Synchronized pitching is when the period of the vessel pitching, equals the period of encounter of the waves from either ahead or astern. It must be considered extremely dangerous especially if in an area of abnormal waves. It can be overcome by reducing the ship’s speed and changing the period of encounter.
Synchronized rolling is when the roll period of the vessel equals the period of encounter of the waves. This is considered a highly dangerous condition and should be destroyed immediately by altering the vessels course.