What Is a Swell — And Why Do Surfers Love It? (2023 Guide)

Last Updated March 17, 2023

Did you know that instead of avoiding heavy storms, surfers get ecstatic before and after they occur? During days as such, the waves and swells are guaranteed to be at their gnarliest! 

You see, a good surfing session depends on perfect wind and wave conditions. At the crack of dawn, surfers wake up to check the beach, and when consistent swells break perfectly to the shore, they know that the waves are going to be big and rideable all throughout the day. But how do you think they are able to differentiate the swells from the good and the bad?

This guide contains all you need to know about swells, including how they happen and when you can expect them to occur. You’ll also learn how to foresee good surf days even without reading surf forecasts. Let’s start!

What are swells in the ocean?

Waimea Bay, Banzai Pipeline, and Teahupo’o — these three surfing spots have one thing in common and it’s where you can find the biggest swells in the world. In these locations, swells are able to reach a maximum height of 10 to 12 meters (32 to 40 feet). 

Ocean swells are a group of smooth, long, surface waves created by strong winds. Contrary to what you might think, swells did not come from local winds. Instead, they were generated from weather systems thousands of nautical miles away from the shore where they break.

To give you an idea of how swells are formed, imagine yourself holding a stone, and this stone you’ll eventually drop inside a small container filled with water. The stone represents the storm — the bigger it is, the stronger the storm it’s representing. The water, on the other hand, is the ocean. 

As you drop the stone, you’ll notice that it’ll create ripples as soon as it reaches the water surface. The ripples represent the swells that move away from the ‘storm’. 

That said, ocean swells occur when there’s a tropical depression or storm happening somewhere in North Atlantic or North and South Pacific. As the strong winds blow across the water surface, the winds transfer their energy towards the water. This creates crests that form the swells later on. 

Once these swells generated, they will be impossible to stop. They will travel for days towards the shore away from the wind that created them. As they move, they perturb the water underneath and interact with the waves and current. They also pass through and absorb other swells, which then creates uniform swell lines. 

Meanwhile, the long swells are often the result of short wind waves, and swells that are generated by stronger winds travel as a group at the same speed. Because of the combination of the wind and water’s energy, the swells are able to travel miles away from their origin. 

When these swells reach an island, they bend around it and spread out in between its channels. Once they’re spread out, they dissipate and finally break into the shore.

How Big Swells Form

There are certain factors that determine the size of a swell — the wind’s speed, its intensity, the uninterrupted distance it covers across the water without changing direction (also known as fetch), and the water depth.

The gnarliest swells indicate that a big storm or typhoon had taken place somewhere on the planet. A study shows that swells found in California were created by the severe storms coming from Siberia that traveled across the Pacific Ocean in a northeastern direction. 

But take note that these swells don’t arrive there the same day the storms occur. In fact, it takes about 10 days for the swells to arrive and break to the shore given that they are 1,000 kilometers away from it. And if the storm has a sustained wind speed of 50 knots that last for at least 3 days, it can create the most outrageous swells that’s able to reach 50 ft. in height. 

High-energy swells, on the other hand, peak during the winter season. Accompanying them are strong surges and currents, including cold water. During winter swells, we recommend wearing winter wetsuits that can help regulate your body temperature in low temperatures.

Surfing on Swells 

If you want to make the most out of your surfing sessions, you need to know how to read swells and understand some terminologies. The first things we’re going to discuss are the differences between a groundswell from a windswell, and a swell from a simple wave. 

When a swell travels, it passes through other swells and absorbs them. As it happens, the combined swells create a more consistent and smoother series of ocean waves. On the other hand, a wave is more of a general term that refers to a moving disturbance in the water.

A groundswell is a long-period group of swells that propagate as they travel. An example of groundswells are typhoon swells generated by a depression that’s traveling from east to west.

Groundswells don’t lose energy, so they become consistent and powerful by the time they reach the shore. They also have a swell period that lasts 12 seconds or longer, making groundswells an ideal condition for surfers. 

Meanwhile, windswells are also referred to as windseas. They are generated from local winds and are commonly found in the Baltic, North, and Mediterranean seas.

These swells are short-lived and messy, and because they lose energy as they travel, they only produce weak swells with a wave period of only 10 seconds or below. This is the reason why it’s hard to surf on them.

Swell period

The swell period is the number of seconds it takes for two successive crests to pass through a definite point such as a buoy or piling. The longer the duration there is in between them, the stronger and larger the wave usually is. 

Long swell periods travel much faster and harness more energy. Swells as such are found in popular surfing spots like Waimea, where the swell periods often reach 22 to 30 seconds. This creates the most spectacular breaks that could snap a surfboard in two. Although this condition may cause injury to surfers and damage to coastal properties, hardcore surfers and pros prefer these kinds of swells.

Swell height 

The height of a swell is the difference of the wave crest of a swell to the trough of the next swell. Swell height is often calculated by buoys, and the higher the swell height is, the bigger the waves it’ll bring. 

Risks of surfing in big swells

Big swells will guarantee the most memorable surfing experiences; however, they pose dangers and risks such as drowning and other physical injuries. 

Probably the worst risk of them all is getting pulled underwater during a nasty wipeout and being held there by incoming waves. In this kind of situation, it’s possible you get slammed to the ocean floor and drown while you try to get back up the water surface. Other risks include rip currents which already caused multiple deaths and drowning to a significant number of surfers worldwide. 

Other risks of surfing big swells are the injuries you’ll get from the boards of beginners or kooks who bailed on them as they try to catch big waves. You also need to look out for territorial local surfers who may ‘accidentally’ hit you with their board when you try to surf their swells. 

Frequently Asked Questions 

Q: How do big swells occur?

Swells are groups of waves generated by strong winds from storms that propagate themselves as they travel. On their way to the shore where they will break, they absorb other swells, leading to swells with smoother tops that are more powerful and bigger in height. 

Q: What kind of swells are best for surfing?

As rule of thumb, the longer the wave period is, the bigger the swell is. Swells with a wave period of at least 10 seconds or longer are the most ideal for surfing because they can reach a swell height of 5 to 50 ft. depending on their category.

If you will surf locations known for their big waves such as Banzai Pipeline, we recommend taking necessary precautions because the outrageous breaks of these swells are life-threatening. 

Q: Are swells similar to waves?

Waves are weak, disorganized swells generated by local winds. Meanwhile, swells are consistent, traveling waves that use the combined energy of the wind and water surface to travel thousands of miles away from where they come from. 

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