ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM HURRICANE IVAN DISCUSSION NUMBER 21 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT TUE SEP 07 2004 LATEST INFORMATION FROM THE RECONNAISSANCE PLANE EARLIER THIS MORNING INDICATED THAT THE MINIMUM PRESSURE WAS 963 MB AND THE PEAK WIND AT FLIGHT LEVEL WAS 116 KNOTS. INITIAL INTENSITY HAS BEEN INCREASED TO 100 KNOTS. THIS IS ALSO SUPPORTED BY SATELLITE INTENSITY ESTIMATES OF 102 KNOTS FROM FROM BOTH TAFB AND SAB. CURRENTLY...THE OUTFLOW IS FAIR IN ALL QUADRANTS BUT A LARGE-UPPER LOW IN CENTRAL CARIBBEAN MAY INDUCE SOME SHEAR OVER THE HURRICANE. THIS IS ALSO INDICATED BY ANALYSES FROM THE UNIVERSITY OF WISCONSIN THAT SHOWS A 20-KNOT SOUTHERLY SHEAR AHEAD OF THE HURRICANE...WHICH COULD HALT INTENSIFICATION IN THE SHORT TERM. HOWEVER...MOST OF THE GLOBAL MODELS ULTIMATELY MOVE THE UPPER-LOW WESTWARD LEAVING A MORE FAVORABLE UPPER-LEVEL ENVIRONMENT FOR THE HURRICANE TO STRENGTHEN AS INDICATED IN THE OFFICIAL FORECAST. IVAN IS A POWERFUL HURRICANE WHICH IS FORECAST TO BE IN THE NORTHWESTERN CARIBBEAN IN FIVE DAYS. IVAN IS MOVING TOWARD THE WEST OR 280 DEGREES AT 16 KNOTS. THE HURRICANE IS SOUTH A RATHER STRONG SUBTROPICAL RIDGE WHICH IS STEERING THE HURRICANE WESTWARD. IN TIME...A LARGE MID TO UPPER LEVEL TROUGH IS EXPECTED TO DEVELOP OVER THE CENTRAL UNITED STATES AND THE GULF OF MEXICO. THIS TROUGH IS FORECAST TO ERODE THE RIDGE ALLOWING THE HURRICANE TO MOVE MORE TOWARD THE WEST-NORTHWEST AND NORTHWEST WITH A DECREASE IN FORWARD SPEED BY THE END OF THE FORECAST PERIOD. HOW FAR NORTH THE HURRICANE WILL MOVE DEPENDS ON THE INTENSITY OF TROUGH OVER THE GULF OF MEXICO...AND THIS VARIES WITH MODELS. THE OFFICIAL FORECAST HAS BEEN SHIFTED SOUTHWARD A LITTLE BIT AT THE END OF THE FORECAST PERIOD...TO BE IN BETTER AGREEMENT WITH THE GFDL AND THE FSU SUPERENSEMBLE. FORECASTER AVILA FORECAST POSITIONS AND MAX WINDS INITIAL 07/1500Z 11.8N 60.2W 100 KT 12HR VT 08/0000Z 12.3N 62.5W 105 KT 24HR VT 08/1200Z 13.0N 65.6W 110 KT 36HR VT 09/0000Z 14.0N 68.5W 115 KT 48HR VT 09/1200Z 15.0N 71.5W 120 KT 72HR VT 10/1200Z 17.5N 76.0W 120 KT 96HR VT 11/1200Z 19.5N 80.0W 120 KT 120HR VT 12/1200Z 22.0N 83.0W 120 KT $$ NNNN
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Page last modified: Tuesday, 07-Sep-2004 15:02:56 UTC