Katwijk aan Zee Surf Stats

The rose diagram illustrates the range of swells directed at Katwijk aan Zee through an average April and is based upon 3351 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast surf and wind right at the shore so we have chosen the optimum grid node based on what we know about Katwijk aan Zee, and at Katwijk aan Zee the best grid node is 31 km away (19 miles). The rose diagram shows the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing but lacks direction information. Five colours represent increasing wave sizes. Very small swells of less than 0.5m (1.5 feet) high are shown in blue. These were forecast 65% of the time. Green and yellow illustrate increasing swell sizes and red illustrates largest swells greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how often that size swell occurs. The diagram indicates that the dominant swell direction, shown by the biggest spokes, was NW, whereas the the most common wind blows from the N. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Katwijk aan Zee and offshore. We combine these with the no surf category of the bar chart. To keep it simple we don't show these in the rose graph. Because wind determines whether or not waves are clean enough to surf at Katwijk aan Zee, you can select a similar diagram that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. In a typical April, swells large enough to cause surfable waves at Katwijk aan Zee run for about 35% of the time.

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