Cloud-to-ground (CG) lightning flash characteristics and radar data were examined for a thunderstorm with large hail and high reflectivity values (> 70 dBz) that occurred on 29 December 1997 in the Bethlehem (South Africa) area. Radar CAPPIs (constant altitude plan position indicator) at the 6 km level, obtained from the Russian MRL5 radar were used. The lightning data were obtained from the LPATS (Lightning Positioning and Tracking) detection network.
Time series were constructed of lightning and reflectivity over the whole lifetime of the storm. The storm produced a total of 3017 flashes of which 85.9% were negative. As the storm matured, the fraction of positive flashes increased, while there was a maximum in both negative and positive flashes in the dissipating stages of the storm. The mean and peak CG flash rates were higher than those that occur in an average Highveld thunderstorm, while the mean and peak signal amplitudes were about the same as those for a Highveld storm. The 5-minute flash frequency corresponded the best to the area covered by reflectivity for the 40 - 49.9 dBz interval over time.
The high hourly percentage of positive CG lightning at the later stages of the storm as well as the high mean and peak flash rates were the same as those for severe storms and can explain the occurrence of large hail in this thunderstorm.
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