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#46142 (Received by flhurricane at: 10:58 AM 15.Sep.2005) TCDAT1 HURRICANE OPHELIA DISCUSSION NUMBER 38 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT THU SEP 15 2005 OPHELIA HAS BECOME RAGGED LOOKING IN RADAR IMAGERY... AND WIND DATA FROM BOTH COASTAL DOPPLER RADARS AND AN AIR FORCE RECONNAISSANCE AIRCRAFT INDICATE THAT MAXIMUM SUSTAINED WINDS HAVE DECREASED TO 70 KT...WHICH MAY BE A LITTLE GENEROUS. THE CENTRAL PRESSURE HAS ALSO INCREASED 4 MB...NOW 986 MB...DURING THE PAST 6 HOURS. THE INITIAL MOTION ESTIMATE IS 065/03. OPHELIA HAS SLOWED DOWN AND HAS PERHAPS EVEN STALLED AS THE CYCLONE IS...ONCE AGAIN... CAUGHT BETWEEN TWO RIDGES. THE LARGE-SCALE RIDGE TO THE EAST THAT EXTENDS NORTHWARD FROM BERMUDA TO NOVA SCOTIA IS FORECAST TO MOVE SLOWLY EASTWARD... WHILE THE SHORTWAVE RIDGE LOCATED TO THE WEST FROM GEORGIA NORTHWARD TO OHIO IS EXPECTED TO CONTINUE TO SLOWLY WEAKEN AND GIVE WAY TO INCREASING WEST-SOUTHWESTERLY MID-LEVEL FLOW AHEAD OF AN APPROACHING SHORTWAVE TROUGH. THE OVERALL LARGE-SCALE FLOW PATTERN IS CURRENTLY MORE ZONAL THAN MERIDIONAL AND THIS PROGRESSIVE PATTERN IS EXPECTED TO PERSIST THROUGHOUT THE FORECAST PERIOD...WHICH SHOULD KEEP OPHELIA MOVING PARALLEL TO THE U.S. EAST COAST. THE 06Z NHC MODEL GUIDANCE HAS MADE A LITTLE MORE OF A WESTWARD SHIFT AFTER 48 HOURS...AND SOME OF THE MODELS LIKE NOGAPS AND UKMET BRING OPHELIA OVER OR VERY CLOSE THE NEW ENGLAND AREA. HOWEVER...THE GFDL...GFS...AND CANADIAN MODELS KEEP OPHELIA WELL TO THE EAST OF THE NORTHEASTERN UNITED STATES...WHICH SEEMS MORE REASONABLE GIVEN THE LOW AMPLITUDE FLOW PATTERN NOTED IN THE 12Z UPPER-AIR DATA AND WATER VAPOR IMAGERY. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS FORECAST...ONLY SLOWER DURING THE FIRST 48 HOURS. EXCEPT FOR THE EXCELLENT UPPER-LEVEL OUTFLOW PATTERN...NOT MUCH ELSE IS FAVORABLE FOR ANY INTENSIFICATION TO OCCUR. A SIGNIFICANT AMOUNT OF DRY MID-LEVEL AIR HAS INTRUDED FROM THE WEST...WHICH HAS HELPED TO ERODE THE CONVECTION ON THE WEST SIDE OF OPHELIA. COOL SHELF WATER JUST OFFSHORE THE OUTER BANKS IS ALSO HELPING TO STABILIZE THE ATMOSPHERE ON THE WEST SIDE AND WEAKEN THE CONVECTION. HOWEVER ...OPHELIA IS STILL CLOSE ENOUGH TO THE GULFSTREAM TO TAP INTO THE WARMER 82-83F WATER THAT EXISTS THERE...SO ONLY SLOW WEAKENING IS FORECAST UNTIL 48 HOURS WHEN INCREASING VERTICAL SHEAR AND MUCH COOLER WATER ARE EXPECTED TO ENHANCE THE TRANSITION INTO AN EXTRATROPICAL LOW PRESSURE SYSTEM. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 15/1500Z 34.8N 75.7W 70 KT 12HR VT 16/0000Z 35.0N 75.0W 65 KT 24HR VT 16/1200Z 35.7N 74.3W 65 KT 36HR VT 17/0000Z 37.1N 73.2W 60 KT 48HR VT 17/1200Z 39.2N 70.9W 55 KT 72HR VT 18/1200Z 44.2N 63.2W 50 KT...EXTRATROPICAL 96HR VT 19/1200Z 47.0N 56.0W 45 KT...EXTRATROPICAL 120HR VT 20/1200Z 51.0N 40.0W 45 KT...EXTRATROPICAL |