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TROPICAL STORM BARBARA DISCUSSION NUMBER   5
NATIONAL WEATHER SERVICE MIAMI FL
8 PM PDT WED JUN 20 2001
 
TROPICAL STORM BARBARA HAS CONTINUED TO BECOME BETTER ORGANIZED 
DURING THE PAST 6 HOURS AND DVORAK INTENSITY ESTIMATES ARE 45 KT 
FROM TAFB AND 35 KT FROM BOTH KGWC AND SAB.  AN EARLIER SSMI 
OVERPASS SHOWED SOME UNCONTAMINATED WIND SPEEDS TO NEAR 40 KT...SO 
THE INTENSITY WAS INCREASED IN THIS ADVISORY PACKAGE.  OUTFLOW 
REMAINS IMPRESSIVE...ESPECIALLY IN THE POLEWARD CHANNEL.

INITIAL MOTION ESTIMATE IS 290/13 OVER THE PAST 12 HOURS.  BARBARA
APPEARS TO HAVE MADE A POLEWARD STAIR-STEP IN THE TRACK DURING THE
PAST 12 HOURS...POSSIBLY DUE TO RE-ORGANIZATION OF THE SYSTEM
CENTER.  EARLIER TRMM AND SSMI OVERPASSES SUGGEST A SHORT TERM
MOTION OF 280/13...BUT I AM NOT READY TO BUY OFF ON THAT TREND QUITE
YET.  THERE IS NOW EXCELLENT AGREEMENT AMONG THE FORECAST GUIDANCE
ON A GENERAL WEST-NORTHWEST TRACK THROUGH 72 HOURS.  THE ONLY MAJOR
OUTLIER IS LBAR WHICH TAKES BARBARA NORTH-NORTHWESTWARD AFTER 60
HOURS.  THE UPPER-LEVEL LOW TO THE NORTHEAST OF HAWAII IS MOVING
WESTWARD IN TANDEM WITH BARBARA AND IS FORECAST TO CONTINUE TRACKING
WESTWARD AND WEAKEN THROUGH THE PERIOD.  THEREFORE...THE LOW SHOULD
HAVE LITTLE EFFECT...IF ANY...ON THE TRACK AND ONLY ACT TO ENHANCE
THE OUTFLOW TO THE NORTH.  THE MAIN STEERING MECHANISM SHOULD BE THE 
LOW- TO MID-LEVEL SUBTROPICAL RIDGE TO THE NORTH.  THE OFFICIAL 
FORECAST IS A LITTLE SOUTH OF THE AVN AND NOGAPS MODELS AND WELL 
NORTH OF THE UKMET...WHICH HAS BEEN STRUGGLING WITH THIS CYCLONE 
BEFORE IT EVER DEVELOPED.

SATELLITE IMAGERY INDICATES THAT CONVECTIVE BANDING FEATURES HAVE
IMPROVED MARKEDLY DURING THE PAST 12 HOURS AND THE OVERALL
CIRCULATION APPEARS TO HAVE TIGHTENED UP.  THE EARLIER BAND OF DEEP
CONVECTION WELL TO THE SOUTH OF THE CENTER HAS DISSIPATED...WHICH
SHOULD ALLOW FOR MORE SOUTHERLY INFLOW TO REACH THE INNER CORE.
THIS MAY ALREADY BE HAPPENING BASED ON THE NOTED INCREASE IN DEEP
CONVECTION NEAR THE CENTER DURING THE PAST 2 HOURS.  EVEN THOUGH
BARBARA IS CURRENTLY MOVING OVER SUB-26C SST WATER...THE WARM MOIST
SOUTHERLY INFLOW MAY HELP TO OFFSET ANY WEAKENING FOR ANOTHER 12 TO
24 HOURS.  IT IS STILL POSSIBLE FOR BARBARA TO BECOME A STRONG
TROPICAL STORM AND REACH NEAR-HURRICANE INTENSITY DURING THE NEXT 24
HOURS...ESPECIALLY IF THE CYCLONE TRACKS FURTHER SOUTH THAN THE
OFFICIAL FORECAST IS INDICATING.

NOTE...HISTORICAL RECORDS NOW SHOW THAT TROPICAL STORM BARBARA IS 
THE EARLIEST NAMED STORM THIS FAR WEST IN THE NORTHEAST PACIFIC.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     21/0300Z 14.0N 132.1W    40 KTS
12HR VT     21/1200Z 14.7N 134.0W    45 KTS
24HR VT     22/0000Z 15.8N 136.5W    50 KTS
36HR VT     22/1200Z 16.8N 138.9W    45 KTS
48HR VT     23/0000Z 17.8N 141.5W    40 KTS
72HR VT     24/0000Z 19.5N 146.0W    30 KTS
 
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