Outer Banks Surfing: Wind Conditions and Wave Formation

Enhance your Outer Banks surfing experience by learning the basics of wave parts and wave formation. Study this guide so that you can begin to understand how weather patterns affect the wave that you see hit the shore.

Wind Means Waves

The wind creates our waves. However, strong wind doesn’t always produce the best waves for surfing. The best waves often originate hundreds of miles from our shore, the result of low-pressure weather systems.

Conditions that Determine Wave Formation

Wind Speed:  More energy equals more speed. This will be determined by the differences between high- and low-pressure weather systems: the greater the range, the faster the speed. The biggest ranges come during intense low-pressure storm systems.

Duration: The longer the wind blows over the same area of the ocean, the bigger the swells will be.

Fetch: The fetch is the area of the unbroken distance wind gets to blow before hitting an obstacle.  Fetches can be thousands of miles of open water.

More energy equals more speed. This will be determined by the differences between high- and low-pressure weather systems: the greater the range, the faster the speed. The biggest ranges come during intense low-pressure storm systems.

Ocean Wave Height Versus Rideable Surf

There is a science to wave formation, but here are the basics. A wave contains two parts: a crest is the point on a wave with the maximum value or upward displacement within a cycle, and a trough is the opposite of a crest, so the minimum or lowest point in a cycle.

The wavelength is the distance over which the wave’s shape repeats. The vertical distance between the crest and the trough is the wave height. This is the height of the waves before they hit the shallow water and start to break.

Wave Height

Waves begin as a slight disturbance on the water that become ripples and grows as the energy increases. From here two factors determine a wave’s height:

Period: The wave period is the time between successive crests. Long-period waves tend to be larger and stronger, while short-period waves are smaller and weaker. Measurement of wave periods helps surfers predict the coming swell over the next several hours and determine whether different swells (waves that originated in varies locations) are contacting the beach at the same time. Generally, longer period waves travel longer distances, create more energy, and develop higher on-shore breakers.

Frequency: Wave frequency is the number of waves passing a fixed point in a given amount of time.

Wave Speed

The speed of a wave has a close relationship to its wavelength. Small waves tend to move slowly at a few knots. Medium-sized waves may move at 10 to 20 knots and large waves move at 30 to 50 knots, sometimes more.

The ability to predict swell height at the shore involves the shape of the ocean floor as it nears the beach (bathymetry), the beach shape, the direction of the swell, local wind direction and strength, and refraction.

Bathymetry

Bathymetry is the study of underwater depth of lake or ocean floors. As waves enter more shallow water they slow and lose energy, power, and size.

Beach Shape

Beach shape is part of bathymetry. A swell hitting an embankment from deep water will create a larger wave than the same sized swell moving up a gently sloping sandy beach. Other obstacles include sandbars, artificial reefs, shipwrecks, and point breaks.

Swell Direction

Each break has its own optimum swell direction which will always affect the wave height of that surfing spot. Some swells might miss a break while others may combine with the other factors and hit the reef or beach in a way to create perfect surfing waves.

Local Winds

Onshore winds are a surfer’s nightmare. A strong wind blowing off the ocean will make the waves flat, misshaped, and sloppy. Offshore winds, however, hold a wave up and provide a nice ridable face and will maintain or increase the wave’s height.

Refraction

Refraction is the change in direction of a wave due to a change in its optical medium.

As we mentioned earlier, a swell moving into shallow water will slow. With the right oceanbed configuration (such as a pointbreak), the wave nearer the beach will slow more than the swell still in deeper water. This will bend the swell into the break and can increase the size of the breaking waves (concave refraction) or reduce it (convex refraction). This also depends on the period of the swell and grows with higher periods.

Predicting Waves

If you make a habit of monitoring pressure systems and wind direction, you will become fairly accurate at predicting wave heights at the Outer Banks.