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TROPICAL STORM DEBBY DISCUSSION NUMBER   5
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT SUN AUG 20 2000
 
THE CONVECTIVE BANDING OF TROPICAL STORM DEBBY HAS BECOME A LITTLE
BETTER ORGANIZED THIS AFTERNOON...WHILE THE CENTER POSITION IS STILL
SOMEWHAT UNCERTAIN.  A 1506Z TRMM OVERPASS SHOWED A TIGHT MID-LEVEL
CIRCULATION OR EYE-LIKE FEATURE IN THE 85GHZ ICE DATA...WHILE THE
37GHZ CHANNEL AND VISIBLE SATELLITE DATA SUGGEST THAT THE LOW-LEVEL
CIRCULATION IS LOCATED ABOUT 25 NM TO THE SOUTHWEST OF THE MID-
LEVEL CIRCULATION.  ALTHOUGH SATELLITE INTENSITY ESTIMATES OF 45 KT
ARE INDICATED BY TAFB AND SAB...I FELT IT BEST TO HOLD THE INTENSITY
DOWN SOME UNTIL THE LOW-LEVEL AND MID-LEVEL CIRCULATIONS BECOME
VERTICALLY STACKED. OUTFLOW REMAINS GOOD IN ALL QUADRANTS.

INITIAL MOTION IS 290/17.  DUE TO THE UNCERTAINTY OF THE LOCATION OF
THE SYSTEM CENTER...THERE MAY BE SOME LARGE WOBBLES ALONG THE TRACK.
THE OVERALL WIND AND CONVECTIVE ENVELOPE HAS BEEN TRACKING WESTWARD
TODAY...WHILE THE SYSTEM CENTER HAS BEEN REFORMING AND WOBBLING
AROUND INSIDE THE ENVELOPE.  DUE TO THE UNCERTAINTY IN THE EXACT
LOCATION OF THE CENTER...THE OFFICIAL FORECAST IS VERY NEAR THE
PREVIOUS FORECAST TRACK.  ALL OF THE GLOBAL AND REGIONAL MODELS
AGREE ON BUILDING THE SUBTROPICAL HIGH TO THE NORTH AND NORTHWEST OF
DEBBY THROUGH THE PERIOD...WHICH SHOULD ACT TO KEEP THE CYCLONE ON A
GENERAL WEST-NORTHWEST TRACK.  THIS SEEMS REASONABLE BASED ON 590 DM
HEIGHTS AND EAST WINDS IN THE 12Z RAOB DATA OVER THE NORTHEAST
CARIBBEAN ISLANDS.  ALSO...RECENT SYNOPTIC DROPSONDE DATA FROM THE
GULFSTREAM JET AIRCRAFT INDICATED A DEEP LAYER MEAN STEERING FLOW
FROM THE EAST AT 15 TO 20 KT NORTH OF DEBBY.  THIS NEW DATA WILL BE
INCORPORATED INTO THE 00Z MODEL RUNS...AND A TRACK CLOSER TO THE
NORTHERN LEEWARD ISLANDS WOULD NOT SURPRISE ME.  THE OFFICIAL TRACK
ON THE EXTREME SOUTHERN EDGE OF THE MODEL GUIDANCE ENVELOPE AND
CLOSE TO BUT A LITTLE SLOWER THAN THE GFDL AND UKMET MODELS.

DEBBY IS EXPECTED TO STEADILY INTENSIFY THROUGH 36 HOURS AND REACH
HURRICANE INTENSITY IN 36 TO 48 HOURS.  THEREAFTER...SOME SHEAR MAY
SLOW DOWN THE INTENSIFICATION RATE AS SUGGESTED BY THE SHIPS
INTENSITY MODEL.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     20/2100Z 15.2N  51.5W    45 KTS
12HR VT     21/0600Z 15.9N  53.8W    50 KTS
24HR VT     21/1800Z 16.9N  57.0W    60 KTS
36HR VT     22/0600Z 17.5N  60.5W    65 KTS
48HR VT     22/1800Z 18.0N  64.0W    70 KTS
72HR VT     23/1800Z 20.5N  70.5W    80 KTS
 
 
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