Nungwi Reefs Surf Stats

The rose diagram shows the combination of swells directed at Nungwi Reefs over a normal September and is based upon 3360 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast surf and wind right at the shore so we have chosen the best grid node based on what we know about Nungwi Reefs, and at Nungwi Reefs the best grid node is 38 km away (24 miles). The rose diagram shows the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing but lacks direction information. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These occurred only 1.3% of the time. Green and yellow show increasing swell sizes and red shows the biggest swells, greater than >3m (>10ft). In both graphs, 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 longest spokes, was ESE, whereas the the prevailing wind blows from the SSE. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Nungwi Reefs and away from the coast. We lump these in 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 clean enough to surf at Nungwi Reefs, you can select a similar diagram that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. During a typical September, swells large enough to cause surfable waves at Nungwi Reefs run for about 99% of the time.

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