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Subtropical Storm OLGA (Text)

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SUBTROPICAL STORM OLGA DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172007
1000 AM EST TUE DEC 11 2007
 
RECENT BUOY...QUIKSCAT...AND SHIP REPORTS INDICATE THAT OLGA'S PEAK
WINDS ARE NEAR 40 KT...AND EXTEND FARTHER AWAY FROM THE CENTER THAN
EARLIER ESTIMATED.  THE STRUCTURE OF OLGA...WITH ITS STRONGEST
WINDS LOCATED STILL 100-200 NMI FROM CENTER...CONTINUES TO BE
CONSISTENT WITH THAT OF A SUBTROPICAL CYCLONE.
 
THE INITIAL MOTION ESTIMATE IS 260/13...ALTHOUGH THE CENTER HAS
MOVED LITTLE OVER THE PAST FEW HOURS. A LOW- TO MID-LEVEL RIDGE
OVER THE WESTERN ATLANTIC IS EXPECTED TO KEEP OLGA ON A BASIC
WESTWARD PATH NEAR THE SOUTH COAST OF HISPANIOLA AND INTO THE
NORTHWESTERN CARIBBEAN SEA...AND MODEL GUIDANCE IS IN RELATIVELY
GOOD AGREEMENT ON THIS SCENARIO. THE OFFICIAL FORECAST LIES ALONG
THE SOUTHERN EDGE OF THE GUIDANCE ENVELOPE AND IS IN BEST AGREEMENT
WITH THE GFS.
 
ALTHOUGH THE CIRCULATION OF OLGA WILL BE INTERACTING WITH THE RUGGED
TERRAIN OF HISPANIOLA...THE PRESSURE GRADIENT AWAY FROM THE
CENTER...WHERE THE STRONGEST WINDS ARE LOCATED...WILL BE SLOW TO
DIMINISH.  THE UPPER-LEVEL TROUGH CURRENTLY OVER THE CYCLONE IS
FORECAST BY ALL THE GLOBAL MODELS TO WEAKEN AND BE REPLACED BY
STRONG NORTHWESTERLY SHEAR OVER THE NEXT 24-36 HOURS OR SO...AND
WHEN THIS HAPPENS OLGA SHOULD DEGENERATE TO A REMNANT LOW.
 
THE PRIMARY THREAT FROM OLGA IS HEAVY RAINFALL...WHICH IS
ALREADY PRODUCING LIFE-THREATENING MUD SLIDES IN PUERTO RICO.
THESE RAINS WILL BE SPREADING ACROSS HISPANIOLA OVER THE NEXT 24
HOURS...WHERE FLASH FLOODS AND MUD SLIDES ARE ALSO LIKELY.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/1500Z 18.1N  68.0W    40 KT
 12HR VT     12/0000Z 18.0N  70.5W    35 KT
 24HR VT     12/1200Z 18.1N  74.0W    30 KT
 36HR VT     13/0000Z 18.2N  77.4W    30 KT...REMNANT LOW
 48HR VT     13/1200Z 18.2N  80.5W    25 KT...REMNANT LOW
 72HR VT     14/1200Z 18.0N  85.0W    25 KT...REMNANT LOW
 96HR VT     15/1200Z...DISSIPATED
 
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FORECASTER FRANKLIN
 
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