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Tropical Discussion
 
(Latest Discussion - Issued 1156Z Aug 05, 2022)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
755 AM EDT FRI AUG 05 2022

NOTE: THE DAILY DISCUSSION AND QPF CHARTS WILL BE INTERRUPTED
UNTIL 15 AUGUST 2022. APOLOGIES FOR THE INCONVENIENCE.

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM AUG
05/12UTC: THE NORTHEAST CARIBBEAN CONTINUES UNDER THE INFLUENCE OF
A MID-LEVEL RIDGE LOCATED NEAR BERMUDA. IN ADDITION...A DRY AIR
MASS ASSOCIATED BY A SHARP TRADE WIND CAP EXTENDS TO THE EAST AND
NORTH OF THE LEEWARD ISLANDS. AS THE RIDGE HOLDS AND THE
PROPERTIES OF THIS AIR MASS ARE ADVECTED WESTWARD...TRADE WIND
CONVECTION CONTINUES TO BE LIMITED IN VERTICAL DEVELOPMENT. THE
SAN JUAN 0OUTC SOUNDING SHOWS A CAP NEAR 750 HPA AND PLENTY OF DRY
AIR BETWEEN THE CAP AND 350 HPA. SATELLITE IMAGERY SHOWS SCATTERED
SHALLOW TRADE WIND CONVECTION ALONG THE NORTH COAST OF PUERTO
RICO...PROPAGATING WEST-SOUTWESTWARD IN 25KT EAST-NORTHEASTERLY
TRADES. THE SAN JUAN RADAR CONFIRMS THAT A FEW SHOWERS ARE
DEVELOPING IN THESE CELLS ANONG THE NORTHWEST COAST OF PUERTO
RICO...BUT THEY APPEAR LIGHT GIVEN THE PRESENCE OF THE CAP AND
LIMITED AVAILABLE MOISTURE.

THE FEATURE OF INTEREST IN THE FORECAST CYCLE IS A TROPICAL WAVE
ARRIVING LATE ON SATURDAY INTO EARLY SUNDAY. THIS IS A WIDE
WAVE...WHICH WILL FAVOR A LONGER PERIOD OF PRECIPITATING
CONVECTION REGARDLESS OF ITS RAPID MOVEMENT. AGREEMENT IN MODEL
GUIDANCE HAS NOT NECESSARILY IMPROVED IN THE LATEST RUNS. FORECAST
PHILOSOPHY HAS NOT CHANGED SIGNIFICANTLY...WHICH MEANS THAT WE ARE
STILL EXPECTING A PEAK IN PRECIPITATION DURING THE DAY ON SUNDAY.
SOME OF THE GUIDANCE SHOWS THE MOIST PLUME WELL TO THE SOUTH OF
PUERTO RICO DURING THE EVENT...BUT GIVEN THE PRESENCE OF A TUTT TO
THE NORTH...WE FAVOR GUIDANCE THAT BRINGS THE MOIST PLUME AND BULK
OF THE PRECIPITATION CLOSER TO PUERTO RICO. THE LARGEST AMOUNTS
CONTINUE TO APPEAR IN THE SOUTHERN VI AND SOUTHEAST PORTIONS OF
PUERTO RICO WITH THIS EVENT...TO REACH SCATTERED MAXIMA OF 1-1.5
INCHES FROM LATE SATURDAY EVENING INTO LATE SUNDAY EVENING IN
VIEQUES AND ST.CROIX...AND SCATTERED MAXIMA OF 1.5-2.5 INCHES IN
SOUTHEASTERN AND EASTERN PUERTO RICO. AFTERNOON CONVECTION ON
SATURDAY WILL ALSO FAVOR SCATTERED MODERATE AMOUNTS IN THE WESTERN
CORDILLERA AND COAST...FORECAST TO REACH 1-1.5 INCHES. ALONG THE
SOUTH-CENTRAL AND SOUTHWEST COAST OF PUERTO RICO...EXPECT
SCATTERED MAXIMA OF 0.5-0.75 INCHES.

ONCE THE MOIST PLUME EXITS THE REGION EARLY ON MONDAY
MORNING...EXPECT A DRY AIR MASS TO MOVE INTO THE ISLANDS
ACCOMPANIED BY EAST-NORTHEASTERLY TRADES. THIS WILL SUSTAIN VERY
LITTLE PRECIPITATION ON MONDAY AFTERNOON...CLUSTERING IN SOUTHWEST
PUERTO RICO.

GALVEZ...WPC (USA)