BOM severe weather outlook for 2021-22 suggests floods, cyclones on the cards
The severe weather season is here, and floods and cyclones are on the forecast.
The Bureau of Meteorology has just released its outlook for the severe weather season, and senior climatologist Greg Browning says, like every year, we need to be prepared.
According to the BOM, there is an average to slightly above average risk of tropical cyclones this season.
The long-term average is for 11 cyclones to form in Australian waters and for four to cross the coast.
But that value has been slipping over recent decades. Since 2000, the average has fallen to nine cyclones per season, according to Mr Browning.
Last year was also expected to be slightly above average and we ended up seeing eight.
"It's sort of with a grain of salt in some ways that we still use that long-term number because it just seems like the days when we had 15 plus are just behind us at the moment," Mr Browning said.
But don't let those declining numbers lull you into a false sense of security.
"While we don't get heaps in an absolute numerical sense, it just takes one in your neck of the woods to cause a whole lot of trouble."
And it doesn't need to be a full-blown cyclone to do damage, tropical lows are also more likely to form under these climatic conditions.
Flooding rains expected
"The whole general climate driver setup is basically favourable for above-average rainfall, particularly over the eastern two-thirds of the country," Mr Browning said.
In the west, a negative Indian Ocean Dipole is starting to break up; to the north there are warm waters, and to the east, a La Niña is threatening to form.
"So, all of those factors basically make us feel pretty confident that we're likely to see average to above-average rainfall, particularly over northern and eastern parts of the country during spring and into summer."
That is coming on top of some already wet catchments, particularly in the east.
"There are parts of the country that the landscape is quite wet, the soil moisture is pretty high, and so it won't take too much rain to see flooding," according to Mr Browning.
"Certainly, increased riverine flooding is a risk during this severe weather period."
It's definitely storm season
Storm season started off with a bang this year, and it is very far from over.
According to Mr Browning, the research is pretty hit and miss as far as the relationship between severe thunderstorm activity and climate drivers.
So, it is difficult to say if there is a higher chance of severe storms than normal this year.
But this is definitely the time of year when we normally see severe storms.
"Especially, eastern New South Wales south-eastern Queensland. It's really coming into the heart of this severe thunderstorm period," he said.
"Right through to probably late spring, we'll see various episodes of severe thunderstorms."
Not off the hook for fires
Mr Browning was emphatic about bushfires.
"Australia always gets fires every summer."
But overall, the rain over the last few seasons and the forecast of more has lowered the risk of big campaign bushfires this year.
"We certainly aren't looking at a season like 2019–20 where we had droughts and really dry conditions leading into the summer and everything was ready to burn.
"We're a long way from that," he said.
But grass fires are still a risk.
The rain is fuelling grass growth, and it doesn't take many days of hot, dry weather for vegetation to dry out.
After good winter rains, an above-average risk of grass fires is also an issue in parts of the south-west, according to Mr Browning.
South-west Western Australia doesn't usually get a lot of summer rain and with no climate drivers pushing wetter than average conditions in the west, this year is likely to be no exception.
"They haven't had some of the soaking rains like we've had over in the east.
"So as summer goes by and they don't have follow-up rainfall, areas will dry out, and they will have fires."
So even though it is not expected to be hotter or drier than usual this year, Mr Browning said fires in the south-west were still likely.
Heatwaves still likely
With wet conditions expected, the chance of the most extreme heat days is currently less than some of our past baking years.
"But as we go into summer, particularly if La Niña doesn't do much or falls in a heap, then we could see an increased number."
"Again, we're not primed to have a really hot extreme year, but obviously, with the background of global warming, we're likely to see some extreme heat days."
La Niña, or La Niña like conditions, can also up the humidity and lead to longer heatwaves.
"Even if they aren't at the highest intensity level, with the extra humidity, that is a major health risk in itself," according to Mr Browning.
These conditions can also lead to stiflingly hot nights, particularly in the tropics.
It's time to prepare
No matter the year, Australia is a pretty extreme place.
According to Richard Thornton, the chief executive of Natural Hazards Research Australia, one of the best things you can do to prepare your family for the types of disasters you may face is to make a plan and get the kids involved.
"There's lots of jobs your kids can do, from helping to tidy the garden to getting their favourite possessions ready in a go bag and organising pets, to making sure the laptops, tablets and phones are easy accessible, fully charged and with a charger, to backing up important documents on hard drives."
Queensland Fire and Emergency Services (QFES) Assistant Commissioner Andrew Short said people should do everything they could to prepare themselves.
"We do know that communities and individuals or families do better when they're prepared," he said.
"It's very important for people to understand their risk; understand by the nature of where they're living what that means for them."
Emergency services around the country provide information on the risks and best ways to prepare, so be sure to make that plan and keep up to date with warnings this severe weather season.