Hurricane IGOR

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HURRICANE IGOR DISCUSSION NUMBER  24
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST MON SEP 13 2010
 
MICROWAVE AND GEOSTATIONARY SATELLITE IMAGERY SUGGESTS THAT AN
EYEWALL REPLACEMENT CYCLE MAY HAVE BEGUN.  TRMM...WINDSAT...AND
SSMIS PASSES FROM ABOUT 5-6 HOURS AGO ALL INDICATED THAT A
SECONDARY EYEWALL WAS BEGINNING TO FORM...AND MORE RECENTLY
CONVECTIVE TOPS AROUND THE EYE HAVE BEEN WARMING.  SUBJECTIVE
DVORAK FINAL-T ESTIMATES HAD FALLEN TO T6.0 TAFB AND SAB AT 0000
UTC...AND THE LATEST OBJECTIVE ADT ESTIMATE IS T6.0/6.4.  BASED ON
THESE DATA...THE INITIAL INTENSITY IS LOWERED TO 120 KT.  FOLLOWING
A CONSENSUS OF THE INTENSITY GUIDANCE...THE OFFICIAL FORECAST KEEPS
IGOR AT THIS INTENSITY FOR THE NEXT 24 HOURS OR SO...BUT IT IS
POSSIBLE THAT ADDITIONAL WEAKENING COULD OCCUR WHILE THE EYEWALL
REPLACEMENT IS IN PROGRESS.  SINCE IGOR IS STILL EXPECTED TO BE
OVER WARM OCEAN WATERS AND REMAIN IN A LOW SHEAR ENVIRONMENT...THE
FORECAST ALLOWS FOR THE POSSIBILITY OF SOME RE-STRENGTHENING
BETWEEN 36-48 HOURS...WHICH IS HINTED AT IN THE SHIPS OUTPUT. 
WEAKENING IS THEN INDICATED DURING DAYS 3 THROUGH 5...BUT IT IS
CONSERVATIVE AND STILL LIES JUST ABOVE THE UPPER BOUND OF THE
GUIDANCE.
 
IGOR JUST WILL NOT BUDGE VERY MUCH TO THE NORTH AND IS MOVING 275
DEGREES AT 8 KT.  THE UKMET MODEL HAS CAPTURED THIS MOTION WELL
OVER THE PAST COUPLE OF DAYS AND HAS CONSISTENTLY BEEN LOCATED ON
THE SOUTHERN EDGE OF THE GUIDANCE ENVELOPE.  SINCE THERE IS STILL
NO CLEAR EVIDENCE OF THE BEGINNING OF A TURN...THE NHC FORECAST
TRACK LIES ALONG THE SOUTHERN PERIPHERY OF THE TRACK GUIDANCE FOR
THE FIRST 24 HOURS...ALTHOUGH STILL NOT AS FAR SOUTH AS THE UKMET.
A TURN TOWARD THE NORTHWEST IS EXPECTED BY 36 HOURS WHEN IGOR
SHOULD HAVE REACHED THE BREAK IN THE SUBTROPICAL RIDGE.  THE SPREAD
IN THE MODELS FROM DAYS 3 THROUGH 5 HAS AGAIN TIGHTENED...AND THE
OFFICIAL FORECAST IS CHANGED LITTLE FROM THE PREVIOUS ONE.  THIS
FORECAST ALSO LIES CLOSE TO A MULTI-MODEL CONSENSUS THAT EXCLUDES
THE GFDN...WHICH HAS BEEN FASTER THAN THE OTHER GUIDANCE FOR
SEVERAL CYCLES.
 
LARGE SWELLS FROM IGOR WILL BEGIN AFFECTING THE LEEWARD ISLANDS
TOMORROW AND REACH PUERTO RICO AND THE VIRGIN ISLANDS BY WEDNESDAY.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/0300Z 17.7N  51.2W   120 KT
 12HR VT     14/1200Z 18.0N  52.3W   120 KT
 24HR VT     15/0000Z 18.8N  53.7W   120 KT
 36HR VT     15/1200Z 19.9N  55.2W   125 KT
 48HR VT     16/0000Z 21.1N  56.6W   125 KT
 72HR VT     17/0000Z 24.0N  59.5W   115 KT
 96HR VT     18/0000Z 27.0N  62.5W   105 KT
120HR VT     19/0000Z 30.5N  64.5W    95 KT
 
$$
FORECASTER BERG
 
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