The southwest corner of the basement is not necessarily the safest place because large objects such as motor vehicles can be deposited into basements. You need something sturdy overhead, such as an I-beam. Another better option in the basement is to get underneath a heavy desk or table or the staircase. If you are caught outside in the open during a tornado, try to hide in a ditch or ravine. Lie flat and cover your head.
Any debris driven by tornado strength winds has the potential to cause serious injury.
Never drive directly towards or the vicinity of a tornado. Any tornado can change direction or speed and put you directly in its path. Move away from the tornado or get out of the car and take shelter immediately. Also, never take cover under highway over-passes. The tornadic winds will be even stronger under highway over-passes and you are actually more exposed to flying debris than you are lying in a ditch or ravine.