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| #294143 (Received by flhurricane at: 4:43 AM 08.Sep.2009) TCDAT2 TROPICAL STORM FRED DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072009 500 AM AST TUE SEP 08 2009 FRED IS GRADUALLY BECOMING BETTER ORGANIZED IN SATELLITE IMAGES. THE STORM IS EXHIBITING A WELL-DEFINED CURVED BAND FEATURE WRAPPING AROUND A DEVELOPING CENTRAL DENSE OVERCAST. BASED ON THE BANDING...DVORAK DATA T-NUMBERS ARE AT LEAST 3.0. THE CURRENT INTENSITY ESTIMATE IS 45 KT FROM BOTH TAFB MIAMI AND SAB WASHINGTON...AND THE ADVISORY INTENSITY IS ALSO SET AT 45 KT. CIRRUS MOTIONS INDICATE STRONG UPPER-LEVEL OUTFLOW IN ALL QUADRANTS OF THE SYSTEM. VERTICAL SHEAR IS EXPECTED TO REMAIN WEAK FOR THE NEXT DAY OR TWO...SO ADDITIONAL INTENSIFICATION SEEMS LIKELY. GIVEN THE CURRENT ORGANIZATION AND FAVORABLE SHORT-TERM ENVIRONMENT...FRED CERTAINLY HAS THE POTENTIAL TO BECOME A HURRICANE WITHIN THE NEXT 36 HOURS. THE OFFICIAL INTENSITY FORECAST IS QUITE CLOSE TO THE SHIPS AND LGEM GUIDANCE THROUGH DAY 3. BEYOND THAT TIME...A LARGE UPPER-TROPOSPHERIC TROUGH OVER THE CENTRAL ATLANTIC SHOULD PRODUCE INCREASING SOUTHWESTERLY SHEAR OVER FRED. THAT...ALONG WITH A SLIGHTLY COOLER OCEAN...WILL PROBABLY INDUCE WEAKENING. THE OFFICIAL FORECAST FOR DAYS 4 AND 5 DOES NOT WEAKEN THE CYCLONE QUITE AS FAST AS INDICATED BY SOME OF THE GUIDANCE. LATEST CENTER FIXES INDICATE A CONTINUED WESTWARD MOTION AT AROUND 275/13. THE NARROW MID-TROPOSPHERIC RIDGE CURRENTLY TO THE NORTH OF FRED IS FORECAST BY THE GLOBAL MODELS TO BECOME ERODED OVER THE NEXT COUPLE OF DAYS BY A MID-TO UPPER-LEVEL LOW CURRENTLY SEEN IN WATER VAPOR IMAGES NEAR 28N AND 40W. THIS EVOLUTION SHOULD CAUSE FRED TO GRADUALLY TURN NORTHWESTWARD AND NORTHWARD OVER THE EASTERN ATLANTIC. NEAR THE END OF THE FORECAST PERIOD...THE GLOBAL MODELS SHOW WEAK RIDGING DEVLOPING AGAIN TO THE NORTH OF THE TROPICAL CYCLONE. IN RESPONSE TO THIS...SOME OF THE TRACK MODELS TURN THE SYSTEM TOWARD THE NORTHWEST BY DAY 5 WITH A VERY SLOW FORWARD SPEED. THE OFFICIAL FORECAST SHOWS A SLOWING OF THE FORWARD SPEED THROUGH THE PERIOD AND HINTS AT A SLIGHT TURN TO THE LEFT AT 96-120 HOURS. THE GFDL AND HWRF MODELS TAKE FRED MUCH FARTHER NORTH IN 5 DAYS...BUT ARE BEING TREATED AS OUTLIERS FOR THE TIME BEING. FORECAST POSITIONS AND MAX WINDS INITIAL 08/0900Z 11.8N 27.3W 45 KT 12HR VT 08/1800Z 12.1N 29.0W 55 KT 24HR VT 09/0600Z 13.0N 30.9W 60 KT 36HR VT 09/1800Z 13.9N 32.5W 65 KT 48HR VT 10/0600Z 15.1N 33.5W 65 KT 72HR VT 11/0600Z 17.5N 34.0W 60 KT 96HR VT 12/0600Z 19.0N 34.0W 55 KT 120HR VT 13/0600Z 20.5N 34.5W 55 KT $$ FORECASTER PASCH |
