Tornadoes are too small of a weather system to be affected by the Coriolis Effect. Hurricanes are affected, but they are on a massive scale compared to tornadoes. Fun Fact: drains and toilets can rotate the water in either clockwise or counter-clockwise directions based on the shape of the drain. it is also possible to make them not spin the water at all. Dam overflow siphons work that way to minimize water turbulence and wear on the structure.