ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM HURRICANE IVAN DISCUSSION NUMBER 22 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 PM EDT TUE SEP 07 2004 AN AIR FORCE RECONNAISSANCE PLANE JUST MEASURED A PRESSURE OF 956 MB WITH A DROP AND 955 MB EXTRAPOLATED FROM 700 MB. IT ALSO MEASURED 118 KNOTS AT FLIGHT LEVEL AND A CLOSED EYEWALL OF 14 NMI DIAMETER. T-NUMBERS REMAIN AT 5.5 ON THE DVORAK SCALE. INITIAL INTENSITY IS 105 KNOTS. SHIPS MODEL INDICATE THAT THE SHEAR WILL REMAIN LOW OVER THE CENTRAL AND WESTERN CARIBBEAN. GLOBAL MODELS APPEAR TO SHOW A FAVORABLE UPPER-LEVEL ENVIRONMENT FOR STRENGTHENING. IN ADDITION...IVAN IS EXPECTED TO REACH THE WESTERN CARIBBEAN SEA WHERE THERE IS AN AREA OF HIGH OCEAN HEAT CONTENT...HIGH OCTANE GAS FOR HURRICANES...WHICH COULD ADD TO THE INTENSIFICATION. IVAN COULD BECOME STRONGER THAN FORECAST. INDICATIONS ARE THAT THERE WILL BE A VERY DANGEROUS HURRICANE OVER THE NORTHWESTERN CARIBBEAN SEA...WESTERN CUBA OR SOUTHEASTERN GULF OF MEXICO IN FIVE DAYS. THERE HAS BEEN NO CHANGE IN THE STEERING AND IVAN IS STILL MOVING TOWARD THE WEST OR 280 DEGREES AT 16 KNOTS. THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 3 DAYS. THEREAFTER...THE FORECAST BECOMES UNCERTAIN. GLOBAL MODELS CONTINUE TO DEVELOP A TROUGH OVER THE CENTRAL UNITED STATES AND THE GULF OF MEXICO. THIS TROUGH IS FORECAST TO ERODE THE RIDGE LEAVING A LARGE AREA OF WEAK STEERING CURRENTS IN THE NORTHWESTERN CARIBBEAN AND SOUTHEASTERN GULF OF MEXICO. BY THEN...THE HURRICANE COULD MOVE NORTH OVER WESTERN CUBA AND SOUTH FLORIDA AS INDICATED BY THE GFS...THE UK AND NOGAPS...OR CONTINUE ON A SLOW WEST-NORTHWEST TRACK AS INDICATED BY THE GFDL AND THE FSU SUPERENSEMBLE. THE LATTER ASSUMES THAT THE TROUGH IN THE GULF OF MEXICO WILL NOT BE STRONG ENOUGH TO STEER THE HURRICANE NORTHWARD...AND THAT THERE WILL BE ENOUGH RIDGING TO STEER THE HURRICANE TOWARD WESTERN CUBA AND THE GULF OF MEXICO. THE OFFICIAL FORECAST IS IN AGREEMENT WITH THE LATTER OPTION BIASED TOWARD THE CONSENSUS. FORECASTER AVILA FORECAST POSITIONS AND MAX WINDS INITIAL 07/2100Z 12.0N 62.0W 105 KT 12HR VT 08/0600Z 12.5N 64.5W 115 KT 24HR VT 08/1800Z 13.5N 67.7W 120 KT 36HR VT 09/0600Z 14.7N 70.7W 120 KT 48HR VT 09/1800Z 16.0N 73.5W 120 KT 72HR VT 10/1800Z 18.0N 77.5W 120 KT 96HR VT 11/1800Z 20.0N 81.0W 120 KT 120HR VT 12/1800Z 23.0N 84.0W 120 KT $$ NNNN
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Page last modified: Tuesday, 07-Sep-2004 20:52:53 UTC