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The variety and size of wind-generated waves are controlled by four
principal factors :
(1) Wind velocity) , (2) wind duration , (3) fetch , and (4) original sea
state.
As wind speed increases , so do the wavelength,the period , and the
height of the resulting waves , provided the wind blows long enough
and the area of water over which the wind blows , called the fetch , is
adequate in length.
Also ,waves present before the onset of recent winds , the original sea
state , affect both the wind and the generation of the newly produced
waves. Without « old seas » the sea surface is smooth .
With « old seas » , the sea surface is rough, and this irregular surface
affects how the water and wind interact. Waves will continue to grow
in size until they reach a maximum size that is determined by the
wind speed and fetch. At this stage of wave growth , called a fully
developed sea.
Growth of waves in the fetch area :
The fetch area is where the wind is in contact with the sea and is
rippling its surface . This is the generating area, where waves are
born.
If there is a storm at sea, the fetch coincides with the area of the
ocean affected by the storm winds,where wind transfers energy to the
water surface and raises waves.
As the storm winds increase in strength , the waves grow longer and
higher .
People sailing through the storm would be in the fetch area . There
they would experience the uncomfortable , jerky motion associated
with chaotic waves that impart an irregular , disordered pattern to the
sea surface.
The water motion is turbulent with sea spray , white caps (foaming
wave crests), and even breaking waves (unstable waves that collapse)
.