Ok, try this. Make a new solid and mask out a hollow loop in the general shape of your tornado as seen from the top. Make the anchor point slightly off center and animate the loop to rotate for a bit longer than you’ll need it to. Then apply a wiggle expression to your solid. Pre-comp the solid (this might not be necessary, but I’m not sure) then make the pre-comp 3D. Rotate it to where you want it (the top of the tornado). Then duplicate it many times (20 or more, probably) and adjust the position and scale so that each one down is a little smaller. You will also need to apply some color correction to vary the color from black to gray to white (or brown). Then move the entire clip of each duplicate a litte forward/backward in the timeline. If you stagger them you might be able to get a wavy effect. This is hard to explain, so if you have questions ask. I will probably try this myself tomorrow (I don’t have AE on this computer) and see if it actually works!