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HURRICANE DALILA DISCUSSION NUMBER  15
NATIONAL WEATHER SERVICE MIAMI FL
8 AM PDT TUE JUL 24 2001

DALILA CONTINUES TO HAVE CONVECTIVE TOPS OF COLDER THAN -80C CLOSE
TO THE CENTER...AND THERE IS SOME POORLY DEFINED BANDING OVER THE
SOUTHWEST SEMICIRCLE.  SATELLITE INTENSITY ESTIMATES ARE 77 KT...
65 KT...AND 65 KT FROM TAFB...SAB...AND AFWA RESPECTIVELY...SO
THE MAXIMUM WINDS ARE NUDGED UP TO 70 KT.
 
THE INITIAL MOTION IS 280/9.  WATER VAPOR IMAGERY SHOWS A MID-LEVEL
RIDGE OR ANTICYCLONE NORTHWEST OF DALILA...WITH A DEEP LAYER CYCLONE
OVER CALIFORNIA.  LARGE-SCALE MODELS INDICATE THAT THE CYCLONE WILL
DIG FAR ENOUGH SOUTHWARD TO WEAKEN THE RIDGE...BUT NOT FAR ENOUGH
TO BREAK IT.  THIS EVOLUTION SHOULD KEEP DALILA ON A GENERAL WEST TO
WEST-NORTHWEST TRACK WITH SOME DECREASE IN FORWARD SPEED THROUGH
THE FORECAST PERIOD.  NHC HURRICANE GUIDANCE GENERALLY AGREES WITH
THIS SCENARIO...ALTHOUGH THERE IS SOME DIVERGENCE ON HOW FAST
DALILA WILL MOVE.  THE BAM MODELS...LBAR...AND NHC91E ARE MUCH
FASTER...WHILE THE UKMET AND GFDL ARE MUCH SLOWER.  THE OFFICIAL
FORECAST WILL COMPROMISE BETWEEN THESE TWO EXTREMES.
 
DALILA CONTINUES IN LIGHT-TO-MODERATE EASTERLY VERTICAL SHEAR...
AND LARGE-SCALE MODELS SUGGEST THIS WILL PERSIST THROUGH THE
FORECAST PERIOD.  SOME FURTHER STRENGTHENING IS FORECAST OVER THE
NEXT 24 HR BEFORE THE HURRICANE REACHES COLDER WATER.  STEADY
WEAKENING SHOULD OCCUR AFTER THAT TIME...WITH THE ONLY QUESTION
BEING HOW FAST WILL THE WEAKENING BE.  THE INTENSITY FORECAST IS IN
GOOD AGREEMENT WITH THE SHIPS MODEL.  HOWEVER...DALILA COULD WEAKEN
FASTER THAN FORECAST...ESPECIALLY IF IT MOVES TO THE RIGHT OF THE
FORECAST TRACK INTO EVEN COLDER WATER.

ON THE CURRENT FORECAST TRACK DALILA SHOULD PASS NEAR SOCORRO
ISLAND IN ABOUT 12 HR.
  
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     24/1500Z 18.3N 109.6W    70 KTS
12HR VT     25/0000Z 18.6N 111.0W    75 KTS
24HR VT     25/1200Z 18.9N 112.4W    80 KTS
36HR VT     26/0000Z 19.3N 113.7W    75 KTS
48HR VT     26/1200Z 19.6N 115.0W    70 KTS
72HR VT     27/1200Z 20.0N 117.5W    60 KTS
 
 
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