000
WTNT42 KNHC 050859
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  24
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 AM AST WED SEP 05 2012
 
AFTER DEVELOPING A CDO-LIKE FEATURE EARLIER...THE DEEP CONVECTION IS
NOW DISPLACED TO THE EAST OF THE ESTIMATED CENTER LOCATION...LIKELY
DUE TO CONTINUED WEST-NORTHWESTERLY SHEAR OF AROUND 20 KT. THE
INITIAL INTENSITY REMAINS 55 KT BASED ON THE LATEST DVORAK ESTIMATE
FROM TAFB. ONLY GRADUAL STRENGTHENING IS EXPECTED FOR THE NEXT DAY
OR SO UNTIL THE SHEAR RELAXES...AND THE NHC INTENSITY FORECAST IS
BELOW THE INTENSITY CONSENSUS FOR THE FIRST 48 HOURS. CONDITIONS
APPEAR FAVORABLE FOR STEADIER INTENSIFICATION AFTER THAT TIME...AND
THE NHC FORECAST AT DAYS 3 THROUGH 5 IS CLOSE TO THE LATEST IVCN
CONSENSUS.
 
IT STILL APPEARS THAT THE LOW-LEVEL CENTER IS DISPLACED A BIT TO THE
WEST OF THE MID-LEVEL ROTATION SEEN IN SATELLITE IMAGERY...BUT THE
INITIAL POSITION AND MOTION OF 340/02 IS UNCERTAIN GIVEN A LACK OF
RECENT MICROWAVE IMAGERY. OVERALL THE SYNOPTIC REASONING REMAINS
UNCHANGED FOR THE TRACK FORECAST. LESLIE IS CAUGHT IN A REGION OF
WEAK STEERING BETWEEN TWO WEAK MID-LEVEL ANTICYCLONES...WHICH
SHOULD RESULT IN A SLOW NORTH-NORTHWESTWARD TO NORTHWARD MOTION FOR
THE NEXT 48 HOURS. BY 72 HOURS...A TROUGH BEGINS TO AMPLIFY OVER
EASTERN NORTH AMERICA WHILE A MID-LEVEL RIDGE BUILDS TO THE EAST OF
LESLIE...WHICH SHOULD RESULT IN A NORTHWARD ACCELERATION. WHILE
THERE IS STILL SOME SPREAD IN THE GUIDANCE REGARDING THE FORWARD
SPEED AND HEADING LATE IN THE PERIOD...THE MODELS HAVE TRENDED
TOWARD A MORE PROGRESSIVE SOLUTION WITH THE TROUGH MOVING OFF THE
U.S. EAST COAST. THIS SHOULD RESULT IN LESLIE TURNING A LITTLE TO
THE EAST OF DUE NORTH BY DAY 5 WITH AN INCREASE IN FORWARD SPEED.
THE NEW NHC TRACK IS LARGELY AN UPDATE OF THE PREVIOUS ONE BUT IS A
LITTLE FASTER AND FARTHER TO THE RIGHT AT DAY 5. THE NHC FORECAST
IS CLOSE TO THE LATEST TVCA CONSENSUS AND LIES ROUGHLY BETWEEN THE
ECMWF AND GEFS ENSEMBLE MEAN.

LESLIE IS A LARGE TROPICAL CYCLONE AND IS FORECAST TO GROW IN SIZE
DURING THE NEXT SEVERAL DAYS. THE WIND FIELD OF THE CYCLONE...
COMBINED WITH ITS EXPECTED SLOW MOTION...WILL HELP TO GENERATE
LARGE LONG-PERIOD SWELLS THAT WILL PROPAGATE AWAY FROM THE TROPICAL
CYCLONE TOWARD BERMUDA AND MUCH OF THE U.S. EAST COAST FOR THE
REMAINDER OF THIS WEEK.
 
THE 34-KT WIND RADII WERE EXPANDED IN THE NORTHWEST QUADRANT BASED
ON OBSERVATIONS FROM NOAA BUOY 41049. 
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/0900Z 25.4N  62.9W   55 KT  65 MPH
 12H  05/1800Z 25.8N  63.0W   55 KT  65 MPH
 24H  06/0600Z 26.2N  63.1W   60 KT  70 MPH
 36H  06/1800Z 26.6N  63.1W   65 KT  75 MPH
 48H  07/0600Z 26.9N  63.3W   70 KT  80 MPH
 72H  08/0600Z 28.2N  64.2W   80 KT  90 MPH
 96H  09/0600Z 31.5N  65.0W   85 KT 100 MPH
120H  10/0600Z 37.5N  64.0W   90 KT 105 MPH
 
$$
FORECASTER BRENNAN