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| #8020 (Received by flhurricane at: 10:44 AM 12.Sep.2004) TCDAT4 HURRICANE IVAN DISCUSSION NUMBER 41 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT SUN SEP 12 2004 THE INITIAL MOTION ESTIMATE IS 300/8. IVAN HAS REMAINED ON TRACK... SO THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK OR REASONING. THE LATEST 12Z UPPER-AIR DATA INDICATE A SHARP SHORTWAVE TROUGH OVER THE LOWER MISSISSIPPI VALLEY HAS PUSHED SOUTHEASTWARD INTO THE CENTRAL GULF OF MEXICO AND HAS ERODED THE RIDGE FROM 500 MB THROUGH THE 300 MB LEVEL. NHC MODEL GUIDANCE IS IN REASONABLE AGREEMENT ON A GRADUAL TURN TO THE NORTHWEST IN 12 TO 24 HOURS... WITH A TURN TO THE NORTH AFTER 36 HOURS WHEN IVAN IS EXPECTED TO EMERGE OVER THE GULF OF MEXICO NORTH OF WESTERN CUBA. THE OFFICIAL FORECAST TRACK IS JUST AN UPDATE OF THE PREVIOUS TRACK AND REMAINS IN THE EASTERN PORTION OF THE NHC MODEL GUIDANCE SUITE. THERE IS NO CHANGE TO THE CURRENT INTENSITY BASED ON RECENT AIR FORCE AND NOAA RECON REPORTS. THEREFORE...THERE ALSO REMAINS NO CHANGE TO THE PREVIOUS INTENSITY FORECAST TREND. IVAN REMAINS WELL ORGANIZED AND THE OUTFLOW HAS IMPROVED TO THE NORTHWEST. THERE WILL BE PERIODIC FLUCTUATIONS IN THE INTENSITY DUE TO EYEWALL REPLACEMENT CYCLES...LIKE THE ONE IVAN IS CURRENTLY GOING THROUGH...BUT LOW SHEAR AND VERY WARM SSTS AHEAD OF THE HURRICANE SHOULD AT LEAST KEEP IVAN A CATEGORY FOUR HURRICANE UNTIL EXPECTED LANDFALL OCCURS OVER WESTERN CUBA IN ABOUT 24 HOURS OR SO. BECAUSE STEERING ARE CURRENTLY WEAK AND MAY WEAKEN EVEN MORE...THERE REMAINS CONSIDERABLE UNCERTAINTY AS TO JUST WHEN AND WHERE...AND AT WHAT INTENSITY...IVAN WILL MAKE LANDFALL IN THE UNITED STATES IN THE LONGER TIME PERIODS. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 12/1500Z 19.0N 81.5W 135 KT 12HR VT 13/0000Z 19.8N 82.4W 145 KT 24HR VT 13/1200Z 21.3N 83.5W 145 KT 36HR VT 14/0000Z 22.9N 84.4W 140 KT 48HR VT 14/1200Z 24.7N 85.0W 125 KT 72HR VT 15/1200Z 28.3N 85.5W 110 KT 96HR VT 16/1200Z 32.5N 84.5W 55 KT...INLAND 120HR VT 17/1200Z 37.0N 81.5W 25 KT...INLAND |
