Oh, what a shot. I'd guess from the looks of this that this is a scary looking cloud. Although It has an enlongated shaft and dipped down some, it doesn't appear to be rotating, and the main shaft of the thunderstorm doesn't look like the average meso. Did it change into one later on?
This is a rather old pic, shot over my grandparents dairy farm, not sure how much of a wider view I have of it and it was too long ago now to remember too well as per progression, but similar storms produced a lot of lightning and a fair bit of torrential rain at times. It wasn't uncommon to have 150-300mm of standing water in places on the farm after a big drop and the watercourse up the back of the property used to overflow its banks on many occasions.