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TROPICAL STORM DOUGLAS DISCUSSION NUMBER   4
NATIONAL WEATHER SERVICE MIAMI FL
2 AM PDT SUN JUL 21 2002
 
THERE HAVE BEEN SEVERAL MICROWAVE IMAGES SUGGESTING THAT THE CENTER
OF THE TROPICAL STORM IS LOCATED TO THE NORTHEAST OF THE PREVIOUS
TRACK.  HOWEVER...TO MAINTAIN CONTINUITY AND OUT OF RESPECT FOR
CENTER FIXES FROM TAFB AND SAB...THE TRACK ADJUSTMENT IS NOT AS
DRASTIC AS THE MICROWAVE DATA WOULD SUGGEST.  INITIAL MOTION
ESTIMATE IS 325/8...ALTHOUGH OVER THE PAST SEVERAL HOURS IT MAY HAVE
BEEN MORE TOWARD THE NORTH-NORTHWEST.  AS NOTED EARLIER...DOUGLAS
HAS APPARENTLY BEEN INTERACTING WITH A DISTURBANCE WHICH WAS
ROTATING AROUND THE NORTHERN PART OF THE STORM CIRCULATION.  THIS
DISTURBANCE IS BECOMING INDISTINCT AS IT GETS ABSORBED INTO THE
CIRCULATION OF DOUGLAS.  LATER TODAY...THE HEADING IS EXPECTED TO
BEND BACK TO THE LEFT AS DOUGLAS BECOMES STEERED MORE BY THE
BROADER-SCALE FLOW.  A MID-TROPOSPHERIC RIDGE IS EXPECTED TO BECOME
BETTER ESTABLISHED TO THE NORTH OF THE CYCLONE...SO A MODEST
INCREASE IN FORWARD SPEED IS FORECAST OVER THE NEXT FEW DAYS.
OVERALL THE OFFICIAL TRACK FORECAST IS JUST SLIGHTLY NORTH OF THAT
FROM THE PREVIOUS ADVISORY...AND NEAR THE SOUTHERN EDGE OF THE 
GUIDANCE SUITE.  THE NCEP GLOBAL MODEL...GFS...IS SLIGHTLY FARTHER 
SOUTH AND FASTER.

THE SYSTEM CONTINUES TO BECOME BETTER ORGANIZED.  THERE IS A GOOD 
BANDING FEATURE IN THE INFRARED IMAGERY AND A PARTIAL EYEWALL-LIKE 
FEATURE IN THE MICROWAVE IMAGERY.  UPPER-LEVEL OUTFLOW CONTINUES TO 
BE RESTRICTED TO THE NORTHEAST BUT IS IMPRESSIVE IN THE OTHER 
QUADRANTS.  DATA T NUMBERS ARE NEAR 3.5...HOWEVER FINAL T-NUMBERS 
FROM SAB AND TAFB REMAIN AT 3.0.  CURRENT INTENSITY IS SET AT 50 KT. 
AS DISCUSSED PREVIOUSLY...THE GFDL MODEL IS VERY AGGRESSIVE ON 
INTENSIFICATION AND BRINGS THE CYCLONE OVER 100 KT WITHIN 36 HOURS.  
THE SHIPS GUIDANCE ALSO SHOWS STRENGTHENING...BUT ONLY TO ABOUT 75 
KT.  THE OFFICIAL FORECAST IS SIMILAR TO SHIPS BUT STRENGTHENS 
DOUGLAS A LITTLE MORE QUICKLY BASED ON THE CURRENT ORGANIZING TREND. 
DOUGLAS IS LIKELY TO BE ENCOUNTERING COOLER SSTS...AND THEREFORE BE 
ON A WEAKENING TREND...BY THE END OF THE FORECAST PERIOD.
 
FORECASTER PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     21/0900Z 15.4N 107.8W    50 KTS
12HR VT     21/1800Z 16.0N 108.7W    60 KTS
24HR VT     22/0600Z 16.5N 110.3W    65 KTS
36HR VT     22/1800Z 17.0N 112.0W    75 KTS
48HR VT     23/0600Z 17.5N 114.0W    75 KTS
72HR VT     24/0600Z 18.0N 118.0W    60 KTS
 
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