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#635201 (Received by flhurricane at: 11:01 PM 28.Sep.2013) TCDAT1 TROPICAL DEPRESSION ELEVEN DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112013 1100 PM AST SAT SEP 28 2013 THE WELL-DEFINED AREA OF LOW PRESSURE OVER THE CENTRAL ATLANTIC HAS DEVELOPED ENOUGH ORGANIZED DEEP CONVECTION TO BE CLASSIFIED AS A TROPICAL DEPRESSION...THE ELEVENTH ONE OF THE ATLANTIC HURRICANE SEASON. THE INITIAL WIND SPEED IS SET AT 30 KT BASED ON EARLIER SCATTEROMETER DATA. THE DEPRESSION IS MOVING NORTHWARD AT ABOUT 8 KT ON THE WEST SIDE OF A DEEP-LAYER RIDGE. THIS SUBTROPICAL RIDGE IS EXPECTED TO WEAKEN SOON AS A LARGE TROUGH AMPLIFIES OVER THE NORTH ATLANTIC...CAUSING THE CYCLONE TO TURN NORTHEASTWARD OVERNIGHT AND THEN EASTWARD LATE SUNDAY. THE TROUGH IS NOT EXPECTED TO ABSORB OR PICK UP THE DEPRESSION...INSTEAD THE MODELS ARE IN GOOD AGREEMENT IN SHOWING THE CYCLONE BEING LEFT BEHIND IN WEAK STEERING CURRENTS FOR AT LEAST A FEW DAYS. THE NEXT SUBSTANTIAL INFLUENCE ON THE STEERING FLOW WILL LIKELY BE ANOTHER TROUGH THAT WILL BE APPROACHING THE DEPRESSION AROUND THE MIDDLE PORTION OF NEXT WEEK. THE NHC FORECAST SHOWS THE SYSTEM MAKING A CLOCKWISE LOOP AND LIES CLOSE TO THE DYNAMICAL MODEL CONSENSUS THROUGH THE FORECAST PERIOD. THE DEPRESSION IS CURRENTLY BEING AFFECTED BY ABOUT 15 KT OF SOUTHERLY SHEAR...WHICH HAS DISPLACED MUCH OF THE ASSOCIATED CONVECTION TO THE NORTH OF THE CENTER. THE SHEAR IS EXPECTED TO LESSEN DURING THE NEXT 24 HOURS...WHICH SHOULD ALLOW THE DEPRESSION STRENGTHEN A LITTLE. AFTER THAT TIME...HOWEVER...AN INCREASE IN NORTHWESTERLY SHEAR AND DRIER AIR ARE EXPECTED TO END THE STRENGTHENING TREND AND LIKELY INDUCE WEAKENING. THE NHC WIND SPEED FORECAST IS NEAR THE INTENSITY MODEL CONSENSUS IN THE SHORT TERM AND THEN LIES ON THE LOW SIDE OF THE GUIDANCE GIVEN THE ANTICIPATED HOSTILE ENVIRONMENTAL CONDITIONS. FORECAST POSITIONS AND MAX WINDS INIT 29/0300Z 25.2N 50.2W 30 KT 35 MPH 12H 29/1200Z 26.1N 49.4W 35 KT 40 MPH 24H 30/0000Z 27.0N 48.3W 40 KT 45 MPH 36H 30/1200Z 27.1N 47.0W 40 KT 45 MPH 48H 01/0000Z 26.6N 46.5W 40 KT 45 MPH 72H 02/0000Z 26.2N 47.5W 35 KT 40 MPH 96H 03/0000Z 27.2N 49.0W 35 KT 40 MPH 120H 04/0000Z 29.5N 47.5W 30 KT 35 MPH $$ FORECASTER CANGIALOSI |