Ensemble Anomaly Forecasting approach to predict extreme weather demonstrated by Beijing July 21, 2012 extreme heavy rain event

Even if a numerical weather prediction model is capable of predicting an extreme weather event, there are several difficulties associated with such a forecast, i.e. how confident is the prediction of the extreme event and how reliable is information related to details such as timing, location and magnitude? In this paper, a method called “Ensemble Anomaly Forecasting”, which combines ensemble forecasts with climatology, is introduced and demonstrated using the Beijing July 21, 2012 extreme heavy rain case. The results show that these two challenging difficulties can be effectively alleviated through this method and ensemble forecasts by providing more reliable and consistent information than a single forecast could provide. Therefore, we strongly recommend forecasters to apply this method in their daily operations to improve their capability in predicting rare high-impact weather events.