ZCZC MIATCDEP5 ALL TTAA00 KNHC DDHHMM HURRICANE DARBY DISCUSSION NUMBER 13 NATIONAL WEATHER SERVICE MIAMI FL 2 AM PDT SUN JUL 26 1998 DVORAK ESTIMATES INDICATE THAT...FOR THE TIME BEING...THE INTENSITY HAS LEVELLED OFF NEAR 90 KNOTS. A LARGE EYE HAS RE-APPEARED...AND DARBY HAS LIKELY BEEN UNDERGOING A CONCENTRIC EYEWALL PHASE AS SUGGESTED BY INFRARED AND MICROWAVE DATA. ANALYSES FROM THE UNIVERSITY OF WISCONSIN CIMMS TROPICAL CYCLONE HOMEPAGE SHOW INCREASED VERTICAL SHEAR NEAR 130W LONGITUDE...AND COOLER SEA SURFACE TEMPERATURES ARE IN THE PROJECTED PATH OF THE HURRICANE AS WELL. THEREFORE GRADUAL WEAKENING IS FORECAST AS IN THE PREVIOUS ADVISORY. MOTION IS ESSENTIALLY THE SAME AS BEFORE...285/11. A MID- TO UPPER- TROPOSPHERIC LOW IS SEEN IN WATER VAPOR IMAGERY NEAR 31N130W...BUT THIS FEATURE DOES NOT SEEM TO BE EXERTING MUCH INFLUENCE ON THE MOTION OF DARBY. THE OFFICIAL TRACK FORECAST MORE OR LESS MAINTAINS THE WEST-NORTHWESTWARD MOTION THROUGH THE PERIOD. THIS IS A BLEND OF THE OBJECTIVE GUIDANCE...SANS THE AVN AND NOGAPS MODELS WHOSE TRACKS APPEAR TO BE TOO FAR TO THE SOUTH. PASCH FORECAST POSITIONS AND MAX WINDS INITIAL 26/0900Z 16.3N 124.5W 90 KTS 12HR VT 26/1800Z 16.7N 126.2W 80 KTS 24HR VT 27/0600Z 17.3N 128.5W 70 KTS 36HR VT 27/1800Z 17.9N 131.0W 60 KTS 48HR VT 28/0600Z 18.5N 133.5W 50 KTS 72HR VT 29/0600Z 20.0N 138.0W 40 KTS NNNN