A Note on Short-term Wave Height Statistics

Short-term wave height distributions in intermediate water depthshave been investigated using spectral wave data from two gauges near Galveston (on the northern side of the Gulf of Mexico) and NDBC buoy 42035 during Hurricane Ike. Frequently used distributions such as the Rayleigh, the scaled Rayleigh and the 2-parameter Weibull distributionsare compared. The analysis of wave heights suggest a good fit to the scaled Rayleigh distribution. The significant wave heightH1/3 is over-predicted most of the time by Rayleigh distribution by 1% to 9% for the data examined. The average of the highest ten percent the waves,H1/10 was also over-predicted by similar magnitude (< 10%). However, the over-prediction was more pronounced for the maximum wave height Hmax by as much as 40% in some cases. The two-parameter Weibull distribution was observed to provide a good fit, but the parameters of the distribution were not consistent with those developed by Forristal (1978). The analysis using the scaled Rayleigh distribution (which utilizes the spectral width) showed a better prediction than the original Rayleigh distribution, but with a high variability.These results will impact the estimation of the largest waves based on simple parameters like the significant wave height obtained from numerical modelling.