15 October 20
Latest on La Niña from the Bureau of Meteorology: There is an increased risk of flooding this summer in the east and north of Australia as the La Niña makes its presence felt.
In the fortnight since La Niña was announced, there has been widespread rain and it looks like flooding is something we are going to have to get used to, according to the BOM's October to April outlook.
BOM senior climatologist Greg Browning said it would be a big change from last year.
"Certainly the concern for this season is for rainfall leading to potentially widespread and prolonged flooding."
The risk of flooding was particularly for the eastern two-thirds of the country, he added.
With the La Niña comes an added risk of tropical cyclones.
The outlook suggests a 66 per cent chance of more cyclones than average for the Australian region this season — and they are expected to form earlier than normal.
In a normal year there are between nine and 11 cyclones, with four crossing the coast. At least one cyclone has crossed the coast every year on record.
This year's above-average forecast bucks the trend of recent decades which saw an overall reduction in the number of cyclones in the region.
Only three years since 2000 had seen more than 11 cyclones and none since 2005, Mr Browning said.
"Certainly it looks like it's going to be more active than we've seen in recent years."
Cyclone season traditionally runs from November to the end of April, with the first landfall in early January — in La Niña years, however, the first cyclone typically crosses the coast in mid December.
With low overall numbers, predicting how many cyclones there will be in each region each year is difficult.
Mr Browning said the accuracy of cyclone outlooks varied, especially when you started looking at the sub-regions.
"We're talking about numbers of cyclones between two and five or seven a year, so quite a small number, that really decreases the accuracy."
He said sub-region accuracy ranged from very low to moderate, but this improved when all sub-regions were combined.
"But as far as the overall number for the Australian region, we can say with some confidence that our outlooks have accuracy."
At least it is looking better than last year, with a normal fire risk in most states and territories.
But it is still a bit of a mixed bag according to Mr Browning.
Parts of Victoria and New South Wales have seen good rain in recent months, but other places like Queensland and south-west Western Australia have seen pretty dry conditions over that time.
"So while the rainfall outlook suggests that they will see a lot of rain over the next few months, until the rain starts to come in and wets the environment and increases the soil moisture, they will be prone to above-average fire risk," Mr Browning said.
Even the regions to see rain during winter are not completely off the hook.
"Southern Australia is one of the most fire-prone environments in the world," Mr Browning said.
To add literal fuel to the fire, he said La Niña's influence often started to wane as we moved into the second half of summer, which could result in the new growth driven by the early rain drying out and increasing the grassfire risk at the end of summer.
So there will be fires around, but hopefully the climate conditions are more favourable towards rainfall than dry conditions, making it less likely we will see the long campaign fires we saw last year, according to Mr Browning.
La Niña is usually associated with cooler temperatures than its counterpart El Nino, but that doesn't mean heatwaves can be ruled out this season.
Mr Browning said La Niñas brought a different type of heatwave, with less single hot days but rather extended heatwaves of moderate intensity.
Then there's the humidity.
"You combine the heat over an extended period of time, plus that humidity, it can lead to significant health risks," Mr Browning said.
Keep up to date with warnings this season on the ABC Emergency website, Facebook or radio and please heed the advice of your local emergency services.
- AUTHOR: KATE DOYLE