Agnes Waters Swell Statistics, Winter: All Swell – Any Wind
This picture shows the variation of swells directed at Agnes Waters through an average southern hemisphere winter. It is based on 7266 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast surf and wind right at the coast so we have chosen the best grid node based on what we know about Agnes Waters. In the case of Agnes Waters, the best grid node is 27 km away (17 miles).
The rose diagram describes the distribution of swell sizes and directions, while the graph at the bottom shows the same thing but without 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 happened 48% of the time. Green and yellow show increasing swell sizes and biggest swells greater than >3m (>10ft) are shown in red. In both graphs, the area of any colour is proportional to how frequently that size swell happens.
The diagram suggests that the prevailing swell direction, shown by the largest spokes, was ENE, whereas the the prevailing wind blows from the SE. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Agnes Waters and offshore. We group 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 clean enough to surf at Agnes Waters, you can load a different image that shows only the swells that were expected to coincide with glassy or offshore wind conditions. In a typical southern hemisphere winter, swells large enough to cause surfable waves at Agnes Waters run for about 52% 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.