The impact of climate change on tornadoes is still an active topic of study. Early research suggests that the warming earth will provide more energy to produce the storms that generate tornadoes, but less shear to give the necessary spin. Observations over the past few decades have yielded a couple of interesting trends. While there are now fewer dMore
When Rick Smith, a forecaster with the National Weather Service office in Norman, Okla., woke up on the morning of May 20, 2013, he knew it was going to be a bad day.
“It just had that feeling of doom,” he said.
It was the peak of tornado season and Norman, situated in the open, green flats of central Oklahoma, lies in the heart of tornado country. Smith knew that all the meteorological signs suggested that day was going to be the culmination of several days of unsettled weather in the area.
At the NWS office, Smith and his colleagues worked feverishly to make sure the local population was warned, taking to Twitter, working with local media, and briefing emergency managers around central Oklahoma, which looked to be the bull’s-eye.
Those managers, who knew Smith well from the close cooperation that comes from being in a tornado-prone place, would later tell him that they knew that day was going to be an especially tough one just from his tone.
“They could hear it in my voice,” he said.
In particular, forecasters were concerned because it looked like storms would develop earlier in the day than usual, meaning children would still be at school.
“As a forecaster you like to be right, but you don’t like to be right on those days,” Smith said.
On that day, the forecasts were right: A massive tornado that would reach EF-5 strength at its peak and stretched up to a mile wide tore across 17 miles of the intertwined areas of Norman, Oklahoma City and Moore. In just 35 minutes, it destroyed more than 1,000 homes and dozens of businesses, while damaging numerous others. It killed 24 people, including seven children at Plaza Towers Elementary, leveled by the ferocious winds.
Nearly three years after the tornado left a path of destruction that was visible by satellite, the community is still rebuilding and working to heal the hidden scars that can linger long after such natural disasters.
No Strangers to Tornadoes
Even for Tornado Alley, Moore has had a particularly notable history with tornadoes, with another major one roaring through in May 1999 and killing 43 people, and yet another in May 2003.
“We are not strangers to this happening,” Gayland Kitch, Moore’s emergency management director, said.
While forecasters were aware on May 20, 2013, that central Oklahoma was under the gun, “we had no idea it was going to be in Moore,” Smith told a group of reporters taking a tour of tornado-impacted sites last October. Where a tornado will hit isn’t clear until it forms.
It was around noon that the threat seemed to be honing in on the Oklahoma City metro area, including Moore to the south and the NWS office in Norman.
The tornado formed at 2:45 p.m. near Newcastle, to the southwest of Moore. Smith and the other NWS meteorologists, who have a bank of TVs in their office, saw it develop on the live feeds streaming from local news helicopters.
In less than four minutes, it was nearly a mile wide.
It soon became clear as the tornado moved closer to more populated areas that it posed a truly catastrophic threat. At 3:01 p.m., the NWS office did something it hadn’t since May 2003 and issued a tornado emergency notice. The term, invented on the fly by the same office during the monster 1999 tornado, is essentially a stronger version of a tornado warning, used when a major storm is poised to hit a heavily populated area.
Forecasters tweeted every few minutes as the tornado tore across landscape, noting as it passed major landmarks. Those efforts, along with the days of notice that severe weather was on the way, saved untold dozens who had enough warning to take shelter.
Thirty-five minutes after it formed, the tornado dissipated over Lake Stanley Draper, to Moore’s east. It left behind destruction that would eventually be tallied at $2 billion, with debris that filled 12,000 truckloads, Kitch said.
In one of starkest images of the tornado’s power, a Ford pickup was found twisted around a tree, it’s front wheels nearly touching the back ones. And “it flew about four or five houses before it found that tree,” Kitch said.
In an example of how fickle tornadoes can be in the damage they inflict, though, a flimsy-looking donut shop near the point where the tornado was at its fiercest survived virtually untouched, while across the way a 7-11 was completely destroyed.
Making of a Monster Tornado
Like all tornadoes, the deadly Moore twister was the product of just the right combination of ingredients, namely a warm, moist, unstable air mass that allows air at the surface to rapidly rise, and winds that change direction with height, needed to create rotation.
Instability of the atmosphere is expressed in a measure called CAPE, or convective available potential energy. Effectively, it is the energy available to fuel storms. A CAPE above 2500 is considered extremely unstable. The air mass over central Oklahoma on May 20 had a CAPE of 4000.
With the right trigger, storms can develop rapidly in such an environment and quickly turn severe. That trigger is often the collision between warm, moist air and colder, drier air, meeting at what is called the dry line, an area where the rotating supercell thunderstorms that give birth to the strongest tornadoes often form.
Just such collision happened on May 20, right in the area of central Oklahoma. Strong wind shear, or those changing winds, were also present on that day.
It was a supercell that formed to the west of Oklahoma City that spawned the deadly tornado that day. Not every supercell thunderstorm gives rise to a tornado, though, and figuring out why some do and some don’t is still an active area of research.
Another burgeoning area of study is how climate change might affect tornado activity.
Tornadoes are far too small and brief to be represented in climate models, but the conditions that produce them can be studied. Research so far suggest that because of a warming, moistening atmosphere, CAPE will like increase as temperatures continue to rise. But wind shear, needed to set off rotation, seems likely to decrease with warming, and it is unclear which of these trends might win out.
Changes in how tornado records have been kept over the years make it difficult to look for the kinds of long-term trends that are clear for events like heat waves. But some recent studies have found that over the past few decades, the number of days per year where tornadoes occur has declined. But at the same time, when there is an outbreak, the number of tornadoes per day has increased.
The variability in the number of tornadoes from year to year has also gone up. But pinning any of these trends to climate change is still a matter of research.
Nick Stemble, the ER manager for the Moore Medical Center, was aware of the potential for severe weather the day of the Moore tornado and had his staff on high alert.
When the tornado warning came, there were about 250 to 300 people in the medical center, and the staff began to move them to the center of the plus sign-shaped building, the designated shelter area, though it was not actually constructed to be a shelter.
One patient was in active labor, and because she had already received an epidural, could not walk down the stairs to the shelter area. Staff moved her to the safest place they could and piled pillows and blankets around her; three nurses stayed with her through the duration of the storm. (Her baby would be delivered safely later that day after she was transported by ambulance to another hospital after the storm passed.)
After leaving the room of the woman in labor, Stemble headed toward the shelter and could see the tornado coming through a bank of windows. He continued through the main lobby, stopping behind a fire door and peering through its small square window to the front of the building. He could see the storm’s winds beginning to push cars in the parking lot, eventually sending them crashing through the sliding glass doors of the entrance.
“And that’s when I decided I shouldn’t be looking out a window anymore,” Stemble said, standing in a set of trailers that are part of the hospital’s current, temporary setup while a new building — with a dedicated, reinforced shelter area — is under construction. On the wall behind him was a framed, and surprisingly intact, American flag that had been flying at the hospital and was found later, six blocks away.
While the hospital sustained major damage and ultimately had to be demolished, most of the damage was absorbed by the outside of the structure and everyone inside was relatively unscathed, Stemble said.
A short distance away, Plaza Towers Elementary had not fared so well, as the storm had ripped through before bearing down on the hospital.
Nikki McCurtain, a fourth-grade teacher then in her first year of teaching at Plaza Towers, was sheltered with her students in the bathroom. When the storm hit, “it happened real fast,” she said.
Sections of the roof were torn off and walls collapsed on top of students and teachers, pinning them under debris. Rescuers digging through the rubble would find the bodies of seven third-graders, killed by the wall that fell on top of them.
A Familiar Recovery
After the tornado dissipated, Moore began the familiar process of cleaning up and rebuilding.
“This storm, people didn’t even have to be told to push their debris to the curb. They already knew” from storms past, Kitch said.
In addition to the new Moore Medical Center — which will include a memorial of that day — a new 7-11 was being built in the spot where the old one was demolished. About three quarters of the houses destroyed by the storm have been rebuilt.
A low-slung brick building of new construction now houses Moore’s new emergency center. At its heart is a sleek, modern-looking room with flat screen TVs tuned to local news channels and weather radar lining the walls. The room also doubles as a tornado shelter, built to withstand 250 mph winds.
The addition of shelters is a theme in the town’s rebuilding. When the tornado roared through, people found the best shelter they could, as only about one third of homes there have shelters. In the local credit union, they sheltered in a vault, but still struggled to hold the door closed against the powerful winds. A family of five survived by sheltering in an old cast iron tub, the children wearing bike helmets, a mattress thrown on top of them.
Of the people who died, “most of them were sheltering, and most of their shelters were quite adequate,” Kitch said. But the sheer intensity of the storm and the chance path it took was what made it so deadly.
The Plaza Towers students who perished, sheltered in one of the best spots they could have been in, Kitch said, were among those victims of chance.
The school has since been rebuilt, a gleaming, inviting space that includes a purpose-built shelter. It comprises four classrooms and the hallway between them — they look no different than the other classrooms in the school, but are built of single-pour concrete.
“I wouldn’t work at a school that didn’t have a shelter,” McCurtain said.
Etched in stone panels embedded in the brick walls of the school’s entrance are the outlines of children — this one in pigtails, that one playing with a football, another carrying a backpack bearing a favorite car. There are seven of them, each one a memorial to one of the students who died that day.
Stone benches bearing each child’s name and the things they loved, such as unicorns or monster trucks, curve along the front of the school.
Just inside the entrance is the remnant of a wall painted with a growling panther, small dings to the paint scattered here and there. It was part of the original school’s entrance, left remarkably intact by the storm and salvaged and restored by maintenance crews.
It now stands as a symbol of what once stood there and the resilience of a community too often subjected to the most destructive forces of Mother Nature.