(CN) — It looks unreal, a Texas take on “The Wizard of Oz.” Instead of Dorothy spinning in her tornado-launched home, a twister topples Riley Leon’s 2.5-ton pickup, spins it in a circle, then blows it upright. Leon speeds away, out of the frame of a storm chaser’s camera phone.
Leon, 16, suffered a lower back fracture but thanks to his seatbelt he survived the cyclone’s 130 mph winds, which knocked his Chevy truck over on a rural highway near Austin in March.
Scientists have documented an increase over the last 20 years of the frequency of tornadoes in the Southern states of Mississippi, Alabama, Arkansas, Tennessee, Kentucky, Virginia, Georgia and South Carolina.
And that’s troubling given the large number of manufactured homes in the region, lax codes that do not require them to be securely anchored to the ground, and the tendency of tornadoes to form at night when people are sleeping – fueled by warm, moist air from the Gulf of Mexico – rather than in the late afternoon or early evening, as they typically do in the Great Plains.
Against this backdrop, Leon’s experience is a lesson: driving through a tornado, bad idea; hunkering down in a manufactured home, even worse.
“A car is a little bit safer than a manufactured home, believe it or not. … You are strapped in. You have a seat belt, and you have safety precautions. You have airbags,” said Stephen Strader, a Villanova University professor focused on reducing risk from hazardous weather.
“When you don’t have a properly anchored manufactured home, the tornado comes along, picks up the entire structure and tosses it like a kite into the woods 100 yards away and you’re inside it,” he cautioned.
In the most harrowing experience of her life, Jennifer Henson-Collins turned to her faith.
Sheltering with her children in a hallway of her manufactured home in Cookeville, Tennessee, as an EF4 tornado spun into her backyard, she hollered prayers to God.
“The tornado picked us up with the hardwood floor and landed us 250 feet across the street! We lost everything! I could feel my guardian angel right behind us hovering over us to protect us. … We had minimum injuries. The scariest night of my life,” she wrote, in a “Tornado Survivor Stories” account she gave to the National Weather Service.
That twister was among an outbreak of more than a dozen nocturnal tornadoes that ravaged west and middle Tennessee on March 2 and 3, 2020, killing 25 people, injuring another 309 and causing $1.6 billion in property damage.
For scientists struggling to link changes in U.S. tornado patterns to climate change, such outbreaks underscore the difficulty of understanding this most enigmatic of weather events.
Even America’s most learned researchers at the National Oceanic and Atmospheric Administration admit their ignorance.
“How do tornadoes form? The truth is that we don’t fully understand,” the agency states in a “Severe Weather 101” primer on its website.
And while tornado clusters, when six or more form within hours of each other, are becoming more common, there are now fewer days on average throughout a year with tornadoes, about 100, than the 1970s, when there were about 150, despite better tools for detecting relatively weak tornadoes.
“The why is one of the great unknowns that I wish I knew the answer to,” said Harold Brooks, a senior research scientist at NOAA’s National Severe Storms Laboratory in Norman, Oklahoma, who has been studying tornadoes since 1985.
Brooks described tornado formation as a balancing of ingredients. They are rotating thunderstorms. Thunderstorms develop when warm, moist air rises into cold, dry air, he explained.
“Now what makes that storm severe and likely to produce a tornado, it needs to form where the wind in the environment, the horizontal wind, increases with height over the lowest several miles,” Brooks continued.
Wind gets the storm rotating.
“To get rotations down to the ground, what happens is that when the storm rains that cools the air as the rain falls and evaporates. And if the air is a little bit cool but not too cold we can get rotation down near the ground. If the air is too cold … it will essentially kill the storm because that kills the warm, moist air at low levels. So there’s real balancing act that goes in,” Brooks said.
The small-scale details make it hard to tell what’s going on in the storm, Brooks noted.
Another factor: Tornadoes are more likely if the storms that form are relatively isolated, Brooks advised, so there aren’t other storms around them to mess up the air flow.
He believes the changing patterns of U.S. tornadoes—more days with clusters of them but less days when any form—implies the structure of the jet stream has changed in ways that affect their development. But pinpointing how changes in air currents impact weather phenomenon that are very small in comparison has proven difficult, Brooks concedes.
“What we know about the structure of the jet stream is on spatial scales of a few thousand kilometers and time scales of a day or two. And when we’re trying to go from that down to something that’s a kilometer and minutes, there’s a huge mismatch in the scale,” he said.
As for climate change, experts say it is causing offsetting precursors. While it is increasing the prevalence of balmy, moist air from the Gulf of Mexico that seeds thunderstorms, it is decreasing the wind shear that spins them.
Vast differences in the temperature of air blowing down from the North Pole and up from the equator create winds that increase with height. But as climate change causes the poles to warm more than the equator, those winds diminish, which is less favorable for tornadoes.
Given all the variables and unknowns with tornadoes, Strader, the Villanova professor, concentrates on raising awareness about how building codes should be changed in the South to reduce injuries and deaths.
Of the 117 U.S. tornado deaths in 2019 and 2020, 113 were in Southern states and 60% occurred in manufactured homes, according to USA today.
Due to lax zoning rules in the Southeast, Strader said, manufactured homes – also informally called mobile homes – are often not located in mobile home parks.
“For instance, over 80% of mobile homes in Alabama are not located in mobile home parks. They are out on rural plots of land where there might be one or two homes and they’re family members. We call those family pods,” he said.
With residents so spread out in rural areas, emergency managers and county officials are faced with a dilemma: Where to put community shelters given many people will not have time to reach them? The average warning time for tornadoes is about 13 to 14 minutes, according to Strader.
One solution, he says, is more strict standards for anchoring manufactured homes.
In response to Hurricane Andrew, a Category 5 hurricane that battered Florida with 165 mph winds in August 1992 and destroyed 63,500 homes, the Federal Emergency Management Agency established wind zones that dictate how much anchoring is required for houses.
“So if you live in Miami-Dade County, you have the highest requirements of any manufactured home in the United States in terms of the anchoring standard. … But once you get about 100 miles away from the coast, it goes away,” Strader said.
In some areas of the South, anchoring is not even required for manufactured homes if they weigh enough to meet the minimum in local building codes.
Due to these shortfalls, Strader advises people in Southern states to see themselves in Miami. But not flying in like Dorothy did to Oz in a tornado-blown home.
“If someone comes up to me from Alabama and says, ‘I’m going to buy a manufactured home. What can I do to make myself safer?’ I tell them to pretend their mobile home is going to be in Miami-Dade County. And strap it down as if you lived on the coast,” he said.
from Courthouse News
