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FXCA20 KWBC 171040
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
639 AM EDT FRI MAY 17 2013

LAST NO AMENDS...NEXT ON MONDAY MAY 20.

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI. UPPER LEVEL
ANALYSIS SHOWS RIDGE OVER THE WESTERN PORTIONS OF THE DOMAIN. EAST
OF THIS AXIS...A BROAD/LOW AMPLITUDE TROUGH EXTENDS OVER THE
WESTERN ATLANTIC TO THE NORTHEAST CARIBBEAN ISLES. JET MAXIMA
ROUNDING THE BASE OF THE TROUGH LIES OVER THE EASTERN
CARIBBEAN...WITH PUERTO RICO-USVI REMAINING ON CONVERGENT SIDE OF
THIS JET. AT LOW LEVELS...BRISK EASTERLY TRADES PREVAIL ACROSS THE
EASTERN CARIBBEAN ISLANDS...WITH SOMEWHAT STRONGER WINDS TO THE
SOUTH OF 15N. MOISTURE PLUME REMAINS BETWEEN JAMAICA-LEEWARD
ISLANDS...WITH BEST MOISTURE CONVERGENCE TO THE SOUTH OF
HISPANIOLA. AS PER SATELLITE DERIVED PWAT ANALYSIS...THIS PLUME
CONTINUES TO PULL AWAY FROM THE FORECAST AREA.

WEAK UPPER TROUGH IS TO PERSIST ACROSS THE NORTHEAST CARIBBEAN
ISLES OVER THE NEXT COUPLE OF DAYS...WITH A HIGHER AMPLITUDE
TROUGH TO DEVELOP FARTHER TO THE WEST TOWARDS THE BEGINNING OF
NEXT WEEK. AS THE TROUGH AMPLIFIES...AS SUBTROPICAL JET MAXIMA IS
TO REPOSITION TO THE WEST...WITH AN UPPER DIVERGENT TO GRADUALLY
TAKE FORM TOWARDS THE MIDDLE OF THE WEEK. AT MID LEVELS THE TROUGH
PATTERN IS CONSIDERABLY WEAKER THAN AT 250 HPA...WITH BEST INFLOW
OF SHORT WAVE ENERGY ACROSS THE BAHAMAS-CUBA-HISPANIOLA. ON THE
FRINGES OF THIS TROUGH...WEAK VORTICES WILL START TO SPREAD ACROSS
 PUERTO RICO AND THE USVI LATER DURING THE CYCLE. AT LOW
LEVELS...THE FLOW IS TO RETAIN AN EAST-TO-SOUTHEAST COMPONENT OVER
THE NEXT FEW DAYS. AS UPPER PATTERN EVOLVES...DEEPER MOISTURE IS
TO GRADUALLY SURGE OVER THE EASTERN CARIBBEAN TOWARDS THE
MIDDLE/LATTER PART OF NEXT WEEK.

AS A SOUTHEASTERLY LOW LEVEL FLOW PERSISTS...EXPECTING AFTERNOON
CONVECTION TO GENERALLY CLUSTER ON NORTHWEST PORTIONS OF PUERTO
RICO...WITH WIDELY ISOLATED CONVECTION TO POSSIBLY DEVELOP ACROSS
SAN JUAN METRO AREA AND OTHER PORTIONS OF THE ISLAND. THIS IS TO
PERSIST DURING THE NEXT THREE TO FOUR DAYS. DURING MEDIUM RANGE
PERIOD GLOBAL MODEL GUIDANCE TRENDING TOWARDS A WETTER SOLUTION...
WITH THE ECMWF FOLLOWING A SOMEWHAT SLOWER EVOLUTION THAN THE
GFS-UKMET. AS MJO ENVIRONMENTAL CONDITIONS BECOME MORE FAVORABLE
AND CONDUCIVE TO DEEP CONVECTION...THE LIKELIHOOD OF A MODERATE TO
HEAVY RAINFALL EVENT DURING THIS PERIOD SEEMS HIGH.

DISCUSSION FROM MAY 17/00UTC: PRODUCT NOT ISSUED.

BLENMAN...BMS (BARBADOS)
MCKENZIE...BDM (BAHAMAS)
DAVISON/GALVEZ...WPC (USA)
$$