Peak factor estimation in hurricane surface winds

The peak factor is a critical parameter in estimating short duration peak gust speeds. An analysis of sixty-four 10 m wind field records measured during the 1999–2008 Atlantic hurricane seasons shows a mildly positive non-Gaussian trend in the skewness of velocity with increasing longitudinal turbulence intensity (Iu). Kurtosis values exhibit slightly platykurtic behavior (kurtosis values less than 3) in open exposure but trend toward Gaussian as Iu increases. Average peak factors are computed from the data, stratified by wind speed and turbulence regime. Gust factor models are also examined; differences between the theoretical and observed zero up-crossing rates and power spectral density functions are used to discuss uncertainty propagation in the model. The results indicate that a non-Gaussian peak factor in theoretical peak gust (or gust factor) calculation appears to be warranted. Additional field measurements in built-up terrain are required to validate this finding.

► Ten years of hurricane surface wind field data are analyzed in this study. ► Observed zero up-crossing rates match theoretical values derived from the von Kármán spectrum. ► Peak (and gust) factors are slightly larger than theory suggests, particularly in built-up terrain. ► The cause is shown to be a mild non-Gaussian trend that increases with turbulence intensity.