What are Swell waves?

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.
• Formation:
  • 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.
• Features:
  • Swells have a narrower range of frequencies and directions than locally generated wind waves, because swell waves have dispersed from their generation area, 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. 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 Information Services (INCOIS) in 2020 — gives forewaring seven days in advance.