Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
508 AM AST Fri Aug 16 2019

.SYNOPSIS...The Saharan dust will clear out of the area tonight,
leaving only traces for the next several days. A weak low level
trough will move through on Saturday and increase showers and
thunderstorms. Then moisture will increase Sunday through Monday
with the passage of a tropical wave on Monday. Localized urban and
small stream flooding are possible on Monday. Some moisture will
continue Tuesday. Then, sporadic showers and isolated
thunderstorms will follow patches of moisture through the area for
the remainder of the week.

&&

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

Hazy skies due to Saharan dust are expected to continue through
tonight. The Saharan dust will also continue to produce stable
weather conditions across the region with very limited shower
activity expected. However, patches of low-level moisture riding
in the northeasterly trade wind flow may continue to spark some
passing showers across the regional waters and affecting northern
and eastern portions of Puerto Rico and the USVI through the early
morning hours. Then, showers and isolated thunderstorms are
expected across southwest Puerto Rico this afternoon as the
available moisture combines with strong daytime heating and local
effects. However, the activity that does develop should be short-
lived and only result in light rainfall amounts.

A broad upper-level low is expected to be situated just north of the
area with an inverted trough at low to mid-levels for Saturday.
Therefore, conditions are expected to become favorable for the
development of more significant shower and thunderstorm activity to
materialize, especially across interior and western Puerto Rico
during the afternoon hours when the available moisture combines with
strong daytime heating and sea breeze convergence. Therefore, there
is a better potential for urban and small stream flooding to occur
in areas that receive a prolonged period of heavy rainfall activity.
Showers in the form of streamers may also develop downwind of the
USVI and El Yunque, affecting the San Juan metro area.

A drier air mass ahead of a tropical wave, currently located near 50
degrees west Longitude as of this morning, will move over the area
Saturday night through early Sunday afternoon. Therefore, mainly
fair weather conditions can be expected. Afternoon convection is
expected across northwest Puerto Rico due to local effects. Then, as
the moisture associated with the tropical wave begins to increase
late Sunday afternoon into Sunday night, showers are expected to
increase in coverage across the Caribbean waters and affect portions
of the USVI and eastern Puerto Rico.

.LONG TERM...Monday through Friday...
Sunday night will bring the entrance of a strongly tilted
tropical wave into the forecast area from the southeast. This will
spread moisture over the area that will peak on Monday and then
steadily decline through Wednesday. Areas of moisture then move
through the forecast area Wednesday night and Friday morning.
The GFS has found this wave difficult and has had some fairly wide
variation in intensity and timing from run to run. For the local
area, Monday afternoon may still be the most uncertain period. For
having moisture in place and good convergence in lower levels and
modest divergence aloft the low probabilities of precipitation
over land areas and the placement of near 100 percent POPs north
of the Saint John in the outer Atlantic waters seems questionable
so have left better chances for rain where orographic lifting
will be taking very moist air and generate convection over land
that will not be completely devoid of heating. After clouds clear
somewhat on Tuesday, lingering moisture should be able to generate
another day of good shower and thunderstorms activity. Wednesday
through Friday will see passing showers and recurring afternoon
showers and thunderstorms, however warm mid levels forecast by the
models on Thursday to be minus 2 to minus 4 degrees at 500 mb,
seem to indicate that strong convection will not occur.

Upper levels in the atmosphere show only minor changes in the
divergence field except as the leading edge of the tropical wave
passes on Monday. At that time, areas of higher divergence aloft
are seen to pass over Puerto Rico, but not so much over the U.S.
Virgin Islands.

&&

.AVIATION...Mainly VFR conds with hazy skies expected to prevail
across the area during the forecast period. Sct SHRA/TSRA expected
across SW PR between 16/16z and 16/22z, affecting the VCNTY TJMZ.
However, no significant impacts to operations are expected as the
heaviest activity should remain to the south of the terminal.
Low-level winds from the ENE-NE below 10 knots through 16/12z,
increasing to 10 to 20 knots with higher gusts and sea breeze
variations after 16/14z. Max winds ENE 20-25 kt btwn FL050-180 and
W 20-25 kt btw FL340-400.

&&

.MARINE...Marine conditions are expected to remain below small
craft advisory criteria through the next 7 days. Thunderstorms
Monday through Wednesday could generate higher winds and seas.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 78 88 78 / 40 40 30 20
STT 91 78 89 79 / 20 30 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
538 AM AST Sat Aug 17 2019

.SYNOPSIS...A weak trough will bring scattered showers to the
area today. A tropical wave will bring showers and thunderstorms
Sunday through Tuesday with drying on Wednesday. A weak
disturbance on Thursday and another wave on Saturday morning of
next week will bring some more showers and thunderstorms.

&&

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

A broad upper level low north of the region and an associated
lower level trough is producing scattered to locally numerous
showers and isolated thunderstorms across the regional waters and
over portions of the islands. These two features in combination
with daytime heating and sea breeze convergence will aid in the
development of afternoon showers and thunderstorms, mainly along
the interior and western sections of PR as well across San Juan
and vicinity. Urban and small stream flooding, frequent lightning
and brief gusty winds are possible with this activity. Elsewhere,
brief heavy showers can develop during the afternoon hours.

Moisture drops overnight, as a drier air mass ahead of a tropical
wave moves from the east and limits shower activity across the
region. However, due to the proximity of the upper level low
thunderstorms can not be ruled out across portions of the Atlantic
and western waters of PR. By Sunday afternoon, tropical moisture
associated to the tropical wave should gradually increase from the
eastern Caribbean waters into the forecast area. As the wave is not
expected to cross the region till later in the day, diurnally
induced afternoon showers and thunderstorms are expected to develop
in the usual areas and between the USVI and eastern PR waters.

Model guidance suggest that the low to mid levels of the atmosphere
will be saturated due to the wave passage and that the strongest or
best chances for rain and thunderstorms should be across the
Caribbean waters and eastern sections of PR and over the USVI
through Monday afternoon and similar or less amounts over the
western half of PR.

.LONG TERM...Tuesday through Saturday...
High pressure at upper levels will have nosed in from the east
northeast over the local area by Tuesday. Although lower pressure
will be southeast high pressure will hold to the north through the
end of the period and be the dominant influence over the weather.

Behind the tropical wave that moved through late Sunday and Monday
a band of moisture will flow over the area in east southeast flow
until a 700 mb ridge passes on Tuesday afternoon (20/18Z). Then
flow will switch to east northeast at 700 mb and bring some of the
moisture back over the area. This will allow good convection over
Puerto Rico during the afternoon and evening. This flow will also
be weakly reflected in the surface flow so as to keep temperatures
on the north coast more moderate and generally no higher than the
lower 90s a few miles inland. Conditions on Wednesday and
Thursday become more stable and moisture will fall below 2 inches
of precipitable water on Tuesday night with only minor peaks on
Wednesday night and Thursday evening to bring enhancement to
shower activity. Thunderstorms should be limited, if any, to the
afternoon in western Puerto Rico Wednesday. Although moisture
will continue low Wednesday through Friday, some disturbances will
trigger scattered showers Thursday afternoon and Friday night
into Saturday.

&&

.AVIATION...Mainly VFR conditions expected through the morning hours
across all terminals. Afternoon SHRA/TSRA could cause tempo MVFR to
brief IFR conditions at TJMZ/TJBQ. Brief MVFR conditions are also
possible at TJSJ btw 17z-21z. Winds are expected to prevail from the
E-ESE at 10-15 kt aft 14z with sea breeze variations.


&&

.MARINE...Small craft advisory conditions are not expected through
the next 7 days. Brief gusty winds, torrential rains and frequent
lighting will accompany thunderstorms generated by a passing
tropical wave Sunday night through Tuesday night.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 89 78 / 40 20 40 60
STT 89 80 88 78 / 50 40 50 70

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
529 AM AST Sun Aug 18 2019

.SYNOPSIS...A tropical wave and associated plume of moisture is
expected to affect the region today through at least Tuesday,
resulting in a higher potential for shower and thunderstorms
activity and a threat for urban and small stream flooding.
Although relatively tranquil conditions are expected Wednesday
through Friday, patches of low-level moisture will trigger shower
and thunderstorm activity from time-to-time. The next tropical
wave is expected to arrive by Friday into Saturday.


&&

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

An active tropical wave, currently just south of the forecast area,
will gradually increase tropical moisture and instability across the
region through the short term period. Wind shear due to an upper
level ridge building behind the wave and northeast of the region is
expected to keep the bulk of the shower and thunderstorm activity to
the south and east of the region. Regardless, a wet and unstable
weather pattern is expected to unfold on Monday and Tuesday as
precipitable water content(PWAT) is forecast to increase from 1.80
inches today to 2.35 inches by Tuesday.

For today, passing showers will increase through the morning hours
across the USVI and eastern sections of PR and isolated
thunderstorms can not be ruled out through the entire period across
the Caribbean waters. Another active afternoon is expected as
showers and thunderstorms are forecast to develop from el Yunque
mountain into the San Juan metro area and along the interior and
western sections of PR. Urban and small stream flooding is expected
with this activity. For Monday and Tuesday, model guidance has high
PWAT content over the region but particularly over the eastern half
of the forecast area and as well across the Atlantic and Caribbean
waters. This will increase the potential for flooding rains across
the USVI and eastern sections of PR. The interior and western
sections of PR should receive similar rainfall amounts, however,
less rainfall amounts are possible if daytime heating is not
sufficient to trigger afternoon convection due to the presence of
mid to upper level clouds.

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

A migrating surface high pressure moving westward across the
north central Atlantic will maintain a moderate to locally fresh
east to southeast wind flow across the region through at late
Saturday. As this high moves into the western Atlantic late
Saturday into Sunday, winds are forecast to briefly shift from the
northeast. Shower and thunderstorm activity will be triggered by
patches of low-level moisture moving across the region from time-
to- time. This activity will favor eastern Puerto Rico during the
overnight and morning hours, while clustering along the interior
and western sectors of Puerto Rico in the afternoon. Lack of upper
level support will limit the frequency and intensity of this
activity. The next tropical wave is expected to approach the
region Friday into Saturday, increasing the potential for shower
and thunderstorms activity. Relatively tranquil conditions are
expected to return on Sunday.


&&

.AVIATION...Mainly VFR conditions expected through the morning hours
across all terminals. Afternoon SHRA/TSRA could cause tempo MVFR
conditions at TJMZ/TJBQ/TJSJ. Winds are expected to prevail from the
east at 8-15 kt with sea breeze variations and higher gusts after
14z.


&&

.MARINE...A surface high pressure centered across the north
central Atlantic will maintain a moderate to fresh east wind flow.
Tranquil marine conditions with seas up to 5 feet and winds up to
15 knots are expected across most of the regional waters. However,
small craft operators should exercise caution across the coastal
waters north of Puerto Rico due to locally winds up to 20 knots.
There is a moderate risk of rip currents for beaches along the
north central to northwest coast of Puerto Rico, as well as for
Playa Ballena in Guanica, Culebrita in Culebra and Cramer Park in
Saint Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 77 87 78 / 40 80 80 50
STT 89 79 87 78 / 50 80 80 60

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
512 AM AST Mon Aug 19 2019

.SYNOPSIS...A departing tropical wave and associated plume of
moisture will continue to affect the local islands and waters
through at least Tuesday, resulting in a higher potential for
shower and thunderstorms activity and a threat for urban and small
stream flooding. Relatively tranquil conditions with the potential
for locally induced showers and isolated thunderstorms are
expected Wednesday through Friday. An elongated area of low-level
moisture ahead of wind surge and a passing tropical wave are
expected to increase the potential for shower and thunderstorm
activity on Friday into Saturday and Monday, respectively.



&&

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

For today, model guidance continues to suggest a wet and unstable
weather pattern with high precipitable water content over the region
but particularly over the eastern half of the forecast area and
across the regional waters. This will result in flooding rains
across the USVI and eastern sections of PR. The interior and western
sections of PR should receive similar rainfall amounts during the
afternoon due to the presence of mid to upper level clouds. However,
if skies clear somewhat and allow for daytime heating, higher
rainfall amounts are possible with any afternoon convection over
western PR. Due to saturated soils from yesterday`s rainfall, flash
flooding as well as mudslides can not be ruled out with any heavy
showers.

On Tuesday, guidance has shown a downward trend of the lingering
tropical moisture and the ECMWF for example brings drier air at
700mb overnight, while the GFS keeps the drier air at this level
south of the forecast area during the same time. Both models agree
on a wind shift from the northeast and the best moisture north of
the region through Tuesday evening. Having said that, modified
previous forecast to keep the best chances of rain along the
Cordillera Central and west/southwest PR in possible strong diurnal
afternoon convection. By Wednesday, a drier air mass will promote
more stable conditions across the region and shower activity will be
confined to the west coast of PR.


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

A migrating surface high pressure moving westward across the
north central Atlantic will maintain a moderate to locally fresh
east to southeast wind flow across the region. Relatively tranquil
weather conditions are forecast on Thursday and continuing through
Friday evening. However, patches of low-level moisture will bring showers
to the US Virgin Islands and Puerto Rico during the overnight and
early morning hours. Then, lingering moisture supported by
diurnal heating and local effects will trigger locally induced
showers and thunderstorms along the interior and over portions of
northwestern Puerto Rico each afternoon. By late Friday night
through Sunday morning, a wind surge ahead of a tropical wave and
south of a developing surface high will transport an elongated
area of low-level moisture across the region, increasing the
potential for shower and thunderstorm activity. Weather conditions
are to briefly improve Sunday through Monday, but moisture
advection from a passing tropical wave will once again increase
the potential for shower and thunderstorm activity by Monday
afternoon.


&&

.AVIATION...Tempo MVFR conditions are expected through the day across
TIST/TISX/TJSJ/TJBQ/TJMZ due to SHRA/TSRA. VCTS/VCSH is expected
across the rest of the terminals. MTN tops obscd across east PR
through much of the forecast period and over the interior and west
PR during the afternoon hours. Tempo IFR conds are possible at
TJMZ/TJBQ btw 17z-21z. Winds are expected to prevail from the east-
southeast at 10-15 kt with sea breeze variations after 14z.


&&

.MARINE...Tranquil marine conditions with seas up to 5 feet and
east winds up to 15 knots are expected across the regional waters
today. A tropical wave will continue to move across the area,
increasing the potential for showers and thunderstorm development
through at least Tuesday. There is a moderate risk of rip currents
for beaches along the north and south coast of Puerto Rico, as
well as Culebrita in Culebra and Cramer Park in Saint Croix. A low
risk of rip currents will prevail elsewhere.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 79 87 78 / 50 50 40 30
STT 88 79 88 78 / 70 60 60 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
520 AM AST Tue Aug 20 2019

.SYNOPSIS...Lingering tropical moisture in combination with
daytime heating and other local effects, will result in showers
and thunderstorms over the interior and western sections of PR
this afternoon. A drier air mass is expected to promote fair
weather conditions during the second part of the workweek, but
diurnally induced afternoon showers are expected each day over
western PR and from streamers off the USVI and east PR. A weak
tropical wave is forecast to bring better chances of rain during
the weekend. A Saharan Air Layer is forecast to arrive late in the
weekend.


&&

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

The TJSJ precipitable water image and the CIMSS total precipitable
water shows some moisture across the region. Additionally, the GOES-
16 water vapor shows the patches of moisture moving into the region
from the east and northeast. The TJSJ 00Z sounding had a
precipitable water value of 2.15 inches; this value is two standard
deviations above the sounding climatology for August.

Mid to upper-level clouds are being blown across portions of Puerto
Rico this morning. The clouds are from the departing tropical wave
which moved away from the area late early Monday morning. We can
expect the cloud cover to continue to diminish throughout the
morning hours. The scattered cloud cover should not affect the
surface heating this afternoon. The combination of increasing low-
level moisture, significant surface heating coupled with topographic
effects will lead to development of scattered to numerous showers
and isolated thunderstorms. This activity is expected to start over
the U.S. Virgin Island and the eastern areas of Puerto Rico this
morning, then across the interior and the western areas of Puerto
Rico this afternoon. Rainfall amounts are forecast to range from
0.50 to 1.00 inches this afternoon. Saturated soils from previous
days rainfall, coupled with todays expected rainfall totals could
cause urban and small stream flooding. Also, mudslides are possible
in higher terrain areas as a result of saturated soils.

Wednesday and Thursday, a drier air mass is progged to move into the
region from the east, this will limit the development of widespread
showers and isolated thunderstorms during the afternoons. Relative
humidity value`s at the mid to upper-levels of the atmosphere on
Wednesday and Thursday are forecast to range from 10 to 25 percent,
while the 1000 to 850 mb relative humidity values during this time
will remain above 80 percent. The 1000 to 850 mb relative humidity
values will aid in the development of shallow convection during the
afternoons in the form of isolated to scattered showers. The trigger
for development will be the moisture embedded in the easterly trade
winds, and the development of the sea breeze during the afternoons.
Due to limited mid to upper-level instability and moisture showers
that do develop will be short-lived.

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

A mid to upper level ridge north of the region is expected to
promote fair weather conditions across the islands on Friday.
However, diurnally induced afternoon convection should develop
over western Puerto Rico. By Saturday, a tropical wave is expected
to increase shower and thunderstorm activity across the region.
At the same time a 700mb high pressure moving from the tropical
Atlantic will bring a wind surge behind it and as well a Saharan
Air Layer. Therefore, breezy conditions and hazy skies due to
Saharan dust are expected late in the weekend. At the end of the
long term period, a tropical wave is forecast to increase shower
and thunderstorm activity. Both global models are showing
different solutions at this moment. The GFS has a strong tropical
wave entering the southeastern Caribbean by Monday morning, while
the ECMWF has a slower solution(including the timing of the 700mb
high) and a weak wave at the end of the period.


&&

.AVIATION...VCTS/VCSH are possible across the U.S. Virgin Island
terminals and eastern PR through 20/12Z. SHRA/TSRA are forecast to
develop across terminal TJBQ and TJMZ by 20/18Z before diminishing
by 21/02z. SHRA/TSRA could cause brief MVFR conds. Sfc winds will
be out of the east at 15 to 20 kts with sea breeze variations
and higher gusts possible due to SHRA/TSRA.


&&

.MARINE...Seas will continue to range between 2-5 feet through the
end of the week with winds from the east between 10-15 knots.
Showers and thunderstorms are expected once again this afternoon
over the coastal western waters of Puerto Rio. Strong gusty winds
and frequent lightning are possible. A moderate risk of rip
currents will prevail for the northern and southern beaches of PR
and across St. Croix through the weekend.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 78 88 78 / 60 30 40 30
STT 88 79 89 78 / 40 30 30 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
503 AM AST Wed Aug 21 2019

.SYNOPSIS...A drier air mass is expected to promote fair weather
conditions today. However, diurnally induced afternoon showers and
thunderstorms are expected over portions of the interior and
western Puerto Rico. Although drier mid level air is expected to
continue through at least Friday, a weak trough and a tropical
wave are expected to increase low level moisture between Thursday
and Saturday. A Saharan Air Layer will bring drier conditions and
Saharan dust by the end of the weekend into early next week.

&&

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

Fast moving showers embedded in the easterly trade winds continued
to push across the region during the overnight hours and this
morning. Due to their rapid movement rainfall amounts were less than
a tenth of an inch. Recent guidance shows the lingering moisture
holding over Puerto through the afternoon. The 00Z precipitable
water value showed a total of 2.33 inches, this low-level moisture
is also depicted on the CIMSS total precipitable site. The low-level
moisture combined with surface heating and orographic effects will
lead to the development of showers and isolated thunderstorms today.
In fact a TUTT low moving into the region will aid in shower and
thunderstorm development. The strongest showers and isolated
thunderstorms will develop across portions of the interior and
southwestern areas of Puerto Rico. Rainfall amounts are expected to
range from 0.50 to 1.00 inches. Also light 0-6 km mean wind flow
could cause showers and isolated thunderstorm to move slowly and
produce rainfall amounts higher than 1.00 inch. Furthermore, soils
remain saturated from previous days rainfall, and additional rain
today could cause urban and small stream this afternoon. Also,
mudslides are possible in areas of steep terrain. Winds will be out
of the east at 10 to 15 mph.

Model guidance shows a narrow band of drier air moving across the
U.S. Virgin Islands this afternoon, then across Puerto Rico later
this evening. The drier air mass will cause showers and
thunderstorms to come to an end once it moves over the aformentioned
areas.

Thursday, the drier air mass is expected to quickly race to the west
of Puerto Rico as the TUTT moves just west of the island. Weak
pertubations and patches of low-level moisture are expected to move
across the area on Thursday. Therefore, showers are forecast to
develop over the U.S. Virgin Islands and eastern areas of Puerto
Rico during the morning, then showers and isolated thunderstorms
across the other areas of Puerto Rico during the afternoon.

Friday, a tropical wave will bring an influx of moisture into the
area on Friday. The moisture coupled with modest instability and
orographic effects will lead to the development of showers and
isolated thunderstorms mainly across the interior and western areas
of Puerto Rico. At this time isolated to scattered showers are
forecast for the U.S. Virgin Islands and eastern Puerto Rico.

Afternoon precipitable water values for the last two days in the
short-term period will range from 1.70 to 1.80 inches. A surface
and mid-level ridge will hold across the region today through
Friday.

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

Lingering moisture associated to a tropical wave will continue
over the region on Saturday. This moisture in combination with
daytime heating and other local effects will result in showers and
thunderstorms developing during the afternoon hours over portions
eastern PR and as well along the interior and western sections of
PR. Urban and small stream flooding is expected with this
activity. Across the USVI, isolated to scattered showers are
expected. Trade winds are expected to increase on Sunday as a low
to mid level high moves from the east. A Saharan Air Layer will
bring Saharan dust and hazy conditions are forecast between Sunday
and Monday. Regardless, the available low level moisture in
combination with diurnal effects will cause showers and possible
isolated thunderstorms to develop over western PR. The 700mb high
is forecast to move west of the region by Tuesday morning and this
will allow for better moisture to pool over the region and as
steering winds turn from the northeast, showers and thunderstorms
are expected to develop over and south of the Cordillera Central
each afternoon.



&&

.AVIATION...VCSH are possible across the U.S. Virgin Island until
21/15Z. Then SHRA are expected across TJSJ by 21/15Z, then SHRA/TSRA
are forecast to develop across terminal sites TJMZ and TJBQ by
21/17Z with the activity diminishing by 22/03Z. SHRA/TSRA could
cause brief MVFR conditions. Winds will be out of the east at 15 to
20 kts.


&&

.MARINE...Relative tranquil marine conditions are expected during
the next few days as seas with seas in general at less than 5 feet
and easterly winds between 10-15 kt. However, winds and seas will
gradually increase on Friday and small crafts should exercise
caution by then across the Atlantic waters due to seas up to 6
feet and winds up to 20 knots. A moderate risk of rip currents
continues mainly for the northern beaches of PR.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 78 89 78 / 50 40 40 60
STT 88 78 90 79 / 50 60 60 60

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
503 AM AST Thu Aug 22 2019

.SYNOPSIS...

A mid to upper-level ridge will continue to hold over the region
through early Saturday morning. A tropical wave will move through
the area today which will cause showers and isolated
thunderstorms across the local waters and northwestern areas of
Puerto Rico this afternoon. A dry Saharan air mass is forecast to
pool over the region this weekend and hold through early next
week. The Saharan dust will cause hazy skies and limit widespread
shower development. However, showers and isolated thunderstorms
are expected to develop as a result surface heating and local
effects. Tropical moisture is forecast to return across the area
on Wednesday as the surface and mid-level ridges slide west of
Puerto Rico.

&&

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

A ridge pattern aloft will persist through the short term. A passing
tropical wave will bring showers across the local waters, the U.S.
Virgin Islands and the windward sections of Puerto Rico throughout
this morning. Periods of moderate to locally heavy rainfall will
cause hazardous driving conditions, brief gusty winds and ponding of
waters on roadways and in poor drainage areas.

Showers will spread into the interior and western sections of Puerto
Rico by mid-morning into the afternoon hours. The combination of
diurnal heating, orographic effects and sea breeze convergence will
aid in the formation of thunderstorms with heavy rainfall mainly
across the northwest quadrant of Puerto Rico. However, low-level
convergence and local effects will trigger additional showers with
isolated t-storms across the U.S. Virgin Islands and the eastern
sections of Puerto Rico including the San Juan Metro area.

Although moisture is forecast to slowly diminish each day, the
lingering tropical moisture will promote passing showers across the
islands and local waters overnight and during the morning. Then,
local effects will aid in the development of afternoon convection
over the western sections. Under a southeasterly wind flow, the
southern plains of Puerto Rico could expect benign rains each day,
especially on Friday morning.

&&

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

Sunday, residual moisture associated with a tropical wave will linger
through the early afternoon on Sunday. The moisture coupled with
daytime heating and local effects will yield showers and
thunderstorms during the afternoon across the interior and western
areas of Puerto Rico. There is a possibility for urban and small
stream flooding during the afternoon in flood prone areas. Sunday
evening the moisture will abate as a dry Saharan air mass push in
from the east Atlantic. The dry Saharan air is forecast to persist
through early part of the next week. Therefore, expect hazy skies
with isolated to scattered showers mainly during the afternoon with
the chance for isolated thunderstorms over western Puerto Rico. Once
again showers will develop due to daytime heating and local effects.
However, due to modest low-level moisture and limited upper-level
instability as a result of mid to upper-level ridges showers will be
short-lived. By Tuesday the 700 mb high shift to the southwest this
shift in the high will allow the tropical moisture to pool into the
region from the east. The return of the deep tropical moisture will
cause the dry Saharan air to diminish over the region. Also, the
tropical moisture will aid in the development of showers and
isolated thunderstorms during the afternoon especially over and
south of the Cordillera Central through the middle of the week.

&&

.AVIATION...

A weak tropical wave will bring SHRA across the local
flying area. These SHRA/+SHRA will result in brief MVFR conditions
at the terminals of E-PR/USVI/Leeward Islands thru the morning hrs.
SHRA/TSRA are expected to develop across the interior/west PR btwn
22/16-23z, affecting TJMZ/TJBQ and possibly JPS. JSJ/IST/ISX could
be affected too. The intensity of this activity is fcst to diminish
aft 22/23z. Winds will continue calm to light and vrb but gusty in
SHRA, increasing at 10 to 15 knots from the E/ESE by 22/13Z.

&&

.MARINE...

Seas up to 6 feet over the next several days. Winds out of the
east at 15 to 20 kts. There is a moderate risk of rip currents for
the northern beaches of Puerto Rico, Culebrita, and the southern
beaches of Vieques. Also, a moderate risk of rip currents for the
beaches of Salt River and Cramer Park in Saint Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 78 90 78 / 50 60 20 50
STT 89 80 89 80 / 40 40 30 40

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
438 AM AST Fri Aug 23 2019

.SYNOPSIS...

Today a tropical wave will create showers and isolated
thunderstorms across Puerto Rico this afternoon. A surface to
mid-level ridge will hold across the region through Friday
evening. A dry Saharan air mass is expected to trickle into the
region on Sunday and cause hazy conditions through the beginning
of the workweek. Although, a stable air mass will be in place
scattered to isolated showers are expected to develop during the
afternoons. On Tuesday moisture is expected to return as the
surface and mid-level ridges move southwest of Puerto Rico. The
returning moisture will end the Saharan dust event. At the end of
the workweek the weather will be unsettled due to increasing
moisture as a result of tropical waves moving near the area.

&&

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

The lingering moisture associated with yesterday`s tropical wave
will continue to bring passing showers across the windward sections
and the local waters through the morning hours. Although a ridge
pattern aloft will continue to suppress deep convection, isolated
thunderstorms should not be ruled out across the northwest quadrant
of Puerto Rico and downwind from the U.S. Virgin Islands and El
Yunque during the afternoon hours. Under a southeast wind flow, the
coastal areas will observe heat indices between 102 and 107 degree
Fahrenheit this afternoon.

Somewhat drier conditions are expected tonight with mostly clear to
partly cloudy skies and limited shower activity. However, the
advection of a patch of moisture and low level convergence will
result in a few passing showers across the U.S. Virgin Islands and
the north and east sections of Puerto Rico.

Another weak tropical wave will bring additional moisture Saturday
afternoon into early Sunday morning. Therefore, locally induced
showers and thunderstorms will be possible, particularly during the
afternoon hours. After the aforementioned wave, a drying trend will
begins as a dense Saharan air mass is forecast to arrive and persist
through the early part of the upcoming week.

&&

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

Monday, a dry Saharan air mass will hold across the region resulting
in hazy skies. This air mass will inhibit the development of
widespread showers during the afternoon on Monday. However,
isolated to scattered showers are possible during the afternoon as a
result of diurnal and local effects. The strongest showers are forecast
to develop over the interior and western areas of Puerto Rico.
Additionally, an isolated thunderstorms can not be ruled out
across the interior and western areas of Puerto Rico. develop.

Tuesday, model guidance continues to show the 700 mb high shifting
to the southwest of Puerto Rico. The shift in the 700 mb high will
allow tropical moisture to pool into the region from the east.
The return of the deep tropical moisture will cause the dry
Saharan air to diminish over the region. The tropical moisture
will aid in the development of showers and isolated thunderstorms
during the afternoons through Thursday especially over and south
of the Cordillera Central.

Friday, a week tropical wave is expected to move near Puerto Rico
and induce numerous to widespread showers and isolated
thunderstorms. This activity could cause urban and small stream
flooding and mudslides in steep terrain. Then on Saturday a stronger
tropical wave will enter into the region from the east this wave
will also induce moderate to heavy rainfall across most of the
island, which could cause urban and small stream flooding.

&&

.AVIATION...

Mainly VFR conditions with a few passing showers at
times. E-PR/USVI/Leeward Islands terminals can expect brief VCSH
with a few SHRA moving across the terminals but without significant
impact. TJPS can expect SHRA between 23/09-11z, briefly lowering VIS
around 5 SM. TSRA/SHRA will remain possible at TJBQ/TJSJ/TJMZ
between 23/16-22z. Winds will continue calm to light and vrb, but
gusty in SHRA. Winds will return from the E/ESE at 10 to 15 knots
with higher gusts and sea breeze variations after 23/13Z.

&&

.MARINE...

Choppy seas up to 6 feet is expected across the Atlantic waters
today. Due to seas up to 6 feet small craft operators are urged to
exercise caution. Elsewhere, seas up to 5 feet today. Easterly
winds will prevail today ranging from 10 to 20 kts. There is a
moderate risk of rip current for most of Puerto Rico beaches
except the western and eastern beaches of the Island. In addition,
a moderate risk of rip currents for the southern beaches of
Vieques and the northeastern beaches of Culebra. Also, there is a
moderate risk of rip currents for the northern and northeast
beaches of the U.S. Virgin Islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 91 78 90 79 / 30 50 50 50
STT 91 80 88 80 / 20 50 40 40

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
551 AM AST Sat Aug 24 2019

.SYNOPSIS...
A weak tropical wave will increase moisture and instability across
the local islands through at least early Sunday morning. A dry air
mass with a dense Saharan air layer will limit shower activity and
create hazy skies by Sunday morning into early next week.
Unsettled weather conditions will return by mid-week of the
upcoming week.

&&

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

GOES-16 IR shows a shallow patch of moisture moving across the
Leeward Islands. This moisture is associated with a weak tropical
wave that has moved into the Northeast Caribbean waters early this
morning, this wave will move across the region through early
Sunday morning. This tropical wave will produce isolated to
scattered showers this morning across the U.S. Virgin Islands and
eastern areas of Puerto Rico. Most of these showers, however, should be
brief and only lead to minor rainfall accumulations. Later this
afternoon the moisture is expected to continue to advance to the
west. The combination of low-level moisture, local effects and
diurnal heating will initiate showers and isolated thunderstorms
across the interior, western and metro areas of Puerto Rico.

In addition, 00Z high-res WRF model develops streamers downwind of
the U.S. Virgin Islands and across metro areas of San Juan this
afternoon. Streamers that do develop could cause urban and small
stream flooding especially if they develop over San Juan metro areas.

Sunday, moisture will linger across the area and induce isolated to
scattered showers across most of the region. Then a dry Saharan air
mass is forecast to advance into the U.S. Virgin Islands and eastern
Puerto Rico late in the afternoon. This dense air layer will limit
shower activity across the aformentioned areas late Sunday
afternoon. The Saharan air will continue to progress to the west
across other areas of the island by Sunday evening resulting in hazy
skies and limited shower activity late Sunday evening into Monday
night.

.LONG TERM...Tuesday through Friday...
For Tuesday, the aforementioned Saharan Air Layer is forecast to
exit the region by late Tuesday night into early Wednesday
morning. Therefore, hazy skies with limited shower activity will
persist.

Model guidance are suggesting unsettled weather conditions
associated with a low-pressure system Wednesday through early
Friday morning. At this time, the National Hurricane Center (NHC)
is monitoring this system, which is located about a thousand
miles east of the Windward Islands. Environmental conditions
appear conducive for additional development and the NHC is giving
a medium chance of formation in the next 48 hours and a high
chance through the next 5 days. There is plenty of uncertainty
regarding the intensity of this disturbance, but giving the
potential for development into a more organize system, we will
continue monitoring this situation. A more seasonable weather
pattern is forecast to return by Saturday.

&&

.AVIATION...
Mainly VFR conditions are expected to persist through the forecast
period. VCSH expected across eastern PR, USVI and Leeward Island
terminals through 24/18Z. SHRA/TSRA across metro areas of PR and
western terminals of PR by 24/16Z, then over terminals TJBQ and
TJMZ by 24/18Z. SHRA/TSRA could cause brief MVFR conds. Winds will
be out of the East to southeast at 10 to 20 kts with higher gusts
and sea breeze variation starting by 24/14Z.

&&

.MARINE...Seas up to 5 feet and winds around 15 knots are
expected across the local waters through much of the forecast
period. If marine guidances are correct, an active tropical wave
will deteriorate the marine weather conditions by mid-week of the
upcoming week.

For the beach goers, there is a moderate risk of rip current for
most of the local beaches of Puerto Rico and the U.S. Virgin
Islands today.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 79 91 80 / 50 50 20 20
STT 90 81 89 80 / 40 40 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
531 AM AST Tue Aug 27 2019

.SYNOPSIS...
A Tropical Storm Warning and Hurricane Watch is in effect for
mainland Puerto Rico, the Caribbean Waters and Mona Passage. Based
on the latest forecast track, tropical storm force winds are
expected to start affecting the Caribbean waters as early as late
tonight or early Wednesday morning and continue across the
southern waters of Puerto Rico through late Wednesday night.

&&

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

A TROPICAL STORM WARNING AND HURRICANE WATCH IS IN EFFECT FOR
MAINLAND PUERTO RICO, THE CARIBBEAN WATERS AND MONA PASSAGE.

Fair weather conditions with Saharan dust particles are expected
to continue across the islands through the morning into the
afternoon hours. Warm temperature are expected today with heat
indices in the low and mid 100 degree Fahrenheit. Some showers may
develop in western Puerto Rico due to local effects, diurnal
heating and sea breeze variations.

Dorian located about 490 miles southeast of San Juan and about 400
miles off to the southeast of St Croix will continue to move
west-northwest today. As Tropical Storm Dorian moves close to the
islands moisture will slowly increase late Tonight into early
Wednesday morning. Therefore, the outer rain bands of Dorian
could bring periods of showers and gusty winds across the U.S.
Virgin Islands and eastern Puerto Rico as early as late tonight
or Wednesday morning. Tropical storm force winds will likely
affect the southern and western sections of mainland Puerto Rico.
The main threat associated with Dorian is flooding rains,
especially across the south and western sections where rainfall
accumulations will range between 2 and 4 inches with isolated
higher amounts up to 6 inches. Squally weather is expected for the
U.S. Virgin Islands, Vieques and Culebra, which could result in
periods of moderate to heavy rain and gusty winds. Given that
Tropical Storm Dorian is a small system, any change in the
forecast track could affect the impacts across Puerto Rico and the
U.S. Virgin Islands.

Dorian is forecast to move into the eastern Dominican Republic
late Wednesday night or early Thursday morning leaving behind
plenty of tropical moisture over Puerto Rico and the U.S. VIrgin
Islands. Therefore, residents in these islands should monitor the
progress of Dorian because an event with heavy rains would be
possible through the short term period.

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

At upper levels, a TUTT low to the northeast of PR/USVI will move
over the Bahamas, while another TUTT-low will sink over the
northeast Caribbean by Friday. The second TUTT-Low will then move
westward leaving the islands in the subsidence side of this system
through at least Saturday. At the surface, another tropical wave
is expected to move across the islands Sunday into Monday. The
aforementioned TUTT-Low is forecast to enhance the tropical wave
increasing the potential for shower and thunderstorm formation
Sunday and Monday.

&&

.AVIATION...
VFR conditions are expected to continue across the terminals of
PR & USVI. Haze due to Saharan dust will continue through at least
tonight. Then, moisture is forecast to increase around 27/20z
across the Leeward Islands, therefore, TNCM/TKPK could expect SCT-
BKN ceilings between FL018-FL025. The outer bands of Dorian could
bring periods with heavy rain and gusty winds at PR/USVI after
27/00z. SFC winds calm to light and VRB becoming from the E-NE at
10 to 15 kts with sea breeze variations/higher gusts aft 27/22Z.

&&

.MARINE...
Seas up to 5 feet are expected to continue until this afternoon.
A Tropical Storm Warning and Hurricane Watch is in effect for the
Caribbean Waters and the Mona Passage. Marine conditions are
expected to slowly deteriorate as early as this evening with
winds of 55 to 65 gusting up to 90 kts across the local waters.
Seas could reach 18 to 20 feet with occasional seas up to 25 feet.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 79 86 76 / 20 60 80 70
STT 90 80 85 79 / 40 70 80 60

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
430 AM AST Thu Aug 29 2019

.SYNOPSIS...Dorian`s tail and associated lingering moisture is
expected to affect the local islands today. As a result, a Flash
Flood Watch remains in effect through 8 PM AST this evening. As
Dorian continues to move away, relatively stable weather
conditions with the potential for locally induced activity is
expected on Friday and Saturday. The next tropical wave, enhanced
by a TUTT low, will affect the area on Sunday and Monday. Although
somewhat drier air is expected to filter the area on Tuesday and
Wednesday, locally induced convection cannot be ruled each
afternoon out as patches of low- level moisture move across the
area from time-to-time.


&&

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

An outer band of Hurricane Dorian has affected the local area,
particularly the local waters, USVI, and the islands of Vieques and
Culebra. Some light to moderate showers affected portions of southern
and eastern PR as well, although the rainfall accumulations were
modest. Based on the forecast track of Dorian, the southerly flow
with deep moisture that is expected today could bring additional
showers and thunderstorms to the local area, so a somewhat active
day could occur today. The southerly wind flow may combine with the
local effects and cause an area of higher shower activity across
northern PR in the afternoon hours. However, as the hurricane moves
away so will the shower activity. Mostly fair weather is expected
for late tonight into Friday morning, then showers and thunderstorms
could occur across the northwestern sections of PR on Friday
afternoon due to local effects. A similar situation is expected for
Saturday, but with a more easterly wind, the shower and
thunderstorm activity is expected across western PR. With the
southerly wind flow, the high temps across northern PR today could
be in the low 90s, but the south coast would be in the upper 80s.

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

A surface high pressure will maintain a moderate east to
southeast wind flow across the region. A tropical wave and
associated plume of moisture is expected to affect the forecast
area on Sunday through Monday. A westward moving TUTT low will
enhance the effects of this wave, increasing the potential for
shower and thunderstorm development during this period. Apart
from this, patches of low-level moisture are expected to cross the
forecast area from time- to- time, enhancing overnight and early
morning showers over eastern Puerto Rico, followed by locally
induced convection each afternoon. The next patch of drier air
accompanied by Saharan dust is expected to arrive by Tuesday and
infiltrate the area through at least Wednesday. However, there is
medium confidence in the timing of the arrival of drier air since
models consensus calls for a wet pattern to dominate through most
of the long-term forecast period.


&&

.AVIATION...Prevailing VFR conds expected across the local terminals,
with mainly VCSH/VCTS, occasional SHRA/TSRA at the terminals. Winds
will be mainly light and variable, but the mean wind flow will be
southwesterly early in the morning, then southerly during the day as
hurricane Dorian moves away from the local area. CIGS will also
improve through the forecast period, by 29/12Z across western PR,
gradually improving with the eastern terminals, TIST and TISX
improving CIGS by 29/23Z.


&&

.MARINE...As Dorian continues to move northwestward and away from
the area, seas are expected to gradually diminish today. However,
Small Craft Advisory conditions will continue across the Atlantic
waters through at least early this morning. Moderate to fresh
winds are expected in the morning across the Atlantic waters, but
light to moderate winds are expected elsewhere today. Showers and
thunderstorms are expected across the local waters today as outer
bands of Hurricane Dorian continue to affect the local waters.

A moderate risk of rip currents is in effect for beaches along the
northwest to northeast and southeast coast of Puerto Rico, as well
as most beaches in Vieques and Culebra. A moderate risk is also in
place for Neltjeberg beach in Saint Thomas.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 78 90 78 / 60 20 30 30
STT 85 80 88 79 / 60 20 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
447 AM AST Fri Aug 30 2019

.SYNOPSIS...Relatively fair and stable weather conditions with
the potential for locally induced activity is expected on today
and Saturday. The next tropical wave, enhanced by a TUTT low, will
affect the area on Sunday with lingering moisture affecting the
local weather conditions on Monday. Although somewhat drier air
accompanied by suspended Saharan dust is expected to filter the
area by midweek, locally induced convection cannot be ruled each
afternoon out as patches of low- level moisture move across the
area from time-to- time.


&&

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

Hurricane Dorian has moved away from the local area, but the
southeasterly wind flow influenced by the hurricane will continue
through most of today. Moisture associated with the hurricane will
also linger through today. For that reason, isolated to scattered
showers are expected early in the morning across the local waters,
USVI, as well as the coastal areas of eastern and southern PR. By
the afternoon hours, the combination of the lingering moisture,
diurnal heating and local effects will cause the development of
showers and thunderstorms across the northwestern quadrant of PR as
well as the possibility of a line of showers and isolated
thunderstorms affecting portions downwind from the Luquillo Mountain
range into the San Juan metro area. Mostly fair weather is expected
elsewhere this afternoon. The high temperatures will be in the low
90s today across the lower elevations of PR and the USVI, apparent
temps may reach the low 100s.

For Saturday and Sunday a much more typical weather pattern returns
with easterly winds but slightly higher than normal moisture. This
is due to a weak tropical wave moving in on Sunday. Because of that
the forecast is for isolated to scattered and brief showers in the
nighttime and early morning hours across the local waters, USVI, and
eastern PR, but showers and thunderstorms are expected across
western PR in the afternoon hours due to local effects. That said,
there is an upper low expected over the local area, which could
enhance the duration and intensity of the thunderstorms expected
over central and western PR on Sunday afternoon. Temps will be near
normal also with highs in the upper 80s to low 90s.

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

A surface high pressure will maintain a moderate east to
southeast wind flow across the region. Lingering moisture from a
departing tropical wave is expected to affect the forecast area
on Monday. Apart from this event, model guidance continues to
suggest that mainly fair and stable weather conditions will
dominate the region Tuesday through Thursday. Shower activity
across the local islands will be strictly the result of patches
of low-level moisture moving across the forecast area from time-
to- time. This activity will be in the form of overnight and early
morning passing showers, followed by locally induced convection
each afternoon. The next patch of suspended Saharan dust is
expected to arrive by Tuesday and infiltrate the area through at
least Wednesday.


&&

.AVIATION...Today through Sunday...
Hurricane Dorian has moved away from the local area, but the
southeasterly wind flow influenced by the hurricane will continue
through most of today. Moisture associated with the hurricane will
also linger through today. For that reason, isolated to scattered
showers are expected early in the morning across the local waters,
USVI, as well as the coastal areas of eastern and southern PR. By
the afternoon hours, the combination of the lingering moisture,
diurnal heating and local effects will cause the development of
showers and thunderstorms across the northwestern quadrant of PR as
well as the possibility of a line of showers and isolated
thunderstorms affecting portions downwind from the Luquillo Mountain
range into the San Juan metro area. Mostly fair weather is expected
elsewhere this afternoon. The high temperatures will be in the low
90s today across the lower elevations of PR and the USVI, apparent
temps may reach the low 100s.

For Saturday and Sunday a much more typical weather pattern returns
with easterly winds but slightly higher than normal moisture. This
is due to a weak tropical wave moving in on Sunday. Because of that
the forecast is for isolated to scattered and brief showers in the
nighttime and early morning hours across the local waters, USVI, and
eastern PR, but showers and thunderstorms are expected across
western PR in the afternoon hours due to local effects. That said,
there is an upper low expected over the local area, which could
enhance the duration and intensity of the thunderstorms expected
over central and western PR on Sunday afternoon. Temps will be near
normal also with highs in the upper 80s to low 90s.


&&

.MARINE...Tranquil marine conditions with seas at or below 5 feet
and light to moderate east to southeast winds are expected during
the next few days. A tropical wave will enter the Caribbean by
Saturday evening and move across the local islands on Sunday into
Monday, increasing the potential for shower and thunderstorm
activity across the local waters.

A moderate risk of rip currents is in effect for most beaches
along the north coast of Puerto Rico, as well as Culebrita beach
in Culebra.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 78 89 79 / 30 10 20 40
STT 87 79 89 78 / 30 20 20 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
423 AM AST Sun Sep 1 2019

.SYNOPSIS...
A seasonal pattern with early trade wind showers and afternoon
convection across western Puerto Rico is expected today. Moisture
associated with a tropical wave will approach the islands on
Monday, resulting in an increase in showers across the region. In
the long- term, no major weather systems are expected to affect
the local area through the end of the workweek.

&&

.SHORT TERM...Today through Tuesday
Passing low level trade wind clouds with embedded showers continued
to cross the region overnight while brushing the coastal areas of
some of the islands from time to time. Rainfall was mainly of light
to moderate intensity and of short duration. Expect this pattern to
continue through the early morning hours followed by gradual
clearing and mostly sunny skies. For the the rest of the day,
available moisture along with daytime heating and local effects will
favor showers and isolated thunderstorms mainly over the central and
west sections of Puerto Rico. Some of the afternoon convection over
Puerto Rico may again lead to minor urban and small stream flooding.
Only isolated afternoon showers will be possible in and around the
U.S. Virgin islands today as mostly fair weather skies should
prevail.

Surface high pressure ridge across the north central Atlantic will
lift slightly northward through Monday as an induced low level
trough/weak tropical wave crosses the northeast Caribbean. This will
be in tandem with a mid to upper level inverted trough forecast to
also move across the forecast area. The low level pattern will
maintain a fairly weak pressure gradient and light easterly trades
resulting in local sea breeze variations. Winds are to become more
east southeast Monday and Tuesday as the trough and tropical wave
exits the region and high pressure ridge reestablishes north of the
area.

Monday through early Tuesday, moisture trailing the weak tropical
wave and low to mid level trough will be sufficient to support the
development and enhancement of early morning and afternoon shower
activity each day. The heaviest expected rainfall however would be
during the afternoon hours and should be focused mainly over parts
of the central interior and west to northwest sections of Puerto
Rico. Elsewhere including the U.S. Virgin Islands mostly fair
weather skies should prevail. No significant weather feature is
forecast during the rest of the period as an overall seasonal
weather pattern expected to prevail.

.LONG TERM...Wednesday through Sunday...
No major weather system are anticipated for the second half of
the workweek. Patches of moisture embedded in the trade winds will
continue to transport showers across the local islands.
Therefore, expect showers early in the day across the eastern half
of Puerto Rico and the U.S. Virgin Islands. Then, due to the
combination of the available moisture and local effects, showers
and thunderstorms will be possible over the western half of Puerto
Rico each afternoon. For the upcoming weekend, an upper level low
will be positioned just to the northeast of the eastern
Caribbean. In addition, moisture is expected to increase as a
tropical wave moves north of the area, hence, there will be a
better potential for rain across the forecast area.


&&

.AVIATION...VFR conds during fcst prd. SHRA ovr regional waters and
en route btw islands. SCT ocnl BKN lyrs nr FL022...FL050...FL250.
Few tops nr FL080. Sfc winds lgt/vrb bcmg 10-15 knots from the ESE
with sea breeze variations and hir gusts aft 01/14z. Aftn SHRA/Isold
TSRA ovr ctrl and W PR fm 01/17Z-01/22Z with VCSH at most terminals.
VCTS at TJBQ/TJMZ 01/17Z-01/22Z. No sig operational wx impacts
attm.


&&

.MARINE...
Tranquil marine conditions will continue today with seas at or
below 4 feet and winds out of the east southeast at 5 to 15 knots.
A weak tropical wave could bring showers to the local area later
today through Monday. The risk of rip currents is moderate for
some of the beaches along northern Puerto Rico.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 90 79 / 30 30 40 40
STT 88 79 88 81 / 30 30 50 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
505 AM AST Mon Sep 2 2019

.SYNOPSIS....
Surface high pressure ridge north of the area and a weak tropical wave
with axis now crossing Puerto Rico, will promote a light southeast
wind flow across the region. Quick passing early morning showers with
areas of locally heavy rains will affect portions of the local waters
with the passage of the tropical wave. Additional shower development
with isolated thunderstorms will be possible mainly over the northwest
sections of Puerto Rico during the afternoon. A drier airmass will
follow later this evening through Tuesday except for few early morning
showers followed by locally and diurnally induced afternoon convection.
No major features is forecast to approach the area during the period.

&&

.SHORT TERM....Today through Wednesday...
Passing showers continued to move across the eastern half of Puerto
Rico and the U.S. Virgin Islands in association with a weak tropical
wave that is moving across the area today. Therefore, expect passing
showers early in the day on the eastern side of the forecast area.
In the afternoon, due to the available moisture and the diurnal
heating, showers and thunderstorms will develop across the interior
and northwestern Puerto Rico. As the tropical wave leaves the region
later in the day , GOES Total Precipitable Water derived product
shows a patch of a drier air over the Lesser Antilles that will
begin to enter the area in the afternoon. In addition, the latest
NASA GMAO and the NAAPS models show some Saharan dust embedded with
this air mass.

On Tuesday, a narrow band of moisture will cross the islands,
increasing the chance of showers during the day, although moisture
will be mainly restricted to the lowest 850 mb. Drier air along with
Saharan dust will return afterward, with the latest GFS sounding
showing precipitable water values dropping to near 1.10 during the
evening hours. On Wednesday,a seasonal pattern should hold on across
the area with a few shallow patches of moisture moving across the
area and afternoon convection developing across western Puerto Rico.

.LONG TERM...Thursday through Sunday...
A slight increase in the easterly trade winds will return by
Thursday as the surface high pressure ridge is to reestablish just
north of the area and a drier airmass and surge of saharan dust
will move across the region. However, shallow patches of low
level moisture will continue to affect the region from time to
time. This will bring periods of passing early morning showers
followed by locally and diurnally induced afternoon convection
through the rest of the work week. Increasing tropical moisture
and upper level instability is expected by Saturday and Sunday as
a Tutt low and tropical wave is forecast interact and cross the
region. By then recent model guidance suggests layered precipitable
water values to increase to around or just below 2 inches. That
said, expect a better support and chance for overall showers and
isolated thunderstorm development over the following weekend
especially on Sunday with potential for urban and small stream
flooding in isolated areas.

&&

.AVIATION...Mainly VFR conditions are expected to continue through
the forecast period. VCTS are expected after 02/17Z for TJMZ/TJBQ
with possible TEMPO that could reduce VIS to MVFR or IFR conditions.
The 02/00Z GFS sounding shows mostly light winds, coming out of the
east-southeast at less than 10 knots at FL050.

&&

.MARINE...Seas are forecast to remain tranquil at 5 feet or less
for the next several days. Quick passing showers with areas of
locally heavy rains will affect portions of the coastal waters
during the passage of the tropical wave today. Isolated thunderstorms
will be possible mainly over the northwest coastal waters of Puerto
Rico during the afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 79 91 79 / 20 20 30 30
STT 88 80 89 81 / 30 20 30 30

[cycloneye]

AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
426 AM AST Tue Sep 3 2019

.SYNOPSIS...An overall drier air mass continued to filter in
from the east during the early morning hours, except for a few
passing showers which brushed parts of the islands from time to
time. Another patch of moisture accompanying a wind surge will
cross the region later today and during the evening hours. This
increase in moisture along with diurnal heating and local effects
will favor showers and thunderstorm development mainly across the
interior and western sections of Puerto Rico. A low to moderate
concentration of Saharan dust will quickly follow the moisture
surge later today through Wednesday. This will also support an
overall hot and hazy conditions with heat indices expected to
range between 100 to 107 in some areas.

&&

.SHORT TERM...Today through Thursday...
Mainly fair weather prevailed across the region through the night
hours. A few showers were observed across the region, but with little
accumulation detected by the Doppler radar. For the rest of the day,
a narrow band of moisture will move across the islands today. This
feature shows precipitable waters values near 2.0 inches according
to GOES Total Precipitable Water derived product. This should result
in a few showers across the U.S Virgin Islands and eastern Puerto
Rico early in the day, followed by afternoon convection across the
interior and western Puerto Rico. Stream-like showers will be
possible across the San Juan metro area and downwind from the isles.
Drier air will reach the forecast area afterward, with precipitable
water values dropping to near 1.10 inches according to the latest
GFS sounding and also in the GOES Precipitable Water product. The
NAAPS model shows that moderate concentration of Saharan dust will
be embedded with this drier air mass. After the passage of this area
of moisture, the pressure gradient will tighten a little, resulting
in a slight increase in winds across the region until early
Thursday.

For Wednesday and Thursday, patches of low level moisture will move
from time to time across the area, bringing passing showers across
the eastern half of the area of responsibility. In the afternoon,
showers and thunderstorms should develop across western Puerto Rico
due to a combination of available moisture and local effects.

.LONG TERM...Friday through Wednesday...
Increasing trade wind moisture expected across the area Thursday
through Friday with low level wind flow becoming more east northeast
ahead of a weak easterly disturbance. This feature will increase
the chance for early morning showers mainly along the north and
east coastal areas. This will be followed by afternoon convection
over parts of the central and west sections of Puerto Rico.
Moisture advection gradually increases through the weekend. The
most favorable and unstable conditions are expected by Sunday and
into early next week as a Tutt low is forecast to relocated just
northeast of the region along with a tropical wave which is
expected to move across the forecast area.

In the mid to upper levels, the high pressure is to drift westward,
allowing the TUTT low to relocate just northeast of the area. Recent
model guidance has been persistent and have so far initialized fairly
well with the ongoing conditions and expected weather pattern. Although
no significant weather feature is forecast during the period, a somewhat
wetter pattern is still expected by Sunday and into early next week
due to the interaction of the Tutt low and approaching tropical
wave. Therefore enhanced early morning and afternoon convection
will be possible through Tuesday with improving conditions and
lesser shower activity expected by Wednesday.

&&

.AVIATION...VFR conditions are expected to prevail through most of
the forecast period. VCTS are expected for TJMZ/TJBQ after 03/16Z.
This could result in TEMPO conditions with VIS reduced to MVFR or
IFR. The 03/00Z sounding showed FL050 winds out of the east
southeast at 8 knots or less. However, winds are expected to pick up
a bit after 03/12Z with winds out of the east at 10 to 15 knots.

&&

.MARINE...Seas are forecast to remain at 5 feet or less, with a light
to moderate wind chop mainly over the Atlantic waters and local passages.
Isolated thunderstorms will be possible across coastal waters of western
and northwestern Puerto Rico during the afternoon hours.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 90 79 90 79 / 40 20 30 30
STT 89 80 90 79 / 30 30 20 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
503 AM AST Wed Sep 4 2019

.SYNOPSIS...Surface high pressure ridge will remain place north
of the region through the end of the work week. A mid to upper
level ridge will build and hold across the area into the weekend.
Light to moderate easterlies will prevail with an overall drying
trend expected through as least Thursday. Another weak easterly
perturbation will bring a slight increase in low level moisture to
the area by Friday. A low concentration of Saharan dust will
persist across the region today but will continue to diminish
during the afternoon and evening hours. Locally and diurnally
induced afternoon showers with possibly isolated thunderstorm
development should be focused mainly over parts of the central
interior and west sections of Puerto Rico, but will be steered by
the prevailing winds.

&&

.SHORT TERM...Today through Friday...
A few light passing showers were observed across portions of eastern
Puerto Rico and the U.S. Virgin Islands. A drier air mass along with
some Saharan dust will continue to move across the region through
the early part of the day. However, patches of moisture embedded in
the trade winds will also move through, resulting in passing showers
early in the day for the eastern half of the forecast area. Then, in
the afternoon, showers and thunderstorms should develop along the
interior and western Puerto Rico. Stream-like showers will be possible
as well along the San Juan metro area and downwind from the isles.

On Wednesday evening through Thursday, as a high pressure at all
levels builds north of the region, winds will shift from the
northeast. Once again, patches of moisture are expected to filter in
with the focus of the strongest afternoon convection along
southwestern Puerto Rico. In addition, northeast winds will bring a
slight relief in heat indices along coastal sections, with values
staying just below the 100 degree mark. For the end of the
workweek, moisture associated with a tropical disturbance will
begin to work its way into the region, increasing the potential
for shower and thunderstorm activity

.LONG TERM...Saturday through Thursday...
Increasing trade wind moisture is expected across the area
through Saturday with low level wind flow becoming more east
northeast ahead of a weak easterly disturbance. This feature will
increase the chance for early morning showers mainly along the
north and east coastal areas. This will be followed by afternoon
convection over parts of the central and west sections of Puerto
Rico. Moisture advection gradually increases as this feature
crosses the area through the weekend. However, the most favorable
and unstable conditions are expected late Sunday and into early
next week as a Tutt low is forecast to shift westward toward the
area along with a tropical wave which is expected to move across
the forecast area.

In the mid to upper levels, high pressure is to shift westward,
allowing the aforementioned TUTT low to relocate just northeast
of the area late Sunday through Monday. Recent guidance continue
to initialized fairly well with the ongoing and expected weather
conditions. Although no significant weather feature is forecast
during the period, a somewhat wetter pattern is still expected by
late Sunday and into early next week due to the interaction of
the Tutt low and approaching tropical wave. Enhanced early morning
and afternoon convection can therefore be expected Monday through
Tuesday with improving conditions and lesser shower activity forecast
for Wednesday and Thursday.

&&

.AVIATION...Mainly VFR conditions are expected to continue across
all terminals through the forecast period. VCTS are expected for
TJMZ after 04/17Z. These thunderstorms could result in TEMPO with
MVFR or IFR conditions. GFS 04/00Z soundings shows FL050 winds out
of the east to east-southeast at 10 to 20 knots.


&&

.MARINE...Seas up to 5 feet and winds up to 15 knots are expected
through today. There is a moderate risk of rip currents for a few
northwestern beaches of Puerto Rico, eastern St Croix and eastern
Vieques, with an overall low risk elsewhere.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 80 89 79 / 40 30 30 40
STT 91 80 90 79 / 30 30 30 40

[cycloneye]

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
500 AM AST Thu Sep 5 2019

.SYNOPSIS...Trade wind moisture will be on the increase today and
Friday, resulting passing showers across eastern Puerto Rico and the
USVI during the overnight and morning hours followed by showers and
thunderstorms across interior and western Puerto Rico during the
afternoon hours. More enhanced rainfall activity is possible during
the weekend into early next week as a result deeper moisture and
an upper-level low near the area. Improving weather conditions
expected by the middle and latter half of next week.

&&

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

Many popcorn showers over the local waters moving in the northeast
to east northeast flow were seen as a moisture band moves east
across the area ahead of a tropical wave moving through late
Thursday and during the day Friday. Some showers came onshore in
northern Puerto Rico and the U.S. Virgin Islands with minor
accumulations. This northeast flow will allow showers to form from
El Yunque to Cabo Rojo later today with some thunderstorms possible,
but warmer 500 mb temperatures today and Friday will keep activity
relatively constrained. Moisture will increase rapidly today and
tonight, however, and this will increase the amount and intensity
of the showers that form during the afternoons and overnight
tonight and Friday. Also moisture at 700 mb is increased overnight
tonight so showers over eastern Puerto Rico and to a lesser
extent the U.S. Virgin Islands will be more abundant tonight than
they have been Wednesday night and early Thursday morning. After
this afternoon precipitable water values remain above 1.85 through
Saturday and the GFS suggests values over 2.1 inches Friday and
over the weekend.

On Saturday, a col at 700 mb moves over the area and winds will
begin to diminish. Moisture also invades the area from the south
to set up later rains.

At upper levels, high pressure over the area will rotate toward Cuba
while a TUTT northeast of the area will extend into the Windward
Islands by Saturday. Upper level divergence will also favor
convection Friday and Saturday as the wave moves through the area.

Urban and small stream flooding will be come more likely Friday and
Saturday in Puerto Rico as moisture increases and upper levels
become more favorable. Surface winds that would move them out of
the area and keep them from forming mainly in the interior portions
of the island will also diminish.

.LONG TERM...Sunday through Friday...

An upper-level low is expected to be located near the area Sunday
through early next week. This will aid in enhancing the instability
aloft. At lower-levels, a trough will slowly move westward across
the area. The combination of these features along with deeper
moisture, with precipitable water values between 2.0 and 2.1
inches, is expected to result in enhanced shower and thunderstorm
activity during the afternoon hours mainly across mainland Puerto
Rico. This low-level trough is also expected to result in a very
light steering flow with the latest forecast soundings from both
the GFS and ECMWF models indicating less than 5 knots. As a
result, the showers that develop are expected to be very slow-
movers and develop across interior Puerto Rico and spread slowly
northward. Given the very slow movement expected with these
showers, urban and small stream flooding is likely to materialize.
Weather conditions are expected to improve by the middle to
latter half of next week as a drier air mass moves overhead.

&&

.AVIATION...VFR conditions are expected to continue across all
terminals through the forecast period. SHRA/TSRA are expected to
dvlp from El Yunque to Cabo Rojo to yield VCTS for TJMZ and TJPS
after 05/17Z with MVFR conds psbl. Areas of mtn obscurations aft
05/16Z. Sfc winds 10 kt or less bcmg aft 05/14Z 12-18 kt with hir
gusts and sea breeze influences alg the coasts. Max winds E 25-30 kt
btwn FL380-450.

&&

.MARINE...Mainly tranquil marine conditions will continue to
prevail with seas less than 5 feet and winds between 10 and 15
knots expected. There is a moderate risk of rip currents for some
of the northern beaches of Puerto Rico and Saint Croix as well as
for Culebrita Beach in Culebra. Elsewhere, the rip current risk is
expected to be low.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 89 79 / 60 60 40 50
STT 90 79 89 78 / 50 50 40 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
511 AM AST Fri Sep 6 2019

.SYNOPSIS...Moisture will be on the increase today and through the
upcoming weekend, resulting in an increase in the coverage and
intensity of showers and thunderstorms across the area, especially
across Mainland Puerto Rico, during the afternoon hours. A
retrogressing upper-level low along with a low to mid-level trough
will aid in enhancing the rainfall activity through early next
week. Improving weather conditions are expected by the middle to
latter portion of next week.

&&

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

Many small showers over the local waters with tops 15-30 kft are now
moving in the east southeast flow as a weak trough passes through
the area. This flow is expected to become more easterly during the
day as the next trough approaches. Mid level temperatures cool
somewhat today and we will have a few more thunderstorms over
western Puerto Rico this afternoon. The next trough is weak and
winds become very weak at lower levels during the day on Saturday
when this trough passes through the forecast area. Mid level
temperatures decrease another degree on Saturday and the weak winds
will allow sea breezes and local effects to dominate, forcing most
of the convection to the north half of Puerto Rico during the
afternoon. Moisture will also peak late in the afternoon to fuel
more vigorous showers and thunderstorms. The threat of urban and
small stream flooding will become more extensive on Saturday.

An area of moisture at 850 and 700 mb, now over Venezuela will move
toward Puerto Rico and the U.S. Virgin Islands during the period on
flow around a high pressure centered over the Windward Islands, but
because a weak low splits off the trough passing through on
Saturday, the moisture is delayed until late Sunday. Also in the 850-
700 mb level, a dry slot can be seen ahead of the moisture. It moves
into the forecast area on Saturday and over Puerto Rico and the U.S.
Virgin Islands late Saturday night and early Sunday.

At upper levels the high pressure, north of the area, is moving
west, and northeast flow over the forecast area will increase to 35
knots during the day. Divergence aloft is forecast by the GFS to be
present but weak today. On Saturday it shows better and more
organized divergence mainly over central and western Puerto Rico
during the afternoon to enhance convection. Winds at upper levels
weaken on Sunday and divergence is not well signaled.

To recap, urban and small stream flooding will be come more likely
today and even more so on Saturday in Puerto Rico as moisture
increases and upper levels become more favorable. Surface winds
that would move the showers and thunderstorms out of the area where
they form will also diminish on Saturday. These slow moving storms
will cause rainfall amounts to increase over western and interior
Puerto Rico, and mainly north of the Cordillera Central.

.LONG TERM...Monday through Saturday...

A low-level trough will remain near the area Monday and Tuesday
of next week. A trough will also be present in the mid to upper-
levels, with the axis near the area. These features along with
abundant moisture, with precipitable water values around 2.00
inches, will continue to result in enhanced shower and
thunderstorm activity, mainly across Mainland Puerto Rico, during
the afternoon hours. Given that the steering flow is expected to
remain below 5 knots, the activity that develops will be very slow
moving. Therefore, urban and small stream flooding will continue
to remain an issue. Across the USVI, at this time, only some
isolated to scattered shower activity is expected with no
significant rainfall accumulations expected. Weather conditions
will improve during the middle to latter portion of next week as a
drier air mass moves overhead and the trough pattern breaks down.

&&

.AVIATION...Brief MVFR Conds psbl at TKPK, othw VFR conditions are
expected to continue across all terminals til 06/16Z. SHRA/TSRA are
expected to dvlp ovr wrn and interior PR and SHRA WNW from the USVI.
VCTS for TJMZ, TJBQ and TJPS after 06/16Z with MVFR conds psbl.
Areas of mtn obscurations aft 06/16Z. Sfc winds 10 kt or less bcmg
aft 05/14Z 10-15 kt with hir gusts and sea breeze influences alg the
coasts. Max winds ENE 30-40 kt btwn FL350-520.

&&

.MARINE...Marine conditions will continue to remain tranquil with
seas less than 5 feet and winds between 10 to 15 knots expected.
There is a low risk of rip currents across all of the local
beaches for today.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 79 88 78 / 60 50 50 20
STT 89 78 88 79 / 60 50 50 30

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
506 AM AST Sat Sep 7 2019

.SYNOPSIS...An area of deep moisture has become entrenched over
Puerto Rico with lighter than usual wind flow. Heavy rains are
expected today and Sunday then gradually tapering off through
Tuesday. Easterly trade winds will then persist through the rest
of the week next week. This will bring areas of showers in our
usual seasonal pattern until next weekend.

&&

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

An unstable weather pattern is expected today and Sunday across the
area. The combination of deep moisture, with precipitable water
values above 2.00 inches, and a low to mid-level trough will provide
the necessary ingredients for the development of heavy showers and
thunderstorms. The heaviest rainfall activity is expected to be
concentrated across most of interior, western, and the northern half
of Puerto Rico, including the San Juan metro area, from the late
morning through most of the afternoon hours. In addition, the
steering flow is expected to be less than 5 knots. Therefore, the
showers that develop are expected to be very slow movers. Given this
scenario, the potential is high for urban and small stream flooding
to occur as well as rapid river rises and mudslides in areas of
steep terrain. Some areas may also experience flash flooding.
Across the USVI, although some isolated to scattered showers are
possible at times, rainfall accumulations are not expected to be
as significant as it will be across Puerto Rico with average
accumulations of than less than a half an inch expected. Most of
the rainfall activity is expected to dissipate during the early
evening hours, with some brief showers expected during the
overnight period.

The activity on Monday is not expected to be as intense as a dry
slot moves across. However, the axis of the low to mid-level trough
is expected to remain near the area. As a result, another round of
showers and thunderstorms can be expected during the afternoon hours
across portions of interior and northern Puerto Rico. In addition,
given that the steering flow will continue to remain very light,
less than 5 knots, the showers that develop will be slow-movers once
again. Therefore, urban and small stream flooding will be possible.

at upper levels, areas of very good divergence will develop both
Saturday and Sunday afternoons across Puerto Rico and coupled with
cool 500 mb temperatures this will enhance the thunderstorms
across the area. A few thunderstorms were seen in the Mona Passage
earlier this morning.

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

By Tuesday a TUTT low will be found both southwest of Puerto Rico
in the Mona Channel and also 1000 miles northeast of Puerto Rico.
Ridging at the surface and mid levels will and a drier atmosphere
will signal the end of the rainiest period and precipitable water
will dip to as low as 1.5 inches. Moisture will then increase
gradually across the area through Saturday. A weak wave will cross
mainly south of the area Thursday night, followed by another area
of moisture and another wave approaching at the end of the period.

Beyond Saturday of next week, the model still remains uncertain
as to the track of a tropical cyclone early in the following week,
but currently takes it northeast of the forecast area.

&&

.AVIATION...VFR conditions expected through 07/14z. SHRA/TSRA
expected across PR between 07/16z and 07/22z with some tops to
FL500 psbl. The activity is expected to be near the vicinity of
TJSJ/TJMZ/TJBQ, with TEMPO MVFR to IFR conditions possible. Winds
light and variable through 07/12z, increasing to 10 to 15 kts from
the E-ESE with sea breeze variations after 07/14z.

&&

.MARINE...Winds and seas are expected to remain below small craft
advisory levels through at least next Saturday. Showers and
thunderstorms will become more frequent today and Sunday then
taper off Monday through Wednesday.

&&

.HYDROLOGY...Several rivers reached flood stage yesterday, namely
the Culebrinas and the Rio de la Plata at Comerio. These rivers
have subsided below the flood stage but are still running higher
than normal. With deep moisture and good instability, showers and
thunderstorms that develop in light wind flow across the area will
bring excessive rainfall to much of interior Puerto Rico and some
coastal sections. Amounts of 2-5 inches are possible today and
Sunday. therefore a flash flood watch has been issued beginning
today at noon and continuing through Sunday at 6 PM AST.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 78 89 78 / 60 30 60 20
STT 89 79 88 79 / 40 40 30 30

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
502 AM AST Sun Sep 8 2019

...A Flash Flood Watch is in effect Until 8 PM AST tonight for
mainland Puerto Rico...

.SYNOPSIS...An area of deep moisture continues over Puerto Rico
with lighter than usual wind flow. Heavy rains are expected today
and Sunday then gradually tapering off through Tuesday. Easterly
trade winds will then persist through the rest of the week next
week. This will bring areas of showers in our usual seasonal
pattern until next weekend.

&&

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

Another very active weather day is expected across the area. The
combination of deep-layered moisture, with precipitable water values
between 2.0 and 2.2 inches, along with deep troughiness will
provide the necessary ingredients to result in another round of
widespread heavy rainfall activity across Puerto Rico. In
addition, numerous thunderstorms with frequent lightning are
expected as there will be good divergence aloft provided by the
upper-level low just southeast of Puerto Rico along with cool 500
mb temperatures near -7 degrees Celsius. The steering flow is
also expected to remain below 5 knots, therefore, the showers are
expected to be very slow-movers once again. Given that the soils
are saturated due to the heavy rainfall from the last couple of
days and with more additional heavy rainfall activity expected,
urban and small stream flooding as well as rapid river rises and
mudslides in areas of steep terrain are likely. Flash flooding may
also be possible in some areas. The areas that will most likely
be experiencing the heaviest rainfall accumulations will be across
central, western, and eastern interior of Puerto Rico as well as
across northern portions of the island, including the San Juan
metro area. The time period when the heaviest rainfall activity
can be expected will be between 11 AM and 6 PM. Across the USVI,
scattered to isolated showers can also be expected from the late
morning into the afternoon hours, however, average rainfall
accumulations should be less than a half an inch.

Lesser moisture is expected for Monday and Tuesday, therefore, the
rainfall activity that develops is not expected to be as intense.
However, the deep-layered troughiness along with the light
steering flow are expected to prevail. As a result, the afternoon
convection that develops has the potential to result in urban and
small stream flooding once again. Given that the steering flow
will remain from the southeast, the activity is expected to be
concentrated along and north of the Cordillera central of Puerto
Rico. Across the USVI, only some isolated to scattered shower
activity is expected with light rainfall accumulations expected.

.LONG TERM...Wednesday through Sunday

By Tuesday the TUTT will have crossed Puerto Rico to be found
north of the island on Wednesday. It is expected to move to the
Leeward Islands by late Friday night, wander somewhat and then
retreat to the north on Sunday. A weak trough in the lower levels will
invade the ridging from the northeast out of the Atlantic to
bring some more showers late Thursday. Moisture will increase
gradually through Sunday.

On Sunday of next week the GFS and the ECMWF show a tropical
cyclone moving toward the Leeward Islands. The models have been
homing in on a solution that takes the system across Culebra
Monday night (16-17 Sep), but this is still highly uncertain and
is not fully reflected in the forecast at this time. In any case a
passing wave will bring better moisture late in the period.

&&

.AVIATION...VFR conditions expected through 07/14z. SHRA/TSRA are
expected top dvlp across PR between 07/15z and 07/22z with some
tops to FL500 psbl. The activity is expected to be near the
vicinity of TJSJ/TJMZ/TJBQ, with TEMPO MVFR to IFR conditions
possible. Winds light and variable through 07/12z, increasing to
10 to 15 kts from the E-ESE with sea breeze variations after
07/14z and hir gusts in TSRA. Maximum winds NE-ENE 20-30 kt btwn
FL340-500.

&&

.MARINE...Winds and seas are expected to remain below small craft
advisory levels through at least next Saturday. Showers and
thunderstorms will become more frequent today then taper off
Monday through Wednesday. Mariners who plan to be navigating in
the area early next week should keep abreast of the latest
forecasts of tropical systems.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 78 91 79 / 60 40 30 30
STT 89 79 88 80 / 50 40 30 30