Explicit risk modelling of sting-jet extratropical cyclones.

Extratropical cyclones (ETCs) are a major hazard for Europe as they cause most of the windstorms and floods in the mid-latitudes, resulting in high economic and social costs.

Sting jets (SJ) are responsible for windstorm damages well ahead the cyclone center. In this study we employ dedicated diagnostics and modeling approaches that identify -along with cyclone tracks- the spatial extent where actual impacts take place. The fine scales of processes involved in SJ generation demand exceptionally high spatial resolutions and dense vertical levels in model simulations (Rivière et al. 2020).

In this study we use the WRF model to simulate 143 historical ETC from 1980 to 2018 that potentially involve SJs. The model simulations use two domains: one parent domain that encompasses the whole cyclone track at a resolution of about 15 km, and another, square-sized domain with each side measuring 1300 km. The nested domain always follows the ETC centers, aiming to resolve explicitly the development of SJs. SJ detection has been achieved through lagrangian modeling, by identifying airstreams that sharply descend ahead of the cloud head and behind the cold front of the cyclones. Historical ETC footprints from ERA-5 and WRF physical downscaling of ERA-5 in convection-permitting resolutions are then used to assess the impact in term of financial losses of an explicit simulation of sting-jets processes.