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Hurricane DANIELLE


ZCZC MIATCDAT1 ALL
TTAA00 KNHC DDHHMM
HURRICANE DANIELLE DISCUSSION NUMBER  34
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062010
500 PM AST SUN AUG 29 2010
 
DEEP CONVECTION AROUND DANIELLE HAS BECOME RATHER ASYMMETRIC WITH
MOST OF THE COOL CLOUD TOPS OCCURRING IN THE CYCLONE'S NORTHERN
SEMICIRCLE. CORRESPONDING...DVORAK CURRENT INTENSITY ESTIMATES FROM
SAB AND TAFB ARE DROPPING WITH 3.5...OR 55 KT...AND 4.0...OR 65
KT...RESPECTIVELY. FORTUNATELY...A FORTUITOUS ASCAT PASS WAS
RECEIVED FROM 1404Z WHICH SHOWED SEVERAL BELIEVABLE HURRICANE 
FORCE WIND VECTORS. A CIMSS AMSU INTENSITY ESTIMATE FROM A 1626Z
NOAA-19 OVERPASS EVEN SUGGESTED CATEGORY TWO INTENSITY...THOUGH
THIS APPEARS TO BE TOO HIGH. THE INITIAL INTENSITY IS SET AT 70 KT
AS A BLEND OF THESE. DANIELLE CONTINUES TO EXHIBIT SOME
BAROCLINICITY... WHICH IS BEING MANIFEST THROUGH THE COLD AIR
ADVECTION ON THE NORTH AND WEST SIDE OF THE CYCLONE.  HOWEVER...AS
THE SYSTEM MOVES NORTHEASTWARD AND A SURFACE HIGH REMAINS NEARLY
STATIONARY OVER THE MID-ATLANTIC STATES...THE EXTRATROPICAL
TRANSITION SHOULD BE DELAYED.
 
DANIELLE CONTINUES TO ACCELERATE TOWARD THE NORTH-NORTHEAST WITH A
CURRENT SPEED OF ABOUT 25 KT. THERE WAS CONCERN THAT WE WERE
FOLLOWING A MID-LEVEL VORTEX RATHER THAN THE SURFACE CIRCULATION.
HOWEVER...GEOSTATIONARY VISIBLE AND POLAR ORBITING MICROWAVE IMAGERY
SUGGESTS THAT THE VORTEX IS STILL COHERENT VERTICALLY. DANIELLE
SHOULD DECELERATE SOME AND TURN TOWARD THE EAST-NORTHEAST BY
TOMORROW UNDER THE INFLUENCE OF A VIGOROUS SHORTWAVE TROUGH TO ITS
NORTHWEST AND A SUBTROPICAL RIDGE TO ITS SOUTHEAST. MOST OF THE
MODELS LOSE THE VORTEX IN ABOUT 48 HR WHEN THE SYSTEM BECOMES
EXTRATROPICAL. THIS IS BECAUSE THERE IS A PROMINENT BAROCLINIC
DEVELOPMENT JUST NORTH OF DANIELLE...WHICH MAY RESULT IN THE VORTEX
FROM DANIELLE BECOMING ABSORBED AT THAT TIME. ASSUMING THAT 
DANIELLE REMAINS THE PRIMARY CYCLONE AFTER EXTRATROPICAL
TRANSITION...A TRACK FORECAST IS PROVIDED THROUGH 96 HR. THE
FORECAST TRACK IS FASTER THAN THE PREVIOUS ADVISORY AND MODEL
CONSENSUS FOR THE NEXT 24 HR BECAUSE OF THE FASTER INITIAL MOTION
THAN ANTCIPATED...AND THEN SIMILAR TO BOTH THEREAFTER. UNTIL
EXTRATROPICAL TRANSITION IN ABOUT TWO DAYS...DANIELLE SHOULD WEAKEN
GRADUALLY DUE TO MODERATE VERTICAL SHEAR AND DECREASING SSTS UNDER
ITS TRACK. THE OCEAN PREDICTION CENTER PROVIDED POSITION...
INTENSITY...AND SIZE GUIDANCE FOR THE EXTRATROPICAL PORTION OF
DANIELLE.
 
THE 1404Z ASCAT PASS ALLOWED FOR A SLIGHT ENLARGEMENT OF THE
34...50...AND 64 KT WIND RADII ESTIMATED FOR THE INITIAL TIME.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      29/2100Z 38.0N  54.5W    70 KT
 12HR VT     30/0600Z 40.1N  52.9W    65 KT
 24HR VT     30/1800Z 41.3N  50.2W    60 KT
 36HR VT     31/0600Z 42.3N  45.5W    55 KT
 48HR VT     31/1800Z 44.0N  39.0W    60 KT...POST-TROP/EXTRATROP
 72HR VT     01/1800Z 51.0N  30.0W    60 KT...POST-TROP/EXTRATROP
 96HR VT     02/1800Z 57.6N  32.5W    50 KT...POST-TROP/EXTRATROP
120HR VT     03/1800Z...DISSIPATED
 
$$
FORECASTER LANDSEA/BERG
 
NNNN


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Page last modified: Friday, 15-Apr-2011 12:09:07 UTC