The severe forest fires that engulfed parts of western Canada this week were so intense that they generated huge “clouds of fire” that created their own thunderstorms.
In what some experts have said is one of the most extreme events they have ever witnessed, over 700,000 intra-cloud and cloud-to-ground lightning – from both fire clouds and thunderstorms regular – were recorded on Wednesday over a period of 15 hours.
“That’s 5% of lightning strikes in Canada in just 15 hours,” said Chris Vagasky, a Colorado-based meteorologist at Vaisala, a Finnish company specializing in meteorological and other environmental measurements.
Forest fires so extreme that they create their own climate are not common, but with climate change making fires both more frequent and more intense, scientists say the chances of such events triggering out of control fires will increase. probably in the future.
A fire cloud, known as a pyrocumulonimbus cloud or pyroCb, typically forms when a fire rages with sufficient intensity to create updrafts of smoke, water vapor and ash that rise high in the air. atmosphere. These columns of air cool and condense, forming clouds that can generate thunder, lightning, and tornado-force winds.
Pyrocumulonimbus clouds are worrisome because they can cause wildfire behavior to be erratic, making it difficult for firefighters to control fires or predict their course. Clouds of fire can also help forest fires spread by lifting hot embers that land downwind or producing lightning that ignites new areas.
It is not clear why some large fires create pyrocumulonimbus clouds and others do not, and this remains an active area of research. Scientists also hope to better understand the effect of climate change on the emergence of fiery clouds.
In general, however, scientists have observed an increase in the frequency and intensity of forest fires due to global warming.
“As the Earth continues to heat up, you tend to have drier periods which create more favorable conditions for forest fires,” said Dakota Smith, a Colorado-based meteorologist. “If you increase the frequency of forest fires, you also increase the risk of extreme forest fire behavior.”
The wildfires raging in British Columbia and Alberta developed following a historic heat wave that brought record temperatures across the Pacific Northwest. It was this sweltering heat that helped create the ideal conditions for large fires to break out, said Mike Flannigan, director of the Canadian Partnership for Forest Fire Science at the University of Alberta.
“It was a powder keg just waiting for a spark,” he said.
Forest fires, wherever they occur, need three basic ingredients to thrive: vegetation, such as leaves, twigs, cones, and dead trees, for fuel; favorable conditions such as hot, dry and windy weather; and finally, some type of ignition such as lightning or a man-made event.
The recent heat wave, which produced temperatures well above 100 degrees Fahrenheit for several days in parts of British Columbia, has helped dry up the land and create a perfect storm of wildfire ingredients.
“The drier it is, the easier it is for a fire to start and spread,” said Flannigan. “It also means there is more fuel available to burn and more energy released, so you have a higher intensity fire.”
So when an ignition event occurs, the consequences can be devastating.
Nowhere was this more evident than in the village of Lytton, B.C., which set new national temperature records three days in a row, peaking at 121 degrees on Tuesday. A day later, a rapid forest fire ravaged the area, forcing a mandatory evacuation order shortly before the entire town was consumed by the flames.
Flannigan said it was unusual to see such severe wildfires in British Columbia so early in the summer. If conditions remain hot and dry, the area could experience a grueling fire season.
“The risk is high and the potential for an extremely active season is there,” he said. “In part, this is already happening now.”