Climate change: Weathering the coming storms

A team of scientists has been studying the extreme weather in northern Argentina to see how it works — and what it can tell us about our future, writes Noah Gallagher Shannon

People talk as waves wash ashore and the outer bands of Hurricane Laura brought winds and rain in High Island, Texas. ( Jon Shapley/Houston Chronicle via AP)

When he thought back to the late-December morning when Berrotarán was entombed in hail, it was the memory of fog that brought Matias Lenardon the greatest dread. 

He remembered that it had drifted into the scattered farming settlement in north-central Argentina sometime after dawn. Soon it had grown thicker than almost any fog the young farmer had seen before. 

As forecaster, Lenardon’s chief concern was identifying weather patterns that might breed a thunderstorm, which on the pampas are notoriously swift and violent. 

This particular storm descended quickly. It engulfed the western side of Berrotarán, where winds began gusting at over 80 mph. Soon, hail poured down, caving in the roof of a machine shop and shattering windshields. 

In 20 minutes, so much ice had begun to accumulate that it stood in the street in mounds, like snowdrifts. As the hail and rain continued to intensify, they gradually mixed into a thick white slurry, encasing cars, icing over fields and freezing the town’s main canal. 

With the drainage ditches filled in and frozen, parts of the town flooded, transforming the dirt roads into surging muddy rivers. Residents watched as their homes filled with icy water.

Lenardon and I met in early December 2018, at the height of summer storm season, in the resort town of Villa Carlos Paz, about a two-hour drive north of Berrotarán. 

We were seated together in a hotel suite, where Lenardon was spending the day meeting with a group of government and university scientists who are funded by the National Science Foundation, Nasa and the Department of Energy. The group was in the midst of a two-month field campaign chasing the storms of the Sierras de Córdoba, and asked for Lenardon to join them.

The invitation had come specifically from the study’s leader, a 43-year-old severe-weather expert named Steve Nesbitt, who after learning of Lenardon’s story had driven several hours to meet him. 

A veteran of storm-chasing campaigns in Nepal, India and the Pacific, Nesbitt had developed a habit over the years of enlisting local sources. He found their stories often contained information that satellites missed or couldn’t perceive — how the contour of the land influenced clouds, how a storm might suddenly change directions in open country. 

In the case of the sierras, Nesbitt also knew that stories like Lenardon’s represented some of the only existing in-situ data on the storms. Few, if any, scientists had ever observed them up close.

Nesbitt, who is a professor at the University of Illinois at Urbana-Champaign, had dedicated much of the last 15 years to studying the freakish storms of this sleepy agricultural region. 

He first became fascinated by them in the early 2000s, when a Nasa satellite tentatively identified them as the largest and most violent on Earth. 

Nesbitt had travelled to Córdoba Province because he felt the weather patterns might offer clues into the enduring riddle of why certain storms grew unexpectedly into cataclysms. 

He believed that if he could chance a closer look inside one of the superstorms — mapping its internal wind structure and the conditions that gave it life — he might be able to produce a blueprint for predicting others like it, in Argentina and worldwide. 

“Climate-change models are predicting all this bad weather,” Nesbitt said. “But no one knows exactly what that weather will look like.” 

Every storm is composed of the same fundamental DNA — in this case, moisture, unstable air and something to ignite the two skyward, often heat. 

When the earth warms in the spring and summer months, hot wet air rushes upward in columns, where it collides with cool dry air, forming volatile cumulus clouds that can begin to swell against the top of the troposphere, at times carrying as much as a million tons of water. 

If one of these budding cells manages to punch through the tropopause, as the boundary between the troposphere and stratosphere is called, the storm mushrooms, feeding on the energy-rich air of the upper atmosphere. 

As it continues to grow, inhaling up more moisture and breathing it back down as rain and hail, this vast vertical lung can sprout into a self-sustaining system that takes on many different forms. Predicting exactly what form this DNA will arrange itself into, however, turns out to be a puzzle on par with biological diversity. 

Composed of millions of micro air currents, electrical pulses and unfathomably complex networks of ice crystals, every storm is a singular creature, growing and behaving differently based on its geography and climate.

With so many variables at play, it became apparent to modern meteorologists that predicting storms required sampling as many as possible. The perfect repository, as it turned out, existed in the Great Plains, where many of the world’s most dangerous storms are born. 

“In every storm there are fingerprints you can see of changing processes,”

Nesbitt said, and if he could find them, he could begin assessing how the storms are transforming in a warmer climate. 

Chasing Twisters

On the morning of December 12, the study forecasters reported that the two systems, along with another pocket of dry air moving north from Patagonia, seemed poised to converge over Córdoba sometime in the next few days.

By the evening, values of CAPE and humidity started to spike in ominous ways. With many of the scientists getting ready to head home, the coming storm would in all likelihood be the study’s last big chase. That evening, as many retired for the long day ahead, a few drank wine and watched “Twister.”

In the hours after the storm passed, Nesbitt, Wurman and the others tried to figure out what they had seen. By the time the last trucks pulled in, around 5:30am, the storm had raged unabated for more than six hours. At its peak, it stretched from the Andes to the Atlantic. 

Parts of it, now already drifting into Brazil, were so powerful they’d briefly become self-sustaining, the clouds feeding on their own heat and moisture — a destructive phenomenon meteorologists call “back-building.” 

In the hotel, the mood among the meteorologists, many of whom were in their 24th hour of monitoring, was delirious. Unable to return to their flooded rooms, a few retired to the hotel restaurant, where distant lightning fields stood visible out the windows.

One event in particular drew the meteorologists’ attention. For most of the evening, scans had shown a staggered line of storms marching steadily northward. Then, around 11:15 or so, something strange flashed on the satellite feed: a single, bulbous mass, which appeared suddenly, covering much of the image field. 

“This whole huge line just popped up,” said Kristen Rasmussen, one of the principal investigators of Relampago and an assistant professor at Colorado State University. “It could tell us a lot,” she said. “It was exactly what we were hoping for.” 

To elaborate, Nesbitt explained that as a storm travels along hot, saturated ground, its base tends to spread out and flatten, sucking up all available energy. The more it draws in, the faster and stronger the vacuum becomes, forming a narrow shaft of rushing air at the center of the storm, or updraft. 

An updraft, as Nesbitt went on, is essentially the storm’s piston, drawing heat and moisture in like gas into a crankshaft, before firing it upward, fueling the storm’s growth and movement. 

From what the team could gather, each of the storms had generated such large, powerful updrafts that they’d eventually merged together and begun to spawn other, smaller updrafts, creating what’s called a “mesoscale convective system” — in short, a giant, organized complex of perhaps 50 or more updrafts, which becomes self-sustaining as it germinates more and more offspring. 

When Nesbitt and the others began combing through the scans and data, they found that several of the other storms they’d observed in Argentina had formed similarly strong updrafts — many of them as much as 60% larger than those in North American storms. 

One had reached over 69,000 feet, among the tallest ever documented. Others covered more than 15 square miles — a massive plume of air surging upward at more than 150 mph. 

This finding seemed to suggest that something in the atmosphere was supercharging updrafts — wrenching heat and moisture off the ground so violently that it spun into unusually broad and towering pillars of air. 

To Nesbitt, the obvious culprit, at least in theory, was the heat and moisture itself — the storm’s fuel. As the atmosphere has continued to warm, lofting ever more moisture into the air, it has also begun to expand, increasing the air’s capacity to absorb ever greater volumes of moisture, not unlike a gas tank that grows in size as you pump more gas into it. 

And because water produces heat as it condenses at altitude, the added moisture accelerates the process further. Based on the study’s local weather stations — one of which was erected on the farmer Lenardon’s land — Nesbitt knew that the atmosphere in the province was already demonstrating signs of this cycle, including spikes in evaporative moisture. But as he pointed out, moisture and heat are merely values of potential energy. They tell us that the sky, like our drying forests, is rapidly becoming an ocean of fuel, but they don’t tell us where and when it might ignite — much less what, exactly, might spark it.

Finding answers to those questions, as Nesbitt saw it, required mapping updrafts in much more intricate detail. 

For years, the most prevalent models used to forecast global weather patterns, he explained, had relied on relatively simple mathematic calculations — or “parameterizations” — to predict where and when a storm might form. 

Programmed to predict some of the largest and most damaging effects of a storm, such as wind and rain, the parameters often failed to render the full complexity of a storm’s development, including the formation of its updraft, resulting in a loss of overall accuracy. 

“Now we’re having to go back,” said Nesbitt, “and try to add some additional realism to the calculations, so they can represent the full stages of a storm’s life cycle.” 

One day shortly before the end of the study, the meteorologists took me into the foothills of Villa Carlos Paz to visit a woman named Maria Natividad Garay, who had in her possession what may be one of the largest hailstones ever recovered. 

Her residence, which lay wedged between an apartment complex and repair shop, included a modest ranch home as well as several apartments and guesthouses, a few of which were rented to Argentine meteorologists affiliated with the study. When we arrived, Garay was sitting out back in a chair, her door left slightly ajar to the cooling breeze.

Garay is a carefully spoken woman in her mid-50s, with short brown hair and the mild, composed smile of someone long conversant with the punctuated boredom of life on the plains. Asked about the storm that produced the hail, she called up the precise date — February 8, 2018 — and told me that the storm had lasted exactly 15 minutes; it was etched in her mind. 

She had lived in the area for nearly 30 years now, she explained, and though the region was known for storms, that was merely a thing people knew. “You have to experience it firsthand,” she said.

She pointed out several long scars on the building next door, places where whole columns of bricks had been peeled away. 

“That was the first thing I saw,” she said; “hail was hitting the wall sideways.” 

The next instant, her skylights shattered, ice pouring into the house. The noise was incredible, she said, like a train coming through your yard — thin and distant at first, then roaring overtop of you. 

After the deluge stopped, she peered outside to find the yard blanketed in what looked like shards of milky glass. “It didn’t rain at all until the hail stopped,” she said, still surprised by the observation a year later. The meteorologists guessed this was why the stone had been so remarkably well preserved.

She held it before us. It was spherical and nearly the size of a grapefruit. She’d kept it wrapped in a Ziploc bag at the rear of her freezer. She couldn’t say why, exactly, only that it had struck her as an object worthy of preservation.

Its frightening size and appearance, buried there in her yard — it seemed of unearthly provenance. She leaned in and showed us the many thousands of crystals spidering through the stone, some of which were already beginning to fracture and melt in her hand.

But then again, she continued, it was just air and water. It was, in other words, composed of the same things we breathe.