Editor’s Note (March 27, 2023): A deadly tornado hit Mississippi last Friday evening. In this December 2021 article, he explores why tornadoes that occur at night and in the Southeast are often deadly causes.
It was around 9:30 pm on December 10th when a severe tornado hit the town of Mayfield, Kentucky. The exceptionally long-lasting twister was part of his December rare outbreak that hit several states in the Midwest and South. That night. The storm was well predicted and given relatively early warning, but at least 89 people have been confirmed dead and some are still missing.
Tornadoes at night can be particularly deadly. This is not just because more people are more likely to be asleep. To analyze the reasons and explain why the Southeast is particularly prone to nighttime storms,Scientific American spoke with Stephen Strader, an atmospheric scientist and disaster geographer at Villanova University who studies how tornado and other severe weather risks overlap with social vulnerability.
[An edited transcript of the interview follows.]
Is there a meteorological difference between tornadoes during the day and tornadoes at night?
Daytime storms that produce tornadoes tend to be more volatile. But at night, the boundary layer ( [portion] troposphere) begin to separate from the rest of the atmosphere. This powerful, often south-facing, low-altitude jet carries moisture from the Gulf of Mexico, and when daytime instability abates, it is shrouded in darkness and causes thunderstorms.in the case of [last] Friday’s event saw very strong low-level jets and significant low-level wind shear [in which winds blow in different directions at different levels of the atmosphere] in the environment. These two factors are very common after sunset in the Southeast.
What makes the Southeast particularly prone to tornadoes at night?
First of all, tornadoes are not uncommon in the Southeast.we like to think about that classic wizard of oz A scene in which a sepia-toned tornado dances in the landscape of Kanas. The reality is the Southeast. It can be traced back to April 27, 2011. [the deadliest day of an event in which 360 tornadoes formed across the region and 320 people were killed], or the 1974 Super Outbreak. This is because by the time large synoptic systems move across the country and evolve over time, they typically reach the southeast during the evening hours. Storm speeds up. A tornado would travel at 60 miles per hour over plains instead of 5 miles per hour. It also makes for a wet storm because there is a lot of moisture to work with. Many ingredients play a role. But the important thing I always tell people is, if I had to ask where tornadoes are most common, I’d say Kansas or Oklahoma, and maybe Texas. Alabama, Mississippi, is where the most is. There is a mismatch, and that mismatch is not meteorological. It’s actually a social problem. And it has to do with vulnerability and exposure.
What factors make this a social problem?
Population density is everything: there are more people in the Southeastern United States. [tornado] what happened there. Poverty is bigger. And the big problem in the Southeast is that the density of mobile manufactured housing is much higher than in any other country in the world. [other parts of] United States The national average percentage of homes that are mobile homes is about 6%, but states like Alabama are above 13-14%. Land use and zoning also play an important role. Outside the United States, most manufactured homes are located in mobile home parks designated for that purpose. In the Southeast, there are 80% of manufactured homes that are not in Mobile Home Park. They are found on isolated land in rural areas. This creates more targets for these tornadoes to hit. This means that instead of passing through fields of corn or wheat, a long-range tornado will pass through the heart of a small city or rural area, which is slightly more populated than other places.
You’re updating a study done in 2008 that looked at the difference between daytime and nighttime tornado mortality. That study found that the mortality rate for the latter did not decline as fast as the overall tornado mortality rate. Does that still apply?
me and walker ashley [of Northern Illinois University] We’ve revisited this and added the next 15 years of data to this and actually take a slightly different perspective. The scariest thing I’ve seen is that the mortality rate between daytime tornadoes and nighttime tornadoes is on the rise. As such, the proportion of people dying from these nocturnal events is increasing. If you look at all tornado events occurring during the day, it’s decreasing. What we’re seeing is that this difference between day and night actually affects the likelihood of being killed.
Another scary thing is [in the 2008 paper] Ashley found that tornadoes that occur at night are 2.5 times more likely to die. I thought maybe it got better. And what we found is that it’s not. It’s probably a little worse.
Most of us go to work during the day as well. So the exposed side of things also changes for him throughout the day. What we usually see is a more dispersed population at night. It’s a little scary, but if anything, the problem is getting worse.
