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#46195 (Received by flhurricane at: 5:03 PM 15.Sep.2005) TCDAT1 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 |