A strong El Niño is under way and models suggest it could become the strongest since reliable records began in 1950 — but the Bureau of Meteorology is warning farmers that the strength of the event does not translate directly into how dry or hot Australia will be. Its explainer, republished by Beef Central, sets out why.

The benchmark is the 1982–83 El Niño, when central tropical Pacific sea-surface temperatures peaked about 2.6 °C above average in January 1983. Forecasts have the current event exceeding that, possibly at more than 3.0 °C above average. Yet every El Niño is different: a strong event can bring only modest effects in some regions, while a weak one can hit hard.

The Bureau's own recent history makes the point. The moderate-to-strong El Niño of spring 2023 coincided with Australia's driest August–October on record, but a strong positive Indian Ocean Dipole (IOD) did much of that drying; by late 2023 El Niño's influence had faded, and east-coast storms and four tropical cyclones delivered above-average summer rain.

Other influences in play now include the IOD — neutral today, but every model has a positive phase developing later in spring, which raises the odds of a dry spring in southern and eastern Australia — as well as unusually warm seas around the continent, the northern wet season and long-term climate change, which is increasing the likelihood of heatwaves, flash drought, dangerous fire weather and heavy rain alike.

This year has not looked like a classic El Niño. It began with an active La Niña and a very wet northern wet season, switched rapidly to El Niño by June, and then saw north-west cloudbands, strong cold fronts and a negative Southern Annular Mode bring an unusually wet winter to parts of the interior and south — though large parts of the east and Western Australia's south-west stayed dry. National water storages were about 71 per cent full in early September; capital-city storages are above 80 per cent except Melbourne (about 70) and Perth (about 40). Drier-than-average areas this year include north-eastern New South Wales into south-eastern Queensland, the south-west of Western Australia and parts of Tasmania.

As at 10 September the long-range outlook has most of Australia likely to see above-average temperatures in the coming months, and a mixed October–December rainfall picture with below-average rain likely for parts of the south-east, including southern New South Wales, Victoria and Tasmania. El Niño's influence on rainfall usually weakens around early summer, and the Bureau says summer forecasts will firm as spring progresses.

Source: Beef Central