CIMMSE TC Wind GroupConference Call

Wednesday, April 10th, 201311 AM

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

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

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

Discussion

Next Conference Call: Wednesday, May 8th, 2013