Surf Swells

As a surfer, understanding how swells impact the waves is critical. Before the Internet came around, surfers would often use tide charts and weather reports to understand how the waves would be that day.

Today, we can use factors like wind direction, wave height, and, most importantly, swell information. So if you want to become a master wave reader, come dive in with us as we explore the ins and outs of swells.

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What Creates Surf Swells?

Swells often generate in mid-latitude depressions in the North Pacific and North Atlantic regions, though sometimes in the South Pacific.

Many people believe that local winds (winds on land) generate swells, though they really result from massive storm winds that take place thousands of miles offshore.

The best way to think of how a storm works, is thinking of it as a drop of water hitting the surface of a calm pond and the water slowly rippling out towards the edges.

The harder and longer this offshore wind blows, the larger the swell becomes. To get a bit scientific: wave trains are a group of waves of equal or similar wavelengths traveling in the same direction.

As a swell continues moving away from the storm formation, longer wavelength wave swells will travel faster, and destroy short-wavelength swells. The initial waves in a long swell period move much quicker than the last carriages in the wave trains. To gain a deeper understanding, check out our why do waves break article.

What Affects Swell Size

Three main variables affect the size of a swell, including:

Wind Direction - Longer offshore winds create larger waves
Wind Speed - The greater the wind speed, the larger the waves
Fetch - The greater the wind area, the larger the waves

A wave will begin losing energy once the wind is no longer impacting it. The friction of the sea and any other obstacles, such as rock and islands, will slow a wave down as it moves along.

When it comes to the wave size at your local surf break, there are a few factors that have an influence, including:

Ocean Floor - A swell that comes directly up onto a reef from a deep seafloor creates massive, barreling waves. On the other hand, waves that come up ashore from a long, shallow ledge will drag and often be much smaller.
Swell Direction - If the break is open to the direction of the swell, it will break much better.
Tide - There are many surf spots out there that are dependent on the tides.

Difference Between Surf And Swell

When surfers talk about the "surf," they usually refer to the waves that break on the ocean's shoreline.

When surfers talk about "swell," they usually refer to a long series of wind-produced, open-ocean waves. A swell will create surf.

Understanding Swell Direction

You must understand the swell direction if you want to know whether or not it will hit your local surf breaks correctly. When you read a surf report, you will typically see swell direction expressed using cardinal points (N, S, E, W).

Generally, a beach that faces directly to the west will receive better, larger waves if a swell is coming in from the west.

The direction of the swell is VERY important, as you will not receive great waves if the swell doesn't hit your region correctly.

For example, Southern California gets plenty of southwest swells during the summer.

Many breaks in San Diego county face west, meaning they won't get many great waves from those swells.

On the other hand, there are many breaks in Orange County that face southwest, meaning during those summer swells, they will get much larger waves.

Ground Swell Vs. Wind Swell

A ground swell is a formation of waves traveling away from the generated area that propagates itself for many miles. Ground swells will accumulate mass-energy before reaching the shoreline, creating powerful and consistent wave trains. Surfers LOVE groundswells, as they provide excellent waves.

Wind swells are generated by local winds and are very short-lived. You will commonly see wind swells in the Mediterranean Sea, Baltic Sea, and the North Sea. They are very disorganized and don't last for long periods.

Difference Between Wave Height And Swell Height

The average height of a swell when it is out at sea is called the swell height. To measure swell height, you must measure from the trough to the peak, as well as the amount of time (in seconds) between a single peak and the next. Scientists will often use offshore ocean buoys to measure swell height.

On the other hand, wave height is the average size of the waves once they've reached the beach. This measurement is what surfers often use to talk about the waves they surf. Depending on the surf report and the forecasting model they use, you might see slight variations in wave height.

Using Swell Information To Read Surf Reports

Knowing more about swells can teach you how to read a surf report correctly. We understand that at first glance, a surf report can look overwhelming. However, understanding how swells fall into the equation will make reading any surf report easier.

There are many websites out there that provide surf reports, including some of our favorites like Surfline and MagicSeaWeed.

If you want to learn more about how to read a surf report correctly, check out our article below on onshore winds vs. offshore winds.