A method to assess wind and wave extreme statistics at offshore wind farms exposed to tropical and extratropical cyclones

Abstract. Offshore wind turbines deployed in tropical-cyclone-exposed regions require reliable estimates of extreme wind and wave conditions for structural design. Existing engineering practices often rely on different methodologies for wind and wave assessments, resulting in design conditions that are not physically consistent. Furthermore, the relatively limited duration of observational records with regards to TC occurrence rate introduces substantial uncertainties in the estimation of long-return period extremes. In this study, we investigate how a Monte Carlo framework can be applied for the joint estimation of extreme wind and wave statistics at offshore sites exposed to both tropical cyclones and extratropical cyclones. The methodology combines synthetic tropical cyclones tracks from the STORM database (Bloemendaal et al., 2020) with the parametric wind model from Vinour et al. (2026) and a tropical-cyclone-adapted WAVEWATCH III configuration to generate large ensembles of tropical cyclone-induced wind and wave conditions. A statistical approach is further introduced to account for remotely generated swell systems that coexist with tropical cyclones, while extratropical cyclones contributions are incorporated through annual maxima statistics derived from ERA5 reanalysis. The approach is applied at the NDBC 41002 buoy in the western North Atlantic, where long-term wind and wave observations are available for comparison. Results show that the coupled modeling framework agrees reasonably well with the historical tropical cyclone extreme statistics. The methodology provides physically consistent joint wind–wave conditions that can be directly used to construct environmental contours and identify offshore design points.