000
WTNT42 KNHC 041442
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  21
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 AM AST TUE SEP 04 2012

DEEP CONVECTION HAS DECREASED NEAR THE CENTER OF LESLIE OVER THE
PAST FEW HOURS. ALTHOUGH THERE IS STILL EVIDENCE OF ABOUT 20 KT OF
NORTHWESTERLY SHEAR...THE CONVECTIVE CLOUD STRUCTURE NOW MORE
RESEMBLES A CURVED BAND PATTERN. RECENT MICROWAVE DATA AND VISIBLE
SATELLITE IMAGES INDICATE THAT THE SHEAR HAS CONTINUED TO CAUSE THE
CIRCULATION TO BE VERTICALLY TILTED AND THE LOW-LEVEL CENTER IS
DISPLACED ABOUT 30 N MI TO THE WEST OF THE MID-LEVEL CENTER. THE
INITIAL WIND SPEED IS HELD AT 55 KT...IN AGREEMENT WITH DVORAK
CI-NUMBERS FROM TAFB AND SAB...BUT THIS COULD BE GENEROUS. LITTLE
CHANGE IN STRENGTH IS FORECAST FOR THE NEXT 36 HOURS DUE TO THE
POOR VERTICAL ALIGNMENT OF LESLIE AND THE FORECAST SHEAR...WHICH IS
EXPECTED TO REMAIN HIGH DURING THAT TIME. IN A COUPLE OF DAYS...THE
SHEAR IS EXPECTED TO LESSEN AND THE NUMERICAL MODELS SHOW A MUCH
MORE FAVORABLE UPPER-LEVEL WIND PATTERN FOR LESLIE TO GAIN
STRENGTH. THEREFORE...THE OFFICIAL FORECAST REMAINS IN LINE WITH
THE PREVIOUS FORECAST AND IS BETWEEN LGEM AND HWRF GUIDANCE.

LESLIE IS MOVING VERY SLOWLY NORTHWARD AT ABOUT 3 KT AND IS LOCATED
IN WEAK STEERING CURRENTS. THE STEERING IS EXPECTED TO REMAIN WEAK
FOR THE NEXT COUPLE OF DAYS...THEREFORE LESLIE IS FORECAST TO
CONTINUE DRIFTING NORTHWARD DURING THAT TIME. BY THE END OF THE
WEEK...THE MODELS ARE IN FAIR AGREEMENT IN SHOWING A MID-LEVEL
RIDGE BUILDING TO THE NORTHEAST OF LESLIE. THIS SHOULD CAUSE THE
CYCLONE TO FIRST TURN NORTHWESTWARD AND THEN ACCELERATE
NORTH-NORTHWESTWARD IN 4 TO 5 DAYS AS IT MOVES ALONG THE WESTERN
PERIPHERY OF THE RIDGE. THE OFFICIAL FORECAST IS SIMILAR TO THE
PREVIOUS ONE AND CLOSE TO THE CONSENSUS AIDS...TV15 AND TVCA.

DUE TO THE LARGE SIZE OF LESLIE AND ITS EXPECTED SLOW MOTION...
LARGE SWELLS PROPAGATING AWAY FROM THE TROPICAL CYCLONE WILL
CONTINUE TO AFFECT BERMUDA AND NEARLY ALL OF THE U.S. EAST
COAST FOR MUCH OF THIS WEEK.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  04/1500Z 25.0N  62.5W   55 KT  65 MPH
 12H  05/0000Z 25.5N  62.5W   55 KT  65 MPH
 24H  05/1200Z 26.0N  62.5W   55 KT  65 MPH
 36H  06/0000Z 26.5N  62.5W   55 KT  65 MPH
 48H  06/1200Z 26.8N  62.6W   60 KT  70 MPH
 72H  07/1200Z 27.5N  63.3W   70 KT  80 MPH
 96H  08/1200Z 29.2N  64.6W   80 KT  90 MPH
120H  09/1200Z 33.0N  65.5W   90 KT 105 MPH
 
$$
FORECASTER CANGIALOSI/ZELINSKY