Explosion in the sky caused by lightning

[Ivan Seeking]

"In addition to the usual fare that comes with a thunderstorm, many on the city’s Northeast Side witnessed an unusual dark circle in the sky, which turned out to be a ring of smoke that a weather official said emanated from an 'explosion caused by lightning'".

http://news.mysanantonio.com/story.cfm?xla=saen&xlb=180&xlc=1022772

[Tyger]

I've actually put up a post describing a detector for just such rings as these. See the second post on this thread.

http://www.physicsforums.com/showthread.php?s=&threadid=2017

[Ivan Seeking]

A follow up to the story:

http://www.woai.com/news/local/story.aspx?content_id=ABC2A860-778F-48BC-B92E-1B9C33EC7F51