Occurrence of rogue sea states and consequences for marine structures

The frequency of occurrence of combined wave systems like wind sea and swell may increase in some ocean areas due to the observed change of storm tracks. These combined sea states, when crossing at a particular angle, may lead to more frequent occurrence of rogue events. The present study addresses these rogue-wave-prone sea states and their probabilities of occurrence. The analysis is based on hindcast data from the North Atlantic, the North Sea, the Norwegian Sea, Nigeria and Australia and supported by numerical simulations performed by the Higher Order Spectral Method (HOSM, West et al. J Geophys Res 92:11803-11824, 1987). The hindcast data have been generated by the wave model WAM. Long-term probabilistic description of significant wave height and spectral peak period is established for the selected locations and probability of occurrence of crossing rogue-wave-prone sea states is indicated. Further, the occurrence of individual rogue waves in low, intermediate and high sea states is also evaluated. The results are discussed from the perspective of design and operations of ships and offshore structures.