Potential impact of a near-surface baroclinic boundary on supercell intensification: A case study from Hungary on 24 April 2022

Abstract

On 24 April 2022, a low-topped supercell developed in northeastern Hungary along a near-surface thermal boundary that separated a warm, dry air mass to the south from a cool, moist air mass to the north. The storm produced large hail (>2 cm) and damaging winds (>25 m s⁻¹). To assess the role of the thermal boundary in this case, we analyzed the convective environment based on surface observations and examined the evolution and intensification of the supercell along the boundary using Doppler radar data. To further investigate the role of the boundary in the intensification of the storm, a one-way nested high-resolution numerical simulation was performed using the Weather Research and Forecasting (WRF) model with 600 m horizontal grid spacing. Lagrangian diagnostics were used to quantify baroclinic and tilting contributions to horizontal vorticity generation along parcel trajectories, while Eulerian fields characterized the spatial structure of the boundary. Between 1230 and 1250 UTC, most inflow parcels passed through or near the boundary before entering the supercell updraft. During this period, the baroclinic term was approximately two orders of magnitude larger than the tilting term. Moreover, the cumulative baroclinic contribution approached the total amount of absolute horizontal vorticity present in the parcels by the end of the trajectory period, underscoring its dominant role in the generation of inflow vorticity. Given the complexity of supercell dynamics, no final conclusions can be drawn; however, the results point to the thermal boundary as a major contributor to near-surface baroclinic horizontal vorticity. Parcels that traversed this zone appear to have imported substantial amounts of horizontal vorticity into the supercell inflow, which likely supported the development of a stronger low-level mesocyclone through subsequent tilting and stretching processes. These findings highlight the potential influence of mesoscale thermodynamic boundaries on storm evolution, particularly in regions with complex terrain and convective variability.