Hurricane OPHELIA

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HURRICANE OPHELIA DISCUSSION NUMBER  39
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT THU SEP 15 2005
 
OPHELIA HAS CONTINUED TO BECOME MORE RAGGED LOOKING IN RADAR AND
SATELLITE IMAGERY. AN AIR FORCE RESERVE UNIT RECONNAISSANCE
AIRCRAFT HAS RECENTLY MEASURED 850 MB FLIGHT-LEVEL WINDS OF 84 KT
IN THE NORTHEAST QUADRANT AND 79 KT IN THE SOUTHEAST QUADRANT.
THESE WIND VALUES ROUGHLY EQUAL 67 AND 63 KT...RESPECTIVELY. THE
CENTRAL PRESSURE HAS ALSO INCREASED TO 987 MB. THEREFORE...THE
INITIAL INTENSITY HAS BEEN DECREASED TO 65 KT...JUST ENOUGH TO KEEP
OPHELIA AS A HURRICANE.
 
THE INITIAL MOTION ESTIMATE IS AN UNCERTAIN 060/03. DURING THE PAST
6 HOURS...OPHELIA HAS BRIEFLY STALLED...MADE A SMALL CLOCKWISE
LOOP...AND NOW APPEARS TO BE DRIFTING EASTWARD. HOWEVER...WITH
RIDGING PERSISTING TO THE SOUTH AND EAST OF OPHELIA...THE HURRICANE
SHOULD MOVE MORE NORTHWARD THAN EASTWARD DURING THE NEXT 12 HOURS.
BEYOND THAT...THE MODELS ARE IN GENERAL AGREEMENT ON A SHORTWAVE
TROUGH OVER THE CENTRAL U.S. TO CONTINUE MOVING EASTWARD AND
GRADUALLY LIFT OUT OPHELIA TO THE NORTHEAST. THE 12Z GFDL...UKMET
...NOGAPS... AND CANADIAN MODELS HAVE MADE A SLIGHT WESTWARD
SHIFT OVER OR NEAR SOUTHEASTERN MASSACHUSETTS...WHILE THE GFS MODEL
DID NOT CHANGE AT ALL AND KEEPS OPHELIA WELL OFFSHORE OF THE
NORTHEASTERN U.S. COAST. A CLOSER LOOK AT ALL OF THE MODEL FIELDS
INDICATES THE MID-LEVEL CIRCULATION CENTERS ALSO REMAIN OFFSHORE
SIMILAR TO THE GFS SURFACE AND UPPER-LEVEL CIRCULATIONS. GIVEN THAT
OPHELIA IS A LARGE CIRCULATION AND SHOULD...THEREFORE... REMAIN
MORE VERTICALLY STACKED...THE OFFICIAL FORECAST TRACK IS NEAR THE
EASTERN PORTION OF THE NHC MODEL GUIDANCE ENVELOPE AND CLOSE TO THE
GFS MODEL AND THE PREVIOUS FORECAST TRACK.
 
ENVIRONMENTAL CONDITIONS ARE EXPECTED TO REMAIN UNFAVORABLE FOR ANY
INTENSIFICATION TO OCCUR. THE BIG QUESTIONS ARE HOW FAST WILL
OPHELIA WEAKEN AND WHEN WILL EXTRATROPICAL TRANSITION OCCUR.
OPHELIA IS EXPECTED TO REMAIN CLOSE ENOUGH TO THE WARMER GULFSTREAM
TO AT LEAST KEEP SOME DEEP CONVECTION GOING IN THE EASTERN
SEMICIRCLE FOR THE NEXT 24 HOURS. HOWEVER...ONCE OPHELIA REACHES
ABOUT 40N LATITUDE WHERE THE OCEAN TEMPERATURES DECREASE
SIGNIFICANTLY...THEN TRANSITION OVER TO A FORMIDABLE EXTRATROPICAL
LOW PRESSURE SYSTEM SHOULD BEGIN. HOWEVER...DUE TO THE UNCERTAINTY
ON EXACTLY WHEN THIS PHASE CHANGE WILL OCCUR...A TROPICAL STORM
WATCH HAS BEEN ISSUED FOR SOUTHEASTERN MASSACHUSETTS.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/2100Z 34.8N  75.6W    65 KT
 12HR VT     16/0600Z 35.1N  75.1W    65 KT
 24HR VT     16/1800Z 36.4N  74.1W    65 KT
 36HR VT     17/0600Z 38.7N  71.6W    60 KT...BECOMING EXTRATROPICAL
 48HR VT     17/1800Z 41.7N  67.7W    55 KT...EXTRATROPICAL
 72HR VT     18/1800Z 46.5N  58.0W    50 KT...EXTRATROPICAL
 96HR VT     19/1800Z 49.5N  47.0W    45 KT...EXTRATROPICAL
120HR VT     20/1800Z 53.0N  27.0W    45 KT...EXTRATROPICAL
 
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