Warning value chain assessments for Storms Eunice (2022) and Ciarán (2023): insights and recommendations

This paper assesses the full value chain resulting in the warnings issued in advance of Storm Eunice (18 February 2022) and Storm Ciarán (2 November 2023), focusing on impacts in southern England. Storm Eunice brought wind hazards over a large area, whereas Storm Ciarán’s hazard footprint covered a smaller area, but was more of a multi-hazard event, with wind, rainfall, and landslide hazards. This paper examines the successes, challenges, and lessons learned from these warnings within the warning value chain framework – a concept illustrating the process of warning production as a sequence of expertise sources (components) connected by bridges facilitating bidirectional information exchange. Using a questionnaire from the World Meteorological Organization’s High Impact Weather (HIWeather) Warning Value Chain Flagship Project, this paper offers a detailed assessment of the warning process, covering the full flow of information and decision-making across the value chain. The post-event analysis for these two storms involved diverse participants, including operational meteorologists, hydrometeorologists, civil contingency advisors, and scientists from the Met Office, Flood Forecasting Centre (FFC), and British Geological Survey. The process culminated in a group scoring exercise for each storm and value chain component. This paper presents the results of the two value chain assessments separately, before drawing comparisons. While both storms impacted southern UK, Storm Eunice posed different forecasting and warning challenges. The findings offer valuable insights for improving future warning systems, focusing on three key themes: (1) streamlining information flow, (2) improving warning communication, and (3) enhancing cross-organizational collaboration.