Tornadoes and mobile homes?

The devastation is unbelievable with the tornadoes.What do you do if you live in a mobile home (one that is not tied down,but sitting on blocks) and the siren goes off for a tornado?how do you know if you should get in your car and head directly to the local storm shelter in town (with children) what if your all by yourself with your kids,what do you do and when do you do it? never been in a tornado so that's why I ask