Interesting tidbit of information about trailers and tornadoes from here in tornado alley ...
it's true that trailers are hardly ever as well-anchored into the ground as a house, which makes them generally far more susceptible to high winds, but ...
tornadoes do tend to follow along lower geographic areas ...
and where do you find a whole lotta trailer parks?
Answer: In flood plains and other low-lying areas that are not ideally suitable for building permanent structures.