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Surfline forecaster (and potential 4/3mm purchaser) Adam Wright responds:

Hi Dave,

You can blame our serious shrinkage and the cold water temps on all of the gusty spring winds that have been blasting through the past few weeks. The phenomenon is actually called upwelling.

Here's a sort of simplified explanation: (The more complex one would drop us a little to far into ocean physics than my saltwater addled brain is willing to go this morning.)

On a normal windless day, the ocean is constantly receiving heat energy in the form of sunlight. The sun will eventually heat up a top surface layer of water and since like air, warmer water will rise to the top, the warmer temps have a tendency to stay along the surface while colder water remains below.

In some areas of deep ocean this surface layer can be 100+ meters thick with a buffer called the Thermocline separating it from the really butt-cold water beneath, but it sort of thins out as you approach a coastline and weird things like currents get involved.

Anyways, without wind this little package would stay nice and neat, and if you lived in the sub-tropic to the low temperate latitudes you probably wouldn't have to wear much in the way of a wetsuit. But since there is wind, and in the California springtime LOTS of wind, this whole separation thing really falls apart.

Wind blowing over the surface of the water has a tendency to get water molecules moving, in general they will move in a circular motion sort of like a forward somersault along the path of the wind. These surface molecules start interacting with ones below them... and so on... getting deeper as wind intensity picks up. This motion is actually the birthplace of a wind wave but it also acts like a conveyer belt bringing up the cold water beneath the surface layer. This gets worse the stronger the wind gets.

Lately, Southern California has gotten a lot of wind. There have been a few days with WNW'er going 30+ knots in the afternoons. This just dredges up an ton of cold water and serves up all of our ice-cream headaches.

Will you still be wearing your booties in June? I sure hope not. Local winds usually start to settle down in May and June and as they do the surface temps will start to rise -- just keep your fingers crossed that local winds stay on the light side for the next few weeks and we should be able to shed some rubber.