Polarimetric Radar Observations of a Tornadic Supercell in Jersey, Channel Islands, on 1 – 2 November 2023

Abstract: At approximately midnight on 2 November 2023, a strong tornado affected parts of Jersey in the Channel Islands. The tornado occurred in a thunderstorm that formed close to the cold front of an intense extratropical cyclone, named “Storm Ciarán” by the Met Office, which produced widespread damaging winds over northern France and adjacent areas. The tornadic storm passed within a few kilometres of the Doppler, polarimetric, C-band radar located on Jersey. In this presentation, radar observations of the storm will be explored, making use of Doppler, polarimetric and conventional radar parameters. Evidence of a debris signature in the polarimetric fields and an associated debris ball in the reflectivity field will be presented. These data represent the first documented observations of a polarimetric tornado debris signature in the British Isles. The structure of the tornadic part of the storm will be explored by construction of vertical sections using available plan-position-indicator scans at several elevation angles.

Biography: Matt works in the Nowcasting team at the UK Met Office, developing tools to aid in situational awareness and nowcasting of convection. Matt recently completed a PhD at the University of Leeds, exploring the situations in which cold-frontal tornadoes occur in the UK and Ireland. Latterly, Matt has constructed a climatology of convection associated with flash-flooding in the UK, exploring the typical environments, radar-observed storm morphologies and other characteristics of these events, with a view to advancing understanding and suitable approaches for the nowcasting of these storms in the UK.