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HURRICANE IRIS DISCUSSION NUMBER  10
NATIONAL WEATHER SERVICE MIAMI FL
11 PM EDT SAT OCT 06 2001
 
A RECONNAISSANCE PLANE GPS DROPSONDE INDICATES THAT THE SURFACE WIND
SPEED INCREASED TO 75 KNOTS OR SO AT ABOUT 21Z OVER A SMALL AREA
JUST NORTHEAST OF THE CENTER...ALONG WITH A CLOSED 12 MILE DIAMETER
EYE..AND 990 MB.  MICORWAVE IMAGERY ALSO SHOWS A WELL-DEFINED SMALL
EYE FEATURE AT THE SAME TIME.  SINCE THEN THE PRESSURE IS UP TO 993
MB AND RECON REPORTS THAT THE EYE IS NO LONGER WELL DEFINED.  THE
OFFICIAL ADVISORY WIND SPEED IS INCREASED TO 75 KNOTS EVEN THOUGH IT
MAY HAVE ONLY BEEN THAT HIGH FOR A FEW HOURS.  THE SHIPS MODEL AND
THE GFDL BRING THE WIND SPEED TO 100 KNOTS OR HIGHER IN A DAY OR
TWO...IF THE CENTER STAYS OVER THE WATER.  SINCE AIRCRAFT DATA AND
RECENT INFRARED IMAGERY IMPLIES A NOT VERY PERSISTENT PATTERN OF
DEEP CONVECTION...THE OFFICIAL FORECAST IS NOT AS AGGRESSIVE AS THE
GUIDANCE AND BRINGS THE WIND SPEED TO 90 KNOTS IN 48 HOURS.
 
AIRCRAFT FIXES GIVE AN INITIAL MOTION ESTIMATE IS 280/16...BASED ON
THE PAST 12 HOURS OF MOTION.  THE PAST 6 HOUR MOTION IS 270/16.  THE
GUIDANCE IS ONCE AGAIN TIGHTLY CLUSTERED TOWARD THE WEST-NORTHWEST
AND THEN WEST OVER THE NEXT 72 HOURS AS THE RIDGE TO THE NORTH IS
FORECAST TO STRENGTHEN.  THE FORECAST TRACK IS SIMILAR TO...AND AN
UPDATE OF...THE PREVIOUS ADVISORY.  IF THE SHORTER TERM 270 DEGREE
MOTION PERSISTS FOR 12 TO 24 HOURS...THE CENTER COULD PASS SOUTH OF
JAMAICA.  OTHERWISE THE FORECAST BRINGS THE CENTER OVER JAMAICAN IN
THE NEXT 12 HOURS.
 
FORECASTER LAWRENCE
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     07/0300Z 17.2N  74.8W    75 KTS
12HR VT     07/1200Z 17.9N  76.9W    75 KTS
24HR VT     08/0000Z 18.8N  79.5W    80 KTS
36HR VT     08/1200Z 19.1N  82.1W    85 KTS
48HR VT     09/0000Z 19.0N  84.6W    90 KTS
72HR VT     10/0000Z 19.0N  89.0W    45 KTS...INLAND
 
 
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