Ocean Beach Swell Statistics, Spring: All Swell – Any Wind
This chart illustrates the variation of swells directed at Ocean Beach over a normal southern hemisphere spring and is based upon 5829 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 Ocean Beach. In this particular case the best grid node is 25 km away (16 miles).
The rose diagram describes the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing but lacks 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 34% of the time. Green and yellow show increasing swell sizes and largest 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 happens.
The diagram suggests that the prevailing swell direction, shown by the biggest spokes, was SE, whereas the the most common wind blows from the WNW. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Ocean Beach and offshore. We combine these 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 Ocean Beach, you can view an alternative image that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. During a typical southern hemisphere spring, swells large enough to cause good for surfing waves at Ocean Beach 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.