This image shows the variation of swells directed at El Porto Beach through a typical January, based on 1728 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 optimum grid node based on what we know about El Porto Beach. In the case of El Porto Beach, the best grid node is 46 km away (29 miles).
The rose diagram describes the distribution of swell sizes and directions, while the graph at the bottom shows the same thing 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 17% of the time. Green and yellow represent increasing swell sizes and biggest swells greater than >3m (>10ft) are shown in red. In either graph, the area of any colour is proportional to how frequently that size swell was forecast.
The diagram suggests that the dominant swell direction, shown by the biggest spokes, was WSW, whereas the the prevailing wind blows from the N. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from El Porto Beach and offshore. We lump these in with the no surf category of the bar chart. To keep it simple we don't show these in the rose diagram. Because wind determines whether or not waves are surfable at El Porto Beach, you can select a similar diagram that shows only the swells that were expected to coincide with glassy or offshore wind conditions. Over an average January, swells large enough to cause good for surfing waves at El Porto Beach run for about 83% 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.