Australia Weather News

Australia is likely to face a hotter-than-normal summer, according to the Bureau of Meteorology's (BOM) weather modelling, as parts of Australia brace for what could be record-level October heat over the coming days.

The long-range forecast, which now goes up to the end of February, is the first glimpse of what the season is shaping up to look like.

It is still early days.

But at this stage the forecast is tipping warmer-than-normal temperatures for most of Australia, except for coastal parts of New South Wales.

It is the nights that are looking the most dramatic, with the initial forecast showing a greater than 80 per cent chance of minimum temperatures being "unusually high".

"Because we are seeing increased chances of it being unusually warm for both overnight and daytime temperatures, that there's an increased chance of extreme heat," BOM senior climatologist Felicity Gamble said.

Meanwhile, November rainfall is likely to be above average for much of northern and eastern Australia.

But by the time the forecast gets to summer, the only places leaning toward wetter-than-normal conditions are far north Queensland and Western Australia's Wheatbelt.

For everywhere else, there is still a wide "spread" in what the model is showing for rain, according to Ms Gamble.

This can mean there is as much of a chance of it being unusually dry as it is average, or usually wet in some areas.

In other words, they do not know yet.

This is not particularly surprising given the "tug of war" happening between climate drivers at the moment.

On the one hand, record warm oceans around Australia, combined with a couple of major rain-bearing climate drivers to the west and east, would typically push toward a wetter spring and summer.

But on the other hand, they are up against a rare, sudden stratospheric warming event high above Antarctica, which heavily favours dry and warm conditions for southern Australia.

"So it will be interesting to see which one ends up dominating during the summer months," Ms Gamble said.

Bushfires, floods and cyclones 

A lack of rain has seen soils start to dry considerably across Victoria, New South Wales and central and southern Queensland in recent weeks.

Several fires have already been burning across these districts.

Ms Gamble said going into summer, the drying landscape could pave the way for an increased risk of bushfires if the trend continued.

"We have seen quite an abundance of fuel growth following that winter rainfall, particularly along eastern parts of Australia … just due to that really quite significant winter rainfall that we had," she said.

"This recent dry spell that we've had over the last few weeks has definitely seen a drying of soils across much of New South Wales, northern Victoria and eastern Victoria as well."

But the weather is not the only thing that matters for bushfire risk, according to Ms Gamble.

Other factors like controlled burns, recent fire history and the type of vegetation also play into the bushfire season.

The official bushfire outlook for summer, which combines all of this information, will come out in late November.

Warm oceans stoke severe storm risk

Simmering oceans around Australia could also increase the risk of powerful storms.

Late spring is the peak time for extreme storms, particularly across parts of eastern Australia such as Queensland, northern New South Wales and the tropics.

Queensland has already been pelted with giant hail up to 8cm in diameter.

Storms are hard to predict this far out because they are very much driven by the weather on any given day. Even in shorter time scales, they can be tricky to forecast.

But Australia's sea surface temperatures have been at record highs, or close to it, for over a year and are expected to remain that way.

Ms Gamble said the increased evaporation coming from warm oceans could provide an extra source of moisture and energy to storms, making them worse when the right weather system came along.

"We've still got a lot of heat in the oceans around Australia and that's forecast to persist through summer, potentially warm further," she said.

However, the dry soil coupled with the unremarkable rainfall forecast could lower the risk of riverine flooding.

"We haven't seen quite such a wet spring, at least so far, so I think that that risk is potentially eased a little bit," Ms Gamble said.

But that risk can change quickly if a big rain system comes along. 

The risk of flash floods, triggered by short, heavy rainfall events, can also happen at any time.

Observations have shown that these types of rainfall events are becoming more extreme with climate change.

BOM ditches cyclone outlook

The number of cyclones is something the BOM is making no call on anymore, having "retired" the seasonal cyclone outlook.

The bureau said this was because it simply was not getting it right enough of the time.

Ms Gamble said the model was based on the historical relationship between El Niño and La Niña and the number of cyclones, but climate change meant the past could not predict the future reliably anymore.

"Things are changing, atmospheric patterns are changing. In the last two to three years, we've seen record or near-record levels of sea surface temperatures across the globe," she said.

"When you add in these unprecedented components to a statistical model that's only looking at past relationships, it loses its capacity to be a reliable predictor of those."

On top of that, the BOM said, while interesting, it was not particularly useful to know how many cyclones there would be in a season, when it only took one to do damage.

Instead, they are now focusing on giving advice about the cyclone season in general and when they see the highest number of cyclones.

They are also encouraging people to keep up to date with the more regular tropical climate updates issued each fortnight, which can indicate whether or not the chance of a cyclone is increased over the coming weeks.

This is true for the long-range outlooks in general, which become more accurate the closer you get.

What is forecast now can totally change once summer actually starts.