The rose diagram shows the range of swells directed at Tarpits through an average March. It is based on 1724 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast surf and wind right at the shore so we have chosen the most applicable grid node based on what we know about Tarpits. In this particular case the best grid node is 43 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 represent increasing wave sizes. Very small swells of less than 0.5m (1.5 feet) high are shown in blue. These were forecast only 27% of the time. Green and yellow illustrate increasing swell sizes and red illustrates biggest swells greater than >3m (>10ft). In each graph, the area of any colour is proportional to how frequently that size swell happens.
The diagram suggests that the most common swell direction, shown by the biggest spokes, was SW, whereas the the prevailing wind blows from the WNW. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Tarpits and out to sea. We lump these in with the no surf category of the bar chart. To avoid confusion we don't show these in the rose diagram. Because wind determines whether or not waves are surfable at Tarpits, 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 March, swells large enough to cause good for surfing waves at Tarpits run for about 18% 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.