A review of the sea state generated by hurricanes

Data from four studies of waves generated by hurricanes are reviewed and compared. The combined dataset presents a consistent picture of the wave field within a hurricane. The wave field is more asymmetric than the corresponding wind field, mainly due to the "extended fetch" which exists to the right of a translating hurricane. This concept leads to the specification of an equivalent fetch for a hurricane which enables the use of fetch limited growth relations for the prediction of the significant wave height within a hurricane. Examination of spectra recorded within hurricanes indicates that they are remarkably similar to fetch limited forms. Relationships for the parameters defining fetch limited spectra are found to also be valid for hurricane conditions. The reason for the similarity of hurricane and fetch limited spectra is attributed to the shape stabilizing effect of non-linear wave-wave interactions, which continually reshape the spectrum to conform to the standard JONSWAP-like form. Although the wind speeds within hurricanes are very high, the spectra generated are mature, with values of non-dimensional peak frequency typical of fully-developed seas. The analysis develops a set of standard relationships which can be used to define the wave field and spectral form for use in design of offshore fixed and floating structures.