Hurricane IGOR

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HURRICANE IGOR DISCUSSION NUMBER  49
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST MON SEP 20 2010
 
DEEP CONVECTION HAS BEEN SPUTTERING NEAR THE CENTER OF IGOR OVER THE
PAST FEW HOURS...HOWEVER SATELLITE CLASSIFICATIONS AND EARLIER
SURFACE OBSERVATIONS FROM BERMUDA SUPPORT KEEPING IGOR AT HURRICANE
INTENSITY.  LITTLE CHANGE IN STRENGTH IS EXPECTED BEFORE IGOR
UNDERGOES EXTRATROPICAL TRANSITION...WHICH SHOULD BE COMPLETE BY 36
HOURS WHEN GLOBAL MODEL FIELDS SHOW THE CYCLONE BECOMING FULLY
EMBEDDED WITHIN A BAROCLINIC ZONE.  POST-TROPICAL IGOR IS EXPECTED
TO REMAIN A STRONG EXTRATROPICAL CYCLONE FOR A DAY OR TWO BEFORE
WEAKENING LATE IN THE PERIOD.
 
THE LATEST SATELLITE FIXES SUGGEST THAT THE FORWARD MOTION OF IGOR
HAS INCREASED...AND THE INITIAL MOTION ESTIMATE IS 025/17. IGOR
WILL CONTINUE TO ACCELERATE TOWARD THE NORTHEAST AS IT RECURVES
AHEAD OF A MID-LATITUDE TROUGH OVER THE CANADIAN MARITIMES DURING
THE NEXT COUPLE OF DAYS.  BY DAYS 3 AND 4 IGOR WILL TURN NORTHWARD
AND THEN NORTHWESTWARD AS IT INTERACTS WITH AN UPPER-LEVEL LOW
MOVING EASTWARD FROM NORTHERN QUEBEC INTO THE DAVIS STRAIT. THE
GLOBAL MODEL GUIDANCE SHOWS A FASTER FORWARD SPEED IN THE FIRST
COUPLE OF DAYS...AND THE OFFICIAL FORECAST HAS BEEN ADJUSTED IN
THAT DIRECTION AND LIES ON THE LEFT SIDE OF THE GUIDANCE
SUITE...BUT TO THE RIGHT OF THE GFS. FROM 48 HOURS ONWARD...THE NEW
FORECAST IS A BLEND OF THE PREVIOUS NHC FORECAST AND THE GFS
ENSEMBLE MEAN. HOWEVER...MODEL SPREAD IS QUITE LARGE AT THE END OF
THE PERIOD DUE TO DIFFERENCES IN HOW IGOR INTERACTS WITH THE UPPER
LOW...AND CONFIDENCE IN TRACK FORECAST NEAR THE END OF THE PERIOD
IS LOW.
 
TROPICAL STORM CONDITIONS ARE STILL BEING FELT ON BERMUDA...BUT
SHOULD GRADUALLY DIMINISH TODAY.  STRONG WINDS ARE POSSIBLE
ALONG THE COAST OF NEWFOUNDLAND AS IGOR PASSES BY...AND THE
CANADIAN HURRICANE CENTRE HAS ISSUED A TROPICAL STORM WATCH FOR A
PORTION OF THAT PROVINCE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/0900Z 34.2N  64.4W    65 KT
 12HR VT     20/1800Z 36.7N  62.4W    65 KT
 24HR VT     21/0600Z 40.6N  57.6W    65 KT
 36HR VT     21/1800Z 45.6N  50.8W    70 KT...POST-TROP/EXTRATROP
 48HR VT     22/0600Z 47.7N  44.5W    65 KT...POST-TROP/EXTRATROP
 72HR VT     23/0600Z 55.0N  37.0W    55 KT...POST-TROP/EXTRATROP
 96HR VT     24/0600Z 61.0N  41.0W    35 KT...POST-TROP/EXTRATROP
120HR VT     25/0600Z...DISSIPATED
 
$$
FORECASTER BRENNAN
 
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