Prognostic Meteorological Discussion
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FXCA20 KWBC 251047
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
646 AM EDT THU AUG 25 2016

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM AUGUST
25/06 UTC: A TROPICAL WAVE CONTINUES TO PULL AWAY...WHILE
SUSTAINING A BROAD AREA OF CYCLONIC ROTATION/LOW PRESSURE AND
ORGANIZED DEEP CONVECTION TO THE NORTHWEST OF PUERTO RICO. A
TRAILING MOIST PLUME EXTENDS BETWEEN THE ISLAND CHAIN AND PUERTO
RICO...AND THIS IS EXPECTED TO CONTINUE BATHING THE FORECAST AREA
DURING THE NEXT 24 HRS. IN A SOUTHEASTERLY STEERING FLOW...THIS IS
TO FAVOR MID MORNING CONVECTION ACROSS THE SAN JUAN METRO AREA.
BUT THE MOST ACTIVE IS LIKELY TO CLUSTER ALONG THE NORTHERN THIRD
OF THE ISLAND DURING THE AFTERNOON AS ENHANCED BY SEA BREEZE
CONVERGENCE-DIURNAL HEATING. IN THIS AREA THE HIGH RESOLUTION
MODEL GUIDANCE SHOW MAXIMA OF 1-2 INCHES IN SCATTERED CONVECTION.
THIS SEEMS REASONABLE CONSIDERING EVOLVING PATTERN AND GENERAL
LACK OF MESO-SYNOPTIC FORCING.

A TUTT LOW IS TO THEN SETTLE TO THE NORTHEAST OF THE LEEWARD ISLES
LATER ON FRIDAY. THE MEANDERING LOW/TROUGH WILL HOLD THROUGH
SUNDAY MORNING...THEN STARTS TO MEANDER WEST ACROSS THE NORTHEAST
CARIBBEAN ISLES. MEANWHILE...AS IT HOLDS TO THE EAST...THIS WILL
TEND TO FAVOR AN UPPER CONVERGENT PATTERN AND THE GRADUAL EROSION
OF AVAILABLE MOISTURE. THIS...HOWEVER...WILL NOT BE STRONG ENOUGH
TO COMPLETELY SUPPRESS CONVECTIVE DEVELOPMENT. ACROSS PUERTO RICO
WE EXPECT LATE MORNING SHOWERS TO BUILD ALONG THE CORDILLERA...AND
AS THE SOUTHEASTERLY STEERING FLOW HOLDS... IT IS TO ALSO FAVOR
EARLY AFTERNOON CONVECTION ACROSS NORTHWEST PUERTO RICO. IN THIS
AREA GLOBAL MODEL GUIDANCE AGREES ON POTENTIAL FOR SOME MODERATE
RAINFALL AMOUNTS. SOME ENHANCEMENT IS POSSIBLE LATER ON SUNDAY
INTO MONDAY AS THE TUTT ALOFT PROPAGATES ACROSS THE FORECAST AREA.

THE TUTT LOW IS TO ALSO STEER HURRICANE GASTON TO THE NORTH...WITH
THE NHC FORECASTING A NORTHWARD TRAJECTORY THAT IS TO KEEP THIS
SYSTEM FAR AND AWAY FROM THE FORECAST AREA.

CONTRERAS...IMN (COSTA RICA)
GALVEZ/DAVISON...WPC (USA)
$$




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