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| #375357 (Received by flhurricane at: 4:40 PM 11.Sep.2010) TCDAT1 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 |
