TROPICAL DEPRESSION TEN DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL102008 500 AM EDT TUE SEP 02 2008

SATELLITE IMAGERY INDICATES THE LARGE TROPICAL DISTURBANCE JUST SOUTH OF THE CAPE VERDE ISLANDS HAS DEVELOPED ENOUGH CONVECTIVE CURVED BAND FEATURES TO BE CLASSIFIED AS TROPICAL DEPRESSION TEN. SATELLITE INTENSITY ESTIMATES ARE T2.0/30 KT AND T2.5/35 KT FROM TAFB AND SAB...RESPECTIVELY.

THE INITIAL MOTION ESTIMATE IS 275/14. THE DEPRESSION IS EXPECTED TO MOVE IN A WEST TO WEST-NORTHWESTWARD MOTION FOR THE NEXT 24 HOURS OR SO...AND THEN TURN MORE WEST-NORTHWESTWARD AND SLOW A LITTLE BIT AS THE CYCLONE MOVES INTO A WEAKNESS IN THE SUBTROPICAL RIDGE TO THE NORTH. THE MID/UPPER-LEVEL TROUGH THAT IS EXPECTED TO WEAKEN THE RIDGE BETWEEN 30N-40 LONGITUDE IS FORECAST BY MOST OF THE GLOBAL MODELS TO WEAKEN AND LIFT OUT TO THE NORTHEAST BY 72-96 HOURS...WHICH WILL ALLOW THE RIDGE TO SLOWLY BUILD BACK IN AND TURN THE CYCLONE MORE WESTWARD BY DAYS 4 AND 5. THE OFFICIAL FORECAST IS SIMILAR TO BUT TO THE SOUTH OF THE NHC MODEL CONSENSUS TO ACCOUNT FOR WHAT APPEARS TO BE A POLEWARD BIAS BY THE GFDL AND HWRF MODELS.

THE CYCLONE IS EXPECTED TO STEADILY INTENSIFY FOR THE NEXT 24 HOURS OR SO DUE TO A VERY FAVORABLE UPPER-LEVEL FLOW REGIME. HOWEVER...BY 36-48 HOURS...ALL OF THE MODELS SUGGEST THAT SOUTHERLY VERTICAL SHEAR OF 20-30 KT WILL DEVELOP...WHICH COULD DISRUPT OR EVEN HALT THE STRENGTHENING PROCESS. SOME OF THE MODELS LIKE THE GFS COMPLETELY DISSIPATE THE CYCLONE...WHICH SEEMS UNREASONABLE AT THIS TIME GIVEN THE LARGE CIRCULATION ENVELOPE NOTED IN SATELLITE IMAGERY. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE SHIPS MODEL THROUGH 48 HOURS...AND THEN HIGHER AT 96 AND 120 HOURS DUE TO THE CYCLONE FORECAST TO REMAIN SOUTH OF 20N LATITUDE OVER WARMER WATER AND UNDER LESS SHEAR THAN THE SHIPS MODEL IS DEPICTING.