HOME	PRODUCTS	FORECASTS	IMAGERY	ABOUT TPC	RECONNAISSANCE

ZCZC MIATCDAT2 ALL
TTAA00 KNHC DDHHMM
TROPICAL STORM DEBBY DISCUSSION NUMBER  16
NATIONAL WEATHER SERVICE MIAMI FL
11 AM EDT WED AUG 23 2000
 
AIR FORCE RECON FOUND A TIGHT MID-LEVEL CIRCULATION THIS MORNING
WITH MOST OF THE CONVECTION DISPLACED TO THE NORTHEAST. THE LOW-
LEVEL CIRCULATION HAS LIKELY BEEN DISRUPTED BY THE DOWNSLOPE FLOW
OFF THE MOUNTAINS OF HISPANIOLA. UPPER-LEVEL OUTFLOW REMAINS
IMPRESSIVE IN THE NORTH SEMICIRCLE...BUT IS RESTRICTED ELSEWHERE DUE
TO SOUTHERLY SHEAR. THE INITIAL INTENSITY WAS DECREASED TO 60 KT
BASED ON SEVERAL RECON DROPSONDES INDICATING 55 TO 60 KT WIND NORTH
OF THE CENTER IN THE WEAKENING CONVECTION AROUND 12Z.
 
THE INITIAL MOTION ESTIMATE IS 280/14.  CENTER LOCATIONS FROM RECON
INDICATE CONSIDERABLE FLUCTUATION IN THE FORWARD SPEED RANGING FROM
19 KT DOWN TO 12 KT.  AS A RESULT...THE INITIAL MOTION ESTIMATE IS
BASED ON CONTINUITY AND PERSISTENCE.  AFTER THE UKMET MODEL MADE A
HUGE CHANGE IN THE TRACK OF DEBBY BETWEEN THE 22/12Z AND 23/00Z
RUNS...I HAVE LITTLE CONFIDENCE IN THE SPECIFICS OF ITS FORECAST
TRACK.  THE UKMET INTENSITY FORECAST CALLS FOR A WEAK SYSTEM...WHICH
SUGGESTS THAT THE MODEL IS BASING THE STEERING MAINLY ON THE LOW-
LEVEL FLOW.  THE NOGAPS MODEL SEEMS TO BE KEYING ON THE SAME TYPE OF
STEERING REGIME.  HOWEVER...THE AVN AND MRF MODELS HAVE BEEN VERY
CONSISTENT WITH A TRACK NEAR THE NORTH COAST OF HISPANIOLA AND
CUBA...AND HAS GRADUALLY BEEN SHIFTING THE TRACK NORTHWARD.  THOSE
MODELS ALSO MADE THE LEAST AMOUNT OF TRACK CHANGE AS COMPARED TO THE
OTHER 23/00Z GLOBAL MODELS.  AS A RESULT...WE HAVE STAYED CLOSE TO
THE GFDL MODEL WHICH TAKES DEBBY CLOSE TO THE SOUTHERN TIP OF
FLORIDA IN 72 HOURS.  ALSO...THE NEW FORECAST MODEL GUIDANCE IS LESS
DIVERGENT THAN PREVIOUS RUNS...AND NOW CONVERGE MORE ON A TRACK
TOWARD SOUTH FLORIDA OR THE FLORIDA KEYS...EXCLUDING THE UKMET AND
NOGAPS WHICH KEEP DEBBY MAINLY TO THE SOUTH OF CUBA.

THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS INTENSITY FORECAST
REASONING.  LAND INTERACTION SHOULD HINDER ANY SIGNIFICANT
DEVELOPMENT FOR AT LEAST THE NEXT 24 HOURS.  AS DEBBY MOVES NORTH OF
THE WINDWARD PASSAGE...INCREASED SOUTHERLY INFLOW MAY ALLOW FOR SOME
WEAK INTENSIFICATION BEFORE THE FLOW COMES OFF OF CUBA AGAIN.  BY 48
HOURS...DEBBY IS FORECAST TO BE FREE OF ANY ADVERSE LAND EFFECTS AND
ALSO BE OVER 29C TO 30C WATER.  ALL THE GLOBAL AND REGIONAL MODELS
AGREE THAT A 200 MB LOW WILL CLOSE OFF NEAR THE YUCATAN...WHICH
WOULD SHIFT THE SHEAR VECTOR AROUND FROM THE SOUTH-SOUTHWEST TO THE
SOUTHEAST...WHICH WOULD BE ALONG AND WITH THE STORM MOTION RATHER
THAN ACROSS IT.  THE SHIPS INTENSITY MODEL ALSO INDICATES DECREASING
SHEAR AFTER 48 HOURS...AND THE INTENSITY COULD BE HIGHER THAN WE ARE
INDICATING IF DEBBY EVER MAINTAINS A GOOD CLOSED EYE/LOW-LEVEL
CIRCULATION.
 
FORECASTER STEWART
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     23/1500Z 19.9N  70.0W    60 KTS
12HR VT     24/0000Z 20.3N  72.6W    60 KTS
24HR VT     24/1200Z 21.2N  75.1W    65 KTS
36HR VT     25/0000Z 22.3N  76.9W    70 KTS
48HR VT     25/1200Z 23.5N  78.5W    75 KTS
72HR VT     26/1200Z 25.5N  81.0W    85 KTS
 
 
NNNN