Story at a glance:
- Tornadoes are occurring more often across parts of Tornado Alley and the South than previously recorded.
- EF1 storms are considered moderate at wind speeds between 86 and 110 mph, and they are becoming more common in the South.
- Most tornadoes occur from March through June, but there are significant events outside that time.
Tornadoes are occurring more often across parts of Tornado Alley and the South than previously recorded.
Tornadoes are famous for forming in a band that stretches from Texas to South Dakota, referred to as Tornado Alley. But a new report from USA Today shows that 20 states saw an increase in tornado activity when comparing annual data from 1980 to 1999 with 2000 to 2019. This includes a number of states in the South outside of the traditional Tornado Alley, including Kentucky, Alabama and Mississippi, among others.
Tornadoes are measured on the Enhanced Fujita (EF) scale, which categorizes tornado damage from 1 to 6. And they are getting deadlier.
There have been more than 60,000 tornadoes reported in the past 70 years or so, 1950 to 2019, with more than half of the tornadoes being EF1 or more severe.
From EF0, the weakest tornadoes that have wind speeds between 65 and 85 mph, and EF5 the strongest tornadoes clocking at wind speeds 200 or greater, an EF1 is considered moderate at wind speeds between 86 and 110.
Scientists aren’t sure how much the increase in reported tornadoes might be attributed to better tracking technology. They’re also not sure why tornadoes appear to be increasing in frequency. But they suspect it may have something to do with heating in the Gulf of Mexico. Tornadoes often form in storms where warm moist air from the Gulf meets a change in the temperature.
The hot Gulf winds meet cooler winds in the western direction, which causes instability and the wind begins to shear, leading to tornado formation, according to Shawn Milrad, associate professor of meteorology at Embry-Riddle Aeronautical University.
When comparing 2000-2019 with the previous two decades, the scientists saw an increase in days with tornado outbreaks, or swarms — events where 10 or more tornadoes are spawned by the same weather system within a couple days.
Most tornadoes occur from March through June, but there are significant events that have been occurring outside the historical season.
When looking at deaths caused by tornadoes, several states saw increases in the study period, notably Missouri, Kentucky, Tennessee and Alabama. USA Today noted that many of the deaths are occurring in the South, which is more densely populated than Tornado Alley and where more people live in mobile homes, which tend to fare worse in the storms.
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