Objective verification for development and monitoring of automated weather forecasts

Objective forecast verification provides the basis to motivate changes to the forecast system. At MeteoSwiss, we are introducing statistical ensemble postprocessing into our automated forecast production. These automated forecasts are accessed by the Swiss general population through the MeteoSwiss website and mobile app and they will form the basis for a range of derived products. Therefore, it is crucial to evaluate the new forecasts broadly, i.e. on the diverse aspects of forecast quality relevant for the variety of products used across all of Switzerland.

The core component of this evaluation system consists of a web portal for interactive visualization of verification measures. This web portal provides the means to compare forecast meteograms at stations with the corresponding observations for a quick visual inspection akin to the information available on the mobile app. In addition, forecast quality of the most recent forecasts is monitored using various verification measures. Finally, re-forecasting with experimental configurations is integrated to produce in-depth reporting on the effect of novel forecasts to support decisions on the development of the forecasting system. To facilitate near real-time analyses, atomic verification scores per meteorological parameter, forecast source, forecast issue time, station, and time are pre-computed and stored in a partitioned database. The partitioning allows for rapid multi-threaded access at analysis time from the interactive web portal. The objective verification is complemented with feedback by forecasters on duty on individual cases during the pre-operational phase of new forecast developments. Here, we will showcase how each of these parts is used to assess release candidates for the automatic forecast production.