Evaluating sub-kilometric simulations in the HARMONIE-AROME model on high-impact convective storms

Very high-resolution and sub-kilometric numerical weather simulations are becoming increasingly common, driven by advances in computational power and atmospheric modeling techniques. These finer-scale models offer the potential to more accurately represent small-scale processes, such as deep convection and storm dynamics, which are often poorly resolved in coarser operational models. As this modelling capability grows, it is crucial to rigorously evaluate the performance of these high-resolution simulations, particularly in reproducing high-impact weather events.

In this study, we assess the capability of sub-kilometric simulations to realistically represent severe convective storms over different regions of Spain. We focus on different selected high-impact weather cases where the operational HARMONIE-AROME model, running at a horizontal resolution of 2.5 km, failed to adequately simulate convective storm development. In contrast, the sub-kilometric simulations successfully captured key storm features, offering improved representation of storm intensity, structure, and evolution. The selected cases span a diverse range of convective phenomena, including supercells, mesoscale convective systems, and ordinary thunderstorms.

Additionally, we aim to support the development of robust conceptual models for forecasting severe convection. These models are grounded in the detailed output from high-resolution simulations and are intended to enhance the forecaster’s ability to anticipate and interpret complex storm behavior in real-world scenarios.