The graph describes the variation of swells directed at Big Wave Bay over a normal April. It is based on 1630 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast wind and surf right at the coastline so we have chosen the most applicable grid node based on what we know about Big Wave Bay. In the case of Big Wave Bay, the best grid node is 38 km away (24 miles).
The rose diagram shows the distribution of swell sizes and directions, 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 happened only 57% of the time. Green and yellow illustrate increasing swell sizes and highest swells greater than >3m (>10ft) are shown in red. In each graph, 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 largest spokes, was ENE, whereas the the dominant wind blows from the ESE. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Big Wave Bay 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 plot. Because wind determines whether or not waves are good for surfing at Big Wave Bay, you can load a different image that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. During a typical April, swells large enough to cause clean enough to surf waves at Big Wave Bay run for about 0% 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.