Prognostic Meteorological Discussion
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FXCA20 KWBC 211038
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
638 AM EDT TUE APR 21 2015

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI VALID FROM
21/06 UTC. MID LEVEL RIDGE IS BUILDING WEST ACROSS THE GREATER
ANTILLES TO THE NORTHEAST CARIBBEAN ISLANDS. THIS IS STRENGTHENING
TRADE WINDS CAP ACROSS THE NORTHERN CARIBBEAN WHILE SUSTAINING
EROSION OF AVAILABLE MOISTURE. AT LOW LEVELS...EASTERLY TRADES
PREVAIL...WITH 850 HPA WINDS PEAKING AT 10-15KT. WIDELY ISOLATED
TRADE WIND SHOWERS EMBED IN THIS FLOW...AFFECTING THE VIRGIN ISLES
AND COASTAL WATERS OF PUERTO RICO.

MID LEVEL RIDGE PATTERN IS TO GENERALLY HOLD OVER THE NEXT SEVERAL
DAYS...HELPING MAINTAIN A STRONG CAP INVERSION ACROSS THE
NORTHEAST CARIBBEAN ISLES. HOWEVER...A PROGRESSIVE MID/UPPER LEVEL
SHORT WAVE TROUGH IS TO REVOLVE AROUND THIS AXIS LATER ON
FRIDAY...WITH BASE OF THE MID LEVEL TROUGH TO STREAM ACROSS THE
FORECAST AREA EARLY ON SATURDAY MORNING. ALTHOUGH WELL DEFINED
THROUGH MID LEVELS OF THE ATMOSPHERE...THE TROUGH DOES NOT SEEM TO
BE STRONG ENOUGH TO OVERCOME NEGATIVE INFLUENCE OF PERSISTENT MID
LEVEL RIDGE PATTERN. SO ANY ENHANCEMENT WITH THIS FEATURE MIGHT BE
SHORT IN DURATION AND VERY LOCALIZED. AT LOW LEVELS...LIGHT
EASTERLY TRADES ARE TO PREVAIL THROUGH THURSDAY EVENING...WITH
WINDS TO THEN VEER TO THE SOUTH-SOUTHEAST EARLY ON FRIDAY MORNING.
DUE TO STRONG MID LEVEL CAP INVERSION...THIS IS TO HAVE LITTLE TO
NO IMPACT ON AVAILABILITY OF MOISTURE ACROSS THE FORECAST
AREA...WITH MODELS NOW FAVORING BEST MOISTURE CONVERGENCE FAR TO
THE NORTH ALONG A MEANDERING FRONT OVER THE ATLANTIC.
HOWEVER...ABOVE NORMAL TEMPERATURES ARE LIKELY TO AFFECT NORTHERN
PUERTO RICO DURING THE WEEKEND.

DUE TO UNFAVORABLE ENVIRONMENTAL CONDITIONS...GLOBAL MODELS ONLY
PROJECTING TRACE RAINFALL AMOUNTS IN WIDELY ISOLATED CONVECTION.
PER THE HRWRF... MEASURABLE AMOUNTS ARE TO LIMIT TO WESTERN
INTERIOR PORTIONS OF PUERTO RICO OVER THE NEXT COUPLE OF
DAYS...AND THIS SEEMS REASONABLE CONSIDERING CURRENT PATTERN.

CRAIG...TTMS (TRINIDAD AND TOBAGO)
SAMUEL...MDS (SURINAME)
DAVISON...WPC (USA)
GALVEZ...WPC (USA)
$$





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