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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1109Z Aug 15, 2014)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
709 AM EDT FRI AUG 15 2014

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI. AT UPPER
LEVELS...A TUTT LOW NORTH OF THE ISLANDS CONTINUES TO LIFT AS A
RIDGE BUILDS FROM THE EAST. AT MID LEVELS...THIS RIDGE IS TO
GRADUALLY BECOME THE DOMINANT FEATURE ACROSS THE WESTERN
ATLANTIC-NORTHERN CARIBBEAN ISLES-GULF OF MEXICO THROUGH SATURDAY
EVENING/EARLY SUNDAY MORNING. AT LOW LEVELS...TROPICAL WAVE IS
INITIALIZED ALONG 53W/54W...WITH MOST ACTIVE CONVECTION WEST OF
THE AXIS. THIS SUGGESTS THAT WAVE IS BECOMING NEGATIVELY TILTED
WITH HEIGHT. THE WAVE ENTERS THE LESSER ANTILLES AROUND 06UTC ON
SATURDAY...CROSSING THE VIRGIN ISLES BY FIRST LIGHT. THROUGH 18UTC
IT IS TO MOVE ACROSS EASTERN PUERTO RICO...AND LATER IN THE DAY
REACHES THE MONA PASSAGE.

AS IT ENTERS THE FORECAST AREA...THIS WAVE IS TO ENCOUNTER
BUILDING MID LEVEL RIDGE PATTERN...WITH UPPER ENVIRONMENTAL
CONDITIONS QUICKLY BECOMING HOSTILE TO ORGANIZED CONVECTION. IF
THE WAVE REMAINS NEGATIVELY TILTED AS SOME OF THE MODELS
SUGGEST...WE ARE PROBABLY LOOKING AT 2-3 HRS OF DEEP
CONVECTION...TO BE FOLLOWED BY A COUPLE OF HOURS OF LIGHT SHALLOW
ACTIVITY. IN THIS ENVIRONMENT...GLOBAL MODEL GUIDANCE SHOWING MOST
ACTIVE CONVECTION ACROSS THE VIRGIN ISLES-EASTERN PUERTO
RICO...WITH MAXIMA PEAKING BETWEEN ONE TO TWO INCHES. THE MODELS
HAVE BEEN SURPRISINGLY CONSISTENT WITH THIS FORECAST. THE HIGHER
RESOLUTION WRF...ARW/NMM VERSIONS...ARE QUITE SUPPORTIVE OF THIS
FORECAST...PROJECTING MODERATE CONVECTION WITH WIDELY ISOLATED
BULLS EYES.

MEDIUM RANGE GUIDANCE THEN SHOWS A FAIRLY DEEP TUTT LOW ENTERING
THE EASTERN CARIBBEAN EARLY NEXT WEEK. THIS APPEARS STRONG ENOUGH
TO WEAKEN THE TRADE WINDS CAP...WITH MODELS SHOWING SCATTERED
SHALLOW CONVECTION SPUTTERING ACROSS THE FORECAST AREA LATER ON
TUESDAY THROUGH WEDNESDAY EVENING.

VALVERDE...IMN (COSTA RICA)
MEDINA...ONAMET (REPUBLICA DOMINICANA)
DAVISON...WPC(USA)