HURRICANE IGOR SPECIAL DISCUSSION NUMBER  18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
130 PM AST SUN SEP 12 2010

SATELLITE IMAGERY AND THE UW-CIMSS ADVANCED DVORAK TECHNIQUE
INDICATE THAT IGOR HAS CONTINUED TO RAPIDLY INTENSIFY AND IS NOW A
CATEGORY FOUR HURRICANE. THE VISIBLE AND BD-CURVE INFRARED 
ENHANCEMENT PICTURES REVEAL A CLEAR 20 NMI DIAMETER EYE WITH A
SURROUNDING INTENSE INNER CORE RING OF -80 DEGREE CELSIUS CLOUD TOP
TEMPERATURES.  THE OFFICIAL INTENSITY FORECAST HAS BEEN MODIFIED TO
INDICATE SOME ADDITIONAL INTENSIFICATION DURING THE NEXT 3 DAYS AND
THEN SHOWS A SLIGHT DECREASE AT DAYS 4 AND 5.  ALSO...FLUCTUATIONS
IN STRENGTH DUE TO EYEWALL REPLACEMENT CYCLES ARE POSSIBLE...BUT
THERE IS LITTLE SKILL IN FORECASTING THE TIMING OF THESE CYCLES.  
THE WIND RADII FORECAST HAS ALSO BEEN ADJUSTED TO ACCOUNT FOR THE
INCREASE IN THE INTENSITY.  THE OFFICIAL NHC TRACK FORECAST REMAINS
UNCHANGED FROM THE PREVIOUS ADVISORY. 

FORECAST POSITIONS AND MAX WINDS

INITIAL      12/1830Z 17.7N  46.1W   115 KT
12HR VT     13/0000Z 17.8N  47.5W   125 KT
24HR VT     13/1200Z 18.0N  49.8W   125 KT
36HR VT     14/0000Z 18.4N  51.8W   125 KT
48HR VT     14/1200Z 19.0N  53.6W   130 KT
72HR VT     15/1200Z 20.7N  56.7W   130 KT
96HR VT     16/1200Z 22.6N  59.6W   125 KT
120HR VT     17/1200Z 24.5N  62.5W   125 KT

$$
FORECASTER ROBERTS/BRENNAN