By Jo Clarke

June 22, 2022 - The Australian Bureau of Meteorology (BoM) has called a La Nina watch for 2022-23 and forecast the probability of another wet year at 50pc, as it finally calls the end of the 2021-22 La Nina that has disrupted coal, gas and agricultural production on the country's east coast.

The change in the El Nino Southern Oscillation (Enso) outlook to a La Nina watch increases the probability of this weather pattern occurring to around double 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 is produced.

The BoM called the end of the 2021-22 La Nina, which has contributed to flooding in key coal, gas and agricultural regions in Queensland and New South Wales (NSW). It maintains its expectations of a wetter than average July-September for these states because of the likely development of a negative Indian Ocean dipole. The BoM did not release a La Nina watch until September last year, with this early change in the Enso outlook possibly showing greater likelihood of a La Nina event materialising.

The 2022-23 southern hemisphere summer will be the third La Nina in a row, with any additional rain falling on already saturated ground and full water storage capacity in many regions of NSW and Queensland.

The La Nina event over the 2020-21 summer led to some minor disruption to mining operations because of flooding and an above average number of storms, including one that caused major damage to a shiploader at the key NSW port of Newcastle. The previous major La Nina event in Australia was during 2010-11 when flooding in late 2010 and early 2011 caused several coal mining firms to declare force majeure in early December, which stayed in place until February. The effect was most pronounced in hard and semi-soft coking coal exports, although thermal coal export growth also slowed over the period before rebounding strongly in 2012-13.

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.