I'm not doubting their findings, but I thought of 'dry lightning'.

["In other words, it may be raining here, and the bolt would shoot out five miles (eight kilometers) from where the rain is and hit the ground where there is no rain. And we see a lot of that this year in the West," said Fire Team Section Chief Ray Johnston.

A bolt of lightning is about as wide as a human finger.

Negatively charged lightning, the most common kind of lightning in thunderstorms, lasts about 41 microseconds or 41-millionths of a second.

But almost every positively charged lightning bolt, the kind most often associated with "dry lightning, lasts up to a full half a second longer -- zapping the ground with a 30,000 degree burst of what scientists call "continuing current."]

From a very good article on dry lightning from CNN.com

More shuttle views of lightning from space (red sprites, blue flashes...) here.