"Movement maketh the MCS": What dynamical factors trigger thunderstorm initiation in West Africa?*

Mesoscale convective systems (MCSs) are thunderstorms up to hundreds of kilometres in size which can have devastating impacts. They dominate the weather systems in West Africa, where they contribute up to 90% of the rainfall in the region during boreal summer, but currently it is very difficult to forecast when they will initiate and where. New developments in regional convection-permitting models have improved representation of these systems, with more realistic distributions of MCSs with more comparable sizes and speeds to those observed using satellites. Such models are an excellent tool to explore the dynamics of MCSs in more detail.

Previous studies have indicated that MCSs over West Africa can be triggered by synoptic and local convergence fields, and studies of MCSs on other continents have shown that new storms can be initiated by vortices that remain after existing MCSs have dissipated. Using CP4-Africa, a convection-permitting regional climate model, and a dataset of tracked storms in the simulation, we investigate what dynamical factors are most strongly associated with MCS initiation. Determining the dynamical environment in which storms initiate could be crucial to improve forecasting of such systems in operational models.