Assateague Swell Statistics, Winter: All Swell – Any Wind
This chart illustrates the combination of swells directed at Assateague through an average northern hemisphere winter. It is based on 6931 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind or surf right at the coastline so we have chosen the best grid node based on what we know about Assateague. In the case of Assateague, the best grid node is 28 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 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 were forecast only 50% of the time. Green and yellow represent increasing swell sizes and red shows largest swells greater than >3m (>10ft). In each graph, the area of any colour is proportional to how often that size swell happens.
The diagram indicates that the most common swell direction, shown by the longest spokes, was SE, whereas the the most common wind blows from the WNW. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Assateague and away from the coast. We combine 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 Assateague, you can load a different image that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. In a typical northern hemisphere winter, swells large enough to cause surfable waves at Assateague run for about 50% 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.