Waves

cue

Was in Enniscrone today and the waves were dumpy (I think that is the technical term :rolleyes:) and closing out. Just wondering what causes this? Is it wind or swell or the random moods of the ocean gods?
I spoke to a surf instructor once with an encyclopediac knowledge of different types of waves, like eskimos with snow, and he seemed to base his descriptions on the shape of the sea-bed or reef. I had no idea what he was talking about at the time but am kinda curious now.
Anyone know is there a name for those waves which you paddle like mad for and then they sort of roll under you without any power? Or is that just me? They bug the hell out of me!

Kell

cue wrote: »

Just wondering what causes this? Is it wind or swell or the random moods of the ocean gods?

Was the wind onshore or offshore and where was the swell coming from? I find that waves that just dump in the centre, the wind is generally a reasonably stiff onshore one. Offshore winds give the wave more of a steep face.

As for seabed/reef, couldnt comment.

K-

cue

Wind was cross offshore. It was holding them up fairly steep but then the wave would just all dump together. Not sure about the swell direction but there was a good period between them.
I think the fact that they were so steep contributed to their collapse, but I could be wrong.

Gone West

The reason Enniscrone was falling apart yesterday was probably that the sandy bottom had no shape to it. The shifting sandbars occasionally break down into lots of smaller bars, with waves just breaking over the bottom all over the place. A well-defined sandbar on a beach break will usually hold the waves up better, giving them form, shape and definition.
Just a guess based on yesterday's swell (9-11 foot @ 11 seconds, WNW) and winds (light offshore, swinging to cross off, swinging to light-mod offshore).

spaceHopper

When a wave gets into shallow water the front of the wave starts to slow down, the water at the back over takes the water at the front and it starts to fall over or break.

Take two cases

The change in depth is sudden and uniform, e.g. the wave hits a sandbar at 90 deg to the wave. All of the wave face experiences the same change and breaks at once or "close out".

The change in depth is gradual and occurs smoothly, e.g. the wave hits a sandbar at 70 deg to the wave. Different part of the wave see different depths, the shallowest parts slow down first and start to break or "peel"

cue

Thanks guys. That makes sense.