The journal Earthsky says the occurrence is very rare. “It was sheer luck to catch that bolt – surely a once-in-a-lifetime encounter. There were only three visible and audible strikes during that storm, many minutes apart,” said Lowenstein.
The strike is known as a positive cloud-ground (CG) strike. Apart from being much less common than normal negative lightning, positive lightning is very energetic with discharge currents exceeding 100,000 amperes (compared to less than 30,000 for negative strikes).