023 
 WTNT41 KNHC 151439
 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