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475
FXCA20 KWBC 211201
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
800 AM EDT MON APR 21 2014

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI. POTENT SHORT
WAVE UPPER TROUGH CENTERS ON A LOW OFF THE COAST OF NORTH
CAROLINA. THIS TROUGH IS SUSTAINING A SURFACE CYCLONE AND
ASSOCIATED FRONTS AND CONVECTION. THE FRONT EXTENDS INTO THE
SOUTHEASTERN BAHAMAS AND SOUTHEASTERN CUBA WHERE THUNDERSTORM
ACTIVITY IS WANING. STRONGEST ACTIVITY CONCENTRATES TO THE NORTH
OF 25N...WHERE WIDESPREAD UPPER DIVERGENCE IS OCCURRING AHEAD OF
THE UPPER TROUGH AXIS...IN ASSOCIATION WITH PRE-FRONTAL
CONVERGENCE. A MID-UPPER RIDGE EXTENDS ACROSS MOST OF THE
CARIBBEAN. THE RIDGE CENTERS OFF THE COAST OF NORTHEASTERN
NICARAGUA AND EXTENDS INTO SOUTHERN HISPANIOLA-PUERTO RICO AND
THEN THE CENTRAL NORTH ATLANTIC. AT SAN JUAN...SUBSIDENCE
INVERSION WAS SITTING AT 875 HPA WITH A VERY DRY AIRMASS ALOFT.

UPPER TROUGH IS PROGRESSING TO THE EAST-NORTHEAST AND IS FORECAST
TO LIFT INTO THE NORTHERN ATLANTIC THROUGH THE CYCLE. AS THE
TROUGH LIFTS AND MOVES AWAY...SUPPORT FOR THE SURFACE FRONT WILL
DECREASE. NEVERTHELESS...AIRMASS NEAR THE TAIL OF THE FRONT WILL
CONTINUE EXHIBITING MODERATE CONVECTIVE INSTABILITY THROUGH THE
CYCLE. FRONT WILL HAVE NO DIRECT EFFECTS ON PUERTO RICO AS IT WILL
REMAIN TO THE NORTH. YET...PREFRONTAL WINDS ARE FORECAST TO WEAKEN
ACROSS PUERTO RICO AND TO THE NORTH...WHILE TRADE WINDS ACROSS THE
LESSER ANTILLES CONSERVE THEIR SPEEDS AND INTENSIFY SLIGHTLY. THIS
WILL GENERATE A REGION OF TRADE WIND CONVERGENCE THAT WILL LIKELY
AFFECT THE LEEWARD ISLANDS AND TO A LESSER EXTENT THE VIRGIN
ISLANDS AND EASTERN PUERTO RICO ON  TUESDAY NIGHT INTO WEDNESDAY
MORNING. THIS WILL ENHANCE MORNING SHOWERS. MODELS DIVERGE
SIGNIFICANTLY IN THIS EVOLUTION THUS CONFIDENCE IS TOO HIGH. WE
ARE STILL EXPECTING SOME ENHANCEMENT IN ACTIVITY DURING TUESDAY
EVENING INTO WEDNESDAY MORNING LEADING TO ACCUMULATIONS OF
05-10MM/DAY AND MAXIMA OF 15MM. OTHERWISE...EXPECTING GENERALLY
QUIET CONDITIONS WITH ACTIVITY CHARACTERIZED MOSTLY BY SHALLOW
CONVECTION.

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





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