Modeling studies of tropical cyclogenesis of TC Debby and Helene during AMMA

This study is to elucidate the transition processes from mesoscale convective system to tropical cyclogenesis in West Africa. TC Debby (21 August 06) and Helene (12 September 06) have been investigated using the high resolution WRF-ARW model. These two systems formed from tropical waves coming off the coast of Africa, and were categorized as tropical depressions south of the Cape Verde Islands, notably in close proximity to one another. The synoptic and mesoscale conditions of these two cases will be examined to understand the similarity or vice versa during the transition period. Additionally, the topography effect on the convective activity in West Africa will be investigated.

The model is configured with 20 km and 4 km nested domains. The preliminary findings have demonstrated that high resolution (i.e., 4 km grid spacing) simulation is able to recapture the MCS propagation over the coastal region in West Africa. In order to provide validation of the model simulations of these real cases, the model results will be compared with satellite imagery as well as the in situ measurements from AMMA.