Accurate sea condition observations are necessary if the forecaster is to be expected to provide accurate sea condition forecasts for operational use. When a breeze comes up, the sea surface will instantaneously become covered with tiny ripples which form more or less regular arcs of long radius.  They increase rapidly in height until they attain a maximum steepness where the pointed crests take on a smooth glassy appearance, indicating small breaking processes.  As the wind continues to blow over the sea, it drags over the surface producing increasingly larger waves.  The wind acts in a manner similar to a paddle rhythmically stroking the water.  There is, however, one difference.  The wind is constantly making small changes in direction and speed.  The result is that the wind is acting like many different paddles stroking the sea in different directions and at different speeds.  This produces many different wave trains in the sea, all with different directions, all with different periods, and all at the same given point in the ocean. If all the different wave trains generated are considered to be sine waves with different heights, directions, and periods., the sum of the heights of the sine waves at a given instant is the mechanism that produces the irregular appearance of The sea.  The various waves which comprise the sea surface are commonly referred to as either sea waves or swell waves.
