Tropical Storm SHARY

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TROPICAL STORM SHARY DISCUSSION NUMBER   3...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL202010
1100 AM AST FRI OCT 29 2010

CORRECTED INITIAL MOTION ESTIMATE TO BE 325/08
 
SATELLITE IMAGERY INDICATES SHARY HAS SLOWED DOWN CONSIDERABLY
DURING THE PAST FEW HOURS AS A SMALL UPPER-LEVEL LOW HAS DROPPED TO
THE SOUTH AND SOUTHEAST OF THE CYCLONE. THIS HAS RESULTED IN THE
VERTICAL SHEAR SHIFTING FROM AN EASTERLY TO NORTHERLY DIRECTION...
CAUSING THE INNER-CORE CONVECTION TO SHIFT TO THE SOUTH SIDE OF THE
CIRCULATION CENTER. DRY AIR NOTED IN WATER VAPOR IMAGERY HAS ALSO
WRAPPED INTO THE EASTERN AND NORTHERN QUADRANTS...RESULTING IN
EROSION OF CONVECTION IN THOSE AREAS. THE INITIAL ESTIMATE REMAINS
AT 35 KT FOR THIS BASED ON SHEAR-PATTERN SATELLITE INTENSITY
ESTIMATES OF T2.5/35 KT FROM TAFB AND T3.0/45 KT FROM SAB.
 
THE INITIAL MOTION ESTIMATE IS 325/08. SHARY IS POSSIBLY PREPARING
TO MAKE A SHARP CUSP IN THE TRACK...AND A TURN TO THE NORTH AND
NORTHEAST IS EXPECTED WITHIN THE NEXT 12 HOURS OR SO AS THE SMALL
UPPER-LEVEL LOW THAT HAS BEEN INFLUENCING THE SHORT TERM MOTION
WEAKENS AND/OR DISSIPATES. AFTER THAT...AN EASTWARD-MOVING
MID-/UPPER-LEVEL TROUGH CURRENTLY LOCATED JUST OFF THE U.S. EAST
COAST AND EXTENDING ACROSS FLORIDA IS FORECAST TO CAPTURE THE
CYCLONE BY 24 HOURS...AND ACCELERATE SHARY RAPIDLY TO THE
NORTHEAST. NHC MODEL GUIDANCE IS IN EXCELLENT AGREEMENT ON THIS
TRACK SCENARIO...EXCEPT FOR JUST MINOR DIFFERENCES IN THE FORWARD
SPEED. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS
ADVISORY AND IS CLOSE TO THE MULTI-MODEL CONSENSUS...TVCN.
 
THE VERTICAL SHEAR IS FORECAST TO WEAKEN SOME AND REMAIN BELOW 10
KT FOR THE NEXT 12-18 HOURS WHILE SHARY REMAINS OVER MARGINAL SSTS
NEAR 26C. THE LOW SHEAR AND COOLER-THAN-NORMAL TEMPERATURES
ALOFT...AS NOTED IN THE 11Z BERMUDA UPPER-AIR SOUNDING...SHOULD
ALLOW FOR DEEP CONVECTION TO RE-DEVELOP NEAR THE CENTER...RESULTING
IN SOME SLIGHT STRENGTHENING. BY 24 HOURS AND BEYOND...HOWEVER...
STRONG VERTICAL SHEAR IN EXCESS OF 30 KT SHOULD KICK IN AND HELP THE
CYCLONE TO TRANSITION INTO A POST-TROPICAL LOW PRESSURE SYSTEM AS
THE CYCLONE MOVES OVER MUCH COOLER WATER TEMPERATURES. THE GFDL AND
HWRF MODELS MAKE SHARY A HURRICANE IN ABOUT 36 HOURS...WHICH SEEMS
EXCESSIVE GIVEN THE VERY COOL SSTS THAT THE CYCLONE WILL BE PASSING
OVER AT THAT TIME. AS A RESULT...THOSE INTENSITY FORECAST SCENARIOS
HAVE BEEN DISCOUNTED. THE NHC INTENSITY FORECAST IS SIMILAR TO THE
PREVIOUS ADVISORY AND IS A BLEND OF THE SHIPS/LGEM MODELS. 

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      29/1500Z 29.6N  66.2W    35 KT
 12HR VT     30/0000Z 32.2N  64.5W    40 KT
 24HR VT     30/1200Z 35.6N  60.0W    45 KT
 36HR VT     31/0000Z 39.9N  52.9W    45 KT...POST-TROP/EXTRATROP
 48HR VT     31/1200Z 45.0N  43.5W    40 KT...POST-TROP/EXTRATROP
 72HR VT     01/1200Z...DISSIPATED
 
$$
FORECASTER STEWART
 
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