1. CIMMSE TC Wind Group Conference Call Wednesday, April 10 th, 2013 11 AM

2. Agenda Holland et al. (2010) Error Function Update Modified Rankine Vortex Error Function

3. 3 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

4. 4 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 do end do

5. 5 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

8. 8 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

11. 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

12. 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

13. Discussion Next Conference Call: Wednesday, May 8 th, 2013