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HURRICANE DARBY DISCUSSION NUMBER  23
NATIONAL WEATHER SERVICE MIAMI FL
2 PM PDT TUE JUL 28 1998
 
VISIBLE SATELLITE IMAGES THIS AFTERNOON SHOW THAT THE STRATOCUMULUS
CLOUD FIELD WEST OF DARBY IS BECOMING INVOLVED WITH THE WESTERN
FLANK OF THE SYSTEM.  THIS IS CONSISTENT WITH THE DECREASE IN THE
AREAL COVERAGE OF DEEP CONVECTION.  THE CURRENT INTENSITY IS LOWERED
TO 75 KNOTS...IN LINE WITH CURRENT INTENSITY ESTIMATES FROM TAFB...
SAB AND KGWC.  THE WEAKENING TREND OF THE PREVIOUS ADVISORY WILL 
BE ACCELERATED SOMEWHAT BRINGING THE SYSTEM TO TROPICAL STORM STATUS
WITHIN 12 HOURS.  THEREAFTER...THE SYSTEM SHOULD CONTINUE TO UNWIND
AS IT MOVES INTO INCREASING SOUTH/SOUTHWESTERLY VERTICAL SHEAR AND
PROGRESSIVELY COOLER WATERS. 
 
SATELLITE FIXES DURING THE DAY SUGGEST THAT DARBY IS MOVING ON A
SLIGHTLY MORE WESTERLY TRACK...AND THE INITIAL MOTION ESTIMATE
IS ADJUSTED TO 280/14 KNOTS.  THE SYSTEM IS NEARING THE WESTERN
PERIPHERY OF THE DEEP-LAYER MEAN RIDGE WITH A MORE NORTHERLY
COMPONENT OF MOTION EXPECTED BY 24 HOURS.  THE OFFICIAL FORECAST
TRACK CALLS FOR A GENERAL WEST-NORTHWEST MOTION BEYOND 24 HOURS
AND IS IN CLOSEST AGREEMENT WITH BAM SHALLOW...THE GFDL...AND THE
AVIATION TRACK GUIDANCE.

THE CURRENT FORECAST BRINGS DARBY TO 140W...DENOTING THE CENTRAL
PACIFIC HURRICANE CENTER AREA OF RESPONSIBILITY....LATER TODAY.

GUINEY/LAWRENCE

FORECAST POSITIONS AND MAX WINDS

INITIAL     28/2100Z 18.1N 138.2W    75 KTS
12HR VT     29/0600Z 18.6N 140.4W    60 KTS
24HR VT     29/1800Z 19.4N 143.4W    50 KTS
36HR VT     30/0600Z 20.5N 146.1W    35 KTS
48HR VT     30/1800Z 22.0N 149.0W    30 KTS
72HR VT     31/1800Z 24.5N 153.5W    25 KTS

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