Tornadoes

Tornadoes are created inside supercell thunderstorms, defined by a rotating updraft initiated by wind shear. This rotation pulls in warmer air, causing its rotation speed to increase. When the rotation meets cooler air, its energy increases. 

The Fujita Scale measures the intensity of a tornado based on the damage it leaves behind. An EF-0 tornado produces winds of 65-85 miles per hour, whereas an EF-5 produces winds of more than 200 miles per hour. 

The regions of the United States where tornadoes occur more frequently are shifting east. A 2021 study of the change in the number of days favorable to tornado formation found that areas around the Mississippi River and east of the Appalachian Mountains saw the most significant increases. At the same time, tornado activity in places like Oklahoma and Kansas decreased to some of the lowest numbers ever seen.  

These shifts are changing the dangers associated with tornadoes and how people understand their tornado-related risk.  

A 2020 study about tornado warnings among people with blindness or low vision found that most of those interviewed preferred television, phone alerts and radio for receiving weather warnings. Participants also identified the need for information to be hyper-local, including the use of street names and other identifying landmarks to help distinguish where the areas of concern are.  

The authors found that areas struck by tornadoes were more likely to have a higher percentage of Black residents, a lower percentage of people with a bachelor’s degree, and a lower median income.  

People living in poverty and Black people are less likely to be homeowners and must rely on the decisions of rental building owners to determine whether their home will be rebuilt. Insured homeowners are also more likely to be able to afford to rent the decreased amount of rental housing available, even as rental prices increase. This leads to a higher level of displacement and fewer affordable housing options available after a tornado, often changing the makeup and nature of the community simultaneously.   

Tornadoes form within powerful thunderstorms, particularly supercells, when rising warm, humid air interacts with cooler air aloft, creating instability and strong updrafts. Wind shear—changes in wind speed and direction at different altitudes—causes the rising air to begin spinning horizontally, and as the updraft intensifies, this horizontal rotation is tilted vertically.  

For a tornado to develop, spinning air must also occur near the ground, often as downdrafts of cooler air descend and spread out, interacting with rising warm gusts to generate rotation at the surface. This spinning air accelerates as it is drawn inward, like a figure skater pulling in their arms, due to the conservation of angular momentum. A tornado forms when this concentrated, rotating column of air extends from the thunderstorm cloud base to the ground.  

Improved weather tracking and emergency alerting systems are needed to give people enough information and time to seek shelter. Additionally, emergency alerts often cover multiple counties and dozens of communities – largely because the meteorologists issuing them from the NWS are not at the storm’s epicenter. Supporting local media organizations can help communities receive more localized information about where a tornado is, which will help people make better decisions about their safety. 

Most weather apps that provide radar images and online streaming of emergency radio communication are not fully accessible to people with disabilities and functional needs. Increasing accessibility to this technology will help people with disabilities and functional needs keep themselves safe during tornadoes.  

Lastly, in areas that are historically most vulnerable to tornadoes, there are no laws requiring structures like apartment buildings or manufactured homes to be built to withstand high winds, like there are in hurricane-prone areas.  

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