A rash of tornadoes devastating multiple states is targeting the South, an area traditionally outside of ‘Tornado Alley,” with a particular vengeance.
Catastrophic weekend tornadoes and storms that started Friday killed 28 people in Kentucky, Missouri and Virginia, with the majority of deaths, 19, occurring in the Blue Grass state where 42 twisters have been reported this year.
Tornadoes continued to cut a path across the South, as Weather Channel videos of violent rotating columns of air tossing trees in the air near Athens, Alabama, May 20 and shredding a roof in Tennessee demonstrate.
Northeastern Global News spoke to Northeastern climatologist Chengfei He about why tornadoes are increasingly occurring in Southern states outside the traditional bounds of the area known as “Tornado Alley,” which roughly includes parts or all of Texas, Oklahoma, Kansas, Missouri, Iowa and Nebraska.
He also explains why tornadoes typically move in a counterclockwise direction and why spring is a peak time for twisters to form.
Are tornadoes becoming more frequent in the U.S.?
When looking at the total number of tornadoes across the entire country, the annual frequency of U.S. tornadoes has remained relatively constant, but the location of where tornadoes are occurring is shifting.
Observation shows that tornado activity appears to be decreasing in the traditional “Tornado Alley” of the Great Plains, while increasing in the Southeast’s “Dixie Alley.”
What accounts for the southern shift?
Tornado-favorable weather conditions are moving toward Dixie Alley. This type of weather is marked by unstable air, with warm and moist air close to the ground and dry, cool air at altitudes between 10,000 and 30,000 feet above the ground.
Why is spring a peak time for tornadoes?
Spring has tornado-favorable weather conditions.
During spring, warm, humid air from the Gulf of Mexico begins pushing northward as the sun warms the continent. Meanwhile, cold air masses from Canada are still strong. When these dramatically different air masses meet along weather fronts, they create instability in the atmosphere.
Think of it like opening a window in a hot room on a cold day –– that dramatic temperature difference creates powerful air movement.
Why do most tornadoes run counterclockwise?
The counterclockwise rotation happens because of something called the Coriolis effect. This effect is caused by Earth’s rotation and influences how air masses move across our planet.
Imagine you’re playing catch with a friend on a merry-go-round. When the merry-go-round isn’t moving, throwing the ball straight to your friend is easy.
But once the merry-go-round starts spinning, something interesting happens –– even when you throw the ball in a straight line, it appears to curve away from your friend! This is due to Coriolis force.
What makes tornadoes so dangerous?
Tornado winds can exceed 200 mph in the strongest storms. They form quickly and that gives people only minutes to take shelter.
Is windy, stormy weather in general increasing?
The short answer is yes, but it’s complicated.
Different types of storms are being affected differently by climate change, and the evidence is stronger for some types than others.
Robust data shows extreme precipitation events have been increasing since the 1950s, largely due to human-caused climate change.
But the link between climate change and tornadoes is less clear