Prognostic Meteorological Discussion
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FXCA20 KWBC 271058
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
658 AM EDT TUE JUN 27 2017

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JUNE
27/06 UTC: A MID LEVEL CELL OF THE SUBTROPICAL RIDGE REMAINS THE
DOMINANT FEATURE ACROSS THE WESTERN ATLANTIC/NORTHERN
CARIBBEAN...SUSTAINING A STRONG CAP INVERSION ACROSS THE NORTHEAST
CARIBBEAN ISLES. THIS COMBINES WITH A DRY SAHARAN AIR LAYER TO
FAVOR FAIR WEATHER CONDITIONS ACROSS THE FORECAST AREA. IN BRISK
EASTERLY TRADES...PESTERING TRADE WIND SHOWERS ARE TO STREAM
ACROSS THE VIRGIN ISLES/EASTERN PUERTO RICO FROM
TIME-TO-TIME...TRIGGERING LIGHT RAINFALL AMOUNTS IN BRIEF SHOWERS.
MEASURABLE RAINFALL AMOUNTS...HOWEVER...ARE TO CONFINE TO WESTERN
PUERTO RICO BETWEEN RINCON AND MAYAGUEZ. THESE CONDITIONS ARE TO
GENERALLY PERSIST DURING THE NEXT TWO DAYS.

ON THURSDAY...AS A STRONG TROPICAL WAVE STREAMS ACROSS THE
FORECAST AREA...MODELS ARE SHOWING ENVIRONMENTAL CONDITIONS
BECOMING MORE FAVORABLE AND CONDUCIVE FOR CONVECTION TO DEVELOP. A
WANING TUTT TO THE NORTHEAST OF THE LEEWARD ISLES IS TO SHED SHORT
WAVE VORTICES THAT ARE TO THEN REVOLVE AROUND THE MID LEVEL RIDGE.
AS THEY STREAM ACROSS THE NORTHEAST CARIBBEAN...THESE COULD LEAD
TO THE GRADUAL EROSION OF TRADE WINDS CAP. AS THE RIDGE/INVERSION
WEAKENS DEEPER MOISTURE IS TO THEN POOL ACROSS THE FORECAST
AREA...WITH GFS AND ECMWF NOW AGREEING ON PWAT CONTENT OF NEARLY
TWO INCHES BY MIDDAY ON THURSDAY. THE INFLOW OF DEEP TROPICAL
MOISTURE WILL THEN FEED CONVECTIVE DEVELOPMENT ON THURSDAY AND
FRIDAY...WITH SCATTERED DEEP CONVECTION TO ENVELOP THE ENTIRE
FORECAST AREA. BUT LACKING STRONG MID/UPPER LEVEL SUPPORT THESE
ARE TO GENERALLY FAVOR MODERATE RAINFALL AMOUNTS. MOST ACTIVE IS
EXPECTED ACROSS THE VIRGIN ISLES-CARIBBEAN COASTAL WATERS OF
PUERTO RICO...WITH A SECONDARY MAXIMA ON NORTHWEST PORTIONS OF THE
ISLAND AS THE WINDS VEER TO THE SOUTHEAST ON THURSDAY-FRIDAY.

GAJADHAR...SLMS (SAINT LUCIA)
GALVEZ/DAVISON...WPC (USA)
$$




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