By Jo Clarke

August 17, 2022 - The Australian Bureau of Meteorology (BoM) has upgraded its La Nina watch for 2022-23 to an alert, increasing the probability of another wet year to 70pc from 50pc.

This will be the third La Nina weather trend in a row, increasing the chances of above average rainfall across already saturated ground and filled water storage in east and north Australia.

Heavy rainfall, storms, flooding and saturated ground in New South Wales (NSW) and Queensland have disrupted coal mining, railing and shipping, as well as coal-bed methane (CBM) development to supply gas to export LNG and domestic markets. It also delayed the harvest in parts of these states last year and caused large volumes of wheat and barley to be downgraded to feed grains from milling wheat and malting barley.

The change in the El Nino Southern Oscillation outlook to a La Nina watch increases the probability of this weather pattern occurring to around triple the normal likelihood. A La Nina is associated with an increased chance of above average rainfall across east and north Australia during September-April, with lower or average rainfall in Western Australia state where the majority of the nation's iron ore and wheat are produced.

Australia's coal exports were down by 8pc in the 2021-22 fiscal year to 30 June compared with 2019-20, which was the last year that was not a La Nina. The drop was despite record-high thermal and metallurgical coal prices during 2021-22, which would usually result in increased supplies if mining firms were not struggling with the effects of flooding and waterlogged pits. Some mining firms have built more water storage over the past year, although they are starting from a position of more water on site than a year earlier.

The BoM only called the end of the 2021-22 La Nina in June, while July was much wetter than average with flooding cutting coal exports out of the NSW port of Newcastle.

The BoM has moved to a La Nina alert much earlier this year than last year, implying that it has more confidence at this point than it did a year ago that another wet southern hemisphere spring and summer is on the way.

A La Nina is also often associated with increased likelihood of tropical cyclones making landfall in north Australia, with cyclones often closing oil and gas infrastructure, iron ore and coal export facilities, along with major rail and road corridors.