HOME	ARCHIVES	FORECASTS	IMAGERY	ABOUT TPC	RECONNAISSANCE

ZCZC MIATCDAT5 ALL
TTAA00 KNHC DDHHMM
HURRICANE ISIDORE DISCUSSION NUMBER  25
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT SUN SEP 22 2002
 
THE INITIAL MOTION ESTIMATE IS 265/06 BASED ON THE PAST 12 HOUR
MOTION.  THE LATEST TRACK GUIDANCE IS IN GOOD AGREEMENT ABOUT MORE
SOUTHWARD COMPONENT OF MOTION THAN THE PREVIOUS GUIDANCE.  THERE IS 
A MID LEVEL RIDGE TO THE NORTH OF ISIDORE ORIENTED SOUTHWEST TO 
NORTHEAST FOR THE FIRST 24 HOURS THAT MIGHT EXPLAIN THE MORE 
SOUTHWARD MOTION.  IN ANY CASE...MOST OF THE GLOBAL MODELS MOVE THE 
CENTER SOUTHWESTWARD OVER THE NORTHWEST TIP OF THE YUCATAN 
PENINSULA.  THE MODELS THEN SHOW A NORTHWESTWARD TURN AFTER 48 HOURS 
IN RESPONSE TO AN EROSION OF THE RIDGE BY THE NEXT APPROACHING SHORT 
WAVE IN THE WESTERLIES.  THE OFFICIAL TRACK IS SHIFTED A LITTLE TO 
THE LEFT OF THE PREVIOUS ADVISORY AND BRINGS THE CENTER TO WITHIN 20 
N MI OF THE NORTHEAST YUCATAN COAST IN 24 HOURS.  EXCEPT FOR THE 
NEED TO MAINTAIN SOME CONTINUITY WITH THE PREVIOUS ADVISORY...I 
WOULD MOVE THE CENTER OVER THE NORTHWEST YUCATAN PENINSULA.
 
A RECON DROP IN THE CENTER GAVE 936 MB AT 07Z.  THIS IS ABOUT 11 MB
DROP IN SIX HOURS.   HOWEVER WIND MEASUREMENTS FROM THE AIRCRAFT
DO NOT SHOW THAT THE WINDS HAVE INCREASED FROM OUR PREVIOUS ADVISORY
VALUE OF 110 KNOTS.  IN FACT GPS DROPS FROM THE AIRCRAFT SO FAR HAVE
A HARD TIME SUPPORTING 110 KNOTS AT THE SURFACE ALTHOUGH WINDS ARE
NEAR 110 KNOTS IN A NARROW LAYER ABOVE THE SURFACE.  PERHAPS THE
SURFACE WINDS WILL SHORTLY RESPOND TO THE PRESSURE FALL.  VERTICAL
SHEAR IS SMALL THROUGH 72 HOURS.  THE CENTRAL DENSE OVERCAST FEATURE
IS IMPRESSIVELY LARGE...COLD AND SYMMETRIC.  THE OFFICIAL 12 HOUR
FORECAST IS FOR 115 KNOTS...NOT AS HIGH AS THE 125 KNOTS ALLOWED BY
THE STANDARD PRESSURE WIND RELATIONSHIP FOR 937 MB.  ON THE OTHER
HAND IT IS ALSO POSSIBLE THAT THE CURRENT INTERACTION WITH THE
YUCATAN PENINSULA WILL LIMIT THE STRENGTHENING.  THERE IS ALSO THE
OPPORTUNITY FOR ADDITIONAL STRENGTHENING AFTER 36 HOURS AS THE
CENTER IS FORECAST TO BEGIN MOVING AWAY FROM LAND.
 
FORECASTER LAWRENCE
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     22/0900Z 22.0N  87.9W   110 KTS
12HR VT     22/1800Z 21.8N  88.9W   115 KTS
24HR VT     23/0600Z 21.5N  90.1W   120 KTS
36HR VT     23/1800Z 21.2N  90.8W   120 KTS
48HR VT     24/0600Z 21.2N  91.4W   125 KTS
72HR VT     25/0600Z 22.0N  92.5W   125 KTS
 
 
NNNN