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The Stages of Wind Waves

In 1933, the USS Ramapo reported a wave in the Pacific Ocean that towered at a height of over 100 feet. When air moves across a smooth body of water, the tension between the two surfaces creates waves. As the water's surface develops ripples, the friction between the water and wind increases, and the waves become more intense. On rare occasions, wind waves can combine, forming extreme storm waves like the one that the sailors of the USS Ramapo saw.

Stage One: Sea Waves
- Wind waves in their first stage of development are called sea waves. They are choppy and irregular in appearance, and often produce white caps and spray. Sea waves are still located at the area of generation, and they tend to travel in roughly the same direction as the wind. Eventually, sea waves outrun the storm that created them, and develop into swell waves.
Stage Two: Swell Waves
- In the second stage of wind wave development, the waves move out of the area where they were generated and take on a smoother shape than the choppy sea waves. These rounded waves are called swell waves, and they no longer have the white caps or spray that characterize sea waves. Swells begin to loose energy when they leave the wave-generation area, but they can still travel up to thousands of miles when they occur in open ocean waters.
Wave Height and Length
- Three factors determine the size of wind waves: wind strength, wind duration and fetch. Wind waves draw their energy from the motion of the air and for the waves to gain energy and increase in size, the wind must be moving faster than the waves. Wind duration refers to the time during which the wind blows --- even a very strong wind won't generate large waves if it only blows for a short period of time. The final variable that determines wind wave size is fetch, or the distance the wind travels without changing direction. For example, a storm in the Pacific Ocean can generate larger waves than a storm of the same size in other oceans because the Pacific Ocean has larger stretches of uninterrupted open water.
Extreme Storm Waves
- Extreme storm waves --- which sailors sometimes call rogue waves, freak waves, killer waves or three sisters --- are large waves that occur with sets of much smaller waves. They typically form when swells that are traveling in the same direction combine, forming steep waves with deep troughs. Extreme storm waves can be unpredictable, according to the National Weather Service, traveling against the wind and other waves and appearing as walls of water, more than twice the size of surrounding waves.

Nature