Rogue waves off the south/southeastern Brazilian coast

The occurrence of freak waves off the Brazilian coast was investigated through the analysis of data recorded by three buoys deployed in the south/southeast region, at a depth of 200 m. As well documented in the literature, these events are not rare, and more than 700 waves could be classified as abnormal based on the relation between the maximum wave height (H max) and the significant wave height (H s), H max ≥ 2H s. The use of other parameters suggested in the literature, as crest amplification index (crest height/H s ≥ 1.3) or a lower limit to the significant wave (H s ≥ 2 m), drastically reduced this number, resulting in a data set more representative of rogue waves. After applying these more strict criteria, only seven “true” freak waves were found. For the first time in Brazilian waters, it was possible to identify two freak waves in the same record. It was also investigated that an index analog to crest amplification, the trough amplification index (trough depth/H s), and several waves satisfied this new condition. The analyses of the asymmetry and directional spreading of measured spectra reveal no significant correlations between these parameters and freak waves. Probably due to the relative low energy of the area when compared to other regions, the longest wave period closer to a breaking condition is 10 s.