Wave propagation

Wind causes tiny ripples on the water. Once the water is rippled, it adds more surface area with which the wind can move more water and grow larger waves. This phenomenon is referred to as wave propagation. Wave propagation is limited by Fetch, the distance the waves travel; wind strength; and wind duration, the length of time the wind blows at its full speed.

For example, a 10 knot (18.5 kph) wind blowing over a 10 nm (18.5 km) fetch for 3 hours in an afternoon can create [fully developed]] (height = 1/7 wavelength) 1' (30 cm) waves.

A 25 kt (46.3 kph) wind blowing over that same 10 nm (18.5 km) fetch for 3 hours could easily build 3' (0.9m) waves, but they won't be fully developed because they have insufficient fetch or duration to grow.

Letting that 25 kt (46.3 kph) wind blow over 160 nm (296 km) of fetch will allow those waves to be fully developed at 9' (2.7m), if wind duration is 16 hours.

See accompanying table under Fully developed.