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Tropical Storm IGOR (Text)

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TROPICAL STORM IGOR DISCUSSION NUMBER  14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST SAT SEP 11 2010
 
IGOR IS VERY CLOSE TO BECOMING A HURRICANE.  SATELLITE IMAGES SHOW
THAT CONVECTION HAS INCREASED AROUND THE CENTER AND HAVE RECENTLY
SUGGESTED THAT AN EYEWALL COULD BE FORMING.  ALTHOUGH MOST OF THE
INTENSITY ESTIMATION TECHNIQUES SUGGEST IGOR IS A HURRICANE...IT IS
PREFERABLE TO WAIT AND SEE IF THE CONVECTION STICKS AROUND AND TO
GET MICROWAVE CONFIRMATION OF THE INNER CORE STRUCTURE.    

MOST OF THE ENVIRONMENTAL FACTORS NEAR THE CYCLONE SEEM RATHER
CONDUCIVE FOR STRENGTHENING.  GLOBAL MODELS ALL BUILD AN UPPER
ANTICYCLONE JUST TO THE NORTH OF IGOR...A RATHER FAVORABLE PATTERN
FOR THE DEVELOPMENT OF A MAJOR HURRICANE.  SSTS AND OCEAN HEAT
CONTENT ALSO INCREASE STEADILY ALONG THE FORECAST TRACK.  THE MOST
OBVIOUS INHIBITING FACTOR IS PERHAPS A WEDGE OF DRIER AIR THAT HAS
WORKED ITS WAY INTO THE NORTHERN PART OF THE CIRCULATION. 
HOWEVER...THAT DRY AIR PROBABLY WILL NOT BE ABLE TO MAKE IT INTO
THE INNER CORE WITHOUT SOME SHEAR...AND THAT DOES NOT SEEM LIKELY AT
THIS TIME.  THUS...THE INTENSITY FORECAST IS RAISED FROM THE
PREVIOUS ONE...BUT PEAKS BELOW THE LGEM AND SHIPS MODELS.  IT IS OF
NOTE THAT ALL OF THE GLOBAL MODELS SHOW THE DEVELOPMENT OF A LARGE
AND POWERFUL HURRICANE...AND THE FORECAST WIND RADII HAVE BEEN
INCREASED.

IGOR REMAINS ON TRACK AND IS MOVING 275/16.  THE SYNOPTIC STEERING
FOR THE NEXT SEVERAL DAYS APPEARS WELL DEFINED WITH A RIDGE TO THE
NORTH OF THE TROPICAL CYCLONE GUIDING THE CYCLONE GENERALLY
WESTWARD.  HOWEVER...THE STRENGTH OF THIS RIDGE IS CRITICAL TO WHEN
IGOR BEGINS A MORE WEST-NORTHWEST MOTION.  THE MODELS THAT MOVE THE
STORM FASTER TO THE WEST INITIALLY...SUCH AS THE NOGAPS OR
UKMET...ALLOW IGOR TO GET A LITTLE CLOSER TO THE NORTHERN LEEWARD
ISLANDS BEFORE MAKING A WEST-NORTHWEST TURN IN TWO OR THREE DAYS.
HOWEVER...ANOTHER GROUP OF MODELS...INCLUDING THE GFS/GFDL
SOLUTIONS...SHOW THAT TURN OCCURRING IN THE NEXT DAY OR TWO.   THE
MODEL SPREAD HAS INCREASED SINCE THE LAST ADVISORY...AND I HAVE
ELECTED NOT TO CHANGE THE FORECAST MUCH...WHICH REMAINS TO THE
SOUTH AND WEST OF THE DYNAMICAL MODEL CONSENSUS FOR NOW.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/2100Z 17.4N  41.2W    60 KT
 12HR VT     12/0600Z 17.5N  43.6W    70 KT
 24HR VT     12/1800Z 17.6N  46.4W    80 KT
 36HR VT     13/0600Z 17.7N  48.8W    90 KT
 48HR VT     13/1800Z 17.9N  51.0W   100 KT
 72HR VT     14/1800Z 18.8N  54.8W   115 KT
 96HR VT     15/1800Z 20.3N  57.7W   115 KT
120HR VT     16/1800Z 22.0N  60.5W   115 KT
 
$$
FORECASTER BLAKE
 
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