Hurricane DANIELLE

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HURRICANE DANIELLE DISCUSSION NUMBER  16
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062010
1100 AM AST WED AUG 25 2010

DANIELLE HAS A LARGE CENTRAL DENSE OVERCAST THIS MORNING WITH
CLOUD TOPS TO -80C.  HOWEVER...RECENT MICROWAVE IMAGERY SHOWS THAT
THE CONVECTION IS ORGANIZED IN BANDS EAST OF THE CENTER WITH NO
EVIDENCE OF AN EYEWALL.  UPPER-LEVEL WESTERLY WINDS ASSOCIATED WITH
A TROUGH TO THE NORTHWEST OF THE HURRICANE ARE CAUSING 15-20 KT OF
WESTERLY VERTICAL SHEAR...AND THIS HAS LIKELY AFFECTED THE
CONVECTIVE STRUCTURE.  SATELLITE INTENSITY ESTIMATES REMAIN 90 KT
FROM TAFB AND 65 KT FROM SAB.  BASED ON THIS...THE INITIAL
INTENSITY REMAINS 75 KT...AND THIS MIGHT BE A LITTLE GENEROUS.  THE
CIRRUS OUTFLOW IS FAIR IN THE EASTERN SEMICIRCLE AND RESTRICTED
ELSEWHERE.

THE INITIAL MOTION REMAINS 300/15.  DANIELLE IS ON THE SOUTHWEST
SIDE OF A LOW/MID-LEVEL RIDGE OVER THE CENTRAL ATLANTIC...WHICH
SHOULD STEER THE CYCLONE IN A GENERAL NORTHWESTERLY DIRECTION WITH
SOME DECREASE IN FORWARD SPEED DURING THE NEXT 72 HR.  AFTER
THAT...DANIELLE IS EXPECTED TO TURN NORTHWARD INTO A WEAKNESS
BETWEEN THE ATLANTIC RIDGE AND A LOW/MID-LEVEL RIDGE OVER THE
EASTERN UNITED STATES.  THE TRACK GUIDANCE SHOWS SOME SPREAD DURING
THIS TIME DUE TO UNCERTAINTIES IN HOW DANIELLE MAY INTERACT WITH A
WEAK MID-LEVEL TROUGH TO THE WEST AND HOW MUCH MID-LEVEL RIDGING
MAY DEVELOP NORTH OF THE HURRICANE.  THE NOGAPS SHOWS THE MOST
RIDGING...AND IN RESPONSE TURNS DANIELLE NORTHWESTWARD.  THE
ECWMF SHOWS A STRONGER TROUGH AND LESS RIDGING...AND IN CONSEQUENCE
TURNS THE HURRICANE NORTHEASTWARD BY 120 HR.  THE OTHER MODELS ARE
IN BETWEEN THESE EXTREMES...WITH THE VARIOUS CONSENSUS MODELS
FORECASTING A NORTHWARD MOTION.  THE NEW FORECAST TRACK IS DOWN THE
MIDDLE OF THE GUIDANCE ENVELOP AND IS SIMILAR TO THE PREVIOUS
FORECAST.
 
DANIELLE SHOULD PASS TO THE EAST AND NORTH OF THE NEARBY UPPER-LEVEL
TROUGH IN ABOUT 24 HR...WHICH IS EXPECTED TO LEAD TO A DECREASE IN
THE SHEAR.  ALL GUIDANCE AGREES ON INTENSIFICATION DURING THE 24-72
HR PERIOD...WITH THE GFDL AND GFDN FORECASTING DANIELLE TO BECOME A
MAJOR HURRICANE.  THE SHIPS AND LGEM MODELS ARE LESS AGGRESSIVE...
AND THE INTENSITY FORECAST CALL FOR A 95 KT PEAK INTENSITY THAT IS
CLOSE TO THE INTENSITY CONSENSUS.  AFTER 72 HR...THE DYNAMICAL
MODELS AGREE THAT AN UPPER-LEVEL TROUGH DEVELOPING WEST OF DANIELLE
SHOULD CAUSE SIGNIFICANT SOUTHWESTERLY SHEAR...AND THE INTENSITY
FORECAST FOR THIS TIME THUS CALLS FOR ARRESTED DEVELOPMENT FOLLOWED
BY WEAKENING.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      25/1500Z 19.6N  52.3W    75 KT
 12HR VT     26/0000Z 20.8N  53.9W    75 KT
 24HR VT     26/1200Z 22.3N  55.7W    80 KT
 36HR VT     27/0000Z 23.7N  57.4W    80 KT
 48HR VT     27/1200Z 24.9N  59.0W    85 KT
 72HR VT     28/1200Z 27.5N  61.5W    95 KT
 96HR VT     29/1200Z 30.5N  62.0W    95 KT
120HR VT     30/1200Z 34.0N  62.0W    85 KT
 
$$
FORECASTER BEVEN
 
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