AR-CHaMo probabilistic forecasts of convective hazards with ECMWF ensemble

Convective hazards pose a significant threat to society and are among the most challenging phenomena for forecasting. The increasing spatial and temporal resolution of (European Centre for Medium-range Weather Forecasts) ECMWF Forecasting system makes it increasingly more suitable for applications targeting severe convection. The European Severe Storms Laboratory (ESSL) has developed additive logistic regression models (AR-CHaMo) for hail and severe convective wind gusts using the ERA5 re-analysis, observations of lightning and severe convection from around the world. ECMWF and ESSL collaborate in a project to apply AR-CHaMo to the ECMWF ensemble (ENS) to provide global predictions of convective hazards in the medium range. Probabilistic products for large hail and severe wind gusts from ENS are undergoing thorough testing, evaluation and skill assessment. Latest results suggest that AR-CHaMo forecasts on ECMWF ENS provide skilful predictions of large hail and severe wind gust risk many days in advance. ESSL and ECMWF continue to refine and develop these probabilistic products by testing more predictors, extending training datasets and including more convective hazards such as tornadoes. These products are already available via the ESSL’s Weather Displayer and are undergoing testing during the regular annual Testbeds. Evaluation of AR-CHaMo forecasts has also been performed internally at ECMWF on a number of severe convection events. The use of the ECMWF’s Integrated Forecasting System (IFS) model levels is capable of providing more accurate predictors and hence better probabilistic AR-CHaMo forecast.