[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 271451
TCDAT1
HURRICANE DANIELLE DISCUSSION NUMBER  25
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062010
1100 AM AST FRI AUG 27 2010

THE OVERALL CLOUD PATTERN OF DANIELLE HAS CHANGED LITTLE SINCE THE
LAST ADVISORY. THE 15-20 NMI DIAMETER EYE REMAINS QUITE DISTINCT
AND EMBEDDED IN THE CENTER OF THE CONVECTIVE CLOUD MASS. CLOUD TOPS
HAVE STARTED TO COOL AND THE COLDEST CLOUD RING NOW ENCIRCLES THE
EYE ABOUT 75 PERCENT. THE SATELLITE CURRENT INTENSITY ESTIMATE FROM
TAFB WAS T6.0/115 KT. ADT ESTIMATES FROM UW-CIMSS ARE T5.9/114 KT
AND AN ODT OF T6.1/117 KT FROM NHC. A BLEND OF THESE INTENSITY
ESTIMATES SUPPORTS MAINTAINING AN INTENSITY OF 115 KT FOR THIS
ADVISORY. AN AIR FORCE RESERVE RECON AIRCRAFT WILL INVESTIGATE
DANIELLE THIS AFTERNOON AND PROVIDE A MORE ACCURATE ASSESSMENT OF
THE INTENSITY.

THE INITIAL MOTION ESTIMATE REMAINS 305/10. DANIELLE HAS MADE A FEW
BRIEF WESTWARD WOBBLES DURING THE PAST FEW HOURS...BUT OVERALL THE
MOTION REMAINS UNCHANGED. THE TRACK WAS NUDGED SLIGHTLY TO THE WEST
THROUGH 36 HOURS MERELY TO ACCOUNT FOR THE SLIGHT WESTWARD POSITION
AT 12Z. THE GUIDANCE MODELS REMAIN VERY TIGHTLY PACKED THROUGH 72
HOURS AND ARE CONSISTENT WITH DANIELLE BEGINNING RECURVATURE TO THE
NORTHEAST BY 24-36 HOURS AS THE HURRICANE ROUNDS THE WESTERN
PERIPHERY OF THE DEEP-LAYER SUBTROPICAL RIDGE SITUATED ALONG 30N
LATITUDE. IT IS POSSIBLE THAT THE OUTFLOW OF DANIELLE ON THE EAST
SIDE THAT IS CONVERGING INTO A BROAD MID-LATITUDE TROUGH TO ITS
NORTHEAST COULD BUILD THE RIDGE SLIGHTLY WESTWARD DURING THE NEXT
24 HOURS. THE RESULT WOULD BE A MORE NORTHERLY MOTION AND SLOWER
RECURVATURE THAN CURRENTLY INDICATED. HOWEVER...THE CYCLONE IS
STILL EXPECTED TO REMAIN WELL TO THE EAST OF BERMUDA. AFTER
RECURVATURE OCCURS...A STRONG MID-LEVEL TROUGH CURRENTLY OVER THE
NORTHEASTERN U.S. IS FORECAST TO ACCELERATE DANIELLE QUICKLY TO THE
NORTHEAST AND THEN CAPTURE THE SYSTEM AT HIGHER LATITUDES AND TURN
IT MORE POLEWARD AFTER 96 HOURS AS A POWERFUL EXTRATROPICAL LOW
PRESSURE SYSTEM. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE
PREVIOUS ADVISORY TRACK THROUGH 72 HOURS...AND THEN A LITTLE FASTER
AND MORE POLEWARD AT DAYS 4 AND 5...WHICH IS CONSISTENT WITH THE
CONSENSUS MODEL...TVCN.

DANIELLE IS EXPECTED TO MOVE INTO A REGION OF LOWER VERTICAL SHEAR
OVER THE NEXT 24 HOURS AS IT APPROACHES THE SUBTROPICAL RIDGE AXIS.
OUTFLOW REMAIN QUITE IMPRESSIVE AND THE IS BEING ENHANCED TO THE
NORTH AND EAST AS THE FLOW INTERACTS WITH BROAD UPPER-LEVEL TROUGH
LOCATED WELL TO THE NORTHEAST OF DANIELLE. GIVEN THE FAVORABLE
UPPER-LEVEL FLOW PATTERN...DECREASING SHEAR...AND SSTS OF 29C...
CONDITIONS APPEAR FAVORABLE FOR SOME SLIGHT STRENGTHENING TO OCCUR
DURING THE NEXT 24 HOURS. HOWEVER...BY 36-48 HOURS...SOUTHWESTERLY
VERTICAL SHEAR AHEAD OF THE U.S. EAST COAST TROUGH IS EXPECTED TO
INCREASE TO 25-30 KT. THE COMBINATION OF THE INCREASING SHEAR AND
DECREASING SSTS SHOULD INITIATE A STEADY WEAKENING TREND. IN THE
96-120 TIME PERIOD...DANIELLE IS EXPECTED TO TRANSITION INTO A
POWERFUL EXTRATROPICAL CYCLONE OVER THE COLD WATERS OF THE NORTH
ATLANTIC. THE OFFICIAL INTENSITY FORECAST IS A BLEND OF THE
SHIPS-GFDL-HWRF INTENSITY MODELS.

FORECAST POSITIONS AND MAX WINDS

INITIAL      27/1500Z 26.9N  59.8W   115 KT
 12HR VT     28/0000Z 27.9N  60.8W   115 KT
 24HR VT     28/1200Z 29.5N  61.2W   115 KT
 36HR VT     29/0000Z 31.5N  60.3W   110 KT
 48HR VT     29/1200Z 34.3N  57.6W    95 KT
 72HR VT     30/1200Z 38.0N  52.0W    80 KT
 96HR VT     31/1200Z 40.5N  43.0W    65 KT
120HR VT     01/1200Z 46.0N  28.0W    60 KT...POST-TROP/EXTRATROP

$$
FORECASTER STEWART

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