Watching big waves break is one of the most amazing feats that Mother Nature can produce. However, big waves do not simply grace the shores of your local beach on a regular basis. Many factors have to come together in order for big waves to be generated. It takes a special weather event for the conditions to be right to produce these large, mythical waves.
The Big Wave Formula
There are two key factors needed to produce a big wave surfing spot:
- Geographical Location – one that is in position to pick up large swells. Not every beach is precisely situated to receive large swells generated from distance storms.
- Seafloor Topography – the rise and fall of the surrounding seafloor. An abrupt rise in the seafloor will produce larger waves than a very gradual rise.
This unique combination of big-wave-producing factors only exists in a handful of locations around the world, which is why big wave surfers are committed to leaving at a moment’s notice, even if the swell is breaking at a beach halfway around the world.
With these two factors in mind, let’s dive into greater detail to see how big waves are created.
What Creates Big Waves?
To the surprise of many, waves are actually created by wind, which is generated by large storms that originate thousands of miles from shore. The conditions have to be just right in order to get the correct wind equation to create big waves. There are only a handful of storms each year that have this wind/wave making potential.
These powerful storms are packed with energy in the form of wind. This energy (or wind) that the storms generate is then transferred from the air into the ocean. Wind is what creates the energy that creates waves.
The Right Storm Conditions
Basically, strong wind is created by low-pressure systems (hurricanes, cyclones). These low-pressure systems have what is called a pressure gradient, which is the pressure difference between high and low pressure. This typically happens when a low-pressure system comes into close proximity with a high-pressure system, and in between these two massive weather systems, the wind begins to blow very strong over the open ocean.
The Three Wind Components Used to Measure and Create Big Waves:
- Wind Speed – how fast the wind is blowing over the ocean
- Fetch – the size of the expanse of water that the wind is blowing over
- Duration – how long the wind is blowing over the ocean in one particular direction
Ex: 65 mph winds blowing over 2200 miles for four or five days will generate some very big waves.
Turning Strong Wind into Swell
As we stated before, the storms impart their energy into the ocean in the form of wind. This wind then blows into and over the ocean, creating open ocean swells, which then turn into waves as they near the shore and break.
What Factors Measure Swell Size and Power?
- Wave Height – how tall the wave is
- Wave Period – time from crest to crest
- Wave Length – distance between the two peaks
Typically, swell size is measured like this: 15 feet at 14 seconds.
This means that 15-foot swells are traveling 14 seconds apart. The swell height determines the height of swells that are traveling toward shore. The swell period determines the thickness of the traveling swells. So, a 15-second swell period represents a much thicker swell than a five-second swell period. The longer the swell period, the more thick and powerful the swell.
So far, we have learned that big, well organized storms create the energy that creates big, open ocean swells that travel toward shore. But how do these swells translate into big waves?
Swells vs. Waves
At this stage it is important to remember that swells and waves are related, but very different pieces in the big wave puzzle. Swells are long, thick waves that originate in storms thousands of miles from shore. Swells are well groomed and organized, since they originate from a large power source, and they travel undisrupted across the open ocean. A breaking wave is the result of a swell reaching the shore and breaking over itself, as it has no more room to travel forward.
Generally, surfers much prefer to ride waves generated from strong swells that originated from distant storms rather than wind waves that are generated closer to shore. As swells meet the approaching coastline, they are often well organized and free of surface chop, which results in a clean peeling wave. Wind waves, on the other hand, are disorganized and riddled with surface chop.
How Waves Break
In order for a traveling swell to become a breaking wave, it needs to begin moving from the deep open ocean toward a shallower depth near shore. As the seafloor begins to get shallower and shallower, the wave energy, which is stored below the surface, then becomes compressed. The only place for the compressed swell energy to go is up, which causes the wave height to increase.
The rate at which swell energy gets transferred into increasing wave height depends on how fast the seafloor rises out of the deep ocean. If the ocean floor abruptly rises from a deep depth, this will have a more dramatic effect on wave height than if there is a gradual rise.
As the wave height rises, the wave energy is converted into kinetic energy, which causes the wave to break over itself, forming the whitewater that is seen on a breaking wave.
Ocean Floor Topography
The final piece of the big wave puzzle is the surrounding ocean floor topography. Big storms and swells are generated in every ocean around the world, but it is the ocean floor topography that determines whether or not a particular beach is going to produce average waves (four- to eight-foot waves) or big waves (12-foot-plus).
The best ocean floor setup for producing big waves is when the seafloor abruptly rises out of the deep ocean. This abrupt rise in seafloor is often formed by reefs, underwater sea mounts, rocks, or ledges. These natural underwater formations quickly focus approaching swells into rising, breaking waves. The part of the wave that hits the reef/rock/sea mount first will slow down, rise, and then break, while the wave out on the side is going to keep traveling, which will cause the wave to bend, angle, and then focus. This bending and angling is what causes the waves to peel, making it possible for surfers to get nice, long rides.
