Hurricane IGOR

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HURRICANE IGOR DISCUSSION NUMBER  15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST SAT SEP 11 2010
 
THE CLOUD PATTERN ASSOCIATED WITH IGOR HAS INCREASED IN ORGANIZATION
DURING THE PAST SEVERAL HOURS.  A TIGHTLY-COILED BAND...WITH CLOUD
TOP TEMPERATURES TO -85C...WRAPS AROUND THE EASTERN SEMICIRCLE INTO
A DEVELOPING CENTRAL DENSE OVERCAST.  AN EYE FEATURE HAS ALSO BEEN
BRIEFLY INTERMITTENT IN CONVENTIONAL SATELLITE IMAGERY...AND A
NUMBER OF MICROWAVE PASSES SEVERAL HOURS AGO REVEALED A DISTINCT
CONVECTIVE RING SURROUNDING THE CENTER.  SUBJECTIVE DVORAK T-NUMBERS
AT 0000 UTC WERE A CONSENSUS 4.0 FROM BOTH SATELLITE AGENCIES...AND
3-HOURLY AVERAGED ADT VALUES FROM UW-CIMSS ARE 4.3.  THE INITIAL
INTENSITY IS RAISED TO 65 KT THIS ADVISORY...MAKING IGOR THE FOURTH
HURRICANE OF THE 2010 ATLANTIC HURRICANE SEASON. THE UNDERLYING
OCEAN ONLY GETS WARMER ALONG THE FORECAST TRACK OF IGOR...PEAKING
AROUND 29C IN ABOUT 3 DAYS.  THAT...COMBINED WITH A LIGHT SHEAR
ENVIRONMENT...WOULD FAVOR A STRENGTHENING TREND FOR THE NEXT FEW
DAYS...AND NEARLY ALL THE INTENSITY GUIDANCE MAKES IGOR A MAJOR
HURRICANE BY 72 HOURS. THEREAFTER...WHILE FLUCTUATIONS IN INTENSITY
MAY OCCUR...IGOR IS EXPECTED TO MAINTAIN MAJOR HURRICANE STATUS AND
BE A LARGE HURRICANE OVER THE CENTRAL NORTH ATLANTIC.
 
IGOR HAS MAINTAINED ROUGHLY THE SAME MOTION...275/15...THOUGH
PERHAPS A TAD SLOWER THAN EARLIER.  SUBTROPICAL RIDGING NORTH OF
THE CYCLONE SHOULD BE THE DOMINANT STEERING FEATURE FOR THE NEXT 2
TO 3 DAYS...CARRYING IGOR ON A GENERAL WESTWARD TRACK.  BEYOND THIS
TIME...DYNAMICAL MODELS SHOW IGOR SLOWING AND TURNING WEST-
NORTHWESTWARD AS IT APPROACHES AND THEN MOVES INTO A SUBSTANTIAL
BREAK IN THE SUBTROPICAL RIDGE.  AS WAS THE CASE IN THE PREVIOUS
MODEL CYCLE...THERE CONTINUES TO BE CONSIDERABLE SPREAD IN THE
TRACK GUIDANCE...WITH THE GFDL/HWRF THE RIGHTMOST OF MODEL
SOLUTIONS AND THE UKMET/NOGAPS THE LEFTMOST.  THESE DIFFERENCES
SEEM TO HINGE ON THE STRENGTH AND POSITION OF THE SUBTROPICAL
RIDGE...WITH THE FORMER MODELS FORECASTING A WEAKER RIDGE DISPLACED
TO THE EAST WHILE LATTER INDICATE A MORE ROBUST RIDGE EXTENDING
FARTHER WEST.  THE OFFICIAL NHC FORECAST TRACK HAS BEEN ADJUSTED TO
THE RIGHT...FOLLOWING THE TREND IN THE GUIDANCE... BUT IS NOT AS
FAR RIGHT AS THE MULTI-MODEL CONSENSUS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/0300Z 17.7N  42.5W    65 KT
 12HR VT     12/1200Z 17.8N  44.8W    75 KT
 24HR VT     13/0000Z 17.9N  47.4W    80 KT
 36HR VT     13/1200Z 18.1N  49.7W    90 KT
 48HR VT     14/0000Z 18.4N  51.9W   100 KT
 72HR VT     15/0000Z 19.5N  55.0W   110 KT
 96HR VT     16/0000Z 21.5N  58.0W   115 KT
120HR VT     17/0000Z 23.5N  61.0W   115 KT
 
$$
FORECASTER KIMBERLAIN
 
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