Tropical Storm LESLIE

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TROPICAL STORM LESLIE DISCUSSION NUMBER  23
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 PM AST TUE SEP 04 2012
 
DEEP CONVECTION HAS BEEN BURSTING NEAR THE LOW-LEVEL CENTER OF
LESLIE FOR THE PAST FEW HOURS.  THE CONVECTION HAS TAKEN ON THE
SHAPE OF A NASCENT CENTRAL DENSE OVERCAST...BUT WEST-NORTHWESTERLY
SHEAR OF AROUND 20 KT CONTINUES TO PUSH THE MAIN CONVECTIVE MASS
EASTWARD.  TRMM AND SSM/IS IMAGES...FROM 2223 AND 0013 UTC
RESPECTIVELY...SUGGEST SOME RECENT INCREASE IN ORGANIZATION AS
EVIDENCED BY THE FORMATION OF A CLOSED MID-LEVEL EYE...BUT THIS
FEATURE CONTINUES TO BE DISPLACED 20-30 N MI EAST OF THE LOW-LEVEL
CENTER.  THE INITIAL INTENSITY IS HELD AT 55 KT IN AGREEMENT WITH A
0000 UTC SATELLITE CLASSIFICATION FROM TAFB. GLOBAL MODELS FORECAST
A SUBSTANTIAL DECREASE IN SHEAR IN ABOUT 24 HOURS AS A LARGE-SCALE
ANTICYCLONE FORMS OVER LESLIE. THE DEEP OCEANIC MIXED LAYER ALONG
THE TRACK OF THE SLOW-MOVING STORM SHOULD ALSO MINIMIZE THE EFFECTS
OF UPWELLING.  STRENGTHENING IS FORECAST TO BEGIN AROUND THE TIME
THE SHEAR RELAXES...BUT THE RATE OF INTENSIFICATION COULD INITIALLY
BE SLOW DUE TO THE LARGE SIZE OF THE CIRCULATION. THE NHC INTENSITY
FORECAST IS NOT MUCH DIFFERENT THAN THE PREVIOUS ONE...AND IS IN
GOOD AGREEMENT WITH THE LATEST SHIPS AND INTENSITY CONSENSUS AIDS.
 
LESLIE APPEARS TO HAVE JOGGED A BIT TO THE LEFT TODAY...AND IS
PLODDING ALONG TOWARD THE NORTH-NORTHWEST WITH AN INITIAL MOTION
ESTIMATE OF 345/02.  THE CYCLONE IS IN A WEAK STEERING
ENVIRONMENT...SANDWICHED BETWEEN TWO WEAK MID-LEVEL ANTICYCLONES. 
WHILE THIS PATTERN SHOULD ALLOW A NET NORTHWARD STEERING FLOW OVER
LESLIE DURING THE NEXT FEW DAYS...THE STORM IS LIKELY TO MAKE ONLY
SLOW PROGRESS DUE TO A WEAK BLOCKING LOW- TO MID-LEVEL RIDGE
SLIDING BY TO THE NORTH.  AS THAT RIDGE SHIFTS AND BUILDS TO THE
NORTHEAST IN 48-72 HOURS...LESLIE WILL BE DRAWN NORTHWARD MORE
QUICKLY.  THE FLOW BETWEEN THIS SAME RIDGE AND AN AMPLIFYING
SHORTWAVE TROUGH APPROACHING THE UNITED STATES EAST COAST ON DAYS
4-5 WILL BEGIN TO EJECT LESLIE TOWARD THE NORTH OR NORTH-NORTHEAST
BY THE END OF THE FORECAST PERIOD.  THE NHC TRACK FORECAST IS BIT
SLOWER THAN THE PREVIOUS ONE AFTER 48 HOURS IN DEFERENCE TO THE
LATEST GFS RUN...BUT IS ADJUSTED A BIT TO THE EAST AT LATER TIMES. 
THIS IS CLOSE TO THE MULTI-MODEL TVCA CONSENSUS.
 
LESLIE IS A LARGE TROPICAL CYCLONE AND IS FORECAST TO GROW FURTHER
IN SIZE DURING THE NEXT SEVERAL DAYS. THE WIND FIELD OF THE
CYCLONE...IN COMBINATION WITH ITS EXPECTED SLOW MOTION...WILL HELP
TO GENERATE LARGE LONG-PERIOD SWELLS WHICH WILL PROPAGATE AWAY FROM
THE TROPICAL CYCLONE TOWARD BERMUDA BERMUDA AND MUCH OF THE UNITED
STATES EAST COAST FOR THE REMAINDER OF THIS WEEK.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/0300Z 25.2N  62.8W   55 KT  65 MPH
 12H  05/1200Z 25.6N  62.9W   55 KT  65 MPH
 24H  06/0000Z 26.1N  63.0W   55 KT  65 MPH
 36H  06/1200Z 26.5N  63.0W   60 KT  70 MPH
 48H  07/0000Z 26.7N  63.0W   65 KT  75 MPH
 72H  08/0000Z 27.5N  63.8W   75 KT  85 MPH
 96H  09/0000Z 30.0N  65.0W   80 KT  90 MPH
120H  10/0000Z 35.0N  65.0W   90 KT 105 MPH
 
$$
FORECASTER KIMBERLAIN
 
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