Andrew Molera State Park Swell Statistics, September: All Swell – Any Wind
This picture illustrates the range of swells directed at Andrew Molera State Park over a normal September and is based upon 2400 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind and surf right at the coastline so we have chosen the optimum grid node based on what we know about Andrew Molera State Park. In the case of Andrew Molera State Park, the best grid node is 27 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 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 21% of the time. Green and yellow show increasing swell sizes and red shows the largest swells, greater than >3m (>10ft). In either graph, the area of any colour is proportional to how commonly that size swell happens.
The diagram implies that the most common swell direction, shown by the longest spokes, was W, whereas the the most common wind blows from the NW. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Andrew Molera State Park and away from the coast. We lump these in with the no surf category of the bar chart. To simplify things we don't show these in the rose diagram. Because wind determines whether or not waves are good for surfing at Andrew Molera State Park, you can view an alternative image that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. During a typical September, swells large enough to cause clean enough to surf waves at Andrew Molera State Park run for about 79% 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.