Governors Island Swell Statistics, Janeiro: All Swell – Any Wind

The figure shows the variation of swells directed at Governors Island over a normal January, based on 2868 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast surf and wind right at the coastline so we have chosen the most applicable grid node based on what we know about Governors Island. In this particular case the best grid node is 21 km away (13 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 64% of the time. Green and yellow represent increasing swell sizes and red illustrates the biggest swells, greater than >3m (>10ft). In each graph, the area of any colour is proportional to how often that size swell happens.

The diagram indicates that the prevailing swell direction, shown by the largest spokes, was E, whereas the the prevailing wind blows from the NNE. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Governors Island 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 plot. Because wind determines whether or not waves are surfable at Governors Island, 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 January, swells large enough to cause good for surfing waves at Governors Island run for about 36% 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.