North Atlantic 950mb Super Storm

Check out this chart issued by the NWS Ocean Prediction Center. It shows the developing North Atlantic 950mb low that set to bring huge surf to Europe over the weekend of the 15th/16th December. The outline, matching the size and shape of the continental US, shows just how huge the storm is – with an fetch stretching from Portugal to the Labrador sea: Or for a slightly clearer view of the coast here’s the same storm on our charts: The southerly Jetstream means swell will develop futher South than has been typical of recent storms, bringing larger swell to the coasts of Portugal and central Europe and opening up less […]

Combining Swells Issue

Some feedback on the new forecast highlights cases like this where the basic overview is dramatically different – it’s worth explaining because it highlights a considerable issue with the old layout that helps explain why we’ve made the change. You can see below an image showing the differences for Cape Town this week: On the face of it a 50% larger call on the old forecast than the new one. In fact the situation is pretty simple – in both cases the model data is the same but the difference is the way we interpret the fact that there are actually two swells running: A solid SW ground swell and […]

Forecast Period vs Wave Buoy Period

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 […]

Nazaré Update

The outlook remains positive for swell on Wednesday. The swell arrives in two simultaneous pulses, clearly separable in the morning on the latest forecast here. For some locations we suspect this can be an issue affecting the final size, but for Praia do Norte there’s less of an issue – with the spot relying on the cross up of the refracted long period component it could even be a benefit. Regardless we’re looking at a significant swell event moving into the sort of range the Red Bull Mito contest is seeking. The issues have been, and to some extent remain, the wind. You can see from the top chart that as this […]