Puerto Rico Weather

Area Forecast Discussion
National Weather Service San Juan PR
601 AM AST SUN JUL 10 2016

.SYNOPSIS...A tropical wave moving through the windward islands
will move through the forecast area today and early tonight. High
pressure in the Atlantic will continue to drive trade wind flow
through the next 10 days. But any waves moving through the area
mid week or over the next weekend will be weak and weather
processes will be dominated by local and diurnal heating.

At upper levels...A weak upper level low northeast of the area
will dig southwest across Puerto Rico early this week followed by
higher pressure that will persist into the weekend.

At mid levels...High pressure will continue across the sub-
tropical Atlantic. A weak trough just west of the Cape Verde
Islands will move across the local area mid week. A second trough
over the Cape Verde Islands at mid week is expected to move
across the local area early next week. Mid levels are mostly dry
this week.

At lower levels...High pressure in the central Atlantic will be
joined by another high out of the New England states mid week this
week. That high will strengthen as it moves into the north central
Atlantic late this week and next weekend. This will maintain
moderate to fresh trade wind flow over the local area. A tropical
wave over the windward islands early this morning will move
through the local area today and early tonight accompanied by
showers and isolated thunderstorms.

&&

.DISCUSSION...The tropical wave that has been followed across the
Atlantic this past week is now appearing as an arch of showers:
the left side moving into the eastern Caribbean and the right side
moving through the Windward and Leeward Islands. Currently
earthworks is showing lightning activity along the south coast of
the Dominican Republic--likely associated with the wave that
recently passed through here--but no lightning activity is noted
with the wave moving through the lesser Antilles, although some
higher tops are noted in the infra-red satellite imagery. The GFS
models appears to be bringing in the wave faster than the MIMIC
imagery shows the wave to be moving, but the difference is only on
the order of several hours rather than half a day. Also the MIMIC
imagery shows moisture extending well north of the area as the arc
of highest moisture--rather like a shark`s fin--even though the
best convective activity in the satellite imagery is confined to
latitudes south of our area. The GFS does not show humidities as
high over the area today as for yesterday and with the center of
the best activity farther south, am limiting POPs for all but the
northwest section of Puerto Rico. Again it appears that the south
coast of Puerto Rico will be the area least likely to receive
rain.

Divergence aloft at 250 mb does not extend north into our area,
but there is a very weak area northeast of us during the day.
Strong divergence is also seen in the model following the wave at
upper levels.

Synoptic features during the rest of the week are weak and mid-
level moisture is mostly lacking. Although a weak trough moves
through at 500 mb mid week it is not clear there will be much
effect. Another trough moving through early next week may be a
little stronger, but again all features are very weak and the
upper level pattern is rather chaotic. Most convection will be due
to local effects and the diurnal heating pattern. The clearest
feature is the Saharan dust forecast by the NASA GEOS 5 model
that shows dust moving in behind this wave and lasting through at
least Tuesday. This should limit visibilities to 10 to 15 miles
Monday and Tuesday and limit convection to mainly western Puerto
Rico.

&&

.AVIATION...VFR conditions expected early this morning. However,
the moisture associated with tropical wave is forecast to enter the
forecast area late this morning, to increase the potential for
SHRA/TSRA late this afternoon into the afternoon hours. Therefore,
SHRA will affect the leeward/USVI/Eastern PR terminals thru the
morning hours. Followed by brief MVFR conds with BKN-OVC cigs btw
FL025-FL070 at TJBQ/TJSJ/TJMZ thru at least 10/23z. Sfc winds at 10-
20 kt with sea breeze variations/higher gusts in/near SHRA/TSRA.


&&

.MARINE...Most of our local waters will feel the effects of the
passing tropical wave with seas of 3 to 6 feet and winds up to 20
knots and higher gusts near thunderstorms. Conditions will relax
slightly but high pressure will continue to drive moderate to
locally fresh trade winds through the week, with the quietest
period around mid-week. Small Craft Advisories are not expected
for the next 10 days.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 77 90 78 / 60 50 10 20
STT 90 78 91 79 / 40 30 20 30

Area Forecast Discussion
National Weather Service San Juan PR
450 AM AST TUE JUL 12 2016

.SYNOPSIS....Mid to upper Upper level ridge will hold across the
region today, then slightly erode on Wednesday and Thursday as a
weak tutt will shift westward across the forecast area. Upper level
ridge is to then build across the region once again by Friday and
into the weekend. Surface high pressure ridge across the Atlantic
will maintain light to moderate east to northeast winds at least
through Wednesday,then increasing during the rest of the week as
the local pressure gradient tightens. A weakly induced surface
trough will move across the forecast area Wednesday and Thursday.
Meanwhile,suspended Saharan dust particulates will continue to
affect the islands and surrounding waters today then gradually
diminish and disperse on Wednesday and during the rest of the work
week. Hazy conditions will therefore persist across the region
today.

&&

.DISCUSSION...Light passing showers were observed developing over
the coastal waters and moving southwest across portions of the
islands. So far rainfall accumulations over land were minimal as
the shower activity continued to move rapidly from across the
near shore Atlantic and over the coastal waters between eastern
Puerto Rico and the U.S Virgin Islands. Recent satellite imagery
suggests overall dry and stable conditions will prevail across the
region...as the ridge aloft and saharan air layer will limit cloud
development and significant convective activity. During the rest
of the day, afternoon showers and an isolated thunderstorm will
remain possible but activity should be focused mainly over the
interior and western PR. Lesser or no shower activity is expected
over the Virgin Islands.

A weakly induced trough is still expected to cross the northeast
Caribbean by Wednesday afternoon. This will increase moisture convergence
across the islands and lead to a slight increase in afternoon shower
development over the central interior and western PR, as well as
parts of the San Juan metro area. Another surge of moisture is expected
during the upcoming weekend when a tropical wave is forecast to move
across the eastern caribbean and local region. This will increase
the potential for showers and thunderstorm development during the
weekend.

&&

.AVIATION...ENE flow will bring drier and cleaner air out of the
central Atlantic ocean. SHRA moving through the area will clear from
the northeast 12/10-16Z--a little sooner in the Leeward Islands. Aft
12/17Z SHRA and isold TSRA will form over the western portion of PR-
-mainly in the SW quadrant for lcl and brief MVFR cigs/vsbys with
mtn obscurations. Clrg expected aft 13/02Z. Sfc winds ENE 5-15 kt
bcmg 10-20 kt with higher gusts aft 12/14Z and sea breeze
influences. Winds alf ENE 15 to 25 kt up thru FL190. Winds lighter
but still NE up thru FL360.


&&

.MARINE...Seas between 4 to 6 feet and winds of 15 to 20 knots expected
today. Small craft operators should exercise caution in some areas
due to light to moderate wind chop. Please refer to the latest
coastal waters forecast issued by WFO San Juan PR for additional
info.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 79 90 78 / 30 30 30 30
STT 91 78 88 79 / 30 30 30 30

Area Forecast Discussion
National Weather Service San Juan PR
545 AM AST THU JUL 14 2016

.SYNOPSIS...Surface high pressure across the central Atlantic will
continue to produce moderate easterly trade winds across the
region through the weekend. Tropical wave will move across the
area Saturday.

&&

.DISCUSSION...Isolated to scattered showers were observed across
the coastal waters overnight. Some of these showers affected the
eastern half of Puerto Rico and the U.S. Virgin islands from time
to time. Trade winds will continue to bring patches of low level
moisture across the region today. This moisture in combination
with strong daytime heating and local effects will produce
scattered showers with isolated thunderstorms this afternoon.

Next tropical wave is expected to affect the local area Saturday.
An increase in moisture is then expected...with drier air on
Sunday after the passage of the wave. For the first part of next
week...trade winds showers are expected to affect the region. An
upper level trough will approach the local area from the
east...but at this time no active weather is expected with this
feature.

&&

.AVIATION...Mostly VFR conditions expected across most of the
local flying area. Brief -SHRA across E PR, USVI and Leeward
terminals thru the morning hrs. SHRA/TSRA across western and
interior PR in the afternoon, with MVFR cond and mnt obscurations
across TJMZ/TJBQ. SHRA/VCTS pos for TJSJ as well. Winds from the E
5-15 KTS increasing to 10-15 KTS with higher gusts after 14/13Z.

&&

.MARINE...seas up to 4 feet and winds up to 15 knots are expected
over the coastal waters.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 79 90 79 / 30 20 40 30
STT 82 79 90 80 / 30 40 40 40

Area Forecast Discussion
National Weather Service San Juan PR
540 AM AST SAT JUL 16 2016

.SYNOPSIS...Strong surface high pressure system will continue to
dominates the northeast Caribbean through early next week. Weak
tropical wave will affect the local area today. An active tropical
wave is expected to affect the local region Thursday.

&&

.DISCUSSION...Isolated to scattered showers were observed across
the coastal waters overnight. Some of these showers affected the
eastern half of Puerto Rico and the U.S. Virgin islands from time
to time. This activity is primarily associated with a tropical
wave. Relatively unstable conditions will induce the development
of scattered to locally numerous showers across the regional
waters and parts of the U.S. Virgin Islands and Puerto Rico this
morning. Then...a round of stronger showers and isolated
thunderstorms will affect the interior...north and west portions
of Puerto Rico during the afternoon hours as the the tropical wave
moves across the region.

After the passage of this wave...local area will remain under the
influence of a strong high pressure system. This area of high
pressure will continue to maintain moderate trade winds across the
region. These winds will transport patches of low level moisture
across the area from time to time. It is not until Thursday that a
change in this weather pattern is expected. An active tropical
wave located this morning in the far eastern Atlantic...it is
expected to approach the local area Thursday. GFS computer model
brings deep tropical moisture across the region associated with
this wave Thursday and Friday. It is too early to know exactly how
this wave will affect the local area. Stay tuned.

&&

.AVIATION...Mostly VFR conditions are expected to prevail across
the local flying area through the fcst period. Brief SHRA early
in the morning may cause VCSH over the local terminals until 16/14Z.
TSRA/SHRA will cause areas of MVFR conditions over western and PR
including TJMZ/TJBQ between 16/16z and 16/22z. Mtn obscurations
western and interior PR. E winds at 10 knots or less til 16/13Z...
increasing to 10-15KT after 16/14Z.

&&

.MARINE...Seas up to 5 feet and winds up to 20 knots are expected.
Small Craft should exercise caution mainly across the nearshore
waters due to winds.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 79 89 78 / 50 20 40 40
STT 89 79 90 78 / 50 20 30 30

Area Forecast Discussion
National Weather Service San Juan PR
450 AM AST MON JUL 18 2016

.SYNOPSIS...Trofiness will continue to prevail across the forecast
area through early Tuesday. As the trough aloft moves west, a ridge
pattern will build across the forecast area from the east late
Tuesday and Wednesday. A broad surface high pressure will continue
to dominate the north central Atlantic, this will result in a
moderate easterly wind flow. Tropical wave passages expected late
Monday into Tuesday as well as on Thursday.

&&

.DISCUSSION...Variably cloudy skies were observed across the
local islands during the overnight and early morning hours.
Scattered to numerous showers affected the local waters, with a
few of them moving across the eastern and northern sections of
Puerto Rico as well as the USVI. The overnight temperatures were
in the upper 70s to lower 80s across the lower elevations and in
the upper 60s to lower 70s across the higher elevations.

Continue to expect a seasonable weather pattern across the forecast
area with locally induced showers and thunderstorms each day mainly
across the western half of Puerto Rico. Showers and thunderstorms
are expected each afternoon as the result of available moisture
combined with local and diurnal effects. In addition, showers
embedded in the trades cant be ruled out across USVI and Eastern
Puerto Rico.

Intensity and coverage of these late morning and afternoon showers
and thunderstorms could be enhanced today as trofiness continues to
dominate the eastern Caribbean as well as on Tuesday afternoon as a
weak tropical wave moves across the area. However, the best moisture
advection during the forecast cycle is still expected late
Wednesday/Thursday with another tropical wave passage. As this
feature moves away on Thursday night, a drier air mass will
encompass the eastern caribbean. This will result in fair weather
with hazy skies. Winds will briefly increase with the tropical
wave passages.

&&

.AVIATION...VFR conds expected across the local terminals through
the forecast period with some exceptions. The SHRA activity over
the local area will cause VCSH through 18/14Z at most of the
terminals. SHRA/TSRA possible after 18/17Z which will likely
affect TJMZ causing MVFR conds but also affect the vicinity of
TJPS, TJBQ, and TJSJ. Winds will continue from the ENE at 5-10KT
until 18/14Z, strengthening thereafter to 10-15KT with occasional
gusts.

&&

.MARINE...A surface high pressure across the north central Atlantic
will continue to promote a moderate easterly wind flow across the
regional waters today. Winds and seas will increase slightly on
Tuesday as a weak tropical wave moves across the eastern Caribbean.
Another tropical wave is expected on Thursday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 78 88 80 / 40 40 40 20
STT 90 80 90 80 / 40 20 20 40

Area Forecast Discussion
National Weather Service San Juan PR
429 AM AST WED JUL 20 2016

.SYNOPSIS...Tropical wave is expected to move into the local area
today with the highest amount of moisture moving in after noon.
Surface high pressure over the Central Atlantic will continue to
promote a moderate easterly wind flow for the next few days. Weak
upper level ridge is present over the local islands but a TUTT is
expected to develop on Thursday to the northeast of the Leewards
and it is expected to move to the southwest into the local area by
Saturday. Saharan dust expected to affect the local area late
Thursday into Friday.

&&

.DISCUSSION...Widely scattered showers have been observed during
the overnight hours across the local forecast area. This is due to
the steady increase in moisture as a tropical wave approaches. The
deepest moisture associated with the tropical wave is expected to
move in after noon...causing showers and thunderstorms to move in
and affect the local islands. Also...when combined with the local
effects...thunderstorms are expected across western PR. Moderate
to heavy rain with occasional lightning and gusty winds can be
expected with the thunderstorm activity. The deep moisture is
expected to linger into Thursday morning...which is the reason why
the forecast calls for numerous showers and isolated thunderstorms
into Thursday morning.

Gradual improvement is expected on Thursday...especially in the
afternoon as drier air and Saharan dust begins to move into the
local area. By Friday...the drier air and Saharan dust is still
expected to be over the local area. There is also the TUTT to the
northeast by then which will cause subsidence due to its
positioning...so shower and thunderstorm activity on Friday
and Saturday afternoon is expected to be limited.


&&

.AVIATION...VCSH but generally VFR conditions are expected to
continue through 20/16z. Then sct-num SHRA and TSRA will develop
mainly interior and northwestern PR with areas of mtn obscurations.
Condtions will persist until 20/22z. SHRA/TSRA to increase at the
Leeward and USVI terminals during the afternoon and evening hours
respectively. These SHRA/TSRA expected to reach PR aft 21/00z. Sfc
winds 10 to 20 kt with some sea breeze influences and higher gusts
in TSRA.


&&

.MARINE...Showers and thunderstorms with gusty winds expected over
the waters today into Thursday as the tropical wave passes. Small
craft advisory continues in effect for 7 foot seas across the
offshore Atlantic waters through this evening. Small craft
operators should exercise caution across the rest of the waters
due to seas up to 6 feet and east winds up to 20 knots.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 90 80 / 50 50 50 20
STT 88 80 89 80 / 50 60 50 20