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| #376223 (Received by flhurricane at: 10:43 AM 15.Sep.2010) TCDAT1 HURRICANE IGOR DISCUSSION NUMBER 30 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010 1100 AM AST WED SEP 15 2010 THE CLOUD PATTERN ASSOCIATED WITH IGOR WAS DETERIORATING DURING THE PAST SEVERAL HOURS...WITH CLOUD TOP TEMPERATURES WARMING AND A DRY SLOT EVIDENT NORTHWEST OF THE CENTER. SEVERAL MICROWAVE OVERPASSES ALSO INDICATED A FURTHER EROSION OF THE INNER EYEWALL AND THE FORMATION OF AN OUTER EYEWALL AT ABOUT 60-70 NMI RADIUS. SINCE ABOUT 1300 UTC...THERE APPEARS TO BE SOME EVIDENCE OF A RE- ORGANIZATION OF THE INNER CORE. DVORAK T-NUMBERS AT 1200 UTC ARE 5.5 AND 6.0 FROM SAB AND TAFB...RESPECTIVELY. BASED UPON THESE ESTIMATES...THE INITIAL WIND SPEED IS DECREASED TO 115 KT FOR THIS ADVISORY. THERE DO NOT APPEAR TO BE ANY NEGATIVE LARGE-SCALE FACTORS THAT COULD PRODUCE A SIGNIFICANT WEAKENING DURING THE NEXT TWO TO THREE DAYS. INSTEAD...FLUCTUATIONS IN INTENSITY ARE LIKELY TO BE GOVERNED BY INTERNAL DYNAMICS FOR WHICH PREDICTABILITY IS POOR. IN ABOUT 3 TO 4 DAYS...GLOBAL MODELS SHOW THAT IGOR SHOULD ENCOUNTER AN INCREASE IN SOUTHERLY SHEAR. THE OFFICIAL NHC INTENSITY FORECAST HAS BEEN LOWERED IN THE SHORT TERM BECAUSE OF THE CURRENT WEAKENING TREND. SHOULD THE CURRENT EYEWALL REPLACEMENT CYCLE END DURING THE NEXT DAY OR TWO...THERE MAY BE AN OPPORTUNITY FOR RE-INTENSIFICATION BEFORE GRADUAL WEAKENING COMMENCES LATER IN THE FORECAST PERIOD. THE INITIAL MOTION IS ABOUT THE SAME AS BEFORE...300/07...AND THE TRACK PHILOSOPHY IS ESSENTIALLY UNCHANGED. IGOR IS MOVING AROUND THE SOUTHWEST SIDE OF THE SUBTROPICAL RIDGE OVER THE EASTERN ATLANTIC AND SHOULD GRADUALLY ENTER A LARGE WEAKNESS OVER THE WESTERN ATLANTIC DURING THE NEXT COUPLE OF DAYS. THIS PATTERN SHOULD STEER IGOR NORTHWESTWARD AND THEN NORTH-NORTHWESTWARD... POSSIBLY WITH A SLIGHT INCREASE IN FORWARD SPEED. DURING THIS TIME...A SERIES OF SHORTWAVE TROUGHS MOVING THROUGH THE WEAKNESS IN THE WESTERN ATLANTIC SHOULD HAVE LITTLE IMPACT ON IGOR. HOWEVER... IN ABOUT 4-5 DAYS...DYNAMICAL MODELS ARE IN GOOD AGREEMENT ON THE PRESENCE OF A SHORTWAVE TROUGH MOVING THROUGH THE NORTHEASTERN UNITED STATES THAT SHOULD BEGIN TO INDUCE RECURVATURE. THERE ARE STILL SOME TIMING AND AMPLITUDE DIFFERENCES IN THE MODELS REGARDING THIS FEATURE...WHICH COULD AFFECT HOW CLOSE IGOR PASSES TO BERMUDA. THE OFFICIAL NHC TRACK FORECAST IS LARGELY UNCHANGED FROM THE PREVIOUS ADVISORY...CLOSE TO BUT JUST RIGHT OF THE MULTI-MODEL CONSENSUS. REGARDLESS OF THE EXACT TRACK...IGOR HAS A VERY LARGE WIND FIELD AND IS EXPECTED TO BRING ADVERSE CONDITIONS TO BERMUDA. FORECAST POSITIONS AND MAX WINDS INITIAL 15/1500Z 19.8N 55.0W 115 KT 12HR VT 16/0000Z 20.5N 56.1W 110 KT 24HR VT 16/1200Z 21.3N 57.5W 110 KT 36HR VT 17/0000Z 22.1N 59.1W 115 KT 48HR VT 17/1200Z 23.3N 60.8W 120 KT 72HR VT 18/1200Z 26.0N 63.5W 110 KT 96HR VT 19/1200Z 30.0N 65.0W 95 KT 120HR VT 20/1200Z 34.5N 63.5W 80 KT $$ FORECASTER KIMBERLAIN |
