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TROPICAL STORM CHANTAL DISCUSSION NUMBER  21
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT MON AUG 20 2001
 
HIGH-RESOLUTION VISIBLE SATELLITE IMAGERY AND REPORTS FROM AN AIR
FORCE HURRICANE HUNTER PLANE INDICATE THAT THE TROPICAL CYCLONE HAS
BECOME SLIGHTLY BETTER ORGANIZED.  ON SATELLITE...THE SYSTEM HAS A
COMMA-SHAPED CLOUD PATTERN AND THE CENTER IS NEAR THE EDGE OF THE
DENSE OVERCAST.  THE AIRCRAFT DATA SHOW THAT THE SOUTHERN PORTION OF
THE CIRCULATION...WHICH HAD BEEN PRACTICALLY NON-EXISTENT...HAS
BECOME DISTINCT.  OVER THE NORTHEAST QUADRANT...THE STRONGEST WINDS
ARE NOW CLOSER TO THE CENTER.  A GPS DROPSONDE MEASURED SURFACE
WINDS OF 50 KNOTS IN THE STRONG CONVECTION TO THE NORTHEAST OF THE
CENTER.  WATER VAPOR LOOPS SUGGEST THAT THE SHEAR IS DECREASING OVER
CHANTAL...AND THIS IS CONFIRMED BY SHEAR TENDENCY ANALYSES BY THE
UNIVERSITY OF WISCONSIN CIMSS AS SHOWN ON THEIR WEB SITE.
HOWEVER...THERE IS VERY LITTLE TIME FOR CHANTAL TO AVAIL ITSELF OF
MORE FAVORABLE CONDITIONS BEFORE MAKING LANDFALL OVER YUCATAN.
HOWEVER...ASSUMING THAT THE CYCLONE EMERGES OVER THE BAY OF
CAMPECHE...THERE WILL BE ANOTHER OPPORTUNITY FOR STRENGTHENING.

THE TRACK FORECAST AND REASONING ARE BASICALLY THE SAME AS BEFORE.  
THE NCEP GLOBAL MODEL BUILDS A 500 MB ANTICYLONE OVER THE NORTHERN 
GULF LATER IN THE FORECAST PERIOD.  THIS SHOULD PRECLUDE A 
SIGNIFICANT NORTHWARD MOVEMENT.  THE OFFICIAL TRACK FORECAST IS A 
BLEND OF THE LATEST DYNAMICAL GUIDANCE...AND SIMILAR TO THE PREVIOUS 
NHC FORECAST.

FORECASTER PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     20/2100Z 18.1N  87.3W    55 KTS
12HR VT     21/0600Z 18.9N  88.9W    50 KTS...INLAND
24HR VT     21/1800Z 19.5N  90.5W    45 KTS...INLAND
36HR VT     22/0600Z 20.0N  92.0W    50 KTS
48HR VT     22/1800Z 20.5N  93.5W    55 KTS
72HR VT     23/1800Z 21.0N  96.0W    70 KTS
 
 
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