Nature: what is the ocean swell and why is it so dangerous?

12/01/2021

Although it is true that the ocean swell is not as dangerous as a tsunami, it does carry very long and strong waves, which can cause a lot of damage as long as the necessary measures are not taken in time to prevent this phenomenon.

What is the ocean swell?

It is a wave generated by storms at sea, accompanied by strong winds that come from far away from where the waves arrive, this type of event in the Pacific, are commonly on the ocean region in the southern hemisphere, same as their stay for long periods (days) on the same place and according to their intensity generate this type of traveling waves.

It consists of the abnormal increase of the height of the wave, which is caused by the effect of friction between the surface of the sea and the wind, which is intensified with the passage of bad weather atmospheric systems that push the ocean waters towards the coast causing strong waves.

When the wave breaks over the coast, simultaneously there is a reverse movement of the water towards the sea, (undertow), the latter also being a risk for boats and people on the beaches. The waves can travel distances of up to 10,000 kilometers to the Mexican coast, where they come up against a natural barrier: the beaches.

Characteristics of the swell

The waves are characterized by their regular period and their soft crests, the length that covers the wave is much higher than its height, generating that this one goes out more on the beach reaching places where normally it would not arrive devastating with what is to its reach.

The ocean swell is characterized by its crests and valleys aligned with the waves formed and you can see a single direction which is the one that predominates, when the swell has a direction and a new sea is superimposed on it is known as a two-sided sea.

But not everything is bad, nature, as they say, is wise and this phenomenon of the sea swell brings benefits, because as it travels in all directions stirring, removing, recycling and mixing generates the process of energy change also called natural enrichment bringing many dividends for marine ecosystems.

Prevention and reaction in cases

The mission of the Meteorological Directorate is to obtain, process, and disseminate timely meteorological and climatological information, as well as warnings of severe weather, safeguard human life at sea and support the civilian population living in coastal areas, as well as maintain the necessary coordination with national and foreign institutions.

Numerical models for wave prediction and ocean information infrastructure are used to make calculations and warnings of these waves, supported by metocean buoys and the tide gauge network; through these systems, the phenomenon of the sea swell is monitored until it reaches a period of 72 hours before, to ensure that it will impact the Pacific coast.

Thanks to these numerical models and a close working relationship with other countries such as Chile, it was detected that the vivid phenomenon on the Mexican Pacific coast was caused by a low-pressure system south of the equator.

Swell rips through the Pacific coast

At the end of April and beginning of May 2015, the phenomenon known as the "ocean swell" was experienced with great intensity in the areas of the Pacific, from Chiapas to Baja California Sur.

The effects were felt with much more force in the coastal areas, causing flooding in sectors bordering the beaches and originating, in addition, different degrees of erosion, which sometimes cause damage to nearby constructions such as the structure of minor piers and houses that because of their location are exposed to the direct effects of the tidal wave.

The forecast system showed waves of almost 6 meters for Acapulco and Puerto Angel, as well as for Lázaro Cárdenas there were large waves and towards Jalisco of lesser height, for which the Regional Commands of Guerrero, Oaxaca, and Chiapas were advised of the forecast of swells, and actions were taken to secure boats and naval personnel.

Likewise, the Pacific Coast Civil Protection Protocol was activated in order to initiate preventive actions in the presence of unusual waves. Among them, the placement of red flags on the beaches to indicate high tide and tours by the authorities to warn people not to approach the beach.

Some of the recommendations of the local authorities in the event of such an incident consist of respecting the indications of the trained lifeguard personnel on the beaches; people should avoid going near to observe the breaking of the waves and not swim in the sea if there is a red flag.

Service providers are asked to remove semi-fixed palapa type establishments that are close to the sea, as well as to protect the fixed posts in that area and to remove the furniture to a more distant location; while owners of small boats are recommended to take extreme precautions against the possibility of damage to them, due to high waves and swells.

The most affected areas

The swell gradually extended from the coast of Chiapas to the Baja California Peninsula, maintaining waves between 1.8 and 2.7 meters. Among the areas most affected and where the Declaration of Emergency was announced were the municipalities of Acapulco, Técpan, Benito Juárez, and Coyuca, in Guerrero; and for Pochutla, Colotepec, Huatulco, Villa de Tututepec, Santa María Tonameca, and San Pedro Mixtepec, in Oaxaca.

The balance reported was three dead, three missing, almost 600 homes damaged, and more than 300 restaurants damaged. Support was given to the population affected by the swell phenomenon.