We have sought to simulate and understand consistently observed features of the Somali Current system during the southwest monsoon using a two-layer, nonlinear numerical ocean model driven from rest by a uniform south wind in a flat bottom, rectangular geometry. High spatial resolution in both equatorial and coastal boundary regions was retained in this free-surface model. The model Somali Current is best classed as a time-dependent, baroclinic inertial boundary current. Analytical solutions to a quasi-steady linear model of the Somali Current are shown to be self-inconsistent with the linear approximation. While linear theory predicts perfect symmetry about the equator, the nonlinear numerical solutions exhibit marked asymmetries in less than a month as the model Somali Current becomes strongly inertial. By day 30 the current has attained its maximum value (140 cm s−1) within a few degrees of the equator, in accord with observations. In this time-dependent case, boundary layer separation occurs ... Abstract We have sought to simulate and understand consistently observed features of the Somali Current system during the southwest monsoon using a two-layer, nonlinear numerical ocean model driven from rest by a uniform south wind in a flat bottom, rectangular geometry. High spatial resolution in both equatorial and coastal boundary regions was retained in this free-surface model. The model Somali Current is best classed as a time-dependent, baroclinic inertial boundary current. Analytical solutions to a quasi-steady linear model of the Somali Current are shown to be self-inconsistent with the linear approximation. While linear theory predicts perfect symmetry about the equator, the nonlinear numerical solutions exhibit marked asymmetries in less than a month as the model Somali Current becomes strongly inertial. By day 30 the current has attained its maximum value (140 cm s−1) within a few degrees of the equator, in accord with observations. In this time-dependent case, boundary layer separation occurs ...