Prognostic Meteorological Discussion
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FXCA20 KWBC 011044
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
644 AM EDT TUE SEP 01 2015

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM SEP
01/06UTC: TUTT TO THE NORTH EXTENDS WEST ALONG 22N/23N TO THE
TURKS...THEN SOUTH INTO A LOW WEST OF JAMAICA. SOUTH OF THIS
AXIS...WEAK CELL OF THE SUBEQUATORIAL RIDGE EXTENDS ACROSS THE
EASTERN CARIBBEAN...WHILE TO THE NORTH A BUILDING CELL OF THE
SUBTROPICAL RIDGE DOMINATES THE WESTERN ATLANTIC-EASTERN USA. AT
LOW LEVELS...A TROPICAL WAVE NOW EXTENDS ALONG 64W. THIS...IN
INTERACTION WITH THE TUTT TO THE NORTH...FAVORS SCATTERED SHOWERS
ACROSS THE LEEWARD TO THE VIRGIN ISLES.

UNDER INFLUENCE OF THE TUTT TO THE NORTH...ENVIRONMENTAL
CONDITIONS DURING THE NOWCAST PERIOD ARE TO REMAIN FAVORABLE AND
CONDUCIVE TO DEEP CONVECTION AS THE TROPICAL WAVE PULLS ACROSS THE
FORECAST AREA DURING THE DAY TODAY. PWAT AMOUNTS ARE TO PEAK
AROUND TWO INCHES IN ASSOCIATION WITH THIS FEATURE...WITH PWAT
MAXIMA EXPECTED AROUND 18UTC. THE COMBINATION OF TROPICAL
WAVE...UPPER LEVEL TROUGH AND DIURNAL HEATING COULD RESULT IN
LOCALIZED HEAVY CONVECTION DURING THE AFTERNOON HOURS. IN THIS
PATTERN... THERE IS A SLIGHT RISK OF SEVERE WEATHER OVER NORTHWEST
PORTIONS OF PUERTO RICO DURING THE AFTERNOON HOURS. DURING THE
MORNING...THE GLOBAL MODEL GUIDANCE SHOWS RAINFALL AMOUNTS OF
.25-.50 OF AN INCH ACROSS THE VIRGIN ISLES TO EASTERN PUERTO RICO.
THIS SEEMS REASONABLE...WITH THE POSSIBILITY OF LOCALIZED MAXIMA
OF 1-2 INCHES OVER SAINT CROIX AND AROUND EL YUNQUE RAINFOREST.
THE BULK OF THE CONVECTION...HOWEVER...IS EXPECTED ACROSS WESTERN
INTERIOR/NORTHWEST PR IN THE AFTERNOON...WHERE HIGHER RESOLUTION
MODEL GUIDANCE SHOWS HIGHLY PROBABLE MAXIMA OF 3-5 INCHES.

THROUGH SHORT RANGE PERIOD MID/UPPER LEVEL RIDGE IS TO THEN BUILD
ACROSS THE WESTERN ATLANTIC TO THE NORTHERN CARIBBEAN ISLES. THIS
DISPLACES THE TUTT SOUTH AND EAST...WITH MID/UPPER LEVEL
CONVERGENCE TO THEN QUICKLY ESTABLISH THROUGH MIDDAY ON WEDNESDAY.
THIS WILL BE FOLLOWED BY A SHARP DROP IN AVAILABLE MOISTURE AND A
DECREASE IN DIURNAL CONVECTION.

SALMON...MS (ANTIGUA AND BARBUDA)
CABRERA...ONAMET (THE DOMINICAN REPUBLIC)
DAVISON...WPC (USA)
GALVEZ...WPC (USA)

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