EOF analyses have been performed on the NOAA-OLR data to characterize the intra-seasonal timescale variability of convection during the summer monsoon over West Africa. Three distinct modes have been found. The first one is located near the equator where it develops and decays without any propagation. It is associated with an atmospheric circulation perturbation in the equatorial plane. The second one shows a westward propagation along the Sahelian band and it is associated with cyclonic/anticyclonic circulation patterns at the monsoon level. The third one is stationary along the northwestern coast of West Africa and it is associated with the quasi-stationary trough present at this place. The understanding of intra-seasonal variability of convection over the Sahel during the northern summer need to take into account the contribution of these three independent modes of variability.