Inferring the Severity of a Multicell Thunderstorm Evolving to Supercell, by Means of Radar and Total Lightning

Abstract

This study analyzes a long-lived thunderstorm with supercell characteristics that took place in the northeastern Iberian Peninsula on 5 July 2012. Severe weather features identified in Doppler radar and total lightning data have been used to infer the severity of this large-hail-bearing storm that substantially damaged local agriculture. Key elements identified in the radar product analysis were: relatively short development time, a long mature phase lasting >2 h, and high and sustained values for most of the radar parameters (reflectivity, vertically integrated liquid, echo tops), which showed an evolution from multicell to supercell structure. Nevertheless, the most significant patterns were the vertical lifting of the cell core, the three-body scatter spike, the bounded weak-echo region, and the anticyclonic rotation, observed in the Doppler velocity fields. Key features identified in the lightning analysis were: 1) the total lightning “jump” as an early sign for severity, 2) the low negative cloud-to-ground (CG) flash rate and 3) the low intensities in negative CG strokes and the regular rate of positive CG as indicators of complexity in the electrical structure. Finally, data strongly suggest the worst damage occurred when the thunderstorm was in its supercell stage. This case study presents one of the first documented supercells in the region.