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TROPICAL STORM DEBBY DISCUSSION NUMBER  17
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT WED AUG 23 2000
 
RECON AND SATELLITE IMAGES INDICATE THAT THE LOW- AND MID-LEVEL
CIRCULATIONS HAVE SEPARATED FROM THE UPPER-LEVEL CIRCULATION DURING
THE DAY. SOME CONVECTION HAS RE-DEVELOPED NEAR THE RAGGED LOW-LEVEL
CIRCULATION...BUT MOST OF THE SIGNIFICANT DEEP CONVECTION REMAINS
SHEARED WELL TO THE EAST WHERE THE BEST UPPER-LEVEL OUTFLOW IS
LOCATED. THE INITIAL INTENSITY WAS DECREASED BASED ON 50 KT RECON
WINDS AT 1000 FT.
 
THE INITIAL MOTION ESTIMATE IS 275/16.  THE MAIN QUESTION IS WHICH
SIDE OF EASTERN CUBA WILL DEBBY TAKE ONCE THE LOW-LEVEL CENTER
EMERGES OFF THE NORTHWEST COAST OF HAITI LATER TONIGHT.  OUR FEELING
IS THAT INCREASING SOUTHERLY FLOW THROUGH THE WINDWARD PASSAGE MAY
HELP TO NUDGE THE CENTER NORTH OF 20N LATITUDE AND KEEP IT ON THE
NORTH COAST OF CUBA. HOWEVER...IT IS POSSIBLE THAT THE LOW-LEVEL
CENTER COULD SNEAK THROUGH THE PASSAGE AND EMERGE ON THE SOUTH SIDE
OF CUBA.  ASSUMING DEBBY STAYS ON THE NORTH SIDE OF THE HIGHER
TERRAIN...THE TRACK KEEPS DEBBY JUST INLAND ALONG THE NORTH COAST OF
CUBA THROUGH 36 HOURS...WHICH IS CLOSE TO GFDL...AND THE MEDIUM AND
DEEP BAM MODELS.  THE NEW 12Z UKMET MODEL HAS SHIFTED ITS TRACK
FURTHER NORTH OF THE PREVIOUS 00Z TRACK.  UNTIL SOME CONSISTENCY IN
THE GLOBAL AND REGIONAL MODELS OCCURS...WE DO NOT WANT TO SHIFT THE
TRACK TOO FAR TO THE WEST AND TAKE SOUTH FLORIDA AND THE KEYS OFF
THE HOOK. THE REASON IS THAT ALL THE MODELS AGREE ON DEVELOPING A
STRONG WEAKNESS IN THE SUBTROPICAL RIDGE ACROSS FLORIDA AND THE
SOUTHEAST AFTER 48 HOURS. NOTE...THE G-IV AIRCRAFT WILL BE MAKING A
SYNOPTIC FLIGHT AROUND DEBBY TONIGHT...AND THAT DROPSONDE DATA
SHOULD MAKE IT INTO THE 00Z MODEL RUNS.

THE INTENSITY FORECAST IS HIGHLY DEPENDENT ON THE TRACK FORECAST. IF
DEBBY STAYS OVER LAND AS FORECAST...THEN WEAKENING SHOULD CONTINUE.
HOWEVER...IF MORE OF THE LOW-LEVEL CIRCULATION STAYS OVER WATER...
SOME SLOW STRENGTHENING COULD STILL OCCUR BEYOND 48 HOURS.  THE
UPPER-LEVEL FLOW WILL ALSO BE MORE FAVORABLE FOR DEVELOPMENT THEN
DUE TO DECREASING VERTICAL SHEAR...AS INDICATED BY ALL THE MODELS.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     23/2100Z 20.0N  72.3W    45 KTS
12HR VT     24/0600Z 20.5N  74.9W    40 KTS
24HR VT     24/1800Z 21.4N  77.6W    35 KTS
36HR VT     25/0600Z 22.6N  79.5W    35 KTS
48HR VT     25/1800Z 24.0N  81.0W    40 KTS
72HR VT     26/1800Z 26.5N  82.5W    55 KTS
  
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