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HURRICANE DARBY DISCUSSION NUMBER  21
NATIONAL WEATHER SERVICE MIAMI FL
2 AM PDT TUE JUL 28 1998

THE EYE IS BECOMING DIFFUSE AND OVERALL DARBY LOOKS WEAKER THAN IT
WAS 24 HOURS AGO.  CURRENT MAXIMUM WINDS ARE REDUCED TO 90 KNOTS. 
THE HURRICANE IS CURRENTLY CROSSING THE 25 DEG C SST ISOTHERM AND
FURTHER WEAKENING IS LIKELY.  THE RATE OF WEAKENING WILL LIKELY
INCREASE LATER IN THE FORECAST PERIOD DUE TO SOUTHWESTERLY VERTICAL
SHEAR.

THE DIRECTION OF MOTION HAS SHIFTED SLIGHTLY MORE TO THE WEST-
NORTHWEST BUT NO SIGNIFICANT CHANGE IS MADE TO THE TRACK FORECAST
FROM THE PREVIOUS ADVISORY.  DARBY SHOULD BE NEARING THE WESTERN
PERIPHERY OF A DEEP-LAYER MEAN RIDGE IN A FEW DAYS.  THE OFFICIAL
FORECAST TRACK IS QUITE CLOSE TO THE LATEST GFDL MODEL GUIDANCE.

PASCH 

FORECAST POSITIONS AND MAX WINDS
 
INITIAL     28/0900Z 17.5N 135.3W    90 KTS
12HR VT     28/1800Z 18.0N 137.5W    85 KTS
24HR VT     29/0600Z 18.7N 140.2W    80 KTS
36HR VT     29/1800Z 19.5N 143.0W    70 KTS
48HR VT     30/0600Z 20.5N 145.5W    60 KTS
72HR VT     31/0600Z 22.5N 150.5W    50 KTS
 
 
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