Simulating and Tracking a Heavily Rainy Wave over West Africa Using a Modeling Strategy with WRF Model

Abstract:

The last decades, over Sahel, are characterized by a relative recovery in rainfall compared to the long drought, which affected this part of West Africa in the 70s, 80s and early 90s. It is also noted an increase of extreme events, mainly excess of rainfall causing damages to many parts of the Sahel area. In this study, we are focusing on an extreme case, which occurred during September 2009. A deep African Easterly Wave (AEW) crossed the region from Niger to Senegal giving heavy rains along its path with a maximum of more than 260mm in Ouagadougou, Burkina Faso. While continuing its trajectory other strong winds associated with the systems caused other kind of damages. A modeling strategy, based on a moving nest with the Weather Research and Forecast model (WRF-ARW), is used to simulate the system.  The model is run at 27 and 9km respectively for the outer and inner domains. Key parameters are investigated in order to assess the ability of WRF model in simulating the even. The study has shown good performance of WRF in simulating tropical systems. Noted weaknesses are also highlighted in the study, which showed promising results in simulating extremes, hours to days head, in support to early warning systems (EWS) to mitigate the adverse effects of extremes.  This is a key responsibility of National Meteorological Services lacking this capacity in developing countries of West Africa.