A suite of satellite data are used to study the near surface westerly winds developing during peak months (July--September) of the West African monsoon in the Atlantic Intertropical Convergence Zone. These new data show that the westerlies appear in the form of a westerly jet. During peak years the daily near-surface westerly wind speed may exceed 10 ms-1. The amplitude of the jet displays substantial decadal and interannual variability that corresponds to rainfall in the West African Sahel and the frequency of African Easterly Waves. Observations and ocean model simulations show that the jet acts to cool SST through entrainment and latent heat loss and to intensify the North Equatorial Countercurrent by increasing the southward oceanic pressure gradient.