Tornadoes and Thunderstorms
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.)
THE FUJITA SCALE FOR TORNADOES
Tornadoes accounted for 37.2 percent of insured catastrophe losses from 1994 to 2013, according to Property Claim Services (PCS). In 2013 insured losses from U.S. tornadoes/thunderstorms totaled $10.3 billion, down from $15 billion in 2012, according to Munich Re. The number of tornadoes dropped to 908 in 2013 from 939 in 2012, according to the National Oceanic and Atmospheric Administration (NOAA). There were 55 direct fatalities from tornadoes in 2013, down from 70 in 2012, according to NOAA. May was the top month for tornadoes in 2013, with 268 tornadoes. These figures do not include tornadoes that cross state lines.
The costliest U.S. catastrophe involving tornadoes, based on insured losses, occurred in April 2011. It hit Tuscaloosa, Alabama, and other areas and cost $7.5 billion in insured damages in 2013 dollars. That event was the 10th costliest U.S. catastrophe, based on insured losses, according to PCS. The second costliest catastrophe involving tornadoes, based on insured losses, struck Joplin, Missouri, and other locations in May 2011. The catastrophe cost $7.1 billion in insured losses in 2013 dollars. (See chart below.) The National Weather Service posts updated information on tornadoes.
THE 2014 TORNADO SEASON
Preliminary NOAA data show that there were 831 tornadoes in 2014 through October 27, compared with 811 during the same period the previous year. On April 27, 30 tornadoes formed in at least seven states (Arkansas, Iowa, Nebraska, Kansas, Oklahoma, Mississippi and Louisiana). Nineteen fatalities were reported. Many homes and buildings were damaged or destroyed in Arkansas, Oklahoma and Kansas, according to the Federal Emergency Management Agency.
THE 2013 TORNADO SEASON
A large outbreak of over 60 tornadoes hit the Midwest and southern Great Plains from May 18 to 20, including an EF5 tornado (the most powerful category) that hit Moore, Oklahoma. Thousands of homes and other buildings were destroyed. According to Munich Re, overall insured losses from the outbreak were estimated to total $1.8 billion.
From May 28 to 31 another large outbreak occurred over the southern Plains. The area near El Reno, Oklahoma, was hit by an EF3 tornado that had the largest diameter ever observed in a tornado, 2.6 miles. Overall insured losses from the outbreak were estimated at $1.4 billion by Munich Re.
From November 16 to 17 a strong storm system hit the Midwest, causing at least six deaths, according to the National Weather Service (NWS). The NWS estimates that 65 tornadoes touched down, mostly in Illinois but also in Indiana and Kentucky. Munich Re says this was the largest tornado outbreak ever observed in the month of November and estimated that insured losses from this event were $900 million. For updated information see NOAA Watch.
PCS reported that in 2013 there were 29 catastrophes involving thunderstorms, which frequently include tornadoes. These catastrophes resulted from 24 thunderstorms and caused $12.87 billion in insured losses.
Munich Re includes tornadoes in the "Severe Thunderstorms" category shown below.
NATURAL DISASTER LOSSES IN THE UNITED STATES, 2013
NUMBER OF TORNADOES AND RELATED DEATHS PER MONTH, 2013 (1)
THE TEN MOST COSTLY U.S. CATASTROPHES INVOLVING TORNADOES (1)
TOP TEN STATES, BY NUMBER OF TORNADOES, 2013 (1)
TORNADOES AND RELATED DEATHS BY STATE, 2013 (1)
TORNADOES AND RELATED DEATHS IN THE UNITED STATES, 1994-2013 (1)
U.S. THUNDERSTORM EVENTS, 1993-2012 (1)
U.S. THUNDERSTORM LOSS TRENDS, 1980-2013