Friday, May 2, 2008

Random Friday Morning Update – It looks fun. Go Surfing!

That SW’er really filled in overnight and it showing some good sized surf to the exposed areas…and to make it better there is still a decent amount of WNW windswell and background S-SW energy to keep even the shadowed areas in some surf.

Conditions are clean, the surf has decent shape and some punch…and I am seeing a few barrels sneak through at some of the dumpier beach breaks out there.

It is running about chest high everywhere (except maybe Seal Beach and a lot of the far north OC spots). The top breaks that can pull in the mix of SW and WNW energy are hitting head high and head high+ on the bigger sets.

San Diego and South Orange County in particular are seeing a lot of quality surf this morning.

So if you have the time, get some!

Here is a shot of the O-side buoy this morning…lots of long-period SW swell showing on it.


srfnff said...

OK, this is probably kind of a stupid question but comparing your text box comment "More than 2.5 feet of deepwater SW swell..." with the Oside chart which shows Sig.Wave Ht. at 4.1 feet, is Sig. WH a measurement of deepwater swell? If not could you give me a better idea of what you mean, or how you estimate or measure "deepwater" swell?


Adam Wright said...

Ha that was sort of an obscure reference wasn't it?

That summary chart on the O-side buoy is a bit misleading, particularly their idea of significant wave height. On the chart I posted the Significant wave is a measurement that is almost not related to any other data on the chart. (well it is but not in the way that they present the other information). Basically it is a summarized total wave height for all of the swell hitting the buoy. So you might have 3' of w windswell mixing with 2' of long-period S swell to form the significant wave height...make sense?

I always find it more useful (and more relevant) to look at the individual period bands...that way you can isolate a particular swell and gauge its strength.

I generally use the term deepwater swell height to describe the swell when it is still in open water and (mostly) hasn’t been affected by shoaling.

This is usually a better measurement for a surf forecaster because you can get a good read on a swell’s power before it gets influenced by nearshore factors, like swell windows and the local bathymetry. Once you got a feel for the actual size and power of a swell then you start applying those other factors in order to actually predict wave heights at particular breaks.

At an average break 2.5 feet of 18-20 second period swell will about double in breaking wave height as it hits the beach. Top spots will be closer to 2.5x on sets…so for example this swell would hit lowers with consistent 5-6’ faces with the potential for some 7-footers to sneak through as well…which was about how big it was this morning.

srfnff said...

OK, that's good info, especially re the significant wave height. But I still don't understand how you get the "deepwater" reading or data. Is there a source for this 2.5 feet or is it surf forecaster "special knowledge" and wave wizardry? (There must be "open ocean" buoys you check as opposed to buoys closer to shore like the Harvest buoy?) And one last thing (yeah, right!) how "open" is open water? Is a buoy 27 nautical miles from land open ocean or does it have to be like 300 miles out?

I think I know what you mean about checking the period bands in that a two foot swell at 17 seconds will deliver much better surf than a six foot swell at eight seconds.

Sorry for pestering you with all these questions're available (ha-ha). (You can always tell me that I only get one question a month or something...)

Adam Wright said...

On those Scripps buoys there is an interactive feature…so if you mouse over the period bands it will actually give you a wave-height associated with those selected swell periods. So on the o-side buoy you could mouse over the 18+ periods and it was showing the “2.5-feet”…I think it is actually bigger now.

I generally consider anything in about 1000’ of water depth “deepwater”. A 20-second period swell starts feeling the bottom at about that depth…but none of the shorter-periods do. So for me it is more a function of water depth rather than distance from land.

Thing is that because most swells don’t start feeling the sea-floor until much shallower depths you can actually get a pretty good read off the nearshore buoys…you just have to get the feel for how each buoy reacts to different swell periods and swell directions.

Ha…I am totally going to start limiting your questions…(probably not, I like to talk about this stuff so keep the questions coming.)

srfnff said...

Fair enough. No more questions until at least Monday. Even surf forecasters have to have a day off or two. Cool you got to take the baby down to Trestles with you...getting him/her ready for their first surf no doubt.