MELBOURNE, Australia – The 2020–21 La Niña is likely to have reached its peak with respect to sea surface temperature patterns in the eastern and central Pacific Ocean, says the Bureau of Meteorology of the Australian Government in its latest update. However, impacts associated with La Niña, such as above average rainfall in eastern and northern Australia, are expected to persist into early autumn, with climate outlooks indicating above-average rainfall is likely across much of the country, particularly in eastern Queensland.
Over the past fortnight the sea surface temperatures across the western and central Pacific Ocean have cooled slightly while those in the eastern side of the basin have warmed. The Southern Oscillation Index continues to remain high with a , well above the La Niña threshold of +7. Model outlooks indicate a return to neutral conditions during the late southern summer or early autumn.
The Southern Annular Mode (SAM) has decreased towards neutral values and is expected to be neutral for the next fortnight. Strongly positive SAM over the last month were driven by an exceptionally strong polar vortex over Antarctica which has largely subsided now.
The Madden–Julian Oscillation (MJO) is located over the Maritime Continent and moderate in strength. Some models indicate it will weaken in the coming week before strengthening again in the Western Pacific Ocean. Along with other tropical wave activity, the MJO can be expected to maintain above-average rainfall and tropical cyclone activity in the Australian region over the coming fortnight.
Climate change is also influencing the Australian climate. Australia’s climate has warmed by 1.44 ± 0.24 °C over the period 1910–2019, while recent decades have seen increased rainfall across northern Australia during the northern wet season (October–April), with more high-intensity, short-duration rainfall events.
