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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1112Z Apr 17, 2014)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
712 AM EDT THU APR 17 2014

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI. WATER VAPOR
IMAGERY NOW SHOWS THE SUBTROPICAL RIDGE WITH AXIS NORTH FROM THE
EASTERN CARIBBEAN TO THE ISLAND OF BERMUDA. A TUTT TO THE EAST
MEANDERS OVER THE CENTRAL ATLANTIC TO THE NORTHERN GUIANAS. COLD
CORE FEATURE ALOFT FAVORS GENERATION OF SHALLOW CONVECTIVE CELLS
ACROSS THE CENTRAL ATLANTIC...WITH EASTERLY TRADES SPREADING THE
CONVECTION ACROSS THE LEEWARD/VIRGIN ISLES.

RIDGE/TROUGH PAIR IS TO PERSIST THROUGH THE END OF THE WEEK. BUT
LATER DURING THE WEEKEND...THE RIDGE IS TO COLLAPSE AS A FAIRLY
STRONG TROUGH EXITING THE USA DEEPENS OVER THE WESTERN ATLANTIC.
AS THE RIDGE FLATTENS... THE TROUGH TO THE EAST OF THE ISLANDS IS
EXPECTED TO RAPIDLY PULL. MEANWHILE...IN A SLOW TO EVOLVE
PATTERN...A TRADE WINDS CAP WILL PERSIST ACROSS THE FORECAST
AREA...TRAPPING MOISTURE TO THE LOW LEVELS OF THE ATMOSPHERE.
EASTERLY TRADES WILL CONTINUE TO ADVECT CLOUD CLUSTERS FORMING TO
THE EAST ACROSS THE LEEWARD/VIRGIN ISLES TO PUERTO RICO...FAVORING
SCATTERED CONVECTION ACROSS THE NORTHEAST CARIBBEAN ISLES OVER THE
NEXT COUPLE OF DAYS. BUT AS THE TROUGH ALOFT WEAKENS DURING THE
WEEKEND...AND INSTABILITY WANES...THIS WILL THEN CUT OFF SUPPLY OF
MOISTURE DURING THE DAY ON SATURDAY. MOST ACTIVE CONVECTION IS
EXPECTED OVER THE NEXT TWO DAYS...WITH CELLS CLUSTERING ACROSS THE
VIRGIN ISLES/EASTERN PUERTO RICO DURING THE MORNING HOURS AND
WESTERN INTERIOR PORTIONS OF PUERTO RICO IN THE AFTERNOON.
RAINFALL AMOUNTS ARE TO RANGE BETWEEN 05-10MM/DAY WITH MAXIMA OVER
THE MOUNTAINS TO PEAK AT 15-20MM. NOTE THAT THE NMM VERSION OF THE
HRWRF IS SHOWING MAXIMA OF NEARLY 50MM ACROSS EL YUNQUE RAINFOREST
DURING THE DAY ON FRIDAY.

DURING MEDIUM RANGE PERIOD...AMPLIFYING POLAR TROUGH OVER THE
WESTERN ATLANTIC WILL THEN SUSTAIN EROSION OF TRADE WINDS CAP
ACROSS THE FORECAST AREA. GLOBAL MODELS THEN PROJECT DEEP LAYER
CONVECTIVE INSTABILITY ACROSS THE NORTHERN CARIBBEAN
ISLANDS...WITH THE GDI PROJECTING POTENTIAL FOR
SHOWERS/THUNDERSTORMS ACROSS THE DOMINICAN REPUBLIC-PUERTO RICO.

GALVEZ...WPC (USA)
GARCIA...SMN (MEXICO)
FIGUEROA...MARN (EL SALVADOR)