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HURRICANE DALILA DISCUSSION NUMBER  16
NATIONAL WEATHER SERVICE MIAMI FL
2 PM PDT TUE JUL 24 2001
 
EASTERLY VERTICAL SHEAR HAS TAKEN A TOLL ON DALILA.  THE LOW LEVEL
CENTER BECAME EXPOSED FOR A SHORT TIME BEFORE A NEW BURST OF
CONVECTION PARTIALLY COVERED IT.  A TRMM SATELLITE OVERPASS AT
1205Z THAT WAS NOT AVAILABLE FOR THE PREVIOUS PACKAGE SHOWED ONLY
A PARTIAL EYEWALL AT BEST...WHICH CASTS SOME DOUBTS AS TO WHETHER
DALILA WAS AS STRONG AS PREVIOUSLY THOUGHT.  THE MAXIMUM WINDS ARE
DECREASED TO 65 KT FOR THIS PACKAGE...AND THAT MIGHT BE A LITTLE
GENEROUS.

THE EXPOSED CENTER WAS A LITTLE NORTH OF THE PREVIOUS FORECAST
TRACK...AND THE INITIAL MOTION IS NOW 290/9.  THE FORECAST
PHILOSOPHY IS LITTLE CHANGED FROM THE PREVIOUS PACKAGE...AS DALILA
SHOULD STAY SOUTH OF A LOW TO MID-LEVEL SUBTROPICAL RIDGE THAT WILL
BE SOMEWHAT WEAKENED BY A DEEP-LAYER TROUGH DURING THE FORECAST
PERIOD.  NHC HURRICANE GUIDANCE IS IN FAIRLY GOOD AGREEMENT ON THE
FORECAST TRACK...ALTHOUGH THERE IS STILL A LARGE SPREAD IN SPEED
BETWEEN THE FASTER BAM MODELS...LBAR...AND NHC91 AND THE SLOWER
AVN...UKMET...AND GFDL.  THE OFFICIAL FORECAST WILL BE SIMILAR TO
AND SHIFTED NORTH FROM THE PREVIOUS PACKAGE...AND AGAIN BE A
COMPROMISE ON THE SPEED.

SATELLITE WINDS FROM CIMSS AT THE UNIVERSITY OF WISCONSIN SHOWS
25-30 KT EASTERLY UPPER LEVEL FLOW OVER DALILA.  WHILE LARGE-SCALE
MODELS CONTINUE TO SUGGEST THESE WINDS SHOULD DECREASE DURING THE
FORECAST PERIOD...THE FORECAST TRACK TAKES THE CYCLONE OVER 24C
WATER BY 72 HR.  THE INTENSITY FORECAST IS CHANGED FROM SHORT-TERM
STRENGTHENING TO SLOW WEAKENING THROUGH THE FORECAST PERIOD.  DALILA
COULD WEAKEN FASTER THAN INDICATED HERE...ESPECIALLY IF THE CYCLONE
MOVES TO THE RIGHT OF THE FORECAST TRACK.

THE CHANGE IN THE INTENSITY FORECAST REQUIRES CHANGES FROM THE 
PREVIOUS WIND RADII FORECAST...WHICH WAS BASED ON THE IDEA THAT
DALILA WOULD GET LARGER AS IT GOT STRONGER.  IT NOW APPEARS UNLIKELY
THAT THIS WILL HAPPEN.

ON THE CURRENT FORECAST TRACK DALILA SHOULD PASS NEAR SOCORRO
ISLAND IN THE NEXT FEW HOURS.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     24/2100Z 18.9N 110.3W    65 KTS
12HR VT     25/0600Z 19.3N 111.6W    60 KTS
24HR VT     25/1800Z 19.8N 113.3W    50 KTS
36HR VT     26/0600Z 20.3N 114.9W    40 KTS
48HR VT     26/1800Z 20.6N 116.4W    35 KTS
72HR VT     27/1800Z 21.0N 118.5W    30 KTS
 
 
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