For navigation safety, ship behaviors in adverse weather conditions must be captured. As a method to know the navigation limit of a ship under external disturbances such as wind and waves, there is a method to capture the maneuvering limit based on the average (steady) sailing conditions (SSCs), such as check helm, forward ship speed (speed drop), and hull drift angle of a ship moving in adverse weather conditions. These are obtained by solving the motion equations for ship maneuvering in steady wind and waves, and related studies have been performed (for instance, Eda, 1968; Ogawa, 1969; Martin, 1980). However, the check helm, hull drift angle, ship speed, etc. fluctuate owing to the effect of random sea. Therefore, to discuss the navigation safety, it may be insufficient to consider only the average condition, and it may be necessary to consider its fluctuation components.