I created a tornado which is a model that has smoke parts in it and a part named Car1 that supposed to move the whole thing to random positions with bodygyro, and a long part that kills players if they touch it. Everything works fine the smoke, the player kill, but it does not move. I made a model of it if anyone is able to help me: https://www.roblox.com/Tornado-item?id=466488703
First off, in your script, the property velocity is deprecated in favor of Velocity, that means the "velocity" should be replaced with "Velocity".
Note: in the script, I noticed that you're only moving a single part within the model. Possibly find/make a tornado mesh and use that?
So, from what I know, BodyGyro and BodyVelocity wont help if the part isn't anchored, so I unanchored it, and it did exactly as the note says. Adding on, all the other parts fell onto "Car1". So again, try a mesh.
Best wishes!