000
WTNT42 KNHC 032034
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  18
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 PM AST MON SEP 03 2012
 
SOME DEEP CONVECTION HAS DEVELOPED CLOSE TO THE LOW-LEVEL CENTER OF
LESLIE RECENTLY...BUT THE OVERALL CLOUD PATTERN IS STILL HIGHLY
ASYMMETRIC DUE TO WEST-NORTHWESTERLY SHEAR. SATELLITE INTENSITY
ESTIMATES FROM TAFB...SAB...AND UW-CIMSS SUPPORT MAINTAINING THE
INITIAL WIND SPEED AT 50 KT. THE SHEAR IS NOT EXPECTED TO LET UP
MUCH FOR THE NEXT 12 TO 18 HOURS...SO LESLIE IS EXPECTED TO CHANGE
LITTLE IN STRENGTH DURING THAT TIME. AFTER THAT...HOWEVER...THE
SHEAR IS FORECAST TO LESSEN AND THE GLOBAL MODELS SHOW AN
UPPER-LEVEL WIND PATTERN THAT IS QUITE FAVORABLE FOR THE CYCLONE TO
INTENSIFY. THE OFFICIAL WIND SPEED FORECAST IS AN UPDATE OF THE
PREVIOUS ONE AND CLOSE TO AN AVERAGE OF THE LATEST SHIPS AND LGEM
GUIDANCE. 

LESLIE HAS BEEN WOBBLING AROUND MOST OF THE DAY...AND THE LATEST
VISIBLE IMAGES INDICATE THAT THE CENTER IS LOCATED TO THE SOUTH OF
THE PREVIOUS ADVISORY POSITION. A LONGER-TERM MOTION ESTIMATE IS
330/3. A VERY SLOW NORTHWARD MOTION IS FORECAST FOR THE NEXT 3 TO 4
DAYS AS LESLIE REMAINS IN WEAK STEERING CURRENTS. BY THE END OF THE
WEEK...A RIDGE IS EXPECTED TO BUILD TO THE EAST OF THE TROPICAL
CYCLONE WHICH SHOULD STEER LESLIE TO THE NORTH-NORTHWEST AT A
FASTER PACE. THE 12Z ECMWF MODEL HAS SHIFTED WELL TO THE WEST AT
DAYS 4 AND 5...AND THERE IS NOW A WIDE SPREAD IN THE MODEL
GUIDANCE. THE OFFICIAL FORECAST IS SLOWER THAN THE PREVIOUS ONE AND
A LITTLE TO THE LEFT AT DAY 5. THIS FORECAST LIES FAIRLY CLOSE TO
THE CONSENSUS AIDS...TVCA AND TV15.
  
DUE TO THE LARGE SIZE OF THE CYCLONE AND EXPECTED SLOW MOTION...
LARGE SWELLS PROPAGATING AWAY FROM THE TROPICAL CYCLONE WILL AFFECT
BERMUDA AND NEARLY ALL OF THE U.S. EAST COAST FOR MUCH OF THE WEEK.
 
THE 34-KT AND 50-KT WIND RADII WERE MODIFIED BASED ON A 1340 UTC
ASCAT PASS.

FORECAST POSITIONS AND MAX WINDS
 
INIT  03/2100Z 24.0N  63.1W   50 KT  60 MPH
 12H  04/0600Z 24.6N  63.2W   50 KT  60 MPH
 24H  04/1800Z 25.3N  63.2W   55 KT  65 MPH
 36H  05/0600Z 25.8N  63.2W   55 KT  65 MPH
 48H  05/1800Z 26.3N  63.2W   60 KT  70 MPH
 72H  06/1800Z 27.0N  63.3W   70 KT  80 MPH
 96H  07/1800Z 28.1N  63.8W   80 KT  90 MPH
120H  08/1800Z 30.5N  65.0W   85 KT 100 MPH
 
$$
FORECASTER CANGIALOSI