Context: A low atmospheric pressure that formed in the South Atlantic Ocean on March 23 triggered swell waves, known as ‘Kallakkadal’ locally, along the coast of Kerala, sparking panic along the coastal areas of Thiruvananthapuram, Kollam, Alappuzha and Thrissur districts, according to a statement issued by the Indian National Centre for Ocean Information Services (INCOIS), a Central government agency that issues weather warnings for fishermen in the country.

Swell Waves Cause Panic Along Kerala Coast

• Impact on Coastal Communities: The surging water resulted in pools on some beaches. The fishermen complained of water damaging their fishing equipment. 

• The severity was higher in Thiruvananthapuram, Kollam, Alappuzha and Thrissur.

• Several parts of Kollam coast experienced devastating tidal waves, resulting in significant damage to homes and affecting numerous residents.

• High Wave Alert Warning: Indian National Centre for Ocean Information Services (INCOIS) issued a high wave alert warning people against visiting the beach.

What Are Swell Waves?

• About: A swell wave is the formation of long wavelength waves on the surface of the seas. They propagate along the interface between water and air. 

• Thus, they are often referred to as surface gravity waves. 

• Origin: These are not generated by the immediate local wind, instead by distant weather systems, where wind blows for a duration of time over a fetch of water. 

• Wind-generated waves continue to progress as swell waves even after the wind has ceased or shifted, or the waves have moved away from the wind source.

• Influencing Factors: The speed of the wind, the amount of ocean surface area affected by wind blowing in the same direction (also known as fetch), and the amount of time those winds blow over the same part of the ocean.

Features of Swell Waves

• Narrow range of Frequencies: Swells have a narrower range of frequencies and directions than locally generated wind waves.

• Swells take on a more defined shape and direction and are less random than locally generated wind waves.

• In terms of directionality, they are characterised by the direction from where it emanates instead of where it is headed. 

• Wavelength: Swell waves often have a long wavelength but this varies with the size of the water body. 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.

Indian National Centre for Ocean Information Services (INCOIS)

• Genesis: It was established as an autonomous body in 1999.

• Nodal Ministry: Ministry of Earth Sciences (MoES) and is a unit of the Earth System Science Organisation (ESSO).

• Mandate: To provide ocean data, information and advisory services to society, industry, the government and the scientific community.

What Are Swell Waves?

• About: A swell wave is the formation of long wavelength waves on the surface of the seas. They propagate along the interface between water and air. 

• Thus, they are often referred to as surface gravity waves. 

• Origin: These are not generated by the immediate local wind, instead by distant weather systems, where wind blows for a duration of time over a fetch of water. 

• Wind-generated waves continue to progress as swell waves even after the wind has ceased or shifted, or the waves have moved away from the wind source.

• Influencing Factors: The speed of the wind, the amount of ocean surface area affected by wind blowing in the same direction (also known as fetch), and the amount of time those winds blow over the same part of the ocean.

Features of Swell Waves

• Narrow range of Frequencies: Swells have a narrower range of frequencies and directions than locally generated wind waves.

• Swells take on a more defined shape and direction and are less random than locally generated wind waves.=In terms of directionality, they are characterised by the direction from where it emanates instead of where it is headed. 

• Wavelength: Swell waves often have a long wavelength but this varies with the size of the water body. 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.

• Normal Waves: Any random disturbance that can occur in the sea. Waves can be of any form, type, shape, height, period, direction, and speed.

• Swell Waves: Swell waves are specific kinds of deep-water, linear, long-range wind-driven waves that emanate or filter out of a random wave system during an external weather event due to wave dispersion.

• Swells travel only in a specific direction as more or less uniform, high-speed, long waves that remain constant over time. The speeds, in turn, are a function of the wavelengths and periods. Swells travel much larger distances as compared to any ordinary wave packet. Swells are unaffected by local weather systems.