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| #294341 (Received by flhurricane at: 4:37 AM 09.Sep.2009) TCDAT2 HURRICANE FRED DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072009 500 AM AST WED SEP 09 2009 ENHANCED INFRARED SATELLITE IMAGES INDICATE THAT FRED HAS UNDERGONE RAPID INTENSIFICATION. THE EYE IS NOW EMBEDDED WITHIN CLOUD TOPS OF -55 DEG C OR COLDER...AND THE DATA T-NUMBER IS AT LEAST 5.0. THIS CORRESPONDS TO A CONSERVATIVE CURRENT INTENSITY ESTIMATE OF 90 KT. THE UPPER-LEVEL OUTFLOW IS WELL-DEFINED...ESPECIALLY OVER THE NORTHERN AND WESTERN PORTIONS OF THE CIRCULATION. FRED IS EXPECTED TO REMAIN IN A LOW-SHEAR ENVIRONMENT FOR THE NEXT 24 HOURS...SO SOME ADDITIONAL STRENGTHENING IS LIKELY TODAY. IN ABOUT 36 HOURS OR SO...THE GLOBAL MODELS SHOW THAT THE HURRICANE WILL BE MOVING INTO INCREASING SOUTH-SOUTHWESTERLY SHEAR ASSOCIATED WITH A LARGE UPPER-TROPOSPHERIC TROUGH OVER THE CENTRAL ATLANTIC. OVER THE NEXT FEW DAYS...FRED WILL ALSO BE MOVING OVER SLIGHTLY COOLER SEA SURFACE TEMPERATURES AND INTO A DRIER MID-LEVEL AIRMASS. THIS COMBINATION OF ENVIRONMENTAL CHANGES SHOULD BRING ABOUT WEAKENING...AND OFFICIAL FORECAST SHOWS A WEAKENING TREND COMMENCING AFTER 24 HOURS. THIS IS FAIRLY CLOSE TO THE LATEST SHIPS GUIDANCE. THE GFDL AND HWRF MODELS...WHICH SEEM TO BE LESS SENSITIVE TO INCREASED SHEAR...DO NOT WEAKEN FRED NEARLY AS MUCH AS THE STATISTICAL/DYNAMICAL GUIDANCE AT DAYS 4 AND 5. THE MOTION HAS BEEN BENDING GRADUALLY TO THE RIGHT AND IS NOW ABOUT 300/11. THE MID-LEVEL RIDGE TO THE NORTH OF THE HURRICANE HAS BEEN WEAKENING AS A MID- TO UPPER-LEVEL TROUGH APPROACHES 35W NORTH OF 20N. DURING THE NEXT 72 HOURS...FRED IS FORECAST TO TURN NORTHWARD INTO THE WEAKNESS CAUSED BY THE TROUGH AND TO DECELERATE AS THE STEERING FLOW BECOMES VERY WEAK. LATER IN THE PERIOD...THE DYNAMICAL GUIDANCE SHOWS A WEAK MID-TROPOSPHERIC RIDGE BUILDING TO THE NORTH AND NORTHEAST OF FRED AND THIS COULD EVENTUALLY BLOCK THE NORTHWARD MOTION OF THE SYSTEM. THE OFFICIAL FORECAST IS ONLY SLIGHTLY TO THE WEST OF THE PREVIOUS ONE AND NOT QUITE AS FAST AS THE MODEL CONSENSUS. THE GFDL AND HWRF TAKE FRED FARTHER NORTH THAN MOST OF THE OTHER MODELS...PROBABLY BECAUSE THEY KEEP FRED AS A DEEP CYCLONE FOR TOO LONG. FORECAST POSITIONS AND MAX WINDS INITIAL 09/0900Z 13.2N 31.7W 90 KT 12HR VT 09/1800Z 14.1N 32.7W 100 KT 24HR VT 10/0600Z 15.4N 33.9W 100 KT 36HR VT 10/1800Z 16.5N 34.3W 90 KT 48HR VT 11/0600Z 17.3N 34.5W 75 KT 72HR VT 12/0600Z 18.4N 34.2W 60 KT 96HR VT 13/0600Z 20.6N 34.0W 45 KT 120HR VT 14/0600Z 23.0N 34.5W 30 KT $$ FORECASTER PASCH |
