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HURRICANE DARBY DISCUSSION NUMBER  18
NATIONAL WEATHER SERVICE MIAMI FL
8 AM PDT MON JUL 27 1998
 
DARBY HAS CHANGED LITTLE IN INTENSITY THE LAST 6 HOURS OR SO WITH
OBJECTIVE T-NUMBERS AVERAGING BETWEEN 5.5 AND 5.7.  SATELLITE
IMAGERY SHOWS A VERY SYMMETRIC HURRICANE WITH A WELL-DEFINED EYE
FEATURE...ABOUT 25 N MI IN DIAMETER.  DVORAK CLASSIFICATIONS FROM
BOTH TAFB AND SAB ARE 5.5...AND THE INITIAL INTENSITY IS HELD AT
100 KNOTS FOR THIS ADVISORY.  THE INTENSITY FORECAST IS VERY SIMILAR
TO THE PREVIOUS FORECAST WITH DARBY EXPECTED TO GRADUALLY WEAKEN AS
IT ENCOUNTERS COOLER WATERS.
 
THE INITIAL MOTION IS 275/12 KNOTS.  THE DEEP-LAYER MEAN RIDGE NORTH
OF DARBY IS EXPECTED TO CONTINUE STEERING THE SYSTEM ON A GENERAL
WESTWARD COURSE THROUGH 36 HOURS. THEREAFTER...A MORE WEST-NORTHWEST
HEADING IS ANTICIPATED AS DARBY APPROACHES THE WESTERN PERIPHERY
OF THE RIDGE.  THE OFFICIAL FORECAST TRACK IS VERY SIMILAR TO THE
PREVIOUS PACKAGE WHICH BRINGS DARBY INTO THE CENTRAL PACIFIC
HURRICANE CENTERS AREA OF RESPONSIBILITY...140W...IN ABOUT 48 HOURS.
 
GUINEY/LAWRENCE
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     27/1500Z 16.8N 130.9W   100 KTS
12HR VT     28/0000Z 16.9N 132.9W   100 KTS
24HR VT     28/1200Z 17.3N 135.3W    90 KTS
36HR VT     29/0000Z 17.8N 138.0W    80 KTS
48HR VT     29/1200Z 18.5N 141.0W    65 KTS
72HR VT     30/1200Z 20.0N 146.5W    50 KTS
 
 
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