ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM JEANNE DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT WED SEP 15 2004 SAN JUAN RADAR DEPICTS A TIGHT CIRCULATION AND A WELL-DEFINED OUTER CURVED BAND IN THE SOUTHEASTERN SEMICIRCLE....AND SATELLITE IMAGERY INDICATES THE CIRCULATION LIES WELL WITHIN THE MASS OF DEEP CONVECTION AND ALSO REVEALS THE OUTER CURVED BAND. DVORAK INTENSITY ESTIMATES ARE 55 KT FROM BOTH TAFB AND SAB. OUTFLOW IS GOOD IN ALL DIRECTIONS EXCEPT THE WEST. BASED ON THE IMPROVING SATELLITE AND RADAR PRESENTATION...THE INITIAL INTENSITY IS INCREASED TO 55 KT. AIRCRAFT RECONNAISSANCE WILL NOT BE AVAILABLE FOR JEANNE UNTIL 18Z TODAY. THE INITIAL MOTION...BASED PRIMARILY ON TRACKING A POORLY-DEFINED CENTER ON SAN JUAN RADAR...IS ESTIMATED AT 295/7. JEANNE IS CURRENTLY ON THE SOUTHERN PERIPHERY OF A DEEP LAYER RIDGE...AND MODEL GUIDANCE AGREES THAT THIS RIDGE SHOULD PERSIST AND MOVE JEANNE ON A CONTINUED WEST-NORTHWEST MOTION THROUGH ABOUT 48 HOURS. BEYOND THAT TIME...THE SOLUTIONS DIVERGE...OWING TO DIFFERENCES IN HOW EACH MODEL HANDLES A WEAKENING IVAN OVER THE SOUTHEASTERN UNITED STATES AND HOW MUCH RIDGING WILL REMAIN OVER THE EXTREME WESTERN ATLANTIC. THE GFS HAS NOW MOVED MORE TO THE WEST IN BETTER AGREEMENT WITH THE REMAINDER OF THE GUIDANCE SUITE...BUT THE GFDL HAS ALSO MOVED FARTHER LEFT AND IS NOW THE WESTERN OUTLIER. AS A RESULT...THE CONSENSUS OF THE MODELS HAS NUDGED SLIGHTLY WESTWARD AT DAYS THREE THROUGH FIVE...AND THE OFFICIAL FORECAST IS ALSO ADJUSTED JUST SLIGHTLY WEST...AND A BIT FASTER THAN...THE PREVIOUS ADVISORY. THE INTENSITY FORECAST IS A CHALLENGE. THROUGH 36 HOURS...MODEL GUIDANCE SUGGESTS ENOUGH ANTICYCLONIC FLOW ALOFT TO SUPPORT INTENSIFICATION...BUT INTERACTION WITH LAND WILL LIKELY LIMIT THE INTENSIFICATION RATE. ONCE JEANNE EMERGES NORTH OF THE GREATER ANTILLES...IT MAY STRUGGLE UNDER STRONGER NORTHERLY SHEAR. HOWEVER...BOTH THE SHIPS AND GFDL GUIDANCE INSIST JEANNE WILL SURVIVE THE SHEAR...UNTIL CONDITIONS BECOME MORE FAVORABLE VERY LATE IN THE FORECAST PERIOD. THEREFORE...THE OFFICIAL FORECAST INDICATES SLOW INTENSIFICATION FOR THE FIRST 36 HOURS...LEVELLING OFF THROUGH 72 HOURS...THEN RESUMING GRADUAL STRENGTHENING ON DAYS FOUR AND FIVE. FORECASTER KNABB/AVILA FORECAST POSITIONS AND MAX WINDS INITIAL 15/0900Z 17.5N 65.1W 55 KT 12HR VT 15/1800Z 18.1N 66.5W 60 KT...OVER PUERTO RICO 24HR VT 16/0600Z 19.1N 68.2W 65 KT 36HR VT 16/1800Z 20.0N 69.9W 65 KT 48HR VT 17/0600Z 20.8N 71.3W 65 KT 72HR VT 18/0600Z 22.5N 74.0W 70 KT 96HR VT 19/0600Z 24.5N 76.0W 75 KT 120HR VT 20/0600Z 27.0N 77.5W 80 KT $$ NNNN
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Page last modified: Wednesday, 15-Sep-2004 09:03:41 UTC