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TC Winds Conference Call

TC Winds Conference Call. Wednesday, February 6, 2013 11 :00 AM. Agenda. Holland et al. (2010) interpolation update Gust Forecast Discussion Gust factor as function of averaging time Consistency among forecasters for averaging time? Better representation for regression equation.

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TC Winds Conference Call

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  1. TC Winds Conference Call Wednesday, February 6, 2013 11:00 AM

  2. Agenda • Holland et al. (2010) interpolation update • Gust Forecast Discussion • Gust factor as function of averaging time • Consistency among forecasters for averaging time? • Better representation for regression equation

  3. Holland et al. (2010) Interpolation Update • Examined all Atlantic hurricanes 2005-2011 • Compared H*Wind analyses to interpolated wind field from modified Rankine method and Holland et al. (2010) method (271 comparisons) • Using outermost closed isobar for anchoring led to significant error • Too storm symmetric (only one value for the storm) • No estimated wind speed provided by NHC for this distance from storm center • Images for the 34 knot anchoring have begun to be uploaded at http://www4.ncsu.edu/~bptyner/holland.html (will be completed by end of the week)

  4. Holland et al. (2010) Update • Goal: potential hybrid approach to improved interpolation method • Minimize error method • Use all 271 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   end do end do

  5. Holland et al. (2010) Update • Assume no error in H*Wind Analysis • Can write H*Wind Analysis in terms of Holland et al. interpolated and error function: H*Wind Anal.(q, d) = Holland Interp.(q, d) + Interp. Error (q, d) • Hypothesis we are testing: -There are systematic errors in the interpolated error over 271 analysis times -Develop error function E(q,d) to model these errors to improve interpolation method • If this works: • Develop TCMTool that creates Holland et al. interpolated wind field • Add error function to this interpolated wind field for initial wind field

  6. Gust Factor as Function of Analysis Time Interval • Motivation • Working through the literature review for the introduction to the climatology paper • Gust factor analyses based on different averaging times

  7. Gust Factor as Function of Averaging Time (From CIMMSE Blog Post, Jonathan Blaes, August 2012)

  8. Gust Factor as Function of Averaging Time • Durst (1960) • Purpose: Provide method for calculating wind gust value over t=t0 interval of time based on average wind speed calculated over t=t1 interval of time • Helps to standardize wind gust factors based on averaging time and wind gust observed time interval

  9. (Krayer and Marshall 1992) (Analysis based on Durst 1960)

  10. Wind Gust Forecast Discussion • The various studies show significantly different gust factor based on the averaging time and the time interval for which the gust is expected to occur • Should we standardize what time interval the gust is forecasted to occur? • Get all local WFOs on same page, if they are not already?

  11. Wind Gust Forecast Discussion • Current TCMWindGust tool uses regression—regression based on 2 minute wind speed average/5 second peak gust • Sustained wind speed based on 1 hour average, 2 sec gust—should this be the standard? (CSTAR Analysis 2012)

  12. Suggestion for Regression Equation σ(1 hr, t seconds) = (Durst 1960) We can substitute in this equation to find σ(1 hr, 5 seconds) = (σ(1 hr, 2 min)/M1hr2 + σ(2 min, 5 sec)/M2min2) 1/2 (Term 1) (Term 2) Then GFGiven Hourly Wind Speed = 1 + Z* σ(1 hr, 5 second)Given Hourly Wind Speed where Z = 2.98

  13. Focuses Next Month • Finish climatology paper, hopefully get to collaborators for review • Work to modify regression curve for TCMWindGust tool? • Continuing working with Anantha on Holland et al. (2010) or other interpolation method • WRF-LES simulation for Irene (2011) • Next conference call: Wednesday, March 13th, 11:00 AM

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