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TROPICAL STORM DALILA DISCUSSION NUMBER  25
NATIONAL WEATHER SERVICE MIAMI FL
8 PM PDT THU JUL 26 2001
 
DALILA CONTINUES TO GENERATE PULSES IN THE CDO PATTERN LIKE IT HAS 
THE PAST 3 NIGHTS AS THE VERTICAL SHEAR WEAKENS AT NIGHT AND THEN 
INCREASES AGAIN DURING THE DAY.  THE INITIAL INTENSITY OF 55 KT IS 
BASED ON DVORAK SATELLITE INTENSITY ESTIMATES OF 55 KT...T3.5...FROM 
TAFB AND AFWA...AND 65 KT...T4.0 EMBEDDED CENTER...FROM SAB.  THE 
INTENSITY WAS HELD AT 55 KT SINCE EMBEDDED CENTER PATTERN HAS NOT 
BEEN PERSISTING FOR MORE THAN A COUPLE HOURS BEFORE WEAKENING AGAIN.
 
THE INITIAL MOTION ESTIMATE IS 285/8 OVER THE PAST 12 HOURS.  DURING 
THE PAST 6 HOURS...THE MOTION HAS BEEN CLOSER TO 275 DEGREES.  THE 
INITIAL POSITION WAS KEPT SLIGHTLY NORTH OF THE SATELLITE FIX 
POSITIONS TO SMOOTH OUT THE SHEAR-INDUCED WOBBLES IN THE TRACK. 
THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK 
PHILOSOPHY. THE LATEST MODEL GUIDANCE IS EVEN MORE TIGHTLY CLUSTERED 
ABOUT A WEST-NORTHWESTWARD OR WESTWARD TRACK THROUGHOUT THE FORECAST 
PERIOD. IN FACT...THE AVN MODEL IS NOW THE SOUTHERNMOST OF ALL THE 
DYNAMICAL MODELS AND TAKES THE CYCLONE MORE WESTWARD.  THE OFFICIAL 
TRACK IS CLOSE TO THE UKMET-AVN CONSENSUS AND JUST A LITTLE SOUTH OF 
THE PREVIOUS FORECAST TRACK.
 
THE AFOREMENTIOEND VERTICAL SHEAR ACROSS DALILA CONTINUES TO HAVE A 
DISTINCT DIURNAL FLUCTUATION.  ANOTHER SURGE IN THE EASTERLY 
UPPER-LEVEL FLOW CAN BE SEEN IN SATELLITE IMAGERY PASSING SOCORRO 
ISLAND.  THAT SURGE SHOULD BE IMPINGING ON THE CYCLONE WITHIN THE 
NEXT 12 HOURS OR LESS.  AS SUCH...SLOW BUT STEADY WEAKENING IS 
FORECAST SINCE DALILA WILL ALSO BE MOVING OVER SUB-25C SST WATER IN 
6 TO 12 HOURS.  THIS SCENARIO IS CONSISTENT WITH THE SHIPS INTENSITY 
MODEL AND THE PREVIOUS FORECAST INTENSITY TREND.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     27/0300Z 20.2N 115.9W    55 KTS
12HR VT     27/1200Z 20.6N 117.1W    50 KTS
24HR VT     28/0000Z 21.0N 118.5W    45 KTS
36HR VT     28/1200Z 21.3N 120.0W    40 KTS
48HR VT     29/0000Z 21.4N 121.2W    30 KTS
72HR VT     30/0000Z 21.5N 123.5W    25 KTS...DISSIPATING
 
 
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