With summer well on its way in Australia, the memories of the bushfire disasters in Summer 2019/2020 are creeping back into the minds of locals. Bushfires devastate thousands of square kilometres, burning up flora and displacing millions of animals country wide.
The recent bushfire disasters have many people wondering, “Can bushfires create their own weather?” And, if so, what can Australians expect this summer?
La Niña in Australia will bring increased rainfall during summer. Though this helps offset the effects of drought in the short term, the boom in vegetation growth will quickly dry out under the baking sun. As temperatures continue to rise, there will be tons of fire fuel across the country.
How Do Bushfires Create Their Own Weather?
Bushfires in Australia can cause their own weather under “extreme weather conditions”. Dry air and hot weather near ground level are the main culprits. This is because the hot weather dries out the vegetation and makes it more likely to catch fire.
Combine this with the hot air at ground level —which causes atmospheric instability— and you have the prime conditions for horrible thunderstorms.
There are two types of clouds formed under these conditions according to AccuWeather, and these are Pyrocumulus and Pyrocumulonimbus.
Let’s look into how thunderstorm clouds like these accelerate bushfires in Australia.
The Dangers of Pyrocumulus and Pyrocumulonimbus Clouds
An active bushfire generates extremely hot air that rushes upwards at great speed. As the air rises, it cools and condenses into water droplets on the ash from the bushfire, and a cloud is formed.
A Pyrocumulus cloud is a “fire cloud” that forms in this way. It forms in the plume of the bushfire and consists of water droplets and ash.
A Pyrocumulonimbus cloud, on the other hand, is a “fire storm cloud”, which sounds a lot more terrifying.
The Bureau of Meteorology says that Pyrocumulonimbus clouds are thunderstorms that form in the plume of smoke from an active bushfire. As the hot air from the bushfire rises, it expands and cools, condensing even further and creating a thunderstorm in the plume of the bushfire.
Whilst these storms can help put out the bushfire itself, they’re more likely to spark new bushfires by means of dry lightning.
Bushfires Can Create Their Own Wind Patterns, Too
As if the above is not bad enough, bushfires create their own wind patterns under the right (or wrong) conditions. Air that is warmer than its surroundings, such as the air coming off the top of a bushfire, rises quickly because it is less dense. The rush of air creates a vacuum at ground level, pulling even more hot air from around the fire into the plume. This is how bushfires create their own wind patterns.
Moreover, sometimes the upward rush of hot air creates a “fire tornado”, drawing up embers and ash into the wind. These conditions are incredibly dangerous for firefighters, and lend themselves to starting more bushfires in the surrounding area.
Diagram of How Bushfires Create Their Own Weather
The diagram below is courtesy of the Bureau of Meteorology. It demonstrates how bushfires in Australia create their own weather, including Pyrocumulus and Pyrocumulonimbus clouds.
- Hot air and smoke rises from the fire.
- Hot air mixes with cool air in the plume, causing it to expand and cool.
- When the air in the plume has risen high enough, the low atmospheric pressure causes its air to cool (cloud forms).
- In an unstable atmosphere a thunderstorm can develop: pyrocumulonimbus cloud
- Contact with dry air further away from the fire causes the cloud to evaporate and cool, resulting in crashing rain.
- Lightning can be produced and ignite new bushfires.
Do you have your disaster plan in place to deal with possible bushfires in Summer 2020/2021? Disaster Recovery specialise in fire cleaning and restoration, so in the event of a bushfire disaster in your area, contact us to support your recovery process. Our blog page features helpful articles, too, to support you in the coming months.