Tornadoes are columns of rotating air that extend from the base of a storm cloud to the ground. Also known as twisters, this type of extreme weather can cause devastating structural damage by producing strong winds, sometimes in excess of 500 kilometers (311 miles) per hour. In 2024, they were responsible for approximately $1.7B in damage and 54 deaths in the US, which experiences the most tornadoes of any nation.
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Supercell tornadoes involve rising warm air—updrafts—from the strongest type of thunderstorm—supercells—to help turn horizontally rotating tunnels of air into vertical columns. In non-supercell tornadoes, which are generally weaker as a result of forming within less energetic systems, vertical rotation is present from the start near ground level.
Waterspouts form over water as long, thin columns of mist and air, while elephant trunks are tornadoes that elongate vertically as they become tilted during their formation, resembling the mammal's appendage. Wedge tornadoes are among the most powerful, often spanning a mile or more in width.
The region experiences atmospheric instability and extensive wind shear due to the convergence of warm, moist air from the Gulf with cooler, drier air from the Rockies. However, some recent data suggests tornadoes are more frequent and more powerful in the Dixie Valley, which includes much of the lower Mississippi Valley.
Technological limitations prevent direct measurements of wind speeds where tornadoes make contact with the ground. Instead, the Enhanced Fujita scale assigns a rating with a range of speeds based on how much damage a tornado caused to various types of structures. These types are more extensive than the original Fujita scale.
If you live in a region prone to tornadoes, have a plan to retreat to a safe room built to withstand strong winds, such as an underground shelter or a windowless room at the lowest level of a study building, in case of a tornado warning. Having a stay-at-home kit with non-perishable food and water, medications, batteries and chargers, and a battery-powered radio is also essential.
Winds can accelerate due to a tunneling effect as they pass under a structure, making seeking shelter from a tornado in a mobile home or recreational vehicle highly discouraged. Significant tornado damage results from debris being picked up and hurled by strong winds, making it unsafe to be near windows that may shatter.
The final steps of tornadogenesis—the process of forming a tornado—depend on near-surface details, such as local geography, which are difficult for radar to observe and affect how funnel clouds make contact with the ground. Inconsistencies in storm behavior have limited the amount of advance warning people receive before tornadoes touch down.
Research teams use drones, mobile weather stations, and radar systems to capture real-time meteorological data, better understand conditions that favor tornado formation, and improve forecasting models. As of 2022, model limitations result in roughly 70% of tornado warnings being false alarms.
The Tri-State Tornado touched down in Shannon County, Missouri, on March 18, 1925, and killed 695 people as it traveled through Illinois and Indiana, making it the deadliest tornado in US history. The deadliest 21st-century tornado was in Joplin, Missouri, on May 22, 2011, killing 158 people and injuring over 1,000.
While there is no official national tornado season as with Atlantic hurricanes, many tornadoes form in the presence of thunderstorms, which are fueled by solar heating and the energy released by the condensation of water vapor. The airflow instabilities created from this energy build throughout the day until the sun sets.
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