Distribution of crest heights in sea states with abnormal waves

To describe the observed crest height distributions, the model of Forristall [Forristall G. Wave crest distributions: Observations and second-order theory. J Phys Oceanogr 2000;30:1931-43] has been applied. Nonlinear effects to second order are taken into account by means of the mean wave steepness and the Ursell number. Although the model is found to be generally adequate for sea states with less severe conditions, the largest crests in the highest sea states, and especially those with abnormal waves present, are permanently underestimated. It could be concluded that the abnormal waves do not conform to the underlying population of waves in the associated sea states.