In recent years, the news has been filled with dramatic reports of devastating tornadoes. From the Joplin tornado in 2011 to this year’s outbreak in Oklahoma, it seems like every year brings reports of terrible devastation from these powerful storms. Are they getting more frequent, or are we just better at detecting them? Are they getting more powerful, or are we just saturated with dramatic video from storm chasers? I thought it might be interesting to look at trends in the number of tornadoes nationally and in Missouri. In this post I will cover some tornado basics. In the next, I will look at trends in the number of tornadoes over time. In a third post, I will look at trends in the most severe tornadoes.

Tornadoes are most common during the spring and summer, but they can occur any time of the year. Texas is the state that experiences the largest number of tornadoes (half again as many as Kansas, which is second), but it is also the second largest state (after Alaska). If you divide the annual number of tornadoes by the land area of the state, the result is surprising. The table below shows the top states in tornadoes per 10,000 square miles of land area. Missouri is 12th.

The most important tornadoes, however, are the large, powerful ones. The National Oceanic and Atmospheric Administration ranks tornado strength on the Enhanced Fujita Scale from 0-5, with 5 being the most powerful. States with the most tornadoes ranked EF-3 to EF-5 are Kansas, Arkansas, and Texas. But again, if you divide by the state’s land area, you get some surprising results. The table below shows the stop states in EF-3 to EF-5 tornadoes per 10,000 square miles of land area. Missouri is tied with four other states for 8th.

Of the 10 most deadliest tornadoes, 3 have involved Missouri. The Joplin tornado, which occurred in 2011, is listed as the 7th most deadly in history. The 3rd most deadly tornado struck St. Louis in 1896. And the deadliest tornado in history was the Tri-State Tornado of 1925. It touched down near Ellington, in Reynolds County, MO. It travelled northeast, crossing the Mississippi River, traveling completely through Illinois, , finally dissipating about 3 miles southwest of Petersburg, Indiana. The total track was 219 miles in length with an average width of 3/4 of a mile. Some 695 people were killed, and 2,027 injured.

Sources:

For national and state tornadoes: U.S. Tornado Climatology, National Climate Data Center, http://www.ncdc.noaa.gov/oa/climate/severeweather/tornadoes.html#history.

For the Tri-State Tornado: 1925 Tri-State Tornado: A Look Back, Paducah, KY National Weather Service Weather Forecast Office, http://www.crh.noaa.gov/pah/?n=1925tor.