HOME	ACTIVE CYCLONES	FORECASTS	IMAGERY	ABOUT TPC	RECONNAISSANCE

ZCZC MIATCDAT3 ALL
TTAA00 KNHC DDHHMM
HURRICANE IRENE DISCUSSION NUMBER  17
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT SUN OCT 17 1999
 
WHILE A BURST OF STRONG CONVECTION HAS OCCURRED NEAR THE CENTER OF
IRENE OVER THE PAST FEW HOURS...IT IS NOW WEAKENING AND BOTH THE
RADAR AND SATELLITE PRESENTATIONS REMAIN UNIMPRESSIVE.  HOWEVER...
THE HURRICANE HUNTER AIRCRAFT RECENTLY REPORTED 850 MB WINDS AS
HIGH AS 71 KT AND A MINIMUM CENTRAL PRESSURE OF 982 MB. IT IS LIKELY
THE DRY AIR SEEN IN WATER VAPOR IMAGERY SOUTH AND WEST OF IRENE IS
ENTRAINING INTO THE HURRICANE AND SUPPRESSING THE CONVECTION. THE
INITIAL INTENSITY REMAINS AT 65 KT.

THE INITIAL MOTION IS 360/08. WATER VAPOR IMAGERY INDICATES A TROUGH
OVER THE CENTRAL U.S. HEADING FOR IRENE...ALONG WITH THE ASSOCIATED
COLD FRONT SEEN ON SURFACE ANALYSES. A BROAD EASTWARD-MOVING RIDGE
IS EVIDENT IN THE IMAGERY WITH AN AXIS ALONG 70W. THIS COMBINATION
OF FEATURES SHOULD GRADUALLY TURN IRENE TO THE NORTHEAST WITH
ACCELERATION OVER THE NEXT 36 HR. THE OFFICIAL FORECAST TRACK
REFLECTS THIS AND IS IN GOOD AGREEMENT WITH MODEL GUIDANCE. THERE
ARE DISAGREEMENTS IN THE LARGE SCALE GUIDANCE AS TO THE EVENTUAL
FATE OF IRENE NEAR THE 36-48 HR FORECASTS.  THE ECMWF...UKMET...
AND ENVIRONMENT CANADA GLOBAL MODEL TRANSFORM IRENE INTO A LARGE 
AND VICIOUS EXTRATROPICAL LOW...WHILE THE AVN...NOGAPS...AND ETA
FAVOR A WEAKER AND MORE SHEARED OUT SOLUTION. THE NHC TRACK AND
INTENSITY FORECASTS ASSUME THE STRONGER SCENARIO.

ALTHOUGH IRENE SHOULD PASS ACROSS THE WESTERN EDGE OF THE GULF
STREAM BEFORE LANDFALL...THE LACK OF ORGANIZATION SHOULD LIKELY
PREVENT SIGNIFICANT STRENGTHENING. A COMBINATION OF LAND INTERACTION
...INCREASING SHEAR...AND COLDER AIR AND WATER SHOULD CAUSE IRENE 
TO WEAKEN AFTER LANDFALL. THE INTENSITY FORECAST CALLS FOR LITTLE
CHANGE IN STRENGTH BEFORE LANDFALL...AND EXTRATROPICAL TRANSITION
AFTER LANDFALL.

BEVEN/GUINEY
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     17/0900Z 30.7N  79.9W    65 KTS
12HR VT     17/1800Z 32.0N  79.7W    65 KTS
24HR VT     18/0600Z 34.8N  77.4W    65 KTS...INLAND
36HR VT     18/1800Z 39.0N  70.5W    55 KTS...EXTRATROPICAL
48HR VT     19/0600Z 44.0N  61.0W    50 KTS...EXTRATROPICAL
 
NNNN