Hurricane LESLIE

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HURRICANE LESLIE DISCUSSION NUMBER  32
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 AM AST FRI SEP 07 2012
 
THE SATELLITE PRESENTATION OF LESLIE HAS DEGRADED SOMEWHAT OVER THE
PAST FEW HOURS. THE EARLIER CDO FEATURE HAS LARGELY DISSIPATED AND
MOST OF THE REMAINING COLD CLOUD TOPS ARE DISPLACED TO THE EAST OF
THE CENTER IN SOME RAGGED BANDS. THE INITIAL INTENSITY REMAINS 65
KT BASED ON THE LATEST DVORAK ESTIMATES FROM TAFB AND SAB. A NOAA
HURRICANE HUNTER AIRCRAFT WILL BE INVESTIGATING LESLIE LATER THIS
MORNING AND PROVIDE VALUABLE DATA ON THE INTENSITY AND STRUCTURE OF
THE CYCLONE. 

SATELLITE WINDS AND ANALYSES FROM UW-CIMSS SUGGEST THAT SOME LIGHT
TO MODERATE WEST-SOUTHWESTERLY SHEAR IS IMPACTING THE CYCLONE. THE 
SHEAR ALONG WITH THE DISORGANIZED STATE OF THE INNER CORE AND
COOLING SSTS DUE TO UPWELLING SHOULD RESULT IN LITTLE CHANGE IN
INTENSITY DURING THE NEXT 24 HOURS. AFTER THAT TIME...AS LESLIE
BEGINS TO MOVE NORTHWARD TOWARD WARMER WATERS...THE SHEAR IS
EXPECTED TO DIMINISH AND SOME STRENGTHENING IS FORECAST. WEAKENING
IS EXPECTED LATE IN THE PERIOD AS THE CYCLONE ENCOUNTERS COOLER
WATERS AND INCREASING SHEAR DURING EXTRATROPICAL TRANSITION. THE
NEW NHC INTENSITY FORECAST IS A BIT LOWER THAN THE PREVIOUS ONE AT
48 AND 72 HOURS AND IS CLOSE TO THE LATEST IVCN CONSENSUS. 

SATELLITE FIXES AND WIND OBSERVATIONS FROM NOAA BUOY 41049 SUGGEST
THAT LESLIE IS DRIFTING SLOWLY NORTHWARD. A STEADIER NORTHWARD
MOTION SHOULD BEGIN BY 24 HOURS AS THE RIDGE NORTH OF LESLIE BEGINS
TO MOVE EASTWARD AND AMPLIFY. AFTER 48 HOURS...AN ACCELERATION
TOWARD THE NORTH AND NORTH-NORTHEAST IS EXPECTED AS LESLIE
INTERACTS WITH A COMPLEX MID/UPPER-LEVEL TROUGH MOVING FROM THE
EASTERN UNITED STATES TO THE CANADIAN MARITIMES. THE TRACK MODEL
GUIDANCE STILL SHOWS SOME SPREAD IN FORWARD SPEED AND HEADING...
ESPECIALLY LATE IN THE PERIOD. THE ECMWF IS ALONG THE LEFT SIDE OF
THE GUIDANCE ENVELOPE WITH THE GFDL...WHILE THE LATEST GFS RUN HAS
TRENDED FASTER AND LEFT TOWARD THE REST OF THE GUIDANCE. THE END
RESULT IS THAT THE LATEST TVCA MULTI-MODEL CONSENSUS IS VERY CLOSE
TO THE PREVIOUS NHC FORECAST...AND THE NEW NHC TRACK IS BASICALLY
AN UPDATE OF THE PREVIOUS ONE. AT DAYS 3 THROUGH 5 THE NHC FORECAST
IS VERY CLOSE TO THE FSU SUPERENSEMBLE AND A BLEND OF THE ECMWF AND
GFS MODELS. 

THE WIND FIELD OF LESLIE...COMBINED WITH ITS EXPECTED SLOW MOTION...
WILL GENERATE LONG-PERIOD SWELLS THAT WILL PRODUCE LARGE WAVES AND
LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF THE U.S.
EAST COAST THROUGH THE WEEKEND. 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/0900Z 26.7N  62.2W   65 KT  75 MPH
 12H  07/1800Z 26.9N  62.3W   65 KT  75 MPH
 24H  08/0600Z 27.6N  62.4W   65 KT  75 MPH
 36H  08/1800Z 28.6N  62.4W   70 KT  80 MPH
 48H  09/0600Z 30.1N  62.2W   75 KT  85 MPH
 72H  10/0600Z 33.7N  61.0W   85 KT 100 MPH
 96H  11/0600Z 38.5N  58.0W   80 KT  90 MPH
120H  12/0600Z 46.0N  54.5W   65 KT  75 MPH...POST-TROP/EXTRATROP
 
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FORECASTER BRENNAN
 
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