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TROPICAL STORM DALILA DISCUSSION NUMBER  21
NATIONAL WEATHER SERVICE MIAMI FL
8 PM PDT WED JUL 25 2001
 
DALILA HAS STRENGTHENED SLIGHTLY AS THE CENTRAL DEEP CONVECTION HAS 
BECOME BETTER ORGANIZED.  THE VERTICAL SHEAR HAS WEAKENED ENOUGH TO 
ALLOW FOR A MORE CIRCULAR OUTFLOW PATTERN TO DEVELOP DURING THE PAST 
6 HOURS.  THE INITIAL INTENSITY IS INCREASED TO 60 KT BASED ON 
DVORAK SATELLITE INTENSITY ESTIMATES OF 65 KT...EMBEDDED CENTER 
PATTERN...FROM TAFB AND 55 KT FROM SAB.  THIS IS ALSO SUPPORTED BY 
THE UW-CIMMS AMSU INTENSITY ESTIMATES SHOWING A PRESSURE DECREASE 
DOWN TO 992 MB.
 
THE INITIAL MOTION ESTIMATE REMAINS AT 285/6.  ALL OF THE DYNAMICAL 
MODELS HAVE CONTINUED THE TREND OF TURNING DALILA SHARPLY TO THE 
NORTHWEST FOR THE FIRST 24 HOURS AND THEN TAKING THE CYCLONE 
WESTWARD AFTER THAT.  THIS TREND HAS PERSISTED FOR SEVERAL MODEL 
RUNS NOW AND IT HAS YET TO OCCUR.  SURFACE ANALYSES INDICATE THE 
RIDGE TO THE NORTH AND WEST OF DALILA HAS BUILT SOUTHWARD AS THE 
REMNANT LOW THAT WAS ONCE TROPICAL STORM ERICK HAS WEAKENED AND 
BECOME LESS DISTINCT.  THE INCREASING EFFECT OF THE LOW- TO 
MID-LEVEL RIDGING SHOULD KEEP THE CYCLONE ON A WEST-NORTHWEST OR 
WESTWARD TRACK THROUGHOUT THE PERIOD.  THE OFFICIAL FORECAST IS 
BETWEEN THE DYNAMICAL MODELS CONSENSUS AND CLIPER...AND JUST A 
LITTLE SOUTH OF THE PREVIOUS FORECAST TRACK.
 
ALTHOUGH DALILA IS MOVING OVER COOLER WATER...SSTS ARE STILL ABOVE 
27C AND IT IS POSSIBLE THAT DALILA COULD REACH MINIMAL HURRICANE 
INTENSITY AGAIN DURING THE NEXT 12 HOURS OR SO.  HOWEVER...ALL OF 
THE GLOBAL MODELS INDICATE ANOTHER SURGE OF STRONG UPPER-LEVEL 
EASTERLY FLOW WILL AFFECT THE CYCLONE BY 24 HOURS...WHICH WILL 
INCREASE THE VERTICAL SHEAR ONCE AGAIN.  THE OFFICAL FORECAST SHOWS 
SLOW WEAKENING THROUGH 24 HOURS AND THEN A SLIGHTLY FASTER DECREASE 
IN INTENSITY AFTER THAT.  THIS IS CONSISTENT WITH THE SHIPS 
INTENSITY MODEL AND ALSO MAINTAINS CONTINUITY WITH THE PREVIOUS 
INTENSITY FORECAST TREND.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     26/0300Z 19.4N 113.2W    60 KTS
12HR VT     26/1200Z 19.6N 114.2W    55 KTS
24HR VT     27/0000Z 19.9N 115.5W    50 KTS
36HR VT     27/1200Z 20.2N 116.8W    40 KTS
48HR VT     28/0000Z 20.5N 118.1W    30 KTS
72HR VT     29/0000Z 21.0N 120.5W    25 KTS...DISSIPATING
 
 
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