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TROPICAL STORM DALILA DISCUSSION NUMBER  19
NATIONAL WEATHER SERVICE MIAMI FL
8 AM PDT WED JUL 25 2001
 
A NEW CONVECTIVE BURST OCCURRED NEAR THE CENTER OF DALILA OVER THE
PAST FEW HOURS.  THE STORM REMAINS IN NORTHEASTERLY SHEAR...AND THE
CONVECTIVE TOPS ARE ALREADY WARMING. BASED ON THIS...AND ON
SATELLITE INTENSITY ESTIMATES OF 65 KT...55 KT...AND 55 KT FROM
TAFB...SAB...AND AFWA...THE INITIAL INTENSITY WILL REMAIN 55 KT.

THE MAIN EFFECT OF THE BURST IS TO OBSCURE THE LOW LEVEL CENTER.
EVEN ALLOWING FOR THE DIFFICULTY IN CENTER LOCATION...IT APPEARS
THAT DALILA HAS SLOWED FURTHER WITH THE BEST ESTIMATE OF THE
INITIAL MOTION 285/5.  WATER VAPOR IMAGERY SHOWS A MID/UPPER-LEVEL
TROUGH OVER SOUTHERN CALIFORNIA CUTTING INTO THE RIDGE NORTH OF
DALILA...WHICH IS THE MOST LIKELY REASON FOR THE SLOWING.  LARGE-
SCALE MODELS CONTINUE TO INDICATE THE RIDGE...ALTHOUGH WEAK...WILL
REMAIN BETWEEN DALILA AND THE TROUGH...THUS CONTINUING A WEST-
NORTHWEST TO WEST MOTION.  NHC HURRICANE GUIDANCE AGREES WITH
THIS...ALTHOUGH THE LARGE DIFFERENCES IN GUIDANCE SPEED NOTED
YESTERDAY CONTINUE TODAY.  THE OFFICIAL FORECAST IS SIMILAR TO...
BUT SLOWER THAN...THE PREVIOUS PACKAGE IN BEST AGREEMENT WITH
NHC91 AND CLIPER.

WHILE DALILA REMAINS SHEARED...SATELLITE WINDS FROM CIMSS SUGGEST 
THE SHEAR IS SOMEWHAT LESS THAN 24 HR AGO.  HOWEVER...THE FORECAST
TRACK MOVES THE CYCLONE OVER 24C WATER BY 72 HR.  THE INTENSITY
FORECAST WILL CONTINUE TO CALL FOR GRADUAL WEAKENING...WITH DALILA
STARTING TO DISSIPATE BY 72 HR.  IT IS NOTABLE THAT THE GFDL
DISSIPATES THE SYSTEM IN 52 HR.

THE RADII OF 12 FT SEAS HAS BEEN REDUCED SOMEWHAT BASED ON DATA
FROM SHIP 9VJO ABOUT 140 N MI SOUTHWEST OF THE CENTER.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     25/1500Z 19.2N 111.7W    55 KTS
12HR VT     26/0000Z 19.4N 112.4W    50 KTS
24HR VT     26/1200Z 19.7N 113.4W    45 KTS
36HR VT     27/0000Z 20.0N 114.5W    35 KTS
48HR VT     27/1200Z 20.4N 115.7W    30 KTS
72HR VT     28/1200Z 21.0N 118.0W    25 KTS...DISSIPATING
 
 
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