ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM JEANNE DISCUSSION NUMBER 27 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT MON SEP 20 2004 JEANNE HAS NOT CHANGED SIGNIFICANTLY IN ORGANIZATION OVER THE PAST SEVERAL HOURS. PEAK FLIGHT-LEVEL WINDS FROM THE AIR FORCE HURRICANE HUNTER AIRCRAFT ARE ABOUT THE SAME AS ON THE LAST RECON MISSION...ALTHOUGH THE CENTRAL PRESSURE IS DOWN A COUPLE OF MILLIBARS. CURRENT INTENSITY IS HELD AT 50 KT. THE HURRICANE HUNTERS FIXED THE CENTER OF THE STORM NEAR THE SOUTHERN PORTION OF THE CONVECTIVE OVERCAST...AND SATELLITE ANALYSTS FROM TAFB...SAB... AND AFWA LOCATED THE CENTER SLIGHTLY FARTHER NORTH. ON SATELLITE IMAGES...THE CLOUD PATTERN IS BECOMING A LITTLE ELONGATED FROM SOUTHWEST TO NORTHEAST. THIS IS INDICATIVE OF SOME SOUTHWESTERLY SHEAR OVER THE SYSTEM...AND ANALYSES FROM THE UNIVERSITY OF WISCONSIN CIMSS INDICATE A LITTLE OVER 15 KT OF VERTICAL SHEAR IN THE AREA. SOME STRENGTHENING IS FORECAST AS PER THE PREVIOUS ADVISORIES AND THE LATEST SHIPS GUIDANCE. A FURTHER INCREASE IN SHEAR AND DRIER AIR IS LIKELY TO HALT THE INTENSIFICATION PROCESS IN A COUPLE OF DAYS. HOWEVER...IF THE SHEAR INCREASES SIGNIFICANTLY AND SOONER THAN EXPECTED...JEANNE MIGHT NOT REGAIN HURRICANE STATUS AFTER ALL. THE ESTIMATED INITIAL MOTION CONTINUES TO BE A LITTLE EAST OF NORTH...010/7. THE STORM IS CURRENTLY BEING STEERED BY THE FLOW BETWEEN A WEAK MID-LEVEL TROUGH TO ITS NORTHWEST AND A RIDGE TO ITS EAST. THERE IS A MUCH LARGER AND STRONGER TROUGH TO THE NORTH-NORTHEAST OF JEANNE...AND THE GFS MODEL PREDICTS THAT THE TROPICAL CYCLONE WILL BE ENTRAINED INTO THE FLOW ON THE SOUTH SIDE OF THIS BIGGER TROUGH...AND MOVE WELL EAST INTO THE OPEN ATLANTIC BY THE END OF THE FORECAST PERIOD. THE GFDL...U.K. MET...AND NOGAPS MODELS DO NOT AGREE WITH THAT SCENARIO...AND SHOW THE LARGE TROUGH LEAVING JEANNE BEHIND. THOSE MODELS DEPICT VARIOUS VERSIONS OF A LOOP BACK TO THE WEST...WITH THE TROPICAL CYCLONE FEELING THE INFLUENCE OF A STRONG MID-TROPOSPHERIC HIGH OVER THE EASTERN UNITED STATES. AS HAS BEEN THE CASE FOR SOME TIME NOW...THERE IS CONSIDERABLE UNCERTAINTY IN THE FORECAST TRACK FOR JEANNE IN THE 2-5 DAY TIME FRAME. THIS OFFICIAL TRACK FORECAST IS A COMPROMISE OF THE VARIOUS MODEL SOLUTIONS...AND SIMPLY HOLDS THE SYSTEM STATIONARY AFTER DAY 3. FORECASTER PASCH FORECAST POSITIONS AND MAX WINDS INITIAL 20/0900Z 26.0N 71.9W 50 KT 12HR VT 20/1800Z 26.7N 71.4W 55 KT 24HR VT 21/0600Z 27.3N 70.5W 60 KT 36HR VT 21/1800Z 27.3N 69.5W 65 KT 48HR VT 22/0600Z 27.0N 68.7W 70 KT 72HR VT 23/0600Z 26.5N 68.0W 70 KT 96HR VT 24/0600Z 26.5N 67.5W 65 KT 120HR VT 25/0600Z 26.5N 67.5W 60 KT $$ NNNN
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Page last modified: Monday, 20-Sep-2004 08:33:22 UTC