I haven't had any visions as in suddenly going from a normal wakeful state to something else entirely, but I have had dreams with a recurring symbol: tornadoes. In the dream they've never been a negative idea. Everyone else around me is freaking out, but I want the tornado. It's always precluded by pictures and associations of normal tornadoes (bunch of wind, destruction...) but the image itself is always completely different. It's like the power of a tornado made solid, and its dripping/flowing/growing down, kind of like an icicle. I can feel the sheer power in it, and always long to reach out and let it grow into me, but I've never been given that opportunity. the first time, I woke up with it 6 inches (13cm) away from my hand, the second time, it had barely touched my foot (I don't understand why, but in the dream I was inside being forced [<- very specific word choice] to get under protection, and it was my foot that was facing the tornado) I felt what was like a slight pinch in my foot, and I woke up. I still long for a dream where I actually get to touch the tornado and let it do its thing to me.
As you can see I have a very strong affinity with the element Air, these dreams, my magickal name (wind of the night), my very disposition. I really want to find out what happens with this tornado.