Asu Swell Statistics, August: All Swell – Any Wind
This chart illustrates the range of swells directed at Asu through an average August, based on 2480 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind or surf right at the shore so we have chosen the most applicable 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 describes the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing but without direction information. Five colours illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. These happened only 0% of the time. Green and yellow illustrate increasing swell sizes and red illustrates the largest swells, greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how often that size swell was forecast.
The diagram indicates that the dominant swell direction, shown by the biggest spokes, was SSW, whereas the the most common wind blows from the SW. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Asu and offshore. We lump these in with the no surf category of the bar chart. To simplify things we don't show these in the rose plot. Because wind determines whether or not waves are surfable at Asu, you can view an alternative image that shows only the swells that were expected to coincide with glassy or offshore wind conditions. In a typical August, swells large enough to cause good for surfing 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.