December 2019, ScientificAmerican.com 63inside the fire tornado may have reached almost 2,700
degrees Fahrenheit. The object was more than 1,000
feet wide at its base and, according to radar imagery,
three miles high. It lasted for at least 40 minutes, dur-
ing which time it moved slowly across the ground, leav-
ing a path of destruction nearly a mile long.
Our team interviewed witnesses and collected video
evidence in the hope of learning from the event. The fire
tornado occurred on the evening of July 26, 2018, in the
course of a forest fire covering thousands of acres north-
west of Redding. So extensive and intense was the fire
that it generated pyroCb clouds at altitudes higher than
three miles. Suddenly, at around 5:30 p.M., the flames
raced eastward, killing firefighting bulldozer operator
Don Smith, as well as a civilian in his home. As the wild-
fire neared the outskirts of Redding, it spawned a num-
ber of fire whirls and threw embers more than a mile
ahead of the fire and across the Sacramento River.
These started several “spot,” or small, isolated fires near
two subdivisions at the end of a dead-end road. An ex-
tremely chaotic scene unfolded as firefighters tried to
evacuate homeowners and save houses even as their es-
cape route was being cut off. People were literally run-
ning for their lives.
Redding firefighter Jeremy Stoke headed to the
scene to help. Just as he was arriving, at about 7:30 p.M.,
the fire tornado formed over the road, trapping resi-
dents and firefighters at the subdivisions. It apparent-ly caught Stoke on the road. He transmitted a mayday
call on his radio before powerful winds rolled his truck
multiple times; it eventually came to rest against a tree
hundreds of feet away. Stoke was found hours later,
dead from traumatic injuries.
Two Cal Fire vehicles being driven down the road
had most of their windows blown out and were bat-
tered by flying debris. Strangely, one of the trucks was
damaged mostly on the driver’s side and the other on
the passenger side—even though they were only 150
feet apart and facing the same direction—indicating
the rotating motion of the air. The occupants huddled
on the floorboards to save themselves from projectiles.
Three nearby bulldozers also had their windows blown
out, with one operator getting glass in his eye and an-
other receiving serious burns to his hands. A retired
police officer who was driving out realized his truck
bed was on fire and pulled over; he survived but sus-
tained burns to his airways. Most tragically, on the out-
er edge of the revolving inferno two children and their
great-grandmother perished inside their burned home.IN THE LABORATORY
What can we learn from an event like this? Can we pre-
dict when and where a fire tornado will occur so that
we can evacuate residents and firefighters? What
causes fire tornadoes? A first step toward an swering
these questions is to look back in history. In 1871 aBURNING
BOARDS
arranged in a
rough triangle
allow air to swirl
into the central
area, where an
other fire gath
ers the rotation
into a vortex.
Forest or urban
fires of certain
shapes can simi
larly gen erate
fire tornadoes.© 2019 Scientific American © 2019 Scientific American