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(Caution: Version displayed is not the latest version. - Issued 1123Z Sep 16, 2020)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
723 AM EDT WED SEP 16 2020

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM SEP
16/12UTC: NHC IS ISSUING ADVISORIES FOR HURRICANE TEDDY AND
TROPICAL STORM VICKY. NOTE THAT THE NHC FORECASTS HURRICANE TEDDY
TO INTENSIFY TO A MAJOR HURRICANE AS IT LIFTS TO THE NORTHEAST ON
THURSDAY.

AS TEDDY STRENGTHENS...IT IS FORECAST TO STEER THE REMNANTS OF
RENE TOWARDS THE NORTHEAST CARIBBEAN ISLES ON THURSDAY...WITH
WANING PERTURBATION REACHING THE FORECAST AREA LATER IN THE DAY.
MODELS THEN DIVERGE ON HOW THIS IS TO EVOLVE AS IT STREAMS ACROSS
THE FORECAST AREA...WITH GFS MAKING ADJUSTMENTS IN FAVOR OF A
BETTER ORGANIZED CIRCULATION THAN WHAT THE EUROPEAN MODELS
SUGGEST. BASED ON THE LATEST IMAGES...IT LOOKS LIKE THE GFS
OVERCORRECTED...AND A WEAKER PERTURBATION IS MORE LIKELY TO STREAM
ACROSS THE FORECAST AREA. AS IT CROSSES THE VIRGIN ISLES TO
EASTERN PUERTO RICO THIS WILL SUSTAIN LIGHT-MODERATE RAINFALL
AMOUNTS...WITH ACTIVITY LIKELY TO INTENSIFY AS IT ENTERS PUERTO
RICO DURING MAX HEATING DURING THE AFTERNOON/EVENING HOURS ON
THURSDAY TO EARLY MORNING ON FRIDAY.

ALTHOUGH THE MODELS DIVERGE ON HOW THE LOW LEVEL PATTERN EVOLVES
DURING THE SHORT RANGE PERIOD...THEY SEEM TO BE IN BETTER
AGREEMENT AT UPPER LEVELS...WITH GLOBAL GUIDANCE FOLLOWING SIMILAR
EVOLUTION THROUGH THE MEDIUM RANGE. IN THIS RUN...THE GFS MADE
PATTERN ADJUSTMENTS...FAVORING A WEAKER TUTT THAN PREVIOUSLY
SUGGESTED...WITH THE CLOSED CIRCULATION TO APPROACH THE NORTHEAST
CARIBBEAN ISLES LATER ON FRIDAY AS IT ROTATES AROUND HURRICANE
TEDDY IN A FUJIWHARA FASHION. THE UPPER LEVEL TROUGH/CLOSED LOW IS
EXPECTED TO MEANDER WEST DURING THE WEEKEND...SETTLING JUST NORTH
OF THE DOMINICAN REPUBLIC. ALTHOUGH THE UPPER TROUGH IS IN AN
IDEAL POSITION TO ENHANCE CONVECTIVE DEVELOPMENT ACROSS PUERTO
RICO...STRONG DOWNWARD MOTION ON THE PERIPHERY OF TEDDY MIGHT
NEGATE ANY POSITIVE INFLUENCE THE TROUGH ALOFT MIGHT HAVE ON LOCAL
WEATHER CONDITIONS. IN A LONG FETCH NORTH/NORTHEASTERLY
FLOW...DIURNAL ACTIVITY DURING THE WEEKEND IS TO CLUSTER OVER
INTERIOR PORTIONS OF PUERTO RICO/CORDILLERA DURING THE LATE
MORNING TO AFTERNOON HOURS. 

DAVISON...WPC (USA)