List of the most powerful 25 tornadoes in US:



25. Udall, KS 5/25/1955; 80 dead 1948-1959

24. Lorain/Sandusky, OH 6/28/1924; 85 dead 1926 !

23. Starkville, MS to Waco, AL 4/20/1920; 88 dead 1914-1924

22. Worcester, MA 6/9/1953; 90 dead 1948-1959

21. Natchez, MS 4/24/1908; 91 dead 1904-1914

20. Camanche, IA/Albany, IL 6/3/1860; 92 dead 1853-1863

19. Snyder, OK 5/10/1905; 97 dead 1904 !

18. Poplar Bluff, MO 5/9/1927; 98 dead 1926 !

17. Gainesville, GA 6/1/1903; 98 dead 1904 !

16. Marshfield, MO 4/18/1880; 99 dead 1882 !

15. Shinnston, WV 6/23/1944; 100 dead 1937-1948

14. Mattoon, IL 5/26/1917; 101 dead 1914-1926

13. Omaha, NE 5/23/1913; 103 dead 1914 !

12. Goliad, TX 5/18/1902; 114 dead 1904 !

11. Waco, TX 5/11/1953; 114 dead 1948-1959

10. Flint, MI 6/8/1953; 116 dead 1948-1959

9. New Richmond, WI 6/12/1899; 117 dead 1893-1904

8. Amite, LA/Purvis, MS 4/24/1908; 143 dead 1904-1914

7. Joplin, MO 5/22/2011; 158 dead 2011 !

6. Woodward, OK 4/9/1947; 181 dead 1948 !

5. Gainesville, GA 4/6/1936; 203 dead 1937 !

4. Tupelo, MS 4/5/1936; 216 dead 1937 !

3. St. Louis, MO 5/27/1896; 255 dead 1893-1904

2. Natchez, MS 5/6/1840; 317 dead 1843 !

1. Tri-State (MO/IL/IN) 3/18/1925; 695 dead 1926 !

Look at the right parts of lines with tornado info. We see that powerful tornadoes happened when SMF=0 or between two years with SMF=0, close to the middle.

Current tornado is happened at 2020 when SMF=0!