Andrew Hall has hypothesized that plasma flow has a large part to play in thunderstorm formation and tornados. These surprising gamma rays mentioned in the article would seem to support Hall's hypothesis.

Hall's theories are well outside of the mainstream and I don't know his credentials, if any, and cannot speak to his hypothesis's veracity. I'm not a scientist. Would any actual scientists care to comment?

Here is a video where he explains his theory: https://www.youtube.com/watch?v=DU706V0bltc