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| #152352 (Received by flhurricane at: 10:37 PM 24.Sep.2007) TCDAT2 TROPICAL DEPRESSION TWELVE DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122007 1100 PM EDT MON SEP 24 2007 THE LARGE LOW PRESSURE AREA IN THE EASTERN ATLANTIC HAS ACQUIRED ENOUGH ORGANIZATION TO BE CLASSIFIED AS A TROPICAL DEPRESSION. A 2004 UTC QUIKSCAT OVERPASS WAS HELPFUL IN LOCATING THE CENTER OF THE DEPRESSION AND THE QUIKSCAT DATA SUGGEST THAT THE MAXIMUM WINDS WERE AROUND 25 KT AT THAT TIME. SINCE THEN...DEEP CONVECTION HAS INCREASED NEAR THE CENTER AND DVORAK CLASSIFICATIONS FROM TAFB AND SAB SUPPORT TROPICAL STORM STRENGTH. HOWEVER...THERE WAS SOME SPREAD IN THE CENTER LOCATION OF THESE ESTIMATES...SO THE INITIAL INTENSITY IS SET AT 30 KT. THE INITIAL MOTION ESTIMATE IS 285/14. THE DEPRESSION IS EXPECTED TO CONTINUE MOVING WEST-NORTHWESTWARD SOUTH OF A MID-LEVEL RIDGE OVER THE CENTRAL AND EASTERN ATLANTIC DURING THE NEXT FEW DAYS. A WEAKNESS IN THE RIDGE IS FORECAST TO DEVELOP OVER THE CENTRAL ATLANTIC IN 4 OR 5 DAYS...WHICH SHOULD ALLOW FOR A NORTHWESTWARD TURN LATER IN THE FORECAST PERIOD. THE DYNAMICAL MODEL GUIDANCE GENERALLY AGREES ON THIS SCENARIO...BUT THERE IS SOME SPREAD IN HOW FAR WEST THE CYCLONE WILL BE WHEN THE TURN MATERIALIZES. THE GFS...AND GFDL ARE FARTHER WEST...WHILE THE NOGAPS AND ECMWF ARE ALONG THE EASTERN SIDE OF THE GUIDANCE. THE OFFICIAL FORECAST IS ALONG THE SOUTHERN SIDE OF THE GUIDANCE ENVELOPE AND LEANS CLOSER TO THE GFS/GFDL SOLUTIONS. THE INTENSITY FORECAST IS SOMEWHAT PROBLEMATIC. THE DEPRESSION APPEARS TO BE IN A FAVORABLE ENVIRONMENT FOR STRENGTHENING DURING THE NEXT COUPLE OF DAYS. THE SHIPS MODEL BRINGS THE DEPRESSION TO HURRICANE STATUS IN 48 HOURS WHILE THE DYNAMICAL MODEL GUIDANCE IS LESS AGGRESSIVE DURING THIS TIME FRAME. BEYOND 72 HOURS...THE GLOBAL MODELS INDICATE THAT SOUTH TO SOUTHWESTERLY SHEAR WILL INCREASE...WHICH SHOULD HALT ADDITIONAL STRENGTHENING. THE OFFICIAL INTENSITY FORECAST IS MORE CONSERVATIVE THAN THE SHIPS GUIDANCE AND IS CLOSER TO THE GFDL INTENSITY FORECAST. FORECAST POSITIONS AND MAX WINDS INITIAL 25/0300Z 10.1N 36.2W 30 KT 12HR VT 25/1200Z 10.6N 38.4W 35 KT- 24HR VT 26/0000Z 11.2N 41.4W 45 KT 36HR VT 26/1200Z 11.8N 44.5W 50 KT 48HR VT 27/0000Z 12.5N 47.4W 55 KT 72HR VT 28/0000Z 15.3N 50.9W 60 KT 96HR VT 29/0000Z 19.0N 53.0W 60 KT 120HR VT 30/0000Z 22.0N 54.5W 60 KT $$ FORECASTER BROWN |
