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Chill falls over the Atlantic as the official season heads towards close
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| #8075 (Received by flhurricane at: 10:46 PM 12.Sep.2004) TCDAT4 HURRICANE IVAN DISCUSSION NUMBER 43 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT SUN SEP 12 2004 AIR FORCE RECON THIS EVENING FOUND A PEAK FLIGHT-LEVEL...700 MB...WIND OF 155 KT IN THE NORTHWEST EYEWALL OF THE HURRICANE. THIS OBSERVATION SUPPORTS A CURRENT INTENSITY OF 140 KT...SO IVAN HAS REGAINED CATEGORY 5 STATUS. SOME FLUCTUATIONS IN STRENGTH ARE LIKELY OVER THE NEXT DAY OR SO...AND IF THE EYEWALL PASSES OVER PORTIONS OF EXTREME WESTERN CUBA A SLIGHT REDUCTION IN INTENSITY MAY OCCUR. THE INTENSITY FORECAST FOR IVAN OVER THE GULF OF MEXICO IS MOST PROBLEMATIC. DATA FROM THE NOAA G-IV JET SHOW WESTERLY UPPER-TROPOSPHERIC FLOW OVER THE SOUTHEASTERN GULF OF MEXICO... WHICH WOULD CAUSE AN INCREASE IN SHEAR OVER IVAN ONCE IT ENTERS THE GULF. ALSO...ANALYSES FROM THE UNIVERSITY OF WISCONSIN CIMSS SHOWS EVEN MORE WESTERLY SHEAR OVER THE NORTHEASTERN GULF OF MEXICO THAN OVER THE SOUTHEASTERN GULF. HOWEVER THE GFS MODEL 200 MB WIND FORECAST SHOWS THE OUTFLOW OF THE HURRICANE DOMINATING THE CIRCULATION OVER THE EASTERN GULF IN 2-3 DAYS...AND THE LATEST SHIPS MODEL RUN SHOWS LESS VERTICAL SHEAR AT THIS TIME FRAME THAN IN EARLIER RUNS. WE ARE ASSUMING THAT SHEAR WILL PLAY SOME ROLE IN WEAKENING THE HURRICANE BEFORE LANDFALL. NONETHELESS IVAN IS EXPECTED TO BE A POWERFUL AND DANGEROUS HURRICANE WHEN IT REACHES THE UNITED STATES COAST. THE EYE CONTINUES TO WOBBLE ALONG A GENERALLY WEST-NORTHWESTWARD HEADING...300/8. THERE IS NOT MUCH CHANGE TO THE TRACK FORECAST REASONING. A SHORTWAVE TROUGH NEAR THE LOWER MISSISSIPPI RIVER VALLEY IS ERODING THE RIDGE TO THE NORTH AND NORTHEAST OF IVAN. THIS SHOULD INDUCE A TURN TO THE NORTHWEST VERY SOON. BY AROUND 48 HOURS...IT IS EXPECTED THAT IVAN WILL BE MOVING NORTHWARD THROUGH THE WEAKNESS IN THE RIDGE OVER THE EASTERN GULF OF MEXICO. COMPARED TO YESTERDAY...THERE HAS BEEN INCREASE IN THE DYNAMICAL MODEL SPREAD BEYOND 48 HOURS. THE OFFICIAL FORECAST IS SHIFTED A LITTLE MORE TO THE WEST BUT IS EAST OF THE CONSENSUS TRACK...AND LEANS TOWARD THE GFDL AND GFS SOLUTIONS. FORECASTER PASCH FORECAST POSITIONS AND MAX WINDS INITIAL 13/0300Z 19.7N 83.2W 140 KT 12HR VT 13/1200Z 20.8N 84.1W 140 KT 24HR VT 14/0000Z 22.3N 85.0W 135 KT 36HR VT 14/1200Z 23.9N 85.9W 135 KT 48HR VT 15/0000Z 25.8N 86.5W 125 KT 72HR VT 16/0000Z 30.0N 86.5W 115 KT 96HR VT 17/0000Z 34.0N 84.5W 45 KT...INLAND 120HR VT 18/0000Z 37.0N 82.0W 20 KT...INLAND |
