In this article we analyze the momentum and vorticity balances of a numerical simulation of the upwelling circulation off central Chile (34¿--40¿S) and its response to interannual local wind changes. Our analysis indicates that the path of the upwelling jet is strongly controlled by the bottom topography. This topographic steering causes the jet to separate from the coast at the Punta Lavapie cape (~37¿S). Although the zeroth-order momentum balance is dominated by the geostrophic terms, the circulation is also affected by nonlinear processes, which lead to the formation of large meanders and the shedding of cyclonic eddies north of Punta Lavapie during periods of wind relaxation. The relative contributions of the zeroth-order vorticity balance and the advective terms are also strongly controlled by changes in the coastline geometry and the bottom topography. Vorticity is created along the current axes and transported toward the coast and the Peru-Chile Trench, where it dissipates. South of Punta Lavapie the across-shelf transports are weaker with equatorward flows that are more stable than in the north. Additional numerical simulations indicate that during periods with El Ni¿o conditions, the area is affected with a general weakening of the currents and upwelling activity, although the northern region still shows the formation of eddies. During years with relatively stronger winds, in contrast, the upwelling activity and across-shelf transport processes are significantly increased. The results show that the Punta Lavapie cape has a large effect on the spatial and temporal variability of the coastal currents in the region off central Chile.