Swell - How Wave Direction and Size can Affect the Surf.

Swell

Usually surfers starting out look at size and maybe direction, neglecting wave period

That wave period also effects how much wrap gets into sheltered spots. The longer wave periods wrap in more than the short period swells. So if the NW is short period junk I don't waste my time looking at the Half Moon Bay Jetty. Tools like the ones offered at Surfline due a pretty good job of illustrating this but I have found that they are best as a general illustration. The nitty gritty of how the swell effects different spots comes with experience.

The Half Moon Bay Jetty is a good example of wave diffraction (the wrapping in of waves) because you can surf the Jetty at 6ft when Mavericks is 40 ft. The big long period NW swell gets cut down to something more manageable to the rest of us. It would due the same at some south facing spots at Santa Cruz, as well as Doran Beach in Bodega Bay and Drakes Beach in Point Reyes.

I have found that although the low period waves are junkier they can be quite fun if the local wind conditions cooperate, with no wind or offshore wind. Ocean Beach can be really nice with offshore wind and small windswell. Some spots will close out less than they normally would because of the softers shoulders on those waves.

The direction also effects the wave conditions, even after accounting for how if affects size vs direction. Sometimes that long wave period can come in just closeout when it hits directly. For example, W swell at a W facing beach. This is especially true if the sandbars suck like they usually due at Sharp Park. But if the wave period drops, and the size drops, and the tide drops.......

Obviously the possibilities are endless but it's nice to a solid grip on the major factors so you start to plan in advance what direction to start driving.

California Swell Sources:

The North Pacific – These are where California's northwest and west swells of medium to long wave periods originate from. Storm activity in the North Pacific generates swells from November to March, with December to February as peak season. The larger size and longer wave periods of some of these swells can mean pretty good wrap for south and southwest facing beaches. In fact, other than spots like Mavericks than can handle massive swells, many of us in California will flee to the southish facing beaches to surf something a little more “manageable”.

The South Pacific – Originating in the Southern Hemisphere, these south to southwest swells hit California between March and October. Late spring is peak season. The huge distance these swells travel mean several things. They have the longest wave periods, up to about 22 seconds. They are also smaller and less consistent than the west and northwest swells. I have been skunked many times when a smaller south swell just didn't show up, perhaps diminished by opposing winds during the journey here.

Local Windswell – Short period windswells are generated within a few hundred miles off the coast. The strongest windswells occur between November and May, with peak windswell season between March and April. Usually these swells approach from northwest to west. The short periods of these swells mean very little wrap will find it's way into the south to southwest facing beaches. Beaches than can handle sloppier surf hand be really fun on windswells.

The Tropics – Tropical storms and hurricanes off of Mexico will generate this swell. This occurs between June and October. The swells are short to medium wave periods and approach from a steep southeast to south direction. They are more of a wave generator for Southern California than Central or Northern California.

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