Alibaba • Statistics for September

September: Autumn Rumbles Begin

September is a transition month in the Cape Verdean surf year. The average swell height rises to 5ft (1.6m) and the average period jumps to 9.2s, a sign that the ocean is beginning to wake up after the summer slumber. The swell direction is still NNE-heavy (62.4%), with N at 15.0% and NNW at 10.3%, but the percentage of N and NNW swell is growing and hints at the return of the winter groundswell train. Alibaba remains constrained by the absence of SSW/SW/W swell, but the longer periods mean the refracted northern energy has more push.

Winds are still mostly from the NE/NNE quarter, with NE (33.3%) and NNE (30.6%) sharing the load. Ideal wind conditions occur 38% of the time, making September one of the more favorable months for combining clean surfaces with building swell. Water temperature peaks at around 27.0°C, air temps average 26.4°C, and rainfall is higher at 1.40mm/day as the Atlantic moisture deepens. Late September can deliver the first solid pulses of the new season, especially if the NAO index trends negative and the storm track begins to dip south.