Caribbean - Central America Weather

[cycloneye]

AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
550 AM AST Sat Apr 20 2019

.SYNOPSIS...High pressure at the surface will maintain moderate to
fresh trade wind flow across the area through Monday. A surface
low will develop northeast of the area that will turn winds more
northeasterly and bring the remnants of a cold front across the
area on Monday, followed by unstable conditions Tuesday and
Wednesday. Moisture will also increase late next week.

&&

.SHORT TERM...Today through Monday...
A surface high pressure located northeast of Bermuda and an
associated ridge extending southwestward over the western Atlantic
will continue to promote a moderate to fresh easterly flow across
the region through Sunday. Under this flow, patches of low-level
moisture will move across the forecast area, enhancing cloud cover
and shower activity. Overnight and early morning showers are
expected to stream across the waters into windward areas of the
islands, while afternoon convection is to favor the interior and
western sectors of Puerto Rico supported by diurnal heating and
local effects. Streamer-like showers are possible over the San
Juan metro area and eastern Puerto Rico downstream from El Yunque
and the local islands, respectively. Significant rainfall
accumulations are not expected due to dry conditions and
divergence aloft.

In the meantime, a mid-level short-wave trough, steered by a polar
trough moving over the western Atlantic, is to move over the
northeast Caribbean on Sunday until it weakens and gets absorbed by
a deep low migrating to the south-southwest over the central
Atlantic on Monday. The latter is forecast to reach a distance of
nearly 1200 miles northeast of Puerto Rico by midday Monday while
promoting a northeast flow across the region. This combination will
result in the weakening of the trade wind inversion and enhance mid-
level moisture transport while supporting deeper convective
instability on Sunday and Monday. Although the distribution of
showers will be of a seasonal structure, favorable conditions aloft
will result in enhanced shower coverage and intensity with moderate
to locally heavy rainfall. The forecast calls for the most intense
activity on Monday with an estimated PW of 1.57 inches, favoring
eastern Puerto Rico and the U.S. Virgin Islands in the morning and
portions of the interior and southwestern Puerto Rico in the
afternoon.

.LONG TERM...Tuesday through Saturday
The upper level low will be closest to the local area Monday night
into Tuesday being 1200 miles east northeast of San Juan. An upper
level jet will wind through the trough over central Cuba and pass
just north of Puerto Rico and the U.S. Virgin Islands and continue
south of the upper level low with winds in the local area ranging
from 75 knots over Puerto Rico to around 100 knots just north of
the local forecast area. The passage of the upper level trough to
the north and the approach of the mid level trough Tuesday and
Wednesday will bring 500 mb temperatures close to minus 11 degrees
C late Tuesday night and around minus 9 degrees on Tuesday.
Therefore have added the possibility of thunderstorms in southwest
Puerto Rico along and around the Cordillera Central on Tuesday
afternoon, since sufficient moisture should still be present to
generate convection that could break through 20 to 25 kft. On
Wednesday 500 mb temperatures warm slightly and moisture is
weaker. Although the forecast does not have afternoon
thunderstorms at this time, will check runs 24 hours hence to see
if conditions persist. The upper level trough will be past by
Thursday and total precipitable water will reach a minimum on
Thursday morning. Moisture begins to rise again Thursday through
Friday, as a patch of low-level moisture moves west through the
area, but dry mid layers and an atmosphere that is just barely
unstable will counteract most convection. Nevertheless, showers
will increase then.

A tropical wave will move through the tropical Atlantic mostly
below 10 north Tuesday and Wednesday, sending a plume of moisture
northeast behind it. It will enter the Caribbean well south of
the area, but that plume will move across Puerto Rico and the U.S.
Virgin Islands Saturday and Sunday and reinforce some of the low
level moisture that arrived the days before. Thus the period will
end with some of the best moisture of the entire week, but still
not completely up to what is usually seen by the end of April.

&&

.AVIATION...Mainly VFR conds will prevail across the local
terminals during the fcst pd. SHRA development is expected in the
vicinity of Mayaguez between 19/18z-23z, possibly affecting
TJMZ/TJBQ and resulting in brief MVFR conds and mtn obscurations.
Winds will be from the east at 5-15 knots, increasing after
20/13Z to 15-20 knots with gusts up to 30 knots and sea breeze
variations.

&&

.MARINE...Due to winds of 15 to 20 knots and locally higher around
Puerto Rico, seas begin to approach 7 feet today through Sunday
night. Therefore, have issued small craft advisories for seas up
to 7 feet. Seas are expected to slightly exceed 7 feet at the
outer buoy by Sunday night and some of this will also impinge on
the northeast corner of our forecast area then. Small craft
advisory conditions are not foreseen beyond this through 7 days.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 85 75 / 30 40 40 70
STT 87 75 86 73 / 20 20 20 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
543 AM AST Sun Apr 21 2019

.SYNOPSIS...A weak cold front riding in on northeast flow
generated by high pressure north of the area and a developing low
in the mid central Atlantic will bring better showers on Monday
followed by another period of drying. Long term models suggest a
moisture plume from a tropical wave passing well south of the area
may bring more showers next Sunday. Winds will begin to diminish
Monday and be rather quiet by Wednesday.

&&

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

A surface high pressure spreading across the west and central
Atlantic will continue to promote a moderate to fresh and briefly
strong easterly flow across the region today. Under this flow, a
patches of low-level moisture will continue to move across the
forecast area today, enhancing cloud cover and shower activity.
Overnight and early morning showers will continue to stream across
the local waters into portions of eastern Puerto Rico and the
U.S. Virgin Islands. Given the intensity of the flow, some of
these showers may move further inland over portions of the
interior. This will be followed by afternoon convection clustering
over the interior and western sectors of Puerto Rico supported by
diurnal heating and local effects. Streamer-like showers are
possible over the San Juan metro area and eastern Puerto Rico
downstream from El Yunque and the local islands, respectively.
Model estimated PW values between 1.35-1.44 inches around
21/12-18Z could support significant shower activity with the most
intense showers in the afternoon.

A weak mid-level trough will continue to drift over the northeastern
Caribbean until it weakens by Monday. In the meantime, a surface
induced trough will continue to migrate south to southwest over the
central Atlantic and linger to the northeast of the region later
today through early next week, promoting a northeast wind flow
across the region. This combination will result in the weakening
of the trade wind inversion and enhance mid-level moisture
transport while supporting deeper convective instability. Although
the showers will favor a seasonal distribution, favorable
conditions aloft will result in enhanced shower coverage and
intensity with moderate to locally heavy rainfall. The forecast
continues to call for the most intense activity on Monday
afternoon. Precipitable water values are estimated to be 1.53
inches. Showers will be scattered to numerous showers and will
favor eastern Puerto Rico and the U.S. Virgin Islands in the
morning, and portions of the interior and southwestern Puerto
Rico in the afternoon. Considerable drying will occur on Tuesday
and shower activity will diminish.

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

After drying on Tuesday behind the cold front, moisture will
return from the northwest at 700 mb on Wednesday. Flow becomes
very light on Wednesday so that most showers will be induced by
local effects of sea breeze convergence and inland heating. The
surface low to our northeast will fade Wednesday and Thursday and
withdraw on Saturday, to be replaced by a weak high just north of
the forecast area. This will bring another period of drier
conditions. At the surface, high pressure will build south into
the tropical Atlantic Saturday night and Sunday, and a weak low
will move from the Gulf of Mexico on Saturday to north of the
local area on Sunday, producing moderate southeasterly flow.

We continue to follow a tropical wave between 30 and 40 west--
mostly south of 10 north. It is forecast to move into the eastern
Caribbean on Thursday and join with moisture streaming into the
southern Caribbean from the southwest. As high pressure at 700 mb
moves into the eastern Caribbean on Saturday, these combined plumes
of moisture will be swept into Puerto Rico and the U.S. Virgin
Islands on Sunday, while the wave continues through the central
Caribbean. Currently, the GFS has been favoring this development
and has been forecasting precipitable water values of 1.8 to 2.0
inches in several of the last runs, if only for a brief period of
24-36 hours. This would bring another round of showers to the area
if the axis of the high continues to be south of Puerto Rico.

&&

.AVIATION...Mainly VFR conditions expected. However, SHRA will
result in briefly MVFR conditions at TSJU between 21/08-10Z and VCSH
conditions across E-PR/USVI and Leeward Islands terminals through
21/14Z. Afternoon convection will bring VCSH in the vicinity of San
Juan and Mayaguez between 21/16-22Z. Winds will continue from the
E at 10-15 knots with higher gusts across E-PR/USVI and Leeward
Islands terminals through 21/13Z, but light and variable
elsewhere. Winds will increase at 15-20 knots with higher gusts
after 21/13Z.

&&

.MARINE...A weak swell of almost 3 feet from the northeast and
winds of 15 to 20 knots are combining to bring seas of 5 to 7 feet
to the north central and northeastern local outer Atlantic waters.
After Monday, sea conditions will improve, and after Wednesday
some of the quietest seas in several months will be seen for a few
days. Seas south of Puerto Rico and the U.S. Virgin Islands may be
as low as 1 to 3 feet Thursday and Friday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 85 73 / 40 70 70 40
STT 86 76 86 74 / 40 70 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
516 AM AST Mon Apr 22 2019

.SYNOPSIS...A cold front will move through the area from the
northeast today. Drier conditions will follow until Friday. Then,
moisture will begin to increase from the southeast and the south
such that by Sunday or Monday showers and thunderstorms will
become likely over the area.

&&

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

A strong surface high pressure and associated ridge spreading across
the west and central Atlantic will continue to lift northwards while
slowly pushing a surface low pressure system south-southwestward
across the central Atlantic to about 1000 nautical miles northeast
of the forecast area late tonight into Tuesday. In the meantime,
a weak surface high will move off the east coast of the United
States into the western Atlantic and just north of the Bahamas.
This combination will promote an east to northeast low-level wind
flow across the region, but gradually diminishing, as the local
pressure gradient relaxes through the short-term forecast period.
At mid-levels, ridging aloft will continue to erode as a short-
wave trough moves over the region. This will result in the
weakening of the trade wind cap and enhance low- to mid-level
moisture transport while supporting deeper convective instability.

Under this flow, the remnants of a frontal boundary will continue to
sink southwestward and cross the region today. This will result in
showers streaming over the waters into portions of eastern and
northern Puerto Rico, as well as across the U.S. Virgin Islands
during the morning hours. Given favorable conditions aloft and the
expected high moisture content with estimated PW values peaking
around 1.5 inches, areas of afternoon convection with periods of
moderate to locally heavy rainfall are expected. This activity is
expected to cluster over the interior and southwestern quadrant of
the island supported by the northeast flow. Total rainfall
accumulations of up to two inches with isolated higher amounts
are expected with a moderate threat of urban and small stream
flooding across these areas. For the U.S. Virgin Islands, although
streamer- like showers may develop in the afternoon, significant
rainfall accumulations are not expected over land.

Conditions are expected to somewhat improve on Tuesday, but another
wave of low-level moisture will enhance cloud coverage and shower
activity across the regional waters and coastal areas during the
overnight and morning hours. The combination of lingering moisture,
favorable upper level conditions, a weak low-level flow, diurnal
heating and local effects will favor a round of localized and
prolonged deep afternoon convection. A drier and weather pattern
with patchy moisture is expected to return late Tuesday into
Wednesday.

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

At upper levels, both the trough just north and over the local
area and the core of the southwesterly 90-knot jet over the local
Atlantic waters on Wednesday will be moving east of the area on
Thursday and west to west northwest flow will commence. On Friday
and Saturday, another jet core north of the area will pass through
and over a very weak ridge moving through the area. Some weak
divergence will be seen. Then on Sunday, a deeper trough over Cuba
will approach the area and arrive in Hispaniola by Tuesday.
During this time weak short waves will pass through the west
southwest flow with bands of divergence aloft.

A similar situation will occur at mid-levels, where the trough
that passed through the area on Wednesday will continue eastward.
Thursday and Friday, however will see another weak trough move
through the area. A ridge will move through Saturday and Saturday
night. Then a trough will deepen over Cuba, but hang back over the
windward passage during the remainder of the period.

At lower levels, the tropical wave we have been tracking south of
12 north, will be entering the eastern Caribbean on Thursday with
the ridge in the western tropical Atlantic waters following at
around 15 degrees north. This will pick up moisture from the
convection and throw it northeast behind the wave and as far north
as 19 degrees north. Southerly flow that develops in the southern
Caribbean over Venezuela will bring up considerable moisture
beginning Wednesday and this flow will continue Thursday. The
tropical wave will then join the southerly flow in the area with
its moisture. By Saturday, some of this moisture will enter the
southern part of the forecast area. On Sunday the best part of this
plume, now stretched east to west over Puerto Rico and the U.S.
Virgin Islands, will cross through the area bringing showers.
Although the moisture at mid-levels leave the area to the
northeast, a plume of moisture will form in the southeast flow and
keep the area relatively moist through Tuesday. 500 mb
temperatures begin to drop Sunday and continue to drop through the
following Wednesday which will make the sounding unstable. By
Monday this will mean that thunderstorms will be possible, though
they will have to fight through the drier air aloft.

It appears that overall moisture will be least on Thursday and
that only scattered showers over the southwest part of the
Cordillera Central should be expected with few showers elsewhere.
Then on Friday moisture will stream over the Caribbean to our
south and slowly spread north into the area on Saturday with
scattered showers over eastern Puerto Rico in the morning and
western Puerto Rico in the afternoon. As moisture increases
Saturday and Sunday, so also will the area and coverage of
showers. By Sunday, thunderstorms cannot be ruled out but
continued low level moisture and mid level cooling on Monday and
Tuesday will keep showers and some thunderstorms over the area.

&&

.AVIATION...Mainly VFR conditions expected. However, SHRA will
result in briefly MVFR conditions at TKPK/TNCM through 22/10Z and
VCSH conditions at TJSJ/TJBQ through 22/14Z. Afternoon convection
will bring VCSH to TJMZ/TJBQ/TJPS between 22/16-23Z. Winds will
be light and variable through 22/13Z, turning from the east and
increase between 10-20 knots with higher gusts and sea breeze
variations after 22/13Z.

&&

.MARINE...Seas are subsiding after reaching almost 9 feet at the
outer buoy (41043) and almost 6 feet at the inner buoy (41053)
late Sunday night. Seas fell to just below 7 feet at the outer
buoy in the last several hours and are expected to subside a foot
or so more today and tonight. This will end the threat of small
craft advisory conditions for the rest of the week. However
another set of swell from the vigorous low to our northeast will
enter the area Tuesday afternoon from the northeast with 4 to 5
foot heights so that by Tuesday night the high risk of rip
currents, (which will come down tonight on the north coast of
Puerto Rico) will be high again Tuesday night. The swell event
will begin to fade on Thursday and Friday. This will bring
relatively quiet seas with seas falling below 4 feet everywhere.
These conditions are expected to persist through next weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 73 86 75 / 70 40 40 40
STT 84 74 87 75 / 40 40 40 40

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
425 AM AST Tue Apr 23 2019

.SYNOPSIS...Patches of moisture, associated to the remnants of an
old frontal boundary, will continue to move across the area
today. Although low moisture content is expected on Wednesday
through Saturday, a patchy weather pattern will enhance locally
induced convection across the islands. By Sunday into early next
week, an increase in moisture transport and favorable upper level
conditions will lead to deeper and organized convection with the
likelihood of isolated thunderstorms across the area.


&&

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

Weak troughiness at the mid- and upper-levels has developed near
Hispanola this morning and is expected to continue to move
eastward over the next several days. During the overnight, a
drier air mass moved across the region resulting in limited
shower development. However, low-level moisture embedded in the
easterly trades is slowly eroding the drier air away. The easterly
trade winds will continue to periodically usher in patches of
low-level through the short- term period.

Model guidance continues to show an increase in upper-level
instability through Wednesday. The upper-level instability is a
result of a strong subtropical jet aloft, which will enhance
divergence over the forecast area. Additionally, 500 mb
temperatures today through Wednesday are expected to be near -8 to
-10 Celsius during the afternoon hours. The combination of the
subtropical jet, diurnal heating and local and diurnal effects
will increase the likely-hood for isolated thunderstorms across
the interior, and western areas of Puerto Rico today and
Wednesday. Due to the factors above isolated thunderstorms were
put into the afternoon forecast for today and Wednesday.

In addition, surface winds will range from 5 to 10 kts today. These
relatively light winds could cause showers and isolated
thunderstorms that do develop to move slowly. This could lead to
urban and small stream flooding and ponding of water on roadways.

Thursday, the subtropical jet is forecast to move away from the area
and decrease the upper-level instability. Furthermore, a drier air
mass will once again move into the region from the north. This will
limit shower development during the afternoon. However, can`t rule
out some showers developing due to local and diurnal effects.


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

A light to moderate easterly wind flow will hold across the region as
a surface high pressure moves eastward over the western Atlantic
on Friday. Although a mass of relatively drier air will dominate
the local weather conditions on both days, showers are expected to
move over portions of eastern Puerto Rico and the U.S. Virgin
Islands during the overnight and morning hours. As the day
progresses, afternoon convection supported by diurnal heating and
local effects is expected to develop over the interior and western
sectors of Puerto Rico. Ridging aloft will prevent deep and
organized convection to develop, limiting rainfall accumulations
over land.

By Saturday, winds are expected to gradually turn from the
southeast while increasing as the aforementioned high and
associated ridge spreads northeastward across the western and
central Atlantic. This flow will aid in advecting deeper tropical
moisture, associated to a tropical wave, into the region by
Sunday, which will hold over the forecast area through at least
Wednesday. Favorable upper level dynamics resulting from an
amplifying trough combined with better moisture content will
enhance the development of deeper and organized convection over
the area. Adding to this, an increase in mid-level moisture
content and temperatures around -8C with divergence aloft will
support the likelihood for isolated thunderstorms across the
region, particularly on Sunday and Monday.


&&

.AVIATION...VRF conds will continue to prevail across all
terminal sites through 23/15Z. Then SHRA are expected to develop
across terminals TJSJ, TJPS, TJBQ AND TJMZ. ISO-TSRA could develop
by 23/18Z mainly across terminals TJBQ, TJMZ and the interior
areas of Puerto Rico. Sfc winds will be out of the east to
northeast at 5 to 10 kts. Winds turn to the north at 07 to 014 kft
with winds ranging from 2 to 14 kts. SHRA and winds will begin to
diminish across the local terminals by 24/01Z.


&&

.MARINE...A gentle east to east-northeast wind flow will hold
across the region through at least Wednesday, becoming moderate to
fresh by the end of the workweek into the weekend. A northeasterly
swell will arrive and spread across the local waters today and on
Wednesday, generating choppy/rough seas up to 6 feet. As a
result, small craft operators are urged to exercise caution
across most of the local waters. By Wednesday evening, marine
conditions are expected to improve and hold through the upcoming
weekend.

A moderate risk of rip currents is in effect for beaches along
the northwest to northeast coast of Puerto Rico, as well as
beaches along the north coast of Culebra, Saint Thomas and Saint
Croix. The risk will elevate to high by this evening for most of
these beaches. This conditions will hold through late Wednesday
night, improving thereafter.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 74 86 74 / 40 30 40 20
STT 85 73 85 73 / 40 30 30 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
429 AM AST Wed Apr 24 2019

.SYNOPSIS...Although low levels of moisture content are expected
today, patches of low-level moisture and favorable upper level
conditions may enhance shower development over the forecast area.
A drier and stable weather pattern is expected on Thursday through
the weekend, but an increase in moisture transport and favorable
upper level conditions by early next week will support a wetter
weather pattern with deeper and organized convection, as well as a
likelihood for isolated thunderstorms.


&&

.SHORT TERM...Today through Friday...

Showers lingered over the Caribbean waters this morning as a result
of surface convergence and limited low-level moisture. Additionally,
0-3km steering flow of less than 5 kts has caused showers to drift
slowly across the Caribbean waters. Across land light showers moved
across the eastern, interior, and southeastern portions of Puerto
Rico. However, as a result of limited moisture in the lower levels
of the atmosphere rainfall amounts have been relatively light.

Later today a weak mid to upper-level trough will continue to
progress to the east and move closer to Puerto Rico. This will put
Puerto Rico near the right entrance region of the jet this
afternoon. The right entrance region is where upward motion occurs,
which supports divergence aloft. The upper-level instability
provided by the sub tropical jet would typical be conducive for
thunderstorm development across Puerto Rico most afternoons. This is
support by the 500 mb temperatures that shows values ranging from
-8 to -9 degrees Celsius today. However, a limiting factor that has
inhibited thunderstorm development is the lack of low-level
moisture. A drier air mass has been pulled down from the north
Atlantic into the region over the last several days. This has
limited low-level moisture, and thus inhibited thunderstorm
development. However, thunderstorm development is possible this
afternoon.

Additionally, showers that do develop will move slowly as a result
of light low-level steering flow. Currently, the skew-T and TJUA VAD
wind profile shows surface and mid-level winds ranging from 5 to 8
kts today. These light winds at the surface and mid-levels of the
atmosphere will cause storms to move slowly this afternoon. This
could lead to urban and small stream flooding, and ponding of water
on roadways this afternoon.

Thursday, the sub tropical jets moves east of Puerto Rico thus
diminishing the upper-level instability over the region. Although,
the instability and low-level moisture will abate showers will
develop as a result of local and diurnal effects. Late Thursday into
early Friday model guidance shows moisture lifting north out of deep
tropics. This moisture is expected to continue to pull north into
the local waters and across U.S. Virgin Islands and southern
portions of Puerto Rico on Friday. This added moisture will increase
rain chances across the region on Friday.

.LONG TERM...Saturday through Thursday...

A combination of surface high pressure systems will promote a
general easterly wind flow across the region throughout the long-
term forecast period. However, winds are to briefly turn from the
east-southeast on Saturday and from the east-northeast on Tuesday
as a surface high moves farther from the region into the central
Atlantic and another surface high moves into the western Atlantic
and builds north of the region, respectively. The latter will
cause winds to increase from moderate to fresh late Monday night
through the end of the forecast period.

Although a mass of relatively drier air will hold over the region
on Saturday and Sunday, patches of low-level moisture will enhance
cloud coverage and shower activity across eastern Puerto Rico and
the U.S. Virgin Islands in the morning, and over the interior and
western Puerto Rico in the afternoon. By Monday and continuing
through at least Thursday, the combination of increased moisture
content (PW values of 1.5 to 2.0 inches) in response to a passing
tropical wave and favorable dynamics aloft due to an amplifying
mid- to upper- level trough spreading across the southwestern
Atlantic will support the development of deeper and organized
convection across the region. Given that models call for relatively
high moisture content and temperatures ranging between -8C and -11C
at mid-levels under divergence pattern aloft supports the likelihood
for isolated thunderstorms across the region, particularly on
Monday through Thursday. Significant rainfall accumulations up to
2 inches and isolated higher amounts are expected across the
islands with this activity, particularly the interior and western
portions of Puerto Rico. Important to emphasize that there is
medium confidence in this forecast as it is expected 5 days from
now, even though model solutions have supported this wet pattern
during the last few days.


&&

.AVIATION...VRF conds are expected to continue to prevail across
all terminals through 24/15Z. Then SHRA will developed across
terminals TJSJ, TJBQ, and TJMZ. Additionally, iso TSRA are
possible this afternoon across terminals TJBQ and TJMZ. Sfc winds
will be out of the east to northeast at 5 to 10 kts.


&&

.MARINE...A gentle east to northeast wind flow will hold across
the region today, but veering to the east and becoming moderate
to fresh on Thursday and continuing through the weekend. A
northeasterly swell will continue to spread across the local
waters today, generating choppy/rough seas up to 6 feet. As a
result, small craft operators are urged to exercise caution across
most of the local waters. Marine conditions are expected to
gradually improve this evening and hold through the upcoming
weekend.

A high rip current risk is in place for beaches along the north
coast of Puerto Rico and Saint Croix, while a moderate risk of rip
currents will continue for the surrounding beaches. Al though coastal
conditions are to improve this evening, the high risk will hold
through Thursday.


&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
437 AM AST Thu Apr 25 2019

.SYNOPSIS...A light to moderate easterly wind flow will hold
today. Winds are to gradually turn from the east-southeast on
Friday through Saturday, but increasing and turning to the east-
northeast by Tuesday through the end of the forecast period.
Although low moisture content is expected through Friday, diurnal
heating and local effects will support the development of locally
induced showers. Moisture is expected to somewhat increase during
the weekend, but a surge in moisture transport will support the
development of deeper and organized convection along with a
likelihood for isolated thunderstorms next week.


&&

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

The base of the trough will continue to move east of Puerto Rico
through Friday, but weak troughiness in the mid to upper-levels
will remain north of the island. Although, weak troughiness will
hold through Friday, a relatively stable weather pattern is
expected to prevail across the region.

The relatively fair weather across the area is a result of limited
low-level moisture combined with the lack of low and upper-level
forcing. However, showers are possible across interior and southern
areas of Puerto Rico today through Saturday. Shower development
during the short-term period will be due to local and diurnal
effects. Also, light low-level winds will cause showers to move
slowly over land areas. Additionally, the relatively air mass will
cause rainfall accumulations to be light to locally moderate.

Saturday, shallow moisture returns to the region this will help aid
in shower development during the afternoon mainly of portions of the
interior and western areas of Puerto Rico. A mid to upper-level
ridge builds across the area early Saturday morning. As the ridge
holds over the area winds will be out of the east to southeast,
which will cause warmer daytime temperatures.

.LONG TERM...Saturday through Thursday...

A moderate to fresh east to east-southeast wind flow will hold
across the forecast area on Sunday and Monday as a surface high
continues to move farther away and spreads across the north
central Atlantic. By Tuesday and continuing through at least
Thursday, winds are to turn from the east-northeast as a broad
surface high moves across the western Atlantic and builds north of
the region. The latter will cause winds to increase and become
fresh to strong as it tightens the local pressure gradient through
the end of the forecast period.

Current guidance suggests that moisture, associated to an
easterly wave, will infiltrate the region on Sunday into Monday.
Then, as the winds gradually turn from the east-northeast,
another surge of moisture is expected as the remnants of a
frontal boundary sink southward over the forecast area. This
combination will result in increased moisture content with
estimated PW values ranging between 1.5 to 2.0 inches and a higher
chance for shower activity with moderate to heavy rainfalls
across the forecast area. Adding to this, an amplifying mid- to
upper-level spreading southeastward over the western Atlantic into
the northeastern Caribbean will result in the weakening of the
trade wind cap while generating a divergence pattern aloft. This
will support the development of deeper and organized convection,
as well as the likelihood for isolated thunderstorms on Monday
through Thursday supported by model estimated mid-level
temperatures ranging between -8C and -10C. Significant rainfall
accumulations up to 2 inches and isolated higher amounts can be
expected with this activity, particularly across the interior and
western portions of Puerto Rico. Even though recent model
solutions have agreed in a wetter pattern by next week, there is
medium confidence in this forecast.


&&

.AVIATION...VRF conds will continue to prevail across all
terminal sites through 25/15Z. Then iso/sct SHRA will develop over
the interior, and western areas of Puerto Rico, before
diminishing by 26/02Z. Sfc light/variable through 25/12Z, then
winds will be out the east ranging from 5 to 15 kts.


&&

.MARINE...Tranquil marine conditions with seas up to 5 feet and
east winds up to 15 knots are expected to prevail today through at
least early next week. There is a moderate risk of rip currents
for beaches along the north coast of Puerto Rico, Culebra and
Saint Croix. Elsewhere, a low risk will continue during the next
few days.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 74 85 75 / 10 20 10 20
STT 80 74 79 75 / 10 20 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
411 AM AST Fri Apr 26 2019

.SYNOPSIS...
A drier air mass will limit shower activity over the next several
days. However, moisture is expected to gradually increase this
weekend. The moisture increase should aid in shower development
mainly during the afternoon. Early next week a mid to upper-level
trough will deepen, and enhance instability over much of the
region. Additionally, the subtropical jet will also enhance
instability as a result of its winds of 70 to 90 kts. The
instability combined with low-level moisture should support deep
convection across portions of western and interior areas of Puerto
Rico. Then early Wednesday the mid and upper-level trough cuts
off from the main flow, and keep unsettled conditions over much of
the area through Friday.

&&

.SHORT TERM...Today through Sunday....
A mid- to upper-level ridge will build from the east and will hold
through at least Sunday. A surface high pressure will continue to
promote an easterly wind flow across the islands. Stable and fair
weather conditions will prevail today. However, limited low-level
moisture combined with diurnal heating and local effects will aid in
shower development across the central and western interior sections
during the afternoon. The strongest activity could produce ponding
of water in roads and poorly drained areas across western PR.

Saturday, shallow moisture returns to the region from the southeast.
This moisture will promote passing showers across the local waters,
the U.S. Virgin Islands and east-PR after midnight into Saturday
morning. Shower activity will increase during the afternoon mainly
across central and western PR. In addition, low level convergence
will bring shower activity across the U.S. Virgin Islands and E-PR
at time. The southern slopes will observe warmer daytime
temperatures.

A similar weather pattern will continue on Sunday. Therefore, shower
development will be due to low-level convergence during the
overnight and morning hours, and due to local and diurnal effects
during the afternoon.

&&

.LONG TERM...
Monday a mid and upper-level trough is forecast to deepen near
Cuba and enhance upper-level instability over the region. Also,
strong upper-level winds of 70 to 90 kts associated with the
subtropical jet will surge just north of Puerto Rico through
Tuesday. The aformentioned features will support upper-level
divergence across Puerto and the U.S. Virgin Islands. In addition,
a weak tropical wave will remain well south of Puerto Rico,
however, the wave will bring deep tropical moisture into the
forecast area late Sunday into Monday. Precipitable water values
on Monday will range from 1.6 to 2.0 inches climatological these
values are close to the 99th percentile for the month of April.

The mid to upper level moisture will erode away the drier air
that has held in the mid and upper-levels of the atmosphere. This
is depicted by the SJU-GFS skew-T and GFS relative humidity images.
The 500 mb temperatures on Monday show values ranging from -9 to -10
degrees Celsius, which would support deep organized covection.The
abundant low-level moisture, adequate upper-level instability, and
upper-level forcing are ingredients needed for deep organized
convection and thunderstorms.

However, GFS Galvez-Davison Index (thermodynamic index) for
tropical convection shows values ranging from 15 to 25. These
values support the potential for a few isolated thunderstorms,
but most of the showers will be shallow convection. Tuesday the
mid and upper-level troughs begin to cut off from the main flow
this will keep troughiness and instability around through the rest
of the workweek. This will increase the likely-hood for afternoon
showers across most of the island. This forecast is depends on
the position of the mid to upper-level trough, and the available
low-level moisture. Therefore, any deviation in track or position
of the aforementioned features could change the long-term
forecast. For this reason the confidence of the long-term forecast
is medium.

&&

.AVIATION...
VRF conds will continue across the local flying areas through at
least 26/15Z. Then, SHRA/+SHRA will develop over the interior, and
northwest sections of Puerto Rico. Afternoon showers should
dissipate around 26/00z. Winds will continue calm to light and
variable, becoming from the E to ESE at 10 to 15 knots with higher
gusts and sea breeze variations.

&&

.MARINE...
Tranquil marine conditions will continue today through the
weekend. Seas will range from 3 to 5 feet, and winds will be
easterly at 5 to 15 kts. A low to moderate rip currents risk will
continue through Sunday. The moderate risk of rip currents are for
the north facing beaches of Puerto Rico.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 76 88 77 / 10 40 30 30
STT 86 76 86 76 / 20 40 40 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
431 AM AST Sat Apr 27 2019

.SYNOPSIS...
Low-level moisture will gradually increase each day this weekend
before peaking on Monday. The increase in shallow moisture will
aid in the development of showers across Puerto Rico during the
afternoon. Light to moderate rainfall is expected to develop
across portions of interior and western areas of Puerto Rico each
day through Monday. Then on tuesday a drier air mass will move
over the area and obstruct afternoon convection. The remainder of
the workweek into the weekend will be unsettled as low-level
moisture, and instability increases across the region. The
increasing instability is due to the mid to upper-level trough and
the low-level jet that is forecast to move near Puerto Rico.
Therefore, expect an increase in afternoon convection with the
possibility for isolated thunderstorms.

&&

.SHORT TERM...Today through Monday....
A ridge pattern aloft inhibited shower activity across the islands
overnight. Tranquil weather conditions will continue into the
morning hours. Precipitable water is expected to increase around 1.5
inches by mid morning. This airmass will bring isolated to scattered
clouds and showers across the U.S. Virgin Islands and E-PR. This
airmass interacting with local effects and diurnal heating will
produce the strongest activity across the interior and western
sections of Puerto Rico during the afternoon hours. However, The
U.S. Virgin Islands and E-PR, including the SJ-metro area, can
expect periods of showers during the afternoon. Afternoon activity
could lead to urban and small stream flooding mainly across central
and western Puerto Rico.

Moisture will continue to increase from the east through at least
Monday. The mid- to upper-level ridge will hold over the islands
through Sunday night. Therefore, a similar pattern will persist on
Sunday, with overnight and morning showers across the USVI/E-PR
followed by afternoon convection across the central and western
interior sections.

The aforementioned ridge pattern is expected to erode by Sunday
night as a mid- to upper-level trough moves from the west into the
northeast Caribbean. This will increase the chance for thunderstorm
development across interior and western portions of PR during the
afternoon hours.

&&

.LONG TERM...Tuesday through Saturday...

Slight changes were made to the long-term forecast as a result of
settle changes in moisture and synoptic features. Tuesday morning
a drier air mass is forecast to filter in and erode away the low
and mid-level moisture. Recent guidance shows precipitable water
values ranging from 1.0 to 1.2 inches on Tuesday. Additionally,
the drier air mass will obstruct the development of deep convection
during the afternoon. However, local and diurnal effects, and the
proximity of the cut-off mid to upper-level low will provide
enough instability for the development of shallow convection.
Wednesday moisture is forecast to slowly filter into the
Caribbean, and peak at the end of the week. Precipitable water
values at this time will be near 1.5 to 1.8 inches, climatological
these values are close to the 75th percentile for the month of
April. The low-level moisture will aid in the development of
showers during the afternoon. Also, 500 mb temperatures through
the long-term period show values ranging from -8 to -10 degrees
celsius, which would support deep organized covection.The
abundant low-level moisture, adequate upper-level instability, and
upper-level forcing are ingredients needed for deep organized
convection and isolated thunderstorms.

Wednesday GFS Galvez-Davison Index (thermodynamic index)
for tropical convection shows values ranging from 25 to 35. These
values support the the potential for scattered thunderstorms or
scattered shallow convection with isolated thunderstorms. This is
supported by the GFS which shows a modest low-level jet to the
north of Puerto Rico. The low-level jet and proximity of the mid
and upper-level trough will enhance upper-level divergence, and
increase instability aloft. Unsettled weather conditions are
expected Thursday through Saturday, with showers and possible
isolated thunderstorms developing during the afternoon mainly
across the interior and western areas of Puerto Rico.

This forecast is depends on the position of the mid to upper-level
trough, and the available low-level moisture. Therefore, any
deviation in track or position of the aforementioned features
could change the long- term forecast. For this reason the
confidence of the long-term forecast is medium.

&&

.AVIATION...
VRF conds will continue across the local flying areas through at
least 27/15Z. Then, occasional SHRA/+SHRA will move over
TIST/TISX/TJSJ by mid morning spreading into the interior and
western PR by the afternoon. SHRA/+SHRA and mount obsc is expected
along the Cordillera Central btwn 27/16-23z. SHRA will likely impact
TJMZ/TJBQ. Winds will continue calm to light and variable, becoming
from the E at 10 to 15 knots with higher gusts and sea breezes.

&&

.MARINE...
Seas will range from 3 to 4 feet through Sunday, then seas will
reach 5 feet. Winds will be out of the east to southeast at 5 to
15 kts with high gusts possible. A moderate risk of rip currents
for the north facing beaches of Puerto Rico today.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 77 85 75 / 30 30 40 50
STT 86 76 86 76 / 40 30 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
428 AM AST Sun Apr 28 2019

.SYNOPSIS...
Moisture will increase over the region today through Tuesday.
Therefore, expect an increase in showers during the afternoon
across most of the area. A drier air mass is forecast to move
into the region either late Tuesday or early Wednesday. The drier
air mass will inhibit deep convection from forming however
isolated showers are possible during the afternoon. Late Wednesday
night low-level moisture gradually increases over the area and
will remain through the remainder of the workweek. The
increase in instability provided by the cut-off low and
increasing low-level moisture will cause unsettled weather through
early Saturday.

&&

.SHORT TERM...SUNDAY THROUGH TUESDAY...
The weak ridge pattern suppressed shower activity across the islands
overnight and will limit it through the morning hours. The ridge
will continue to erodes as a trough moves closer to the islands. As
a result, instability is forecast to increase which combined with
the available moisture, diurnal heating and local effects will
produce afternoon convection mainly across the interior and western
sections of Puerto Rico. In addition, the west end of the U.S.
Virgin Islands and E-PR, including the SJ-metro area, can expect
periods of showers during the afternoon. Thunderstorm development is
possible along and to the west of the Cordillera Central during the
afternoon hours. These sections could expect urban and small stream
flooding this afternoon.

Instability and plenty of tropical moisture will persist through at
least Monday. Therefore, the potential for shower and thunderstorm
development will remain high through at least Monday. For Tuesday,
although favorable upper level dynamic will continues, a dry airmass
is forecast to filter from the east. This could limit shower
formation on Tuesday.

&&

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

A short wave trough will amplify across the west Atlantic then
become cut-off from the main flow on Wednesday. The cut-off low is
forecast to linger near Hispaniola and cuba through Saturday.
Current model guidance has upper-level instability increasing as a
result of the upper-level low. In addition, modest upper-level
winds of 50 to 70 kts as a result of the sub-tropical jet. The
low-level jet and proximity of the mid and upper-level trough will
enhance upper-level divergence, and increase instability aloft
over the area through the end of the workweek.

Also, the SJU- GFS shows 500mb temperatures ranging from negative
8 to 10 through the long-term period. The abundant low-level
moisture, adequate upper-level instability, and upper-level
forcing are ingredients needed for deep organized convection and
isolated thunderstorms across portions of western and interior
areas of Puerto Rico. Rainfall amounts Thursday through Friday
could range from 0.50 to 1.00 inches across the western and
interiors areas of Puerto Rico. Elsewhere, isolated to scattered
convection will form across other areas of the island during the
day. Therefore, expect unsettled weather conditions through
Friday. Then early saturday a mid to upper-level ridge will build
across the region and bring a end to the unsettled weather through
Sunday.


&&

.AVIATION...
VFR conds expected across the local terminals through the morning
hours. MTN obsc is expected across the higher elevations of PR btwn
28/16-23Z. SHRA/TSRA development is expected across the interior and
west-PR. This activity can produce VCSH/VCTS across TJSJ/TJPS/TJMZ
and TJBQ. The USVI terminals should not ruled out VCSH btwn 28/15-
20z. Calm to light and variable winds will continue 28/13Z, then are
expected to return from the east at 10 to 15 kt with higher gusts
and sea breeze variations.

&&

.MARINE...
A gentle to moderate easterly wind flow will continue across the
local and outer waters today. Then winds are forecast to increase
to moderate to fresh over portions of the Atlantic and Caribbean
waters. Seas will range from 3 to 5 feet today then seas will
become choppy early next week as winds increase over the waters.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 86 76 / 40 50 50 20
STT 86 76 87 76 / 40 40 30 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
534 AM AST Mon Apr 29 2019

.SYNOPSIS...
A short wave trough will continue to amplify aloft. A subtropical
jet will swing by the northeast Caribbean providing good
ventilation and instability across the region today. Low-level
moisture will continue moving across the local islands today. As a
result, another rainy day will be likely today. Upper level
instability should persist through mid week.

&&

.SHORT TERM...today through Wednesday...

Mid to upper level trough over Hispaniola will continue to
provide good upper level divergence over Puerto Rico today. A
moist east to southeast low level wind flow will continue and
showers and thunderstorms are expected to develop once again over
the interior and western sections of Puerto Rico. Additional
convective activity is expected across the eastern interior and
showers could affect once again the eastern sections of the island
this afternoon. Urban and small stream flooding is expected with
the heaviest showers.

For Tuesday and Wednesday, although favorable upper level dynamics will
persist a dry airmass in the low to mid levels is forecast to filter in
from the east. This should limit widespread shower activity across the
islands. However, isolated to scattered afternoon showers with possible
isolated thunderstorms are possible over the interior and western
sections of Puerto Rico. Across the U.S. Virgin Islands, streamers are
expected to develop and showers could briefly affect portions of the
islands. A drying trend is expected on Tuesday and Wednesday and fair
weather conditions should prevail.

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

A short wave trough with a subtropical jet will linger across the
northeast Caribbean through Friday. Unsettle weather conditions
can be expected Thursday and Friday.

A cut-off low moving across the Florida Peninsula will move
westward near the region promoting another subtropical jet over
the region. However, a ridge pattern is forecast to build aloft
between late Friday and Sunday. Under this weather pattern,
locally induced showers will develop each afternoon mainly across
the interior and western sections of the islands. While, the
windward sections can expect passing showers during the overnight
and early morning hours. This feature will be followed by another
short-wave trough early next week.

&&

.AVIATION...Mainly VFR conditions are expected to prevail through
the forecast period. However, SHRA/TSRA is expected to develop over
the interior and western PR. This could cause tempo MVFR conditions at
TJMZ/TJBQ btw 16z-22z. Iso TSRA could develop south of TJSJ. Low level
winds will continue from the ESE winds at 10-15 kt with sea breeze
variations and higher gusts aft 14z.


&&

.MARINE...
Mariners can expect choppy seas as the easterly trade winds
increase across the local waters. Showers and thunderstorms may
develop across the coastal waters of the Atlantic and in the Mona
passage during the afternoon and evening hours. Small craft
operators should exercise caution across most of the local waters.
Seas will reach 7 feet from early Tuesday morning through late
Tuesday evening in the southern portion of the Mona Channel and
the outer Caribbean waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 74 88 75 / 50 20 20 20
STT 87 76 86 76 / 10 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
501 AM AST Tue Apr 30 2019

.SYNOPSIS...
A mid to upper level trough will linger over the region through at
least Thursday. A drier air mass will move into the area from the
east today. Therefore, mostly sunny skies will prevailed through the
morning hours, followed by locally induced showers and isolated
thunderstorms across portions of the interior and western Puerto
Rico. Another patch of moisture will arrive Tuesday night until
Thursday morning, bringing a better chance of showers to the area. A
mid-level ridge will build from the west by Friday into the weekend,
limiting shower development in the area.

&&

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

A mid to upper level trough will linger over Hispaniola during the
next few days and this could provide divergence aloft to support
isolated thunderstorm development during the afternoon hours over
the interior and western sections of Puerto Rico, but mainly on
Wednesday afternoon. For today, a drier air mass will move over the
region from the east and the precipitable water content is forecast
to drop between 1.20-1.40 inches across the islands. However,
daytime heating in combination with the sea breeze convergence and
the proximity of the trough should lead to the development of
showers with possible isolated thunderstorms over western PR.

On Wednesday, a surge of low level moisture from the east in
combination with the amplifying upper level trough should result in
better chances of rain and thunderstorm development across the
forecast area. Urban and small stream flooding can be expected with
the heaviest showers on Wednesday. By Thursday, another area of
drier air is forecast to fill in from the east between 12z-22z. This
will promote fair weather conditions across the U.S. Virgin Islands
but diurnally induced afternoon showers are expected to develop over
western PR.

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

A ridge pattern aloft will build from the east over the northeast
Caribbean by the end of the work-week into early next week. A
migratory surface high pressure will tighten the local pressure
gradient promoting an easterly wind flow through at least Sunday.
As the high pressure enters the eastern Atlantic Ocean the surface
winds are forecast to shift from the east-southeast. Under this
weather pattern, locally induced showers will develop each
afternoon mainly across the interior and western sections of the
islands. While, the windward sections can expect trade wind
showers during the overnight and early morning hours. Under a
east-southeast wind flow, maximum temperatures could reach low 90s
along the northern coastal areas by the upcoming week.

&&

.AVIATION...
Mainly VFR conditions are expected to prevail through the
forecast period. However, SHRA/TSRA is expected to develop over
western PR btw 16z-22z. This could cause tempo MVFR conditions at
TJMZ/TJBQ. Low level winds will continue from the ESE winds around
15 kt with sea breeze variations and higher gusts aft 14z.

&&

.MARINE...
Choppy seas are expected as the easterly trade winds increase
across the local waters and passages. Therefore, small craft
operators should exercise caution across most of the local waters.
A Small Craft Advisory is in effect across the southern portions
of the Mona Passage and the outer Caribbean waters due to seas
around 7 feet. In addition, showers and thunderstorms may develop
over portions of the coastal waters of western Puerto Rico and in
the Mona passage during the afternoon and evening hours.

Beachgoers there is a high risk of rip currents across the eastern
beaches of St Croix. The risk of rip currents will be moderate
across most of the local beaches, except across St John and
west PR.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 76 86 76 / 20 30 60 40
STT 87 77 86 75 / 20 40 50 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
532 AM AST Wed May 1 2019

.SYNOPSIS...A mid to upper level trough over the Bahamas is
forecast to move further northwest and dissipate by Friday. A
surge of low level moisture from the east will increase shower and
thunderstorm development across the forecast area today. Drier air
and fair weather conditions return during the second half of the
week.


&&

.SHORT TERM...TODAY THROUGH FRIDAY...

A mid to upper level trough will continue to provide divergence
aloft and instability until early Thursday. A patch of moisture
will move in from the east today, bringing a better chance for
convective development across the area. Surface convergence and
orographic lifting will aid in shower development across the U.S.
Virgin Islands and eastern Puerto Rico through the morning hours.
Then, this surge of moisture in combination with local effects and
the proximity of the trough should result in showers and
thunderstorms activity, mainly across the interior and western
Puerto Rico. The USVI and E-PR, including the San Juan metro area
and southeast PR, may observe isolated thunderstorms during the
afternoon hours as well. Urban and small stream flooding is likely
with any persistent heavy rainfall today.

A drier air mass should reach the region on Thursday. However,
shower activity is still possible across the interior and western
Puerto Rico and downwind of the islands. In addition, an upper level
ridge will begin to build east of the region by Thursday night,
further promoting a fair weather pattern across the forecast area.

A migratory surface high pressure, located off to the north across
the Atlantic Ocean, will tighten the local pressure gradient
increasing local winds from this afternoon into the end of the
workweek.

.LONG TERM...SATURDAY THROUGH WEDNESDAY...

Trade wind cap and drier air aloft should promote fair weather
conditions through the long term period. A weak upper level jet
will move briefly on Sunday to enhance afternoon convection over
the interior and western sections of Puerto Rico. Otherwise, trade
wind showers will move at times across the USVI and the eastern
sections of PR, leaving minor rainfall accumulations during the
overnight/early morning hours. This will be followed by diurnally
induced afternoon showers over west/northwest PR each day.


&&

.AVIATION...SHRA will affect the terminals of E-PR/USVI and the
Leeward Islands through the morning hours. SCT-BKN ceilings between
FL022-FL070 can be expected at times. SHRA/TSRA will spread into the
interior/W-PR btwn 01/16-23z. This could result in brief periods of
MVFR conds or even IFR at TJMZ/TJBQ/TJSJ. Sfc winds will continue
from the E - ENE at 10 kt or less, increasing btwn 15-20 kt with
higher gusts and sea breeze variations after 01/13z.


&&

.MARINE...Breezy trades will maintain choppy seas across the
offshore waters and across the local passages through the end of
the work week. Seas up to 6 feet and east winds up to 20 knots are
expected to prevail. Therefore, small crafts should exercise
caution. There is a high risk of rip currents across the eastern
beaches of St. Croix through Friday afternoon. Across the rest of
the islands, a moderate risk of rip currents will continue for
the next several days.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 76 86 76 / 40 50 50 30
STT 87 77 86 75 / 50 50 50 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
548 AM AST Thu May 2 2019

.SYNOPSIS...Upper level trough will continue to support showers
and thunderstorms this afternoon across mainland Puerto Rico.
Drier mid level air is expected to fill on Friday and Saturday.
Upper level jet and surge in low level moisture will increase
showers again on Sunday. An induced surface trough will bring
showers once again on Tuesday.


&&

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

Since showers have ended over Saint Croix, the flood warning for the
area will be cancelled. Some deep ponding may still persist during
the morning hours as waters are slow to drain.

A weak pocket low at upper levels will pass north of Puerto Rico and
dissipate on Friday leaving moderately strong westerly flow in
place. High pressure will build south and over the area Friday and
Saturday, ridging from the south.

At mid levels, an area of cold 500 mb temperatures associated with
the upper level high, will move east, north of the area, and
dissipate. 500 mb temperatures will rise from minus 9 today to minus
6 on Saturday and instability will gradually decrease.

At lower levels high pressure in the western Atlantic will slowly
drift southeast arriving to a position 800 miles north northeast of
Puerto Rico by Saturday afternoon. This will continue to drive
moderate to fresh trade winds across the area.

The colder air at mid levels will allow showers and thunderstorms to
develop in the moderately rich moisture of the lower levels. Local
urban and small stream flooding will be possible in western and
interior Puerto Rico today. The moisture will diminish-
-mainly above 850 mb--and the risk of showers and thunderstorms will
decrease somewhat Friday and Saturday. Instability will also
decrease Friday and Saturday as the mid levels warm. Nevertheless
showers should be expected each afternoon in western and interior
Puerto Rico, and showers will likely cross into eastern Puerto Rico
during the overnight and early morning hours.

Showers will gradually diminish around the U.S. Virgin Islands this
morning and only light showers are expected Friday and Saturday.

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

A 50-60 kt W-SW upper level jet and a surge in low level moisture
will increase the potential for thunderstorm development on Sunday
afternoon over portions of the interior and western PR. Moisture
drops on Monday but diurnally induced afternoon showers are
expected to develop mainly over western PR and off the USVI in
form of streamers. A surface low and associated cold front is
forecast to move off the mid-Atlantic coast of the U.S. on Monday
and move into the central Atlantic by mid week. By Tuesday, an
induced surface trough is expected to increase the potential for
scattered to numerous showers and possible thunderstorm activity
across PR.

A mid level ridge is forecast to build and hold across the
western Atlantic through mid week, while an upper level trough
over the far central Atlantic extends into the northeastern
Caribbean. At the surface, a northeasterly wind flow will prevail
across the forecast area, as a surface high pressure builds over
the southwestern Atlantic. This will result in passing showers
across the northeastern sections of PR and across the USVI during
the second half of the week during the overnight and early morning
hours, followed by diurnally induced afternoon showers over the
interior and west/southwest sections of PR.


&&

.AVIATION...MVFR conds will cont over NE central PR in
SHRA/isold +SHRA til 02/14Z with mtn obscurations. +SHRA/+TSRA to
redevelop ovr wrn PR aft 02/16Z with IFR/MVFR and mtn obscurations.
Brief MVFR may be encountered at TJMZ/TJBQ. Aft 02/14Z easterly sfc
winds incr to 10-20 kt with gusts to 28 kt psbl alg N and S coasts
of PR. Maximum winds WSW 65-75 kt btwn FL400-480.


&&

.MARINE...Breezy trades will keep choppy seas across the offshore
waters and passages for the next few days. Mariners can expect
seas up to 6 feet and east winds up to 20 knots in general. Small
crafts should therefore exercise caution across most of the
regional waters. Moderate risk of rip currents will prevail across
most of the north, east and southern beaches of PR. A high rip
current risk continues in effect through this afternoon across the
eastern tip of St. Croix.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 77 87 75 / 50 40 40 50
STT 86 76 87 76 / 50 20 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
511 AM AST Sat May 4 2019

.SYNOPSIS...Brisk trade winds will continue today and Sunday, but
winds diminish during the early part of next week. A weak short
wave aloft will bring enhanced convection to the area on Sunday.
Drier conditions will return on Monday and Tuesday. Conditions
gradually become more moist Tuesday through Saturday.

&&

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

An upper level ridge will build over Puerto Rico
this morning is generating more stable conditions across the
local forecast region. Enough moisture will be available to
interact with local effects and develop scattered to numerous
showers. These showers will develop mainly across the western
interior sections of Puerto Rico. Most of these showers will
dissipate around sunset.

On Sunday, increasing moisture with a slightly more unstable
conditions will increase the shower coverage. Expect showers moving
onshore and affecting the eastern portions of Puerto Rico during
the morning hours and later on across the interior and western
portions of PR. Local urban and small stream flooding in isolated
thunderstorms will be possible in western Puerto Rico. Although
moisture will decrease on Monday, and mid levels will be dry and
somewhat stable, showers are still expected in eastern Puerto Rico
during the overnight and early morning hours and over western
Puerto Rico during the afternoon.

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

A strong ridge will re-build over the area on Tuesday from
northern South America. The axis is expected remain just west of
the local area through the period. After Thursday this ridge will
begin to flatten, allowing the jet north of the area to approach
the area later in the period. Upper levels will contribute little
to the dynamics during the week, but beginning Friday areas of
divergence aloft will enhance any activity over the weekend.

Mid levels are dry until Thursday, when southerly flow will bring
up tropical moisture from easterly waves passing well south of the
area. With enhanced precipitable water values, shower activity
will increase. 500 mb temperatures will be considerably warmer
until Friday. By Sunday of next week, values as low as minus 8.5
degrees C could be seen. This would allow thunderstorms to form
again in western Puerto Rico.

Lower level flow turns southeasterly beginning Tuesday and will
carry considerable moisture into the area by Thursday. The best
moisture is expected on Friday and Saturday. Sunday and Monday
will have some drying.

The moist periods Friday through Sunday of next week will bring a
few more showers to the U.S. Virgin Islands, but generally only
light amounts are expected Tuesday through Thursday.

&&

.AVIATION...VFR conds to prevail except aft 04/17Z ovr wrn and
interior PR. Aft 04/17Z SHRA to dvlp ovr wrn and central PR with
mtn obscurations and areas of MVFR/IFR. Brief MVFR to affect
TJMZ/TJBQ till arnd 04/22Z. Sfc winds 10 kt or less in easterly flow
with land breezes to bcm aft 04/14Z 10-20 kt with gusts to 30kt psbl
from the east with sea breeze influences. Maximum winds W 50-60
knots btwn FL360-490.

&&

.MARINE...Marine conditions will continue choppy through Tuesday
with some improvement on Wednesday. Small craft advisories are not
expected for the next 7 days.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 76 87 76 / 30 50 40 50
STT 87 76 85 76 / 20 10 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
456 AM AST Sun May 5 2019

.SYNOPSIS...High pressure in the central Atlantic will maintain
easterly trade winds that will carry areas of moisture across
Puerto Rico and the U.S. Virgin Islands. For now, the best
moisture is expected Thursday and next weekend. Mid and upper
levels become more favorable for showers and thunderstorms then.


&&

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

Today the ridges move to the east of the area as a weak short-
wave trough develops to the north of Puerto Rico. In addition, a
weak jet will be north or slightly over the area today. The weak
jet and short-wave trough will increase upper-level instability
over Puerto Rico today. Also, low-level moisture is expected to
increase across the area. The aformentioned factors will increase
the rain chances and the possibility for isolated thunderstorms
mainly over portions of interior and western areas of Puerto Rico
during the afternoon.

Monday and Tuesday the sub-tropical jet is forecast to move east of
Puerto Rico making the mid to upper level atmosphere more stable,
decreasing the chances for thunderstorm development. Although low-
level moisture will decreases across the region between Monday and
Tuesday enough moisture will be available to generate isolated to
scattered showers mainly across the interior and western portions of
Puerto Rico each afternoon.

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

A broad ridge at upper levels will remain over the area through
Sunday. There will be some influence from a moderate jet that
remains north of the area during the period. Upper level
divergence will coincide with better overall moisture Saturday and
Sunday to bring an increase in showers and thunderstorms.

At mid levels high pressure dominates the Caribbean. A minor
weakness in the ridge develops west of the area late in the
period. Mid levels remain dry until Thursday. Mid level moisture
in moderate amounts then continues into next week.

Areas of moisture in the lower levels are carried through by the
persistent easterly trade winds. Better moisture at 700 mb is
seen developing late Wednesday and Thursday. A plume of moisture
is lifted off a tropical wave passing well south of the area and
crosses through the area Friday and Saturday. It is on Saturday
afternoon that the best moisture is to be seen. This will also be
the time when 500 mb temperatures reach minus 9 degrees. Numerous
showers and some thunderstorms are expected late this week and
possibly into Sunday of next week. Otherwise the period will see
overnight and morning showers on the eastern slopes of Puerto Rico
followed by afternoon showers in western Puerto Rico.

&&

.AVIATION...VFR conds will prevail today for most the terminals.
Easterly winds will return at 15-20 kt with higher gusts and sea
breeze variations after 05/13z. SHRA will develop ovr wrn and jbq
central PR with mtn obscurations and MVFR psbl TJMZ/TJBQ til
around 05/23z. Sfc winds will become calm to light and variable
after 05/23z. Maximum winds W 50-60 kts btwn FL340-480.

&&

.MARINE...Winds and sea will peak later this evening. Although
seas are expected to remain below 7 feet, small craft will need
to exercise caution. Winds and seas may briefly exceed 20 knots
and 7 feet within 15 nautical miles of Puerto Rico`s north coast--
especially in showers. Otherwise, small craft advisories are not
expected through Sunday of next week.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 89 75 / 50 50 50 40
STT 85 77 86 77 / 40 40 40 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
532 AM AST Mon May 6 2019

.SYNOPSIS...After a brief surge of moisture today conditions will
be relatively tranquil through Wednesday with typical scattered
showers. Another moisture surge will occur on Thursday, and
wetter weather will occur on Friday and Saturday as a weak upper
level trough passes over a moisture plume from a tropical wave
passing south of the area and instability increases. Currently our
wettest time is expected to be Saturday and Saturday night.

&&

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

A mid to upper level short wave trough along with the sub-tropical
jet is forecast to weaken and continue to move east of the region
through Wednesday. This is to be replaced by an upper level ridge
which will bring stable conditions aloft and place the region on the
subsident side of the upper trough today through Tuesday. The
building upper level ridge will also strengthen the trade wind
cap inversion across the region and help limit moisture transport
across the region by Tuesday. In the low levels, the surface ridge
is forecast to slowly move eastward into the central and
northeast Atlantic through Wednesday. This in turn will maintain a
moderate east to southeast low level wind flow.

For the rest of the morning hours, an elongated area of low level
moisture is still forecast to cross the region, and is expected to
bring an increase in shower activity across the local area while
affecting portions of the windward side of the islands. During the
afternoon hours, the shower activity may become scattered to numerous
across portions of the central interior and northwestern PR while
isolated showers will remain possible around the USVI.

Low-level moisture transport is then expected to decrease across the
region Tuesday through Wednesday in response to the winds becoming
more southeasterly and the increasing stability aloft. Still,
however, expect sufficient moisture to be available to aid in the
development of isolated to scattered showers--mainly over the
central interior and western portions of Puerto Rico each
afternoon. Elsewhere, including the U.S. Virgin Islands we should
experience mostly sunny skies and pleasant weather conditions in
most areas,except for some early morning passing showers on the
windward side of the islands and over the coastal waters, followed
by isolated afternoon showers mainly downwind of the islands or
just offshore.

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

At upper levels, the broad upper level ridge over the Caribbean,
with an axis over Hispaniola, will edge slowly east through our
local area over the weekend. A weak short wave will move through
the ridge and enhance the shower activity breeding in the much
wetter atmosphere to be in place by Saturday. A stronger trough
over western Cuba on Saturday, will cross through the local area
Monday night, after which moisture will greatly diminish.

At mid levels moisture increases as winds turn southwesterly
Friday and Saturday since high pressure over the western
Caribbean will move into the western tropical Atlantic. Mid levels
will be considerably wetter Friday through Monday.

At lower levels, a moisture surge will move through on Thursday.
A plume of moisture is lifted off a tropical wave passing well
south of the area and crosses through the area Friday and
Saturday. It is on Saturday afternoon that the best moisture is to
be seen. This will also be the time when 500 mb temperatures
reach minus 8.5 degrees. Numerous showers and some thunderstorms
are expected late this week and possibly into Sunday of next week
even though 500 mb temperatures warm slightly through Monday.
Otherwise the period will see overnight and morning showers on the
eastern slopes of Puerto Rico followed by afternoon showers in
western Puerto Rico. Some of the showers and thunderstorms will be
heavy enough over the weekend to provoke urban and small stream
flooding.

&&

.AVIATION...VCSH at TIST/TISX and TJSJ/TJPS til 06/12z as SHRA will
move eastwards across the flying area en route btwn islands. Mtn
Tops obscr ovr E PR due to passing low clds/SHRA. Aft
06/16Z...Incr clds with Isold-Sct SHRA ovr the west and ctrl Mtn
range of PR with VCSH mainly at TJMZ/TJBQ. Isold SHRA psbl nr TJSJ
but of short duration and no sig operational WX impacts. Sfc wnds
nr 10 kts fm E incr to 15-20 KTS with ocnl higher gusts and sea
breeze variations aft 06/14z. Maximum winds W-WNW 45-55 kt btwn
FL300-490.

&&

.MARINE...Marine conditions will improve through Wednesday. seas
will rise on Thursday into Friday and then subside over the
weekend. Small craft advisory conditions are not expected through
next Monday in the forecast area, but the frequency of
thunderstorms will increase toward the end of the week.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 88 75 / 50 40 40 20
STT 86 77 86 77 / 50 20 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
455 AM AST Tue May 7 2019

.SYNOPSIS...
The mid to upper level ridge is to hold across the region today
through Wednesday supporting stable conditions aloft and decreasing
moisture transport. The local pressure gradient will continue to
relax over the next few days as the surface high pressure across
the Atlantic slowly moves farther east of the region. This will
result in decreasing east to southeast trade winds through Wednesday.
By Thursday and Friday...expect a short wave trough to become amplified
across the west Atlantic. This will begin to erode the mid to upper
level ridge now in place and again destabilize the upper levels while
weakening the trade wind cap inversion by the upcoming weekend. In
addition, increasing low level moisture convergence and the passage
of a weak tropical wave over the eastern Caribbean will promote better
potential for a moist and unstable weather pattern for the weekend.

&&

.SHORT TERM...Today through Thursday...
A mid to upper-level ridge will build overhead and hold throughout
the short-term period. This will maintain the atmosphere above
700 mb very dry, suppressing the development of deep and organized
convection across the area. As a result, a mainly fair weather
pattern is expected. However, enough low-level moisture will be in
place from time to time to result in some brief showers across
portions of eastern PR and the USVI during the overnight and
morning hours followed by showers developing across western PR
during the afternoon hours due to daytime heating and local
effects. Given the dry air aloft, the showers that develop across
western PR during the afternoon hours are expected to be short-
lived. Therefore, significant rainfall accumulations are not
expected at time.

.LONG TERM...Friday through Tuesday
At upper levels, the broad upper level ridge will shift eastward
and flatten across the region as a short wave will move across the
southwest Atlantic and become amplified. This will again bring unstable
conditions aloft and provide good ventilation and divergence aloft for
convective development during the latter part of the work week and
through the upcoming weekend. Therefore a much wetter pattern with
enhance convection is so far expected by Friday but especially over
the weekend. Recent model guidance continued to suggest a very moist
and unstable weather pattern with layered precipitable water exceeding
2.00 inches in some areas by the weekend and especially late Saturday
through Sunday. At lower levels, increasing moisture convergence is
forecast to begin on Friday as good tropical moisture accompanying
a tropical wave will be lifted across the region as the aforementioned
wave passes just south of the area. Therefore, based on recent guidance,
looking for scattered to numerous shower activity with good potential
for enhanced thunderstorm activity during most of the period with the
best change so far late Saturday through Sunday and possibly into early
Monday.

A gradual improvement is expected by Tuesday as the upper trough weakens
and lifts eastward and a ridge builds just west of the area. This will
support the strengthening the trade wind cap inversion favoring
lesser chance for widespread convective development across the
forecast area.

&&

.AVIATION...Mainly VFR conditions will prevail across all local terminals
throughout the period. Sct SHRA expected across western PR between
07/16z-22z, possibly affecting the vicinity of TJMZ/TJBQ. Brief MVFR
conditions cannot be ruled out. Winds will be out of the E at less
than 10 knots through 07/12z, increasing to 12 to 20 knots with gusts
up to 25 kts and sea breeze variations after 07/14z.

&&

.MARINE....Choppy seas up to 6 feet expected to continue today
due to winds up to 20 knots across most of the local waters and
passages. A gradual diminishing of winds and seas is forecast at
least through Friday. There is a moderate risk of rip currents
across many of the north and south facing beaches today.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 89 76 / 40 10 10 10
STT 86 76 86 76 / 20 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
350 AM AST Wed May 8 2019

.SYNOPSIS...

A mid to upper-level ridge will hold across the region through
Thursday thus creating relatively stable weather conditions.
However, shallow moisture could lead to the development of streamers
today over Puerto Rico and the U.S. Virgin Islands. Friday a mid to
upper-level trough is forecast to develop west of the area and
slowly erode the mid to upper-level ridge over the region. The
weakening of the mid to upper-level ridge will allow low-level
moisture to slowly filter into the region through the weekend. Also,
a weak tropical wave in the Caribbean waters will enhance low-level
moisture over Puerto Rico on Saturday through Sunday. Therefore wet
and unsettled weather is expected this weekend through early next
week.

&&

.SHORT TERM...Today through Friday...

Mid to upper-level ridge will continue to hold across the area
through Thursday. This will maintain the atmosphere above 700 mb
very dry, suppressing the development of deep and organized
convection. At lower levels, patches of moisture will move across
the area from time to time. This will result in some brief showers
moving across the local waters and portions of eastern Puerto Rico
and the USVI during the overnight through mid-morning hours,
followed by the development of showers across the northwest quadrant
of Puerto Rico during the afternoon hours due to daytime heating and
local effects. Additional showers in the form of streamers may also
develop downwind of the USVI and El Yunque, affecting the San Juan
metro area, given that the low-level flow will continue to be
unidirectional from the east-southeast. At this time, given the dry
air aloft present, significant rainfall accumulations are not
expected.

The upper-air pattern will begin to change by Friday as a mid to
upper-level trough will begin to amplify across the southwest
Atlantic, eroding the ridge. This will serve to increase the
instability aloft as well weaken the trade wind cap. Therefore,
shower activity during the afternoon hours across western Puerto
Rico could be more enhanced as a result of more favorable conditions
aloft.

&&

.LONG TERM...Saturday through Wednesday...

The long-term period will be wet and unsettled as a result of
moisture convergence in the low-levels, and increasing mid to
upper-level moisture over the region. The low-level moisture is a
result of a weak tropical wave which is forecast to move into the
Caribbean waters on Saturday. This wave is forecast to remain
well south of the area. Current guidance keeps precipitable water
values around 1.5 to 2.0 inches through the entire long-term
period.

A developing trough and sub-tropical jet will enhance upper-
level divergence over portions of the western and interior areas
of Puerto Rico. Also, the upper-level divergence will cause the
the upper- levels of the atmosphere to be unstable thus conducive
for thunderstorm development during the afternoon.

The combination of increasing moisture through the entire
atmospheric column and instability aloft combining with local and
diurnal effects will cause wet and unsettled weather conditions
across the region through the middle of the workweek.
Additionally, deep moisture convection could lead to urban and
small stream flooding across many areas during the afternoon. As a
result of model consistency the forecast at this time is medium
high.

&&

.AVIATION...

Mainly VFR conditions will prevail across the local
flying area. Sct SHRA expected across western and northwest PR
between 08/16z and 08/22z, possibly affecting TJMZ/TJBQ. MVFR
conditions cannot be ruled out. A line of SHRA may also affect the
San Juan metro area between 08/16z and 08/20z, resulting in VCSH
across TJSJ. Winds will be from the east at less than 10 knots
through 08/12z, increasing to 10-20kts with higher gusts and sea
breeze variations after 08/14z.

&&

.MARINE...

Seas will range from 3 to 5 feet across the local and outer waters
through Friday. Winds will be out of the east to southeast at 10
to 15 kts with higher gusts possible. A low to moderate risk of
rip currents for all the local beaches through the weekend.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
450 AM AST Thu May 9 2019

.SYNOPSIS...Surface high pressure will continue to lift farther eastward
into the northeast Atlantic to maintain a light to moderate east to
southeast wind flow, while inducing a weak trough across the northeastern
Caribbean. A tropical wave is forecast to enter and cross the eastern
Caribbean late Friday and through the weekend while bringing a significant
increase in low level moisture. A mid to upper level trough will continue
to amplify just west of the region today, then lift east northeast
across the area Friday through the weekend to increase
instability aloft and support a moist and unstable airmass across
the forecast areas through the early part of next week.

&&

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

Not much change in the overall pattern is expected for today as a
ridge aloft will continue to maintain the atmosphere above 700 mb
very dry, suppressing the development of deep and organized convection.
Therefore, similar conditions as to what as been observed during
the last couple of days is expected with a few brief showers affecting
eastern portions of PR and the USVI during the morning hours followed
by the development of showers across interior and northwest PR during
the afternoon hours due to daytime heating and local effects. Additional
showers may also develop downwind of the USVI and El Yunque, affecting
the San Juan metro area.

The overall synoptic pattern will begin to change by Friday as a mid
to upper-level trough begins to amplify across the southwest Atlantic.
This will weaken the ridge aloft, allowing for better instability
aloft and more moisture to be introduced into the mid- levels of
the atmosphere. Therefore, more enhanced showers are expected across
interior and northwest PR during the afternoon hours. Since the
instability aloft will be greater with the 500 mb temperatures
dropping to between -7 to -8 degrees Celsius, isolated thunderstorms
were put into the forecast for the afternoon hours. The USVI is
expected to observe mainly fair weather conditions with just a few
showers expected.

On Saturday, the mid to upper-level trough continues to amplify even
more with the axis situated near central Cuba. This will increase
the divergence aloft. Deeper moisture will also be moving over the
area with precipitable water values increasing to between 1.75 to 2
inches. Therefore, more widespread shower and thunderstorm activity
is expected, especially during the afternoon and nighttime hours
when the upper-level forcing and the moisture will be the best.

.LONG TERM...Sunday through Thursday..
A fairly warm, moist and unstable weather pattern is forecast due
to strong low level moisture convergence produced by the tropical
wave, along with increasing mid to upper- level instability supported
by a jet maxima which will round the base of the amplifying upper
trough crossing the region. Although the wave is forecast to move
just south of the region, peripheral moisture along the north and
east sections of the wave axis will converge and pool across the
region favoring a very moist and unstable weather pattern.

Although models still remain in slight disagreement as far as timing
of this wet pattern, all suggest an increase in deep layered moisture
and a very unstable weather pattern through the weekend and into
the early part of next week. Current guidance still maintain precipitable
water values between 1.5 to 2.0 inches through most of the period.
The best potential for increased and enhanced convective development
still looks like late Saturday afternoon through Sunday.

A slight improvement is forecast on Monday but there will be still
potential for additional afternoon shower and thunderstorm development
mainly over parts of the interior and west sections of Puerto Rico.
This will be followed by continued improvement with drier conditions
and lesser activity Tuesday through the remainder of the period. By
then the high pressure ridge is expected to build aloft and strengthen
the trade wind inversion while the low level easterly trades increase
and bring a drier airmass to the region.

All in all, the overall expected increase in deep layered moisture
and widespread convection over the islands may lead to urban and
small stream flooding across many areas each afternoon, at least
through the early part of next week. Stay tuned as we will continue
to monitor the on going and expected weather pattern.

&&

.AVIATION...Mainly VFR conditions will prevail across all terminals
during the next 24 hours. SHRA expected across interior and western
PR between 09/16Z and 09/23Z. This may result in TEMPO MVFR
conditions for TJBQ and TJMZ as well as VCSH at TJPS. Additional
SHRA may affect the San Juan metro area between 09/15Z and 09/20Z,
resulting in VCSH at TJSJ. Winds will continue at less than 10 kts
through 09/12Z, increasing to around 15 kts with higher gusts and
sea breeze variations after 09/14Z.

&&

.MARINE...A gentle to moderate easterly wind flow is forecast across
the regional waters through Friday. A small northerly swell will arrive
and move across the Atlantic waters and passages today and Friday.
Overall fairly tranquil marine conditions will prevail with Seas up
to 5 feet and winds between 10 to 15 knots. There is a moderate risk
of rip currents for some of the north and east local beaches.

&&

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

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
413 AM AST Fri May 10 2019

.SYNOPSIS...An unstable weather pattern is expected through the
weekend as the combination of a mid to upper-level trough and
deeper moisture will result in an increase in the coverage and
intensity of showers and thunderstorms. Conditions will improve by
early next week as a ridge builds aloft, resulting in less shower
activity across the area.

&&

.SHORT TERM...Today through Sunday...

A light to moderate east to southeast low-level winds will prevail
today becoming more southeasterly Saturday through Sunday due to the
passage of weakly induced low level trough and a tropical wave
moving westward across the eastern Caribbean. An amplifying mid to
upper-level trough and the associated subtropical jet will also move
across the southwestern Atlantic today through the weekend and
continue to erode the upper level ridge. This will weaken the trade
wind cap inversion while increasing layered moisture content/cloud
cover.

The combination of these features during the period will favor
strong low level moisture convergence/pooling across the region
along with increasing upper level divergence and instability. This
will therefore increase potential for shower development across the
islands and regional waters during the entire period. Early morning
showers will continue to stream westward while affecting portions of
the north and east coastal areas of the islands. Afternoon shower
development will follow mainly over the central interior, and
northwestern sections of Puerto Rico; as well as over the eastern
interior and parts of the San Juan metro where isolated to scattered
showers will be likely in the form of streamers steered by the east
southeast wind flow. Isolated afternoon showers can also be expected
to develop on the west end and downwind of the U.S. Virgin Islands
each day.

The anticipated periods of locally heavy rains during the afternoons
will cause ponding of water on roadways at times and may lead to
urban and small stream flooding in some areas today and over the
weekend. Current model guidance still maintain high precipitable
water values up to near 2.0 inches through the period. However, The
best potential for increased and enhanced convective development
still looks like late Saturday through Sunday but overall a moist
and unstable weather pattern is in store for the entire period.


.LONG TERM...Monday through Friday...

Conditions will improve by early next week as the upper-level
trough pulls away and a ridge aloft builds overhead. This will
result in a decrease in shower activity across the area. However,
enough moisture will still be present to result in some passing
showers across eastern portions of PR and the USVI during the
overnight and morning hours followed by more enhanced showers
across interior and western portions of Puerto Rico during the
afternoon hours due to daytime heating and local effects.
Isolated thunderstorms are also possible with the afternoon
activity given that there will be sufficient moisture in the mid-
levels and 500 mb temperatures will range between -7 and
-8 degrees Celsius, allowing for enough instability aloft to be
present. This ridging pattern is expected to hold through the end
of the work week.

&&

.AVIATION...Prevailing VFR cond durg prd. SHRA en route btw local
islands and ovr the coastal waters...SCT ocnly BKN lyrs nr FL022...
FL050...FL090...FL250. Mtn top obscr ovr Ern PR low cld lyrs/-SHRA
til 10/14Z. SHRA psbl nr TJSJ/TJMZ/TJBQ with brief MVFR low cigs
and SHRA btw 10/17Z-10/22Z. Sfc wnds bcmg fm E 10-15 kt with ocnl
higher gusts and sea breeze variations aft 10/14z. L/lvl wnds fm E-
SE 10-20 kt blo FL100. FEW tops btw FL100-FL150.


&&

.MARINE...Fairly tranquil seas between 3 and 5 feet will prevail
across the regional waters today and through the upcoming
weekend. Seas will become choppy by early next week as a larger
northerly swell arrives and spreads across the regional waters.

For beachgoers, a small northerly swell currently affecting the
area will result in a high risk of rip currents for the beaches
located along the north-central coast of Puerto Rico as well as
the San Juan and Vicinity coast. A low to moderate risk of rip
currents is expected elsewhere.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 77 88 76 / 50 30 50 50
STT 86 77 85 77 / 30 50 60 60