Terrifying science behind whirling ‘fire vortex’ in Shasta’s Carr fire inferno
Triple-digit temperatures and super-concentrated heat — not heavy winds — are spinning funnels of fire that have twice erupted in the dangerous Carr fire, tormenting the city of Redding in Northern California as firefighters contend with a rare meteorological foe.
Witnesses likened one Thursday night to a tornado. Another ominous fire cloud Friday reached nearly 5 miles high, so tall it cast a shadow and caused wind gusts of 50 mph.
This unusual weather phenomenon, called a “fire vortex,” is creating dangerously erratic conditions, complicating efforts to contain the steadily growing Carr fire in Shasta County, said Daniel Swain, a climate scientist at UCLA.
“This giant rotating cylinder on top of the fire, composed of smoke, pulls burning embers and smoldering debris thousands of feet into the atmosphere,” he said.
It allows fire to jump over barriers, such as roads, rivers and bulldozed firebreaks, Swain said. “It causes it to do crazy, very unpredictable things.”
What’s behind the phenomenon?
The Redding fire is not driven by stiff winds, as witnessed in Santa Rosa, the Oakland hills and other fatal California wildfires, Swain said. Instead, the fire created its own heat source, aided by an afternoon sun that baked the ground with air temperatures to 113 degrees.
“It rises, stretches and spins, like a ballerina.”
— Daniel Swain, climate scientist
As super-hot smoke ascends, it creates a wicked updraft — so strong it begins to rotate.
“It rises, stretches and spins, like a ballerina,” Swain said.
Incredible video captured by bystanders show an enormous tendril-like plume whirling near Redding, spewing smoke and poisonous carbon monoxide gas into the air.
Most “fire whirls” are small and brief spin-ups that occur almost continuously on the margins of major fires.
But the Carr fire’s fire-induced vortex was unusually deep and tall, according to scientists.
“Full-on rotating convective column. Scary as hell,” tweeted Neil Lareau, assistant professor of atmospheric science at the University of Nevada, Reno.
It was so powerful that three high-voltage transmission towers were melted and blown over, according to journalist Damon Arthur of the Redding-based Record Searchlight newspaper. He witnessed mature trees that escaped the flames but were uprooted and stripped of all leaves.
“The Carr fire is unprecedented in that strong winds were not driving the fire, but rather the plume rotated and intensified, creating its own weather.
“The Carr fire is unprecedented in that strong winds were not driving the fire, but rather the plume rotated and intensified, creating its own weather. For a fire to burn into Redding like that is very unique.” — Craig Clements, director of the Fire Weather Research Lab at San Jose State University
For a fire to burn into Redding like that is very unique,” said professor Craig Clements, director of the Fire Weather Research Lab at San Jose State University. “Hot temperatures, dry air and critical fuel conditions. The fire danger today is extreme for Northern California.”
Last October’s catastrophic fire in Santa Rosa was ignited
from ridge to ridge.
In Redding, the winds were essentially dead calm, Swain said. But temperatures reached the triple digits, peaking at 113.
“It really did create its own weather system over the city of Redding,” he said.
Similar columns of fast, rising hot air are often seen over the Sierra in the summer, resulting in bubbly cumulus clouds. That’s because those mountain peaks act as a heat source, warming the local atmosphere. The heat causes little pieces of the atmosphere to rise, condensing and forming clouds — even triggering thunderstorms.
While rare, it is not unknown to firefighters. One of California’s
most famed “fire tornadoes” occurred in 1926, when lightning struck large oil tanks near San Luis Obispo. Thousands of whirls were formed, lofting one house into the air for 150 feet, killing two occupants.
But they are difficult to predict, Swain said.
“California’s firefighting agencies are second to none,” with strong connections to the meterologic community, he said. “They were well aware of the potential for this to happen.”
“In this instance, it all came together,” he said, “at the worst time and worst possible place.”