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Tropical Storm LESLIE (Text)

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TROPICAL STORM LESLIE DISCUSSION NUMBER  36
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 AM AST SAT SEP 08 2012
 
LESLIE SHOWED SOME SIGNS OF PERHAPS GETTING BETTER ORGANIZED EARLIER
TONIGHT...WITH CONVECTIVE BANDS TRYING TO WRAP AROUND THE SOUTH
SIDE OF THE CENTER. HOWEVER...THE CLOUD PATTERN HAS RECENTLY BECOME
MORE RAGGED AND THE COLDEST TOPS ARE DISPLACED WEST AND NORTH OF
THE CENTER LOCATION. DROPSONDE DATA FROM THE AIRCRAFT MISSIONS LAST
NIGHT AND SATELLITE IMAGERY SHOW SOME DRY AIR WRAPPING INTO THE
SOUTHERN PORTION OF THE CIRCULATION...WHICH IS LIKELY HINDERING
INTENSIFICATION FOR THE TIME BEING. THE INITIAL INTENSITY REMAINS
55 KT IN AGREEMENT WITH THE LATEST DVORAK ESTIMATE FROM TAFB.
 
THE INTENSITY FORECAST REASONING REMAINS UNCHANGED...AS DRY AIR AND
RELATIVELY COOL WATERS SHOULD LEAD TO ONLY GRADUAL STRENGTHENING IN
THE NEXT DAY OR SO. AFTER THAT TIME...AS LESLIE MOVES OVER WARMER
WATERS...STEADIER INTENSIFICATION IS EXPECTED THROUGH 72 HOURS. AT
DAYS 4 AND 5 LESLIE SHOULD WEAKEN AS THE SHEAR INCREASES WHILE THE
CYCLONE MOVES NORTH OF THE GULF STREAM AND UNDERGOES EXTRATROPICAL
TRANSITION. THE NHC FORECAST IS CLOSE TO OR A LITTLE ABOVE THE
INTENSITY CONSENSUS AFTER 12 HOURS AND IS SIMILAR TO THE PREVIOUS
ADVISORY.
 
THE INITIAL MOTION ESTIMATE IS 360/04. THE MID-LEVEL RIDGE NORTH OF
LESLIE IS EXPECTED TO WEAKEN DURING THE NEXT DAY OR TWO AS A
LONGWAVE TROUGH MOVES INTO EASTERN NORTH AMERICA. LESLIE SHOULD
BEGIN TO ACCELERATE NORTHWARD AND THEN NORTH-NORTHEASTWARD THROUGH
THE PERIOD AS IT INTERACTS WITH THE TROUGH. THE NHC TRACK FORECAST
THROUGH 48 HOURS IS LARGELY AN UPDATE OF THE PREVIOUS ONE AND IS
NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE. AT 72 HOURS AND BEYOND...
THE NHC FORECAST HAS BEEN SHIFTED TO THE LEFT WITH A SLIGHTLY
SLOWER FORWARD SPEED. THIS REPRESENTS A TREND TOWARD THE LATEST
TRACK GUIDANCE...WHICH FOR THIS CYCLE GENERALLY SHOWS MORE
INTERACTION BETWEEN LESLIE AND A SHORTWAVE TROUGH THAT TRIES TO CUT
OFF EAST OF NEW ENGLAND IN 3 TO 4 DAYS. HOWEVER...THE NEW NHC TRACK
IS STILL A LITTLE EAST OF THE TVCA CONSENSUS AND LIES ALONG THE
EASTERN EDGE OF THE GUIDANCE ENVELOPE LATE IN THE PERIOD. 
 
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 AND INTO EARLY NEXT WEEK.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/0900Z 28.1N  62.3W   55 KT  65 MPH
 12H  08/1800Z 28.9N  62.2W   55 KT  65 MPH
 24H  09/0600Z 30.3N  62.0W   60 KT  70 MPH
 36H  09/1800Z 31.9N  61.6W   65 KT  75 MPH
 48H  10/0600Z 33.6N  61.0W   75 KT  85 MPH
 72H  11/0600Z 38.5N  58.5W   80 KT  90 MPH
 96H  12/0600Z 44.5N  55.5W   65 KT  75 MPH...POST-TROP/EXTRATROP
120H  13/0600Z 48.0N  53.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
 
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FORECASTER BRENNAN
 
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