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| #45029 (Received by flhurricane at: 11:11 PM 09.Sep.2005) TCDAT1 HURRICANE OPHELIA DISCUSSION NUMBER 15 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT FRI SEP 09 2005 THE SATELLITE SIGNATURE OF OPHELIA HAS BECOME LESS IMPRESSIVE DURING THE EVENING...WITH A SIGNIFICANT DECREASE IN BOTH THE COVERAGE AND INTENSITY OF THE CONVECTION. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT REPORTS THAT THE CENTRAL PRESSURE HAS RISEN TO 985 MB... AND THE THAT MAXIMUM 850 MB FLIGHT-LEVEL WINDS SO FAR HAVE BEEN 65 KT 25-30 N MI SOUTHEAST OF THE CENTER. IT APPEARS THAT A COMBINATION OF 20 KT SOUTHWESTERLY SHEAR AND DRY AIR INTRUSION HAS AT LEAST TEMPORARILY DISRUPTED THE CONVECTIVE STRUCTURE. THE INITIAL INTENSITY REMAINS 65 KT BASED MAINLY ON THE CENTRAL PRESSURE AND PERSISTENCE FROM THE PREVIOUS PACKAGE. THE INITIAL MOTION IS A RATHER UNCERTAIN 055/8...UNCERTAIN BECAUSE THE THE SHORT TERM MOTION SEEMS TO BE IN EXCESS OF 10 KT. THE REASON FOR THE ACCELERATION IS NOT CLEAR...BUT MAY BE RELATED TO UPPER-LEVEL WESTERLY FLOW. AS A TROUGH OVER THE WESTERN ATLANTIC LIFTS OUT AND IS REPLACED BY RIDGING OVER THE EASTERN UNITED STATES...OPHELIA IS EXPECTED TO SLOW AND LIKELY TURN BACK TOWARD THE WEST OR WEST-NORTHWEST. THIS TRACK IS SUPPORTED BY ALL THE LARGE-SCALE MODELS EXCEPT THE GFS...WHICH CALLS FOR A SLOW NORTHWARD MOTION AFTER 24 HR. THE NEW FORECAST TRACK IS SIMILAR TO THE PREVIOUS PACKAGE...CALLING FOR OPHELIA TO TURN BACK TO THE WEST-NORTHWEST AND MAKE LANDFALL IN THE SOUTHEASTERN UNITED STATES IN 72-96 HR. THE NEW TRACK IS A LITTLE EAST AND NORTH OF THE PREVIOUS TRACK BASED ON THE INITIAL POSITION. IT SHOULD BE NOTED THAT NONE OF THE LARGE-SCALE MODELS HAVE FORECAST THE CURRENT MOTION...AND IF THE MOTION CONTINUES THE FORECAST TRACK WILL LIKELY UNDERGO SOME ADJUSTMENTS IN LATER ADVISORIES. THE INTENSITY FORECAST REMAINS PROBLEMATIC. THE SHIPS...GFDL...AND FSU SUPERENSEMBLE ALL FORECAST OPHELIA TO REACH 85 KT BEFORE LANDFALL...AND THE INTENSITY FORECAST WILL FOLLOW SUIT. THAT BEING SAID...THE CURRENT SHEAR...ABUNDANT DRY AIR SEEN IN WATER VAPOR IMAGERY...AND BROAD STORM STRUCTURE WILL LIKELY SLOW DEVELOPMENT. HOW LONG THE SHEAR WILL LAST IS UNCERTAIN...AS THE LARGE-SCALE MODELS HAVE DIFFERING SOLUTIONS ON HOW THE UPPER-LEVEL WINDS WILL EVOLVE NEAR OPHELIA. AN EXTRA COMPLICATION IS THAT OPHELIA IS FORECAST TO MOVE OVER SEA SURFACE TEMPERATURES OF 27-28C...EXCEPT WHEN IT PASSES OVER THE GULF STREAM. THE SLOW MOTION OVER RELATIVELY SHALLOW WARM WATER MAY ALLOW THE STORM TO UPWELL COOLER WATER AND INHIBIT INTENSIFICATION. IT IS POSSIBLE THAT OPHELIA COULD BECOME A CATEGORY THREE HURRICANE...BUT IT WOULD NOT BE A SURPRISE IF IT STRENGTHENED LESS THAN CURRENTLY FORECAST. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 10/0300Z 30.4N 77.0W 65 KT 12HR VT 10/1200Z 31.0N 76.8W 65 KT 24HR VT 11/0000Z 31.2N 76.7W 70 KT 36HR VT 11/1200Z 31.5N 77.2W 75 KT 48HR VT 12/0000Z 31.7N 77.9W 80 KT 72HR VT 13/0000Z 32.5N 79.5W 85 KT 96HR VT 14/0000Z 33.5N 80.0W 60 KT...INLAND 120HR VT 15/0000Z 35.5N 78.5W 30 KT...INLAND |
