Caribbean - Central America Weather

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 https://twitter.com/FrancoPSE/status/846083295226007552

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More activity in the same area.

 https://twitter.com/CycloforumsPR/status/846116531482308608

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 https://twitter.com/MSotomayor11/status/846104713078738946

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NWS confirms the small Tornado.

Weather Summary for Puerto Rico
National Weather Service San Juan PR
618 PM AST Sun Mar 26 2017

Isolated to locally scattered showers were observed over and north
of the Cordillera Central this afternoon. . Winds were
west southwest at 10 mph with some sea breeze variation .Even a brief tornado
was also reported in Villa Andalucia, Trujillo Alto.
Temperatures were in the mid to upper 80s along coastal areas.

[cycloneye]

[cycloneye]

AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
401 AM AST Mon Mar 27 2017

.SYNOPSIS...A surface low over the Atlantic waters northwest of
PR will continue to move north northeast into the western Atlantic for
the next few days. A surface high will build across the Western
Atlantic just northwest of the surface low, spreading into the
local area by midweek as the surface low moves east into the
central Atlantic. Drier air at mid levels is expected to continue
moving in through the end of the week. Light southerly winds will
continue until Monday, becoming very light on Tuesday, then
northerly and increasing on Wednesday and Thursday.

&&

.SHORT TERM...Today through Wednesday...
Doppler weather radar indicated isolated to scattered showers
moving northward from the Caribbean waters across the U.S. Virgin
Islands, Vieques, Culebra as well as across the eastern sections
of Puerto Rico overnight and early this morning. However, no
significant rainfall amounts were measured. Elsewhere over land
areas not significant precipitation was detected.

A surface low pressure system to the north of Hispaniola this
morning will continue to bring a relatively moist southerly wind
flow across Puerto Rico and the U.S. Virgin Islands today. Less
cloud cover is expected today across the region and therefore
diurnal heating in combination with sea breeze convergence and
other local effects will induce the development of showers and
possible thunderstorms along and north of Cordillera Central,
including the San Juan Metro area during the afternoon hours.
Urban and small stream flooding are possible over northern Puerto
Rico. As the low moves further northeastward over the Atlantic
waters, moisture will continue to decrease across the local
islands tonight and Tuesday. However, the lingering moisture in
combination with local effects will induce the development of
some convection each afternoon specially across the interior and
northern sections of Puerto Rico. Due to the expected southerly
wind flow, warmer than normal temperatures are possible across
the northern coastal municipalities of Puerto Rico during the
next few days.

.LONG TERM...Thursday through Monday...
The surface low will continue to move north into the north
central Atlantic on Thursday and the ridge across the western
Atlantic builds north of the islands through the end of the week.
This will generate a northerly wind flow from Wednesday through at
least Saturday. A much drier airmass will prevail over the region
from Thursday through late Friday...this will result fair weather
conditions through this period. East to southeast winds return
from early Saturday through Sunday with moisture increasing from
the southeast...associated with remnants of the surface
low/frontal boundary.

&&

.AVIATION...Brief periods of MVFR conds will remain possible at
the Leeward and USVI TAF sites this morning. SHRA/TSRA expected
aft 27/16z in and around TJMZ, TJBQ and TJSJ. Light and variable
winds are expected overnight. Latest TJSJ sounding indicated a
south southwesterly wind flow at all levels, but very strong
aloft.

&&

.MARINE...Seas will continue to subside this morning. Early this
morning local buoy 41115 in Rincon indicated seas of 5 feet while
bouy 41053 in San Juan indicated also seas of 5 feet. The small
craft advisories were cancelled. A moderate risk of rip currents
will continue to prevail across some areas during the next few
days.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 75 86 77 / 60 40 40 10
STT 84 75 84 75 / 40 40 40 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
248 PM AST Mon Mar 27 2017

.SYNOPSIS...
A mid-low level trough is forecast to swing by the islands the
rest of today into late Tuesday night. This system will be
accompanied by plenty of tropical moisture through at least mid
week. This will combine with a light southerly wind flow to result
in afternoon convection along and to the north of the Cordillera
Central, including the San Juan metropolitan area and Northeast
PR through at least Tuesday. This pattern is expected to change
after Wednesday night, as winds are forecast to become from the
North-Northeast with the formation of a trade wind cap over the
region.

&&

.SHORT TERM...Today through Wednesday...
A surface low is about 380 miles north of Punta Cana and is
moving northeast at about 15 mph. This motion will continue and
perhaps accelerate during the next 48 hours. Bands of convection
will form in the southwest flow around the islands today and
tomorrow, but moisture has diminished somewhat and convection has
been weaker in strength and coverage. There is little consensus in
the models as to where a band might form in the flow tonight, the
GFS wants to have convection form northwest of Puerto Rico after
28/00z and shift to southeast of Puerto Rico aft 28/06z. HiRes
models have scattered showers on both sides of the island. It is
likely that a band will form parallel to the flow however--and
over water--leaving better than one quarter to one half inch of
rain over smaller islands-- if any are in its path and nearby
coasts.

On Tuesday a plume of moisture at 700 mb will form an arc that
travels from Colombia north to the local Caribbean waters from the
west southwest. This plume will enhance the moisture over the area.
Then, during the day Tuesday, with moisture higher and the upper
level jet and trough a little closer conditions will be a little
better even though the GFS is still not putting much divergence
aloft over the forecast area. With strong directional shear near the
surface and good speed shear above 700 mb--albeit decreasing with
time--small showers could develop with land or water spout
potential, once diurnal heating gets underway.

Currently the model trend has been to peak the moisture on Tuesday
but the GFS has been raising its moisture forecast for Wednesday.
Therefore cannot expect too much improvement until Thursday when
drier air will move in from the north. Temperatures on Tuesday will
continue above normal for the north coast despite afternoon
cloudiness, but on Wednesday winds should shift to more northerly as
the low pressure moves east across our longitude and temperatures on
the north coast will return to normal and temperatures on the south
coast will rise by even as much as 5 degrees.

.LONG TERM...Thursday through Monday... The surface low will
continue to move north into the north central Atlantic on Thursday
and the ridge across the western Atlantic builds north of the
islands through the end of the week. This will generate a
northerly wind flow from Wednesday through at least Saturday. A
much drier airmass will prevail over the region from Thursday
through late Friday...this will result fair weather conditions
through this period. East to southeast winds return from early
Saturday through Sunday with moisture increasing from the
southeast...associated with remnants of the surface low/frontal
boundary.

&&

.AVIATION...
SHRA are forming along a sea breeze front in nrn PR and
will generate very localized brief MVFR conds in CIGS/VSBYS. SHRA
will diminish aft 28/00z. Some areas of hir terrain will be
obscured. Aft 28/06z areas of moisture will move thru the USVI and
Leeward islands from the SE to bring brief pds of MVFR in SHRA to
TISX/TNCM/TKPK. Sfc winds SE-S 10 to 15 kt. Maximum winds WSW 55
knots btwn FL290-420, but winds will incrs to SW 30 kt as low as
FL120 by 28/06z.

&&

.MARINE...
Buoy network continues to indicate subsiding seas across the
local waters. Mariners can expect seas at 2 to 5 feet across the
nearshore waters and up to 6 feet across the Atlantic Offshore
waters. Models are bringing a short period northerly swell by mid
week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 86 77 85 / 40 40 10 10
STT 75 84 75 84 / 40 40 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
409 AM AST Tue Mar 28 2017

.SYNOPSIS...A surface low pressure system north of Puerto Rico
will continue to bring a light and moist southerly wind flow
across the region today. A surface trough is forecast move across
the local islands today aiding in the development of showers and
thunderstorms along and to the north of Cordillera Central,
including the San Juan metropolitan through at least tonight.
A drier air mass is expected to encompass the region by mid week.

&&

.SHORT TERM...Today through Thursday...
A surface low pressure system located around 300 miles north of
Puerto Rico early this morning will continue to induce a moist
south to southwesterly flow which in combination with daytime
heating and local effects, will aid in the development of showers
and possible thunderstorms across the northern slopes of Puerto
Rico this afternoon. As has been the last couple of days, the
afternoon activity will be focus mainly across the north and
northeast sections of Puerto Rico including in the vicinity of San
Juan.

The surface low is expected to move northeast away from the area by
late Wednesday. As it move away from the area, a high pressure
system is expected to take control of the weather locally. As a
result, drier and stable weather conditions are expected to return
to the local area by Thursday.

LONG TERM...Friday through Tuesday...
As the surface low just to the north of Puerto Rico and
Hispaniola continues to move further northeastward into the north
central Atlantic, a ridge will begin to build across the region
late in the work week and during the upcoming weekend. This
feature will bring a northeasterly wind flow and a general dry and
stable weather pattern across the local islands through early in
the weekend. The northeasterly wind flow is expected to produce
seasonable temperatures during this period. An east to east
southeast winds will return to the region from late Saturday
through early next week with more moisture transport to produce an
slight increase in cloudiness and showers across the region and
warmer than normal temperatures across the northern coastal
municipalities of Puerto Rico. No widespread or significant shower
activity is expected at in the foreseeable future.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
TAF sites through at least 28/16z. Periods of MVFR conditions can be
expected across TJSJ and TJBQ between 28/16z through 28/22z in SHRA.
Low level winds will continue mainly south at 10 kts or less.

&&

.MARINE...Seas of 3 to 5 feet will continue to prevail across
the Atlantic waters, with seas 2 to 4 feet across the Caribbean
waters. A moderate risk of rip current will continue across the
Atlantic shoreline of Puerto Rico during the next few days. A
northerly swell will arrive across the local waters Wednesday
into Thursday with seas increasing up to 6 feet.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 77 85 75 / 60 20 20 10
STT 83 74 85 73 / 40 20 40 20

[cycloneye]

Final report from the NWS of San Juan about the small Tornado of March 26 in Puerto Rico.

http://www.weather.gov/media/sju/pdf/20 ... iedras.pdf

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
341 PM AST Tue Mar 28 2017

.SYNOPSIS...SFC low to the north of the local area will continue
to promote a southerly wind flow across the local area, bringing
moisture, which is helping the development of showers across the
local islands, especially across central and northern PR when the
moisture combines with the local effects and favorable upper level
conditions. North swell is expected to affect the local waters
late Wednesday and Thursday.


&&

.SHORT TERM...This afternoon through Wednesday...
A surface low is about 380 miles north of Punta Cana and is
moving northeast at about 15 mph. This motion will continue and
perhaps accelerate during the next 48 hours. Bands of convection
will form in the southwest flow around the islands today and
tomorrow, but moisture has diminished somewhat and convection has
been weaker in strength and coverage. There is little consensus in
the models as to where a band might form in the flow tonight, the
GFS wants to have convection form northwest of Puerto Rico after
28/00z and shift to southeast of Puerto Rico aft 28/06z. HiRes
models have scattered showers on both sides of the island. It is
likely that a band will form parallel to the flow however--and
over water-- leaving better than one quarter to one half inch of
rain over smaller islands-- if any are in its path and nearby
coasts.

On Tuesday a plume of moisture at 700 mb will form an arc that
travels from Colombia north to the local Caribbean waters from the
west southwest. This plume will enhance the moisture over the area.
Then, during the day Tuesday, with moisture higher and the upper
level jet and trough a little closer conditions will be a little
better even though the GFS is still not putting much divergence
aloft over the forecast area. With strong directional shear near the
surface and good speed shear above 700 mb--albeit decreasing with
time--small showers could develop with land or water spout
potential, once diurnal heating gets underway.

Currently the model trend has been to peak the moisture on Tuesday
but the GFS has been raising its moisture forecast for Wednesday.
Therefore cannot expect too much improvement until Thursday when
drier air will move in from the north. Temperatures on Tuesday will
continue above normal for the north coast despite afternoon
cloudiness, but on Wednesday winds should shift to more northerly as
the low pressure moves east across our longitude and temperatures on
the north coast will return to normal and temperatures on the south
coast will rise by even as much as 5 degrees.

.LONG TERM...The latest guidance is now suggesting that Wednesday
will not be as dry as it had suggested in the past few days. So
even though the winds are expected to shift to a northerly
direction, this means that the interior and southern sections of
PR have the better chance for afternoon showers. The rest of the
the forecast area should have isolated to briefly scattered
showers. Then fair weather overnight Wednesday into Thursday with
afternoon showers on Thursday afternoon developing across the SW
quadrant of PR, and once again isolated showers elsewhere,
including the USVI. However for Thursday, the latest guidance
still suggests drier air over the local area as a possible frontal
passage pushes through. Fair weather mainly on Friday, then the
front may retrograde on Saturday, increasing moisture
significantly and so will the shower activity over the forecast
area over the weekend.


&&

.AVIATION...SHRA are forming along a sea breeze front in nrn PR and
will generate very localized brief MVFR conds in CIGS/VSBYS. SHRA
will diminish aft 28/00z. Some areas of hir terrain will be
obscured. Aft 28/06z areas of moisture will move thru the USVI and
Leeward islands from the SE to bring brief pds of MVFR in SHRA to
TISX/TNCM/TKPK. Sfc winds SE-S 10 to 15 kt. Maximum winds WSW 55
knots btwn FL290-420, but winds will incrs to SW 30 kt as low as
FL120 by 28/06z.


&&

.MARINE...Seas generally of 3 to 5 feet are to be expected across
the Atlantic waters and local passages, 2 to 4 feet across
southern PR and south of the USVI. The northerly swell expected
late Wednesday into Thursday may cause seas to go up to 6 feet
across the Atlantic waters and local passages.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 77 85 75 83 / 40 20 10 10
STT 74 85 73 83 / 40 40 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
353 AM AST Wed Mar 29 2017

.SYNOPSIS...A surface high across the southwest Atlantic will
push the surface low to the northeast of the region further
northeast well away from the local islands. As this happens, the
local winds will shift to the north northeast today. Lingering
moisture across the region will combine with local effects to
induce the development of showers and possible thunderstorms along
and south of Cordillera Central today. Winds are expected to
become more easterly by the weekend as the surface high drift
eastward while weakening. North swell is expected to affect the
local waters late Wednesday and Thursday.

&&

.SHORT TERM...Today through Friday...
Partly cloudy skies prevailed across the local islands overnight.
Some light passing showers were seen across the Caribbean coastal
waters. Local Area remains under the influence of a surface low
pressure system which was located several hundred miles northeast of
the area. Trailing moisture associated with this feature will
continue to aid in the development of showers and possible
thunderstorms mainly over the Cordillera Central of Puerto Rico. The
difference today it is that the wind has shifted northerly. As a
result,shower activity will be focus mainly over the southern slopes
of Puerto Rico.

As the aformentioned area of low pressure continue to move away from
the area, a drier airmass is expected to encompass the region
Thursday and Friday as a high pressure system builds across the
western Atlantic.

.LONG TERM...Saturday through Wednesday...
A weak surface high pressure is expected to develop across the
central Atlantic early in the weekend to maintain an easterly trade
wind flow across the local islands Saturday and Sunday. At the same
time a surface low emerging across the northeastern United States
seaboard will push the surface high eastward while weakening. As
this happens patches of moisture associated with a frontal
remnants will combine with local effects both days to produce an
increase in cloudiness and shower activity across Puerto Rico and
the U.S. Virgin Islands during the weekend, but at this time not
widespread or significant precipitation is expected during this
period.

As the aforementioned surface low and associated frontal boundary
moves northeastward toward the north central Atlantic, another
stronger surface high is expected to develop and drift across the
western Atlantic. This feature will bring an east northeast trade
wind flow across the forecast area late Monday through at least
Wednesday. An upper level ridge is expected to build and
strengthening over the northeast Caribbean during the weekend and
is expected to persist over the region through at least Wednesday.
This feature will inhibit the development of widespread or deep
convection across the local islands during the forecast period,
but moisture embedded in the trades will continue to combine with
local effects to produce some shower activity across western and
interior Puerto Rico each day.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
TAF sites through at least 29/16z. Periods of MVFR conditions can be
expected across TJPS and TJMZ between 29/16z through 29/22z in SHRA.
Low level winds will be mainly north and northwest at 10 kts or
less.

&&

.MARINE...Seas of 3 to 5 feet will continue to prevail across
the Atlantic waters, with seas 2 to 4 feet across the Caribbean
waters. A moderate risk of rip current will continue across the
Atlantic shoreline of Puerto Rico today and tonight. A northerly
swell will arrive across the local waters late Wednesday into
Thursday with seas increasing up to 6 feet.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 84 75 84 74 / 20 10 10 10
STT 84 74 85 73 / 40 20 20 20

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
410 PM AST Wed Mar 29 2017

.SYNOPSIS...Shower and thunder development still possible across
the eastern interior and southern slopes through the early evening
hours. A generally fair weather pattern will prevail Thu and
Fri with some locally induced afternoon showers across west and
southwest Puerto Rico. Moisture advection is expected the upcoming
weekend.

&&

.SHORT TERM...Tonight through Sat Morning...
Shower and thunder development still possible through the early
evening hours across the eastern interior and southern slopes of
Puerto Rico. With the heaviest showers ponding of water on
roadways and in low lying areas is expected with some rises along
small stream and rivers.

As a surface low across the north central Atlantic moves east
northeast, a surface high will build north of the area. Therefore
low level winds are expected to become more east northeast Friday
and east to east southeast late Saturday and into Sunday. At upper
levels, a mid level ridge will build from the west and hold much of
the upcoming week. Precipitable water will continue to erode under
the prevailing northerly winds. As the low level winds becomes
easterly to east southeast the upcoming weekend, moisture is
expected to advect once again across the forecast area. Therefore,
tonight through Friday mainly fair weather conditions are expected
to prevail with a few locally induced showers across the west and
southwest Puerto Rico. As the moisture increases the upcoming
weekend, the chance for showers will increase, although under a
building ridge there will be hostile environment for thunderstorm
development. As a result, expect passing showers across the USVI and
E PR Saturday morning with showers developing over and west of the
Cordillera Saturday afternoon.

.LONG TERM...Sat thru Wed/issued 353 AM AST Wed Mar 29 2017/
A weak surface high pressure is expected to develop across the
central Atlantic early in the weekend to maintain an easterly
trade wind flow across the local islands Saturday and Sunday. At
the same time a surface low emerging across the northeastern
United States seaboard will push the surface high eastward while
weakening. As this happens patches of moisture associated with a
frontal remnants will combine with local effects both days to
produce an increase in cloudiness and shower activity across
Puerto Rico and the U.S. Virgin Islands during the weekend, but at
this time not widespread or significant precipitation is expected
during this period.

As the aforementioned surface low and associated frontal boundary
moves northeastward toward the north central Atlantic, another
stronger surface high is expected to develop and drift across the
western Atlantic. This feature will bring an east northeast trade
wind flow across the forecast area late Monday through at least
Wednesday. An upper level ridge is expected to build and
strengthening over the northeast Caribbean during the weekend and
is expected to persist over the region through at least Wednesday.
This feature will inhibit the development of widespread or deep
convection across the local islands during the forecast period,
but moisture embedded in the trades will continue to combine with
local effects to produce some shower activity across western and
interior Puerto Rico each day.

&&

.AVIATION...Mostly VFR conds expected to prevail at all TAF sites
through the forecast period. VCTS expected at JPS/JSJ through
29/22z. Light northerly winds tonight and overnight becoming more
easterly by tomorrow.

&&

.MARINE...Tranquil marine weather conditions will persist tonight
with seas below 5 feet and northerly winds at less than 15 knots.
A northerly swell is expected to reach the islands by Thursday.
Therefore the risk of rip currents is expected to increase along
the north facing beaches of PR and the USVI.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 84 74 84 / 30 30 20 20
STT 74 85 73 85 / 30 30 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
412 AM AST Thu Mar 30 2017

.SYNOPSIS...The proximity of an area of moisture associated with a
surface low well northeast of the region is expected to combine with
daytime heating and local effects to induce the development of
shower activity along and south of Cordillera Central this
afternoon. A generally fair weather pattern will prevail on tonight
Friday with some locally induced afternoon showers across west and
southwest Puerto Rico. Moisture advection is expected to increase
again during the upcoming weekend.

&&

.SHORT TERM...Today through Saturday...
Partly cloudy to clear skies prevailed across the local islands
overnight. Some light passing showers were seen across the Atlantic
coastal waters.Some of these showers brushed the northern coast of
Puerto Rico. Rainfall accumulation with this activity was minimal.

For today, high pressure system will take control of the weather
conditions across the region. Drier air will continue to move across
the region from the north, limiting the development of showers
across the area. However, available moisture will combine once again
with daytime heating and local effect, will produce some showers
across the interior and southwest sections of Puerto Rico this
afternoon.

For late Friday into Saturday, an area of moisture is expected to
move from the Caribbean coastal waters to the north and is forecast
to affect the region Friday night into Saturday. Therefore, an
increase in shower activity is expected by that time.

.LONG TERM...Sunday through Thursday...
A surface high pressure across the central Atlantic is expected to
maintain a generally easterly trade wind flow across the region
through late in the weekend. This surface high is expected to drift
rapidly eastward while weakening as a strong surface low and
associated frontal boundary emerge across the eastern United States
seaboard early in the week. This feature is expected to maintain an
east to east northeast low level wind flow across the northeast
Caribbean through at least Tuesday. Another surface high will
develop across the central Atlantic by mid week between two low
pressure systems. One of the low across the north central Atlantic
and the other emerging across the northwestern Atlantic. The
combination of these features will induce a tight pressure gradient
over the region increasing the winds speed across the local islands
Wednesday and Thursday. Patches of moisture embedded in the trades
will combine each day with local effects to induce a new round of
showers and possible thunderstorms especially during the afternoons
hours across Puerto Rico, but not widespread precipitation is
expected. Looking well ahead we can see the repetition of the same
weather pattern of developing surface highs between surfaces lows
until at least the next weekend.

Model guidance suggest that the upper level ridge over the northeast
Caribbean is expected to erode during the weekend allowing more
moisture transport across the local islands Saturday, Sunday and
early in the week. This weakening upper ridge will allow old frontal
boundaries remnants to induce and increase in showers and possible
thunderstorms across the region until at least Monday.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across all
TAF sites through at least 30/16z. Some showers can be expected in
the vicinity of TJPS and TJMZ this afternoon. Low level winds will
be mainly north to northeast at 10 to 15 kts.

&&

.MARINE...Early this morning buoy 41043 indicated a long period
northerly swell of 17 seconds with 7 feet seas. This swell is
expected to impact the Atlantic waters today and tonight, but is
expected to decay rapidly on Friday. This swell will induce a
high risk of rip currents for the northern beaches of PR. Two
additional northerly swells one associated to the surface low over
the Central Atlantic and another one from a low that should enter
the NW Atlantic on Saturday are expected to keep hazardous seas
and marine conditions at the northern coasts of the islands
through the weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 75 85 76 / 20 20 20 20
STT 85 73 85 75 / 20 20 20 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
326 PM AST Thu Mar 30 2017

.SYNOPSIS...An old frontal system will return to Puerto Rico and
the U.S. Virgin Islands Saturday to increase the moisture and
showers activity in the area. The boundary will linger until late
next week. Late next week another boundary is set to approach the
area first to bring a short dry spell then to increase shower
activity ahead of it.

&&

.SHORT TERM...Today through Saturday...Drier air behind an old
frontal boundary will hold through tonight and tomorrow allowing
only a few showers over the local higher terrain of the Cordillera
Central. The sounding revealed a cap strong enough to block even
parcels at maximum heating at 12 kft and current radar shows tops
no higher than this even though it also showed a few showers
moderately heavy for a few minutes at a time. On Friday
precipitable moisture reaches a minimum of just a little more than
one inch before the moisture associated with the old frontal
boundary that passed through earlier in the week returns from the
southeast. This boundary will then stall over the area and weaken
somewhat, allowing scattered showers to persist into next week. A
broad upper level ridge will cover the central Caribbean and
reinforce this mostly dry pattern. A weak ripple in the flow late
Saturday will enhance showers to a small degree.

.LONG TERM...Sunday through Friday...
Ridging at upper levels will persist for much of the week and
then the ridge will move through the area and to the east on
Friday. Several low level features will approach the area. On
Monday a weak front will dissipate just north of the area with
little effect. A second front will likewise weaken north of the
area on Thursday but will push the weakening frontal boundary and
its associated moisture over the area a little farther south and
allow some drier air in from the northeast. The approach of a
third front will enhance the convergence ahead of it mainly after
Friday (7 April) and end the drying trend that will have begun
Saturday, (the day after tomorrow).

&&

.AVIATION...SHRA have formed over the Cordillera Central and some
mountain obscurations have occurred over the Luquillo range. But
the air has been to dry for further activity and SHRA are expected
to dissipate before 31/00Z. VFR conds will prevail at all TAF
sites in this drier air mass. Aft 31/16z SHRA will again form over
the hir terrain in PR but VFR should cont thru 31/22Z at all TAF
sites. Sfc winds from the NE at 10 kt with brief gusty winds
and sea breeze variations til 30/23z, then calm/light and VRB winds.

&&

.MARINE...Seas at the outer buoy have risen to above 7.5 feet and
the wave watch model is now running about 2 feet too low there.
Current models show Atlantic seas peaking at around 6 feet on
Friday and the next significant swell trains will not be until
Sunday. Models persist at brining some 7 foot seas to the Atlantic
waters then. Caribbean seas will remain tranquil with winds and
seas remaining below criteria for small craft exercise caution.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 85 76 87 / 10 20 30 40
STT 73 85 75 84 / 10 20 10 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
423 PM AST Fri Mar 31 2017

.SYNOPSIS...An old frontal boundary greatly weakened with time,
will return to the local area on Saturday and linger until
Wednesday. On Thursday drier air from the northeast will move in
but convergence ahead of another front crossing Hispaniola will
increase the moisture over the area Friday and Saturday.

&&

.SHORT TERM...Today through Monday...
Moisture associated with an old frontal boundary slowly edging
toward the local area from the east northeast appears tenuous at
best and will likely not affect the local area before Saturday.
Some convection was observed along the boundary as well as an
outflow boundary from that convection about 300-320 miles
southeast of the southeast coast of Puerto Rico. However both the
outflow boundary and the convection are weakening at this time.
Current indications are that this will move into the Mona channel
around midday tomorrow. GFS is indicating that precipitable water
values will increase tomorrow to almost 1.7 inches and that all of
that increase will occur below 22 kft. This will increase the
height that surface parcels will be able to rise tomorrow and
hence the instability of the airmass. So, convection is expected
and possibly even isolated thunderstorms in western interior
Puerto Rico and downstream from El Yunque, but most areas will see
only isolated showers. A similar situation will be encountered
Sunday. On Monday moisture increases slightly over Saturday as the
old boundary re-centers over Puerto Rico--and not so much over
the U.S. Virgin Islands. Flow will then return to the east and
showers will mainly center over the center of Puerto Rico from
west to east.

At upper levels...flow continues out of the west northwest as a
jet streak passes well to the north of the area and the upper
level ridge continuing over the central Caribbean. This will also
not contribute to the showers that will form Saturday through
Monday.

.LONG TERM...Tuesday through Sunday...
Moisture will peak just ahead of the passage of a weak short wave
at upper levels. Precipitable water then plunges from the highest
of the week (Tuesday) to the lowest of the week (Thursday) with
shower activity closely conforming to the moisture level. On
Friday a parcel of moisture will come out of the Anegada passage
or just south of it and increase as it passes mainly south of
Puerto Rico in response to a cold front coming out of Florida.
This front stalls over the weekend near the windward passage.

&&

.AVIATION...Sea breeze induced moisture convergence ovr the central
MTN range of PR will increase aftn cloudiness with SCT-BKN cld lyrs
FL025...FL050...and ISOLD-SCT SHRA there. VCSH for light SHRA psbl
nr TJSJ/TJMZ til 31/23Z as well as TNCM and TKPK. Few streamer
like clds en route and downwind of USVI but mostly VFR. Except for
local sea breeze variations...SFC winds fm E 10-15 kt...bcmg
lgt/vrb ovr land fm 31/23z-01/14z. Wnds fm NE 5-10 kts blo
FL100...bcmg NW and incr w/ht ABV. Max wnds fm NW 50-60 kts nr
FL350. No sig wx impacts ovr flying area attm.

&&

.MARINE...Swell from the north northeast will increase beginning
Saturday morning through Sunday--diminishing on Monday. Small
craft advisories will likely begin Saturday night and continue
into Monday. A second significant wave train is expected by
Thursday of next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 87 75 88 / 10 20 20 20
STT 74 85 73 86 / 10 10 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
442 AM AST Sat Apr 1 2017

.SYNOPSIS...A mid to upper level ridge will continue to dominates
the local islands through the forecast period. Low level moisture
associated with the remnant of an old frontal boundary will
affect the region today. Very dry weather conditions are expected
for the early part of next week.


SHORT TERM...Saturday through Tuesday Morning...

Mostly clear skies prevailed across the local islands overnight and
early this morning with shower activity noted across the Caribbean
waters. Winds were light and variable with coastal temperatures in
the mid 70s.

A mid to upper level ridge will hold across the local islands
through the forecast period. At lower levels, as a high pressure
north of the area moves eastward, low level winds will become east
southeast. This will result in moisture convergence across the local
islands through the weekend. Although another surface high will
build north of the area early next week with an east northeast wind
flow returning to the area, the low level moisture convergence will
continue.

Therefore, through early next week and under precipitable water
values near or above the normal range as well as a lack of upper
level dynamics, shallow convection will prevail each day. As the
moisture increases from the southeast, expect passing showers across
the USVI and E PR particularly in the morning and evening hours.
Shower development is expected each afternoon mainly across central
Puerto Rico due to sea breeze convergence, diurnal heating and the
aforementioned moisture advection. Afternoon showers are expected in
the vicinity of the San Juan Metro Area today under east southeast
winds.

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

An area of cloudiness with showers is expected to linger across
the region from Tuesday through at least Thursday. This area of
moisture will aid in the development of showers, but overall
pleasant weather conditions are forecast to prevail across most of
the area. In the later part of next week, a cold front will move
southeast across the Bahamas and will approach the local region by
next weekend.

&&

.AVIATION...VFR conds expected to prevail at all TAF sites through
01/16z. SHRA expected in and around JSJ/JBQ between 01/16-22z with
brief MVFR conds possible. East southeast winds at around 10 knots
with some sea breeze variations expected today.

&&

.MARINE...Local buoy observations indicated seas between 3 to 5
feet continues across the local waters. Latest model guidance
indicates seas will deteriorate later today into Sunday. As a
result, Small craft advisories are in effect for most coastal
waters. Moderate risk of rip current is expected across most local
beaches of Puerto Rico and the U.S. Virgin Islands.

&&

.CLIMATE...March 2017 ended as the 2nd wettest March on record at
Cyril E. King AP in St Thomas with a rainfall total of 5.83 inches.
Wettest March on record - March 2004 with 6.23 inches.

March 2017 also ended as the wettest March on record at Henry E.
Rohlsen AP in St Croix with a rainfall total of 6.40 inches. This
broke the old record of 4.15 inches set in March 1985.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
451 AM AST Sun Apr 2 2017

.SYNOPSIS...A band of moisture associated with an old frontal
boundary will enhance shower activity mainly over the interior of
Puerto Rico through Monday. Drier air will filter in from the
northeast beginning late Tuesday as high pressure moves into the
central Atlantic.

&&

.SHORT TERM...Sunday through Wednesday Morning...

Rain-free conditions and clear skies prevailed across the local
islands overnight and early this morning. Winds were light and
variable with coastal temperatures in the mid 70s.

A mid to upper level ridge will hold across the local islands with
some weakening expected by midweek. At lower levels, as a high
pressure across the central Atlantic and east of the area moves
eastward, another high pressure will build north of the area by
Tuesday. This will result in east northeast winds early the upcoming
workweek. An area of low level moisture converge will continue to
prevail across the local islands through at least Tuesday with
precipitable water values near the normal range.

Under this pattern expect a seasonable weather pattern with shower
development over central and west Puerto Rico each afternoon due to
diurnal heating and sea breezes. Some showers are also expected in
the vicinity of the San Juan Metro Area today due to the prevailing
east southeast wind flow.

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

Strong upper level ridge will hold through at least Friday. A cold
front is forecast by computer models to exit the U.S. east coast
by Friday and will move southeast during the next weekend. This
cold front is forecast to move closer to the local area at the end
of next weekend. If the forecast verifies, an increase in shower
activity could occur as this front moves near the area.

&&

.AVIATION...VFR conds expected to prevail at all TAF sites through
02/16z. SHRA expected in and around JSJ/JBQ between 02/16-22z with
brief MVFR conds possible. East southeast winds at around 10 knots
with some sea breeze variations expected today.

&&

.MARINE...Seas up to 7 feet and winds up to 15 knots are expected
to continue across the offshore Atlantic waters and local
passages. Seas between 3-5 feet are expected elsewhere. Small
Craft advisories continues in effect.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 76 86 75 / 20 30 20 30
STT 84 74 85 75 / 20 30 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
342 PM AST Sun Apr 2 2017

.SYNOPSIS...A band of moisture associated with an old frontal
boundary will enhance shower activity mainly over the interior of
Puerto Rico Monday and Tuesday. Drier air will filter in from the
north and northeast beginning late Tuesday as high pressure moves
into the central Atlantic. Moisture will begin to return next
Sunday when a strong cold front pushes into Hispaniola.

&&

.SHORT TERM...Today through Tuesday...
The surface high pressure to the northeast of the local area
continues to weaken as another surface high pressure moves into
the western Atlantic to the north northwest of the local area.
Afternoon shower development is expected over PR after the
available moisture combines with the local effects and diurnal
heating. Broad high pressure in the upper levels should limit the
intensity of the convection, keeping the chances of thunderstorms
fairly low since there is not a whole lot of upper level support
for thunderstorms at the moment. However, moderate to locally
heavy showers are very possible.

For this afternoon, the local effects and diurnal heating have
combined with the available moisture to cause showers in Puerto
Rico`s interior. With normal moisture and abundant sun urban and
small stream flooding will be likely despite relatively dry mid
levels. But by tonight, most of the locally induced showers will
have dissipated, leaving only brief showers to affect the north
and eastern sections of PR in the overnight hours.

The local winds will turn more east northeast tonight, but we can
expect isolated morning showers across the USVI and the northern
and eastern sections of PR. Afternoon showers will again develop
across the interior into the western sections of PR when the local
wind flow combines with the local effects and available moisture,
similar to what we expect for today including locally heavy
showers and the possibility of urban and small stream flooding,
but with the ENE winds and slightly breezier conditions, the
temperatures should remain in the mid 80s for the northern coast
including the San Juan airport and the USVI. It will be warmer in
the south and western sections of PR.

Latest guidance suggests that a patch of moisture could be passing
through the local area on Tuesday with the ENE winds still prevailing
over the area. Showers will be isolated in the morning but during
the afternoon shower development is once again expected to be
locally induced, so the interior and western sections of PR have a
chance of showers, while there is only a slight chance of showers
across the USVI.

.LONG TERM...Wednesday through Tuesday...
A broad ridge is found entrenched over northern South America and
the central Caribbean on Wednesday. It slowly drifts east and
through Puerto Rico and the U.S. Virgin Islands by Friday morning
with relatively dry weather and sparse showers. Its passage opens
the way for a deep trough to leave Florida and move to Hispaniola
by the following Tuesday accompanied by rapidly rising columnar
moisture Sunday through Tuesday and increasing probabilities for
showers. In fact, the tail of a weak jet will pass over Puerto
Rico and the USVI on Monday night.

&&

.AVIATION...VFR conds across the local terminals for the next 24
hours. Afternoon convection is possible, which would cause VCSH
near TJMZ, and TJPS. Winds will be from the ESE to SE at around 10
KT with sea breeze variations until around 03/00Z. Thereafter,
the winds will become more from the E to ENE and decrease to about
5 KT for the overnight period with trade wind SHRA causing VCSH
across the USVI terminals as well as TJBQ and TJSJ on occasion.
Maximum winds next 24 hours will be west around 60 knots at FL400.

&&

.MARINE...Seas are peaking now and are expected to fall fairly
rapidly overnight. Seas at buoy 41043 was almost 10 feet at 6 AM
AST, but have relaxed to 7.6 feet now. This will fall will be
reflected in our local waters shortly as swell are still from the
north. Another weaker pulse is expected to move in late Tuesday.
This episode will also be shorter and periods of the swell will be
shorter as well. Seas generally decline after Wednesday through at
least next Sunday though swell remains northerly. Easterly seas
and swell will increase gradually in the Caribbean through
Wednesday but are expected to be no more than 3 to 5 feet except
where north swell moves in through the wider passages.

&&

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

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
339 AM AST Mon Apr 3 2017

.SYNOPSIS...An area of moisture associated with an old frontal
boundary will enhance shower activity mainly over the interior of
Puerto Rico during the afternoon hours today and Tuesday. Drier
air will filter in from the north and northeast beginning late
Tuesday as high pressure moves into the central Atlantic. Moisture
will begin to return next Sunday when a cold front pushes into
Hispaniola.

&&

.SHORT TERM...Rain-free conditions and clear skies prevailed
across the forecast area except over northeast Puerto Rico where
few passing showers were observed. However, Rainfall accumulations
associated with these showers were minimal. Winds were light and
variable with coastal temperatures in the mid to upper 70s.

A mid to upper level ridge will hold across the forecast area
through the end of the workweek. This feature is forecast to erode
Friday and into the upcoming weekend as a broad mid to upper level
trough moves across the western Atlantic with its associated surface
front approaching the local islands Saturday. A building surface
high north of the area will promote east northeast winds through at
least midweek, resulting in near normal temperatures along the north
coast of Puerto Rico.

Therefore, under ridge aloft and near normal precipitable water
expect a seasonable weather pattern with shower development over
central and west Puerto Rico each afternoon due to diurnal heating
and sea breezes.

.LONG TERM...A ridge will prevail over the local region from
Wednesday through the incoming weekend. Guidance suggest that this
weather scenario will change as a trough will move from NW. This
weather feature will increase the chances of rain for next Sunday
through Wednesday.

&&

.AVIATION...VFR conds expected to prevail at all TAF sites through
03/16z with VCSH possible at JSJ/IST early this morning. SHRA
possible in and around JBQ/JPS between 03/16-22z with brief MVFR
conds. East northeast winds at around 10 knots with some sea breeze
variations expected today.

&&

.MARINE...Seas will continue subside today. Seas up to 6 feet are
expected across the Atlantic waters today. There is a High Risk
of Rip Currents for northwest to northeast facing beaches of
Puerto Rico and Culebra until at least this afternoon. There is
also a high risk of rip current for St Thomas and St. John also
until this afternoon.


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
341 PM AST Mon Apr 3 2017

.SYNOPSIS...The old boundary that has been hovering over the area
for the last 48 hours or so will begin to move south again Tuesday
and Wednesday. This will allow drier air to filter in from the
north and east through Thursday. Not withstanding sufficient
moisture will remain to allow convection each afternoon in the
western and interior portions of Puerto Rico. Showers will
increase as areas of moisture will begin to form Friday through
Sunday as a front approaches from the northwest. Current
indications are that this front may be able to pass mid-week next
week.

&&

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

SFC high pressure across the western Atlantic will drift to the east
and north of the local islands, tightening the local pressure
gradient as winds become more easterly for the first half of the
week. High pressure in the upper levels will continue to dominate
for the next several days, which should limit the convection to
that which is locally induced. Available moisture will be near
normal but it should be enough for the development of moderate to
heavy showers once it combines with the local effects and diurnal
heating.

The local winds will continue from the ENE today, which caused some
showers across the north and eastern sections of PR in the morning
and now showers west, and a few sections of southern and central PR
this afternoon. Some of these showers could cause urban and small
stream flooding before all showers dissipate around 8 AM AST. The
eastern sections of PR and the USVI could observe isolated
showers and not as persistent as those developing over central and
western PR.

Latest guidance suggests that the overall moisture should remain
near constant, at about 1.3 to 1.4 inches of precipitable waters for
Monday and Tuesday, but it will be drier on Wednesday with
precipitable water dipping down to 1.15 inches according to the
GFS model. Hence, with no other big change in the overall
pattern, the weather on Tuesday should be similar to the weather
today with the exception that the wind will be more easterly so
the showers should follow that pattern and affect more of the
interior and western sections of PR. However as Wednesday will be
a bit drier, the afternoon convection over PR is expected to
produce more modest shower activity and more limited coverage,
mainly across western PR with less coverage across the rest of
the local islands.

Through this first half of the workweek, the USVI should observe
only isolated to scattered brief showers. The relatively dry airmass
and the high pressure aloft is just too much for significant
showers to develop and affect the USVI, except in cases where the
showers develop over the islands due to the local effects and
affect the western portions of Saint Thomas and Saint Croix before
they stream off into the waters.

.LONG TERM...Thursday through Tuesday... After a weak short wave
moves through Tuesday night, high pressure aloft and the surface
high northeast of the area will contribute to a drying trend that
should bottom out on Friday morning coincident with the passage of
a decaying ridge.

A cold front will move out of Florida on Thursday and then
decellerate as it approaches the area. As it approaches, patches
of moisture will form in the induced upward vertical motion ahead
of the front and the added moisture brought by southeast flow.
This will increase shower chances through the weekend and beyond.
At this time the GFS suggests that the cold front will pass
through the area mid- week bringing cooler and much drier air
behind it.

&&

.AVIATION...Mainly VFR conds across the local terminals thru
04/16z. Afternoon convection is likely, which would cause VCSH
across TJSJ, TJMZ, and TJPS, with TEMPO MVFR at TJMZ possible
today and Tuesday. Winds will be from the ENE at around 15 KT
with sea breeze variations until around 04/00Z. Thereafter, the
winds will remain from the ENE but slightly lighter til 04/14Z with
brief SCT SHRA causing VCSH across the USVI terminals as well as
TJBQ and TJSJ. After 04/12Z local winds become slightly more
easterly at around 15 KT.

&&

.MARINE...Low pressure moving into the north central Atlantic
ocean has sent another pulse of northerly swell toward the western
tropical Atlantic with a tail that will brush Puerto Rico and the
northern U.S. Virgin Islands Tuesday night through Thursday. There
is some difference in timing between the GWW and the WNA and have
chosen the earlier GWW timing . This model did suggest 7 foot
seas as early as 4/18Z, but have discounted that by a few tenths
of a foot to begin most SCAs Tuesday night. Other zones will be
affected but are too far out to begin the SCAs. This event should
be weaker than the previous one and no other events of 7 foot seas
are expected through Tuesday of next week. Caribbean seas will
remain tranquil except as affected through passages by the
northerly swell.

&&

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