My favorite article about tornados answers this question best. “A common belief is that since most tornadoes in the U.S. travel from west-southwest to east-northeast, the southwest side of the basement is the safest place to hide out.
The originator of this advice may be John Park Finley, one of the first serious meteorological researchers who studied hundreds of tornadoes in a career spanning the late nineteenth and early twentieth centuries. Finley said you should never take refuge in the east side of a basement, and specifically warned against the northeast corner — he reasoned that debris from the house would be blown in that direction.” Guess what? In 1966 it was proven wrong by Joe Eagleman of the University of Kansas. He studied the wreckage of the EF5 Topeka tornado of that year and concluded that if you had a full basement, the northeast corner was the safest place to be and the south side the most dangerous. Why? External debris knocked down southern walls and blew in through south-facing basement windows; when winds shifted the whole house to the northeast, the southwest corner of the basement was where the upper stories fell in. There is no best place in the basement unless you have a reinforced section built exclusively for this occasion. A basement, however, is the safest place to be in general if you don’t have an underground shelter.
“The Straight Dope” by Cecil Adams written July 29, 2011