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| #9189 (Received by flhurricane at: 10:40 PM 18.Sep.2004) TCDAT1 TROPICAL STORM JEANNE DISCUSSION NUMBER 22 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT SAT SEP 18 2004 SATELLITE IMAGERY AND REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INDICATE THAT JEANNE IS POORLY ORGANIZED...POSSIBLY DUE TO INTERACTION WITH AN UPPER-LEVEL LOW SEEN IN WATER VAPOR IMAGERY JUST SOUTH OF THE STORM. THE CIRCULATION IS ELONGATED FROM THE NEW CENTER THAT FORMED THIS AFTERNOON TO THE OLD CENTER...WHICH HAS MOVED EASTWARD AND IS NOW BETWEEN GREAT INAGUA ISLAND AND HAITI. THE STRONGEST CONVECTION IS CURRENTLY WELL-REMOVED TO THE EAST OF THE CENTER. THE AIRCRAFT FOUND A MINIMUM PRESSURE OF 1002 MB AND MAXIMUM FLIGHT-LEVEL WINDS OF 44 KT WELL TO THE NORTHEAST OF THE NEW CENTER. BASED ON THIS...THE MAXIMUM INTENSITY REMAINS 40 KT...ALTHOUGH THIS MAY BE GENEROUS. THE INITIAL MOTION IS A HIGHLY UNCERTAIN 360/5. IF JEANNE IS NOT ACTUALLY YET MOVING NORTH...IT WILL BE SOON AS SATELLITE... RAWINSONDE...AND SURFACE OBSERVATIONS SHOW A WEAK BUT DEEP-LAYER TROUGH HAS DEVELOPED OVER FLORIDA IN ASSOCIATION WITH THE REMNANTS OF IVAN. THIS HAS ERODED THE RIDGE NORTH AND NORTHWEST OF JEANNE AND SHOULD ALLOW A NORTHWARD MOTION. LARGE-SCALE MODELS SUGGEST THIS SHOULD CONTINUE FOR 48 HR OR SO...THEN POSSIBLY BECOME A NORTH-NORTHEASTWARD MOTION. THE FIRST 72 HR OF THE FORECAST TRACK FOLLOWS THIS SCENARIO...BEING A LITTLE SLOWER THAN AND ALONG THE LEFT SIDE OF THE ENVELOPE OF DYNAMICAL MODELS. AFTER 72 HR...THE LARGE-SCALE MODELS FORECAST A DEEP-LAYER RIDGE TO BUILD NORTH AND NORTHWEST OF JEANNE IN THE WAKE OF A DEEP-LAYER TROUGH MOVING THROUGH THE CANADIAN ATLANTIC PROVINCES. THIS SHOULD BLOCK THE NORTHWARD MOTION AND COULD TURN JEANNE BACK WESTWARD BY 120 HR. DYNAMICAL GUIDANCE CALLS FOR LOOPS OF VARIOUS SIZES AND SPEEDS... WITH 120 HR POSITIONS BETWEEN 67W AND 76W. THE FORECAST TRACK FOR 72-120 HR WILL NOT CALL FOR A COMPLETE LOOP...BUT WILL SHOW A HALF-LOOP THAT IS SMALLER AND SLOWER THAN THAT OF THE GUIDANCE. OBVIOUSLY...THE 96 AND 120 HR FORECASTS HAVE A HIGHER THAN NORMAL LEVEL OF UNCERTAINTY. THE INTENSITY FORECAST ALSO HAS HIGH UNCERTAINTY. IN THE SHORT TERM...THE BROAD CIRCULATION AND THE LACK OF DEEP CONVECTION NEAR THE CENTER WILL AT LEAST SLOW INTENSIFICATION. UPPER-LEVEL WINDS SHOULD BECOME MORE FAVORABLE FOR DEVELOPMENT IN ABOUT 24 HR...BUT BY THAT TIME JEANNE MAY BE PASSING OVER THE SEA SURFACE TEMPERATURE WAKE OF FRANCES...WHERE SST ANALYSES INDICATE TEMPERATURES BELOW 28C IN SOME AREAS. THIS MAY COUNTER THE OTHERWISE FAVORABLE ENVIRONMENT. AFTER 48-72 HR...SHEAR IS FORECAST TO INCREASE AND JEANNE MAY INTERACT WITH A COLD FRONT...BOTH OF WHICH WOULD LIMIT STRENGTHENING. THE SHIPS AND GFDL MODELS BOTH TAKE JEANNE TO 65-70 KT MAXIMUM WINDS IN 48-72 HR FOLLOWED BY LITTLE CHANGE IN STRENGTH...AND THE INTENSITY FORECAST FOLLOWS THIS. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 19/0300Z 22.4N 72.3W 40 KT 12HR VT 19/1200Z 23.4N 72.5W 40 KT 24HR VT 20/0000Z 24.8N 72.5W 45 KT 36HR VT 20/1200Z 26.3N 72.2W 50 KT 48HR VT 21/0000Z 27.4N 71.8W 60 KT 72HR VT 22/0000Z 28.0N 71.0W 65 KT 96HR VT 23/0000Z 27.5N 70.5W 65 KT 120HR VT 24/0000Z 27.0N 71.0W 65 KT |
