The prediction of critical loads and responses from green sea on FPSOs in random storm waves is described. Physical mechanisms leading to water on deck and bow flare slamming, and the resulting responses, are analysed. A numerical engineering software tool, WaveLand, is reviewed. Critical inflow parameters predicted by this tool are addressed, in order to identify events in a 3-hours storm for subsequent detailed modelling. In particular, the incident wave particle velocity and the relative height above deck are considered. Model test data from two tests with a turret moored FPSO in steep storm sea states are used to demonstrate the role of these parameters in events leading to impact loads on deckhouse and bow flare. A comparison to VoF-based CFD simulations of a water-on-deck event is also shown The water propagation on a forecastle deck, as well as the resulting impact load on a deck house, shows promising comparisons to model test data and to WaveLand simulations.