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TROPICAL STORM DARBY DISCUSSION NUMBER   4
NATIONAL WEATHER SERVICE MIAMI FL
8 PM PDT THU JUL 23 1998

VISIBLE SATELLITE IMAGES INDICATE THAT DARBY HAS WELL DEFINED CLOUD
BANDS WRAPPING AROUND THE CENTER BUT IT LACKS CENTRAL FEATURES. IR
IMAGES SHOW THAT THE CONVECTIVE TOPS ARE NOT VERY COLD AT THIS TIME. 
T-NUMBERS ARE 3.0 AND 2.5 SO THE INITIAL INTENSITY IS SET AT 40
KNOTS. SHIFOR SHOWS ONLY A SLIGHT INCREASE IN INTENSITY WHILE THE
GFDL FORECASTS NO CHANGE AT ALL.  DARBY IS MOVING OVER WARM
WATERS...LOW LATITUDES...AND THERE IS NO WIND SHEAR AHEAD. 
THEREFORE...THE OFFICIAL FORECAST BRINGS THE SYSTEM TO HURRICANE
STATUS IN 36 HOURS...FOLLOWING SHIPS MODEL AND AS INDICATED IN THE
PREVIOUS FORECAST.

INITIAL MOTION IS 275/10.  A DEEP LAYER MEAN RIDGE TO THE NORTH OF
THE STORM IS FORECAST TO PERSIST SO A GENERAL WEST TO WEST-NORTHWEST
TRACK IS EXPECTED THROUGH 72 HOURS. THIS IS IN GENERAL AGREEMENT
WITH ALL TRACK MODELS EXCEPT BY THE HIGHLY UNLIKELY SOLUTION OF THE
AVN WHICH TURNS DARBY SOUTHWESTWARD. 

AVILA
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     24/0300Z 13.2N 114.9W    40 KTS
12HR VT     24/1200Z 13.2N 116.5W    45 KTS
24HR VT     25/0000Z 13.5N 118.5W    55 KTS
36HR VT     25/1200Z 14.0N 120.5W    65 KTS
48HR VT     26/0000Z 14.5N 122.5W    70 KTS
72HR VT     27/0000Z 14.5N 127.5W    70 KTS
 
 
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