Application of the warning value chain in designing a new warning capability for the UK

Intense convective storms cause many deaths around the world each year from flash floods, landslides, lightning, tornadoes and hail. These are also some of the most difficult to forecast weather hazards and are generally not predictable in a deterministic sense by Numerical Weather Prediction models. In the UK the incidence of such storms has increased significantly in recent years, as a result of climate change, and is projected to increase further with increasing summer temperatures and corresponding increases in absolute humidity. The current UK weather warning service is focused on providing early warnings of six or more hours lead time to enable people to plan ahead for safety. However, the small spatial and temporal scales of convective storms mean that only a very general probabilistic indication can be given of timing and location in these warnings. As a result, most recipients do not prepare for the possibility of severe impacts, even when the accompanying message indicates that they are possible. One option being considered for enhancing the current warning service is to developed a complementary very short range warning focused on storms that present a risk to life. This implies a particular set of responses from warning recipients which make specific demands on the information communicated and the means of communication. On the other hand, current forecasting capabilities for these storms are limited and there are known constraints to forecast improvement. This presentation will demonstrate how a value chain approach has helped to identify the critical components of such a warning system, mapping them on to existing and projected capabilities. Results of a preliminary feasibility study will be shown.