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| #9222 (Received by flhurricane at: 4:55 AM 19.Sep.2004) TCDAT1 TROPICAL STORM JEANNE DISCUSSION NUMBER 23 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT SUN SEP 19 2004 AN AIR FORCE HURRICANE HUNTER AIRCRAFT HAS BEEN INVESTIGATING JEANNE AND THEY FOUND PEAK FLIGHT LEVEL...1500 FT...OF 53 KT ABOUT 50 N MI NORTHEAST OF THE CENTER. USING A STANDARD REDUCTION FOR THIS ALTITUDE GIVES A MAXIMUM SURFACE WIND SPEED OF 40-45 KT. THE TROPICAL CYCLONE HAS BEEN MOVING AWAY FROM THE DISRUPTING INFLUENCE OF AN UPPER-LEVEL LOW...AND CURRENTLY SEEMS TO BE ESTABLISHING A BETTER-DEFINED UPPER-LEVEL OUTFLOW PATTERN. THEREFORE SOME STRENGTHENING IS LIKELY OVER THE NEXT COUPLE OF DAYS. THE OFFICIAL FORECAST SHOWS JEANNE EVENTUALLY RESTRENGTHENING INTO A HURRICANE... AS DO THE SHIPS AND GFDL MODELS. HOWEVER...THE GFS 200 MB WIND FOREAST SHOWS FAIRLY STRONG WESTERLY FLOW...IMPLYING SIGNIFICANT SHEAR...OVER THE AREA WHERE THE TROPICAL CYCLONE IS FORECAST TO BE LOCATED IN 72 HOURS. JEANNE MAY HAVE TO OVERCOME A RATHER HOSTILE UPPER-LEVEL ENVIRONMENT ON ITS WAY TO REGAINING HURRICANE STATUS. BASED ON THE RECON FIXES...THE INITIAL MOTION ESTIMATE IS 340/6. A MID-LEVEL TROUGH OVER THE FLORIDA PENINSUAL IS FORECAST TO MOVE EASTWARD AND TURN JEANNE NORTHWARD AND NORTH-NORTHEASTWARD DURING THE NEXT 24-36 HOURS. HOWEVER...IN 2-3 DAYS...THIS TROUGH IS LIKELY TO BYPASS THE TROPICAL CYCLONE AS AN UNUSUALLY STRONG DEEP-LAYER HIGH BUILDS OVER THE EASTERN UNITED STATES. A RIDGE EXTENDING FROM THIS HIGH IS PREDICTED...BY THE DYNAMICAL MODELS... TO BLOCK THE NORTHEASTWARD MOTION OF JEANNE...AND CAUSE THE TROPICAL CYCLONE TO EXECUTE A CLOCKWISE LOOP. THIS OFFICIAL FORECAST SHOWS A LITTLE WIDER LOOP THAN THE PREVIOUS ADVISORY...BUT HAS THE SAME GENERAL IDEA. IT SHOULD BE REPEATED THAT THIS IS A LOWER THAN NORMAL CONFIDENCE FORECAST. SINCE JEANNE IS MOVING AWAY FROM THE SOUTHEASTERN BAHAMAS AND HAS TROPICAL STORM FORCE WINDS CONFINED TO THE NORTHEAST AND SOUTHEAST QUADRANTS...THE GOVERNMENT OF THE BAHAMAS INTENDS TO DISCONTINUE WATCHES AND WARNINGS FOR THE BAHAMAS SHORTLY. FORECASTER PASCH FORECAST POSITIONS AND MAX WINDS INITIAL 19/0900Z 23.2N 72.5W 40 KT 12HR VT 19/1800Z 24.1N 72.6W 45 KT 24HR VT 20/0600Z 25.5N 72.2W 50 KT 36HR VT 20/1800Z 27.0N 71.7W 55 KT 48HR VT 21/0600Z 28.0N 70.5W 60 KT 72HR VT 22/0600Z 27.0N 70.0W 65 KT 96HR VT 23/0600Z 26.0N 70.0W 65 KT 120HR VT 24/0600Z 26.0N 71.5W 65 KT |
