Australia & New Zealand: Exceptional water deficits to emerge in Tasmania

26 April 2017

The Big Picture
The 12-month map (below) indicates severe to exceptional water deficits in South Australia, Queensland, Victoria, Tasmania, and New Caledonia, and moderate deficits in New South Wales and central Australia.

Surpluses reaching exceptional severity are forecast for the Kimberley Plateau in the northwest and in northeastern Queensland.

Impacts
Heavy rain and flooding from a category 4 storm, Cyclone Debbie, that hit coastal Queensland and New South Wales, Australia and North Island, New Zealand in late March left 6 dead, at least 100,000 without power, and early estimated damages of A$1 billion (~US$770 million) in Australia alone. The disaster zone stretched 1,000 km (600 miles) along eastern Queensland and NSW. Several days later water levels on the Fitzroy River in Rockhampton peaked at around 9 meters (30 feet) flooding streets, shops, homes, and closing the airport for 6 days. Floodwaters reached the roofs of cars in Gold Coast, Queensland and residents of Lismore boated between houses. The National Farmers Federation is predicting crop losses of A$1 billion.

Continuing rainfall a week later led to a suspension of flights at Wellington Airport in New Zealand and left 10,000 homes without power in Auckland.

Forecast Breakdown
The 3-month maps (below) for the same 12-month period show the evolving conditions.

As is apparent in the top two maps, water anomalies – both deficits and surpluses – are forecast for much of Australia for the six-month period ending June 2017. Thereafter, the extent and severity of anomalies is expected to diminish considerably.

The April through June map indicates significant improvement as widespread and exceptional water anomalies are no longer evident in South Australia, Queensland, and New South Wales. However, severe to exceptional deficits are expected to emerge throughout Tasmania and in Western Australia, particularly from Perth south. A vast expanse of moderate deficits is forecast for central Australia, and exceptional deficits will persist in Northern Territory’s Top End near Darwin. Moderate deficits are expected to persist in New Caledonia and may emerge in southern South Island, New Zealand.

Moderate to exceptional surpluses will continue to emerge in eastern Queensland from Mackay past Rockhampton. Surpluses in the Kimberley Plateau in the northwest will diminish in extent and severity and begin transitioning as deficits emerge.

From July through September primarily abnormal deficits will prevail over most of the country. However, severe to extreme deficits will continue to emerge in eastern Tasmania, Western Australia from Perth south, and in Northern Territory’s Top End near Darwin. Surpluses in the Kimberley Plateau will continue to diminish and transition. Surpluses in eastern Queensland will also diminish.

The forecast for the final months – October through December – indicates conditions similar to the prior three months.

(It should be noted that forecast skill declines with longer lead times.)