Wave Formation
The great majority of large breakers one observes on a beach result from distant winds. Five factors influence the formation of wind waves:
- Wind speed
- Distance of open water that the wind has blown over (called the fetch)
- Width of area affected by fetch
- Time duration the wind has blown over a given area
- Water depth
All of these factors work together to determine the size of wind waves. The greater each of the variables, the larger the waves. Waves are characterized by:
- Wave height (from trough to crest)
- Wavelength (from crest to crest)
- Wave period (time interval between arrival of consecutive crests at a stationary point)
- Wave propagation direction
Waves in a given area typically have a range of heights. For weather reporting and for scientific analysis of wind wave statistics, their characteristic height over a period of time is usually expressed as significant wave height. This figure represents an average height of the highest one-third of the waves in a given time period (usually chosen somewhere in the range from 20 minutes to twelve hours), or in a specific wave or storm system. The significant wave height is also the value a "trained observer" (e.g. from a ship's crew) would estimate from visual observation of a sea state. Given the variability of wave height, the largest individual waves are likely to be somewhat less than twice the reported significant wave height for a particular day or storm.
Read more about this topic: Wind Wave
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