What are Swell waves?

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What are Swell waves? Blog Image


Recently, swell waves inundated coastal areas in central and southern districts of Kerala.

About Swell Waves

  • A swell is the formation of long wavelength waves on the surface of the seas. These are composed of a series of surface gravity waves.


  • They occur not due to the local winds, but rather due to distant storms like hurricanes, or even long periods of fierce gale winds.
  • During such storms, huge energy transfer takes place from the air into the water, leading to the formation of very high waves. Such waves can travel thousands of kilometres from the storm centre until they strike shore.


  • Swells have a narrower range of frequencies and directions than locally generated wind waves, because swell waves have dispersed from their generation area, have dissipated and therefore lost an amount of randomness, taking on a more defined shape and direction.
  • These waves can propagate in directions that differ from the direction of the wind, in contrast to a wind sea.
  • Their wavelengths may rarely exceed more than 150 m. Swell wavelength, also, varies from event to event. Occasionally, swells which are longer than 700 m occur as a result of the most severe storms.
  • It occurs without precursors or any kind of local wind activity and as a result.

In India early warning systems like the Swell Surge Forecast System launched by the Indian National Centre for Ocean InformationServices (INCOIS) in 2020 — gives forewaring seven days in advance.

Q1: What is the mandate of Indian National Centre for Ocean Information Services?

It is to provide the best possible ocean information and advisory services to society, industry, government agencies and the scientific community through sustained ocean observations and constant improvements through systematic and focused research.

Source: Swell waves inundate coastal areas in southern, central Kerala