Itapiruba • Statistics for September

September: Biggest Swell, Tricky Winds

September is the heaviest month for raw swell size, with the average height climbing to around 6-6.5ft (1.9m) and period holding at 9.4s. The South Atlantic is at its most active, with storm after storm pushing toward the coast and generating solid groundswell from the entire east-south-southeast spectrum. ENE (15.4%), E (13.8%), ESE (13.6%), SE (13.4%) and SSE (12.0%) all pump consistently, while S (11.1%) adds extra southern energy. The 5-6.5ft (1.5-2m) and 6.5-8ft (2-2.5m) classes are unusually well filled, making this the month most likely to produce consistent overhead-plus surf.

The catch is wind. Ideal-window frequency drops to 37%, one of the lowest of the year. NNE (24.9%) and NE (15.5%) winds, often in the 20-40kph range, put a bump on what would otherwise be epic surf. SSW (11.4%) and SW (10.5%) still show up, but true W-NW offshores are rare. The saving grace is that when a strong cold front passes and the wind turns offshore, the combination of size, period and groomed surface can produce firing waves. With water at 18.2°C and air at 18.2°C, and spring rains starting to build (4.43mm/day), you have to pick your windows carefully.