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TROPICAL STORM JOYCE DISCUSSION NUMBER 21
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT SAT SEP 30 2000
A BURST OF DEEP CONVECTION HAS OCCURRED NEAR THE CENTER...BUT THERE
IS LITTLE OR NO EVIDENCE OF BANDING FEATURES. OVERALL THE SYSTEM
REMAINS VERY DISORGANIZED AND THE MAXIMUM WIND ESTIMATE IS KEPT AT
MARGINAL STORM STRENGTH. HOWEVER IT SHOULD BE NOTED THAT WE HAVE
SEEN A NUMBER OF CASES OF RELATIVELY INSIGNIFICANT-LOOKING SYSTEMS
IN WHICH RATHER STRONG WINDS WERE FOUND. AN AIR FORCE HURRICANE
HUNTER PLANE WILL INVESTIGATE JOYCE LATE TONIGHT TO GIVE A MORE
PRECISE MEASUREMENT OF INTENSITY. BOTH THE SHIPS MODEL AND ANALYSES
FROM THE UNIVERSITY OF WISCONSIN CIMSS SHOW WEAK SHEAR IN THE
VICINITY OF JOYCE. HOWEVER AS BEFORE...BECAUSE THE CURRENT STATE OF
THE SYSTEM IS NOT VERY HEALTHY...NOT MUCH INCREASE IN STRENGTH IS
PREDICTED UNTIL LATE IN THE FORECAST PERIOD.
AS NEW CONVECTION DEVELOPS NEAR THE CENTER...THERE IS MORE COUPLING
WITH THE MID- TO UPPER-LEVELS AND THIS MAY CAUSE SOME SLOWING OF THE
EFFECTIVE STEERING FLOW. SHORT-TERM MOTION HAS SLOWED FROM 16-18
KNOTS EARLIER TODAY TO ABOUT 14 KNOTS. THE TRACK FORECAST IS ABOUT
THE SAME AS BEFORE BUT SLIGHTLY DELAYS THE TIMING OF JOYCES PASSAGE
OVER THE WINDWARDS. GLOBAL MODELS SHOW A MID-TROPOSPHERIC RIDGE
REMAINING NORTH OF JOYCE FOR THE NEXT FEW DAYS. THEREFORE A WEST-
TO WEST-NORTHWEST MOTION SHOULD CONTINUE...TAKING JOYCE INTO THE
CENTRAL CARIBBEAN AROUND THE END OF THE FORECAST PERIOD.
THIS OFFICIAL FORECAST IS IN GOOD AGREEMENT WITH THE LATEST NCEP
GLOBAL MODEL RUN. THE U.K. MET SHOWS A SIMILAR TRAJECTORY BUT A
SLIGHTLY FASTER FORWARD SPEED.
FORECASTER PASCH
FORECAST POSITIONS AND MAX WINDS
INITIAL 30/2100Z 10.5N 57.3W 35 KTS
12HR VT 01/0600Z 11.0N 59.5W 35 KTS
24HR VT 01/1800Z 11.8N 62.2W 35 KTS
36HR VT 02/0600Z 12.5N 65.0W 40 KTS
48HR VT 02/1800Z 13.5N 67.5W 50 KTS
72HR VT 03/1800Z 15.0N 72.0W 65 KTS
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