Swell

[MikeIH]

I’m new!! Could someone please explain why there are 3 “swells”? Thanks.

[idefix37]

@mikeih

Waves is the sea state (also called total sea) that you can observe in a given place. It is a mix of different waves :
Waves = Wind waves + Swell + Swell 2 + Swell 3
Wind waves (see other layers) is waves generated by the local wind
Swell is the main swell generated by a distant wind. The swell travels great distances to where you observe it.
Swell 2 is a smaller swell generated by a distant wind in another place.
Swell 3 mostly is very small and often neglected.
The difference between Swell 1, Swell 2 and 3 is their significant heights.

What is the interest of knowing these different types of waves?
For Surfers the best conditions are a strong Swell with low Wind waves and low Swell 2/3. With strong Wind waves and strong Swell, waves are very disorganised especially if their directions are different ... "like in a washing machine".
For Sailors, Wind waves at 90º of the Swell direction give a "cross sea" tougher than a sea with all kind of waves in the same direction
...etc...

[idefix37]

@mikeih
In addition here is a theoretical sketch. Hope it helps:

If there is no local wind, waves are only caused by swell. And without swell, waves are generated by the local wind. When there is no local wind and no swell, the sea is flat, of course.

[MikeIH]

@idefix37 many thanks, really appreciate your time. Best Mike