Prognostic Meteorological Discussion
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FXCA20 KWBC 281044
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
644 AM EDT THU MAY 28 2015

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM MAY 28/06
UTC: BROAD TUTT CONTINUES TO DOMINATE FLOW OVER THE NORTHEAST
CARIBBEAN ISLES WHILE CENTERING ON A CLOSED LOW NEAR 26N 62W.
BUILDING CELL OF THE SUBEQUATORIAL RIDGE IS TO GRADUALLY DISPLACE
THIS AXIS TO THE NORTH-NORTHWEST OVER THE NEXT COUPLE OF
DAYS...WITH RIDGE TO THEN BECOME DOMINANT FEATURE EARLY DURING THE
WEEKEND. AS THE TUTT MOVES AWAY...AN INDUCED TROUGH IN THE
EASTERLY TRADES IS TO PULL ACROSS THE FORECAST AREA DURING THE DAY
TODAY. ON ITS WAKE A MOIST SOUTHEASTERLY FLOW IS TO ESTABLISH
ACROSS THE LESSER ANTILLES. PWAT CONTENT IS TO INCREASE TO 50-55MM
EARLY ON FRIDAY...WITH HIGH MOISTURE CONTENT EXPECTED TO PERSIST
FOR SEVERAL DAYS. MOISTURE THEN SLOWLY EBBS FROM THE EAST AS A
TRADE WINDS SURGE ENTERS THE ISLAND CHAIN DURING THE WEEKEND.

GLOBAL MODELS AGREE ON FAIRLY WET WEATHER CONDITIONS DURING THE
SHORT RANGE PERIOD...WITH MOST ACTIVE CONVECTION DEVELOPING ON
FRIDAY TO SATURDAY. BUT DURING MEDIUM RANGE PERIOD THEY DIVERGE ON
HOW SOON THE RAINS ARE TO END...WITH THE UKMET AND ECMWF BOTH
FORECASTING ACTIVITY TAPERING OFF EARLY ON MONDAY. THE GFS...IN
CONTRAST...MAINTAINS AN ACTIVE PATTERN THROUGH THE MIDDLE OF THE
WEEK. BOTH EUROPEAN MODELS SEEM TO FAVOR A STRONGER WIND SURGE AND
FASTER RESTORATION OF THE TRADE WINDS CAP THAN WHAT THE GFS. THE
METEOSAT DUST PRODUCT HINTS AT POSSIBLE SAL SPREADING ACROSS THE
TROPICAL ATLANTIC...BUT THIS IS BEING OBSCURED BY DENSE HIGH
CLOUDS. THUS IN A HIGH UNCERTAINTY FORECAST...MEDIUM RANGE
FORECAST CONFIDENCE IS LOW.

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




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