Saturday, September 12, 2009

Random Swell Update – New NW swell is filling in nicely

So I was looking through the buoys this evening (I know, I know I should probably get this case of “forecast OCD” looked at) and I am seeing the new NW swell (290-300) showing some decent size.

Check out the San Nicolas island buoy, which is sort of an outer buoy for Socal in the sense that it is more exposed to swells in the open ocean with less shadowing from Point Conception and the Nearshore Islands.



We won’t see all of this energy along our beaches but it is nice to see a good sized lump (considering that it is early/mid September) moving though our nearby stretch of ocean. I even think that I am going to add a little more size to the forecast tomorrow.


Nice to see some green on the chart!

So for Sunday…we can expect this NW swell (290-300) to mix with some background tropical SW swell (190-215) and some steady local windswell. Average W-NW facing spots are going to be in the chest-shoulder high range on sets. Standout NW facing breaks, particularly in Ventura, the South Bay, a few breaks in North OC, and most of the winter breaks in San Diego (biggest in the South County), will be more consistently in the chest-head high range, maybe even a few bigger sets mixing in at the top spots on the right tides.

If the periods were a bit longer I might have added more size to the surf tomorrow but as it is I think that it will still be plenty fun…and fairly consistent with punchy workable waves at the best exposed areas.

Winds still look a tad dicey tomorrow, not victory at sea or anything, but some onshore flow/texture at the more open spots…sort of westerly through SB down through North LA, variable through the South Bay, and sort of S-SW for OC and San Diego. It will still be rideable even with the bump/texture…but don’t expect perfect conditions. Have a good one…hopefully the update will help you grab a few tomorrow.

16 comments:

Anonymous said...

damn south winds!!!!!

Anonymous said...

pretty junky

Anonymous said...

adam, question..
if this swell is 290 - 300+ why does the san pedro say 270? its showing as of 11:29 a.m. 4.9' @ 15 272 deg true.

thanks

Anonymous said...

pechanga!!!

namotuman said...

farking south winds!! really junked up so. county. won't be so much an advantage for those early morning heats at the hurley......

Anonymous said...

AW,
what's your take on the el nino
for late season tropical, s hemi and n pac winter swells, can you do a post when you are bored or something?
thanks brotherman,
Coconutz!

Adam Wright said...

There are a couple of reasons why the San Pedro buoy sometimes shows wonky data…but the main one is just its location. Check it out…copy and paste these coordinates into Google Maps …

33 37.07 N 118 19.02 W
(33.6178 -118.3170)

It will give you a marker roughly located where the buoy is moored.

Now scale the map back so that you can see all of Southern California, and make sure that it is “satellite view” so that you can see the undersea contours of the ocean floor.

The San Pedro buoy is almost completely shadowed from any NW energy above 300 degrees…by a combination of the Channel Islands and Point Conception. Because of this shadowing on NW swells (290 and above) it almost exclusively shows energy that is being wrapped in by refraction occurring in deep water.

What happens is that NW swells (285-295) with a long enough swell-period (16-17 seconds or higher) will start to feel some of the shallower areas around the Southern California Bight, in this case it is the edge of the shelf that extends westward from San Miguel Island. The shallow waters bend the swell off its original swell angle and wrap it around into the more open areas to the South of the Channel Islands. The swell will actually start to bend even more to a westerly direction as it passes under Santa Rosa Island, (and thanks to another shallower shelf), after which it finally moves back into deeper water. Check out the CDIP's larger scale model of the San Pedro channel...you can see how the swell is wrapping in from the deeper water.

http://cdip.ucsd.edu/?nav=recent&sub=nowcast&units=metric&tz=UTC&pub=public&map_stati=1,2,3&xitem=spc

By the time that the swell is heading towards the San Pedro buoy it has been bent around to about a 270-280 degree swell angle, which is the main reason that buoy always seems to show a more westerly angle on the steeper NW swells. You will occasionally get some scatter energy mixing in from energy refracting around the Anacapa side of the Channel Islands…but it isn’t really wave-making swell…just some random hiccups as the swell sloshes around in the Bight.

The second reason that the buoy output seems skewed is due to the way that the CDIP and Scripps present the buoy data. The particular graph that most of us look at…

http://www.lajollasurf.org/sanpedro.html

…has a couple of weakness/quirks that crop up when you have multiple swell sources in the water. Basically if you have two similar sized swells with similar swell periods, but coming from different directions, the buoy graph will “average” those 2 directions to something in the middle. For example if you have a W swell (270) and a S swell (180) the “dominant direction” on the graph would be SW (225), which wouldn’t even be a swell-direction that we have in the mix, and if you tried to score surf on the 225-degrees, you might even miss the swell altogether.

I go over a lot of that buoy stuff in my “how to use the buoys” blog post I did a while back. Check it out when you get a chance

http://socalforecast.blogspot.com/2008/04/ocean-science-101-how-to-use-noaa-and.html

When you get right down to it…it is important to use the buoy network as a “whole” and not base decisions off of just one particular buoy. I like to look at almost all of them in a single check, using the outer buoys to give a good (but almost overexposed) picture of what the true-swell angles…and then back up those observations with the nearshore buoys that help paint a clearer picture of how much of that energy is making it to the beach.

Hope this helps…

Cheers!

Adam

Adam Wright said...

Coco - that is a good idea...I will put something together, probably over the next week or something. (I am finally going to get some quality time to spend on the site...thanks in no small part to all of you guys that visit the ads/sponsors and/or have donated to the tip jar). I am hoping to start rolling out a lot of new content before too long. Anyways...thanks for the post suggestion!

Anonymous said...

keep up the good work Adam. U kick ass!

Anonymous said...

thanks a ton adam.... one more quick question if you don't mind. the energy that is being wrapped around the socal bight, is it weaker energy then say swell that is truely coming in from 270? meaning smaller once it arrives vs swell that is truly coming in from the west?

thanks again

Adam Wright said...

Yeah that is exactly right...you start to lose more and more energy as more refraction occurs.

The one thing that can throw the perception of that energy loss off is the actual bathemetry of the surf spot...so even though you might lose energy overall as the swell wraps in, the set up of the break can focus and multiply the effects of the leftover swell...making it seem like the full amout of the swell is hitting.

Anonymous said...

thanks again...... i understand now.....been windering for a long time now...

deckmanx said...

Hey Adam, in that future post for El Nino could you go into what that may mean for other parts of the world? (Peru, Chile, Ecuador, Central America, etc...) I have a trip planned to Peru in January and I'm not sure what a possible El Nino would mean for my trip! Thanks!

Anonymous said...

Just for future forecasting reference...Southbay was WAY overhead and completely walled all weekend. It was big Saturday morning and stayed big until last night.

Kemble2000 said...

Adam, I like the 9-band out on CDIP (though what's online looks different than what you posted...I assume you manipulated it a bit?). Anyways...for the Ventura county coast, do you see Harvest as the best bouy to watch?

Anonymous said...

Unreal info, wow, superb, thanks
Coconutz!