We get regular emails telling is that the forecast swell period is wrong. This assessment is based, quite reasonably, on the regular differences between the model forecast and the numbers observed on a local wave buoy. However this difference doesn’t mean either is wrong. The explanation is that most wave buoys look at ‘average period’ of all swells where, more usefully, your forecast looks at peak period of each separate swell. The crucial thing to understand about model forecasting is we’re trying to simplify things in order to predict them. Most surfers know that swell height is the peak to trough size of the wave and that wave period is the time [...]
MSW is a tool kit designed for any surfer. But without some idea how to use those tools and what they do you’re missing out on much of the value. With a little time on this site, starting in this section, you’ll be better equipped to make your own call.
Bit of back to basics for many but we know a lot of keen surfers still feel less than confident with understanding swell direction*. We’ve written a little example of reading swell direction on your surf forecast that talks about the importance of this for understanding the surf (there’s plenty more to add – it’s a critical part of the forecast) but before you can even do that you need to get to grips with the terminology. This diagram is a nice illustration to understand the relationship between degrees and the compass points. On MSW we always talk about swell and wind directions as the direction they come FROM. So [...]
I have noticed when I’m reading the surf report say at 5ft 12seconds yet when i look at the buoy data the size is usually very close to the report but period 7-8 seconds based on the example we are using ,Im aware the buoy data is taken at every hour and there may be alot of different swell trains off ground and wind swells all interacting and affecting the data, but I thought the dominant groundswell would show up and cancel out the inferior windswells,could you explain why the period always smaller than surf report says. Many thanks jonathan. Hi Jonathan, Short answer the wave buoy reports ‘average’ period [...]
The earth isn’t flat, but our charts are. When we create a flat chart to represent the curved surface of our oceans we have to choose a ‘projection’ that converts one to the other. The downside of the way we do this (and the way everyone has to do this to make maps that you’ll recognise, check this out for more information) is that a straight line on the chart isn’t the same as a direct line on the earth’s surface. This means a swell that appears to be a straight shot to your local break might actually not make it and also means the swell window for some regions [...]