Hurricane IGOR

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HURRICANE IGOR DISCUSSION NUMBER  34...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST THU SEP 16 2010

CORRECT INITIAL INTENSITY FROM 115 KT TO 120 KT
 
IGOR IS MAINTAINING VERY DEEP CONVECTION AND A 30-35 NMI WIDE EYE
WITHIN A CENTRAL DENSE OVERCAST...BUT THE OVERALL CONVECTIVE
PATTERN HAS BECOME MORE ASYMMETRIC. THE RESTRICTED NATURE OF THE
OUTFLOW TO THE WEST OF THE CYCLONE SUGGESTS SOME UPPER-LEVEL
WESTERLY FLOW IMPINGING ON THE CIRCULATION...WHICH MAY ALSO BE
CONTRIBUTING TO THE RAGGED APPEARANCE OF THE CDO. SUBJECTIVE DVORAK
T-NUMBERS ARE A CONSENSUS 6.0 AT 1200 UTC AND SERVE AS THE BASIS
FOR LOWERING THE INTENSITY TO 120 KT FOR THIS ADVISORY. AN AIR
FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT IS SCHEDULED TO
INVESTIGATE IGOR IN A FEW HOURS AND WILL PROVIDE A MORE ACCURATE
ASSESSMENT OF ITS INTENSITY.
 
WATER VAPOR IMAGERY SUGGESTS THAT THE COMBINATION OF A SHEAR AXIS
NORTHWEST OF IGOR AND THE SOUTHWESTWARD DISPLACEMENT OF THE
UPPER-LEVEL ANTICYCLONE ASSOCIATED WITH IGOR MAY BE IMPARTING WEAK
TO MODERATE WESTERLY SHEAR TO THE HURRICANE. SHIPS MODEL OUTPUT
INDICATES THAT THIS SHEAR MAY PERSIST FOR NEXT 12-24 HOURS AND THEN
DECREASE...ALLOWING FOR SOME INTENSIFICATION BEFORE ABOUT 48 HOURS.
ALTHOUGH INNER CORE DYNAMICS WILL LIKELY INDUCE SOME DIFFICULT TO
PREDICT FLUCTUATIONS IN INTENSITY...IGOR IS EXPECTED TO REMAIN A
LARGE AND FORMIDABLE HURRICANE FOR THE NEXT 3 TO 4 DAYS. AFTER
THAT...INCREASING SOUTHWESTERLY SHEAR AND GRADUALLY COOLER WATERS
SHOULD LEAD TO WEAKENING OF THE CYCLONE...WITH THE WEAKENING
POSSIBLY GREATER THAN INDICATED IF THE 30 TO 45 KT OF SHEAR
PREDICTED BY THE GFS VERIFIES. THE GUIDANCE ALSO INDICATES THAT
EXTRATROPICAL TRANSITION WILL BE UNDERWAY BY DAY 5. THE OFFICIAL
FORECAST IS SLIGHTLY HIGHER THAN SOME OF THE STATISTICAL-DYNAMICAL
GUIDANCE BUT SIMILAR TO THE PREVIOUS INTENSITY FORECAST.
 
IGOR HAS BEEN WOBBLING ABOUT AN INITIAL MOTION OF 305/06. LITTLE HAS
CHANGED REGARDING THE OVERALL TRACK PHILOSOPHY. THE HURRICANE IS
EXPECTED TO MOVE NORTHWESTWARD AROUND THE WESTERN PERIPHERY OF A
SUBTROPICAL RIDGE DURING THE NEXT 72 HOURS. BEYOND 72 HOURS...IGOR
SHOULD BECOME EMBEDDED WITHIN THE MID-LATITUDE WEST-SOUTHWESTERLY
FLOW AHEAD OF A VIGOROUS SHORTWAVE TROUGH MOVING THROUGH THE
NORTHEASTERN U.S. AND THE CANADIAN MARITIMES...AND TURN NORTH AND
THEN NORTHEAST WITH INCREASING FORWARD SPEED. THE SPREAD IN THE
MODEL GUIDANCE HAS DECREASED SINCE YESTERDAY...WITH THE LATEST
SOLUTIONS TRENDING SLIGHTLY LEFTWARD AND TIGHTLY CLUSTERED AROUND
THE OFFICIAL FORECAST.
 
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/1500Z 21.0N  57.2W   120 KT
 12HR VT     17/0000Z 21.5N  58.3W   115 KT
 24HR VT     17/1200Z 22.4N  60.0W   120 KT
 36HR VT     18/0000Z 23.8N  61.7W   120 KT
 48HR VT     18/1200Z 25.3N  63.2W   120 KT
 72HR VT     19/1200Z 29.0N  65.0W   105 KT
 96HR VT     20/1200Z 33.5N  63.5W    95 KT
120HR VT     21/1200Z 39.0N  56.5W    80 KT
 
$$
FORECASTER KIMBERLAIN
 
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