An investigation of rogue waves using UK coastal data

While several theories regarding the formation of “rogue waves” have been proposed, efforts to validate them using large datasets have discredited some of the mechanisms earlier thought to be prominent. Recently, some data-based theories have been proposed as an alternative. These include analyses based on a) wavelet transform; b) relationship of the rogue wave to various sea-state parameters; and c) the Grassberger Procassia phase space dimension. These theories were investigated using measurements around the UK coast. The results indicate that basic wavelet analyses and the Grassberger Procassia algorithm may not be sufficient for indicating the occurrence of a rogue wave; however, the ratio of the energy during rogue wave formation to the average background energy in the sea state, based on continuous wavelet transforms, does show a correlation to the abnormality index (AI) of the sea-state. Also, the depth-to-wavelength ratio was found to be more informative in this regard, rather than the crest-trough correlation specified by previous research. The probability of rogue wave occurrence (corresponding to an AI greater than 2) is estimated to be about 1.2 × 10⁻⁴ in UK coastal waters, which is somewhat higher than off the coasts of California and Washington in the USA.