Historically , the number of tornadoes globally and in the United States was .
Is likely underrepresented : research by Grazulis on annual tornado activity suggests that , as of 2001 , only 53 % of yearly United States tornadoes were officially recorded .
Historically , the number of tornadoes globally and in the United States was and is likely underrepresented : research by Grazulis on annual tornado activity suggests that , as of 2001 , only 53 % of yearly U.S. tornadoes were officially recorded .