Understanding Ocean Waves for Surfers

How Waves Are Made

• Waves are created by wind generated from offshore storms. On weather reports, these storms can be identified as low pressure areas. The closer the isobars are on the weather map, the stronger the wind. When wind blows on the ocean's surface, ripples are created. Ripples become waves, whose size depends on the strength of the wind and the length of time it is blowing. Waves will begin as "small chop" -- small waves that cannot be surfed -- but will increase in size as the wind continues. A wave is considered to be fully formed when the largest waves possible have been generated from a particular wind speed.

What Affects Waves

• The size of the swell can be affected by three main things: wind speed, wind duration and fetch (the area over which the wind affects the wave). When the wind stops affecting the wave, it will begin to lose energy. In addition, as the waves travel, the seabed and other obstacles, such as islands, will reduce them. Other factors that affect the size of the waves as they break are the direction of the swell; a possible swell coming straight up from the ocean floor, which will create large barreling wave sets; and the tide, which affects some surf spots more than others.

Swells

• As waves propagate, moving further away from the wind source, they will organize into swell lines, which are called sets. Sets are like wave trains, and a series of waves will hit the beach at the same time.

  Waves with longer periods -- waves that take a long time to pass through any given point -- will have better swell. If you have a local surf spot, be aware of how the swell direction affects this break. In California, most beaches face due west, so a west swell will hit the break straight on and result in clean, consistent waves. A southwest swell will result in a different wave appearance as it hits the beach.

Wave Height and Time

• Internet sites with surfing reports may be able to interpret how the weather will affect a break, but it pays to understand the common surfing terminology, such as swell interval (the time between each wave) and swell height. For example, "3 feet 10 seconds" means the average height of the waves is 3 feet (in surfing feet) and it is 10 seconds between waves. The longer the interval between each wave, the bigger the waves and the better the surfing will be.