Storms and winds can affect how waves are formed.
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Look for Surfable Waves!

Ground Swells vs Wind Swells

There are various factors that affect how waves are formed. Without storms and winds, surfers wouldn’t be able to surf in the ocean. And that would bite!

surf kata noi
Phuket, Thailand

When strong winds blow in the deep blue sea thousands of miles offshore, it gradually creates wave energy! These waves build up as they travel towards the shore and after sorting themselves out, they then become swells. They develop a “wave train” and ultimately arrive along the coastal surf breaks.

These types of waves that make their way to the shores are made from groundswells. They are classified as a long period swell (greater than 14 seconds between successive waves) and they contribute to greater wave energy and ultimately, bigger and cleaner waves to ride.

When you see consecutive waves that are organized and lined up in sets, that’s when you know that they’re made by groundswells. This is the preferred type of swell (and period) that experienced surfers seek for when checking surf reports.

surfing kata beach
Blown out waves at Kata beach

The other type of swell that creates waves are windswells.  These waves are generated by local winds blowing hundreds of miles or less offshore. They are classified as short period swells (less than 15 seconds between successive waves).

Since this type of wave energy does not interact with the ocean floor, waves tend to dissipate because of their susceptibility to opposing winds and seas. You can easily distinguish them by noting their choppy, unorganized, and jumbled waves with offshore whitecaps, which characterizes them. In general, these waves do not provide the best rides for surfers, however, they still can be pretty fun at times.

A combination of groundswells and windswells can also create surfable waves. As mentioned earlier, many factors including wind speed, wind duration, fetch, seafloor topography (bathymetry), swell direction, and tide all contribute to the quality of waves.


Offshore vs Onshore

It’s very important to know your surf break’s desired wind direction as well as its cardinal directions (North, East, South, West) because knowing whether the winds are offshore or onshore will give you a better idea of the surf conditions.

Offshore winds

Offshore winds are what surfers look for. The direction of this type of wind blows from the land towards the ocean. Breaking waves are slightly “held up” offering cleaner faces and better shape overall. You can visibly tell when winds are offshore by watching the “spray” at the top of breaking waves being blown out towards the ocean. Strong offshore winds can also make it more difficult to get into a wave and will require an extra boost of paddling power. Build up your paddle endurance now!  

Onshore winds

Onshore winds may be good for cool ocean breezes but they are not favorable for surfing. Winds blowing in the direction from the ocean towards the land essentially ruins the shape of waves making them crumble and consequently, unsurfable. Bad onshore winds! Bad!

Cross shore winds

Cross shore winds are also not favorable if it’s blowing considerably strong. Light cross shore winds will affect the conditions but the surf may still be manageable.

Beginner Surfer’s Guide

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