We conduct a model case study using the non-hydrostatic limited area COSMO model of the German Weather Service (DWD). Our study focuses on the period between 09-16 September 2006. On 09 September, an MCS developed over Burkina Faso within the trough of an AEW and grew rapidly into a mature MCS during the following 12 hours. It moved westwards, reached its maximum strength early on 10 September and then began to decay. New convective systems developed within the AEW as it approached the Atlantic. On 11 September this complex moved over the Atlantic, underwent further development. On 12 September, the system was organised enough to become a tropical depression and it was upgraded to Tropical Storm Helene on 14 September 2006. After steady intensification Helene became a Hurricane on 16 September 2006.
We present results from 72 h model runs initialised from ECMWF analyses on different days within the period of interest. The horizontal resolution is 2.8 km so that the convective parametrisation is switched off. We use the model output to diagnose the interaction between the synoptic and the convective scale over land. Various budgets are calculated (e.g. heat moisture, vorticity) and a potential vorticity diagnosis is carried out. The model results are also compared to observations obtained during the AMMA campaign.