Prognostic Meteorological Discussion
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FXCA20 KWBC 311112
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
712 AM EDT THU JUL 31 2014

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI. TUTT LOW
NORTH OF THE ISLANDS AND ASSOCIATED INDUCED/INVERTED TROUGH IN THE
EASTERLY TRADES ARE TO DOMINATE FORECAST DURING THE SHORT RANGE
PERIOD. THE TROUGH ALOFT IS ENHANCING DEEP LAYER CONVECTIVE
INSTABILITY...WHILE THE LOW LEVEL PERTURBATION SUSTAINS MOISTURE
CONVERGENCE ACROSS THE EASTERN CARIBBEAN ISLES. PWAT IN THIS AREA
NOW RANGES BETWEEN 40-45MM...AND THIS IS EXPECTED TO PERSIST AS
THE PERTURBATION MOVES ACROSS THE FORECAST AREA DURING THE DAY
TODAY. GRADUAL EROSION OF AVAILABLE MOISTURE IS THEN EXPECTED
THROUGH FRIDAY AFTERNOON...WHEN PWAT DECREASES TO 30-35MM.
MEANWHILE...EXPECTING SCATTERED CONVECTION ACROSS THE VIRGIN ISLES
AND PUERTO RICO. CONSIDERING EVOLVING PATTERN WE PREFER THE WETTER
GFS SOLUTION OVER THE DRYER EUROPEAN MODELS. IN A SOUTHWESTERLY
FLOW...THE MOST ACTIVE CONVECTION IS EXPECTED WEST OF MANATI LATER
THIS MORNING THROUGH THE EARLY AFTERNOON HOURS. THIS IS WELL
SUPPORTED BY THE HRWRF MODEL.

SYSTEM OF CONCERN IS THE TROPICAL DISTURBANCE ALONG THE ITCZ AND
NEAR 50W EARLY THIS MORNING. THE NHC UPPED THEIR PROBABILITY OF
TROPICAL CYCLONE FORMATION TO 60 PERCENT AS CONVECTION/WINDS
STRENGTHENED DURING THE MORNING HOURS. THE GLOBAL
MODELS...ALTHOUGH THEY DIVERGE ON THE TIMING...THEY NOW AGREE ON
THE POSSIBLE TRAJECTORY OF THIS FEATURE. DURING THE
PERIOD...BUILDING UPPER LEVEL RIDGE WILL FAVOR A DIVERGENT PATTERN
ALOFT...WITH ENVIRONMENTAL CONDITIONS ACROSS THE FORECAST AREA
GRADUALLY BECOMING MORE FAVORABLE AND CONDUCIVE TO ORGANIZED DEEP
CONVECTION. PER THE MODEL GUIDANCE...HUMACAO/BARCELONETA AND SAINT
CROIX/VIEQUES ARE THE MOST LIKELY TO EXPERIENCE THE BRUNT OF THIS
SYSTEM. IN THIS AREA THE FORECASTED MAXIMA RANGES BETWEEN 50-75MM.
THIS SEEM REASONABLE ACROSS THE VI AND VIEQUES. BUT OVER SOUTHEAST
PR...STRONG TOPOGRAPHICAL FORCING IN THE AREA IS  LIKELY TO FAVOR
MUCH HIGHER AMOUNTS.

FIGUEROA...MARN (EL SALVADOR)
VALVERDE...IMN (COSTA RICA)
DAVISON...WPC (USA)
$$




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