ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM ALETTA DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL EP012012 800 AM PDT TUE MAY 15 2012 THE CLOUD PATTERN OF ALETTA HAS CHANGED LITTLE DURING THE PAST 12 HOURS OR SO. THE CYCLONE CONSISTS OF A COUPLE OF CLUSTERS OF DEEP CONVECTION WITH THE CENTER APPARENTLY ON THE SOUTHEASTERN EDGE OF THE MAIN CONVECTIVE MASS. DVORAK T-NUMBERS REMAIN AT 2.5 FROM BOTH SAB AND TAFB AND THE INITIAL INTENSITY IS ONCE AGAIN MAINTAINED AT 35 KT. ALETTA IS EXPECTED TO REMAIN IN A LOW SHEAR ENVIRONMENT AND OVER WARM SSTS THAT COULD ALLOW FOR SOME SLIGHT STRENGTHENING DURING THE 12 HOURS OR SO. AFTER THAT TIME...AN APPROACHING UPPER-LEVEL TROUGH FROM THE WEST IS EXPECTED TO CAUSE AN INCREASE IN SOUTHWESTERLY SHEAR. THE INCREASING SHEAR AND SOME DRIER AIR THAT IS CURRENTLY LOCATED TO THE WEST OF THE CYCLONE ARE EXPECTED TO INITIATE WEAKENING WITHIN 24-36 HOURS. ALETTA IS FORECAST TO DEGENERATE INTO A REMNANT LOW IN A FEW DAYS AND DISSIPATE BY THE END OF THE FORECAST PERIOD. ALETTA IS MOVING WESTWARD OR 280/8 KT. THE CYCLONE SHOULD CONTINUE MOVING WESTWARD TO WEST-NORTHWESTWARD WITH SOME INCREASE IN FORWARD SPEED DURING THE NEXT 2-3 DAYS AS IT REMAINS SOUTH OF A STRONG MID-LEVEL RIDGE. THE RIDGE IS FORECAST TO WEAKEN LATER IN THE FORECAST PERIOD AS A MID- TO UPPER-LEVEL TROUGH APPROACHES FROM THE NORTHWEST. THIS SHOULD RESULT IN A CONSIDERABLE SLOWING OF THE FORWARD MOTION OF THE CYCLONE. THE TRACK GUIDANCE IS IN FAIRLY GOOD AGREEMENT THROUGH 48 HOURS...BUT THERE IS SOME SPREAD AFTER THAT TIME AS SOME OF THE MODELS TURN THE CYCLONE NORTHWARD BY THE END OF THE PERIOD. FOR NOW...THE NHC FORECAST SHOWS ALLETTA MAINTAINING A WEST-NORTHWESTWARD MOTION UNTIL DISSIPATION. HOWEVER... THE UPDATED FORECAST IS CONSIDERABLY SLOWER THAN THE PREVIOUS ADVISORY AT DAYS 3 AND 4...IN DEFERENCE TO THE SLOWER FORWARD SPEED SHOWN BY MOST OF THE DYNAMICAL MODELS BY THAT TIME. FORECAST POSITIONS AND MAX WINDS INIT 15/1500Z 10.6N 109.6W 35 KT 40 MPH 12H 16/0000Z 11.0N 111.1W 40 KT 45 MPH 24H 16/1200Z 11.3N 113.2W 40 KT 45 MPH 36H 17/0000Z 11.6N 115.3W 35 KT 40 MPH 48H 17/1200Z 12.0N 117.0W 30 KT 35 MPH 72H 18/1200Z 12.5N 119.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 19/1200Z 13.0N 120.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 20/1200Z...DISSIPATED $$ FORECASTER BROWN NNNN
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Page last modified: Monday, 31-Dec-2012 12:10:03 UTC