ZCZC MIATCDEP3 ALL TTAA00 KNHC DDHHMM TROPICAL DEPRESSION THIRTEEN-E DISCUSSION NUMBER 2 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132012 200 AM PDT SAT SEP 22 2012 CONVENTIONAL SATELLITE IMAGERY AND MICROWAVE DATA INDICATE THAT THE CLOUD PATTERN IS GRADUALLY BECOMING BETTER ORGANIZED. THE CONVECTION IS RAGGED NEAR THE CENTER...BUT THERE ARE BANDING FEATURES DEVELOPING IN ALL QUADRANTS. THE OUTFLOW IS FAIR INDICATING THAT THE SHEAR IS LOW. IN FACT...SHIPS MODEL MAINTAINS VERY LOW SHEAR THROUGH 5 DAYS. THE INITIAL INTENSITY IS KEPT AT 30 KNOTS BASED ON THE AVERAGE OF DVORAK T-NUMBERS. DUE TO THE LOW SHEAR ENVIRONMENT AND THE WARM OCEAN...STRENGTHENING IS FORECAST. BY THE END OF THE FORECAST PERIOD...THE CIRCULATION WILL BE NEARING COOL WATERS AND A GRADUAL WEAKENING SHOULD THEN BEGIN. THE INITIAL MOTION IS A LITTLE BIT UNCERTAIN SINCE THE CENTER IS STILL IN FORMATIVE STAGE. THE BEST ESTIMATE IS 280 DEGREES AT 6 KNOTS. THE DEPRESSION IS SOUTH OF A SUBTROPICAL RIDGE CENTERED ACROSS NORTHERN MEXICO AND THE SOUTHWESTERN UNITED STATES. THE FLOW AROUND THE RIDGE WILL STEER THE CYCLONE ON A GENERAL WEST-NORTHWEST TO NORTHWEST TRACK FOR THE NEXT 3 DAYS. AFTER THAT...AN EASTWARD MOVING SHORTWAVE WILL ERODE THE RIDGE...AND THE CYCLONE SHOULD TURN MORE THE NORTH WITH A DECREASE IN FORWARD SPEED. THE NHC FORECAST HAS BEEN SHIFTED A LITTLE BIT TO THE NORTH AND EAST FROM THE PREVIOUS ONE. THIS IS BASED ON THE FACT THAT BOTH THE GFS AND THE ECMWF GLOBAL MODELS...AND THE HWRF/GFDL PAIR...TURN THE CYCLONE NORTHWARD AHEAD OF THE APPROACHING TROUGH. THE BULK OF THE DYNAMICAL MODELS RECURVE THE CYCLONE EAST OF 118 DEGREES WEST. FORECAST POSITIONS AND MAX WINDS INIT 22/0900Z 13.7N 107.5W 30 KT 35 MPH 12H 22/1800Z 14.0N 108.4W 40 KT 45 MPH 24H 23/0600Z 14.5N 109.7W 50 KT 60 MPH 36H 23/1800Z 15.5N 111.0W 60 KT 70 MPH 48H 24/0600Z 16.3N 112.5W 70 KT 80 MPH 72H 25/0600Z 18.0N 115.5W 75 KT 85 MPH 96H 26/0600Z 19.5N 117.0W 65 KT 75 MPH 120H 27/0600Z 21.0N 118.0W 50 KT 60 MPH $$ FORECASTER AVILA NNNN
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Page last modified: Monday, 31-Dec-2012 12:10:38 UTC