Analysis of tropical high impact weather events using TIGGE data

Forecasting high impact weather events in tropical regions and the possible ranges of intensity or evolution that can be supported by the large scale environmental conditions is essential. Important guidance for this can be obtained from ensemble forecasts. An empirical orthogonal function (EOF)- and fuzzy cluster analysis is performed to examine data from several THORPEX Interactive Grand Global Ensemble (TIGGE) ensemble prediction systems in order to examine the information contained within the models.

In a case study of an intense African easterly wave (AEW) that caused major flooding in Ouagadougou, Burkina Faso, it is shown that this method can be used to identify distinct AEW scenarios that are contained in the ensemble data. The results indicate the possibility for the occurrence of heavy precipitation already four days in advance, and become the most likely scenario by two days before the event evolved.

Examples for a variety of event types – including more recent intense precipitation events from 2012 and 2013 affecting West Africa in association with AEWs, and tropical cyclone Haruna (2013), which affected Madagascar – will be shown to illustrate how this coarse grid-resolution data can be used to identify these types of events, and to provide suggestions on how TIGGE data could be used for downscaling purposes.