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A rising cloud of hot air, smoke, and moisture, reaching the height of the plane and flashing lightning. Dominating the landscape are wind-driven flame fronts, often bouncing off fire escapes. Maybe even a rare fire hose.

Runaway Fire in Southern Oregon, months of drought and last month’s surging heat wave, Biggest wildfire ever in the United States this yearhaving already burned more than 340,000 acres or 530 square miles of forest and grassland.

And at a time when climate change is causing wildfires to get bigger and more intense, it’s also one of the most extreme, so big and hot that it’s affecting the winds and disrupting the atmosphere.

“The fire is so big and produces so much energy and excess heat that it changes the air,” said Marcus Kauffman, spokesman for the state forestry department. “Normally the weather predicts what the fire will do. In this case, the fire predicts what the weather will do.”

The Runaway Fire has been burning for two weeks, and for most of that time, one or more extreme fire behaviors have lit up the entire fire, causing rapid changes in winds and other conditions, causing the flames to spread rapidly through the forest canopy. trees and embers blown over long distances at the same time quickly ignite point fires elsewhere.

“This is an extreme, dangerous situation,” said Chuck Redman, a forecaster with the National Weather Service who is at fire headquarters and provides forecasts.

The fires are so severe that they confuse firefighting efforts from their own weather conditions. Density and extreme heat can force the wind to circulate around them, forming clouds and even creating eddies of heat, smoke and gusts of wind, sometimes called fire hoses.

The disastrous Carr Fire, near Redding, California, in July 2018 was one of those fires, some attributed to the fire hurricane, that burned 130,000 acres, destroyed more than 1,600 structures and killed at least eight people. winds as high as 140 miles per hour this was filmed on video.

Many wildfires grow quickly, and Bootleg Fire is no exception. It grew a few square miles or less in the first few days, but in more recent days it has grown to 80 square miles or more. And almost daily, erratic conditions forced some of the nearly 2,200 firefighters to retreat to safer locations, further hampering containment efforts. More than 75 houses and other structures burned.

Along the northern edge on Thursday night, fire jumped over a chemical-retardant-treated line, forcing firefighters to retreat. This was the latest example of a fire outstripping a fire.

“This fire is a real challenge, and we’re looking at a constant battle for the foreseeable future,” said forest department incident commander Joe Hessel.

And it is likely to continue to be unpredictable.

“Fire behavior is a function of fuels, topography, and weather,” said Craig B. Clements, director of the San Jose State University Wildfire Interdisciplinary Research Center. “It usually changes from day to day. Sometimes by the minute.”

Mr Redman said the fire created high air currents of high air currents, some of which reached 30,000 feet, almost daily, of hot air, smoke and humidity. He said that one day they saw one of these clouds collapse; this can happen in the early evening when the updraft stops.

It can spread a fire by creating strong, gusty winds from all directions, forcing the surface air outward. “This is not a good thing.”

But last Wednesday, conditions led to the formation of a larger, taller cloud called a thundercloud-like pyrocumulonimbus. Neil Lareau, who studies wildfire behavior at the University of Nevada, Reno, likely reached altitudes of about 45,000 feet.

Like a thunderclap, the massive cloud caused lightning strikes, alarming firefighters because of their potential to start new fires. It might have rained, too.

“Some of these events are raining on their own,” said John Bailey, a forestry professor at Oregon State University.

Rain can be a good thing by dampening some fuels and helping to slow the fire. However, Dr. Rain can also create dangerous downdrafts by cooling the air closer to the surface, Lareau said.

There are also reports of fire hoses, small swirling air vortices, and flames common to many wildfires, often incorrectly identified as fire hoses. The whirlpools of fire are small, perhaps the largest several dozen feet in diameter and lasting from a few seconds to a few minutes.

However, Dr. Lareau said there are some indications that the Fugitive Fire may have created a veritable fire whirlwind, which could be several thousand feet in diameter, with wind speeds in excess of 65 miles per hour, spread thousands of feet into the air and was the last. Taller. “It seems to produce a pretty significant rotation,” he said.

Fire tornadoes occur as a plume of hot air rising inside a fire, which pulls more air from outside to replace it. Local topography and differences in wind direction often caused by fire can give this inflowing air a spin, and stretching the air column can cause it to spin faster, just as a figure skater pulls her arms in to increase her strength. translate

Mr Redman said incident command had not received any fire hose reports. “But it’s entirely possible for someone to break out in a fire this big and intense,” he said. “When we get these extreme events, things happen that we need to watch.”

Other types of extreme fire behavior are more common. But the duration of the extreme behavior in Runaway Fire stunned some who fought it.

“This extreme behavior and explosive growth is happening every day,” said Mr. Kauffman. “And you can’t really fight fire under these conditions. It’s too dangerous.”

The root cause of most extreme behavior is the large amount of heat the fire pumps out.

The amount of heat is related to the dryness of the fuel of trees and other vegetation, both dead and alive. Fuels in Southern Oregon and much of the West are extremely dry as a result of the severe drought affecting much of the region.

Dr. Clements likened it to a campfire. “You want the driest wood and logs to light the fire,” he said. “It’s the same with a forest fire. That’s why we’re watching the drought.”

If the plant is moist, some of the combustion energy is used to evaporate its moisture. The fire burns hotter if there is no moisture to evaporate. “More heat is released,” he said. “The flames are bigger.”

Oregon was also hit by an extreme heatwave in late June, when record temperatures were broken by as much as 9 degrees Fahrenheit in some places. This further dried out the vegetation. In southern Oregon, fuels were as dry as late summer in a more normal year.

Dr. “We had a lot of fuel ready to burn,” Bailey said.

What will help end the excessive behavior and ultimately the fire itself is a good and widespread rain. But that’s not on the horizon.

“We don’t see any significant relief for at least next week,” said Mr Redman. “But I don’t think we can get any worse.”