Tropical Storm LESLIE

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TROPICAL STORM LESLIE DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 PM AST SAT SEP 01 2012

THE CENTER OF LESLIE REMAINS EXPOSED TO THE NORTHWEST OF THE MAIN
CONVECTIVE MASS DUE TO 15-20 KT OF NORTHWESTERLY VERTICAL WIND
SHEAR.  SATELLITE INTENSITY ESTIMATES ARE 55 KT FROM TAFB AND 45 KT
FROM SAB.  DATA FROM THE INDIAN OSCAT SCATTEROMETER NEAR 1630 UTC
SUGGESTED AN INTENSITY NEAR 55 KT.  SINCE THE SATELLITE APPEARANCE
HAS CHANGED LITTLE SINCE THAT TIME...THE INITIAL INTENSITY IS HELD
AT A POSSIBLY GENEROUS 55 KT.
 
LESLIE HAS TURNED NORTHWESTWARD DURING THE PAST SEVERAL HOURS WITH
AN INITIAL MOTION OF 305/16. THE CYCLONE SHOULD GRADUALLY TURN
NORTHWARD WITH A DECREASE IN FORWARD SPEED DURING THE NEXT 48 HR AS
IT MOVES INTO A BREAK IN THE SUBTROPICAL RIDGE CAUSED BY A
MID/UPPER-LEVEL LOW NEAR 28N72W AND A BROAD MID/UPPER-LEVEL TROUGH
NORTH OF 35N BETWEEN 55-75W. AFTER THAT...ALL OF THE GUIDANCE
AGREES THAT LESLIE SHOULD MOVE SLOWLY IN A GENERALLY NORTHWARD
DIRECTION AS IT INTERACTS WITH THE MID/UPPER-LEVEL LOW...THE
REMANTS OF ISAAC...THE SUBTROPICAL RIDGE TO THE EAST...AND A
SHORTWAVE RIDGE IN THE WESTERLIES PASSING NORTH OF THE STORM. THE
GUIDANCE HAS CHANGED LITTLE SINCE THE PREVIOUS ADVISORY...AND THE
NEW FORECAST TRACK IS AN UPDATE OF THE PREVIOUS TRACK.
 
THE INTENSITY FORECAST IS PROBLEMATIC.  THE GLOBAL MODELS AGREE ON
FORECASTING INCREASING SHEAR OVER LESLIE DURING THE NEXT 48 HR...
AND THE SHIPS MODEL FORECASTS SHEAR IN EXCESS OF 25 KT.  DESPITE
THIS...MUCH OF THE INTENSITY GUIDANCE EITHER MAINTAINS THE
STRENGTH OF THE CYCLONE OR FORECASTS INTENSIFICATION DURING THIS
TIME.  BASED ON THE FORECAST SHEAR...THE NEW INTENSITY FORECAST NOW
CALLS FOR SLIGHT WEAKENING DURING THE FIRST 48 HR...WITH THE
FORECAST NEAR THE THE LOWER EDGE OF THE INTENSITY GUIDANCE.  THE
SHEAR MAY START TO SUBSIDE AFTER 48 HR...AND THE GLOBAL MODELS
FORECAST LESLIE TO GROW IN BOTH SIZE AND DEPTH DURING THAT TIME. 
THIS PORTION OF THE INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS
ADVISORY...BUT IS WEAKER THAN THE INTENSITY CONSENSUS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  02/0300Z 20.2N  58.4W   55 KT  65 MPH
 12H  02/1200Z 21.3N  60.1W   55 KT  65 MPH
 24H  03/0000Z 23.1N  61.6W   50 KT  60 MPH
 36H  03/1200Z 24.7N  62.5W   50 KT  60 MPH
 48H  04/0000Z 25.8N  62.7W   50 KT  60 MPH
 72H  05/0000Z 27.0N  62.5W   55 KT  65 MPH
 96H  06/0000Z 28.0N  62.5W   65 KT  75 MPH
120H  07/0000Z 29.5N  62.5W   70 KT  80 MPH
 
$$
FORECASTER BEVEN
 
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