Statistical analysis of freak waves characteristics under tropical cyclone influence in open ocean conditions

Freak waves have caused extensive damage to offshore structures due to their destructive power and inherent unpredictability. Using the wave data obtained from the central South China Sea, the freak wave statistical characteristics and the influence of tropical cyclones on these statistics are examined. Particular attention is given to the occurrence probability of freak waves and the effect of the tropical cyclone factor. Wave trains with high Benjamin-Feir Index (BFI) and wave groupiness factor (GF) occur mainly under strong wind and extreme wind conditions. As the cyclone-intensity factor I (quantified by the ratio of the station wind speed to the maximum wind speed near the cyclone center) increases, the BFI and GF increase, whereas the skewness decreases correspondingly. The freak wave occurrence probability is positively correlated with kurtosis and the GF, and is higher than the predictions of classical models such as Rayleigh and Mori. The Mori and GC models provide reasonable predictions of freak wave heights, whereas the GC-CR crest distribution model performs better than the Rayleigh model in predicting extreme crest elevations. The results elucidate the modulatory role of tropical cyclones in wave evolution and provide a practical engineering framework for freak wave prediction under tropical cyclone conditions.