Bullets just don't have the punching power to stop a twister. You need to load an 18 wheeler box trailer full of TNT. Setup a remote driving capability in the tractor and put the truck on a course in front of the tornado path. Rig up a remote detonator and when the twister is just enough away to not move the trailer, click the red button.
The shockwave should disrupt the part of the cone touching the ground. If that doesn't work, then send in a B-2 with a nuke.
