ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM HURRICANE IVAN DISCUSSION NUMBER 11 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT SUN SEP 05 2004 INFRARED SATELLITE IMAGERY AND A 0450Z TRMM OVERPASS SHOW THAT IVAN HAS DEVELOPED SUFFICIENT ORGANIZED CONVECTION AROUND THE WARM SPOT SEEN EARLIER TO NOW CALL IT AN EYE. SATELLITE INTENSITY ESTIMATES ARE 77 KT FROM AFWA AND 65 KT FROM TAFB AND SAB. THUS...IVAN IS UPGRADED TO A 65 KT HURRICANE. THE INITIAL MOTION IS NOW 280/18...AND THE SHORT-TERM MOTION MAY BE EVEN FASTER. IVAN IS ON THE SOUTH SIDE OF A STRONG SUBTROPICAL RIDGE...AND THIS SHOULD LIKELY CONTINUE FOR THE NEXT 3-4 DAYS. THIS PATTERN SHOULD ALLOW A GENERALLY WEST-NORTHWESTWARD MOTION FOR THE NEXT 3-4 DAYS...A SCENARIO SUPPORTED BY WELL-CLUSTERED TRACK GUIDANCE. THE GUIDANCE REMAINS FAIRLY WELL-CLUSTERED AROUND A WEST-NORTHWEST MOTION ON DAY 5...BUT BY THAT TIME THERE ARE SIGNIFICANT DISAGREEMENTS ON THE SYNOPTIC PATTERNS OVER THE WESTERN ATLANTIC RANGING FROM THE NOGAPS SOLID-LOOKING RIDGE TO THE GFS BROAD POST-FRANCES TROUGH. THE 120 HR POINT WILL CONTINUE A WEST-NORTHWEST MOTION...BUT THE CONFIDENCE IN THIS POINT HAS DECREASED. THE NEW FORECAST TRACK IS NUDGED A LITTLE TO THE SOUTH OF THE PREVIOUS PACKAGE BASED MAINLY ON THE INITIAL POSITION. LARGE-SCALE GUIDANCE PREDICTS LIGHT VERTICAL SHEAR FOR THE NEXT 3-4 DAYS...SO THERE IS NO OBVIOUS REASON WHY IVAN SHOULD NOT INTENSIFY FURTHER. THE INTENSITY FORECAST FOLLOWS THIS PHILOSOPHY...AND IT IS POSSIBLE THERE COULD BE RAPID STRENGTHENING. WITH THE FORECAST TRACK TAKING THE STORM OVER HISPANIOLA BETWEEN 96-120 HR...THE FORECAST INTENSITY IS CONSIDERABLY REDUCED. THERE IS ALSO SOME UNCERTAINTY OF WHETHER THE SHEAR WILL REMAIN FAVORABLE AFTER 96 HR...AS THE GFS IN PARTICULAR SHOWS THE UPPER-LEVEL WINDS BECOMING LESS FAVORABLE. AS NOTED EARLIER...BECAUSE OF THE TYPICAL TRACK FORECAST ERRORS AT 4-5 DAYS...THE CENTER COULD EASILY PASS SOUTH...OR NORTH...OF THE ISLAND OF HISPANIOLA. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 05/0900Z 9.7N 44.3W 65 KT 12HR VT 05/1800Z 10.3N 47.1W 70 KT 24HR VT 06/0600Z 11.3N 50.6W 75 KT 36HR VT 06/1800Z 12.2N 54.1W 80 KT 48HR VT 07/0600Z 13.1N 57.5W 85 KT 72HR VT 08/0600Z 14.5N 63.5W 95 KT 96HR VT 09/0600Z 17.0N 69.0W 105 KT 120HR VT 10/0600Z 20.5N 73.5W 70 KT $$ NNNN
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Page last modified: Sunday, 05-Sep-2004 08:42:52 GMT