MOST tornados skip along the ground, they don't stay on it solidly. Also at least around here most individual funnel clouds only last for a few minutes ... or between 2 to 15 miles, spending most of their time up in the air not on the ground.

The super big ones, like a couple of yesterday's monsters, however can stay SOLIDLY on the ground for a considerable distance. The F5's that hit Xenia Ohio and Whichita Falls Kansas were like that. Each about 1/2 mile to mile across and solidly on the ground for a number of miles. (Probably the same thing happened yesterday - which the weather service will figure out in the next few days).