Asu Swell Statistics, Spring: All Swell – Any Wind
The rose diagram illustrates the range of swells directed at Asu over a normal northern hemisphere spring and is based upon 6580 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast wind or surf right at the coastline so we have chosen the best grid node based on what we know about Asu. In the case of Asu, the best grid node is 30 km away (19 miles).
The rose diagram shows the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing without direction information. Five colours illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. These were forecast only 0% of the time. Green and yellow illustrate increasing swell sizes and red shows the largest swells, greater than >3m (>10ft). In each graph, the area of any colour is proportional to how commonly that size swell occurs.
The diagram implies that the most common swell direction, shown by the longest spokes, was SSW, whereas the the most common wind blows from the WSW. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Asu and out to sea. We combine these with the no surf category of the bar chart. To keep it simple we don't show these in the rose diagram. Because wind determines whether or not waves are good for surfing at Asu, you can view an alternative image that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. During a typical northern hemisphere spring, swells large enough to cause clean enough to surf waves at Asu run for about 100% of the time.
IMPORTANT: Beta version feature! Swell heights are open water values from NWW3. There is no attempt to model near-shore effects. Coastal wave heights will generally be less, especially if the break does not have unobstructed exposure to the open ocean.