Australia & New Zealand: Surplus persists in N, SE Australia

25 April 2024

THE BIG PICTURE
The 12-month forecast ending in December 2024 indicates that intense surplus will occur in most northern and central regions of Australia, with exceptional deficits diminishing in portions of the country near its western coast. Exceptional deficits are expected to emerge in Tasmania, as well as in pockets across New Zealand.

Severe to exceptional surpluses are expected in the following regions:

Northern Territory, widespread throughout most northern and central regions of the territory.
Northern Queensland, with exceptional surpluses appearing primarily throughout the Yorke Peninsula.
Eastern to southeastern New South Wales, spreading through Wollemi National Park and into coastal regions of the Southern Tablelands.
Western Australia, near Lake Carnegie.

Severe to exceptional deficits are expected in the following areas:

Northern and southern Western Australia, in northern coastal regions near Port Hedland, as well as in coastal regions near the city of Albany.
Tazmania, widespread throughout western and central portions of the country.
New Zealand, with isolated pockets of exceptional surplus appearing near the cities of Dunedin and Nelson.

The 3-month maps (below) show the evolving conditions in more detail.

FORECAST BREAKDOWN
The forecast through June 2024 anticipates that surpluses will continue throughout central and northern portions of Northern Territory and northern Queensland. Similarly intense surpluses are expected to continue in Western Australia near Lake Carnegie. Exceptional deficits are expected to occur along the southwestern coast of Victoria, as well as throughout Tasmania. Deficits in New Zealand near Dunedin, Portland, and Wellington are expected to continue.

From July through September 2024, surpluses in Northern Territory and Queensland are expected to mostly change into transitional conditions, covering most of both regions. Severe to extreme surpluses are expected to persist in central Northern Territory and Queensland. Moderate to severe surplus is anticipated to emerge in east-central regions of New South Wales. Exceptional deficits may emerge in northern portions of Western Australia. Deficits in Tasmania are expected to downgrade in size and intensity, but endure in most regions of the country.

The forecast for the final months – October 2024 through December 2024 – indicates that intense surpluses may return in northern to central Queensland and Northern Territory. Similarly intense surpluses may expand throughout New South Wales and southeastern regions of Queensland. Southern Tasmania is expected to observe severe to extreme deficits. Southernmost regions of New Zealand are expected to observe an emergence of moderate to severe deficits.

Please note that WSIM forecast skill declines with longer lead times.

IMPACTS
On April 5th, Sydney’s Warragamba Dam began spilling due to major rainfall in the area over the course of 24 hours. This deluge caused thousands of citizens to evacuate their homes and pumped the equivalent of 80,000 Olympic-sized swimming pools downstream every single hour of the incident. More than 150 people were rescued from floods on Saturday, the New South Wales State Emergency Service said, adding that 72 rescues took place in Sydney.

The same day, Australian authorities reported that 152 people had been rescued from floods after intense rainfall hit eastern regions of New South Wales. Authorities said 72 people were rescued from Sydney, with almost 15 evacuation orders announced statewide. “Flood levels in some of the rivers particularly in western Sydney are continuing to rise,” New South Wales Premier Chris Minns said in a televised conference. The region endured nearly a month’s worth of rainfall, nearly 4.4 inches over 24 hours.

A man was found dead after storms and heavy rains hit Queensland, causing widespread flooding in the area. Authorities found the 71 year old man in a suburb of the city of Greenbank, which was one of multiple Queensland sites hit with more than 100 mm of rainfall in merely one hour, causing 30 road closures across the state. These storms continued north and are headed for northern regions of the state, in an event BoM senior meteorologist Dean Narramore calls a “black nor’easter.” “When you have these big coastal troughs, the sunshine would disappear,” said Narramore. “You get these really dark clouds moving along the NSW coast, really strong onshore winds as well, and it will bring widespread heavy and flooding rain.”

NOTE ON ADMINISTRATIVE BOUNDARIES
There are numerous regions around the world where country borders are contested. ISciences depicts country boundaries on these maps solely to provide some geographic context. The boundaries are nominal, not legal, descriptions of each entity. The use of these boundaries does not imply any judgement on the legal status of any territory, or any endorsement or acceptance of disputed boundaries on the part of ISciences or our data providers.

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