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HURRICANE DARBY DISCUSSION NUMBER  16
NATIONAL WEATHER SERVICE MIAMI FL
8 PM PDT SUN JUL 26 1998

DARBY IS ANOTHER EXAMPLE THAT CLEARLY SHOWS THAT SKILLS IN
PREDICTING INTENSITY CHANGES ARE LOW.  THIS IS DIFFICULT PROBLEM
THAT BOTH OPERATIONAL AND RESEARCH COMMUNITIES ARE TRYING TO
OVERCOME.  HURRICANE SPECIALISTS AND EVERY AVAILABLE MODEL...RANGING
FROM THE SIMPLE SHIFOR TO THE HIGHLY SOPHISTICATED STATE OF THE ART
GFDL...FORECAST WEAKENING.
 
DARBY DID NOT WEAKEN AS FORECAST AND IN FACT...IT COULD BE A LITTLE
BIT STRONGER TODAY IF THE NEW OBJECTIVE T-NUMBERS ARE CONSIDERED.
THESE NUMBERS ARE PEAKING AROUND A 6.0 ON THE DVORAK SCALE.
HOWEVER...MORE RELIABLE SUBJECTIVE T-NUMBERS FROM SAB AND TAFB
REMAIN ABOUT 5.5 GIVING AN INTENSITY OF ABOUT 100 KNOTS.  THE
HURRICANE HAS A DISTINCT AND LARGE EYE EMBEDDED WITHIN A WELL
DEFINED CDO BUT WITHOUT BANDING FEATURES.  DARBY IS MOVING PARALLEL
TO THE 25 DEGREE SST ISOTHERM SO ONLY A SLOW WEAKENING IS INDICATED
AND AS SUGGESTED IN THE PREVIOUS ADVISORY.    

DARBY IS MOVING AROUND THE PERIPHERY OF A STRONG DEEP LAYER MEAN
ANTICYCLONE WHICH IS FORECAST TO PERSIST.  THEREFORE...NO
SIGNIFICANT CHANGE IN TRACK IS FORECAST DURING THE NEXT 24 TO 36
HOURS.  THEREAFTER...AN INCREASE IN FORWARD SPEED AND A SMALL TURN
TO THE WEST-NORTHWEST IS EXPECTED AS SUGGESTED BY MOST OF THE
GUIDANCE.  ON THIS TRACK...IN ABOUT 48 TO 60 HOURS...DARBY WILL BE
CROSSING 140 DEGREES WEST...MOVING INTO THE HONOLULU AREA OF
RESPONSIBILITY. 

AVILA 

FORECAST POSITIONS AND MAX WINDS
 
INITIAL     27/0300Z 16.5N 128.2W   100 KTS
12HR VT     27/1200Z 16.5N 130.0W   100 KTS
24HR VT     28/0000Z 17.0N 132.5W    90 KTS
36HR VT     28/1200Z 17.5N 135.5W    80 KTS
48HR VT     29/0000Z 18.0N 138.0W    70 KTS
72HR VT     30/0000Z 20.0N 144.5W    50 KTS
 
 
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