Tropical Storm LESLIE

ZCZC MIATCDAT2 ALL
TTAA00 KNHC DDHHMM
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  40
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 AM AST SUN SEP 09 2012
 
DEEP CONVECTION ASSOCIATED WITH LESLIE DECREASED IN COVERAGE LATE
IN THE EVENING...HOWEVER A NEW BURST OF THUNDERSTORMS HAS FORMED
JUST NORTH OF THE CENTER...AND IT IS NOW WRAPPING AROUND THE 
WESTERN PORTION OF THE CIRCULATION.  THE LATEST DVORAK INTENSITY
ESTIMATES RANGE FROM 45 TO 55 KT AND AN EARLIER ASCAT PASS SHOWED 
A LARGE AREA OF 40-45 KT WINDS.  THE INITIAL INTENSITY IS MAINTAINED
AT 55 KT...WHICH COULD BE A LITTLE GENEROUS.

AS LESLIE MOVES NORTHWARD IT SHOULD FINALLY LEAVE THE AREA OF COOLER
WATERS CAUSED BY UPWELLING DURING THE PAST SEVERAL DAYS.  AS THIS
OCCURS THE CYCLONE IS FORECAST TO BE IN A FAVORABLE UPPER-AIR
ENVIRONMENT.  THESE CONDITIONS FAVOR INTENSIFICATION...HOWEVER
GIVEN THE CURRENT STRUCTURE OF THE CYCLONE AND ISSUES WITH DRY 
AIR ENTRAINMENT...LESLIE MAY HAVE SOME DIFFICULTY IN STRENGTHENING. 
THE NEW NHC FORECAST CALLS SOME INCREASE IN WIND SPEED...BUT LESS
THAN IN THE PREVIOUS ADVISORY.  LESLIE IS FORECAST TO BEGIN
INTERACTING WITH A FRONTAL ZONE WITHIN 48 HOURS AND THE CYCLONE IS
EXPECTED TO BECOME EXTRATROPICAL EARLY TUESDAY. THE EXTRATROPICAL
LOW IS PREDICTED TO MAINTAIN ITS INTENSITY FOR A DAY OR SO BEFORE
GRADUALLY WEAKENING OVER THE NORTH ATLANTIC. 

THE INITIAL MOTION IS 360 DEGREES AT 8 KT.  LESLIE IS FORECAST TO
BEGIN MOVING FASTER TOWARD THE NORTH AND NORTH-NORTHEAST AS A LARGE
DEEP-LAYER TROUGH MOVES EASTWARD OFF THE EAST COAST OF THE UNITED
STATES.  THE TRACK MODEL GUIDANCE IS TIGHTLY CLUSTERED DURING THE
FIRST 48 HOURS AND THE NHC TRACK IS NEAR THE MIDDLE OF THE GUIDANCE
ENVELOPE.  THE GLOBAL MODEL GUIDANCE HAS ONCE AGAIN TRENDED TOWARD
A FASTER SOLUTION FOR THE 3 TO 5 DAY FORECAST PERIODS.  THIS HAS
RESULTED IN A SIGNIFICANT ADJUSTMENT TO THE TRACK FORECAST AT 72
THROUGH 120 H.  HOWEVER...THE TRACK FORECAST FOR THE EXTRATROPICAL
PORTION IS STILL SLOWER THAN THE MODEL CONSENSUS IN ORDER TO
MAINTAIN SOME CONTINUITY WITH THE PREVIOUS ADVISORY. 
 
LONG-PERIOD SWELLS FROM LESLIE ARE EXPECTED TO PRODUCE ROUGH SURF
AND LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF THE
U.S. EAST COAST FOR THE NEXT FEW DAYS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/0900Z 30.8N  62.5W   55 KT  65 MPH
 12H  09/1800Z 32.4N  62.3W   55 KT  65 MPH
 24H  10/0600Z 34.5N  61.5W   60 KT  70 MPH
 36H  10/1800Z 37.5N  60.2W   65 KT  75 MPH
 48H  11/0600Z 42.0N  58.0W   65 KT  75 MPH
 72H  12/0600Z 52.0N  50.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
 96H  13/0600Z 59.5N  35.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
120H  14/0600Z 61.0N  15.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER BROWN
 
NNNN