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wave speed The speed of the crest of a wave as it moves along the medium that is waving. Wave speed applies to waves in strings, in the air and in the water. This speed is determined by the wavelength of the wave from: wave speed (knots) = 1.33 square root of the wavelength in feet. For any given wind speed, there are many different waves heights and lengths, and consequently many wave speeds present at all times. As a rule, when waves are first formed they move very slowly, with the speed increasing with time up to some practical limit, which for fully developed wind waves is about 0.7 to 0.9 times the wind speed. For a steady 20-knot wind blowing for at least a day over open water, the average wave speed will be about 16 knots. Awareness of wave speed is often crucial to boat handling in big seas. Remember all aspects of waves are statistical, so we are referring here to an average or most probable wave speed. See G226 to compute the actual distribution or at least some approximation to it. Wave speed versus water depth is shown in G441. Wave speed in general is discussed in ART-18.

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