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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1223Z Aug 04, 2022)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
823 AM EDT THU AUG 04 2022

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM AUG
04/12UTC: A MID-LEVEL RIDGE AXIS EXTENDS FROM THE NORTH ATLANTIC
NEAR 30N 55W INTO THE VI. ALTHOUGH THIS IS ENHANCING STABILITY
SOME...THE DOMINANT FEATURE ASSOCIATED WITH THE CURRENT DRY
CONDITIONS ARE THE LIMITED AMOUNTS OF AVAILABLE MOISTURE
ASSOCIATED WITH A WEAK SAHARAN AIR LAYER. THE SAN JUAN SOUNDING
SHOWS A DRY LAYER LOCATED BETWEEN 650 AND 850 HPA. THIS IS
CONSISTENT WITH ISOLATED CUMULUS PROPAGATING IN THE
EAST-NORTHEASTLY TRADES OFF THE NORTH...EAST AND SOUTHEAST COASTS
OF PUERTO RICO. NOTE THAT THE LACK OF STRATIFORM STRUCTURES IS
CONSISTENT WITH A WEAK INVERSION BUT DRY AIR ENTRAINMENT PROCESSES
LIMITING THE DEVELOPMENT OF SIGNIFICANT PRECIPITATION.

OF INTEREST IS THE TROPICAL WAVE ARRIVING ON SUNDAY. MODELS ARE
ENTERING IN AGREEMENT ON THE EVOLUTION OF THIS SYSTEM...AND NOW
SHOW THE WET SPELL FOCUSING PRIMARILY ON SUNDAY. THE WAVE AXIS IS
FORECAST TO ARRIVE ON SUNDAY MORNING...AND THE BULK OF
PRECIPITATION TRAILS. AT THE CURRENT TIME...THE WAVE IS
PROPAGATING IN THE TROPICAL ATLANTIC NEAR 40W AND SHOWS LITTLE
CONVECTION ASSOCIATED WITH IT. YET...THIS IS GOING TO CHANGE ONCE
THE WAVE APPROACHES THE LESSER ANTILLES AS IT ENCOUNTERS A MORE
FAVORABLE ENVIRONMENT...INCLUDING ENHANCED UPPER DIVERGENCE
ASSOCIATED WITH THE KELVIN WAVE. IT APPEARS THAT THE BULK OF THE
PRECIPITATION WILL PASS JUST TO THE SOUTH OF THE ISLANDS...WHICH
IS CONSISTENT WITH THE PRESENCE OF A RIDGE TO THE NORTH.
YET...SOME OF THE MODERATE PRECIPITATION WILL MAKE IT INTO PUERTO
RICO...PEAKING DURING SUNDAY MORNING INTO THE EARLY AFTERNOON. ON
THESE LINES...EXPECT PRECIPITATION STARTING TO INCREASE AROUD
SUNRISE ON SUNDAY...CLOSE TO THE TIME OF THE WIND CHANGE FROM
EAST-NORTHEASTERLIES TO EAST-SOUTHEASTERLIES. EXPECT THE HEAVIEST
PRECIPITATION TO DEVELOP DURING SUNDAY MORNING INTO THE EARLY
AFTERNOON ACROSS SOUTHEAST PUERTO RICO...WHERE EXPECT MAXIMA OF
1-1.5 INCHES. THE SOUTHWEST VI WILL ALSO RECEIVE HIGHER AMOUNTS
THAN THEIR NORTHERN COUNTERPARTS...WITH  SCATTERED TOTALS OF 0.5-1
INCH. CONFIDENCE ON DETAILS WILL VERY LIKKELY INCREASE TOMORROW
FRIDAY...AS MODELS ARE GENERALLY CAPTURING THE SYSTEM WITH FAIR
AGREEMENT.

GALVEZ...WPC (USA)