Near Shore

As ocean waves enter shallow water nearer the shore they start to change their behaviour. Understanding these effects and how swell models do and don’t account for them is crucial to transforming a forecast for the incoming swell into an understanding of the surfing conditions at your local beach.

Sea Temps and Coastal Upwelling

Your MSW forecast gives a current sea temperature for every spot we list.  The data comes from a Satellite survey. The Satellite is capable of extremely accurate readings of the surface temperature – however at maximum it’s capable of monitoring an area of about 1 Square Kilometer and the data we then receive is averaged over an area larger than this. For most of the worlds surf breaks this is a reliable guide to temperatures encountered in the surf, but there are circumstances where this isn’t the case. In some areas a phenomena know as ‘coastal upwelling‘ can cause problems. Briefly (and click the link for an article with more […]

Entering Shallow Water

Predicting the track of open ocean swells in deep water is almost easy. Waves travel in very predictable patterns, height slowly decreases as the swell propagates. Waves of different periods separate and arrive at different times. Given an understanding of the strength of the original storm you could calculate roughly the size and arrival time of the swell with some fairly simple maths and without needing a computer. What happens as these waves enter shallow water is where a large part of the challenge to us as surf forecasters lies. Shallow water is defined in relation to the period of the wave. Longer period swells have longer wavelengths and a […]

Breaking Waves

We’ve described how shallow water effects waves as they head towards the coast. Of course the most dramatic effect is the one we’re most interested in as surfers, the final breaking phase. As waves enter shallow water they slow down and they change shape, increasing in height. Once they reach a water depth of approximately 1.3 times their height they start to break. How rapidly this happens is affected by the local sea bed, on a gently sloping beach with light winds the wave will gradually increase in height eventually the top starts to spill gently forward. These waves break slowly, they’re definitely surfable and can form the staple part […]

Local Winds

Wind is responsible for creating surf, but the wind in the last couple of miles at the beach also has a profound effect on the waves produced on the beach. When we talk about wind we talk about the direction which it comes from, for example a North wind blows from the North to the South. We also talk about wind as onshore, offshore and cross-shore. Onshore Onshore wind blows from the sea to the land. It pushes on the back of incoming waves. This extra pressure causes waves to break earlier and in deeper water, particularly on more gently sloping beaches this generally creates a less steep wave face […]