Saturday, April 12, 2008

Random SW Swell Alert – The South Pacific is heating up!

We have a new storm setting up an overhead+ SW swell for Baja, Mainland Mexico, and Northern Central America. (After it smacks Tahiti along the way naturally). The same storm will be sending a smaller, but still healthy, version of the SW swell to Hawaii and California.

(if you just want the swell details…skip this next part…seriously if you don’t you will just get pissed at my rambling)

After a couple week hiatus it looks like the South Pacific is finally starting to get its act together. It has been a slow couple of weeks so it will be nice to have some more juice showing out in the line-up. This last gap between storms (translation total lack of significant Southern Hemi swell) that we have just had is actually fairly normal for the SPAC.

When you look at the big picture you start to see that most of the storm/wind/wave energy in the Southern Ocean (the band of ocean that circulates around Antarctica) moves in a west-to-east pattern…forecasters generally refer to this a “zonal flow”. Unfortunately we need a storm that breaks out of the zonal pattern, trying to change its latitude, and in the process sets up fetch that is aimed toward our regions. This happens quite a bit but not always in a location that is ideal for sending us surf (like on the other side of Australia, or up next to South America).

A sort of dumb analogy for the process is to picture the South Pacific as a pot of boiling water with the storms being the bubbles that boil to the surface…but only way cooler because when a bubble forms in the right spot it sends us a good swell.

Anyway there are a couple of triggers that cause these “bubble” storms to form…and they almost always involve some sort of energy transfer from a warm-weather area to a cold-weather area. A particularly violent example of this is when you get warm tropical moisture that moves into the cooler upper-latitudes. This process is generally called a tropical based storm (or air-mass) going “extra-tropical”. I could totally bore you with the physics behind latent-heat energy in water…but then my brain would hurt all weekend…so just trust me when I say that there is a lot of energy in tropical moisture…and as the air-mass carrying it cools that energy needs to go somewhere. And it does…usually in the form of strong winds in a bad-ass storm.

I can already hear you out there…”gee Adam that is great but tell us about the swell already weather-nerd!”

Hahaha…jerks. I actually wanted to bring the process to your attention because it is just this “extra-tropical” process that is setting up this next swell.

Here I made a cool chart!

On the chart you can actually see two low-pressures. One is a tropical system and the other a colder mid-latitude low. If you follow the numbers you see the tropical system take a slow dive towards Antarctica…and in the process it expels a ton of energy as it cools. This energy tries to spread out but instead is gathered in by the following storm system.

By slide #5 the cold storm, which is moving in a great direction for all of our surf spots, has jumped in intensity, likely it would have had about 30-40 knots of wind in the core but now, thanks to being jumpstarted by the extra-tropical system, it is seeing winds closer to 60-65 knots (which is the lower end of the wind speeds in the CAT1 Hurricane category). Basically the storm has jumped from being an average to below average swell maker to a good-swell producer.

To cap it off the cold storm continues to push the good area of fetch into the lower latitudes and sort of seals the deal on the swell energy heading towards Mainland Mexico. Anyway…just thought I would share some of the mechanics behind this next swell.

OK Finally the swell details (the hungover may continue reading now)

Mainland Mexico and Northern Central America – There is actually plenty of smaller swells sending in surf to this region right now. So if you are down there or planning on going down there you will have some fun-sized overhead surf while you are waiting for the bigger SW’er to arrive. This swell that I was just talking about will actually start to arrive with long-period energy on the 19th and then peak on the 20-21st. Most breaks will build into the shoulder-overhead+ range with sets going 2-3’ overhead+ at times. Deepwater breaks will be closer to double-overhead on the big sets.

Baja Sur Mexico – The SW swell (210-220) is actually pretty westerly in swell angle so it hits Baja Sur about the same time it moves into Mainland Mex. Most pacific side spots will see this swell start to hit later on the 19th…but it really fills in more on the 20th and eventually peaks into the 21st. Look for lots of shoulder-head high waves at the well exposed areas. Standout spots will have some bigger sets...but expect some inconsistency at times.

Southern California – The SW swell moves in on the 20th, actually following a small playful one that hits around the 17-18th. This new bigger SW’er (200-220) ends up peaking on the 21st and into the 22nd. Due to a little shadowing from the South Pacific it won’t be as big or consistent as the other regions. We can still expect the average breaks to be around waist-shoulder high. Standout spots, mostly in North San Diego and Southern Orange County, will have some bigger head high+ sets at times.

Hawaii – There is a good portion of fetch heading toward the islands…so we will actually see decent sized S swell arrive on the South Shores around the 16th…and eventually peaking on the 17-18th. This one looks good for shoulder-overhead faces with sets going 1-2’+ overhead as the swell peaks at the top breaks.

As usual I will give some updates on this swell as it gets closer…particularly if size or timing needs adjusting…so check back for more details.

No comments: