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CIMMSE TC Wind GroupConference Call
Wednesday, April 10th, 201311 AM
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Agenda
• Holland et al. (2010) Error Function Update• Modified Rankine Vortex Error Function
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Holland et al. Error Analysis
• Goal: potential hybrid approach to improved interpolation method
• Minimize error method
• Hypothesis we are testing:-There are systematic interpolation errors over the 219 available analysis
times as a function of distance from storm center-Develop error function E(q,r) to model these errors to improve the
Holland et al. interpolation method
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Holland et al. Error Analysis: Method
• Minimize error method– Use all 219 storm analysis times
do ts = 1->num_available_analysis_times do i = quadrant 1->4 //calculate average hwind analyzed wind speed at the
various distances from storm center (1)
//calculate Holland et al interpolated wind speed at the various distances from storm center (2)
//take difference of (1) and (2) to provide estimate of
quadrant error for the analysis time based on distance from storm center (where data available for both)
end doend do
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Holland et al. Error Analysis
• For each quadrant and analysis time we then:– Calculate average error, binning each 5 km
distances from storm center– Normalize error relative to best track maximum
sustained winds provided by NHC for the analysis time
• Result: four plots (one for each quadrant), normalized error vs. distance from storm center
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Holland et al. (2010) Update
• Can create improved Holland Interpolated Wind Field:
Holland_Improved(q, d) = Holland Interp(q, d) - Normalized Interp Error Function (q, d) * Max Wind
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Summary: Advantages/Disadvantages
• Holland et al. Error Function: – Advantage• Pretty direct relationship of error as function of
distance
– Disadvantages• Holland et al. would need to be coded into
TCMWindTool• Holland et al. initial plots do not show improvement
over modified Rankine
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Summary: Advantages/Disadvantages
• Modified Rankine Error Function: – Advantages• Already coded into TCMWindTool• Shown to perform better than Holland et al. model
– Disadvantages• When looking at all storms as a function of distance,
error not as direct function with distance– Larger spread in error as function of radius among different
times/storms– Likely attributable to dependence on 34, 50, and 64 knot
maximum wind radii
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Discussion
Next Conference Call: Wednesday, May 8th, 2013