Synoptic Analysis of Extreme Rainfall Event in West Africa: the Case of Linguère

Abstract

After the drought period of the 70s and 80s, the Sahelian countries have experienced a resurgence of heavy rains phenomena and devastating floods causing a lot of socio-economic damages since the beginning of the 21st century. In this work, the environmental conditions associated with an extreme rainfall event that has led to high socio-economic impact in Senegal is studied by using the database of the extreme event from the DPC (Direction de la Protection Civil) of Senegal, Satellite products, ERA-Interim reanalysis and five Weather Model Prediction datasets. The rain event occurred on 26 August 2017 at Linguere (15.07°W and 15.23°N). This study aims to analyse the synoptic conditions associated to the event and also the ability of the numerical forecast models to predict it. The satellite dataset shows that the precipitating convective system was initiated at the level of a trough, on August 25 in the afternoon, and the extreme rain event took place on August 26 between 0600UTC and 1200UTC over Linguere. Various atmospheric parameters such as the configuration of the low-level moisture transport, precipitable water, relative humidity at 200 and 700-hPa as well as relative vorticity at 700-hPa appear as good indicators to characterize extreme rainfalls. The numerical forecast models used were able to predict short-term rainfall around Linguere. However, none of the models could predict the extreme aspect of precipitation because they tend to underestimate the intensity compared to rain gauge records.