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Hurricane IGOR


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HURRICANE IGOR DISCUSSION NUMBER  37
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST FRI SEP 17 2010
 
THE CLOUD PATTERN OF IGOR HAS BECOME A LITTLE LESS ORGANIZED
OVERNIGHT WITH WEAKER EYEWALL CONVECTION NOTED.   SATELLITE
CLASSIFICATIONS RANGE FROM 102 KT FROM TAFB AND SAB...TO UW-CIMSS
ADT NUMBERS NEAR 125 KT.  A BLEND OF THESE DATA SUGGEST THAT
KEEPING THE INITIAL INTENSITY AT 110 KT IS REASONABLE.  DATA FROM
NOAA BUOY 41044 SUGGESTED THAT THE PRESSURE WAS SEVERAL MB LOWER
THAN THE LAST AIRCRAFT FIX FROM THIS AFTERNOON...WHEN THE INTENSITY
WAS ALSO NEAR 110 KT.  
 
IGOR IS LIKELY TO REMAIN A MAJOR HURRICANE FOR THE NEXT TWO TO THREE
DAYS WHILE IT STAYS IN A WARM WATER AND MOSTLY LIGHT SHEAR
ENVIRONMENT.  THEREAFTER...WATERS GRADUALLY COOL...WHILE
SOUTHWESTERLY SHEAR IS FORECAST TO INCREASE.  MODEL GUIDANCE IS IN
RELATIVELY GOOD AGREEMENT ON THIS SCENARIO...AND THE NHC FORECAST
IS CLOSE TO THE PREVIOUS ONE.  REGARDLESS OF THE EXACT INTENSITY...
IGOR IS EXPECTED TO BE A VERY LARGE AND DANGEROUS HURRICANE WHEN IT
PASSES CLOSE TO BERMUDA.  IN THE LONG RANGE... EXTRATROPICAL
TRANSITION SHOULD BE COMPLETED AROUND 120 HOURS...AND GLOBAL MODELS
ARE SHOWING A RATHER INTENSE CYCLONE AT THAT TIME.
 
THE INITIAL MOTION HAS SHIFTED A LITTLE TO THE LEFT OR 305 DEGREES
AT 8 KT.  THE SYNOPTIC STEERING HAS BEEN RELATIVELY WELL DEFINED
FOR THE LAST SEVERAL DAYS AS IGOR TRAVELS AROUND THE SOUTHWESTERN
PERIPHERY OF A SUBTROPICAL RIDGE.  A TURN TO THE NORTH SHOULD OCCUR
IN ABOUT TWO DAYS...WITH ALMOST ALL OF THE MODEL GUIDANCE VERY
CLOSE TO BERMUDA IN ABOUT 3 DAYS TIME. THE NEW NHC FORECAST IS
BASICALLY AN UPDATE OF THE PREVIOUS ONE FOR THE FIRST FEW DAYS. 
AFTER PASSING BERMUDA...IGOR SHOULD ACCELERATE AS IT BEGINS TO GET
CAUGHT UP INTO THE MID-LATITUDE SOUTHWESTERLIES.  MOST OF THE
GUIDANCE IS A LITTLE FASTER IN THE LONG RANGE...AND THE OFFICIAL
FORECAST GOES ALONG WITH THAT IDEA.  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/0900Z 22.4N  59.4W   110 KT
 12HR VT     17/1800Z 23.2N  60.8W   110 KT
 24HR VT     18/0600Z 24.5N  62.5W   110 KT
 36HR VT     18/1800Z 26.1N  64.0W   105 KT
 48HR VT     19/0600Z 27.8N  64.9W   105 KT
 72HR VT     20/0600Z 32.5N  64.5W    95 KT
 96HR VT     21/0600Z 40.0N  56.0W    80 KT
120HR VT     22/0600Z 50.0N  45.0W    70 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BLAKE/BRENNAN
 
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