Asheville and surrounding towns in western North Carolina had just been drenched by a heavy rainstorm when the remnants of Hurricane Helene slammed into the Blue Ridge Mountains.
What unfolded starting Wednesday evening and lasting throughout the weekend is a well-studied atmospheric phenomenon.
“As the weather moves toward the mountains, the clouds have to rise up and over the mountains, and that’s the buoyancy effect,” said Doug Outlaw, a National Weather Service meteorologist in the agency’s Greenville-Spartanburg office. South Carolina. “It tends to push out more rainfall, and unfortunately it caused extreme flash flooding, which devastated communities. It was an enormous amount of water that was channeled and funneled through the valleys at once.”
The devastation in North Carolina’s inland mountain towns—thousands of feet high and hundreds of miles from any coastline—may seem unexpected for an area once seen as a safe haven from the effects of climate change, but it’s the kind of far-reaching impact which will become increasingly likely, experts say.
Helene flooded parts of southern Appalachia with more than two feet of rain. Floods washed away entire homes and washed out highways, cutting off access to cities.
“That’s about half a year’s worth of rain in four days,” Outlaw said. “It is one of the worst weather events to hit this area in history.”
At least 20 locations in western North Carolina, including Asheville, experienced flooding expected only once in a thousand years.
Climate change strengthens storms because higher ocean temperatures act as fuel and a warmer atmosphere allows heavier rain over land. For every 1 degree Fahrenheit of warming, the atmosphere can hold about 4% more moisture, says Shel Winkley, a meteorologist at the nonprofit research group Climate Central.
This significantly increases the risk of catastrophic flooding.
A May report from Climate Central detailed the increasing risk of inland flooding due to global warming. The places where Helene’s remains caused the most damage were among those most at risk, according to the report.
“Appalachia was listed as one of the areas that had an outsized burden for future flooding,” Winkley said. “This is an area that is known to have the potential for more flooding and also more expensive flooding. Unfortunately, we saw that last weekend.”
Of the more than 120 deaths recorded so far from storms in six states, at least 44 occurred in North Carolina.
Part of the problem is the region’s mountainous terrain. But in this case, the area suffered a double whammy: Heavy rain fell just days before Hurricane Helene made landfall in Florida, after which the remnants of the storm brought even more rain and wind to southern Appalachia.
“It was two compound events that collided,” Winkley said.
Forecasters saw it coming with a high degree of accuracy.
“*URGENT NOTICE* This will be one of the most significant weather events to occur across the western portions of the area in modern times,” officials with the National Weather Service’s Greenville-Spartanburg office wrote in an update on X on Thursday. “Record flooding is forecast and has been compared to the 1916 floods in the Asheville area.”
According to the Asheville Museum of History, 25 people died in 1916 when floods swept away buildings, destroyed the local power plant, destroyed the railroad and cut off Asheville from the rest of the country.
The similarities are striking.
“The forecast was really good,” said Christopher Godfrey, chairman of the department of atmospheric sciences at the University of North Carolina Asheville. “The National Weather Service has done a fantastic job. They were quite firm in their choice of words.”
Given these warnings and his own expertise, he said, the gruesome outcome came as no surprise to him.
‘It’s about the topography here. There is really steep terrain. Houses are built on steep terrain. Roads go up steeply,” Godfrey said. “This is such a catastrophic flood with all the rain we got. Even well-built bridges will be gone.”
Scientists are investigating what role climate change played in Hurricane Helene and have shared some initial results. One group found that Helene was up to 20% wetter in parts of the Southeast due to global warming. Another estimated that climate change caused some parts of Georgia and the Carolinas to receive 50% more rainfall and that precipitation totals were up to 20 times more likely to occur due to climate change. The estimates are preliminary, but both are based on respected scientists using previously peer-reviewed methods.
Godfrey recorded 12 inches of rain over three days at his home in Arden, North Carolina. More than 24 inches fell in nearby Hendersonville during the same period, according to the National Weather Service. That is simply too much for the mountainous landscape; the flood damage in the Godfrey area is roughly equivalent to what Federal Emergency Management Agency maps show would happen in a flood expected once every 500 years.
The severity caught one of his neighbors off guard, Godfrey said.
“The neighbor across the street said, ‘I heard that, but I didn’t do anything. I didn’t think it would be that bad. ”
Godfrey said some of the storm’s impacts have been surprising, including the extent of tree damage, which has closed roads and made the work of first responders even more challenging.
“I don’t think anyone expected the magnitude of the tree fall,” said Godfrey, who researches wind storms and tree falls.
He thinks most of the trees fell because the ground was so saturated. During the height of the storm, Godfrey said, he heard a pattern ringing throughout the neighborhood as one tree after another fell.
“You could hear click, click, click, click and then hear the crash when it landed,” Godfrey said. “What we heard was the breaking of the roots.”
Two walnut trees, taller than 100 feet, fell several dozen feet from Godfrey’s home. Another tree crunched a neighbor’s car.
Communications systems have also fared worse than Godfrey expected.
“We have no idea what’s going on there,” Godfrey said in a telephone interview during a visit to a weather station he manages at UNC Asheville. “The only reason you got me is because I’m currently standing on the top of a hill overlooking Asheville. Down in the valley there is no internet, no Wi-Fi, no mobile network and not even text messages.”
Asheville has been called a climate paradise in some reporting because it is removed from coastal threats such as sea level rise and its relatively high elevation keeps temperatures low.
But almost nowhere on Earth is isolated from natural hazards, and few places have taken steps to adequately prepare for extreme weather that is becoming increasingly common. Seattle was once seen as a potential climate paradise, until a 2021 heat wave sent temperatures to 108 degrees Fahrenheit in a place where most people lacked air conditioning. And parts of the Midwest that were considered climate havens have also seen extreme rain.
“Climate change affects different communities in different ways, and so while mountainous areas may have been a refuge from extreme temperatures, they are, as we discovered, not necessarily a refuge from the potential for devastating flooding,” Winkley said.
It’s a reminder, he said, of the far-reaching consequences of a warming world.
“Normally a hurricane is thought of as a coastal problem, but now we’re finding that these events – these large-scale, climate-driven events – can make the weather more intense further away from the typical impact sites that you would think,” he said.
This article was originally published on NBCNews.com