Role of coastal topography in pre-tropical cyclone disturbance formation

Mesoscale Convective Systems (MCSs) are the primary source of rainfall in the Sahel region of West Africa. These MCSs may strengthen over the ocean and transition into tropical cyclones. MCSs in this region are associated with the inland intrusion of southwesterly monsoon winds during late summer and early fall. MCS formation is observed in the convergence zone between this moist, monsoonal flow and the easterly winds inland.

We hypothesize that the mountains to the south of Senegal, in Guinea, Sierra Leone, and Liberia have a modulating influence on MCS development in this region. A secondary topographic element of importance is the highlands just northeast of Senegal in Mauritania.

In late August 2006, a MCS developed over West Africa. It transitioned from land to ocean on 31 August, and days later became a tropical cyclone, eventually strengthening into Hurricane Florence. We use a series of idealized sensitivity studies to examine the influence of the topography on the initiation and development of the pre-Florence MCS using the Weather Research and Forecasting (WRF) model.