will become from the southeast on
occasions, resulting in warmer than normal temperatures along the
northern coastal areas of Puerto Rico. The surface high will
continue to pull areas of shallow moisture across the local
islands from time to time. This moisture embedded in the trades
will be sufficient to produce isolated to scattered shower
activity across the U.S. Virgin Islands and eastern sections of
Puerto Rico during the nights and early in the mornings. The
combination of this moisture with daytime heating, sea breeze
development and other local effects will produce showers and
possible a couple of thunderstorms each afternoon across western
sections of Puerto Rico, but not widespread precipitation is not
expected during the forecast period.

&&

.AVIATION...VFR conditions are expected to prevail through the
remainder of the 06/06Z TAF period. Sfc winds from the east
northeast at 5 to 10 kts and upper level winds turning to the
northwest from FL130-FL380 at 10 to 40 kts. SHRA are expected by
06/18Z for terminals TJMZ and TJBQ then clearing after 06/23Z.

&&

.MARINE...Fairly tranquil seas expected today and through the
upcoming weekend with wave heights up to 5 feet across the
offshore Atlantic waters, up to 4 feet elsewhere. Winds will be up
to 15 knots for the next several days as well.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 75 89 76 / 10 10 10 20
STT 86 76 86 77 / 20 10 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
455 AM AST Sat Apr 7 2018

.SYNOPSIS...Generally dry conditions with scattered afternoon
showers are expected today. Moisture increases erratically next
week and conditions turn wetter over the following weekend. Winds
will increase over the eastern Atlantic this weekend and around
the forecast area by mid-week, generating hazardous seas.


&&

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

Mostly clear skies prevailed across the forecast area overnight and
this morning with light east northeast winds.

The surface ridge and a weak mid level ridge will erode away most
of the available moisture across the region, but local and
diurnally induced afternoon showers will be possible. The heaviest
rain will be over portions of the interior and western Puerto
Rico similar to yesterday. Elsewhere sunny skies with the
possibility of a passing shower late in the afternoon are
expected.

Sunday, the polar trough will move into Florida and the Atlantic
waters and impinge on the mid level ridge over the Caribbean. As a
result, moisture will increase and scattered showers will grow by
midday.

On Monday, global models depict an easterly wave moving through
the Lesser Antilles which can be tracked by the 700 mb heights.
Once the wave moves through the Lesser Antilles it begins to
weaken and dissipates greatly before reaching Puerto Rico on
Monday. But, the wave will bring an increase in moisture across
the region. This combined with local and diurnally induced effects
will generate showers across western and interior Puerto Rico.

.LONG TERM...Tuesday through Friday
Patches of moisture generate in the western tropical Atlantic and
move over the area. Flow is generally easterly but becomes more
southeasterly Wednesday night through Friday with warmer daytime
temperatures on the north coast. Precipitable water values vary
widely until Friday morning as moisture patches move through, but
conditions become distinctly wetter over the weekend. Some urban
and small stream flooding is possible after Friday--mainly in
western and interior portions of Puerto Rico. Winds increase
considerably across the tropical Atlantic early in the week.

&&

.AVIATION...VFR conditions are expected to prevail through the
remainder of the 07/06Z TAF period except for psbl MVFR conds at
TJMZ btwn 07/16-21Z due to CIGS. Sfc winds from the east
northeast at 5 to 10 kts. Some passing SHRA are expected by 06/15Z
for terminals TJSJ,TJBQ and TJMZ then clearing after 07/23Z. SHRA
will continue VCTY the Leeward Islands.

&&

.MARINE...Waves created by tight gradients over the eastern
Atlantic will begin to be seen on Wednesday and small craft
advisories will be necessary for much of the rest of the week--
mainly on the eastern side of the Atlantic and Caribbean waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 90 75 / 10 20 20 40
STT 85 75 85 76 / 20 20 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
357 PM AST Sat Apr 7 2018

.SYNOPSIS...A SFC high pressure across the east central Atlantic
will keep easterly winds today across the local area, then a SFC
low moving NE along the U.S. East Coast will cause the local winds
to shift a bit more southeasterly while at the same time causing a
northerly swell which is expected to reach our waters by late
Monday. Upper ridge will remain over the local area for the next
several days. Patches of moisture will pass through, causing the
overall moisture to be either near normal or slightly below normal
through the early part of the workweek.

&&

.SHORT TERM...Tonight through Monday...

The afternoon convection that occured this afternoon is expected
to diminish shortly after sunset, with gradually improving weather
this evening and tonight. The current weather pattern is not
conducive to prolonged and sustained thunderstorm development even
though heavy showers and isolated thunderstorms are expected.
However, these showers and thunderstorms are expected to be
locally induced in the afternoon hours each day due to the
combination of the local effects and diurnal heating. The shower
activity will affect western PR mostly with a streamer or two
developing and affecting portions of the San Juan metro area. The
USVI however is expected to remain mainly dry except for the
westernmost sections of the island as streamers develop and
possibly affect that western tip as the showers move west. Then in
the overnight and early morning hours for the next few days,
isolated to locally scattered and brief showers are expected
across the local waters, USVI, and eastern PR. This general
pattern is expected through the weekend and into the upcoming
workweek.

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

Patches of moisture across the western tropical Atlantic will
affect the local area. Flow will be generally easterly, becoming
more southeasterly on Wednesday night through Friday.
Because of these patches of moisture, precipitable water values
are expected to vary widely until Friday as the patches of
moisture move through. The upper levels may not have any
particular feature that would cause enhanced areas of instability,
therefore most of the shower and possible thunderstorm activity
will likely be locally induced. Keep in mind that this is the long
term forecast, so confidence is moderate at best at this point.

&&

.AVIATION...VFR conditions will continue to prevail across most TAF
sites through the forecast period. Brief periods of MVFR conditions
can be expected across TJMZ and TJBQ in SHRA/TSRA through 07/22z.Low
level winds will continue mainly east at 10 kts.


&&

.MARINE...Fairly tranquil seas with maybe a slight chop across the
offshore Atlantic waters and the Anegada passage due to seas of
up to 5 feet. Seas of 4 feet or less are expected for most of the
remaining waters. Rip current risk will be low to moderate for the
next couple of days.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 90 75 87 / 20 20 40 40
STT 75 85 76 85 / 20 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
458 AM AST Sun Apr 8 2018

.SYNOPSIS...A disturbance with moderate showers remains east of
the Leeward Islands. Moisture will peak on Monday, but showers
will continue in the west for much of the week. Winds and seas
will increase mid week with a persistent high in the central
Atlantic.

&&

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

Mostly clear skies prevailed across the forecast area overnight and
this morning with light east southeast winds.

Today, a polar trough aloft in the Gulf will move into the Atlantic
waters late tonight and impinge on the mid level ridge over the
the local area as a result we will see an increase in available
moisture with scattered showers by midday. The high in the central
Atlantic at the surface will turn the winds to the east southeast
for about 24 hours. An area of disturbed weather near the Leeward
Islands has moved very little during the past several days. Most
reliable models show the moisture of the disturbance further west
than the actual IR imagery shows. As a result POPs will be
lowered for the eastern portions of Puerto Rico today.

On Monday, the surface and mid level ridge strengthens north of
the area, while the broad upper level ridge remains overhead also.
Early Monday a surge of moisture will move in from the east from
the disturbance thus increasing precipitable water values across
the region. This increase in low level moisture, combined with
local effects, and diurnal heating will induce showers with the
possibility for isolated thunderstorms--mainly in western and
interior Puerto Rico. The formation of thunderstorms will depend
on how close the upper level jet gets to Puerto Rico. The jet
will need to get close enough to generate instability.

Tuesday, the ridge aloft remains across the area with low level
moisture moving over the area during the afternoon, this combines
with diurnal heating to cause showers across the U.S. Virgin
Islands and eastern Puerto Rico in the morning, then the showers
will form across western and interior Puerto Rico during the early
afternoon hours.

.LONG TERM...Wednesday through Sunday...
The strong high over the east central Atlantic is already
generating better winds east of the area. These winds will arrive
by Wednesday along with higher seas. The ridge aloft builds back
over the local area after the passage of a short wave trough
Tuesday and is followed by a westerly jet Friday through Sunday.
Shower activity, however will remain dependent on the shallow
moisture in the marine layer as mid levels do not moisten
sufficiently until Sunday to yield a significant change in shower
coverage. Currently the GFS shows a break in the moisture on
Saturday, but the GFS has been inconsistent with columnar moisture
beyond Friday. Divergence aloft will also come into the picture
on Sunday.

&&

.AVIATION...VFR conditions are expected to prevail through the
remainder of the 07/06Z TAF period except as mentioned below. Sfc
winds currently are from the east southeast at 5 to 10 kts.
VCTY SHRA cont til 08/14Z with MVFR CIGS psbl at TNCM/TKPK. Some
passing SHRA are expected aft 08/15Z for terminals TJSJ,TJBQ and
TJMZ then clearing after 08/22Z. MVFR conds expected in TJMZ with
mtn obscurations in interior PR. Max winds WSW incrg to 50 kt at
FL410 by 09/06Z. Winds less than 15 kt below FL250.

&&

.MARINE...Tranquil seas of less than 5 feet will gradually
roughen by mid week. Seas generated by winds south of the high
pressure in the east central Atlantic will arrive late Tuesday and
Wednesday. Small craft advisories are likely then for 7 foot seas
spreading across the outer Atlantic waters and part of the
Caribbean sea.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 88 74 / 20 40 40 30
STT 85 76 85 75 / 40 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
417 PM AST Sun Apr 8 2018

.SYNOPSIS...Strong surface high pressure across the east central
atlantic will continue dominating the local winds for the next
several days, with winds increasing slightly for midweek. Upper
ridge over the local area will prevail for the next several days.
Showers and possible thunderstorms will mostly be limited to areas
of sea breeze convergence and due to local effects for the next
few days.

&&

.SHORT TERM...This afternoon through Tuesday...

Moderate to locally heavy showers will continue this
afternoon across portions of western PR due to the combination of
local effects and diurnal heating. This activity is expected to
continue across different sections of western PR for the rest of
the afternoon into the early evening hours. Isolated and brief
showers are expected tonight and Monday morning, then afternoon
showers and possible thunderstorms once again on Monday afternoon
across western PR. This general pattern of isolated showers across
the USVI, the local waters and eastern PR while western PR
receives afternoon showers is expected for the next several days
as the shower activity is induced due to the combination of local
effects. Not much change is expected in the max/min temperatures
as they are expected to be near normal.

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

...From previous discussion, with a few updates...

The strong high over the east central Atlantic is already
generating better winds east of the local area. These winds will
arrive by Wednesday along with higher seas. The current ridge
aloft builds back over the local area after the passage of a short
wave trough Tuesday and is followed by a westerly jet Friday
through Sunday. Shower activity, however will remain dependent on
the shallow moisture in the marine layer as mid levels do not
moisten sufficiently until Sunday to yield a significant change in
shower coverage. Currently the GFS shows a break in the moisture
on Saturday, but the GFS has been inconsistent with columnar
moisture beyond Friday. GFS model is no longer showing much
divergence aloft for Sunday, which is typical to see variations in
the long range models, instead it is currently showing some modest
divergence aloft late on Saturday, but by Sunday morning the
divergence is east of the local area. Therefore the model precip
solution has only modest amounts of rain for Sunday over the local
area.


&&

.AVIATION...VFR conditions are expected to prevail across most TAF
sites through at least 09/12z. Increasing cloudiness with showers
can be expected in and around TJMZ and TJBQ from 08/16z through
08/22z. Low level winds will be mainly east southeast at 10 kts
except for sea breeze variations in coastal areas.


&&

.MARINE...Seas are expected to be fairly tranquil with some chop
over the offshore Atlantic waters. Wave heights will be up to 5
feet across the offshore Atlantic waters and the Anegada passage,
otherwise seas will be up to 4 feet for the rest of the local
waters. Wave heights to increase on Tuesday night and Wednesday,
possibly becoming hazardous across the Atlantic waters and Anegada
passage.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 88 74 86 / 40 40 30 30
STT 76 85 75 86 / 40 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Mon Apr 9 2018

.SYNOPSIS...

A mid level ridge will continue to prevail through Thursday with
widely scattered showers across portions of the interior and
western Puerto Rico through Saturday. Other areas could see
isolated showers due to locally induced effects. The low to mid
level moisture returns late on Thursday across the region. On
Friday and Saturday, a combination of low level moisture and an
upper level jet will create showers and isolated thunderstorms
across portions of western and interior Puerto Rico. Other areas
will see isolated to scattered showers.

&&

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

A thin line of widely scattered showers moved into eastern Puerto
Rico in the pre-dawn hours leaving traces in most areas and three
hundredths of an inch in Maunabo as of 4 AM AST. The MIMIC product
shows a concave arc of moisture moving toward the area and presently
stretched out over Culebra and Vieques. At this time it is producing
only isolated showers, but it is expected to produce numerous
showers in western and interior Puerto Rico this afternoon when it
arrives during maximum heating and convergence over the island.
Surface winds turn back to the east and sea breezes should come to
the aid of temperatures trying to find 90 degrees on the north
coast, where they did reach 89 degrees at the airport in San Juan
yesterday. Expect about a degree cooler today on that account.
Moisture drops off quite a bit tonight, then recovers on Tuesday,
but it should be somewhat drier Tuesday afternoon with scattered
showers in western and interior Puerto Rico and isolated if any
shower activity in the U.S. Virgin Islands. At upper levels a weak
trough will pass just north of the area, but little support for
convection is expected and flow will return to a more west northwest
direction on Tuesday morning. Surface winds will increase
noticeably on Tuesday and Tuesday night while moisture remains the
same. Although some convection is expected both Tuesday and
Wednesday it should be more sheared both days due to the increase in
easterly winds at lower levels and persistent westerlies above 30
kft. Urban and small stream flooding is possible in western Puerto
Rico and mudslides remain a threat where debris blocks efficient
drainage.

&&

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

A front well to the north of Puerto Rico will interact with the
mid level ridge on Thursday and create a col region to the
northwest of Puerto rico. During this time the low level moisture
will increase from east to west with the bulk of the moisture
arriving Thursday afternoon and lasting through the weekend.
Friday, the GFS model begins to moisten the mid layers late in
the morning, but Saturday drier air moves in again and remains
through Monday.

Showers will increase due to the increase in low level moisture,
combined with local effects, and diurnal heating. These showers
will occur mainly across portions of western and interior Puerto
Rico through Monday. An upper level jet will position itself just
to the north of Puerto Rico and the U.S. Virgin Islands on
Thursday. Friday, the upper level jet will nose in over the
region with winds ranging from 50 to 70 kts through Sunday
evening. Late Sunday the upper level jet moves off to the
northeast away from the Islands. The aforementioned jet should
create enough instability to cause isolated thunderstorms during
the afternoon on Friday and Saturday. So isolated thunder was put
into the forecast.

&&

.AVIATION... VFR conditions are expected to prevail through 09/17Z.
Aft 09/17Z SHRA will form over wrn and interior PR with mtn
obscurations and MVFR CIGS. MVFR CIGS may occur at TJMZ durg the
period. Sfc winds E 5-15 kt with sea/land breeze influences. Max
winds W 35-45 kt btwn FL340-520 bcmg WNW by 10/12Z.

&&

.MARINE...Seas will remain tranquil today due to seas only
ranging from 4 to 5 feet. On Tuesday the outer Atlantic waters
will increase to 5 to 7 feet due to northerly swell that will move
across the area today. As a result, a Small Craft Advisory will
be in effect starting Tuesday at 2 PM. A high rip current risk is
in effect for Cramer Park and Saint Croix today through Friday
morning. Puerto Rico will begin to see high risk for rip currents
on its northern coasts Tuesday night.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 77 82 77 / 30 30 40 40
STT 86 78 79 78 / 30 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
420 AM AST Tue Apr 10 2018

.SYNOPSIS...

Mid level ridge will prevail over the area through Friday then a
mid level trough will move close to the Islands on Sunday. Low
level moisture will move over the area periodically over the next
several days. Showers and isolated thunderstorms are possible
each day this week as a result of sea breeze convergence and
local diurnal effects.

&&

.Short term...Today through Thursday
Strong surface high pressure ridge across the north central will
Atlantic will maintain a fairly tight pressure gradient across the
region to produce moderate east to southeast trade winds through
Thursday. The prevailing trade winds along with weak easterly
pertubations will therefore continue to bring occasional patches of
low level moisture across the islands and coastal waters during the
period. The mid to upper level ridge in the meantime, will hold in
place creating and overall westerly wind flow aloft.

No significant upper level support in place so expect locally and
diurnally induced showers and possible isolated thunderstorms mainly
over portions of central western PR for the next few days. The brief
periods of locally heavy rains in some of these areas may lead to
minor urban flooding or ponding of water on roadways and in poor
drainage areas. Winds will remain from the east at 10 to 20 mph
except for the local sea breeze variation and higher gusts with
afternoon convection. Elsewhere and around the USVI and coastal
waters, mostly isolated showers of short duration can be expected
with occasionally passing early morning showers each day. Some of these
showers may brush the coastal areas from time to time as they pass
by.

&&

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

A polar trough will transition to a weak shear line north of
Puerto Rico late Thursday. As a result the mid level ridge will
weaken over the region, and allow mid level moisture to moisten
the mid layers of the atmosphere Friday afternoon. The moistening
of the mid layers will be very short-lived as the mid level ridge
rebounds and builds over the region Saturday morning.

Friday looks to be the wettest day in the long term period with
low level moisture moving in from the east and a strong upper
level jet that will move across the Islands. The Upper level jet
will move to the northeast of the area early Sunday as result
upper level winds will also subside. Sunday a mid level trough
will stall just north of the Islands and cause showers across
interior and western Puerto Rico. Monday and Tuesday, lingering
low level moisture combined with local effects and diurnal heating
will cause showers across portions of the interior and western
Puerto Rico. Elsewhere, passing showers are possible for most of
the long term period.

&&

.AVIATION...

VFR conditions will prevail across most TAF sites
through the fcst prd. Brief MVFR in SHRA/Isold TSRA ovr ctrl
interior of PR and vcty TJMZ and TJBQ fm 10/17z-10/22z. Low level
winds fm E 15-20 kts BLO FL200. Sfc wnds fm E 10-15 kts higher with
sea breeze variations.


&&

.MARINE...

Today seas will increase to 7 feet with winds of 20 kts across
the offshore waters. Therefore small craft operators should
exercise caution. The local winds will be up to 20 knots across a
larger portion of the local waters on Tuesday and Wednesday which
combined with a northeasterly swell will cause hazardous seas
over the Offshore Atlantic and Caribbean waters as well as the
local passages

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 76 88 76 / 40 40 30 40
STT 86 79 86 78 / 40 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
534 AM AST Thu Apr 12 2018

.SYNOPSIS...
A band of moisture will bring passing showers across the local
waters, the U.S. Virgin Islands and the eastern half portion of
Puerto Rico through the morning hours. Locally and diurnally
induced showers and possibly an isolated thunderstorm are expected
to form across the western interior of Puerto Rico during the
afternoon hours. A high pressure ridge aloft will weakens
throughout the end of the work-week. An easterly wave
perturbation will enhance the potential for shower and
thunderstorm development on Friday.

&&

.Short Term...Thursday through Saturday...
Occasional patches of low level moisture will continue to move
over the islands today under the influence of an east to southeast
wind flow. This will result in showers moving over portions of
eastern PR, including Vieques and Culebra, as well as the U.S.
Virgin Islands in the morning, followed by locally and diurnally
induced showers and possibly isolated thunderstorms across the
interior and western sections of Puerto Rico in the afternoon.
This activity could lead to ponding of waters in roads and poorly
drained areas across these sections.

As the mid level ridge weakens and an easterly wave approaches the
local area, an increase in available tropical moisture will result
in a higher frequency of passing showers over eastern Puerto Rico
and the U.S. Virgin Islands during the morning hours, and enhanced
intensity and coverage of showers and isolated thunderstorm during
the afternoon hours on Friday.

Once the easterly wave moves away, shower intensity and coverage is
expected to decrease. However, a few passing showers remain possible
over eastern Puerto Rico and U.S. Virgin Islands during the morning
hours, while limited shower activity is expected over the interior
and western Puerto Rico on Saturday afternoon.

.LONG TERM...Sunday through Friday...
A migratory high pressure over the Atlantic ocean will maintain a
tight pressure gradient across the local islands through at least
Tuesday. When, a surface low pressure and associated cold front
is forecast to enters the western Atlantic on Tuesday. At upper
levels, a polar trough is forecast to move north of the islands
around midweek.

Moisture levels across the region is forecast to remain around
the normal values for April through at least Tuesday. Under an
easterly trade wind flow patches of moisture will move across the
region at times inducing the typical passing showers during the
overnight and morning hours, followed by diurnal and locally
induced showers across the western interior of PR each afternoon.

A frontal system, forecast to move north of the islands, could
induce prefrontal troughs over the region after mid-week. Model
guidance suggested moisture to increase above normal levels after
mid week, and winds are forecast to shift from the south to
southeast. At this time, the islands seems to be moving into a
more wet and unstable weather pattern by the second part of the
upcoming week. Confidence is moderate at this time.

&&

.AVIATION...
Mostly VFR conditions expected across all terminals. Passing
showers will approach the vicinity of TIST/TISX between 12/12-15Z,
but conditions should remain VFR. Showers and possible VCTS could
bring brief MVFR conditions to TJMZ/TJBQ between 12/15-23z. East
to southeast winds between 10 and 15 knots with gusts around 22
knots will continue.

&&

.MARINE...
Hazardous seas are expected to continue across the outer Atlantic
waters through the weekend. Although marine conditions will
improve somewhat across the regional waters, choppy seas around 7
feet are expected to return by Saturday as model guidance
suggested. Therefore, small craft operators should exercise
caution across the expose local waters due to seas up to 6 feet.

For the beach goers, there is a high risk of rip currents for the
beaches along the eastern half portion of St Croix and a moderate
for most of the local beaches.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 86 75 / 30 30 30 40
STT 85 75 84 74 / 30 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
521 AM AST Fri Apr 13 2018

.SYNOPSIS... A band of moisture with passing showers accompanying
an easterly perturbation will continue westward across the
northeastern Caribbean and affect the region during the rest of
the morning hours and throughout the day. Available moisture along
with local and diurnal effects will support another active
afternoon as showers and thunderstorms develop along the
Cordillera Central and west sections of Puerto Rico. Streamer like
afternoon showers are also expected across parts of the San Juan
Metro, as well as parts of the U.S. Virgin Islands.

&&

.SHORT TERM...Today through Sunday...
Showers and clouds were depicted by radar and satellite imagery
early this morning. This activity is associated with an easterly
perturbation and low level convergence, which is expected to move
across the region throughout the day. As a result shower activity
will continue to affect the the U.S. Virgin Islands, portions of
eastern PR, including Vieques and Culebra, as well as the
surrounding waters. Another round of locally and diurnally induced
showers are expected to develop across the interior and western
sections of Puerto Rico as well as in the San Juan metro area during
the afternoon. This activity could lead to urban and small stream
flooding across the area.

A surface high pressure across the Atlantic ocean will tighten the
local pressure gradient resulting in breezy conditions across the
region through early next week. Under this weather pattern, models
are suggesting patches of moisture embedded in the trades resulting
in passing showers across the U.S. Virgin Islands and eastern Puerto
Rico during the overnight and morning hours. Followed by convection
associated with local and diurnal effects across the western and
interior sections of Puerto Rico during the afternoon hours.


.LONG TERM...Monday through Saturday of next week...
Surface high pressure will continue shift eastwards into the
central and east Atlantic, as a cold front will enter and cross
the western Atlantic while inducing a surface trough across the
forecast area by Tuesday. By Wednesday and through the latter part
of next week an easterly wave is also forecast to enter the eastern
caribbean and merge with the aforementioned surface trough as winds
become more southeasterly. This expected pattern will bring a significant
increase in tropical moisture across the region. A mid to upper level
polar trough will shift farther east across the region Monday through
Tuesday, while a high pressure ridge builds west of the area and induces
a westerly wind flow aloft by Wednesday and through the end of the week.
Increasing instability aloft is therefore expected by Wednesday and
through at least Thursday as an upper jet segment will move across
the region and provide good ventilation and upper diffluence across
the northeastern Caribbean.

With the unstable conditions aloft along with the induced troughiness
and the approaching easterly wave, expect fairly moist environment and
active weather conditions by mid week. Therefore based on most recent
model guidance and the overall weather pattern, expect increasing
chance for shower activity and thunderstorms development, beginning
on Wednesday and continuing through at least Thursday of next week.
Friday through Saturday...expect a gradual improvement as the upper
level ridge is so far forecast to spread northward across the region,
and the easterly winds return in response to the Atlantic surface
high ridge building north and east of the region.

&&

.AVIATION...SHRA/-SHRA are expected to affect TJSJ/TIST/TISX and
TNCM/TKPK through the morning hours. Brief gusty winds as well as
BKN ceilings could affect these terminals especially in/near SHRA.
Mountain obsc, +SHRA/SHRA and possibly TSRA are expected to
affect the interior and western sections of PR btwn 13/16-23z. As
a result brief MVFR or even IFR conds are possible at TJMZ/TJBQ.
Easterly winds between 10 and 15 knots with gusts around 25 knots
will continue.


&&

.MARINE...Seas up to 7 feet are expected to continue across
the Atlantic offshore waters and in the Anegada Passage later
today and through the weekend. Therefore, small craft advisories
are in effect for these waters. Elsewhere, seas will continue
between 4 to 6 feet and winds will prevail from the east at 10 to
15 kts increasing 15-20 kts through the weekend. A moderate risk
of rip currents will continue for the northern and east facing
beaches of the islands. A high risk of rip currents will continue
for St. Croix through the weekend. A high risk is expected across
the Atlantic beaches of PR during the weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 75 86 73 / 40 40 40 50
STT 85 73 85 75 / 40 40 40 70

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
510 PM AST Fri Apr 13 2018

.SYNOPSIS...Surface high pressure across the western Atlantic will
continue to produce moderate to fresh trade winds across the
region throughout the weekend. Patches of low level moisture will
affect the local region from time to time.

&&

.SHORT TERM...Tonight through Sunday...Mostly sunny to partly
cloudy skies prevailed across Puerto Rico and the U.S. Vrigin
Islands today. Morning showers affected the east section of Puerto
Rico and the northern U.S. virgin Islands. Early in the
afternoon, showers developed across the north central Puerto Rico,
affecting the municipalities of Toa alta, dorado and Catano.
Rainfall amounts were between three quarters to one inch in some
areas. Later, showers with thunderstorms developed once again
across the western interior and western sections of Puerto Rico.
This activity was primarily induced by the combination of daytime
heating and local effects. A similar weather pattern is expected
through Sunday, with mostly sunny skies during the morning hours,
with showers and thunderstorms developing across the western
sections of Puerto Rico during the afternoon hours.


.LONG TERM...Monday through Saturday of next week...(no changed
needed from previous discussion)

Surface high pressure will continue shift eastwards into the
central and east Atlantic, as a cold front will enter and cross
the western Atlantic while inducing a surface trough across the
forecast area by Tuesday. By Wednesday and through the latter part
of next week an easterly wave is also forecast to enter the
eastern caribbean and merge with the aforementioned surface trough
as winds become more southeasterly. This expected pattern will
bring a significant increase in tropical moisture across the
region. A mid to upper level polar trough will shift farther east
across the region Monday through Tuesday, while a high pressure
ridge builds west of the area and induces a westerly wind flow
aloft by Wednesday and through the end of the week. Increasing
instability aloft is therefore expected by Wednesday and through
at least Thursday as an upper jet segment will move across the
region and provide good ventilation and upper diffluence across
the northeastern Caribbean.

With the unstable conditions aloft along with the induced troughiness
and the approaching easterly wave, expect fairly moist environment and
active weather conditions by mid week. Therefore based on most recent
model guidance and the overall weather pattern, expect increasing
chance for shower activity and thunderstorms development, beginning
on Wednesday and continuing through at least Thursday of next week.
Friday through Saturday...expect a gradual improvement as the upper
level ridge is so far forecast to spread northward across the region,
and the easterly winds return in response to the Atlantic surface
high ridge building north and east of the region.


&&

.AVIATION...SHRA/TSRA across PR this afternoon may cause MVFR conds
at TJMZ and possibly TJPS with VCSH/VCTS across the remaining
terminals. East winds at 15-20 knots with sea breeze variations. Wx
improving after 13/23Z. Brief SHRA across the local waters
thereafter may cause brief SHRA at TJSJ, TIST, and TISX overnight.
Winds will remain easterly but at around 10kts overnight, increasing
once again up to 20kt after 14/13Z.

&&

.MARINE...Seas between 5 to 7 feet will continue across the local
waters through the weekend. As a result, small craft advisories
are in effect.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 86 73 86 / 40 40 50 50
STT 73 85 75 86 / 40 40 70 70

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
514 AM AST Sat Apr 14 2018

.SYNOPSIS...
Breezy easterly winds will push a patch of low level moisture over
the islands throughout the day, bringing passing showers at times
over the windward sections of eastern Puerto Rico and the U.S.
Virgin Islands. Local and diurnal effects will aid in the
formation of showers and thunderstorms once again across the
interior and western sections of Puerto Rico during the afternoon
hours.

&&

.SHORT TERM...Today through Monday...
Surface high pressure ridge north and east of the region will
maintain a moderate to fairly strong easterly wind flow across the
forecast area. The prevailing easterlies will bring sufficient
patches of low level moisture across the region through the weekend
to support occasional passing showers and the development of
afternoon convection each day. A broad mid to upper level trough
will continue to lift north and east of the region while a high
pressure ridge will build northward just west of the area through
Monday. The prevailing westerlies aloft will become more
northwesterly by Monday, placing the region on the west side of the
upper trough axis.

Small clusters of low level clouds with embedded passing showers
continued to cross the region this morning carried by the prevailing
moderate easterlies. A few showers briefly brushed portions of the
north and east coastal sections of the islands, but so far no
significant rainfall accumulations have been observed or reported.
For the rest of the morning and early afternoon expected diminishing
cloudiness with mostly sunny skies. However, during the afternoon
hours expect available moisture along with local and diurnal effects
to again support afternoon convection mainly over portion of the
interior and west Puerto Rico as well as around parts of the San
Juan metro where a few clouds and showers may form and quickly
stream westward across these areas. Some of the afternoon convection
particularly over the west interior may be locally heavy with
isolated thunderstorms possible. This may lead to minor flooding and
ponding on waters on roadways and in poor drainage areas.

Sunday through Monday...more of the same expected across the
forecast region on Sunday, with occasional passing early morning
trade wind showers followed by isolated to scattered afternoon
convection mainly over the west interior sections of Puerto Rico.
Elsewhere including the U.S. Virgin islands expect mostly sunny and
fair weather skies except for a few showers of short duration which
may quickly form on the down wind side of the islands and stream
westward over the coastal waters. By late Monday and thereafter,a
surface trough is forecast to gradually develop across the eastern
Caribbean as the surface ridge will weaken and lift north of the
area. This will increase the chance for localized convection and
moisture convergence across the region.

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

A cold front across the western Atlantic Ocean is forecast to
induce a surface trough across the region on Tuesday which could
merge with the leading moisture of an approaching tropical wave.
This tropical wave is forecast to cross the Lesser Antilles around
early Tuesday, and into the eastern Caribbean through the latter
part of the next work-week as winds become more southeasterly.
Unsettle weather conditions are forecast under this pattern.

A mid to upper level polar trough well north of the region will
induce an jet segment aloft by Thursday into the upcoming weekend,
providing good ventilation across the northeastern Caribbean. If
model guidance are right, an unstable and fairly moist environment
would increase the chance for shower and thunderstorm development
through the second part of the upcoming week.

&&

.AVIATION... VFR conds durg entire prd. Passing -SHRA ovr the
coastal waters and en route btw PR and the nrn Leeward islands.
Isold SHRA ovr E PR til 14/12z. SCT ocnl BKN cld lyrs nr FL022...
FL040..FL080. Few tops 120-150...mostly SKC ABV Fm 14/17z-14/22z
SHRA/psbl TSRA ovr central and W interior of PR impacting mainly
TJBQ/TJMZ with Isold VCSH at TJSJ. L/lvl wnds fm E blo FL150 btw
10-25 kts bcmg WNW ABV and incr with height.

&&

.MARINE...
Small craft advisories are in effect for the offshore Atlantic and
Caribbean waters and the Anegada Passage due to seas between 6
and 8 feet with occasional seas up to 10 feet. The wind will blow
from the east at 15 to 20 knots. Rough and choppy seas are
forecast to continue through at least Monday. Therefore small
craft operators are urge to exercise caution across most of the
local waters.

For the beach goers, a high risk of rip currents is expected from
the northwest to northeast coast of Puerto Rico and for the
beaches of the eastern half portion of St Croix through at least
Sunday evening.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 76 86 75 / 40 40 40 40
STT 85 74 86 76 / 40 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
411 PM AST Sat Apr 14 2018

.SYNOPSIS...Strong easterly winds will continue to dominate the
local region through Monday. A patch of low level moisture will
exit the local area Sunday morning. A cold front will exit the
east U.S coast by Monday, weakening the pressure gradient.

&&

.SHORT TERM...Tonight through Monday...Variably cloudy skies
prevailed across and the U.S. Virgin Islands today. A patch of low
level moisture moved across the region late this morning,
producing isolated to scattered showers across the region. Later
in the afternoon, a streamer formed from Trujillo Alto through
Vega Baja. Rainfall accumulations were between one to two inches.
This patch of low level moisture will exit the local area by
Sunday morning. A slot of dry air is expected to encompass the
region Sunday morning into the afternoon hours. Some shower
development is expected in the western interior section of Puerto
Rico Sunday afternoon. Another patch of moisture embedded in the
trades is forecast to affect the region on Monday.

.LONG TERM...Tuesday through Sunday...(No overall changes from
previous discussion).

A cold front across the western Atlantic Ocean is forecast to
induce a surface trough across the region on Tuesday which could
merge with the leading moisture of an approaching tropical wave.
This tropical wave is forecast to cross the Lesser Antilles around
early Tuesday, and into the eastern Caribbean through the latter
part of the next work-week as winds become more southeasterly.
Unsettle weather conditions are forecast under this pattern.

A mid to upper level polar trough well north of the region will
induce an jet segment aloft by Thursday into the upcoming weekend,
providing good ventilation across the northeastern Caribbean. If
model guidance are right, an unstable and fairly moist environment
would increase the chance for shower and thunderstorm development
through the second part of the upcoming week.

&&

.AVIATION...Passing SHRA will briefly affect TIST, TISX, and TJSJ
terminals through 14/22Z, causing very brief MVFR conds as the
showers pass by. SHRA/TSRA possible across western PR after 14/18Z,
which could affect TJBQ and TJMZ, causing brief MVFR conds through
14/21Z. Winds will remain mainly from the east at 15-25KT with
higher gusts through 14/23Z. Winds to decrease to 10-15KT and
weather to improve after 14/23Z.

&&

.MARINE...Seas up to 8 feet has been observed across the offshore
Atlantic waters. Seas between 6 to 8 feet will continue through at
least Monday night across most coastal waters. Small Craft
advisories continue in effect.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 76 86 75 86 / 40 40 40 20
STT 74 86 76 85 / 40 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
513 AM AST Sun Apr 15 2018

.SYNOPSIS...
Breezy easterly winds will push a patch of moisture with clouds
and showers across the U.S. Virgin Islands and eastern Puerto Rico
through mid morning, when a patch of a dry air is expected to
filter from the east over the islands. During the afternoon hours,
local effects and diurnal heating will result in another round of
showers and thunderstorms across the west and interior sections
of Puerto Rico as well as downwind from the Virgin Islands. The
local weather will be dominated by an advective pattern through
late Monday night.

&&

.SHORT TERM...Today through Tuesday...
Dominant surface high pressure across the Atlantic will maintain
moderate to strong easterly winds across the forecast area. The
prevailing easterlies will continue to bring frequent patches of low
to mid level clouds and embedded showers across the region the rest
of the weekend and into early next week. Some of the showers will
continue to be enhanced by the upper trough which will linger north
and east of the area through Monday. The trough is forecast to lift
further northeast while weakening on Tuesday, as a high pressure
ridge builds northward just west of the area. Northwesterly winds
will then prevail aloft maintaining the region on the west side of
the upper trough axis.

Mostly cloudy skies and passing showers moderate to locally heavy at
times will move through the area during the rest of the morning
hours transported by the brisk easterly trade winds. These showers
will move inland from time to time and may lead to ponding of water
on roadways and poor drainage areas as well as hazardous driving
conditions. A gradually clearing is expected by late morning. During
the afternoon expect the available moisture along with local and
diurnal effects to support convective development mainly over
portion of the interior and west sections of Puerto Rico as well as
isolated areas around the San Juan metro. Some of the afternoon
shower activity may be locally heavy with isolated thunderstorms
possible. The heaviest rainfall may lead to quick rises in water
levels in small rivers and streams, as well as minor ponding on
water on roadways and in poor drainage areas.

The overall moisture advective weather pattern is expected to change
on Monday and Tuesday as the easterly trades will gradually diminish
as the Atlantic high pressure ridge lifts northward and relaxes the
local pressure gradient. A cold front is forecast to enter and move
across the western Atlantic while inducing a surface trough which
will build northwards across the Eastern Caribbean. Winds are then
expected to become southeasterly. This unfolding pattern along with
an approaching tropical wave will enhance low level convergence and
increase instability across the region by late Tuesday. Until then
expect sufficient moisture transport to support periods of morning
and afternoon convection each day with the heaviest rainfall focused
over the central mountain range and west sections of Puerto Rico.
Elsewhere including the U.S. Virgin islands expect a mixture of
sunshine and clouds with chance of mostly isolated afternoon showers
in the form of streamers mainly downwind and on the west end of
the adjacent islands.

.LONG TERM...Wednesday through Sunday...
Model guidance continues suggesting a wet spell by mid-week into
the upcoming weekend, as a cold front, a jet segment and a plume
of tropical moisture combined through this period. If model are
correct, a tropical wave is forecast to reach the islands by
Wednesday into Thursday providing ideal conditions for the
development of organize convection. A mid to upper level polar
trough well north of the region will induce an jet segment aloft
by mid-week into the upcoming weekend, providing good ventilation
across the northeastern Caribbean. An unstable and fairly moist
environment would increase the chance for shower and thunderstorm
development through the second part of the upcoming week. Winds
are forecast to veer from the southeast through late Friday.
Improving weather conditions under a trade wind pattern is
forecast to return by late the upcoming weekend.

&&

.AVIATION...
SCT ocnl BKN cld lyrs nr FL025..FL050...FL080 across
the flying area and en route btw islands with passing SHRA/-SHRA.
FEW Top 120-150. Prevailing VFR conds durg prd with brief MVFR en
passing SHRA and ovr interior sections of E PR. Mtn Top obscr due to
low clds and -SHRA til 15/14z. Fm 15/17z-15/22z SHRA/psbl TSRA ovr W
interior of PR impacting mainly TJBQ/TJMZ with Isold VCSH at TJSJ.
L/lvl wnds fm E blo FL200 btw 15-25 kts bcmg fm W ABV and incr with
height.

&&

.MARINE...
Choppy and rough seas are expected to continue through at least
Monday, when seas are expected to slowly diminish. Therefore,
Small Craft Advisories remains in effect for the offshore Atlantic
and Caribbean waters and local Passages through at least Monday.
Winds will continue from the east at 15 to 20 knots with higher
gusts, but winds are forecast to drop around Monday, when a cold
front is expected to move into the western Atlantic.

Beach goers, a high risk of rip currents continues for the
northern beaches of Puerto Rico and St. Croix through late
tonight.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
538 AM AST Mon Apr 16 2018

.SYNOPSIS...Shallow marine moisture and brief passing showers will
be augmented by better moisture on Wednesday and Thursday with a
weak low-level trough passage late Tuesday. The cold front that
left Florida last night will not be able to reach the local area
before it is forced to retreat on Wednesday.

&&

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

An easterly perturbation and associated low level moisture just
east of Guadeloupe will enter the eastern Caribbean during the
next day or so. A cold front entering the western Atlantic is
forecast to remain well to the north of the region as a broad
surface high pressure builds over the east central Atlantic by
midweek. PWAT content is expected to increase from 1.45 inches
today to 1.8 inches by Wednesday evening. East to southeast
steering winds will prevail each day between 10-15 kts. Diurnally
induced afternoon showers and isolated thunderstorms are expected
to develop each day...mainly over the northwest quadrant of Puerto
Rico. Streamers are also expected to develop across the USVI and
over the San Juan metro area from the eastern mountains. Localized
urban and small stream flooding is expected with this activity
each afternoon but mainly in western Puerto Rico. An upper level
trough is expected to enhance convective development over the
region by Wednesday. This trough and the expected increase in
moisture will favor the development of scattered to numerous
showers and thunderstorms across portions of the local waters and
the islands.

.LONG TERM...Thursday through Monday

The conditions bringing the showers and thunderstorms to most
areas of the islands Wednesday will increase slightly and reach a
maximum of Thursday. Most indicators including precipitable water
(PWAT) and the GDFI (Galvez-Davidson Index) will favor the best
chance of thunderstorms and heavier showers on Thursday. This
would also be the day of the most widespread urban and small
stream flooding though, even then, it should be localized to the
most favored areas. On Friday and Saturday the divergence aloft is
no longer favorable and the jet moves east with the passage of a
weak shortwave trough on Saturday. Moisture diminishes after
Saturday as winds at 700 mb turn northeasterly and even surface
flow becomes a little north of east. Precipitable water values
return to those of yesterday or between 1.2 and 1.5 inches for
the rest of the period. This will yield scattered showers
overnight on the windward slopes and coasts and isolated
thunderstorms in the west and interior during the afternoons, but
there should be little more than that until Tuesday of next week.


&&

.AVIATION...Mainly VFR conditions expected to prevail across all
terminals through 16z. However, passing shra could move at times
across TNCM/TKPK/TIST/TISX through the day, causing brief MVFR cigs.
Across the PR terminals, shra/tsra is expected btw 17z-23z across
the NW portions of PR, impacting mainly TJBQ/TJMZ with mtn
obscurations and tempo MVFR conds. ESE winds expected at 10-20
kts blo FL100 with sea breeze variations at the sfc after 14z.
Maximum winds NNW 50-65 kt btwn FL320-470 strongest at FL400 at
16/12Z.

&&

.MARINE...Seas are gradually subsiding with the winds and all
small craft advisories should come down by 2 PM AST this
afternoon. Rip current risk will remain moderate and small craft
will need to exercise caution in some waters. Seven foot seas are
forecast to return to the local outer Atlantic waters by Thursday
afternoon but for no more than 24 hours.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 74 87 75 / 50 40 40 40
STT 85 76 86 76 / 40 40 40 50