As mentioned in the article on swell generation - wind creates waves. The size of those waves will depend on three things, the strength of the wind, how long it blows for and the 'fetch'. Literally the distance of ocean over which the wind is blowing. The greater the area a storm covers the larger the waves created will be (assuming the strength or duration don't limit the size). This is of critical importance to surfers in areas of limited fetch. There are many areas regularly surfed that are marked by the limited distances swells have to fully develop - the great lakes, the English Channel and many surfable areas of the Mediteranean are good examples. Understanding the importance of fetch can be crucial in spoting swell generating winds in these areas. In this kind of situation a variation in the wind direction from, for example, south to south-west might mean that the area of sea over which the wind was able to blow was increased by enough distance to make the difference between totally unsurfable low period slop and a workable wave.
In areas of coast exposed to large areas of open ocean the concept of fetch is equally important. A small local storm, even powerful, will generate limited waves compared to a deep low pressure spanning a larger area. The exception would be a smaller system travelling over a large distance following the waves it creates - see the article on virtual fetch. |
