ECSS2023-70
https://doi.org/10.5194/ecss2023-70
11th European Conference on Severe Storms
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Enhanced climatology of large hail in the UK: Radar-derived diurnal cycle and storm mode

Henry Wells1, John Hillier1, Freya Garry2, Nick Dunstone3, Huili Chen4, Abdullah Kahraman5,3, William Keat2, and Matthew Clark2
Henry Wells et al.
  • 1Department of Geography and Environment, Loughborough University, Loughborough, United Kingdom (h.m.wells@lboro.ac.uk)
  • 2Met Office, Exeter, United Kingdom
  • 3Met Office Hadley Centre, Exeter, United Kingdom
  • 4School of Architecture, Building and Civil Engineering, Loughborough University, Loughborough, United Kingdom
  • 5School of Engineering, Newcastle University, Newcastle upon Tyne, United Kingdom

Large hail, with a diameter of at least 20 mm, is a hazard associated with severe convective storms (SCS) that can cause significant damage. Understanding of atmospheric environments conducive to large hail is underpinned by catalogues of past events. Because of the small footprint of hail events, these often rely on crowdsourced reports. In the UK, the relative rarity of large hail and low public awareness of SCS hazards makes obtaining a complete set of reports difficult, and in many cases the precise time of the hail is not recorded. In this study, the two major databases of UK large hail reports are merged for the first time. Composite radar reflectivity data are used to verify and enhance 260 reports since 2006. Time of the hail and the basic storm mode (isolated, clustered or linear) are visually estimated from animations. Compared to the UK’s most severe historic hailstorms (1800–2004), our quality controlled climatology of all sizes of large hail shows a diurnal cycle with a slightly broader peak. Around 55% of large hail events are associated with isolated cells, while 34% have supercellular characteristics, a much lower proportion than found in the USA. The full event set (1979–2022), comprising over 850 reports, is used to update the seasonal, spatial and size distributions of large hail in the UK. We intend that this hail event set forms part of a multi-hazard analysis of UK SCS, also including tornadoes and extreme rainfall, and its relationship to background atmospheric conditions. The effect of climate change on UK SCS will be investigated through past and future trends in these background conditions.

How to cite: Wells, H., Hillier, J., Garry, F., Dunstone, N., Chen, H., Kahraman, A., Keat, W., and Clark, M.: Enhanced climatology of large hail in the UK: Radar-derived diurnal cycle and storm mode, 11th European Conference on Severe Storms, Bucharest, Romania, 8–12 May 2023, ECSS2023-70, https://doi.org/10.5194/ecss2023-70, 2023.