ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM TROPICAL DEPRESSION SEVEN-E DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL EP072012 200 AM PDT TUE AUG 07 2012 THE LOW PRESSURE SYSTEM LOCATED WELL SOUTHWEST OF THE MEXICAN COAST HAS CONTINUED TO GAIN CONVECTIVE ORGANIZATION OVER THE PAST FEW HOURS. ALTHOUGH THE AREA OF SHOWERS AND THUNDERSTORMS IS SOMEWHAT SMALL...TAFB AND SAB WERE ABLE TO PROVIDE DVORAK ESTIMATES OF T2.0. THE LOW IS THEREFORE BEING UPGRADED TO A 30-KT DEPRESSION AT THIS TIME. THE INITIAL MOTION IS ESTIMATED TO BE 295/10 KT. THE DEPRESSION IS BEING STEERED WEST-NORTHWESTWARD BY A MID-LEVEL RIDGE OF HIGH PRESSURE THAT IS ANCHORED OVER THE SOUTHWESTERN UNITED STATES AND EXTENDS SOUTHWESTWARD TO THE HAWAIIAN ISLANDS. THE RIDGE IS EXPECTED TO HOLD FIRM IN THE VICINITY OF THE CYCLONE DURING THE 5-DAY FORECAST PERIOD. HOWEVER...THE GLOBAL MODELS SUGGEST THAT BROAD LOW-LEVEL CYCLONIC FLOW WILL DEVELOP NEAR THE MEXICAN COAST ON DAYS 3 THROUGH 5 AND POTENTIALLY SLOW THE WESTWARD MOTION OF THE CYCLONE. THE NHC FORECAST INDICATES A STEADY WEST-NORTHWESTWARD MOVEMENT DURING THE FIRST 2 DAYS OR SO...FOLLOWED BY A DECELERATING WESTWARD MOTION THEREAFTER. CONFIDENCE IN THIS TRACK FORECAST IS HIGH GIVEN THE LESS-THAN-NORMAL SPREAD IN THE TRACK GUIDANCE. THE DEPRESSION IS OVER WATER OF ABOUT 29C AND IN AN ENVIRONMENT OF LIGHT SHEAR. A LARGE UPPER-LEVEL LOW LOCATED SOUTHWEST OF THE BAJA PENINSULA IS MOVING STEADILY WESTWARD...WHICH IS ALLOWING THE UPPER-LEVEL OUTFLOW OVER THE DEPRESSION TO EXPAND WESTWARD. ENVIRONMENTAL CONDITIONS SHOULD ALLOW FOR STRENGTHENING OVER THE NEXT 3 DAYS OR SO...AND THE OFFICIAL FORECAST IS AT THE HIGHER END OF THE INTENSITY GUIDANCE. BY DAYS 4 AND 5...THE CYCLONE WILL BE LOCATED IN A MORE MARGINAL THERMODYNAMIC ENVIRONMENT...AND THE CIRCULATION COULD BECOME DECOUPLED WHEN THE LOW-LEVEL CENTER IS TUGGED BACK TO THE EAST. WEAKENING IS THEREFORE EXPECTED AT THE LATTER STAGES OF THE FORECAST. FORECAST POSITIONS AND MAX WINDS INIT 07/0900Z 14.3N 111.7W 30 KT 35 MPH 12H 07/1800Z 14.9N 113.0W 35 KT 40 MPH 24H 08/0600Z 15.7N 114.9W 45 KT 50 MPH 36H 08/1800Z 16.5N 116.7W 50 KT 60 MPH 48H 09/0600Z 17.0N 118.5W 55 KT 65 MPH 72H 10/0600Z 17.0N 120.5W 60 KT 70 MPH 96H 11/0600Z 17.0N 121.5W 55 KT 65 MPH 120H 12/0600Z 17.0N 121.5W 45 KT 50 MPH $$ FORECASTER BERG NNNN
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Page last modified: Monday, 31-Dec-2012 12:10:22 UTC