ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM HURRICANE IVAN DISCUSSION NUMBER 20 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT TUE SEP 07 2004 AIR FORCE RECON INDICATES THAT IVAN HAS AND IS BECOMING BETTER ORGANIZED...WHICH IS ALSO SUPPORTED BY THE DRASTICALLY IMPROVED APPEARANCE IN SATELLITE IMAGERY. RECON REPORTS INDICATE AN INNER CONCENTRIC EYEWALL HAS ALMOST COMPLETELY DECAYED WHILE A NEW OUTER EYEWALL HAS STABILIZED AT AROUND 20 NMI DIAMETER. THE HIGHEST 700 MB FLIGHT-LEVEL WIND REPORTED SO FAR HAS BEEN 107 KT IN THE NORTHWEST QUADRANT. A DROPSONDE IN THE SAME AREA INDICATED 137 KT WINDS AT 953 MB...BUT THIS IS BELIEVED TO BE A WIND GUST. HOWEVER ...THE OVERALL VERTICAL WIND PROFILE CLEARLY REVEALED THAT IVAN IS IS BECOMING MUCH BETTER ORGANIZED AS COMPARED TO JUST 6 HOURS AGO. THE INITIAL MOTION IS 280/16. RECONNAISSANCE AND SATELLITE POSITION ESTIMATES INDICATE THAT IVAN HAS SLOWED ITS FORWARD SPEED SOMEWHAT. A NOAA GULFSTREAM-IV JET PERFORMED A SURVEILLANCE FLIGHT AROUND THE PERIPHERY OF IVAN LATE YESTERDAY EVENING WHICH HAD A SIGNIFICANT IMPACT ON THE 00Z MODEL RUNS. MOST OF THE NHC MODEL GUIDANCE IS TIGHTLY CLUSTERED ABOUT A WEST-NORTHWESTWARD MOTION WITH A GRADUAL DECREASE IN FORWARD SPEED THROUGH 72 HOURS AS IVAN MOVES AROUND THE SOUTHWEST PERIPHERY OF THE STRONG SUBTROPICAL RIDGE TO THE NORTH OF THE CARIBBEAN ISLANDS. HOWEVER...AFTER THAT THE MODELS BEGIN TO DIVERGE ENOUGH FOR ALREADY STORM WEARY PEOPLE IN FLORIDA TO BE CONCERNED ABOUT. THE GFDL HAS BEEN VERY CONSISTENT WITH A TRACK BETWEEN HAITI AND JAMAICA AND ACROSS SOUTHEASTERN CUBA. THE NEW 00Z GFS RUN NOW HAS A MORE REALISTIC TROPICAL CYCLONE VORTEX IN THE MODEL INITIALIZATION...AND IT HAS SHIFTED ITS TRACK MORE TO THE EAST OR RIGHT OF THE PREVIOUS RUNS. THIS IS ALSO CONSISTENT WITH THE LATEST NOGAPS AND GFDN MODELS. THE UKMET APPEARS TO BE THE ONLY OUTLIER AT 96HR AND 120HR BY TAKING IVAN WEST-NORTHWESTWARD TOWARD WESTERN CUBA. THIS SEEMS UNLIKELY GIVEN THAT ALL OF THE MODELS ... INCLUDING THE UKMET...GRADUALLY BUILD A STRONG HIGH AMPLITUDE HIGH/RIDGE ACROSS THE CENTRAL U.S. AND MEXICO AND INTO THE WESTERN GULF OF MEXICO BY 120 HOURS THAT SHOULD ACT TO BLOCK ANY WESTWARD MOTION INTO THE CENTRAL AND WESTERN GULF. IN RESPONSE TO THE WESTERN U.S. RIDGING ...A BROAD TROUGH IS FORECAST TO REMAIN IN THE WAKE OF FRANCES ACROSS THE SOUTHEASTERN U.S. AND THE CENTRAL AND EASTERN GULF OF MEXICO...WHICH UNFORTUNATELY OPENS THE DOOR FOR IVAN TO POSSIBLY SLOW AND MOVE MORE NORTHWARD BY 120HR ACROSS CENTRAL CUBA. THE OFFICIAL FORECAST TRACK IS CLOSE TO THE PREVIOUS TRACK THROUGH 72 HOURS...AND THEN TO THE RIGHT OF TRACK AFTER THAT ...WHICH IS CONSISTENT WITH THE GUNA AND GUNS CONSENSUS MODELS. IVAN IS FORECAST TO MOVE OVER PROGRESSIVELY WARMER WATER...REACHING NEAR 30C WATER IN 72HR. GIVE THE CURRENT AND FORECAST OUTFLOW PATTERN TO REMAIN QUITE IMPRESSIVE...THEN AT LEAST STEADY INTENSIFICATION APPEARS TO BE IN ORDER. IF THE OUTFLOW ON THE WEST SIDE OF IVAN TAPS INTO THE MID-/UPPER-LEVEL LOW TO THE WEST OVER THE CENTRAL CARIBBEAN SEA...THEN RAPID INTENSIFICATION COULD OCCUR. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 07/0900Z 11.4N 58.5W 95 KT 12HR VT 07/1800Z 12.0N 61.2W 105 KT 24HR VT 08/0600Z 13.0N 64.5W 110 KT 36HR VT 08/1800Z 14.2N 67.6W 115 KT 48HR VT 09/0600Z 15.5N 70.5W 120 KT 72HR VT 10/0600Z 18.0N 75.5W 120 KT 96HR VT 11/0600Z 20.5N 79.0W 120 KT 120HR VT 12/0600Z 23.0N 81.0W 100 KT...INLAND $$ NNNN
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Page last modified: Tuesday, 07-Sep-2004 09:02:53 UTC