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TROPICAL STORM DARBY DISCUSSION NUMBER   3
NATIONAL WEATHER SERVICE MIAMI FL
2 PM PDT THU JUL 23 1998
 
THE SATELLITE SIGNATURE OF THE SYSTEM REMAINS FAIRLY IMPRESSIVE
WITH BANDING FEATURES WRAPPING FURTHER AROUND THE LOW-LEVEL
CENTER...HOWEVER DEEP CONVECTION HAS NOT INCREASED SIGNIFICANTLY.
DVORAK CLASSIFICATIONS FROM BOTH TAFB AND SAB ARE UP SLIGHTLY TO
2.5...35 KNOTS.  THEREFORE...THE SYSTEM IS BEING UPGRADED TO
TROPICAL STORM DARBY.  WITH WELL-ESTABLISHED OUTFLOW OVER THE
WESTERN SEMICIRCLE...AND IMPROVING ELSEWHERE...AND A LOW VERTICAL
SHEAR ENVIRONMENT...GRADUAL STRENGTHENING IS FORECAST.  DARBY IS
EXPECTED TO REACH HURRICANE STATUS BY 36 HOURS.  NO SIGNIFICANT 
STRENGTHENING IS ANTICIPATED BEYOND 36 HOURS AS THE SYSTEM
APPROACHES MARGINALLY COOLER WATERS.
 
THE SYSTEM HAS CONTINUED ON A WEST-NORTHWEST HEADING THIS AFTERNOON
AT A SLIGHTLY FASTER PACE WITH THE INITIAL MOTION ESTIMATE NOW
285/11 KNOTS.  THE MID- TO UPPER-LEVEL TROPOSPHERIC RIDGE DENOTED
IN WATER VAPOR IMAGERY CONTINUES TO SUGGEST THAT A GENERAL WEST TO
WEST-NORTHWESTERLY STEERING ENVIRONMENT SHOULD PERSIST THROUGH MOST
OF THE PERIOD.  THE OFFICIAL TRACK FORECAST IS A TAD TO THE LEFT OF
THE PREVIOUS ADVISORY...AND IS A COMPROMISE BETWEEN CLIPER...GFDL...
AND THE UKMET.
 
GUINEY/PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     23/2100Z 13.3N 114.4W    40 KTS
12HR VT     24/0600Z 13.7N 116.1W    45 KTS
24HR VT     24/1800Z 14.0N 118.3W    55 KTS
36HR VT     25/0600Z 14.3N 120.3W    65 KTS
48HR VT     25/1800Z 14.5N 122.5W    70 KTS
72HR VT     26/1800Z 15.0N 126.5W    70 KTS
 
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