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| #7680 (Received by flhurricane at: 4:59 AM 09.Sep.2004) TCDAT4 HURRICANE IVAN DISCUSSION NUMBER 28 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT THU SEP 09 2004 AIR FORCE RECON THIS MORNING HAS FOUND AN INTENSE HURRICANE IVAN. THE CENTRAL PRESSURE OF 922 MB HAS DROPPED 15 MB IN THE PAST 7 HOURS...WHILE THE 700 MB FLIGHT-LEVEL WINDS HAVE INCREASED TO 154 KT...EQUAL TO 139 KT SURFACE WIND...TO THE NORTH AND NORTHEAST OF THE CENTER ON TWO SEPARATE PASSES. IN ADDITION...AND EYEWALL DROPSONDE RECORDED A WIND SPEED OF 175 KT AT ABOUT 630 FT ABOVE SEA LEVEL. BASED ON THIS INFORMATION...IVAN IS EASILY UPGRADED TO A 140-KT CATEGORY 5 HURRICANE. AS I WRITE...A NEW RECON REPORT INDICATES AN EXTRAPOLATED PRESSURE OF 916 MB. THE INITIAL MOTION IS 290/13. IVAN HAS BEEN SLOWLY GAINING LATITUDE OVER THE PAST 24 HOURS...AND THE LAST TWO RECON FIX POSITIONS SUGGEST THAT IVAN MAY BE MOVING AT 295 DEGREES. DROPSONDE DATA FROM THE 00Z SYNOPTIC SURVEILLANCE FLIGHTS AROUND IVAN HAS RESULTED IN TIGHT AGREEMENT AMONG ALL OF THE AVAILABLE NHC MODELS THROUGH 60 HOURS...ON IVAN MOVING OVER OR AT LEAST VERY NEAR JAMAICA IN 36-48 HOURS. AFTER THAT...THE MODELS DIVERGE CONSIDERABLY...ALTHOUGH THE SPREAD IS MUCH LESS THAN IT HAS BEEN OVER THE PREVIOUS 2-3 DAYS. UNFORTUNATELY...THE MODEL SPREAD STILL BRACKETS THE FLORIDA PENINSULA. THE MAIN DIFFERENCE BETWEEN THE MODELS AGAIN REMAINS IN HOW THEY HANDLE THE DEVELOPMENT AND FUTURE TRACK OF A MID- TO UPPER-LEVEL LOW CURRENTLY NEAR 34N 48W. WATER VAPOR WINDS SUGGEST THAT THE UPPER-LOW IS STRONGER THAN ALL OF THE MODELS HAVE BEEN FORECASTING. HOWEVER...THE MODEL THAT INITIALIZED THE LOW THE BEST AT 00Z WAS NOGAPS. THIS MODEL HAS BEEN VERY CONSISTENT...ALONG WITH THE ECMWF MODEL...ON BRINGING IVAN ACROSS WEST-CENTRAL CUBA AND THEN OVER OR NEAR THE FLORIDA PENINSULA. THE UKMET MODEL REMAINS THE WESTERNMOST OUTLIER...WHILE THE GFS IS STILL THE EASTERNMOST OUTLIER. HOWEVER...BOTH MODELS HAVE BEEN GRADUALLY SHIFTING THEIR TRACKS TOWARD FLORIDA...AND THE LATEST GFDL RUN NOW TAKES IVAN ACROSS SOUTHEAST FLORIDA IN 96-120 HOURS. GIVEN THE BETTER AGREEMENT AMONG THE MODELS ON THIS FORECAST CYCLE...THE OFFICIAL TRACK IS CLOSE TO THE PREVIOUS FORECAST THROUGH 72 HOURS...AND THEN SHIFTED SLIGHTLY EASTWARD AT 96- AND 120-HR. THE UPPER-LEVEL OUTFLOW PATTERN IS IMPRESSIVE AND WELL-ESTABLISHED ...AND IF ANYTHING...WILL ONLY GET BETTER FOR THE NEXT 72-96 HOURS. THEREFORE...THE FUTURE INTENSITY WILL LIKELY BE MODULATED BY INNER- CORE CONVECTIVE CHANGES AND LAND INTERACTION SINCE TH WATER AHEAD OF IVAN IS ONLY FORECAST TO GET WARMER...AS WARM AS 30C SOUTH OF CUBA AND OVER THE FLORIDA STRAITS. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 09/0900Z 13.9N 70.0W 140 KT 12HR VT 09/1800Z 14.8N 72.0W 140 KT 24HR VT 10/0600Z 16.2N 74.3W 135 KT 36HR VT 10/1800Z 17.6N 76.4W 135 KT 48HR VT 11/0600Z 19.1N 78.3W 125 KT 72HR VT 12/0600Z 21.0N 80.2W 125 KT 96HR VT 13/0600Z 24.0N 81.0W 115 KT 120HR VT 14/0600Z 28.0N 81.0W 80 KT...INLAND OVER FLORIDA |
