breaking news, gofrper mitt romney's campaign announced late this evening he will reveal his choice for vice president tomorrow morning in virginia. "good morning america" will have the news as it develops. but we turn now to the summer of wild weather. the hottest july on record, crippling drought in half of the country and now tropical storms bringing epic rains to the east coast. ji ginger zee has been out storm chasing. >> reporter: we're chasing one of nature's most destructive and unpredictable forces. >> oh, look at that. that was beautiful. >> reporter: tim samaras is a seasoned storm chaser and no stranger to wild weather. >> most of the core i believe is right here. >> reporter: but today he's focused on another nearly impossible mission. he's attempting to document the birth of a lightning strike. tim wants a glimpse behind that blazing flash he believe this is moment holds the clues that will help us better understand the mystery of this lethal phenomenon. armed with an ultra high speed camera. >> a shot we just got. >> reporter: cool. oh, my gosh. he will try to capture thi