Huge rise in dangerous fire-generated thunderstorms: report

A dangerous and freakish type of weather event increased substantially in the past bushfire season alone, a new report reveals.

A report into the devastating Black Summer bushfires has detailed a stunning rise in the number of dangerous fire-generated thunderstorms.

The storms are freak weather events that produce extreme winds, lightning, tornadoes and black hail and can rapidly change the expected spread and behaviour of a fire.

Between the early 1980s and the 2018-19 season, there were 60 recorded fire-generated thunderstorms in southeastern Australia.

Now the tally sits at almost 90 – close to a 50 per cent rise in one season alone.

Fire-generated thunderstorms increased by 50 per cent in the past bushfire season. Picture: AAP Image/Dean Lewins

The shocking figure was contained in a report compiled by former chief scientist Mary O‘Kane and former deputy police commissioner Dave Owens released on Tuesday by the NSW Government.

It follows an inquiry into the bushfire season in NSW that burned 5.5 million hectares, destroyed 2476 homes and killed 26 people across the state.

The unusual fire-generated thunderstorms, also known as pyrocumulonimbus, could escalate the spread of a fire and produce hazardous conditions for firefighters, the report said.

They form when plumes of hot air reach high into the sky and interact with the atmosphere, forming a cloud that hangs over the fire — and can sometimes transform into the dangerous thunderstorm.

The freakish weather events create extremely dangerous conditions for firefighters. Picture: BOM

The thunderstorms were one of many contributing factors in an “extreme and extremely unusual” bushfire season that took even experienced firefighters by surprise.

This or a similar atmospheric weather event is thought to have contributed to the death of firefighter Samuel McPaul, who was 28 and “doing everything right” according to the RFS when he died at Jingellic in December after his truck flipped in extraordinary weather conditions.

Lots of bushfire activity from the season challenged traditional assumptions about how fires behave and spread, the report said, as it called for more investment into fire science research.

Expert evidence considered by the inquiry suggests the effects of climate change could increase the number of fire-generated thunderstorms in future.

One recommendation calls for hazard reduction burning to be prioritised in areas where blazes are likely to escalate into the dangerous storms.

The NSW Government has vowed to implement all 76 recommendations contained in the report.

Others include trialling the early dispatch of water bombers to bushfires and aerial firefighting at night.

It also calls for increased hazard reduction burning in general while acknowledging the fuel loads in the 2019-20 season were, on average, on par with that of the last three decades.