The weather bureau has issued an El Nino watch and warns parts of Australia could face droughts later in 2023, after years of heavy rain and floods in the country’s east.
After two years of heavy rain and record floods across the eastern states, La Nina is finally over but authorities warn more extreme weather could be on the way in the form of a drought.
The Bureau of Meteorology issued an El Nino watch on Tuesday, after long-range forecasts revealed a 50 per cent chance of the warmer, drier weather pattern occurring this year.
More neutral weather is expected throughout autumn and winter, while hotter conditions could return by summer, the Bureau of Meteorology’s Andrew Watkins said.
“Long-range forecasts show there’s an increased chance of below average rainfall for most of Australia during autumn 2023,” Dr Watkins said.
“But the northern wet season, including the tropical cyclone season, for northern Australia continues during March and April, so there remains the chance of tropical weather systems bringing heavy rain at times to the north.”
Authorities said the possibility of El Nino meant an increased risk for bushfires.
There have been 27 El Nino events since 1900, and about 18 of those were affected by widespread winter-spring drought.
La Nina refers to the cool and often rainy phase of the ocean-atmosphere phenomenon meteorologists call the El Nino-Southern Oscillation, while El Nino is the warm, dry phase.
Scientists unpick Australia’s year of weather disasters
Leading climate scientists have delved into some of the most extreme weather events Australians endured last year, and there were plenty to choose from.
Some of the nation’s top client scientists have unpicked the factors behind Australia’s disastrous and deadly year of weather and climate extremes.
It goes without saying that devastating rain and flooding events overshadowed all others in 2022 after a third consecutive La Nina smashed rainfall records around the country.
While the east coast was awash with water, plenty of other events were happening including extreme heat in the west and the Antarctic, as well as wild winds and hail storms.
Here’s a look at some of the events examined in the State of Climate and Weather Extremes 2022 report.
The authors, from the Australian Research Council Centre of Excellence for Climate Extremes, hope it will help governments and the public understand the complexity and nature of the climate extremes being witnessed.
|
Flooding forces residents out of homes for weeks
10 News First – Disclaimer |
|
Devastating floods in Qld and NSW
The northern NSW town of Lismore was at the heart of a devastating series of storms that flooded south-east Queensland and NSW in the first half of 2022.
Rainfall records were smashed, with some regions experiencing more than five times what they’d normally get in a month. It was the costliest flood in Australia’s history, with more than 20 lives lost.
In Lismore, flood waters surged two metres above the previous record, forcing families onto rooftops to survive.
Scientists say the floods resulted from a combination of meteorological phenomena.
First, the La Nina weather pattern meant catchments were already sodden and primed for flooding.
Then, in late February, a Rossby wave triggered the development of multiple rain-producing weather systems.
Rossby waves are building blocks of weather and are high-altitude, planetary-scale waves that largely drive a range of weather at the surface level, according to the report.
They are disturbances in planetary waves, such as the jet stream over Australia.
As the waves get bigger, they can break, just like at the beach.
A Rossby wave breaking event, south of Australia, was one of the main drivers of the weather that inundated so much of Queensland and NSW in February and March.
Sydney’s wettest year
Just three weather events delivered almost half of the staggering amount of rain Sydney copped in 2022.
The city’s wettest year on record had 2530 millimetres of rain – more than double the average.
Atmospheric rivers – which work like conveyer belts and deliver relentless streams of moisture-laden air from the warm Coral Sea – and east coast lows were largely to blame.
Three events – in February/March, July and October – were responsible for 40 per cent of the rain. The result was flash flooding across Sydney, significant flooding of the Hawkesbury-Nepean catchment, and forced the evacuation of 85,000 people.
A recent study by the ARC Centre of Excellence suggests the number of atmospheric rivers may increase by 80 per cent by the end of the century under moderate and high emissions scenarios.
Record heat in WA
A complicated mix of weather events led to falling heat records in Western Australia in the summer of 2021-22.
In January, a strong high-pressure system over the Great Australian Bight brought hot, dry weather from the desert to Perth as a coastal trough blocked sea breezes.
The result was six consecutive days above 40 degrees in Perth – the longest such run for any month in 123 years of observations.
The Pilbara region also endured a record-breaking heatwave, with the town of Onslow equalling Australia’s hottest day on record when the mercury hit 50.7 degrees on January 13.
In December, suppressed tropical activity meant Marble Bar, also in the Pilbara, briefly became the hottest place on the planet, reaching 46.2 degrees.
Heatwaves are now one of the most deadly natural hazards in Australia and they are expected to continue to worsen as the climate warms.
Antarctica feels the heat
Last year was one of record sea ice loss and record heat in Antarctica.
In March, a heatwave hit resulting in temperatures of more than 50 degrees above average in some areas.
The same month also brought the collapse of a part of the East Antarctic ice shelf the size of New York City, with the heat also driving the collapse of the Conger ice shelf.
The Antarctic also broke records for loss of sea ice in 2022 and that has continued, with sea ice extent falling to a record low in 2023.
The 2023 Antarctic sea ice minimum extent was about 40 per cent less than the average between 1981 and 2010.
That’s alarming because Antarctic sea ice reflects sunlight and influences air-sea interactions and ocean circulation, and is an important habitat for krill, which underpins the Southern Ocean food web.
Sea ice also holds Antarctic ice shelves in place, something that helps ward off sea level rise.
Wild winds in a double day of trouble
On the same day last November, severe thunderstorms lashed parts of South Australia and the Northern Territory, leaving trails of damage.
The storms were part of a broad region of severe weather that extended through central Australia, and while both produced severe winds they were very different.
Adelaide was hit by a line of storms that stretched for 140km, producing gusts of more than 100km/h, causing transmission lines to fail and cutting off the state from the national grid.
In Alice Springs, roofs were lost to a single storm that was 10 kilometres wide and produced a microburst – a strong wind event common over regions that have a deep layer of hot, dry air near the surface.
Scientists say more research is necessary to ascertain how climate change will impact events like these in the future.
Hail hammers three states
Destructive hail storms hit Victoria, Queensland, and NSW last year and farmers, in particular, copped a belting.
In the first couple of weeks of 2022, large hail caused widespread damage to potato crops in Victoria and citrus and grape crops in NSW. Some grape growers lost half their crops.
In October, near Rockhampton in Queensland hail the size of cricket balls fell.
The following month hailstorms tore across Victoria’s Mallee region, leaving millions of dollars in crop and property losses. Port Macquarie was also pelted causing significant property damage.
Climate change affects atmospheric properties associated with hail.
Experts believe hailstorms might be less frequent but more severe as the climate warms, but also warn the effect on hail remains highly uncertain.
-AAP
