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HURRICANE DEBBY DISCUSSION NUMBER  15
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT WED AUG 23 2000
 
DEBBY HAS AGAIN SHOWN LITTLE CHANGE IN STRENGTH OVER THE PAST 6 HR.
AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT FOUND A MINIMUM
PRESSURE OF 995 MB AND 74 KT FLIGHT LEVEL WINDS NORTHEAST OF THE
CENTER.  ON THIS BASIS...THE INITIAL INTENSITY REMAINS 65 KT. 
WSR-88D DATA FROM SAN JUAN INDICATE A SERIES OF EYEWALL MESOVORTICES
HAVE FORMED AND THEN DISSIPATED DURING THE NIGHT...AS THE EYEWALL
CONVECTION HAS HAD TROUBLE WRAPPING MORE THAN HALFWAY AROUND THE
CENTER.  ONE NOTABLE ASPECT IS THAT A DROPSONDE IN THE EYE INDICATES
THE SURFACE CENTER MAY BE WEST OF THE 700 MB CENTER.

THE INITIAL MOTION IS 285/14.  A TWO-AIRCRAFT SYNOPTIC FLOW MISSION
TONIGHT RELEASED NUMEROUS DROPSONDES OVER THE CARIBBEAN AND WESTERN
ATLANTIC.  THESE SHOWED THAT DEBBY IS SOUTH OF A DEEP LAYER RIDGE...
AND IS ALREADY PASSING WEST OF THE WEAKNESS CAUSED BY A SHORTWAVE
TROUGH SEEN IN WATER VAPOR IMAGERY NEAR BERMUDA.  THE RIDGE SHOULD
KEEP DEBBY ON A GENERAL WEST-NORTHWEST TRACK THROUGH 48 HR.  THE
DROPSONDES HAVE CAUSED INTERESTING CHANGES IN THE MODELS.  ALL
LARGE-SCALE MODELS NOW CALL FOR A MORE WESTERLY MOTION ALONG THE
NORTH COASTS OF HISPANIOLA AND CUBA INTO THE GULF OF MEXICO.  THIS
INCLUDES THE UKMET...WHICH 12 HR AGO WAS MOVING DEBBY NORTHWARD EAST
OF FLORIDA.  IT DOES APPEAR THAT THE EASTERN U.S. TROUGH WILL
AMPLIFY SOUTHWARD BY 48 TO 72 HR.  THE QUESTION IS WILL DEBBY BE
CLOSE ENOUGH TO RESPOND TO IT?  THREE MODELS THAT SAY YES ARE LBAR
AND VICBAR...WHICH KEEP DEBBY EAST OF FLORIDA...AND THE GFDL...WHICH
TAKES IT TO NEAR THE FLORIDA KEYS.  IN VIEW OF THE SIZE OF THE
CHANGES...THERE WILL BE ONLY A SLIGHT SOUTHWARD ADJUSTMENT OF THE
FORECAST TRACK AT THIS TIME.  A MORE SUBSTANTIAL ADJUSTMENT CAN WAIT
UNTIL THERE IS MORE EVIDENCE OF WESTWARD MOTION AND MORE CONSISTENCY
IN THE MODEL RUNS.

THE DROPSONDE DATA INDICATES 10-20 KT SOUTHERLY FLOW AT 200-300 MB
UNDERCUTTING THE OUTFLOW OF DEBBY.  THIS HAS HELPED INHIBIT
INTENSIFICATION.  A COMBINATION OF SHEAR AND PROXIMITY TO HISPANIOLA
SHOULD PREVENT SIGNIFICANT STRENGTHENING FOR THE 24 HR OR SO.  AFTER
THAT...THE SHEAR MAY DECREASE AND ALLOW INTENSIFICATION.  THE SHIPS
MODEL...WHICH HAS PERFORMED WELL SO FAR...NOW TAKES DEBBY TO 81 KT
BY 72 HR.  AN EXTREME OUTLIER IS THE GFDL...WHICH HAS A 926 MB
PRESSURE AS DEBBY REACHES THE FLORIDA KEYS.  THIS LOOKS SUSPECT...AS
IT IS ALREADY STRONGER THAN REALITY AND A LOT OF DEEPENING OCCURS AS
THE MODEL STORM MOVES ALONG THE COASTS OF HISPANIOLA AND CUBA. 
NEVERTHELESS...DEBBY COULD BE A DANGEROUS MAJOR HURRICANE AS IT
APPROACHES SOUTH FLORIDA.
 
FORECASTER BEVEN
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     23/0900Z 19.7N  68.7W    65 KTS
12HR VT     23/1800Z 20.3N  70.7W    65 KTS
24HR VT     24/0600Z 21.0N  72.9W    65 KTS
36HR VT     24/1800Z 22.0N  75.1W    75 KTS
48HR VT     25/0600Z 23.0N  77.0W    80 KTS
72HR VT     26/0600Z 25.5N  80.0W    90 KTS
 
 
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