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HURRICANE DARBY DISCUSSION NUMBER  17
NATIONAL WEATHER SERVICE MIAMI FL
2 AM PDT MON JUL 27 1998

CONVECTIVE TOPS HAVE WARMED OVER THE PAST 12 HOURS OR SO...BUT DARBY
REMAINS VERY WELL-ORGANIZED WITH A WELL-DEFINED EYE ESTIMATED TO BE
ABOUT 25 N MI IN DIAMETER.  THUS FAR...DARBY HAS KEPT FAR ENOUGH TO
THE SOUTH SO AS TO AVOID THE STRONGER VERTICAL SHEAR NEAR 20N
LATITUDE.   THE HURRICANE APPARENTLY UNDERWENT AN EYEWALL
REPLACEMENT CYCLE OVER THE PAST 24 TO 36 HOURS...LEADING TO THE
SECOND PEAK IN INTENSITY.  IT IS NOT CERTAIN WHETHER THE SYSTEM WILL
GO THROUGH ANOTHER SUCH CYCLE OR NOT.  THIS LIKELY DEPENDS ON HOW
MUCH LONGER THE ATMOSPHERIC AND OCEANIC ENVIRONMENT REMAIN
FAVORABLE.  SINCE THE CURRENT TREND SUGGESTS SLOW WEAKENING...AND
EYEWALL CYCLES ARE NEARLY IMPOSSIBLE TO FORETELL...GRADUAL WEAKENING
IS PREDICTED AS IN THE PREVIOUS ADVISORY PACKAGE.

THERE ARE NO SIGNIFICANT CHANGES TO THE MOTION OR THE TRACK
FORECAST.  STEERING WILL LIKELY CONTINUE TO BE DOMINATED BY A DEEP-
LAYER MEAN RIDGE TO THE NORTH OF DARBY...ALONG ABOUT 27N LATITUDE. 
THE LATEST NCEP GLOBAL MODEL RUN SHOWS THIS RIDGE EXTENDING THROUGH
145W LONGITUDE THROUGH THE FORECAST PERIOD.

ON THE CURRENT OFFICIAL FORECAST TRACK...DARBY WILL BE NEARING THE
BORDER OF THE CENTRAL PACIFIC HURRICANE CENTERS AREA OF
RESPONSIBILITY...140W...IN ABOUT 48 HOURS.        

PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     27/0900Z 16.5N 129.5W   100 KTS
12HR VT     27/1800Z 16.7N 131.2W   100 KTS
24HR VT     28/0600Z 17.1N 133.7W    90 KTS
36HR VT     28/1800Z 17.5N 136.3W    80 KTS
48HR VT     29/0600Z 18.0N 139.0W    70 KTS
72HR VT     30/0600Z 19.5N 144.5W    50 KTS
 
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