Aligator Rock Swell Statistics, Winter: All Swell – Any Wind
The graph describes the variation of swells directed at Aligator Rock over a normal northern hemisphere winter, based on 6931 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind or surf right at the shore so we have chosen the most applicable grid node based on what we know about Aligator Rock. In the case of Aligator Rock, the best grid node is 42 km away (26 miles).
The rose diagram describes the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing 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 were forecast only 24% of the time. Green and yellow illustrate increasing swell sizes and red illustrates the highest swells, greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how often that size swell happens.
The diagram indicates that the dominant swell direction, shown by the largest spokes, was NW, whereas the the dominant wind blows from the E. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Aligator Rock and away from the coast. We lump these in with the no surf category of the bar chart. To simplify things we don't show these in the rose diagram. Because wind determines whether or not waves are surfable at Aligator Rock, you can load a different image that shows only the swells that were expected to coincide with glassy or offshore wind conditions. During a typical northern hemisphere winter, swells large enough to cause good for surfing waves at Aligator Rock run for about 76% 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.