Facts + Statistics: Tornadoes and thunderstorms

Tornadoes

A tornado is a violently rotating column of air that extends from a thunderstorm and comes into contact with the ground, according to the National Oceanic and Atmospheric Administration (NOAA). In an average year about 1,000 tornadoes are reported nationwide, according to NOAA. Tornado intensity is measured by the enhanced Fujita (EF) scale. The scale rates tornadoes on a scale of 0 through 5, based on the amount and type of wind damage. It incorporates 28 different damage indicators, based on damage to a wide variety of structures ranging from trees to shopping malls.

The U.S. experiences more tornadoes than any other country in the world, according to a 2013 report by Lloyd’s of London. (See Executive Summary, page 4 of Tornadoes a Rising Risk? for additional findings and statistics.)

2021 Tornadoes: From January 1 to December 14, 2021, there were 1,254 tornadoes in the United States, compared with 1,075 in all of 2020, according to preliminary data from the National Oceanic and Atmospheric Administration (NOAA). Tornadoes killed over 100 people in 2021, including about 90 in the December 10 series of tornadoes. In 2020, 76 people perished in tornadoes.

On the evening of December 10, 2021, a powerful low-pressure system that lifted from the Southern Plains into the Great Lakes and fueled by record-setting warm temperatures and a La Niña weather pattern spawned about 35 tornadoes across six states and killed about 90 people. Hardest hit was Kentucky, where about 75 people were killed and 26,000 homes and businesses were without power, and more than 1,000 homes were destroyed. In addition, six people were killed in Illinois; four in Tennessee; two in Arkansas; and two in Missouri. Although loss estimates will take weeks to tally, insured losses will rank among the top 10 costliest U.S. catastrophes involving tornadoes. According to an Artemis survey of about 1,000 reinsurance and related companies, the majority of respondents (37 percent) estimate the tornadoes will cost $2.5 billion to $5 billion in insured losses, but about a quarter estimated the losses at $5 billion to $7.5 billion and over $7.5 billion, respectively. The costliest catastrophe involving tornadoes occurred in April 2011, when a spate of twisters hit Tuscaloosa, Alabama, and 12 other states, causing $8.5 billion in insured losses in 2020 dollars. The deadliest event in the 2000s was the May 2011 Joplin, Missouri event that took 158 lives.

2020 Tornadoes: In 2020 there were 1,075 tornadoes compared with 1,517 in 2019, which was the highest annual total since 2011, when there were 1,691 tornadoes, according to NOAA. In 2020, 76 people perished in tornadoes compared with 42 in 2019. On April 12 and 13, 30 people perished in tornadoes in Georgia, Mississippi, South Carolina and Tennessee. On March 2 and 3, 25 people were killed in tornadoes in central Tennessee, including the city of Nashville. Tornado deaths in 2020 were the highest since 2011, when 553 people were killed in 1,691 tornadoes.

Insured Losses

Convective storms are the most common and damaging natural catastrophes in the United States, according to the Insurance Information Institute’s May 2020 white paper, Severe convective storms. According to Aon, insured losses in the United States from these storms totaled at least $10 billion each year since 2008. While scientists cannot say that these storms are increasing, it is clear that the losses are increasing, as a result of population growth and economic development. In addition, the geography, frequency and intensity of these storms also may be changing. Aon reports that there were 14 separate billion-dollar economic, or total loss severe convective events in 2020. The most expensive included the August 10 Midwest derecho, or straight lines winds. Aon’s current estimate of insured losses for severe convective storms in 2020 is a record $36 billion. The previous record was $32 billion in 2011.

The United States experiences more tornadoes than any other country. The National Oceanic and Atmospheric Administration notes that tornadoes can happen any time of year. The costliest U.S. catastrophe involving tornadoes, based on insured losses, occurred in April 2011. It hit Tuscaloosa, Alabama, and other areas, and cost $8.5 billion in insured damages (in 2020 dollars). The second costliest was the tornado system from August 8 to 12, 2020 that included the August 10 Midwest Derecho that caused $8.3 billion in insured losses.. (See chart below.) The National Weather Service posts updated information on tornadoes.

Convective storms are the result of warm, moist air rising from the earth, and depending on atmospheric conditions, may develop into tornadoes, hail, thunderstorms with lightning, or straight-line winds. Convective storms are the most common and damaging natural catastrophes in the United States, according to the Triple-I’s May 2020 white paper, Severe convective storms. According to catastrophe modeling company RMS, insured losses in the United States from these storms average about $17 billion each year, nearly equal to the losses incurred by hurricanes. While scientists cannot say that these storms are increasing, given the relatively short periods of reliable, post-Doppler radar data, it is clear that the losses are increasing, as a result of population growth and economic development. In addition, the geography of these storms appear to be changing from what previously was called the “tornado alley” to the southern United States with tornado formation tending to develop further east.

According to Aon, there were 14 separate billion-dollar economic, or total loss, severe convective events in 2020. The most expensive included the August 10 Midwest derecho (straight line winds).

Number Of Tornadoes And Related Deaths Per Month, 2020 (1)

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(1) Excludes Puerto Rico. A tornado that crosses state lines is counted as a single event in this chart.

Source: U.S. Department of Commerce, Storm Prediction Center, National Weather Service.

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The following chart shows the top 10 catastrophes involving tornadoes. It counts severe convective storms that may include tornadoes and other perils such as straight-line winds (derechos) and hail. The August 10, 2020, Midwest Derecho, which is included in the chart as part of the August 8-12, 2020 outbreak, would rank as the fourth-costliest insured severe convective storm event on record for the U.S. if considered alone. It caused $7 billion in insured losses in Iowa, Illinois, Wisconsin and Indiana.

U.S. Tornado Count, 2020

 

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Source: U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Weather Service.

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