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| #147405 (Received by flhurricane at: 4:37 AM 22.Aug.2007) TCDAT4 HURRICANE DEAN DISCUSSION NUMBER 37 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042007 500 AM EDT WED AUG 22 2007 REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INDICATE THAT THE CENTRAL CORE OF DEAN COLLAPSED DURING PASSAGE ACROSS THE YUCATAN PENINSULA. THE AIRCRAFT FOUND THE RADIUS OF MAXIMUM WINDS HAD EXPANDED TO 55 N MI IN ASSOCIATION WITH A LARGE CONVECTIVE BAND. SATELLITE IMAGERY SHOWS CONVECTION FORMING CLOSE TO THE CIRCULATION CENTER...BUT THIS DOES NOT CORRESPOND WITH ANY WIND MAXIMUM SEEN BY THE AIRCRAFT. THE MINIMUM CENTRAL PRESSURE WAS 979 MB AND THE MAXIMUM SURFACE WINDS FROM THE STEPPED FREQUENCY MICROWAVE RADIOMETER WERE 64 KT. BASED ON THIS AND THE POSSIBILITY THE MAXIMUM WINDS WERE NOT SAMPLED...THE INITIAL INTENSITY REMAINS 70 KT. THE INITIAL MOTION IS 285/17. A DEEP-LAYER RIDGE NORTH AND NORTHEAST OF DEAN SHOULD STEER THE CYCLONE GENERALLY WEST-NORTHWESTWARD UNTIL LANDFALL IN ABOUT 12 HR...AND UNTIL EVENTUAL DISSIPATION OVER THE MOUNTAINS OF MEXICO. UPPER-LEVEL WINDS HAVE BECOME SOMEWHAT LESS FAVORABLE FOR INTENSIFICATION...WITH THE SHIPS MODEL AND ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN SHOWING 15-20 KT OF NORTHEASTERLY VERTICAL WIND SHEAR. THIS...COMBINED WITH THE LARGE CORE SIZE...SUGGESTS THAT RE-INTENSIFICATION MAY BE SLOWER THAN PREVIOUSLY THOUGHT. THE INTENSITY FORECAST NOW CALLS FOR WINDS TO INCREASE TO 80 KT BEFORE LANDFALL...WHICH IS A LITTLE ABOVE MOST OF THE GUIDANCE. DEAN SHOULD WEAKEN AFTER LANDFALL AND DISSIPATE BY 48 HR AT THE LATEST. THE WIND RADII HAVE BEEN CHANGED SIGNIFICANTLY BASED ON AIRCRAFT... BUOY...AND QUIKSCAT OBSERVATIONS. THE INCREASED AREA OF HURRICANE FORCE WINDS HAS REQUIRED A NORTHWARD EXTENSION OF THE HURRICANE WARNING ALONG THE MEXICAN COAST. FORECAST POSITIONS AND MAX WINDS INITIAL 22/0900Z 20.3N 94.8W 70 KT 12HR VT 22/1800Z 20.9N 97.1W 80 KT 24HR VT 23/0600Z 21.4N 100.2W 40 KT...INLAND 36HR VT 23/1800Z 21.8N 103.5W 20 KT...INLAND 48HR VT 24/0600Z...DISSIPATED $$ FORECASTER BEVEN |
