摘要：A major linear mesoscale convective system caused severe weather overnorthern France, Belgium, the Netherlands and northwestern Germany on3 January 2014. The storm was classified as a cold-season derecho withwidespread wind gusts exceeding 25 m s−1. While such derechosoccasionally develop along cold fronts of extratropical cyclones, thissystem formed in a postfrontal air mass along a baroclinic surface pressuretrough and was favoured by a strong large-scale air ascent induced by anintense mid-level jet. The lower-tropospheric environment was characterisedby weak latent instability and strong vertical wind shear. Given the pooroperational forecast of the storm, we analyse the role of initial and lateralboundary conditions to the storm's development by performingconvection-resolving limited-area simulations with operational analysis andreanalysis datasets. The storm is best represented in simulations with hightemporally and spatially resolved initial and lateral boundary conditionsderived from ERA5, which provide the most realistic development of theessential surface pressure trough. Moreover, simulations atconvection-resolving resolution enable a better representation of theobserved derecho intensity. This case study is testimony to the usefulness ofensembles of convection-resolving simulations in overcoming the currentshortcomings of forecasting cold-season convective storms, particularly forcases not associated with a cold front.
