Pyrocumulonimbus clouds, more popularly known as fire-generated thunderstorms, add a sinister mode of risk throughout extreme bushfire situations. These weather phenomena can make a critical situation even more dangerous by adding to chaotic fire dynamics that hamper firefighting efforts. Under the guidance of professor McRae, the pyroCB register — a single-purpose website for tracking occurrences of these clouds — was born. He underscores the increasing occurrence of pyrocumulonimbus activity in Australia, especially over the last 20 years.
Similarly, Australia has experienced many episodes of these extreme fire behaviors since the notorious Ash Wednesday fire in 1983. As per the pyroCB register, there have been more than 100 fire thunderstorms recorded since the year 2000. Just seven such incidents were documented in the 35 years before that. This trend is a stark indicator of changing fire behavior, especially during extreme fire seasons like the Black Summer.
The Nature of Pyrocumulonimbus Clouds
Fires generate massive, hot updrafts due to the immense heat released. This thunderstorm-like updraft transports abundant moisture and particles into the upper atmosphere, allowing pyrocumulonimbus clouds to form. This process is responsible for the creation of lightning, thunder and, in some cases, tornadoes given the right conditions. In extremely rare instances, these clouds themselves can produce black hail, underlining their capriciousness and danger.
Recent near real-time radar imagery from north-east Victoria, near Walwa, showing the dramatic pyrocumulonimbus formation. This jaw-dropping cloud phenomenon even generated record lightning strikes within the conflagration. Normally when this appears you have a major large fire that is producing its own weather system. This makes it more difficult to implement effective firefighting strategies and increases dangers to surrounding communities.
Professor McRae notes that “by the time the plume has risen and cooled (enough to cause lightning), it could be 40, 50, 100 kilometres downwind.” This unpredictability makes firefighting much more difficult. It creates dangerous situations for local residents who don’t expect danger up ahead.
Historical Context and Recent Trends
Pyrocumulonimbus clouds have long been unique climatic anomalies rarely seen throughout Australian history. Their occurrence has increased dramatically since the turn of the century. Even compared to previous fires of this era, the Black Summer fires of 2019-2020 were unique in their severity. In only one season, the number of pyrocumulonimbus events doubled. This alarming trend signals an urgent need for enhanced understanding and management strategies to mitigate risks associated with these clouds.
Yet the 2003 Canberra bushfires should be a cautionary tale. They illustrate the profound impacts that can take place when pyrocumulonimbus clouds develop during exceptional fire episodes. The fires caused four deaths and the loss of almost 500 homes. Climate change is accelerating the frequency and intensity of bushfires. Experts such as Professor McRae are highlighting the importance of making fire management strategies dynamic so that they can address these new challenges head on.
The Role of Fire Services and Public Awareness
“Climate change has definitely played a role in the increase of these clouds,” says Professor McRae. He underscores the Fire Services’ critical function in keeping our communities safe and secure. “The most important message is do what the fire service says you should do,” he advises. This guidance is critical, particularly as circumstances are increasingly complicated by unpredictable winds and shifting weather patterns.
Residents are reminded to stay alert and follow evacuation orders from fire officials. “If the fire service says go, you pay attention to that message,” Professor McRae adds, emphasizing that timely action can save lives during critical moments.
The interaction of climate change with fire behavior is another rising worry. As Professor McRae observes, “We’re evolving, but it’s rapid adaptation because climate change keeps accelerating the evolution of the problem.” Between persistently low river flows and a hotter, drier land under climate change, conditions are set up for fires to grow very quickly.
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