Extract from ABC News
It is only September and already Australia's fire danger dial has been swung to red on several occasions.
After warnings of catastrophic fire danger on the New South Wales South Coast this week, Queensland's Channel Country is facing extreme fire danger on Thursday, as is the Northern Territory's north Barkly region on Friday.
With projections for a hot and dry end to 2023 under the El Niño climate pattern, and increased fuel loads across some parts of the country, it is unlikely to be the last warning like it.
So when you see a rating of extreme and catastrophic fire danger, what is it actually telling you? And what should you be doing?
The likely outcome
In its simplest form, each category describes how dangerous a bushfire might be if it were to start that day.
It does not signal the likelihood of a bushfire occurring, nor does it mean one is already underway.
Australasian Fire Authorities Council (AFAC) chief executive Rob Webb said the system was designed to be an early warning for the community about what they needed to think about.
"It's just saying, 'Look, if you see smoke on a day like today, these are the kinds of things you should be doing'," he said.
"And it's not something that we can just rest on and hope we learn these things. It's a really important message."
There are four ratings, and their recommendations are:
Moderate: Plan and prepare. You should stay up to date and be ready to act if there is a fire.
High: Prepare to act. There is a heightened risk of fires in your area. Decide what you will do if one starts.
Extreme: Take action now to protect your life and property. Fires will spread quickly and be extremely dangerous. Check your bushfire plan and make sure you and your property are ready. Reconsider travel through bushfire risk areas.
Catastrophic: For your survival, leave bushfire risk areas. If a fire starts and takes hold, lives are likely to be lost. Stay safe by going to a safer place early in the morning, or the night before.
What increases the risk?
One of the main factors behind a high or low-risk fire day is weather, with a hot, dry and windy day the standard recipe for bad bushfires.
But the weather is not the only factor, which is why you may see an extreme fire danger rating on a day where the weather forecast does not appear particularly dangerous.
For decades, air temperature, humidity and wind speed, as well as preceding drought conditions, were the primary factors in the calculation of the fire danger rating.
This formula was known as the McArthur Fire Danger Index.
But in 2022 a new model for calculating risk was introduced, known as the Fire Behaviour Index.
The new model also takes into account a more in-depth look at a district's vegetation, including the different trees and plant species, and information about how much there is and how dry it is.
Each of these variables are crunched by models at the Bureau of Meteorology, spitting out a number from zero to 100+.
The higher the number, the higher the fire danger in that area.
Mr Webb said the model was able to be updated as scientific understanding of fires progressed.
"It's trying to not only paint a better picture of what the fuels are doing, but it's trying to build a system that is able to move with the science," he said.
"And as the climate might change, and we start to see things and fuel types that we may not have seen before, we can adapt the fire system to meet those needs and will continue to improve it."
Ratings not the full story
Mr Webb said while the fire danger rating provided a good summary of potential risk, it did not paint the full picture.
He said factors like lightning, which made ignition more likely, and how many different regions had a heightened risk of fire, could also influence the outcome of a fire and put a strain on resources.
Mr Webb said these were considered in the fire danger rating for the day, but were communicated in other ways too.
For example, fire agencies may put total fire bans in place to reduce the risk.
"When you hear statewide total fire bans being put in place it doesn't mean it's catastrophic or extreme fire danger across the whole state," Mr Webb said.
"It just means there are parts of the state where it's going to be busy and [emergency services] can't afford any more fires to start because there aren't enough resources."
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