Australia is not at the end of its pain with the fires which ravage the south-east of the country. Forest fires are so intense - their smoke has been spotted in Chile, 12,000 km away - that they generate their own meteorological phenomena, “fire storms”, with devastating lightning.
These thunderstorms, almost without rain, are difficult to predict: scientists are still trying to understand their origin. These “fire storms” are formed as follows: large fires cause extreme heat and a large plume of smoke which, rising in the sky, interacts with the humidity of the air to form a cloud. “The shocks of the ice particles located in the very cold upper parts of these clouds cause an accumulation of electric charge, which is released by giant lightnings. After producing a fire storm, this cloud is called pyrocumulonimbus ”.
Dangerous and unpredictable thunderstorms
These thunderstorms tend to be accompanied by very little rain so when lightning strikes the ground, very dry, this generates new fires in the surroundings. On "Black Saturday" in Victoria in 2009, the lightnings caused new fires up to 100 kilometers away from the original fire.
But the danger does not stop there. Fires can also throw embers up to 30 kilometers beyond where the thunderstorm occurred. And clouds can also produce strong updrafts and "downdrafts" generating extremely strong winds that can fan the existing flames. They can even create fire tornadoes.
"Fire storms are the most dangerous and unpredictable manifestation of a forest fire, and it is impossible to stop or control it," said Rachel Badlan, researcher at the University of New Wales. South. Experts say these phenomena are incredibly difficult to predict because the fires themselves are difficult to predict.
"Forecasting the weather component may be possible days in advance, but forecasting favorable fire conditions will remain a significant challenge for some time," said the Australian Meteorological Office.
Canberra-based researchers believe that the so-called "deep inflamed" part - the depth of active fire - is essential to understanding when fire storms occur, and therefore are studying the factors influencing this depth.
More frequent phenomena?
Between 2001 and 2016, 56 such thunderstorms were recorded in Australia. This phenomenon has also been observed in the United States, Canada, Russia and Mongolia - mainly in forest areas.
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But there are signs that they are becoming more common. During a six-week period in 2019, at least 18 pyrocumulonimbus formed in Victoria alone, in southeast Australia.
Experts also believe that climate change is amplifying the conditions necessary for the formation of these fire storms. Researchers predict that by 2060, there could be a sharp increase in conditions that could generate this type of thunderstorm, and that it could start to occur in the spring as well as in the summer.