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Half Moon Bay ratings
Quality on a good day: 2.0
Consistency of Surf: 2.0
Difficulty Level: 1.0
Crowds: 4.0

Overall: 2.8

See all 18 ratings

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Surf Report Feed

Half Moon Bay Swell Statistics, December: All Swell – Any Wind

The graph illustrates the combination of swells directed at Half Moon Bay through an average December and is based upon 2953 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind and surf right at the coast so we have chosen the best grid node based on what we know about Half Moon Bay, and at Half Moon Bay the best grid node is 31 km away (19 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 happened only 4% 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 often that size swell was forecast.

The diagram indicates that the most common swell direction, shown by the longest spokes, was W, whereas the the most common wind blows from the SSE. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Half Moon Bay and away from the coast. We combine these with the no surf category of the bar chart. To simplify things we don't show these in the rose plot. Because wind determines whether or not waves are surfable at Half Moon Bay, you can load a different image that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. In a typical December, swells large enough to cause good for surfing waves at Half Moon Bay run for about 96% 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.