So it is better to hunt t-storms while standing under the roof.
Safer in a car, I think, at least as long as they still have steel body shells - the metal acts as a Faraday cage & you'll be OK even if the car gets a direct hit. My (convertible) car may not be the best for this purpose as it takes 25-30 secs for the (metal) roof to deploy, if I went storm chasing I'd probably have the roof down for better visibility & would get soaked when the rain starts. Actually in "normal" rain I stay dry so long as I can maintain 50 mph+ as the slipstream deflects the rain over my head, but I'm sure this wouldn't work in heavy thundery rain.