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Hurricane IGOR


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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
 
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