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| #215390 (Received by flhurricane at: 4:53 PM 10.Sep.2008) TCDAT4 HURRICANE IKE DISCUSSION NUMBER 39 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL092008 500 PM EDT WED SEP 10 2008 THE RECONNAISSANCE AIRCRAFT DATA SHOW THAT IKE HAS TWO WELL-DEFINED WIND MAXIMA OF ROUGHLY EQUAL STRENGTH. THE PEAK FLIGHT-LEVEL WINDS OF 93 KT WERE FOUND IN A BAND ABOUT 90 NM EAST OF THE CENTER. A DROPSONDE WITHIN A FEW MILES OF THE CENTER REPORTED LOW-LAYER MEAN WINDS OF 97 KT...WHICH CORRESPOND TO 82 KT AT THE SURFACE. THE ADVISORY WINDS ARE SET TO 85 KT ON THIS BASIS. THE LARGE EXPANSE OF HURRICANE AND TROPICAL STORM FORCE WINDS EXPLAINS THE APPARENT MISMATCH BETWEEN THE PEAK WINDS AND THE CENTRAL PRESSURE. CONDITIONS IN THE GULF OF MEXICO REMAIN FAVORABLE FOR STRENGTHENING...INCLUDING LIGHT SHEAR AND STRONGLY DIFLUENT UPPER-LEVEL OUTFLOW FOR THE NEXT DAY OR TWO. ON THE OTHER HAND...RECENT NORTHWARD SHIFTS IN THE TRACK NOW SUGGEST THAT IKE MAY ENCOUNTER A COOL EDDY IN THE CENTRAL GULF AND MISS A WARM EDDY. NEVERTHELESS...ALL OBJECTIVE GUIDANCE NOW MAKES IKE A MAJOR HURRICANE AND THE OFFICIAL FORECAST IS INCREASED SLIGHTLY OVER THE PREVIOUS FORECAST. OTHER THAN INTERNAL EYEWALL DYNAMICS...WHICH ARE IMPOSSIBLE TO FORECAST MORE THAN A FEW HOURS IN ADVANCE...I SEE NO REASON WHY IKE SHOULD WEAKEN APPRECIABLY AS IT MOVES INTO THE WESTERN GULF. THE INITIAL MOTION IS 310/7. THE TRACK FORECAST PHILOSOPHY IS BASICALLY UNCHANGED. IKE IS MOVING NORTHWEST TOWARD A WEAKNESS IN THE SUBTROPICAL RIDGE. THIS RIDGE IS FORECAST TO BUILD IN OVER THE NEXT DAY OR TWO...WHICH SHOULD TURN THE TRACK BACK TO THE WEST-NORTHWEST UNTIL IKE APPROACHES A DEEP LAYER TROUGH FORECAST TO COVER THE WESTERN UNITED STATES IN TWO DAYS. ALL GUIDANCE TURNS IKE NORTHWARD TO VARYING DEGREES WITHIN A DAY OR SO OF PROJECTED LANDFALL. THERE HAS BEEN A NORTHWARD SHIFT IN SOME OF THE GUIDANCE...MOST NOTABLY THE GFDL AND GFS. IT IS TO BE EXPECTED THAT SUBTLE CHANGES IN THE MODEL EVOLUTION OF THE WESTERN TROUGH AND RIDGE OVER THE SOUTHEASTERN U.S. WILL LEAD TO GUIDANCE FLIP FLOPS OVER THE NEXT COUPLE OF DAYS. WITH THAT IN MIND...THE OFFICIAL FORECAST IS NUDGED ONLY SLIGHTLY NORTHWARD. IKE IS A VERY LARGE HURRICANE...AND IS EXPECTED TO REMAIN LARGE AS IT CROSSES THE GULF OF MEXICO. REGARDLESS OF WHERE THE CENTER CROSSES THE COAST...THE EFFECTS OF IKE WILL BE FELT OVER A LARGE AREA. FORECAST POSITIONS AND MAX WINDS INITIAL 10/2100Z 24.5N 86.1W 85 KT 12HR VT 11/0600Z 25.0N 87.4W 95 KT 24HR VT 11/1800Z 25.6N 89.3W 105 KT 36HR VT 12/0600Z 26.2N 91.5W 110 KT 48HR VT 12/1800Z 27.0N 94.0W 115 KT 72HR VT 13/1800Z 29.5N 97.0W 90 KT...INLAND 96HR VT 14/1800Z 34.5N 95.5W 30 KT...INLAND 120HR VT 15/1800Z...ABSORBED IN FRONTAL ZONE $$ FORECASTER FRANKLIN |
