Andromeda Swell Statistics, December: All Swell – Any Wind
The figure illustrates the combination of swells directed at Andromeda through an average December and is based upon 2457 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 optimum grid node based on what we know about Andromeda, and at Andromeda the best grid node is 63 km away (39 miles).
The rose diagram describes the distribution of swell sizes and swell direction, 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 were forecast only 16% of the time. Green and yellow represent increasing swell sizes and red shows the largest swells, greater than >3m (>10ft). In each graph, the area of any colour is proportional to how commonly that size swell happens.
The diagram implies that the most common swell direction, shown by the longest spokes, was SW, whereas the the most common wind blows from the SSW. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Andromeda and away from the coast. 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 clean enough to surf at Andromeda, you can select a similar diagram that shows only the swells that were expected to coincide with glassy or offshore wind conditions. In a typical December, swells large enough to cause surfable waves at Andromeda run for about 84% 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.