Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
344 PM AST Wed May 10 2017

.SYNOPSIS...The upper level trough is expected to continue over
the local area at least through late Thursday, with an upper level
ridge developing thereafter and for the next several days after
that. SFC shortwave troughs are expected to move through the area
for the next few days. Shower and thunderstorm activity is
expected on Thursday once again. SFC high pressure across the
central Atlantic will keep the local winds from the east to
southeast for the rest of today, shifting to a northeasterly
direction on Thursday.

&&

.SHORT TERM...The above normal moisture has combined with the
upper level trough to cause the showers and thunderstorms that
have affected much of Puerto Rico today and portions of the USVI.
We can expect for these showers and thunderstorms to continue
through the rest of the afternoon. Some of the high resolution
models are indicating additional showers and possible
thunderstorms overnight across the local area and then showers and
thunderstorms across the interior, west, and southwestern sections
of PR on Thursday afternoon. The flash flood watch is still in
effect until 6PM AST this afternoon.

.LONG TERM...Saturday trough Wednesday...From the previous
discussion...

A ridge aloft is expected to build over the region by the
upcoming weekend into next week. However, model guidance quickly
bring a tropical wave with abundant tropical moisture across the
region Sunday or Monday. This scenario can increase the potential
for showers and thunderstorms across the islands. Moisture is
forecast to rapidly decrease Tuesday into mid week. The lingering
moisture will result in periods of showers and thunderstorms
during the afternoons and early evening hours due to the
combination of daytime heating and local effects mainly along the
Cordillera and western sections of Puerto Rico. The U.S. Virgin
Islands, as well as the windward sections of PR, can expect
passing showers mainly during the overnight and early morning
hours each day.

&&

.AVIATION...SHRA/TSRA is present across many sections of the local
area, which is causing VCSH/VCTS across most of the local
terminals. This activity is expected to continue through 10/23Z.
Prevailing VFR conds expected overnight with VCSH likely across
the USVI terminals and TJSJ. Winds will be from the ESE at around
10-15kt for the rest of the day, weakening to 5-10kt overnight.
Winds to shift to a more NE direction by 11/14Z at 5-10kt with sea
breeze variations developing.


&&

.MARINE...Seas are expected to be up to 5 feet across the local
waters for the next few days. Winds will be up to 15 knots today
but showers and thunderstorms are possible over the waters which
could cause local wind gusts near the thunderstorms. There is a
moderate risk of rip currents across the north and east coast of
PR and along most of the coasts of Vieques, Culebra, and St Croix.
High risk of rip currents expected tomorrow for northern PR.


&&

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

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
602 AM AST Thu May 11 2017

.SYNOPSIS...
The proximity of a mid-upper level trough and a surface shortwave
trough with abundant moisture will produce favorable environmental
conditions for the development of widespread showers and
thunderstorms across the islands this afternoon. In addition to
that, soils are already saturated and most of the river levels are
higher than normal, therefore a Flash Flood Watch was issued for
all Puerto Rico. The trough axis aloft is forecast to move over
the Lesser Islands by Friday, positioning Puerto Rico and the U.S.
Virgin Islands in the subsidence area of this feature. As it
moves away, an upper level ridge will develop thereafter and
through the upcoming week.

&&

.SHORT TERM...
Thunderstorms have developed over local waters northeast through
east of Saint John and a few strikes were seen over the outer waters
south of Puerto Rico. This activity has been favored by a strong
upper level trough that has brought cooler air aloft and the
continued presence of moisture behind an old frontal boundary now in
the northern windward islands. Although columnar moisture levels are
falling today through Friday night, there will still be sufficient
moisture to develop showers and thunderstorms across western and
interior Puerto Rico today. The jet around the upper level trough
will be over the Caribbean along the southern boundary of our
forecast area and will contribute to the vigor of the thunderstorms
that develop after noon today. The jet will wane almost immediately
after sunset as the trough passes overnight. Because of the
increased instability over yesterday and the cooler air aloft, there
is a possibility of some small hail in the strongest thunderstorms
this afternoon.

Moisture will continue to diminish Friday and the winds at 250 mb
will reach a minimum at 12/18Z, but divergence associated with the
trough will redevelop over Puerto Rico Friday afternoon. This will
foment another round of showers and thunderstorms, although activity
should not be as intense as yesterday. On Saturday moisture reaches
a minimum and flow aloft turns northwest. Current models suggest
convergence aloft that will aid in subsidence and reduce shower
activity to locally driven effects. Since flow will shift from east
to east southeast at the surface, this will bring the best shower
activity to the northwest portion of Puerto Rico during the
afternoon. Some thunderstorms should still be expected then.

.LONG TERM...Sunday trough Thursday...
A ridge aloft is expected to hold over the region the upcoming
week. However, model guidance quickly bring a tropical wave with
abundant tropical moisture across the region Sunday or Monday.
This scenario can increase the potential for showers and
thunderstorms across the islands. Moisture is forecast to rapidly
decrease by Tuesday into mid week. But, GFS guidance suggest the
formation of a Subtropical Jet by midweek. The combination of
daytime heating, local effects and the available moisture could
produce periods of showers and thunderstorms during the afternoons
and early evening hours along the Cordillera and western sections
of Puerto Rico. Also, the U.S. Virgin Islands, as well as the
windward sections of PR, can expect passing showers mainly during
the overnight and early morning hours each day.

&&

.HYDROLOGY...
The Guanajibo river has crested and should drop below flood stage
of 20 feet by 9 AM AST. Some lakes in Puerto Rico are overflowing
and others have gates opened that are releasing water into rivers
keeping flow abnormally high. Soils are saturated and upwards of
4 inches in very localized areas could fall this afternoon in some
of the same places as heavy rain fell yesterday. We expect a
continued threat of mudslides and some thunderstorms may produce
rainfall amounts that will exceed yesterday despite slightly lower
atmospheric moisture. Therefore a flash flood watch was issued
for mainland Puerto Rico for this afternoon.

&&

.AVIATION...The strong upper trof and ample moisture has prolonged
convection across the FA overnight. TSRA are over local waters
mainly ENE of TIST with tops higher than 50 kft and freq LTGICCCCW.
LLVL flow is now ENE 5 to 15 kt. Aft 11/15Z +SHRA and TSRA will
develop over wrn and interior PR and favor SW PR. Lcly MVFR/IFR
conds with widespread mtn obscurations are expected. Some small
hail in strongest TSRA are psbl. Max winds W 65 to 75 kt at 11/18Z
btwn FL350-480.

&&

.MARINE...
Mariners can expect light to gentle easterly winds with seas of 5
feet or less through the next several days .

For the Beach Goers, there is a high risk of rip currents along
the Atlantic Coastline of Puerto Rico. Refer to the Surf Zone
Forecast for more details.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 76 89 76 / 20 20 20 20
STT 85 75 86 75 / 40 30 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
355 PM AST Thu May 11 2017

.SYNOPSIS...Trough aloft will continue to move away while
weakening. As a result, weather conditions are expected to slowly
improve Friday and into the upcoming weekend. However, locally
induced showers and thunderstorms are still expected each day.

&&

.SHORT TERM...Tonight thru Sat...

Weather conditions are expected to slowly improve across the
forecast area as the broad mid to upper level trough across the
forecast area shifts eastward while weakening. As this feature
moves away tonight and Friday, a mid level ridge will spread
across the local islands to result in a more seasonable weather
pattern. The ridge aloft is then expected to hold across the
forecast area through at least early next week. Under the
influence of the ridge aloft, low level moisture is expected
to erode.

Therefore...A generally fair weather pattern is expected to
prevail during the morning hours across the local islands with
showers and thunderstorms developing each afternoon across
central Puerto Rico. Soils are already saturated, therefore with
the heaviest showers urban and small stream flooding as well as
mudslides in areas of steep terrain are still possible.

.LONG TERM...Sun thru Thu.../issued 602 AM AST Thu May 11 2017/

A ridge aloft is expected to hold over the region the upcoming
week. However, model guidance quickly bring a tropical wave with
abundant tropical moisture across the region Sunday or Monday.
This scenario can increase the potential for showers and
thunderstorms across the islands. Moisture is forecast to rapidly
decrease by Tuesday into mid week. But, GFS guidance suggest the
formation of a Subtropical Jet by midweek. The combination of
daytime heating, local effects and the available moisture could
produce periods of showers and thunderstorms during the afternoons
and early evening hours along the Cordillera and western sections
of Puerto Rico. Also, the U.S. Virgin Islands, as well as the
windward sections of PR, can expect passing showers mainly during
the overnight and early morning hours each day.


&&

.AVIATION...Tempo MVFR/IFR possible at TJPS/TNCM/TKPK through 22z
due to TSRA. Mountain top obscd along the interior/eastern sections
of PR. Mostly VFR elsewhere with periods of -RA/VCSH across the
USVI terminals. SFC winds light with a northerly component, becoming
light and variable overnight.

&&

.MARINE...Seas 3 to 5 feet and easterly winds 10 to 15 knots will
continue to prevail across the local waters tonight. The near shore
San Juan buoy is still indicating a small 12-13 second swell at
around 3 feet. As a result, breaking waves between 5 and 6 feet
are still expected and therefore the high risk of rip currents
continues through late tonight. Tranquil marine conditions will
continue through early next week with seas below 5 feet and
easterly winds 10-15 knots.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 89 76 89 / 40 30 20 20
STT 75 86 75 88 / 40 30 20 20

[tolakram]

Quiet in here.

 https://twitter.com/NHC_TAFB/status/863099482052972544

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
345 PM AST Fri May 12 2017

.SYNOPSIS...A generally fair weather pattern is expected
to prevail each morning, followed by afternoon showers
and thunderstorms each day across central Puerto Rico.
Moisture advection is expected late Sunday and into early
next week.

&&

.SHORT TERM...Tonight thru Sun...

As the mid to upper level trough moves away while weakening,
a mid level ridge will spread across the forecast area. The
mid level ridge is then expected to hold through at least early
next week. At lower levels, a high pressure north of the area
will shift eastward during the weekend to result in east
southeast winds Sun and early next week. This flow will result
in moisture advection beginning Sun and continue through mid
week. In fact, tonight through at least Sun, low level moisture
is expected to remain near or below the normal values.

Therefore, mainly fair weather pattern is expected to prevail
during the morning hours with shower and thunder development
each afternoon mainly across central Puerto Rico the upcoming
weekend.

.LONG TERM...Mon thru Sun.../issued 533 AM AST Fri May 12 2017/

Moisture begins flow back over the area beginning early Saturday
morning and peaks on Monday afternoon. At the same time, although
an upper level ridge moves over us on Monday, areas of moderate
divergence aloft will begin to appear and favor the formation of
showers and isolated thunderstorms. The moisture at lower levels
dips on Wednesday which will be the driest of the week according
to the GFS, but precipitable water never falls much below 1.9
inches and rises to its highest level yet at the end of the next
weekend. Hence, after Tuesday, showers and thunderstorms will
continue in our typical diurnal pattern and increase slowly late
in the week. Then heavy moisture will return.

&&

.AVIATION...Mainly VFR conditions will prevail during the next
24 hours across all terminals. However, brief SHRA/-TSRA still
possible this afternoon across interior PR impacting mainly TJPS.
Low level winds expected from the ENE at 10 knots or less.

&&

.MARINE...Tranquil marine conditions will continue to prevail
across the local waters during the next several days with seas
below 5 feet and winds 10 to 15 knots. There is a moderate risk
of rip currents along the north facing beaches which is expected
to continue through the weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 76 89 77 90 / 20 20 30 30
STT 76 87 78 87 / 20 20 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
514 AM AST Sat May 13 2017

.SYNOPSIS...Isolated showers are expected today. A tropical wave
and southerly flow will replace the dry air in place over the area
with better moisture, producing showers and thunderstorms Monday
and Tuesday. Some of this moisture will linger at lower levels and
southerly flow will produce warmer temperatures next week. Abundant
moisture returns next weekend.

&&

.SHORT TERM...Today through Monday...A low level ridge will
spread across the region through the weekend to induce a light
east to southeast wind flow. Surface high pressure north of the
region will however shift slightly north and east of the area over
the next few days allowing the trade winds to become more
southeasterly by Sunday and Monday. A mid to upper level trough
will continue to fill and lift north and east of the region as a
mid level ridge will spread across the forecast area. The mid
level ridge is then expected to hold through Sunday, then
gradually erode as a polar trough will become amplified and move
eastward across the west Atlantic by Monday.

The prevailing winds will support a slightly drier airmass today
through Sunday with warmer than normal daytime temperatures. Mostly
fair weather skies are expected to prevail during the morning
hours but showers and a slight chance of an isolated thunderstorm
can be expected each afternoon. The activity should be focused
mainly across central and west interior sections of Puerto Rico,
but will later steer northwards towards the coastal areas under
the southeasterly wind flow.

Based on the most recent model guidance, expect increasing low level
moisture advection and instability aloft by late Sunday and Monday
with the approach of an easterly perturbation and the aforementioned
mid to upper level polar trough. This will therefore bring more
favorable conditions for showers and thunderstorms across the
region.

.LONG TERM...At this time the GFS is showing the axis of the best
moisture crossing through Puerto Rico early Monday night. Areas
of moderate to strong divergence aloft will be in place then or
move over the area overnight and into Tuesday. By Tuesday upper
level flow gains a slight southerly component ahead of a trough
that digs into the western Caribbean. Sufficient moisture will be
in place for showers and thunderstorms to continue Tuesday. Then
the GFS continues to run a high level of moisture through the
period with the lowest value for the week ahead coming in around
1.6 inches on Thursday evening. Moisture then returns and peaks
Saturday morning and upper level flow turns southwest again--
with bands of divergence--some strong enough to favor heavy showers
and strong thunderstorms. Although urban and small stream
flooding is possible each day on a localized basis. Currently the
weekend after this looks quite wet and may support more
widespread flooding.

&&

.AVIATION...VFR conds expected durg prd...Isold SHRA en route btw
islands and ovr local Atl and Caribbean waters with a few -SHRA
to brush E coastal sections of PR and adjacent islands til 13/13z.
Winds lgt/vrb bcmg mainly from the E 10-15 kts except for local
with sea breeze variations. Aft 13/14Z chance of SHRA/Isold TSRA
ovr Ctrl Mtn and range of PR with VCSH at TJBQ/TJMZ?TJSJ til
13/22z.

&&

.MARINE...Gentle to moderate winds will increase Wednesday into
Thursday. Although models may still be overestimating wind speeds
over the local waters Thursday, seas may reach 7 feet Thursday in
the outer Atlantic and Caribbean waters. Showers and thunderstorms
will increase Monday into Tuesday diminish through Friday and then
increase Saturday and Sunday. As always, strong gusty winds may be
present around thunderstorms. Rip current risk will be moderate
at most for the next few days.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 77 90 76 / 20 20 30 20
STT 87 78 87 77 / 20 30 30 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
345 PM AST Sat May 13 2017

.SYNOPSIS...The chance for shower and thunder activity will
increase next week as the ridge aloft erodes and moisture
increases from the east southeast. Warm temperatures are
possible along the northern slopes of Puerto Rico through
midweek.

&&

.SHORT TERM...Tonight thru Monday...

Weak ridge aloft is expected to erode during the next few days,
as a broad mid to upper level trough approaches from the west. At
lower levels, a high pressure north of the area will continue to
move eastward to result in east southeast winds through early
next week. Under this evolving pattern, moisture advection is then
expected from the east southeast tomorrow and continue through
midweek.

As a result, passing showers embedded in the moist east southeast
wind flow are possible across windward areas with showers and
thunderstorms developing over and north of the Cordillera Central
each afternoon. As the ridge weakens, intensity and coverage of
these afternoon showers and thunderstorms will increase each day.
With the heaviest rain, urban and small stream flooding is
expected each afternoon. The east southeast wind flow will also
result in warm temperatures along the northern slopes of Puerto
Rico through at least midweek.

.LONG TERM...Tue thru Sun/issued 514 AM AST Sat May 13 2017/

At this time the GFS is showing the axis of the best moisture
crossing through Puerto Rico early Monday night. Areas of moderate
to strong divergence aloft will be in place then or move over the
area overnight and into Tuesday. By Tuesday upper level flow
gains a slight southerly component ahead of a trough that digs
into the western Caribbean. Sufficient moisture will be in place
for showers and thunderstorms to continue Tuesday. Then the GFS
continues to run a high level of moisture through the period with
the lowest value for the week ahead coming in around 1.6 inches on
Thursday evening. Moisture then returns and peaks Saturday
morning and upper level flow turns southwest again-- with bands of
divergence--some strong enough to favor heavy showers and strong
thunderstorms. Although urban and small stream flooding is
possible each day on a localized basis. Currently the weekend
after this looks quite wet and may support more widespread
flooding.

&&

.AVIATION...Mainly VFR conditions will prevail across the
local flying area for the next 24 hours. However, brief
SHRA/-TSRA still possible late this afternoon across interior
PR impacting mainly TJMZ. Latest 12Z TJSJ sounding indicated
light and variable winds all the way from the SFC to around
20k feet...becoming westerlies and increasing with height
above 20k feet.

&&

.MARINE...Tranquil marine conditions will continue to prevail
across the local waters during the next several days with seas
below 5 feet and winds 10 to 15 knots. There is a moderate risk
of rip currents along the north facing beaches which is expected
to continue through early next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 77 90 76 88 / 20 20 30 30
STT 78 87 77 86 / 30 20 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
514 AM AST Sun May 14 2017

.SYNOPSIS...A tropical wave will move west across the Caribbean--
mainly south of the area--today and spread better moisture across
Puerto Rico and the U.S. Virgin Islands this afternoon through
Monday. Then southeasterly flow around the western end of high
pressure over the tropical Atlantic will bring somewhat drier air
over the area through most of the week. Showers and thunderstorms
will increase today and Monday, but will still occur each day in
the northwestern two thirds of Puerto Rico.

&&

.SHORT TERM...Early this morning through Tuesday...
Mainly isolated showers are across the local waters, with only a
few expected to brush some of the islands during the morning
hours. This will be followed by mostly sunny skies during the late
morning and early afternoon. However, with the gradually
increasing low level moisture advection along with local and
diurnal effects, expect showers and possibly isolated
thunderstorms to develop once again over parts of the central
interior and northwest sections of PR. Elsewhere mostly sunny
skies are expected, but some areas may experience isolated
showers of short duration mainly downwind of the islands over the
coastal waters.

The ridge aloft will continue to erode during the next few days,
as a broad mid to upper level trough will become amplified and
move eastward across the west Atlantic. This trough is to linger
just west of the region through Tuesday thereby increasing
instability aloft over the northeastern Caribbean. At lower
levels, a high pressure ridge north of the area will continue to
move eastward resulting in light to moderate east southeast winds
through Tuesday. With this scenario and based on most recent model
guidance, still expect good tropical moisture transport across
the region from the east southeast at least until the middle of
the upcoming week.

As a result, passing showers embedded in the east southeast wind
flow will remain likely across windward areas during the morning
hours, followed by showers and possibly an isolated thunderstorm
developing over and north of the Cordillera Central each afternoon.
Some of the showers and thunderstorms will be enhanced, leading to
periods of locally heavy rainfall. Therefore urban and small stream
flooding as well as rapid rises along some of the major rivers and
their tributaries will remain possible each afternoon. The
prevailing low level southeast wind flow will also support warmer
temperatures along the northern half of Puerto Rico through at least
midweek. Recent dust aerosol product and guidance also continued to
suggest the intrusion of some Saharan dust across the eastern
Caribbean by Tuesday and Wednesday.

.LONG TERM...Wednesday through Sunday
The area will remain under the influence of an upper level high
pressure, which after Tuesday will remain rather close to the
eastern Caribbean south of the local area. High pressure at 700
and 500 mb also remains east southeast of the area through at
least Sunday, and the subsidence generated will bring in drier
air at those levels. The GFS has been very inconsistent about
moisture levels to be expected in the local area. Only yesterday
it showed more moisture over the following weekend than was
expected tomorrow (Monday), but this is no longer the case and
columnar moisture over San Juan is no longer expected to exceed 2
inches after Monday of this week. Since the plume of moisture out
of the equatorial regions is pushing northward over Hispaniola and
eastern Cuba for most of the week now, am accepting this latest
change and have lowered expectations for rain here after mid week
this week. Confidence level, however, is only medium at this
time. Although the plume does draw closer to the local area late
in the week and over the weekend. At least for now, the threat of
widespread heavy rain has been postponed beyond mid week next
week.

That said, however, there will be sufficient heating and moisture
to generate some early morning showers over the local waters and
the southeast coasts and slopes of Puerto Rico and daily afternoon
showers and thunderstorms over the northeastern two thirds of
Puerto Rico. Urban and small stream flooding would be expected
where these showers are the heaviest.

&&

.AVIATION...VFR conds expected til 14/16Z with brief VCSH across the
local terminals. Sfc wnds fm the SE less than 10 KT become ESE
aft 14/14Z at 10-15KT and slightly higher with sea breeze
variations. Between 14/17Z-14/22Z...locally and diurnally induced
SHRA/TSRA possible across central and W-NW PR with mtn
obscurations and VCSH/VCTS at TJMZ/TJBQ/TJSJ and brief MVFR conds
psbl mainly at TJBQ.


&&

.MARINE...Models may still be overdoing the winds Wednesday and
Thursday but are now only expecting borderline small craft
conditions for seas over both the Atlantic and Caribbean waters.
Although this remains a possibility, the most likely seas will be
up to 6 feet peaking on Thursday.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 77 90 76 / 20 30 40 40
STT 86 78 86 78 / 20 30 30 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
345 PM AST Sun May 14 2017

.SYNOPSIS...The proximity of a developing upper level trough west
of the area will increase the chance of shower and thunder activity
early this week. A ridge pattern aloft will strengthen across the
forecast area by midweek. Warm temperatures along the northern
slopes of Puerto Rico will continue during the next few days under
an east southeast wind flow.

&&

.SHORT TERM...Tonight thru Tuesday...

The proximity of a developing mid to upper level trough west of
the area will increase the chance of shower and thunder activity
Monday and Tue. At lower levels, a high pressure north of the
area will continue to move east northeast, resulting in southeasterly
winds through midweek. The trofiness to the west and the east
southeast wind flow will increase the precipitable water near or
slightly above the normal range Mon-Tue.

As a result, passing showers embedded in the moist east southeast
wind flow are possible across windward areas with showers and
thunderstorms developing over and north of the Cordillera Central
each afternoon. As the trough to the west develops, intensity and
coverage of these afternoon showers and thunderstorms will increase
each day. With the heavy rain, urban and small stream flooding is
expected each afternoon. The east southeast wind flow will also
result in warm temperatures along the northern slopes of Puerto
Rico through at least midweek.

.LONG TERM...Wed thru Sun.../issued 514 AM AST Sun May 14 2017/

The area will remain under the influence of an upper level high
pressure, which after Tuesday will remain rather close to the
eastern Caribbean south of the local area. High pressure at 700
and 500 mb also remains east southeast of the area through at
least Sunday, and the subsidence generated will bring in drier
air at those levels. The GFS has been very inconsistent about
moisture levels to be expected in the local area. Only yesterday
it showed more moisture over the following weekend than was
expected tomorrow (Monday), but this is no longer the case and
columnar moisture over San Juan is no longer expected to exceed 2
inches after Monday of this week. Since the plume of moisture out
of the equatorial regions is pushing northward over Hispaniola and
eastern Cuba for most of the week now, am accepting this latest
change and have lowered expectations for rain here after mid week
this week.

&&

.AVIATION...Mainly VFR conditions will prevail across the local
flying area for the next 24 hours. However, brief SHRA/-TSRA still
possible late this afternoon across west and northwest PR
impacting mainly TJMZ/TJBQ. Latest 12Z TJSJ sounding indicated
light and variable winds all the way from the SFC to around 18k
feet... becoming westerlies and increasing with height above 18k
feet.

&&

.MARINE...Tranquil marine conditions will continue to prevail
across the local waters through midweek with seas 4 to 6 feet
and winds around 15 knots. There is a moderate risk of rip
currents along the north facing beaches through Tue, increasing
to high by midweek.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 77 90 76 89 / 20 30 20 50
STT 78 86 78 86 / 30 20 30 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
343 AM AST Mon May 15 2017

.SYNOPSIS...An upper level trough now located to the west of the
local area will increase the chance of shower and thunder
activity early this week. A ridge pattern aloft will strengthen
across the forecast area by midweek. Warm temperatures along the
northern slopes of Puerto Rico will continue during the next few
days under an east southeast wind flow. An area of Saharan dust
will move across the area through at least Wednesday.


&&

.SHORT TERM...Slowly amplifying trough across the western Atlantic
will continue to erode the mid to upper level ridge overhead. This
will create sufficient instability and ventilation aloft to
support convective activity across portions of the local waters
and parts of the islands particularly Puerto Rico during the
afternoon hours through Tuesday. In the low levels...a high
pressure across the central and northeast Atlantic will lift
farther north and east thru Tuesday to create weak troughiness and
prevailing southeast wind flow across the forecast area. This
pattern will maintain a fairly moist low to mid level environment
with precipitable water to remain slightly above the normal. The
Surface High pressure ridge will build and spread north of the
region by Wednesday resulting in a return of moderate easterly
winds and lesser moisture transport across the region.

As a result, passing showers embedded in the east southeast wind
flow will therefore continue across the coastal waters and windward
areas of the islands during the rest of the morning. This will be
followed by showers and possibly thunderstorms developing over and
north of the Cordillera Central each afternoon. The instability
aloft along with daytime heating will continue to support periods of
enhanced afternoon convection mainly over the north central and
western sections of Puerto Rico. Some showers may also form and
stream over the San Juan metro during the afternoon hours. Periods
of heavy rainfall may lead to urban and small stream flooding during
the afternoons. In addition, the persistent south to southeast low
level wind flow will also result in warmer temperatures along the
northern half of Puerto Rico during the next few days. Maximum
temperatures should range in the upper 80s to low 90s across the
coastal areas.

.LONG TERM...After mid week a surface high pressure ridge is
forecast build and spread north of the region by Wednesday. This
will generate easterly winds and a slight decrease on low
level moisture across the region through Friday. Once again
moisture associated to this trough will reach the local forecast
area increasing the chances of rain for the incoming weekend.


&&

.AVIATION...VFR conds durg entire prd. SCT ocnl BKN cld lyrs nr
FL020...FL035...FL100. Brief Mtn top obsc ovr ern PR til 15/14z due
to low CIG/-SHRA. Btw 15/17z-15/22z...SHRA/ isold TSRA psbl ovr ctrl
interior and nrn half of PR with VCTS psbl at TJMZ/TJBQ and TJSJ aft
15/18Z due to psbl streamer-like SHRA/ or isold TSRA. Wnds calm to
light and variable, becoming from the E-ESE at 10-15 kts except
slightly higher with sea breeze variations after 15/14z.


&&

.MARINE...although most of the swell energy generated by a low
over the NE Atlantic will move across the east of the Lesser
Antilles some long period swell could be reaching our local waters
on Tuesday afternoon. For today...seas will be between 3 to 5 feet
with a NE Swell and winds will be at around 15 knots or less.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 91 79 91 79 / 30 0 40 20
STT 86 79 87 79 / 20 30 40 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
341 PM AST Mon May 15 2017

.SYNOPSIS...Fair weather conditions will continue to prevail
during the morning hours with shower and thunder development
expected across northwest Puerto Rico each afternoon. Warm to
hot temperatures continue along the northern slopes under east
southeast winds. SAL continues tomorrow to result in hazy skies.

&&

.SHORT TERM...Tonight thru Wed...

The proximity of a developing trough to the west of the local
islands may enhance shower and thunder development Tue-Wed during
the afternoon hours. This enhancement is short-lived because as
the trough amplifies into the central Caribbean, a ridge pattern
aloft begins to strengthen across the area. As a result, locally
induced showers and thunderstorms are still expected across
northwest Puerto Rico during the afternoon hours Tue-Wed. Warm to
hot temperatures will continue to prevail across the northern
slopes of Puerto Rico as east southeast wind flow prevails across
the eastern Caribbean.

.LONG TERM...Thu thru Mon...

A mid to upper level ridge will hold across the forecast area
through at least early the upcoming weekend. This feature is
expected to erode through the weekend and into early next week.
As the ridge erodes, precipitable water is expected to increase
across the forecast area. At lower levels, a high across the
western Atlantic will hold through the forecast period to result
in moderate east southeast winds.

Therefore, expect a seasonable weather pattern with showers and
Tstorms each afternoon across the western interior and northwest
Puerto Rico. Elsewhere, mostly fair weather is expected with
limited shower activity. Warm to hot temperatures will continue
under an east southeast wind flow.

&&

.AVIATION...Mostly VFR conditions will prevail across the
local flying area for the next 24 hours. However, brief
SHRA/-TSRA still possible late this afternoon across west
and northwest PR impacting mainly TJMZ/TJBQ with only are
possible across TJSJ. Latest 12Z TJSJ sounding indicated
a southeast wind flow from the SFc to 10K feet, becoming
westerly and stronger aloft.

&&

.MARINE...Tranquil marine conditions will continue to prevail
across the local waters through midweek with seas 4 to 6 feet
and winds 15-20 knots. There is a moderate risk of rip currents
along the north facing beaches tonight, increasing to high by
Tuesday morning.

&&

.CLIMATE...TMAX at LMM airport reached 93F, this broke the
previous record set back in 2001. A Tmax of 93F also marks
the highest Tmax so far this year at LMM airport.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 79 91 79 90 / 20 20 20 20
STT 79 87 79 87 / 30 30 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
458 AM AST Tue May 16 2017

.SYNOPSIS...Recent satellite imagery suggests a fairly high concentration
of Saharan dust spread across the region today. Expect lesser amounts
of suspended dust particulates and a cleaner air mass Thursday and
during the rest of the work week. The mid to upper level ridge will
maintain its hold and aid in suppressing convective development across
the region. Surface high pressure ridge will continue to build and
spread across the west and central Atlantic while maintaining moderate
east southeast trade winds across the northeastern Caribbean.

&&

.SHORT TERM...Tuesday through Thursday...
Mid to upper ridge will continue to hold across the eastern/southeastern
Caribbean through Thursday. While at the same time an upper trough lingers
over the western/central Caribbean and across La Hispaniola. Surface
ridge will continue across the eastern/central Atlantic promoting
east to southeast trades and above normal temperatures across the coastal
areas of Puerto Rico. The heat index can range from the high 90s to
the low 100s across the northern coastal areas of Puerto Rico today.
A surface ridge is expected to enter the western Atlantic and build
north of the area by late Wednesday turning winds more from the east.
A weak front will linger/dissipate between the two highs while remaining
north of the area late in the forecast period.

Dry air at mid levels and Saharan dust will continue across the forecast
area at least through early Thursday creating hazy skies. This, in combination
with synoptic upper level pattern of trof across Hispaniola and ridge
over the eastern Caribbean basin will lead to diurnally induced convection
over portions of the northwest quadrant of mainland PR each afternoon.
Limited shower activity is expected across the rest of the island and
the USVI`s other than streamers with light rainfall amounts developing
downwind of the small islands.

.LONG TERM...Fri thru Tuesday...
The mid to upper level ridge will hold across the forecast area through Friday
but will erode over the upcoming weekend as a polar trough will move
across the west Atlantic and north of the region. As the ridge erodes,
low level moisture transport and precipitable water is forecast to slightly
increase once again across the forecast area. In the low levels, high
across the western and central Atlantic will be the dominant weather
feature and is expected to hold in place through the forecast period.
This will result in moderate east to southeast trade winds.

Therefore, expect a mostly seasonal weather pattern with periods
of passing late evening and early morning showers across the coastal
waters and windward side of the islands, followed by mainly locally
and diurnally induced afternoon convection mostly over parts of
the central interior and west sections of Puerto Rico. However,
model guidance does suggest occasional surges of moisture associated
with weak easterly perturbations moving across the region late Saturday
through Sunday and another Sunday through Monday. This should slightly
increase the chance for showers and possibly isolated afternoon thunderstorms
across the western interior and northwest Puerto Rico. Elsewhere,mostly
fair weather and sunny skies is expected with limited shower activity.
Near normal temperatures can also be expected during the long term
period which should be generally in the mid to high 80s in most
areas.

&&

.AVIATION...Mainly VFR conditions expected to prevail across all
terminals for the next 24 hours. HZ skies due to Saharan dust will
continue across the flying area, but visibility expected to remain
P6SM. Brief SHRA/-TSRA possible between 18z-22z near the vicinity of
TJBQ. Trade wind -shra can lead to sct/bkn cigs btw FL030-FL050
across the rest of the terminals. TIST/TISX are reporting false
bkn/ovc low CIGS. Winds below FL100 fm the ESE at 12-22 kts...bcmg
West and increasing with height. Sea breeze variations across W/NW
PR expected after 15z.

&&

.MARINE...Seas increasing up to 6 feet across the Atlantic waters,
offshore Caribbean waters and local passages today. Winds of 10 to
15 knots increasing to 15 to 20 knots by Wednesday.

&&

.CLIMATE...The dominant southeasterly trade winds will result in above
normal temperatures and moderate to high heat indices along portions
of the coastal areas of the islands, with high temperatures reaching
the low 90s in some areas today.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 92 78 90 78 / 20 10 20 10
STT 87 79 88 78 / 20 20 20 10

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
351 PM AST Tue May 16 2017

.SYNOPSIS...A fair weather pattern will continue to prevail across
the local islands through at least the upcoming weekend with some
shower and thunder development still possible across northwest
Puerto Rico each afternoon. Warm to hot temperatures are expected
along the northern slopes of Puerto Rico under east southeast winds.
Hazy skies will continue to prevail tomorrow due to SAL.

&&

.SHORT TERM...tonight thru Thu...

A fair weather pattern will continue to prevail across the local
islands during the forecast period under a mid to upper level
ridge and precipitable water near or below the normal range. At
lower levels, a building ridge across the western Atlantic will
continue to promote east southeast winds during the next few days.

As a result, continue to expect limited shower activity across
the forecast area with some shower/thunder development still
possible across northwest Puerto Rico each afternoon. Warm to
hot temperatures and hazy skies will continue under east
southeast winds and SAL respectively.

.LONG TERM...Fri thru Tue.../issued 458 AM AST Tue May 16 2017/

The mid to upper level ridge will hold across the forecast area
through Friday but will erode over the upcoming weekend as a
polar trough will move across the west Atlantic and north of the
region. As the ridge erodes, low level moisture transport and
precipitable water is forecast to slightly increase once again
across the forecast area. In the low levels, high across the
western and central Atlantic will be the dominant weather feature
and is expected to hold in place through the forecast period. This
will result in moderate east to southeast trade winds.

Therefore, expect a mostly seasonal weather pattern with periods
of passing late evening and early morning showers across the
coastal waters and windward side of the islands, followed by
mainly locally and diurnally induced afternoon convection mostly
over parts of the central interior and west sections of Puerto
Rico. However, model guidance does suggest occasional surges of
moisture associated with weak easterly perturbations moving across
the region late Saturday through Sunday and another Sunday
through Monday. This should slightly increase the chance for
showers and possibly isolated afternoon thunderstorms across the
western interior and northwest Puerto Rico. Elsewhere,mostly fair
weather and sunny skies is expected with limited shower activity.
Near normal temperatures can also be expected during the long term
period which should be generally in the mid to high 80s in most
areas.

&&

.AVIATION...Mainly VFR conditions expected to continue across the
local TAF sites for the next 24 hours. HZ skies due to Saharan dust
will continue across the local flying area, but visibility expected
to remain P6SM. Latest TJSJ 12Z sounding indicated a south southeast
wind wind up to 20 knots from the SFC to around 12k feet, becoming
westerly and stronger aloft.

&&

.MARINE...A long period northerly swell will continue to reach
the local waters through at least Wednesday with seas up to 6 feet
particularly across the Atlantic waters and passages. Winds will
continue east southeast at around 15 knots. There is a high risk
of rip current for the northwest to northeast beaches of Puerto
Rico and for Culebrita beach in Culebra.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 78 92 78 90 / 10 20 20 20
STT 79 86 78 88 / 20 20 20 20

&&

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
636 AM AST Wed May 17 2017

.SYNOPSIS...Suspended Saharan dust will linger across the region but
is expected to diminish by Thursday and Friday. Overall a fair
weather pattern is forecast for the next several days as a high
pressure ridge will build and spread across the region. Another
hot, hazy and overall dry air mass is expected today under the
prevailing southeast low level wind flow. Daytime high
temperatures in some areas will be slightly above normal again
today, but should, however, return to near normal on Thursday and
Friday as the wind become more easterly and gradually increases
across the region.

&&

.SHORT TERM...Today through Friday... A mid to upper level ridge
will continue to suppress convective activity across the islands
through Friday. Forecast soundings are indicating below normal
PWAT values for much of the forecast period. Fair weather
conditions are expected to prevail with limited diurnally induced
showers each afternoon across portions of western Puerto Rico.
Hazy skies due to Saharan dust will continue today. Above normal
temperatures are expected once again today across the coastal and
urban areas of the islands. Surface high pressure will continue to
build across the western Atlantic and north of the forecast area.
Moderate to locally fresh trade winds will continue through the
forecast period. Trade wind showers over the waters can briefly
affect portions of the USVI and eastern areas of PR. High cirrus
clouds will continue to stream over the local area as an upper
trough will linger over the northwestern Caribbean.

.LONG TERM... Late Friday thru Wednesday...The mid to upper level
ridge will erode slightly Friday through Saturday as a polar
trough will move across the west Atlantic and north of the region.
By Sunday and into the following week, high pressure will
reestablish once again across the Atlantic and remain the dominant
weather feature. In the low levels, a high across the western and
central Atlantic is expected hold in place through most of the
weekend but is forecast to shift farther eastward late Sunday and
Monday as a cold front will approach the eastern seaboard of the
United States. By then, the prevailing moderate easterlies will
become more southeasterly bringing hotter daytime temperatures and
elevated heat indices to portions of the islands once again.

All in all, a mostly seasonal weather pattern with limited
periods of passing late evening and early morning showers across
the coastal waters and windward side of the islands will prevail.
This will be followed by locally and diurnally induced afternoon
convection mainly over the interior and west sections of Puerto
Rico, with a few streamer-like showers possible in and around the
San Juan metro area. However, the prevailing easterlies will
still bring occasional patches of shallow low level moisture
associated with weak perturbations across the region, over the
weekend and into early next week. This added moisture should be
sufficient to support the development of local and diurnally
induced showers each day with only a slight chance of isolated
thunderstorms over western PR during the afternoons.
Elsewhere, mostly fair weather and sunny skies are expected with
limited shower activity. Near normal high temperatures are expected
Friday through Saturday, generally between the mid to high 80s,
but so far expect warmer/hotter days Sunday through Tuesday as
winds become more southeasterly.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across
all terminals for the next 24 hours. HZ due to Saharan dust will
continue across the flying area, but visibilities are expected to
remain P6SM. SHRA possible between 18z-22z near the vicinity of
TJBQ/TJMZ. Winds from the east at 10-15 knots with higher gusts
and sea breeze variations after 14z.

&&

.MARINE....A northerly swell will gradually subside across the
local Atlantic waters today through Thursday, with seas up to 6
feet today. Easterly trade winds will continue to increase to 15
to 20 knots across the local waters today and during the rest of
the week. This will create choppy sea conditions.

There is a high risk of rip currents for the northwest to
northeast beaches of Puerto Rico and for Culebrita beach in
Culebra. There is a moderate risk of rip currents for almost all
beaches in Vieques and the USVI. Please refer to the latest Surf
Zone Forecast (SRFSJU) issued by WFO San Juan Puerto Rico.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 88 77 / 20 10 10 20
STT 87 78 88 77 / 20 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
433 AM AST Thu May 18 2017

.SYNOPSIS...Lesser concentration of Saharan dust was observed across
the region, as the dust particulates continued to diminish. Overall
limited shower activity is expected for the next several days, as
a high pressure ridge will dominate the local weather pattern. A
predominantly dry and stable air mass with mostly sunny skies is
therefore expected to prevail. Increasing trade winds is forecast
today and into the weekend as the surface high pressure will continue
to tighten the local pressure gradient.

&&

.SHORT TERM...Today through Saturday...Ridge aloft will continue
across the eastern Caribbean basin. Saharan dust is expected to continue
over the forecast area today. These two features will result in a dry/fair
weather pattern across the islands. Shower activity will be limited
to brief trade wind showers across the USVI and sections of eastern
PR, followed by shallow afternoon convection over western PR. A trade
wind surge will create breezy conditions over the waters and coastal
areas of the islands. Max temps should reach the upper 80s to lower
90 degrees across the coastal and urban areas of the islands, dropping
to the mid-high 70s during the overnight hours.

.LONG TERM...Recent model guidance still suggests a slight erosion
of the mid to upper level ridge as a polar trough crosses the west
and central Atlantic. On Sunday, a high pressure ridge will enter
the southwest Atlantic and build eastward over the forecast area.
This will remain the dominant weather feature and consequently maintain
mostly fair and stable weather conditions across the region for most
of next week. The surface high pressure will be reinforced on Sunday,
as a cold front and associated weak trough dissipates across the central
Atlantic and north of the region. An easterly pertubations is forecast
to move across the eastern Caribbean late Sunday through Monday of
next week. By Tuesday, expect decreasing moisture transport and increasing
trade winds, with a gradual shift to southeast during the remainder
of next week. This is in response to the surface high shifting further
into the central Atlantic. Model guidance also suggests much warmer/hotter
daytime temperatures, especially along the northern half of Puerto Rico.
Another round of Saharan dust is forecast to arrive across the region
by early next week.

A quick surge of moisture accompanying a weak easterly perturbation
may bring additional low level moisture and showers to the region
late Sunday through Monday. This so far appears to be of short duration
with no major rainfall accumulations expected. No significant weather
feature is forecast to affect the region as mostly fair weather and
sunny skies is forecast at this time. Diurnally induced afternoon convection
should be focused mainly over parts of the central interior and interior
and west sections of Puerto Rico, with mostly streamer- like afternoon
convection over parts of the east sections including the San Juan metro
area. Expect limited shower activity elsewhere.

&&

.AVIATION...Mainly VFR conditions expected to prevail across all
terminals for the next 24 hours. HZ due to Saharan dust but vsby
P6SM. SHRA possible between 18z-22z near the vicinity of TJMZ.
Surface winds from the east at 10-15 knots with higher gusts in
the mid 20s after 14z.


&&

.MARINE...Small craft should exercise caution as the mainly wind
driven seas will be up to 6 feet across the local waters and winds
will be up to 20 Knots.

There is a high risk of rip currents across the northern coast of
Puerto Rico and Culebra, and moderate risk across most of the remaining
beaches in Puerto Rico, Vieques, and Culebra. For the USVI, there is
a moderate risk of rip currents across most of the beaches around the
islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 78 87 77 / 10 20 20 20
STT 89 78 87 78 / 10 20 20 10

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
350 PM AST Thu May 18 2017

.SYNOPSIS...A short wave trough is over the Bahama Islands through
Cuba and the western Caribbean will move east to and across the
local area on Saturday. In the mean time...A surface high pressure
ridge centered over the western North Atlantic will continue to
yield a mostly east wind flow across the northeast Caribbean.


&&

.SHORT TERM...Tonight through Saturday night...A few showers that
developed over western Puerto Rico earlier Thursday afternoon are
expected to dissipate by this evening as diurnal heating rapidly
diminishes. The morning sounding showed winds of 20 to 30 kt from
just above the surface up to around 11 kft and models suggest
that surface winds could increase overnight tonight diminishing
aft 19/08z. Higher elevations may experience a breezy night. On
Friday low level winds will still have a slight northerly
component that should cause best showers during the afternoon over
southwestern Puerto Rico. This should also result in slightly
lower temperatures, around 85 degrees as opposed to around 90, across
the northern portions of the islands. Temperatures could bounce
back up to around 90 again Saturday as surface winds shift again
to east-southeast as the Atlantic high pressure ridge shift
slightly eastward.

.LONG TERM...Sunday through Wednesday...Short wave trough
mentioned above will move east across the area and may induce an
increase in the shower activity Sunday. However...a mid/upper
level ridge will build rapidly across the eastern Caribbean
with strong subsidence and drier conditions dominating the area.
A rather strong episode of Saharan dust is expected to arrive
across the eastern Caribbean by early next week. The combination
of strong subsidence, drier conditions and the arrival of the
Saharan dust will likely result in higher afternoon temperatures
possibly reaching the lower to mid 90s...especially along northern
sections of Puerto Rico.


&&

.AVIATION...Incrg sfc winds of 10 to 20 kt and gusts up to 28 kt
will slowly diminish as winds bcm more Ely. -SHRA still forming off
of El Yunque til arnd 18/21Z. Ltd SHRA in NW PR with VCSH TJMZ/TJBQ
till 18/21Z. Saharan dust has limited some vsbys to 7-10 SM but is
also causing some CIG sensor errors. Isold mtn obscurations til
18/22Z. VFR all TAF sites through 20/08Z, except pds MVFR for CIGs
psbl at TNCM/TKPK.


&&

.MARINE...A wind surge is expected to move across the local
islands tonight resulting in surface winds ranging in the 15 to 20
kts. This in turn will result in seas momentarily building to
around 6 feet across the Atlantic and Caribbean offshore waters.
However both winds and seas are expected to subside by Friday with
conditions remaining below caution criteria the rest of the
forecast period.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 77 85 78 89 / 10 10 20 20
STT 78 88 78 88 / 10 10 10 10

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
451 AM AST Fri May 19 2017

.SYNOPSIS...A mid to upper trough will move across the Atlantic
and into the northeastern Caribbean through the weekend. Upper
ridge builds from the west through much of next week. Weak surface
trough will linger northeast of the area during the weekend. A
broad surface high pressure building across the western Atlantic
will move into the central Atlantic by mid week next week. This
will result in southeasterly winds. A Saharan air layer will move
early next week across the forecast area.


&&

.SHORT TERM...Friday through Sunday...Variably cloudy skies
prevailed across the local islands overnight and early this
morning with limited shower activity noted over the north coast of
Puerto Rico. Overnight temperatures were in the high 70s to low
80s across the lower elevations to the low 70s across the higher
elevations. Winds were from the east at around 10 mph.

A mid to upper level trough will continue to meander northeast of
the forecast area today through early the upcoming weekend, inducing
a surface trough across the northeast Caribbean Sat-Sun. This
surface trough is expected to promote moisture advection across the
eastern Caribbean during the weekend. However, precipitable water
values will continue in the normal range. As the trough aloft moves
away while weakening Sunday and early next week, the surface trough
will dissipate and a ridge pattern aloft is expected to establish.
Therefore, under a slight increase in convective instability and
available moisture, expect afternoon showers and thunderstorms
developing over west Puerto Rico Sat-Sun with limited shower
activity expected elsewhere. Meanwhile for today, continue to expect
a fair weather pattern with limited shower activity across the
forecast area.

.LONG TERM...Monday through Friday...Mostly fair weather
conditions are expected across the islands. As SAL and ridge
pattern aloft erodes the available moisture. Therefore, limited
shower activity and hazy skies are expected once again. As the
surface ridge moves into the central Atlantic winds will turn more
from the southeast and warmer temperatures are expected. Shower
development will be confined to the western/northwest portions of
Puerto Rico during the afternoon hours. Across the U.S. Virgin
Islands and the eastern sections of Puerto Rico, light trade wind
showers could move from time to time, but overall a drying trend
is forecast through the end of next week.


&&

.AVIATION....Mostly VFR conditions are expected to prevail at all
terminals through the forecast period. SHRA still possible between
18z-22z in and around TJMZ with brief MVFR conds possible. Easterly
winds around 10-15 knots with higher gusts and sea breeze
variations after 14z.


&&

.MARINE...Small crafts should continue to exercise caution today
through much of the regional waters due to seas up to 6 feet and
winds up to 20 knots. Seas and winds are expected to subside
during the weekend. There is a moderate risk of rip currents for
much of the north, east and south facing beaches of the islands.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 79 89 78 / 30 30 20 20
STT 88 79 87 78 / 30 30 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
415 AM AST Sat May 20 2017

.SYNOPSIS...Locally induced showers and thunderstorms are expected
across the western interior and west Puerto Rico each afternoon
through the weekend. A fair and stable weather is expected to
prevail much of next week with warm to hot temperatures and hazy
skies.

&&

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

A slightly increase in moisture is expected across the region
during the weekend. Mid to upper level cloudiness will continue
to stream across the region in the prevailing westerly upper
flow. A surface trough just to the northeast of the region will
produce an increase in low level moisture across the region today.
This will induce the development of short lived showers and a
couple of thunderstorms across western and interior sections of
Puerto Rico this afternoon. However, precipitable water values
will continue in the normal range. An upper level trough axis will
drift eastward across the northeast Caribbean tonight and Sunday,
bringing a more favorable upper level dynamics increasing the
moisture advection across the local islands on Sunday. This will
favor better afternoon convection and the possibility of
thunderstorms Sunday afternoon. By Sunday night and Monday the
trough axis will be to the east of the region, diminishing the
overall moisture across the local islands.

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

A mid to upper level ridge is expected to build across the
forecast area Wed-Thu and hold through Saturday with some
weakening anticipated on Sunday. This will promote moisture
erosion across the eastern Caribbean during the forecast period
with precipitable water values remaining below the normal range.
At lower levels, a broad high pressure will dominate the central
Atlantic, resulting in east southeast winds across the forecast
area. SAL is also expected to reach the eastern Caribbean early
next week.

Therefore, under the influence of east southeast winds and a dry
and stable air mass with dust particles, a fair weather pattern is
expected with warm to hot temperatures and hazy skies much of
the next week.

&&

.AVIATION...Mostly VFR conditions expected across the local flying
area for the next 24 hours. Some SHRA expected to develop over
western PR between 18Z-22Z producing brief periods of MVFR over
TJMZ. Latest TJSJ sounding indicated an east to east northeast
wind flow up to 20 knots from the SFC to 6kft.

&&

.MARINE...Tranquil marine conditions are expected to prevail
across the local waters during the next few days with seas up
to 5 feet and winds 10-15 knots. There is a moderate risk of
rip currents across the north facing beaches of Puerto Rico and
Culebra.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 80 90 80 / 20 20 20 20
STT 90 80 89 80 / 20 30 30 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
430 AM AST Sun May 21 2017

.SYNOPSIS...Locally induced showers and thunderstorms are expected
across central and west Puerto Rico this afternoon. A weak tropical
wave will continue to move south of the area while an induced
trough remains to the northeast of the local islands. A fair and
stable weather is expected to prevail much of the next workweek
with warm to hot temperatures and hazy skies.

&&

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

Doppler radar indicated isolated shower activity across northern
and eastern sections of Puerto Rico as well as across the
surrounding waters overnight and early this morning. The surface
trough northeast of the region will continue to drift northeastward
while weakening away from the region today. An upper level trough
will also move to the east of the region today. However, the
lingering moisture will combine with daytime heating, sea breeze
convergence and mountain effects to induce another round of
showers and thunderstorms mostly across western, interior and
northwest Puerto Rico this afternoon. Later surface analysis
depicted a weak easterly wave over the eastern Caribbean this
morning. The northern edge of this wave will aid to enhance the
showers activity across the region today. Not significant
precipitation is expected across the U.S. Virgin Islands. GFS
guidance indicated PWAT values at around 1.80 inches today,
decreasing rapidly below 1.50 inches Monday an Tuesday as the
easterly wave moves away and a relatively dry and hazy air mass
encompass the region from the east. Residual moisture still
expected to produce some convection over western Puerto Rico on
Monday.

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

A mid to upper level ridge will hold across the area through the
forecast period with some weakening expected Sunday and into early
next week. The ridge pattern aloft will promote limited moisture
with precipitable water values remaining below the normal range.
At lower levels, a broad high pressure will dominate the central
Atlantic, resulting in east southeast winds across the eastern
Caribbean Wed-Fri. Latest guidance continues to indicate the
Saharan Air Layer across the eastern Caribbean much of the
workweek.

Therefore, under the influence of east southeast winds and a dry
and stable air mass with dust particles, a fair weather pattern
is expected with warm to hot temperatures and hazy skies much of
the workweek. As the ridge aloft erodes Sunday and into the next
week, an increase in low level moisture is expected with a better
chance for showers and thunderstorms.

&&

.AVIATION...Mostly VFR conditions expected across the local
flying area. VCSH/VCTS is possible across TJMZ and TJBQ after
21/17Z as . afternoon convection develops over western and
northwest PR. Winds will increase at 10-15 knots after 21/13Z
with sea breeze variations. Latest TJSJ sounding indicated an
easterly wind up to 15 knots from the SFC to 12K feet, becoming
westerly and stronger aloft.

&&

.MARINE...Tranquil marine conditions are expected to prevail
across the local waters through early this week with seas up
to 5 feet and winds 10-15 knots. There is a moderate risk of
rip currents across the north facing beaches of Puerto Rico.
Seas will build up to 7 feet by midweek.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 90 78 / 30 20 30 10
STT 90 79 88 80 / 20 30 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
409 PM AST Sun May 21 2017

.SYNOPSIS...Showers and thunderstorms are once again occurring
this afternoon across central and western PR due to local effects
and available moisture. Weak tropical wave is expected to move to
the south of the local islands tonight while the induced trough
continues northeast through tonight before it weakens and
dissipated by Monday and a SFC high develops north of the local
islands. Haze due to Saharan Dust and warm temps are expected
through this week.

&&

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

The band of moisture as seen over the area in the MIMIC product is
thinning as it hold over Saint Thomas and southwest between Vieques
and Saint Croix. Although streamers with very light precipitation
(so far) have developed off of these islands little other effect has
been seen. Due to weaker moisture in the area showers are not as
widespread or intense as they were yesterday at 2 PM AST, but are
still developing. The GFS suggests that columnar moisture will peak
around 22/06Z and then drop below levels seen anytime in the last 48
hours, so showers may linger into the evening as well.

As what remains of an eastward moving ridge at upper levels passes
over Puerto Rico Monday night, convergence aloft will begin to help
suppress vertical motion. Northwest flow will have already begun and
This will greatly decrease the amount of shower coverage Monday
afternoon. It may not be enough to completely suppress
thunderstorms, however, as the model anticipates higher CAPE levels
than today or yesterday. This will be reversed on Tuesday when
divergence aloft will increase with the passage of a weak upper
level short wave and moisture temporarily increases Tuesday and
Wednesday. Nevertheless equivalent potential temperature values will
decrease considerably after tonight and remain low till at least
Tuesday afternoon in the presence of Saharan dust that will also
increase considerably between 22/15Z and 23/15Z. This will lead to
hazier skies and weakly developing clouds during the week.

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

A mid to upper level ridge will hold across the area through the
forecast period with some weakening expected Sunday and into early
next week. The ridge pattern aloft will promote limited moisture
with precipitable water values remaining below the normal range.
At lower levels, a broad high pressure will dominate the central
Atlantic, resulting in east southeast winds across the eastern
Caribbean Wed-Fri. Latest guidance continues to indicate the
Saharan Air Layer across the eastern Caribbean much of the
workweek, however, it looks particularly dense early in the week.

Therefore, under the influence of east southeast winds and a dry
and stable air mass with dust particles, a fair weather pattern
is expected with warm to hot temperatures and hazy skies much of
the workweek. As the ridge aloft erodes Sunday and into the next
week, an increase in low level moisture is expected with a better
chance for showers and thunderstorms. One more thing to note, the
latest guidance is indicating that the 100-850mb thickness is
expected to drop late this week, which could cause a few degrees
cooler minimum temperatures during the overnight hours if the
skies are clear and the wind is light.

&&

.AVIATION...VFR conds have prevailed across the local area and are
expected to continue except for TJMZ which has already seen some
SHRA/TSRA development and may have CIGS nr BKN030 til 21/21Z. Some
mtn obscurations over hir terrain expected til 21/04Z. Sfc winds
easterly with sea/land breeze variations 5 to 15 kt. Maximum winds
50 to 70 knots from FL390-470 by 22/18Z strongest at FL470.

&&

.MARINE...Seas are expected to continue 2-4 feet through Monday,
then increase gradually on Tuesday and Wednesday with potential of
up to 7 feet by Wednesday. There is a moderate risk of rip
currents for northern Puerto Rico and Culebra today and Monday,
low risk elsewhere.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 79 90 78 91 / 30 30 20 20
STT 79 88 80 89 / 30 20 20 20