Grumari Surf Stats

The figure shows the range of swells directed at Grumari through an average July and is based upon 3472 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 Grumari, and at Grumari the best grid node is 54 km away (34 miles). The rose diagram shows the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing 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 29% of the time. Green and yellow illustrate increasing swell sizes and red shows the biggest swells, greater than >3m (>10ft). In either graph, the area of any colour is proportional to how commonly that size swell was forecast. The diagram implies that the dominant swell direction, shown by the biggest spokes, was S, whereas the the prevailing wind blows from the NE. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Grumari and offshore. We group these with the no surf category of the bar chart. To keep it simple we don't show these in the rose graph. Because wind determines whether or not waves are clean enough to surf at Grumari, you can select a similar diagram that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. In a typical July, swells large enough to cause surfable waves at Grumari run for about 71% of the time.

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