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TROPICAL STORM DALILA DISCUSSION NUMBER  18
NATIONAL WEATHER SERVICE MIAMI FL
2 AM PDT WED JUL 25 2001
 
THE CENTER OF DALILA IS VERY DIFFICULT TO LOCATE...AND IS BEING
ESTIMATED LARGELY BY CONTINUITY OF THE PREVIOUS TRACK.  THE FORWARD
SPEED DROPPED A LITTLE OVER THE PAST 12 HOURS...PRESUMABLY BECAUSE
THE COLD LOW OVER SOUTHERN CALIFORNIA HAS BEEN ERODING THE RIDGE TO
THE NORTH OF THE TROPICAL CYCLONE.  ALL GUIDANCE EXCEPT THE GFDL
INDICATES A GENERAL WEST-NORTHWEST TRACK THROUGH THE FORECAST
PERIOD.  THE GFDL TURNS DALILA SHARPLY NORTHWARD AFTER 48 HOURS...
BUT THIS APPEARS TO BE AN ARTIFACT CAUSED BY A DISORGANIZATION OF
THE VORTEX IN THE MODEL.  THE AVN SHOWS A SLIGHT AND REASONABLE BEND
TO THE RIGHT OVER THE NEXT 24-36 HOURS IN RESPONSE TO THE COLD
LOW...AND ON THIS BASIS THE OFFICIAL FORECAST IS NUDGED SLIGHTLY TO
THE RIGHT OF THE PREVIOUS ADVISORY.

DVORAK T NUMBERS YIELD 55 KT AND THE OFFICIAL INTENSITY IS LOWERED 
TO THIS VALUE.  NORTHEASTERLY SHEAR IS STILL AN INHIBITING 
FACTOR...AND THERE ARE SOME HINTS IN THE SATELLITE IMAGERY THAT THE 
CYCLONE HAS BECOME LESS WELL ORGANIZED.  THE SHIPS MODEL WEAKENS 
DALILA ONLY VERY SLOWLY THROUGH 36 HOURS IN ANTICIPATION THAT THE 
SHEAR WILL LESSEN. HOWEVER THIS MODEL...GENERALLY THE BEST INTENSITY 
GUIDANCE WE HAVE...HAS CONSISTENTLY OVERESTIMATED THIS STORM.

FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     25/0900Z 19.1N 111.5W    55 KTS
12HR VT     25/1800Z 19.4N 112.6W    50 KTS
24HR VT     26/0600Z 19.9N 113.9W    45 KTS
36HR VT     26/1800Z 20.3N 115.2W    35 KTS
48HR VT     27/0600Z 20.5N 116.5W    30 KTS
72HR VT     28/0600Z 21.0N 119.5W    25 KTS...DISSIPATING
 
 
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