Understanding Wave Height, Swell height and Fetch.

Discussion in 'All Things Boats & Boating' started by oceancruiser, Jan 23, 2014.

  1. oceancruiser

    oceancruiser Previous Member

    Last edited: Jan 25, 2014
  2. jehardiman
    Joined: Aug 2004
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    jehardiman Senior Member

    Fetch is the minimum distance that the wind of a set speed must blow over in order to build a seaway of a given height and period. You are never going to get large, long period waves on a small pond no matter how hard or long the wind blows. Conversely in the Southern Ocean, the fetch is effectively endless and waves of huge height and long period (length) are generated even in modest breezes.

    So, wind waves are generated by the local wind blowing over its rerquired fetch. Swell is caused by remote winds blowing over its fetch, and then the waves leave that area and travel to the local area.

    FWIW, if I am interested in swell in the Southern Califorinia Bight, I look at storms off New Zealand 2-3 days before. That is where my swell will be generated, and I can track that swell across the Pacific on the Ocean Buoy Data Center.
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