Ann Street Peaks Swell Statistics, May: All Swell – Any Wind
This chart describes the variation of swells directed at Ann Street Peaks through an average May. It is based on 2200 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast wind or surf right at the coast so we have chosen the best grid node based on what we know about Ann Street Peaks. In this particular case the best grid node is 45 km away (28 miles).
The rose diagram shows the distribution of swell sizes and directions, while the graph at the bottom shows the same thing without direction information. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These occurred only 8% of the time. Green and yellow show increasing swell sizes and red represents highest 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 most common swell direction, shown by the biggest spokes, was ESE, whereas the the dominant wind blows from the SSE. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Ann Street Peaks and out to sea. We combine these with the no surf category of the bar chart. To simplify things we don't show these in the rose graph. Because wind determines whether or not waves are surfable at Ann Street Peaks, you can load a different image that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. In a typical May, swells large enough to cause good for surfing waves at Ann Street Peaks run for about 92% 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.