“This is historic in the U.S.,” Craig Clements, director of San Jose State University’s Fire Weather Research Laboratory, told BuzzFeed News. “This might be the strongest fire-induced tornado-like circulation ever recorded.”
How it formed
The tornado formed as the blaze, which has already charred an area three times as large as the District of Columbia, erupted and began to rotate like a supercell thunderstorm. Initially the smoke plume reached about 20,000 feet. That’s not overly impressive for a thunderstorm, but it couldn’t rise any higher: It was trapped beneath an inversion.
That “cap” in the atmosphere caused the smoke to spread out. But around 7:15 p.m. Pacific time, two plumes suddenly managed to break the cap. They rose into an unstable environment and exploded upward, towering to nearly 40,000 feet within 30 minutes. That extreme, rapid vertical growth of the fire fueled an updraft that eventually would spawn the tornado.
Looking at a profile of the atmosphere from a nearby National Weather Service office on the day of the fire, changing winds with altitude were apparent. That means any cloud that spans multiple layers in the atmosphere is going to experience this shearing force resulting from being pushed in multiple directions. This caused the entire smoke cloud to rotate, just like any tornado-producing thunderstorm.
Eventually a pair of quickly-rotating updrafts became established between 7:30 and 8 p.m. — rivaling the intensity of the turbulent behemoth storms that sweep across the Plains each spring. The southern updraft went on to produce a legitimate tornado.
The key was how quickly the updraft rose. After all, the smoke cloud top doubled in height, surging upward nearly four miles in 40 minutes. Just like a skater pulling in her arms, when a vortex near the ground is stretched, it intensifies — likely the main ingredient in tornado formation.
While the National Weather Service forecast office in Sacramento described the vortex as a fire whirl, our analysis suggests this was an actual tornado. Fire whirls are much more common. They are the equivalent of dust devils and shed off by large wildfires by the hundreds.
But this vortex’s rapidly-rotating updraft that was embedded in cloud-based rotation bore the hallmarks of a textbook tornado.
“I’m relatively comfortable calling this a tornado; I’m sure some people will take issue with it,” Neil Lareau, a physics professor at the University of Nevada at Reno, told Axios. Lareau specializes in fire weather phenomena.
The funnel produced tornado-like damage, too. It tore trees from the ground, destroyed additional structures and even collapsed/twisted large high-tension electrical towers!
The NWS & @CAL_FIRE Serious Accident Review Team (SART) are conducting a storm damage survey regarding the large fire whirl that occurred Thursday evening in Redding. Preliminary indicators placed max wind speeds achieved by the fire whirl in excess of 143 mph. #cawx #CarrFire pic.twitter.com/3iRX90lhLJ— NWS Sacramento (@NWSSacramento) August 2, 2018
An even more intense firenado Down Under?
While this may be the most intense fire tornado observed in the United States, an even more vigorous fire tornado has been documented in Australia.
On Jan. 18, 2003, a lightning-sparked wildfire near Canberra produced a pyrocumulonimbus smoke cloud that grew into a supercell thunderstorm. It produced 80 mph winds, fueling the blaze and exacerbating fire suppression efforts. Similar atmospheric conditions were in place, and the storm produced a tornado that traveled roughly 15 miles over the course of an hour, touching down four times and carving out a path about a quarter-mile wide.
Investigators in the wake of the Canberra Fire Tornado found a path of clockwise-laid trees, suggesting convergent rotating winds at the surface.
That particular tornado skirted most towns, but did level a neighborhood in the Australian community of Lincoln Close, Chapman. The storm did damage consistent with 160 mph winds — even tossing the eight-ton roof of a water tower more than a half mile near Mount Arawang.
Record heat stoking California blazes
Fire season is in full swing across the Golden State, and this year has seen a string of exceptionally destructive blazes. The Carr Fire has been blamed for at least six deaths and claimed nearly 1,600 structures.
July ranked as the hottest month in the past three decades in Redding. And there’s no end in sight to the hot conditions as climate change continues to take a toll on the beleaguered region.
Redding’s top-five hottest years have all occurred in the past five. In addition, the moisture-starved region is seeing a drying trend during the summer months. Thanks to this combination, increased fire activity is likely in the years ahead — and the uptick we’re seeing now is partially because of climate change.
As the planet continues to warm, devastating fire seasons like this in the West will become the near normal.
Capital Weather Gang’s Jason Samenow contributed to the reporting in this story.