This chart shows the variation of swells directed at Loblolly Bay over a normal June. It is based on 1594 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind or surf right at the coast so we have chosen the optimum grid node based on what we know about Loblolly Bay. In this particular case the best grid node is 36 km away (22 miles).
The rose diagram describes the distribution of swell directions and swell sizes, 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 67% of the time. Green and yellow show increasing swell sizes and red represents the biggest swells, greater than >3m (>10ft). In either graph, the area of any colour is proportional to how often that size swell occurs.
The diagram indicates that the dominant swell direction, shown by the longest spokes, was NE, whereas the the prevailing wind blows from the ESE. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Loblolly Bay and out to sea. We group 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 good for surfing at Loblolly Bay, you can select a similar diagram that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. During a typical June, swells large enough to cause clean enough to surf waves at Loblolly Bay run for about 33% 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.