Ocean Waves - Wind and Swell

Ocean surface waves have two basic sources. Wind produces waves moving roughly in the same direction. Higher wind speeds produce higher and longer waves. Wind is described by a direction and a wind speed. There is an option in RenderWorld to have the wind speed and/or direction change with time.

Swell, the other source of waves is generally longer waves that come from a distant location (perhaps leftovers from a far off storm) and have no relation to the local wind. Swell can move in any direction, even upwind. Swell is described by a direction, length of the waves, and a description of how focused or spread out they are (i.e. are they all traveling in exactly the same direction, or do they travel in slightly different directions)?