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HURRICANE IRIS DISCUSSION NUMBER  11
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT SUN OCT 07 2001

AFTER MOVING MOSTLY WESTWARD...EVEN WOBBLING A LITTLE SOUTH OF
WEST...THE HURRICANE APPEARS TO HAVE RESUMED A WEST-NORTHWEST MOTION 
OF ABOUT 285/15.  GLOBAL MODELS MAINTAIN A RIDGE TO THE NORTH OF THE 
IRIS DURING THE FORECAST PERIOD...AND THIS RIDGE IS PREDICTED TO 
STRENGTHEN A BIT OVER THE EASTERN GULF OF MEXICO IN A COUPLE OF 
DAYS.  BECAUSE OF THE MORE WESTWARD MOTION OVER THE PAST 
6-12 HOURS...THE OFFICIAL FORECAST TRACK HAS BEEN ADJUSTED JUST 
SLIGHTLY TO THE SOUTH OF THE PREVIOUS ONE.  THIS IS ROUGHLY IN THE 
MIDDLE OF THE NUMERICAL GUIDANCE SUITE WHICH IS FAIRLY TIGHTLY 
CLUSTERED.  THE AVN MODEL IS SOMEWHAT TO THE NORTH OF THE OFFICIAL 
FORECAST...HOWEVER THAT MODEL HAS EXHIBITED A SLIGHT NORTHWARD BIAS 
FOR IRIS THUS FAR.  

ALTHOUGH THE SATELLITE PRESENTATION HAS BEEN RATHER 
RAGGED-LOOKING...LATEST AERIAL RECONNAISSANCE OBSERVATIONS SUGGEST 
THAT IRIS IS MAINTAINING ITS STRENGTH.  THE EYE WALL IS STILL CLOSED 
AND...EVEN THOUGH THE HIGHEST FLIGHT LEVEL WINDS SO FAR ON THIS 
MISSION WERE 76 KNOTS...THE CENTRAL PRESSURE READING WAS DOWN TO 987 
MILLIBARS.  RECENTLY...A GPS DROPSONDE SHOWED A SPOT SURFACE WIND 
SPEED OF 70 KNOTS JUST NORTH OF THE CENTER.  IT IS PRESUMED THAT 
SLIGHTLY STRONGER SURFACE WINDS EXIST SOMEWHERE OVER THE NORTHERN 
SEMICIRCLE OF THE HURRICANE.  AN UPPER-LEVEL CYCLONE HAS BEEN 
ROTATING AROUND THE SOUTHERN SEMICIRCLE OF IRIS...AND PERHAPS 
INTERFERING WITH THE OUTFLOW.  THAT LOW IS NOW SOUTHEAST OF THE 
HURRICANE...AND APPEARS TO BE INCREASING ITS SEPARATION FROM IRIS.  
WE ANTICIPATE THAT THE ENVIRONMENT WILL BECOME MORE FAVORABLE FOR 
INTENSIFICATION AS THE HURRICANE ENTERS THE NORTHWEST CARIBBEAN SEA. 
THE SHIPS MODEL BRINGS IRIS TO MAJOR HURRICANE STATUS IN 48 HOURS... 
AND THE OFFICIAL FORECAST IS JUST SLIGHTLY MORE CONSERVATIVE.

FORECASTER PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     07/0900Z 17.1N  76.1W    75 KTS
12HR VT     07/1800Z 17.7N  78.0W    80 KTS
24HR VT     08/0600Z 18.3N  80.7W    85 KTS
36HR VT     08/1800Z 18.5N  83.5W    90 KTS
48HR VT     09/0600Z 18.5N  86.0W    95 KTS
72HR VT     10/0600Z 18.5N  90.0W    45 KTS...INLAND
 
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