ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM HURRICANE JEANNE DISCUSSION NUMBER 31 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT TUE SEP 21 2004 REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INDICATE THAT THE CENTRAL PRESSURE OF JEAN HAS FALLEN TO 972 MB...WITH MAXIMUM FLIGHT-LEVEL WINDS OF 93 KT AT 850 MB IN THE SOUTHWEST QUADRANT. THE AIRCRAFT ALSO REPORTED A 45 NM WIDE EYE...OPEN TO THE SOUTH...WHICH SATELLITE IMAGERY INDICATES IS MOSTLY CLOUDED OVER. SATELLITE INTENSITY ESTIMATES ARE 77 KT FROM TAFB AND SAB...AND 65 KT FROM AFWA. THE INITIAL INTENSITY IS INCREASED TO 80 KT BASED MAINLY ON THE 11 MB PRESSURE FALL SINCE THE LAST RECONNAISSANCE MISSION. THE INITIAL MOTION IS 070/5. ALL GUIDANCE AGREES THAT JEANNE SHOW SLOW AND TURN SOUTHEASTWARD DURING THE NEXT 24 HR OR SO AS A HIGH PRESSURE RIDGE BUILDS TO THE NORTH. AFTER THAT...MODEL DIVERGENCE IS AGAIN PRESENT. THE GFS STILL WANT TO TAKE JEANNE OFF TO THE EAST. ON THE OTHER HAND...THE UKMET AND NOGAPS HAVE SHIFTED CONSIDERABLY TO THE WEST OF THEIR PREVIOUS FORECASTS...CALLING FOR JEANNE TO LOOP WESTWARD BEFORE TURNING NORTHWESTWARD BY DAY 5. IT SHOULD BE NOTED THAT NEITHER OF THESE MODELS INITIALLY MOVE JEANNE AS FAR EAST AS IT IS NOW. THE GFDL IS IN BETWEEN THESE EXTREMES... CALLING FOR A LESS DRASTIC WESTWARD MOTION DURING THE LOOP. THE OFFICIAL FORECAST WILL CHANGE PHILOSOPHY TO THAT A LOOP WESTWARD AND THEN NORTHWESTWARD BY DAY 5...BUT NOT AS FAR WEST AS THE UKMET AND THE NOGAPS. THIS LOW CONFIDENCE FORECAST TRACK IS IN BEST AGREEMENT WITH THE GFDL AND GUNA. ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN INDICATES 20 KT OF WEST-SOUTHWESTERLY SHEAR ACROSS JEANNE AT THIS TIME. THIS SUGGESTS THAT THE OBSERVED DEEPENING SHOULD SOON CEASE IF IT HAS NOT ALREADY DONE SO. THE SHIPS MODEL INDICATES THE SHEAR SHOULD PERSIST FOR 24-36 HR AND THEN GRADUALLY SUBSIDE. THIS COULD ALLOW SOME ADDITIONAL STRENGTHENING IF JEANNE DOES NOT SHEAR OFF BEFORE THEN...INGEST THE AIR BEHIND THE COLD FRONT JUST TO THE NORTH...OR UPWELL COLD WATER UNDERNEATH IT WHILE MAKING ITS SLOW LOOP. THE INTENSITY FORECAST WILL CALL FOR SLIGHT STRENGTHENING AT 48 HR ON THE ASSUMPTION THAT NONE OF THESE THINGS WILL HAPPEN. AFTER 72 HR...SHIPS FORECASTS AN INCREASE IN SHEAR. HOWEVER...LARGE-SCALE MODELS HAVE A VARIETY OF SOLUTIONS FOR THE UPPER-LEVEL WINDS NEAR JEANNE AT THAT TIME RANGING FROM FAVORABLE TO UNFAVORABLE...AND IT IS UNCLEAR AT THIS TIME WHICH MODEL HAS THE BEST GRASP OF THE EVOLUTION. THE INTENSITY FORECAST WILL THUS LEAN ON THE SHIPS MODEL AND CALL FOR WEAKENING AT 96-120 HR. THE INTENSITY FORECAST REMAINS LOW CONFIDENCE. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 21/0900Z 27.6N 70.0W 80 KT 12HR VT 21/1800Z 27.6N 69.6W 80 KT 24HR VT 22/0600Z 27.1N 69.3W 80 KT 36HR VT 22/1800Z 26.5N 69.5W 80 KT 48HR VT 23/0600Z 26.3N 70.0W 85 KT 72HR VT 24/0600Z 26.6N 71.0W 85 KT 96HR VT 25/0600Z 27.5N 72.0W 75 KT 120HR VT 26/0600Z 29.0N 73.0W 65 KT $$ NNNN
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Page last modified: Tuesday, 21-Sep-2004 08:33:33 UTC