RainBoW's first increment: Renewing the weather warning system at the German Meteorological Service one step at a time

The German Meteorological Service (Deutscher Wetterdienst, DWD) is renewing its weather warning system through a dedicated program called RainBoW ("Risk-based, Application-oriented and INdividualizaBle Provision of Optimized Warning Information"). With the overarching goal to more strongly support informed decision-making in the face of significant weather situations, we are specifically working to improve the comprehensibility of warnings to make them more effective, and to extend their forecast horizon to give recipients more time to act. Additionally, targeted at users with specialized warning requirements, we aim to enable the individualization of warnings. 

RainBoW's outcomes will be released gradually. The first increment focuses on the goal to improve the comprehensibility of warnings for the general public, which includes the introduction of a consistent warning criteria catalogue. DWD's warnings currently operate on a four-level scale, but the amount of available levels varies between warned weather elements. For example, there are four warning levels for wind gusts, while only three are used for rain. Moreover, the current least severe level does not always represent hazardous weather, which might lead to unnecessary alarmism. To address these discrepancies, we plan to introduce a three-level system with a consistent semantic definition for each of the levels. A second aspect to advance the comprehensibility of warnings is a restructured warning text with a focus on potential weather impacts and recommended actions, which we also plan to release within the first increment. 

Besides this, RainBoW's first increment will address the goal of extending the forecast horizon of warnings, initially focussing on thunderstorm warnings. Currently, warnings are issued once a thunderstorm is detected by nowcasting systems, resulting in very short lead times. In case of expected severe thunderstorms, a pre-warning is provided earlier, but this is not the case for all available warning levels. To bridge this gap, we plan to introduce a new thunderstorm warning, which uses the forecasted thunderstorm potential as a base instead of the immediate detected thunderstorm in nowcasting. These new thunderstorm warnings are intended to provide earlier information before a short-notice warning is issued, which is at the same time more reliable than the pre-warning.   

While the first increment focusses on the goals to improve the comprehensibility of warnings and to extend their forecast horizon, we are also working on RainBoW's upcoming increments. Amongst other improvements, this comprises advancing the individualization of warnings via the so-called warning portal ("DWD-Warnportal"), and the implementation of an automatic warning trend covering up to seven days. 

This contribution will go into detail concerning the contents of the first increment, and will give a brief overview of other ongoing work within RainBoW.