Convective Environments Prone to Downbursts, Large Hail, Flash Heavy Precipitation and Tornadoes in Spain

When certain atmospheric conditions are met, deep moist convection becomes prone to severe weather. Identifying these convective environmental conditions is a central objective in severe weather research. This study focuses on the environments associated with severe convective weather over Spain, derived from vertical profiles extracted from the ERA5 reanalysis and combined with cloud‑to‑ground lightning data and public reports of downbursts ( > 80 km/h), large hail (> 5 cm), flash heavy precipitation (> 60 mm/h), and tornadoes. We evaluated the skill of more than 200 convective parameters using threshold‑based binary classifications between each hazard type and non‑severe thunderstorms, assessed through ROC curves. Composite thermodynamic diagrams and hodographs were also constructed for each severe‑weather hazard, permitting a more visual comparison that might be useful to forecasters.

Summer downburst environments are noticeably warmer than those of non‑severe thunderstorms, with DCAPE and freezing‑level height emerging as the most discriminating parameters. Outside summer, downbursts occur in environments with enhanced wind throughout the profile, although wind strength remains below that of High‑Shear–Low‑CAPE severe environments described in the literature. The increased hodograph length in non-summer downbursts is primarily due to strong 0–3 km winds. Large‑hail events occur mostly in summer and are associated with elevated CAPE and wind shear, making them well distinguished from non‑severe thunderstorms by the WMAXSHEAR compound index. Flash heavy precipitation is favored by high parcel moisture content and low‑level saturation. Their hodographs indicate slow storm motions, reflected in reduced Bunkers right‑moving vector, and exhibit a rapid turning in the lowest 3 km. Tornadoes and waterspouts are challenging to distinguish from non‑severe thunderstorms based on convective parameters, showing only modest increases in 0–3 km CAPE, saturation, and slightly lower lapse rates in upper-levels. Composite thermodynamic diagrams and hodographs do not indicate any major distinguishing characteristic.

This study provides a reference framework for identifying the most relevant environmental indicators for future severe‑weather research in the region. It also delivers the first convective‑parameter‑based characterization of downburst environments in Spain, highlighting differences from studies in other regions where alternative parameters have proven more suitable or have shown other typical values.