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Hurricane IGOR


ZCZC MIATCDAT1 ALL
TTAA00 KNHC DDHHMM
HURRICANE IGOR DISCUSSION NUMBER  40
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST FRI SEP 17 2010
 
INFRARED SATELLITE IMAGERY INDICATES IGOR HAS BECOME BETTER
ORGANIZED WITH A RING OF CONVECTIVE CLOUD TOPS OF -70C AND COLDER
ENCIRCLING A 20-25 NMI DIAMETER EYE THAT HAS BECOME MORE DISTINCT
DURING THE PAST COUPLE OF HOURS. A 17/2026Z AMSU OVERPASS ALSO
INDICATED THE UPPER-LEVEL WARM CORE HAS STRENGTHENED AND MOVED
UPWARD FROM 300 MB TO THE 200 MB...SUGGESTING THAT IGOR IS LIKELY
STRENGTHENING. AN AIR FORCE RESERVE RECON AIRCRAFT WILL BE
INVESTIGATING IGOR AROUND 06Z AND PROVIDE A BETTER INTENSITY
ESTIMATE.
 
THE INITIAL MOTION ESTIMATE IS 315/11. IGOR HAS MADE A TROCHOIDAL
WOBBLE TO THE RIGHT OF THE PREVIOUS FORECAST TRACK...BUT THIS IS
LIKELY JUST A TEMPORARY MOTION. IGOR IS EXPECTED TO MOVE BACK ON OR
CLOSE TO THE PREVIOUS ADVISORY TRACK BASED ON 00Z UPPER-AIR DATA
FROM BERMUDA SHOWING 24-HOUR MID-LEVEL HEIGHTS HAVE INCREASED BY 20
METERS AND WINDS HAVE SHIFTED AROUND TO AN EASTERLY DIRECTION...
WHICH INDICATES THE SUBTROPICAL RIDGE HAS BUILT WESTWARD TO THE
NORTH OF BERMUDA. UNFORTUNATELY...THIS RIDGING PATTERN WILL BE
SHORT-LIVED DUE TO A STRONG SHORTWAVE TROUGH CURRENTLY LOCATED JUST
OFF THE U.S. EAST COAST FORECAST BY ALL THE GLOBAL AND REGIONAL
MODELS TO CONTINUE TO MOVE EASTWARD AND CREATE A WEAKNESS IN THE
RIDGE BETWEEN 60W-70W LONGITUDE BY 24 HOURS. THIS WILL ALLOW IGOR
TO GRADUALLY MOVE NORTHWARD THROUGH THIS BREAK IN THE SUBTROPICAL
RIDGE PATTERN AND PASS VERY CLOSE TO BERMUDA IN ABOUT 48 HOURS. BY
72 HOURS...IGOR IS FORECAST TO BE CAPTURED BY A SECOND SHORTWAVE
TROUGH AND BE ACCELERATED OVER THE FAR NORTH ATLANTIC AS A POWERFUL
EXTRATROPICAL LOW PRESSURE SYSTEM. THE OFFICIAL FORECAST IS SIMILAR
TO THE PREVIOUS ADVISORY AND IS CLOSE TO THE MODEL CONSENSUS.
 
IGOR IS EXHIBITING AN IMPRESSIVE OUTFLOW PATTERN THAT CONTINUES TO
EXPAND IN ALL QUADRANTS. THE HURRICANE IS EXPECTED TO MAINTAIN THIS
FAVORABLE OUTFLOW REGIME FOR THE NEXT 36-48 HOURS.  AFTERWARDS...
INCREASING SOUTHWESTERLY UPPER-LEVEL FLOW AHEAD OF A MID- TO
UPPER-LEVEL TROUGH WILL INCREASE THE SHEAR ACROSS THE CYCLONE...
WHICH COUPLED WITH DECREASING SSTS...SHOULD INDUCE WEAKENING. BY 96
HOURS...IGOR IS FORECAST TO TRANSITION INTO A LARGE AND POWERFUL
EXTRATROPICAL CYCLONE OVER THE FAR NORTH ATLANTIC WHEN IGOR MERGES
WITH A FRONTAL SYSTEM. THE OFFICIAL INTENSITY FORECAST IS SIMILAR
TO THE SHIPS INTENSITY MODEL.

THE EXTRATROPICAL FORECAST TRACK AND INTENSITIES AT 96 AND 120 HOURS
IS BASED ON GUIDANCE FROM THE NOAA OCEAN PREDICTION CENTER.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/0300Z 24.6N  62.0W    95 KT
 12HR VT     18/1200Z 25.6N  63.2W   100 KT
 24HR VT     19/0000Z 27.1N  64.4W   105 KT
 36HR VT     19/1200Z 29.1N  65.0W   105 KT
 48HR VT     20/0000Z 31.7N  64.5W   100 KT
 72HR VT     21/0000Z 36.2N  61.2W    85 KT
 96HR VT     22/0000Z 45.0N  50.0W    65 KT...POST-TROP/EXTRATROP
120HR VT     23/0000Z 52.5N  42.0W    65 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER STEWART
 
NNNN


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Page last modified: Friday, 15-Apr-2011 12:09:14 UTC