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TROPICAL STORM CHANTAL DISCUSSION NUMBER  18
NATIONAL WEATHER SERVICE MIAMI FL
11 PM EDT SUN AUG 19 2001
 
CHANTAL REMAINS VERY POORLY ORGANIZED THIS EVENING...WITH ITS 
LOW-LEVEL CENTER ABOUT 100 NM TO THE WEST OF THE CLOSEST DEEP 
CONVECTION.  FOR A TIME IT LOOKED AS THOUGH A CENTER MIGHT HAVE BEEN 
FORMING ON THE SOUTHWEST EDGE OF THE CONVECTION...BUT AN AIR FORCE 
RECONNAISSANCE AIRCRAFT FLEW THROUGH THIS LOCATION AT 700 MB AND 
COULD NOT DETECT ANY PRESENCE OF A CIRCULATION THERE.  THEY DID 
REPORT FLIGHT-LEVEL WINDS OF 69 KT...WHICH USING TYPICAL SURFACE 
REDUCTION FACTORS WOULD GIVE 60 KT AT THE SURFACE.  HOWEVER...A 
DROPSONDE RELEASED IN THE STRONGEST FLIGHT-LEVEL WINDS REPORTED 
SURFACE WINDS OF ONLY 38 KT.  AS EVIDENCED BY THIS OB AND A LONG 
HISTORY OF ILL-DEFINED SURFACE CENTERS...CHANTAL IS NOT EFFECTIVELY 
TRANSPORTING MOMENTUM TO THE SURFACE.  THE INITIAL INTENSITY IS 
LOWERED A BIT FOR THIS PACKAGE.  WITH THE CENTER SO REMOVED FROM THE 
CONVECTION...IT IS DIFFICULT TO ENVISION CHANTAL STRENGTHENING 
SIGNIFICANTLY BEFORE LANDFALL.  THIS THINKING IS SUPPORTED BY THE 
00Z RAOB FROM MERIDA...WHOSE 200 MB WIND SUGGESTS THAT SOUTHWESTERLY 
SHEAR IS NOT ABATING AS QUICKLY AS FORECAST BY THE AVN.

THE RECON FIXES CONTINUE THE EARLIER TREND OF BEING TO THE SOUTH OF 
THE VISIBLE LOW-LEVEL CLOUD SWIRL...SUCH THAT THE WIND CENTER LIES 
TO THE SOUTH OF THE LOW-LEVEL VORTICITY CENTER.  IT IS THE VORTICITY 
CENTER THAT WE ARE TRACKING AND THE INITIAL MOTION IS 290/16.  THERE 
IS NOT MUCH CHANGE IN THE SYNOPTIC REASONING.  GLOBAL MODELS 
ESTABLISH A MID-LEVEL RIDGE IN THE NORTHERN GULF THAT SHOULD KEEP 
CHANTAL...IF IT SURVIVES...ON A BASIC WEST-NORTHWESTERLY TRACK. 
SHOULD CHANTAL RECOVER IN THE SOUTHERN GULF...A SLOWING OF THE 
FORWARD SPEED IS EXPECTED.
 
FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     20/0300Z 17.1N  83.5W    55 KTS
12HR VT     20/1200Z 17.8N  85.8W    55 KTS
24HR VT     21/0000Z 18.8N  87.8W    60 KTS...INLAND
36HR VT     21/1200Z 19.8N  89.7W    50 KTS...INLAND
48HR VT     22/0000Z 21.0N  91.5W    55 KTS
72HR VT     23/0000Z 22.0N  94.0W    65 KTS
 
 
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