Tragedy has struck again...Bodega Bay

Wow, thanks. I had no idea. Glad I learned this before ending up in a bad situation!

Wow, thanks. I had no idea. Glad I learned this before ending up in a bad situation!

me too, thanks!

RIP. 



& also from a surfing perspective a 10ft @ 10 seconds/windswell wave breaking near shore is usually much less than 10ft in height. Maybe half that. But a 10ft @ 20 seconds/groundswell wave breaking near shore could result in 12-18ft waves. That's my general rule of thumb.

There are plenty of reef breaks all up & down the coast that won't even have any waves breaking at 10ft @ 10 seconds. That's really just big chop.
But as the period goes up past 12-13 seconds then waves start showing up. Some places even break at 2-3ft @ 13 seconds. Beach breaks do have waves even on small windswell due to shallow sand bars.

I remember a couple times it was 20ft @ 25 seconds & I drove around everywhere was closed out including Bolinas, Drakes, & Doran all the way to the jetty. What a waste of gas when I could have been kayak fishing somewhere inland or on the bay.

Appreciate the lesson, I never knew this.

Swell period is more important than size.  Taking out a small boat in 5@10 is a minor hassle.  Taking out a small boat in 5@20 can be dangerous. 

can you expound on this a little?  Relatively new to this and trying to get an understanding of what I'm seeing when I check ocean conditions prior to leaving home.

When I have some free time in the next couple days I'll write up a primer on swell conditions as a new thread.

Swell period is more important than size.  Taking out a small boat in 5@10 is a minor hassle.  Taking out a small boat in 5@20 can be dangerous. 

can you expound on this a little?  Relatively new to this and trying to get an understanding of what I'm seeing when I check ocean conditions prior to leaving home.

When I have some free time in the next couple days I'll write up a primer on swell conditions as a new thread.

Thanks,  the little you did write was very informative, looking forward to that…

  Thanks again,,,

Swell period is more important than size.  Taking out a small boat in 5@10 is a minor hassle.  Taking out a small boat in 5@20 can be dangerous. 

can you expound on this a little?  Relatively new to this and trying to get an understanding of what I'm seeing when I check ocean conditions prior to leaving home.

When I have some free time in the next couple days I'll write up a primer on swell conditions as a new thread.

Thanks, much appreciated!

http://www.surfertoday.com/surfing/6760-how-is-a-wave-formed-understanding-swell-and-surf-forecasts

I guess I've been reading the swell report incorrectly. I always thought that longer the period means calmer water. I fail to understand why 10'@20 is more powerful than 10'@10. If I'm on the water, a 10' swell come by every 10 seconds means I'd bob up and down 6 times per minute. Versus, 10'@20 I'd bob up and down 3 times per minute. Is that thinking wrong? What makes a longer period swell more powerful than a shorter period?

Shorter periods can make the wave faces really steep.  5@10 is fishable.  5@5 is gnarly, you will have waves breaking in your lap.  5@20 is totally fine, just be very aware of rocks and semi-submerged obsticals because big setscome through every ~15-20 minute that push a whole bunch of water.

Lucky13, you are correct about the 10 second vs 20 second frequency. 10 seconds equates to way more bobbing up & down. The difference between groundswell & windswell power wise has to do with breaking waves near shore. The longer period equals a wave that traveled a much greater distance & those waves pack way more power vs shorter period waves that were created locally. Stormsurf is my favorite website for surf forecasts. They are pretty good about nailing the size of waves & in their Quickcast they forecast both the wave size & frequency measured at the offshore buoys & also the predicted wave heights, of actual breaking waves, near shore. Wave height at the buoy & waves actually breaking at the shore are two different things.



http://www.stormsurf.com/page2/forecast/shortcast/ncal.html



See the difference in the "details" vs the "waves" sections of the Quickcast.

What makes a longer period swell more powerful than a shorter period?

Speed and mass.  Windswell is rampy, groundswell is slabby......you probably wouldn't even notice the slabs in deeper water.  If you've ever been diving on a relatively flat day but had a ton of horizontal surge in the shallows, that's a long period groundswell doing its thing.

The longer period equals a wave that traveled a much greater distance & those waves pack way more power vs shorter period waves that were created locally.

I see. It's making more sense now. Thanks Jim!

Thanks crash, Art for the explanation also!

Think in terms of volume.

10' @ 10 seconds has a certain volume of water.

10' @ 20 seconds has WAY more volume.

So when that large volume of water hits the shallows it builds up on itself and can break with extreme power.

A call of 3' @ 17 seconds is known by many to be a very "flat" day, but watch out!  While most places will be flat, some reefs and beaches will have a huge break on such a day - especially south/west facing areas that are protected from the usual north/NW swell and wind.

Thanks Eric. This is going to make me read the forecast in a very different way.