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TROPICAL STORM CHANTAL DISCUSSION NUMBER 19
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT MON AUG 20 2001
EARLIER RECON DATA INDICATED CHANTAL REMAINS POORLY ORGANIZED...WITH
MULTIPLE LOW-LEVEL CIRCULATIONS EMBEDDED WITHIN A BROAD AREA OF LOW
PRESSURE. HOWEVER...DURING THE OUTBOUND LEG...THE RECON AIRCRAFT
PASSED THROUGH A BETTER-DEFINED CIRCULATION NEAR 17.0N 83.9W AT
0523Z. THIS CIRCULATION ALSO HAD A 30 KT WIND MAX ASSOCIATED WITH
IT...AND SATELLITE IMAGERY INDICATES A LARGE THUNDERSTORM CLUSTER
HAS DEVELOPED OVER OR NEAR THAT CIRCULATION. BASED ON A COMBINATION
OF THE RECON WIND DATA AND THE CONVECTIVE TRENDS NOTED SATELLITE
IMAGERY...THE 06Z SYNOPTIC AND ADVISORY POSITIONS WERE KEPT A LITTLE
FARTHER NORTH THAN THE LAST RECON VORTEX LOCATION. THIS IS ALSO
MAINTAINS CONTINUITY WITH EXTRAPOLATED POSITIONS FROM THE PREVIOUS
ADVISORY MOTION. RECON ALSO FOUND A 61 KT 850 MB FLIGHT-LEVEL WIND
ON THE OUTBOUND LEG AT 0552Z...WHICH EQUATES TO ABOUT A 50 KT
SURFACE WIND. HOWEVER...THIS WIND REPORT WAS JUST NORTH OF THE
STRONGEST CONVECTION...SO THE INITIAL INTENSITY IS HELD AT 55 KT.
THE INITIAL MOTION ESTIMATE IS 290/13 BASED ON A BLEND OF RECON AND
SATELLITE POSITION ESTIMATES. CHANTAL IS EXPECTED TO MAINTAIN A
GENERAL WEST-NORTHWEST MOTION UNTIL LANDFALL IN ABOUT 18 TO 24 HOURS
ALONG THE YUCATAN PENINSULA. THE VAST MAJORITY OF THE MODEL
GUIDANCE REMAINS TIGHTLY CLUSTERED IN TAKING CHANTAL SLOWLY ACROSS
THE YUCATAN AND INTO THE SOUTHWEST GULF OF MEXICO IN 36 TO 48 HOURS
AND THEN TURNING THE CYCLONE MORE WESTWARD AFTERWARDS. THE OFFICAL
FORECAST TRACK IS VERY CLOSE TO THE PREVIOUS TRACK AND NEAR THE
UKMET AND AVN TRACK FORECASTS.
THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS INTENSITY FORECAST.
CHANTAL IS EXPECTED TO REMAIN IN A SHEARED STATE FOR THE NEXT 36
HOURS OR SO...AND LITTLE OR NO SIGNIFICANT STRENGTHENING IS
FORECAST. HOWEVER...IT IS POSSIBLE FOR CHANTAL TO REACH MINIMAL
HURRICANE INTENSITY JUST BEFORE MAKING LANDFALL OVER YUCATAN AS
INCREASING FRICTIONAL CONVERGENCE ON THE WEST SIDE MAY HELP TO
TIGHTEN UP THE LOW-LEVEL CIRCULATION.
FORECASTER STEWART
FORECAST POSITIONS AND MAX WINDS
INITIAL 20/0900Z 17.3N 84.8W 55 KTS
12HR VT 20/1800Z 18.1N 86.6W 60 KTS
24HR VT 21/0600Z 19.5N 88.5W 50 KTS...INLAND
36HR VT 21/1800Z 20.6N 90.3W 45 KTS...INLAND
48HR VT 22/0600Z 21.3N 92.0W 55 KTS
72HR VT 23/0600Z 22.0N 94.5W 70 KTS
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