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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1036Z Apr 20, 2015)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
636 AM EDT MON APR 20 2015

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM APRIL
20/06 UTC: A MID LEVEL RIDGE EXTENDS EAST FROM THE WESTERN
CARIBBEAN ACROSS THE CUBA TO HISPANIOLA...WHILE A SHORT WAVE
TROUGH MEANDERS OVER THE EASTERN CARIBBEAN. MID LEVEL RIDGE
PATTERN IS FORECAST TO STRENGTHEN THROUGH TUESDAY EVENING...WITH
AXIS TO BUILD EAST ACROSS PUERTO RICO-VIRGIN ISLES. THIS IS TO
STRENGTHEN CAP INVERSION ACROSS THE FORECAST AREA...LEADING TO
EROSION OF AVAILABLE MOISTURE. AT LOW LEVELS...RIDGE OVER THE
ATLANTIC FAVORS LIGHT EASTERLY WINDS ACROSS THE FORECAST AREA...A
PATTERN THAT IS TO HOLD THROUGH WEDNESDAY EVENING. EARLY ON
THURSDAY...HOWEVER...WINDS VEER TO THE SOUTHEAST AS SURFACE RIDGE
YIELDS TO POLAR TROUGH OVER THE WESTERN ATLANTIC. MODELS THEN
PROJECT A SLIGHT INCREASE IN PWAT AMOUNTS AS ITCZ MOISTURE ADVECTS
ACROSS THE WINDWARD ISLES TO THE EASTERN CARIBBEAN.

IN THIS PATTERN EXPECTING ISOLATED CONVECTION TO DEVELOP ACROSS
PUERTO RICO DURING THE AFTERNOON HOURS...WITH ACTIVITY LIKELY TO
CLUSTER ALONG THE CORDILLERA AND WESTERN INTERIOR PORTIONS OF THE
ISLAND. OVER INTERIOR PORTIONS OF THE ISLAND THE HRWRF SHOWS
MAXIMA RANGING BETWEEN 1-3 INCHES IN ISOLATED CONVECTION. BUILDING
RIDGE AND STRENGTHENING CAP INVERSION WILL THEN SUSTAIN A SHARP
DECREASE IN ACTIVITY ON WEDNESDAY-THURSDAY...WITH GLOBAL MODEL
GUIDANCE SHOWING LITTLE TO NO ACTIVITY DURING THAT PERIOD.
ENVIRONMENTAL CONDITIONS...HOWEVER...BECOME SOMEWHAT MORE
FAVORABLE FOR CONVECTION TO DEVELOP LATER ON FRIDAY AS MID/UPPER
LEVEL TROUGH STREAMS ACROSS THE FORECAST AREA.

DISCUSSION FROM APRIL 20/12 UTC:

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC
INITIAL  24     36     48     60     72     84     96        TYPE
NONE

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