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INCOIS Issues Red Alert for Kerala Coast Over Potential Swell Waves
The Indian National Centre for Ocean Information Services (INCOIS) issues a Red Alert across all coastal districts in Keralam over dangerous sea conditions caused by potential swell waves. The alert warns residents and authorities, and the news highlights India’s swell wave early warning and forecast system.
Swell Waves:
| Dimension | Key Details |
|---|---|
| Definition | Swell waves are long-wavelength ocean waves formed on the surface of the seas and travel away from their places of origin. |
| Wave type | Swell waves comprise a series of surface gravity waves. |
| Indian term | Swell waves are also called Kallakkadal waves in India, which is a colloquial term used by Keralam fishermen. |
| Organisation and propagation | Swell waves organise themselves into groups of similar heights and periods, and then travel long distances without much change. |
| Early warning system | INCOIS Swell Surge Forecast System has been launched in 2020 and gives forewarning 7 days in advance. |
| Formation | Swell waves are usually created by windstorms or other weather systems. |
| Energy transfer mechanism | Windstorms and other powerful air current systems transfer energy from the air to water, making swell waves more powerful than locally generated waves. |
| Storm-linked high waves | During storms, huge energy transfer takes place from the air into the water, leading to the formation of very high waves. |
| Travel distance | Swell waves can travel thousands of kilometres from the storm centre until they strike shore. |
| Cause not local winds | Swell waves occur not due to local winds, but due to distant storms like hurricanes, or long periods of fierce gale winds. |
| Frequency and direction range | Swells have a narrower range of frequencies and directions than locally generated wind waves. |
| Reason for defined shape | 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. |
| Direction vs wind | Swell waves can propagate in directions that differ from the direction of the wind, in contrast to a wind sea. |
| Wavelength limits | Swell wavelengths may rarely exceed more than 150 m, and occasionally swells longer than 700 m occur as a result of the most severe storms. |
| Precursors | Swell waves occur without precursors or any kind of local wind activity. |