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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1204Z Jul 07, 2020)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
804 AM EDT TUE JUL 07 2020

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JUL 07/12
UTC: A PROGRESSIVE AFRICAN EASTERLY WAVE STREAMING ACROSS THE
TROPICAL ATLANTIC REACHED THE ISLAND CHAIN EARLY THIS MORNING.
THROUGH THE DAY IT IS TO CONTINUE ACROSS THE EASTERN
CARIBBEAN...ENTERING THE VIRGIN ISLANDS EARLY THIS EVENING. AS IT
ENTERS THE FORECAST AREA...MODELS CONSISTENTLY SHOW ENVIRONMENTAL
CONDITIONS IMPROVING...WITH THE WAVE DRAWING A PLUME OF DEEP
TROPICAL MOISTURE NORTH ACROSS THE LESSER ANTILLES TO THE
NORTHEAST CARIBBEAN. PWAT CONTENT IS EXPECTED TO PEAK AROUND TWO
INCHES THIS EVENING...WITH THE HIGHER MOISTURE CONTENT LIKELY TO
RESULT IN SCATTERED SHOWERS AND THUNDERSTORMS OVER THE VIRGIN
ISLES-EASTERN PUERTO RICO...AS SUGGESTED BY THE  ECMWF AND GFS GDI
FORECASTS FOR THIS PERIOD. THROUGH WEDNESDAY MORNING THE WAVE
RACES ACROSS PUERTO RICO...REACHING THE DOMINICAN REPUBLIC BY
DAYBREAK...WITH MOST ACTIVE CONVECTION EXPECTED OVER PUERTO RICO
SOUTH OF THE CORDILLERA.

SECONDARY CONVECTION IS EXPECTED ACROSS PUERTO RICO THROUGH MIDDAY
ON WEDNESDAY AS TRAILING MOISTURE PLUME LIFTS ACROSS THE FORECAST
AREA. BUT LATER IN THE DAY...THE MOISTURE CONTENT IS TO THEN
RAPIDLY EBB AS A DRY AND DUSTY SAHARAN AIR LAYER RAPIDLY ENTRAINS
FROM THE EAST. THIS WILL BE ACCOMPANIED BY A FAIRLY STRONG AND
SHALLOW TRADE WINDS INVERSION...WHICH IS LIKELY TO LAST THROUGH
MIDDAY ON SATURDAY. IN BRISK EASTERLY TRADES...MODELS SHOW THE
OCCASIONAL CLOUD CLUSTER TO STREAM ACROSS THE NORTHEAST CARIBBEAN.
BUT IN A VERY HOSTILE ENVIRONMENT...THESE ARE TO ONLY FAVOR LIGHT
TO TRACE RAINFALL AMOUNTS IN PASSING SHOWERS...WITH STREAMERS
FORMING OVER THE VIRGIN ISLES-VIEQUES-CULEBRA TO TRAIN OVER
EASTERN PORTIONS OF PUERTO RICO.

LONG RANGE GUIDANCE SHOWS THE NEXT TROPICAL WAVE ENTERING THE
FORECAST AREA LATER ON SATURDAY EVENING/EARLY SUNDAY
MORNING...WITH THE WAVE FOLLOWING A SIMILAR EVOLUTION TO THE
LATTER AS IT MAKES LANDFALL DURING THE NIGHTTIME HOURS.

DAVISON...WPC (USA)