The Strait Swell Statistics, December: All Swell – Any Wind
This picture shows the combination of swells directed at The Strait over a normal December. It is based on 2457 NWW3 model predictions since 2006 (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 The Strait. In this particular case the best grid node is 44 km away (27 miles).
The rose diagram illustrates the distribution of swell sizes and directions, while the graph at the bottom shows the same thing but without direction information. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These were forecast only 23% 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 was forecast.
The diagram suggests that the prevailing swell direction, shown by the longest spokes, was W, 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 The Strait and offshore. We combine these with the no surf category of the bar chart. To avoid confusion we don't show these in the rose plot. Because wind determines whether or not waves are good for surfing at The Strait, 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 December, swells large enough to cause clean enough to surf waves at The Strait run for about 58% 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.