In his book on surfing as spiritual quest (West of Jesus) , Steve Kotler says that "waves are wind." Like Kotler's interesting but sometimes tedious tome on surfing, science and the origin of belief (mythology and science really, he should have titled his book, West of Einstein), Steve doesn't go far enough. Because while wave energy is converted wind energy, wind itself, remembering back to my Meteorology 101 class at Cabrillo College, is caused by uneven heating of the earth's surface. And this involves far greater dynamics that cover vast geographic areas. (For a basic primer on the weather click on the Synoptic Meteorology link.)
This uneven heating of the earth's surface, the origin of wind, causes differences in pressure to occur, especially when air warms over land masses creating high pressure, which can then be filled by high seeking, low pressure areas. Weather is unique also to the geographic area in which we live. While there are strong similarities about the weather on the west coast of the Monterey Bay or North San Diego County, different weather patterns are established according to global locations, including ocean currents and local geography.
One of the most pervasive weather features we experience on the west coast is known as the "marine layer." this weather phenomenon occurs mostly in summer and all along the California coast. Known as "June Gloom" by many, our marine layer or inversion is caused by warm air placing a lid on cooler moist air which then condenses into fog. How long the fog stays around each day is dependent again upon much larger scale weather patterns that are transiting through our geographical area. The marine layer pattern is prevalent in NorCal and SoCal even though the air temperature and water temperatures are appreciably higher in Southern Cali.
So what does all this have to do with the waves (talk about tedious)? In the summer the general conditions that create the marine layer also have a lot to do with creating the kinds of waves that are predominant in the summer (especially in NorCal) and that is "local wind swell". Because of our geographical positioning in NorCal (the way the lands faces the ocean) we rarely receive the benefits of a south swell like they do in SoCal. Therefore, if it wasn't for wind swell we'd have no swell. (More on south swells later.)
Winds are generated when high pressure areas seek to flow into low pressure areas. During the summer instead of the low pressure winter storms that roll across the North Pacific, vast areas of high pressure transit the north eastern Pacific. At the same time huge areas of low pressure are formed over the land mass areas of Utah and Colorado to name two states that are involved in this general pattern. Winds then blow from north to south down the Cali coast, and inland from ocean to land creating "downslope" wind swell and onshore wind conditions. How can we tell when this is happening, other than looking out the window or when standing at the beach? Here's a couple websites to check out: The National Weather Service is always a good source of information, especially the Forecast Discussion links for your area. And Surf Storm has assembled one of the best collections of satellite maps for just about every condition one could think of in the "models" section. Not only can you see the large areas of high and low pressure but you can call up maps that show wind speeds and direction as well as wave size and direction.
Something of the opposite is true in winter when NorCal tends to get bigger and better and more sustained swells than our surfing brothers and sisters down south. Generally, the same meteorological processes are responsible for this, but in reverse. Large low pressure storms roll across the north pacific creating strong wind energy (remember waves are wind?) that converts to waves which often times are headed right at us. In the south what are often good swells for us northerners can be blocked by geographical formations (islands) or even coastlines that don't face into the swells.
But wait, you say, it doesn't matter if we're talking about local wind swell, or big storms in the Pacific, it's winds that create the waves! And you'd be right. but without all those other planetary features working all at once, there would be no wind, and no waves.
Surfing is more than just riding waves, it is also knowing your mother. Mother Nature that is.
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