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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1138Z Dec 15, 2014)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
638 AM EST MON DEC 15 2014

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI. A MID/UPPER
LEVEL TROUGH EXTENDS OVER THE WESTERN ATLANTIC...ENVELOPING AREA
TO THE WEST OF 50W AND NORTH OF 20N. THE TROUGH PATTERN ALOFT
SUSTAINS DEEP LAYER CONVECTIVE INSTABILITY ACROSS
HISPANIOLA-VIRGIN ISLES...WITH MOISTURE CONVERGING BETWEEN A
SURFACE FRONT OVER NORTHERN HISPANIOLA AND A PREFRONTAL SHEAR LINE
OVER PUERTO RICO. SATELLITE DERIVED ANALYSIS SHOWS PWAT AMOUNTS OF
45-50MM POOLING ACROSS THE VIRGIN ISLES INTO PUERTO RICO.

MID/UPPER TROUGH OVER THE WESTERN ATLANTIC IS TO QUICKLY PULL TO
THE EAST-NORTHEAST LATER THIS EVENING. A SHORT WAVE TROUGH IS TO
FOLLOW...FORECAST TO TAKE A BEELINE ACROSS THE BAHAMAS DURING THE
DAY ON TUESDAY...REACHING PUERTO RICO-USVI EARLY ON WEDNESDAY
MORNING. ON ITS WAKE...A MID LEVEL RIDGE IS TO THEN BUILD FROM THE
WEST...RESTORING THE TRADE WINDS CAP ACROSS THE FORECAST AREA
WHILE SUSTAINING GRADUAL EROSION OF AVAILABLE MOISTURE. AT LOW
LEVELS...THE SURFACE FRONT IS TO STALL TO THE NORTH...WHILE
PREFRONTAL SHEAR LINE IS TO MEANDER BACK AND FORTH BETWEEN PUERTO
RICO AND THE NORTHERN LEEWARD ISLES OVER THE NEXT COUPLE OF DAYS.
AS DEEP LAYER CONVECTIVE INSTABILITY IS TO PERSIST...EXPECTING
PWAT TO RANGE BETWEEN 40-45MM THROUGH WEDNESDAY EVENING.

THE GFS AND ECMWF ARE IN EXCELLENT AGREEMENT DURING THE SHORT
RANGE PERIOD...PROJECTING RAINFALL AMOUNTS OF 35-40MM/DAY ACROSS
PUERTO RICO AND THE USVI OVER THE NEXT TWO DAYS. THIS MIGHT BE
SOMEWHAT CONSERVATIVE CONSIDERING DEEP LAYER CONVECTIVE
INSTABILITY AND MESO-SYNOPTIC FORCING ACROSS THE FORECAST AREA.
THE HRWRF SHOWS HIGHER AMOUNTS...WITH THE ARW VERSION OF THE MODEL
INITIALLY SHOWING THE MOST ACTIVE CLUSTERING ALONG THE SURFACE
FRONT AS IT MEANDERS NORTH OF THE FORECAST AREA. BUT AS DIURNAL
HEAT CYCLE ESTABLISHES EARLY THIS AFTERNOON...IT THEN SHOWS
MODERATE TO HEAVY RAINFALL AMOUNTS CLUSTERING ALONG THE NORTHERN
SLOPES OF THE CORDILLERA CENTRAL...PROJECTING MAXIMA OF 75-100MM.
THIS SEEMS REASONABLE UNDER CURRENT DYNAMICS.

DISCUSSION FROM DECEMBER 15/00UTC: 

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC
INITIAL  24     36     48     60     72     84     96     TYPE

NONE.

JN BAPTISTE...MS (SAINT LUCIA)
NANDA...MDS (SURINAME)
DAVISON...WPC (USA)