Overshooting Top Detection in Severe Thunderstorms Using Satellite Imagery in Catalonia: A Comparison with Lightning and Radar Observations

The research consists of the analysis of the detection of overshooting tops (OT) over a period of 10 years using water vapour imagery from a satellite. OT is usually observed in thunderstorms producing severe hail. The results were compared with other remote sensing data (weather radar and lightning) to validate the algorithm and to characterise those severe thunderstorms correctly identified. First, it was observed how the algorithm detects false OT associated with non-convective structures, mainly during the non-warm season. Because the differences between the satellite parameters in well- and badly-corrected overshooting tops are small, with an average minimum brightness temperature difference of less than 2 °C, it is difficult to distinguish correct cases from incorrect ones using satellite imagery alone. For this reason, it is highly recommended to combine it with other data types, as in the present analysis. In warm-season cases, the results show that OT signatures were well identified in most cases, but there are cases with elevated false alarm ratios or low probabilities of detection. Finally, the characterisation of severe thunderstorms combining multiple systems led to the quantification of different parameters from different points of view, showing that TOP45 and electrification provide better results. Events with high electrification occur mainly in the warm season, while those without flashes were detected during the cold season. These results are relevant to improving the forecast of severe events in Catalonia.