Tropical Storm in Puerto Rico, August 15 to 16, 2021

Area Forecast Discussion
National Weather Service San Juan PR
1127 AM AST Sun Aug 15 2021

.UPDATE...

Tropical Storm Warning remains in effect for Puerto Rico, the U.S.
Virgin Islands, and surrounding waters.
Flash Flood Watch remains in effect for Puerto Rico and the U.S.
Virgin Islands.

Tropical Storm Grace is currently south of the local islands, though
with rather ill-defined circulation and center. Rain bands have made
their way over the islands, bringing periods of moderate to heavy
rainfall, as well as occasional thunderstorms. Rainfall amounts so
far are locally up to 2 inches over land; based on radar data, up to
nearly 4 inches of rain has fallen between the northern USVI and St.
Croix, east of Vieques and Culebra. The storm has slowed down
compared to yesterday/last night, as was expected, and more areas of
locally intense rainfall are likely to be seen, lasting into
tomorrow. Forecast for expected local impacts remains on track, with
a total of 3 to 6 inches of rainfall, and locally higher amounts
expected. This rainfall also remains the main hazard, though
tropical-storm-force winds are possible, mostly as gusts, with the
highest potential in the south.

Please refer to the HLSSJU and TCVSJU for further details
regarding Tropical Storm Grace.

&&

.AVIATION...

MVFR/IFR conditions are possible across the local terminals today
and tonight due to +SHRA/TSRA from TS Grace. The +RA/TSRA will
continue to affect the local terminal sites through around 16/04Z
for the USVI terminals, and through around 16/08Z for the PR
terminals. Winds will range from 15 to 25 kts with gusts possibly
exceeding 35 kts through 16/08Z. CIGs could be between FL015-020 due
to the cloudiness associated with TS Grace.

&&

.MARINE...

No changes to previous forecast. Hazardous conditions continue to be
generated by the winds from Tropical Storm Grace. Seas of up to 10
feet, with winds up to 35 knots, gusting to 50 knots, are possible.
High risk of rip currents continues for all beaches. High Surf
Advisory continues into tonight for south-facing beaches.

&&

.PREV DISCUSSION... /issued 553 AM AST Sun Aug 15 2021/

UPDATE...A High Surf Advisory has been issued for southern Puerto
Rico, Vieques and Saint Croix.

PREV DISCUSSION... /issued 536 AM AST Sun Aug 15 2021/

SYNOPSIS...Tropical Storm Grace will continue to move across
the local islands bringing tropical storm force winds and periods
of heavy rain, with the potential for life-threatening flash
flooding and mudslides, as well as rapid river flooding. Hazardous
marine and coastal conditions are also expected today. As Tropical
Storm Grace moves away, weather conditions are expected to
improve late Monday into Tuesday. A more typical weather pattern
is expected Tuesday and onwards with locally induced afternoon
showers each day.

SHORT TERM...Sunday through Tuesday...

Tropical Storm Grace is expected to track west-northwest in the
general direction towards the U.S. Virgin Islands and Puerto Rico
throughout the day today with maximum sustained winds near 40 mph.
Grace will bring tropical storm force winds and periods of heavy
rain, with the potential for life-threatening flash flooding and
mudslides, as well as rapid river flooding. The most likely time
period for the heaviest rainfall activity associated with this
system is late this morning into early Monday, while the areas
most likely to receive the highest rainfall accumulations are
portions of the southern and eastern Puerto Rico as well as the
U.S. Virgin Islands. Expect rainfall accumulations between 3 and
6 inches, particularly across the U.S. Virgin Islands, as well as
southern and eastern Puerto Rico where isolated amounts up to 8
inches are possible.

Please refer to the HLSSJU and TCVSJU for details regarding Tropical
Cyclone Grace.

As Tropical Storm Grace moves away, weather conditions are expected
to improve late Monday into Tuesday. On Tuesday, a drier airmass
will encompass the forecast area. Nevertheless, lingering moisture
will combine with local effects and diurnal heating to result in
showers and thunderstorms across west Puerto Rico during the
afternoon hours.

LONG TERM...Wednesday through Monday...

Long term forecast is still on track. A mid to upper level ridge
will prevail throughout much of the forecast cycle with some
weakening anticipated Thu-Sat. At lower levels a broad surface high
pressure across the central Atlantic will yield moderate easterly
winds. The latest guidance continues to show precipitable water
values below the normal range (1.75 inches) most of the time.
Therefore, expect a typical weather pattern with shower and thunder
development limited to west areas of Puerto Rico each day. However,
passing showers across eastern coastal areas cant be ruled out.
Daytime high temperatures will be in the mid 80s to near 90 for
coastal areas, and in the mid 70s to near 80 for higher elevations

AVIATION...MVFR/IFR conditions are expected across terminals TJSJ,
TIST, and TISX due to +SHRA/TSRA from TS Grace. The +RA/TSRA will
continue to affect the local terminal sites the next 20 hrs.
Winds will range from 20 to 30 kts with gusts exceeding 40 kts
through 16/06Z. SCT015- BKN020 clouds through 15/12Z, then
SCT015-BKN020 clouds 15/16z- 16/06Z across most terminals sites.

MARINE...Conditions will continue to deteriorate as Tropical Storm
Grace moves across the local waters. Expect seas between 7 and 10
feet with occasional higher seas and winds between 35 and 45 knots
with higher gusts around 65 knots.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  83  78  83  79 /  90  90  60  50
STT  83  78  84  78 /  90  90  70  50

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Tropical Storm Warning for Central Interior-Culebra-Eastern
     Interior-Mayaguez and Vicinity-North Central-Northeast-
     Northwest-Ponce and Vicinity-San Juan and Vicinity-
     Southeast-Southwest-Vieques-Western Interior.

     High Rip Current Risk through Monday afternoon for Mayaguez and
     Vicinity-North Central-Northeast-Ponce and Vicinity-San
     Juan and Vicinity-Southwest-Western Interior.

     Flash Flood Watch through Monday evening for Central Interior-
     Culebra-Eastern Interior-Mayaguez and Vicinity-North
     Central-Northeast-Northwest-Ponce and Vicinity-San Juan and
     Vicinity-Southeast-Southwest-Vieques-Western Interior.

     High Surf Advisory until 8 PM AST this evening for Central
     Interior-Northeast-Ponce and Vicinity-Southeast-Southwest-
     Vieques-Western Interior.

     High Rip Current Risk through late tonight for Central Interior-
     Culebra-Southeast-Vieques.

     High Rip Current Risk through late Monday night for Northwest.

VI...Tropical Storm Warning for St Croix-St.Thomas...St. John...and
     Adjacent Islands.

     Flash Flood Watch through Monday evening for St Croix-
     St.Thomas...St. John...and Adjacent Islands.

     High Surf Advisory until 8 PM AST this evening for St Croix.

     High Rip Current Risk through late tonight for St Croix-
     St.Thomas...St. John...and Adjacent Islands.

AM...Tropical Storm Warning for Anegada Passage Southward to 17N-
     Atlantic Waters of Puerto Rico and USVI from 10 NM to 19.5N-
     Caribbean Waters of Puerto Rico from 10 NM to 17N-Coastal
     Waters of Northern Puerto Rico out 10 NM-Coastal Waters of
     Northern USVI and Culebra out 10 NM-Coastal Waters of
     Northwestern Puerto Rico out 10 NM-Coastal Waters of
     Southern Puerto Rico out 10 NM-Coastal Waters of Southern
     USVI Vieques and Eastern Puerto Rico out 10 NM-Coastal
     Waters of Southwestern Puerto Rico out 10 NM-Mona Passage
     Southward to 17N.

&&

SHORT TERM...JA/DSR/ERG
LONG TERM....CRS
PUBLIC DESK...CVB/RVT/ER

Perspectivas sobre Condiciones Peligrosas del Tiempo
Servicio Nacional de Meteorologia en San Juan PR
522 AM AST domingo 15 de agosto de 2021

AMZ710>745-PRZ001>013-161000-
San Juan y Vecindad-Noreste-Sureste-Este Interior-Norte Central-
Interior Central-Ponce y Vecindad-Noroeste-Oeste Interior-
Mayaguez y Vecindad-Suroeste-Culebra-Vieques-Las aguas costeras
cercanas y lejanas a la costa del Atlantico y Caribe-
522 AM AST domingo 15 de agosto de 2021

Esta perspectiva sobre las condiciones peligrosas del tiempo es para
Puerto Rico y las aguas costeras del Atlantico.

.Dia Uno...Hoy y esta noche

Favor de referirse a HLSSJU y TCVSJU para detalles sobre la Tormenta
Tropical Grace.

.Dias dos hasta el siete...lunes a sabado

Favor referirse al HLSSPN y TCVSJU para detalles sobre la Tormenta
Tropical Grace.

.Comunicado sobre informacion reportada por observadores...

No se espera activacion amplia de observadores. Favor de reportar
cualquier informacion sobre inundaciones, vientos, oleaje y
corrientes marinas al Servicio Nacional de Meteorologia en San Juan
mientras siguen las indicaciones de las autoridades locales y
estatales.

AMZ715-725-VIZ001-002-161000-
San Tomas, San John e Islas Adyacentes-Santa Cruz-Aguas cercanas
del Atlantico y aguas costeras adyacentes del Caribe-
522 AM AST domingo 15 de agosto de 2021

Esta perspectiva sobre las condiciones peligrosas del tiempo es para
Islas Virgenes Estadounidenses y las aguas costeras adyacentes.

.Dia Uno...Hoy y esta noche.

Favor de referirse a HLSSJU y TCVSJU para detalles sobre la Tormenta
Tropical Grace.

.Dias dos hasta el siete...domingo a viernes

Favor referirse al HLSSPN y TCVSJU para detalles sobre la Tormenta
Tropical Grace.

.Comunicado sobre informacion reportada por observadores...

No se espera activacion amplia de observadores. Favor de reportar
cualquier informacion sobre inundaciones, vientos, oleaje y
corrientes marinas al Servicio Nacional de Meteorologia en San Juan
mientras siguen las indicaciones de las autoridades locales y
estatales.