A radar analysis of two giant hailstones in Catalonia

Hail events are common in Catalonia (NE of the Iberian Peninsula). The first two giant hailstones (with diameters equal to or exceeding 10 cm) occurred in this region in 2022 and 2023. These occurrences align with the hypothesis that extreme severe weather events have increased with rises in air and sea surface temperatures. This behavior coincides with the pattern observed in most of regions around the World.

The research presented here focuses on the thunderstorm characteristics of both cases as observed by the weather radar network of the Servei Meteorologic de Catalunya. Regarding the volumetric structure, the giant hail-bearing storms exhibited dimensions unprecedented in Catalonia, as it is observed from the analysis comparing with a set of more than 200 different cases.

We have compared these two events with the rest of the hailstorms set in terms of affected area, duration, dimensions, or life cycle evolution. The study was conducted using a high-resolution 3D grid of 1 km per 1 km per 0.5 km. This grid enabled the identification of the most relevant elements associated with the reflectivity fields in each case.

Furthermore, we sought general parameters through initial automatic identification and characterization algorithms, allowing us to determine reflectivity distribution along the vertical, which has been compared also with lightning data. Additionally, we conducted more in-depth analyses for certain life cycle instants with particular elements, such as a change in the nature of the storm, the inclination, or the observation of concrete elements such as the three-body scatter spike, the boun weak echo region, or the hook echo.