[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 280850
TCDAT1
HURRICANE DANIELLE DISCUSSION NUMBER  28
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062010
500 AM AST SAT AUG 28 2010

DATA FROM THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INDICATE
THAT DANIELLE HAS WEAKENED...LIKELY AS A RESULT OF AN EYEWALL
REPLACEMENT CYCLE.  THE AIRCRAFT FOUND CONCENTRIC EYEWALLS WITH
RADII OF 20 AND 60 NM AROUND 0345 UTC...AND SUBSEQUENT SATELLITE
IMAGERY SUGGESTS THAT THE INNER EYEWALL HAD CONTINUED TO ERODE.  THE
AIRCRAFT MEASURED A MAXIMUM FLIGHT LEVEL WIND OF 100 KT AND A
CENTRAL PRESSURE OF 950 MB.  BASED ON THIS...THE INITIAL INTENSITY
IS DECREASED TO 95 KT FOR THIS ADVISORY.  WHILE ENVIRONMENTAL
CONDITIONS REMAIN FAVORABLE FOR THE NEXT DAY OR SO...DANIELLE WILL
NOT LIKELY HAVE ENOUGH TIME TO RESTRENGTHEN SIGNIFICANTLY AFTER THE
EYEWALL CYCLE COMPLETES.  THE INTENSITY FORECAST SHOWS LITTLE
CHANGE FOR THE NEXT 24 HOURS...AND A SLOW WEAKENING IS INDICATED
BEYOND THAT TIME AS THE VERTICAL SHEAR INCREASES AND THE HURRICANE
BEGINS TO MOVE OVER COOLER WATERS.  LATE IN THE PERIOD...DANIELLE
WILL LIKELY TRANSITION INTO A LARGE AND POWERFUL EXTRATROPICAL
CYCLONE OVER THE NORTH ATLANTIC...AND ONLY SLOW WEAKENING IS
INDICATED DURING THE TRANSITION PROCESS.

THE AIRCRAFT FIXED THE CENTER A LITTLE TO THE LEFT OF PREVIOUS
ESTIMATES...AND SHOWED THAT DANIELLE HAS SLOWED A LITTLE.  THE
INITIAL MOTION ESTIMATE NORTH-NORTHWEST OR 345/8.  THE TRACK
GUIDANCE IS TIGHTLY CLUSTERED OVER THE FIRST 24 TO 36 HOURS...AS
DANIELLE WILL ACCELERATE TOWARD THE NORTH AND NORTHEAST AS IT
INTERACTS WITH A LARGE MID- TO UPPER-LEVEL TROUGH MOVING OFFSHORE
OF THE U.S. EAST COAST.  BEYOND THAT TIME...DANIELLE WILL SLOW
TEMPORARILY FROM 48 TO 72 HOURS AS THE FIRST UPPER-TROUGH LIFTS
OUT...AND THEN ACCELERATE AGAIN TOWARD THE EAST-NORTHEAST AS
ANOTHER TROUGH CAPTURES THE CYCLONE AND THEN PULLS IT SHARPLY
NORTHWARD BY DAY 5.  THE OFFICIAL FORECAST HAS BEEN ADJUSTED A
LITTLE TO THE LEFT OF THE PREVIOUS ONE THROUGH 24 HOURS DUE TO THE
MORE WESTERLY INITIAL POSITION OF THE CYCLONE.  BEYOND THAT
TIME...A MORE SIGNIFICANT ADJUSTMENT TO THE LEFT OF THE PREVIOUS
TRACK WAS MADE TOWARD THE MODEL CONSENSUS THROUGH 48 HOURS...AND
TOWARD A BLEND OF THE GFS AND ECMWF AT 72 HOURS AND BEYOND.

FORECAST POSITIONS AND MAX WINDS

INITIAL      28/0900Z 28.6N  61.0W    95 KT
 12HR VT     28/1800Z 30.2N  60.6W    95 KT
 24HR VT     29/0600Z 33.2N  58.6W    95 KT
 36HR VT     29/1800Z 36.7N  56.1W    90 KT
 48HR VT     30/0600Z 38.9N  54.3W    85 KT
 72HR VT     31/0600Z 41.5N  47.0W    70 KT
 96HR VT     01/0600Z 47.1N  32.4W    70 KT...POST-TROP/EXTRATROP
120HR VT     02/0600Z 54.5N  35.5W    60 KT...POST-TROP/EXTRATROP

$$
FORECASTER BRENNAN


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