Hurricane DANIELLE

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HURRICANE DANIELLE DISCUSSION NUMBER  27
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062010
1100 PM AST FRI AUG 27 2010

CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY INDICATES THAT DANIELLE
HAS STARTED AN EYEWALL REPLACEMENT CYCLE DURING THE PAST SEVERAL
HOURS...WITH A 60 NM WIDE OUTER EYEWALL FORMING AROUND THE 15-20 NM
WIDE INNER EYEWALL. THE INITIAL INTENSITY REMAINS 115 KT FOR THIS
ADVISORY BASED ON SATELLITE ESTIMATES FROM TAFB AND SAB...BUT THIS
COULD BE A LITTLE GENEROUS DUE TO THE EYEWALL REPLACEMENT. AN AIR
FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS ENROUTE TO INVESTIGATE
DANIELLE. THE HURRICANE REMAINS IN A LIGHT VERTICAL SHEAR
ENVIRONMENT WITH GOOD TO EXCELLENT CIRRUS OUTFLOW IN ALL
DIRECTIONS.
 
THE HURRICANE HAS TURNED TO THE RIGHT DURING THE PAST 6 HR WITH THE
INITIAL MOTION NOW 335/8.  THE TRACK GUIDANCE IS IN GOOD AGREEMENT
THAT DANIELLE SHOULD TURN TOWARD THE NORTHEAST DURING THE NEXT 24
HOURS AND ACCELERATE INTO THE WESTERLIES THEREAFTER.  THERE IS SOME
SPREAD IN THE GUIDANCE ON THE SPEED OF MOTION DURING EXTRATROPICAL
TRANSITION...WITH THE GFS AND CANADIAN MODELS SHOWING A FASTER
MOTION THAN THE EUROPEAN AND THE UKMET.  THE TRACK FORECAST SPLITS
THE DIFFERENCE BETWEEN THOSE EXTREMES.
 
IT IS UNLIKELY THAT DANIELLE WILL HAVE TIME TO COMPLETE THE EYEWALL
REPLACEMENT CYCLE BEFORE IT ENCOUNTERS DECREASING SEA SURFACE
TEMPERATURES AND INCREASING WIND SHEAR IN 24 HR OR SO.  THE NEW
INTENSITY FORECAST CALLS FOR A 115 KT INTENSITY FOR 12 HR...WITH
STEADY WEAKENING THEREAFTER.  EXTRATROPICAL TRANSITION SHOULD BEGIN
AT ABOUT 96 HR AND BE COMPLETE BY 120 HR.  THE DYNAMICAL MODELS
FORECAST DANIELLE TO REMAIN A STRONG CYCLONE THROUGH TRANSITION...
AND THIS IS REFLECTED IN THE INTENSITY FORECAST.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      28/0300Z 28.1N  60.6W   115 KT
 12HR VT     28/1200Z 29.2N  60.7W   115 KT
 24HR VT     29/0000Z 31.5N  59.4W   110 KT
 36HR VT     29/1200Z 34.2N  57.1W   100 KT
 48HR VT     30/0000Z 36.8N  53.9W    85 KT
 72HR VT     31/0000Z 40.0N  46.5W    70 KT
 96HR VT     01/0000Z 43.0N  37.5W    65 KT
120HR VT     02/0000Z 51.5N  28.5W    65 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BEVEN
 
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