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| #376286 (Received by flhurricane at: 4:38 PM 15.Sep.2010) TCDAT1 HURRICANE IGOR DISCUSSION NUMBER 31 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010 500 PM AST WED SEP 15 2010 INFRARED SATELLITE PICTURES INDICATE THAT IGOR IS MAINTAINING ITS CONVECTIVE ORGANIZATION...WITH INNER CORE CONVECTION MORE VIGOROUS THAN EARLIER. HOWEVER...VISIBLE SATELLITE IMAGES SUGGEST THAT THE EYEWALL REPLACEMENT CYCLE IGOR IS EXPERIENCING IS STILL OCCURRING. A DISTINCT BUT PARTIAL INNER EYEWALL IS EVIDENT AND AN OUTER EYEWALL NOW AT 30-40 NM RADIUS SEEMS TO BE GRADUALLY CONTRACTING. SUBJECTIVE DVORAK CLASSIFICATIONS ARE AT 5.5 AND 6.0 FROM SAB AND TAFB...RESPECTIVELY...WHILE THE LATEST 3-HOURLY AVERAGED ADT VALUE IS CLOSE TO 6.0. THESE ESTIMATES ARE THE BASIS FOR KEEPING THE INITIAL INTENSITY AT 115 KT FOR THIS ADVISORY. THERE ARE NO OBVIOUS LARGE-SCALE FACTORS THAT COULD CAUSE A SIGNIFICANT WEAKENING OF IGOR DURING THE NEXT 2-3 DAYS. ANY CHANGES IN INTENSITY DURING THIS TIME ARE MOST LIKELY TO BE RELATED TO INNER CORE DYNAMICS FOR WHICH PREDICTABILITY IS LOW. IN 3-4 DAYS...GLOBAL DYNAMICAL MODELS CONTINUE TO SHOW AN INCREASE IN SOUTHERLY SHEAR...AND IGOR SHOULD REACH MARGINAL SEA SURFACE TEMPERATURES TOWARD THE END OF THE PERIOD. THE STATISTICAL-DYNAMICAL GUIDANCE RESPONDS TO THESE FACTORS BY SHOWING A GRADUAL WEAKENING BEYOND 72 HOURS. THE OFFICIAL NHC INTENSITY IS BASICALLY UNCHANGED...WITH THE FORECAST STILL INDICATING SOME POTENTIAL FOR RE-INTENSIFICATION IN THE SHORT TERM AFTER THE CURRENT EYEWALL REPLACEMENT CYCLE ENDS. THERE HAS BEEN LITTLE CHANGE TO THE MOTION...AND THE LATEST ESTIMATE IS 295/07. IGOR IS MOVING AROUND THE SOUTHWEST PERIPHERY OF THE SUBTROPICAL RIDGE OVER THE EASTERN ATLANTIC AND IS GRADUALLY ENTERING A PRONOUNCED WEAKNESS IN THE WESTERN ATLANTIC. THIS SYNOPTIC PATTERN SHOULD STEER IGOR ON A NORTHWESTWARD AND THEN NORTH-NORTHWESTWARD COURSE DURING THE NEXT 2-3 DAYS. DURING THIS TIME...SEVERAL SHORTWAVE TROUGHS MOVING THROUGH THE WEAKNESS IN THE WESTERN ATLANTIC SHOULD HAVE LITTLE EFFECT ON IGOR. HOWEVER... DYNAMICAL MODELS ARE IN GENERALLY GOOD AGREEMENT THAT A VIGOROUS SHORTWAVE TROUGH MOVING THROUGH THE NORTHEASTERN STATES/CANADIAN MARITIMES IN ABOUT 4-5 DAYS SHOULD BEGIN TO INDUCE RECURVATURE. THE GFS/HWRF/GFDL HAVE BEEN INDICATING A MORE ROBUST SHORTWAVE FEATURE AND A SHARPER RECURVATURE DURING THE PAST SEVERAL RUNS. ON THE OTHER HAND...THE UKMET...ECMWF...AND THE ECMWF ENSEMBLE MEAN HAVE HAD A WEAKER AND MORE PROGRESSIVE SHORTWAVE THAT COULD DELAY RECURVATURE AND ALLOW FOR A MORE WESTWARD TRACK. THE OFFICIAL NHC TRACK FORECAST REMAINS ABOUT THE SAME AS BEFORE AND IS VERY NEAR THE MULTI-MODEL CONSENSUS...CONTINUING TO SHOW IGOR PASSING CLOSE TO BERMUDA IN ABOUT 4 DAYS. FORECAST POSITIONS AND MAX WINDS INITIAL 15/2100Z 20.1N 55.6W 115 KT 12HR VT 16/0600Z 20.6N 56.7W 110 KT 24HR VT 16/1800Z 21.4N 58.2W 115 KT 36HR VT 17/0600Z 22.4N 59.8W 120 KT 48HR VT 17/1800Z 23.5N 61.5W 120 KT 72HR VT 18/1800Z 26.5N 64.0W 105 KT 96HR VT 19/1800Z 31.0N 65.0W 95 KT 120HR VT 20/1800Z 36.0N 61.5W 80 KT $$ FORECASTER KIMBERLAIN |
