The numbers of SCTDs were largest at the Tartu and Voru stations, 116 and 153, respectively.
In more than 2/3 of the SCTDs cases, the centres of SCs were closer to the stations than 500 km.
As expected, the monthly distribution of SCTDs (Fig.
A significant decrease in the frequency of SCTDs (p < 0.
01) relationships between the frequencies of SCTDs and other TDs over the stations (r = 0.
Similar proportions were observed in case of SCTDs when thunder was registered at least at one station.
Correlation analysis revealed statistically significant relationships between the frequencies of SCs and SCTDs, as well as between the frequencies of TDs related to SCs and other TDs.
The only statistically significant trend of SCTDs was detected in August.
At a distance up to 500 km, there were more SCTDs in case of WSCs than in case of ESCs.
Still, we can state that thunder events caused by SCs tend to last longer in July than, for example, in August when there is the maximum of SCTDs.
In general, the stations with more thunder also record more SCTDs.