Under which conditions is parametric rolling most likely to occur?

Parametric rolling is a phenomenon that occurs when a ship experiences a unique resonance condition, leading to significant and sometimes dangerous rolling motions. This situation is most likely to occur in head seas when the wavelength of the waves is approximately equal to the length of the ship.

When a ship is navigating head seas, the angle of the waves relative to the ship can cause it to rise and fall in a way that entrains a periodic rolling motion. If the wavelength matches the ship's length, the timing between the ship’s natural rolling frequency and the wave encounter frequency aligns, thereby amplifying the rolling motion. This specific condition can lead to a dangerous situation where the rolling intensifies, potentially reaching excessive angles.

In contrast, the other scenarios presented do not create the necessary conditions for parametric rolling. Calm seas with minimal wave action lack the dynamic interactions required for rolling. Following seas with short wave periods may not induce enough periodic interaction that resonates with the ship's rolling frequency. Heavy winds without waves would not generate the required wave patterns that contribute to parametric rolling, as waves play a critical role in this phenomenon. Thus, the most critical factor for parametric rolling to occur effectively aligns with the scenario where the ship is moving into head seas with wavelengths equal to