Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 240818
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
418 AM AST Tue Sep 24 2019

.SYNOPSIS...
Increasing cloud cover and better organized convection were noted
over the eastern Caribbean waters in association with Tropical
Storm Karen. Doppler weather radar and recent satellite imagery
continue to show explosive deep convection associated with Karen
becoming more widespread and increasing over the past few hours.
Convective outflow and rainbands were also noted propagating
northwards and reaching parts of the islands from time to time.
Expect this activity to continue to increase and become more
frequent as Karen tracks north northwest across the forecast area
during the rest of the day into Wednesday.

A Flash Flood Watch remains in effect until Wednesday afternoon
for Puerto Rico and the U.S. Virgin Islands.

A Tropical Storm Warning is also in effect for Puerto Rico and
the U.S. Virgin Islands.

&&

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

The first rainbands of Karen were noted moving across the local
waters, with some of them making their way inland, overnight.
This activity is expected to continue and then to increase in
frequency and intensity as Karen moves closer during the morning.
GOES imagery and the Hurricane Hunter aircraft detected deep
convection increasing south of it center. The center of Karen is
still expected to move over or near Puerto Rico and the U.S.
Virgin Islands today. In the latest National Hurricane Center
intensity forecast, Karen makes landfall as a weak tropical storm
system. The main impacts associated with Karen are flooding
rains, winds, and hazardous marine conditions. Even though the
center of Karen will be over the Atlantic waters near northeast
Puerto Rico by this afternoon, flooding rains will likely continue
across PR and USVI through at least Wednesday. Therefore, a Flash
Flood Watch will be in effect until at least Wednesday evening.

Regardless of Karen`s intensity, the system is expected to produce
rainfall accumulation totals between 2 and 4 inches of rain, with
isolated rainfall amounts up to 8 inches possible, mainly across
the southern and eastern sections of Puerto Rico, including the
mountainous terrain, Vieques, Culebra and the U.S. Virgin Islands.


Based on the latest model guidance, a wet pattern will persist over
Puerto Rico and the U.S. Virgin Islands through at least Thursday
with Total Precipitable Water values ranging between 2 and 2.5
inches.

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

Moisture remnants from Tropical Storm Karen are forecast to be
gradually lifted north of the area by Friday; however, due to its
proximity, it will maintain a light southerly wind flow across
the area through Friday. This in turn will support a fairly moist
airmass persisting across the region and therefore favor the
development of afternoon convection across the islands. The next
tropical wave is forecast to push into the region Saturday through
Sunday, followed by decreasing moisture and improving weather
conditions on Monday and Tuesday.

Tropical Storm Lorenzo, which formed yesterday south of the Cape
Verde Islands, is currently forecast by the National Hurricane
Center to cross 20 north Saturday morning. This will be more than
1200 miles east of Puerto Rico, and this storm is currently not
expected to pose any direct threat to Puerto Rico or the U.S.
Virgin Islands.

&&

.AVIATION...VCSH/VCTS expected en route between PR and the Northern
Leeward Islands as the rainbands associated with TD Karen approaches
the area. Brief MVFR SCT-BKN lyrs nr FL022...FL050...FL090. Winds
light and variable bcmg...10-20 kts fm E-ESE with sea breeze
variations aft 24/14z. Please refer to the latest SIGMET as well as
NHC Advisory for TD KAREN.


&&

.MARINE...The recently upgraded TS Karen continues to track NNW
across the local Caribbean waters. Deteriorating seas and hazardous
marine conditions with squally conditions will be likely mainly
across the Caribbean waters and local passages. A tropical storm
warning remains in effect.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  90  76  91  78 /  80  80  60  50
STT  86  80  87  80 /  80  80  60  60

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Flash Flood Watch through Wednesday afternoon 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.

     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.

VI...Flash Flood Watch through Wednesday afternoon for St Croix-
     St.Thomas...St. John...and Adjacent Islands.

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

AM...Flash Flood Watch through Wednesday afternoon for Coastal Waters
     of Southern Puerto Rico out 10 NM-Coastal Waters of
     Southern USVI Vieques and Eastern Puerto Rico out 10 NM.

     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
     Southern Puerto Rico out 10 NM-Coastal Waters of Southern
     USVI Vieques and Eastern Puerto Rico out 10 NM.

&&

$$

SHORT TERM...RAM
LONG TERM....JA


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