Extract from ABC News
A dangerous storm sweeps over Beerburrum in Queensland on Wednesday evening, in what could be a familiar scene this summer. (Supplied: Doug O'Neill)
Australia is facing one of the hottest summers on record according to the Bureau of Meteorology's (BOM) weather modelling which tips well-above-average temperatures across the country.
The forecast for a scorching summer is largely due to ongoing high ocean temperatures surrounding Australia, a persistent feature which has plagued most of globe since early last year.
The warm seas will not only raise air temperatures, but also boost atmospheric moisture levels, swinging the odds to favour frequent storm outbreaks and above average rain.
Our simmering oceans could also lead to the most active cyclone season in years with the BOM expecting around 11 named storms in the Australian region, including an increased risk of severe (category three or above) systems.
Summer heat to challenge records
Of the past six years, the three which were not La Niña periods took the top three spots as Australia's hottest summers on record, all with mean temperatures more than 1.6 degrees Celsius above the long-term average.
This trend suggests this summer will also produce well above average temperatures — a prediction supported by seasonal modelling.
The BOM's initial summer forecast released this week, shows a greater than 80 per cent chance of minimum temperatures in the top 20 per cent of years – which the BOM label "unusually high temperatures".
The BOM's summer forecast for minimum temperatures shows a high risk of unusually hot nights. (ABC News)
While muggy, sweaty nights are the hot tip, the outlook for maximums is less extreme.
The BOM's modelling indicates a 30 to 60 per cent chance of unusually-high daytime temperatures for the majority of Australia, although when setting a lower bar of above median maximums, this probability increases to greater than 80 per cent in most areas.
Conversely, the chance of summer temperatures in the bottom 20 per cent of years is almost nationwide below 10 per cent.
There is a high chance of unusually hot maximums according to the BOM's summer forecast. (ABC News)
The bullish forecast is partly the result of exceptional heat in our surrounding oceans.
The sea surface temperature (SST) is currently warmer than normal off every Australian coastline apart from small pockets of south-west WA, and waters are as much as 2.5C above average off the coast of Broome.
Warm oceans directly heat the air just above the surface but can also influence the temperature inland during periods of onshore winds.
The other key factor is climate change, which in recent decades has ensured our summers are perpetually warmer than normal, except for strong La NIña years like 2010, 2011, 2020 and 2022.
So just how hot could this summer become?
The BOM's seasonal model predicts the mean temperature across the country will land at about 1.5C above the baseline 1961—1990 average, which would comfortably position the upcoming summer in the top five hottest on record.
A sweltering summer also amplifies the risk and severity of extreme hot days along with dangerous heatwaves (spells of at least three days with abnormally oppressive weather).
Similarly, the risk of bushfires increases when temperatures are high, and while fires can occur anywhere after a spell of hot and dry weather, a heightened threat is emerging this summer across drought affected regions of southern SA and Victoria where rainfall in 2024 has been in some locations the lowest on record.
Warm seas to fuel humidity and rain
Australia has already recorded its wettest first nine months of a year since 2011, and above average rain is likely to continue for the remainder of the year, and through January and February.
Without a global climate driver like La Niña fully established, the wet outlook hinges more on local conditions, aided by the warmer seas which will promote cloud and rainfall thanks to additional evaporation.
Oceans are currently warmer than normal surrounding Australia, providing the fuel for a hot, thundery summer. (ABC News)
While the swing to favour rain has been consistent for several months, the confidence in the forecast is only moderate thanks to the variable nature of precipitation.
For example, while last summer was hot, the remnants of the 2022 Hunga-Tonga volcano eruption shifted wind patterns to generate high rainfall in the east and north.
So how likely is a wet summer?
The BOM's outlook shows up to a 70 per cent chance of above median rain for parts of the east, and only displays a swing to drier conditions in western Tasmania.
The summer rain outlook favours above median falls across most of Australia. (ABC News)
When it comes to weather forecasting though, it's always wise to seek a second opinion.
The most respected weather model worldwide, the ECMWF, concurs with the BOM's model that most of Australia is likely to be wetter than normal — also as high as 70 per cent in parts of the east.
Another forecasting method is to survey dozens of models and take the average, and again this ensemble output displays a 60 to 70 per cent chance of above median rain this summer.
With increased rain, also comes a heightened risk of thunderstorms, since a significant amount of precipitation in the warmer months falls from storm clouds.
The most storm prone region of Australia is the northern tropics where up to 90 days per year have lightning and thunder, however the area most prone to severe thunderstorms which bring a combination of hail, damaging winds and flash flooding is south-east Queensland and north-east NSW.
Brisbane sees more severe thunderstorms than other Australian capitals — an average of around 20 days per year with a severe storm within a 150-kilometre radius of the city, and this season could see that number grow closer to 25 days.
A storm rages across south-east Queensland this week as the official storm season gets underway. (Supplied: Kevin Sturgess)
Increased threat of strong tropical cyclones
Warm oceans are associated with tropical cyclones, since a prerequisite for their formation is SSTs above 26.5C.
Despite this threshold already being exceeded off our northern coastline, the BOM's forecast is for an average season, meaning around 11 tropical cyclones in the Australia region, and four making landfall.
While this estimate may seem conservative considering the warm waters, Australia has not recorded an above average cyclone season in nearly two decades, so 11 systems would be noticeably more active relative to recent years.
The reduction in cyclones this century is due to climate change, however the number of severe systems has remained steady, and the added energy boost this season due to the warm oceans has prompted the BOM to predict an increased likelihood of category three or above storms.
The BOM are also warning of an increased threat of storm surges from tropical cyclones due to rising sea-levels.
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