Analysis of radar observations suggest that most of the rainfall in Niamey during the AMMA IOP was associated with large convective systems, observed to begin in the second week of July as the monsoon was established. These large systems were organized as squall line mesoscale convective systems (SLMCS) with large trailing regions of stratiform rain and propagated westward every 2-3 days. The radar observations also show that during the IOP, SLMCS usually passed through Niamey in the early morning hours. SLMCS observed with the MIT radar in Niamey corresponded well with rainfall events in the GPCP rainfall dataset. In the large-scale, the NCEP Reanalysis 700 mb vorticity fields suggest a strong connection between African easterly waves and the westward propagating SLMCS observed by the radar.