MELBOURNE, Australia – Despite some warming of sea surface temperatures in the central and eastern tropical Pacific Ocean over the past fortnight, La Niña remains at moderate levels reports the Bureau of Meteorology of the Australian Government in its latest Climate Driver Update. Model outlooks suggest the current La Niña is approaching its peak, with a likely return to neutral conditions during the late southern summer or early autumn.
The Southern Annular Mode (SAM) is strongly positive. While positive SAM often occurs during La Niña influence, the current event is also being driven by an exceptionally strong polar vortex over Antarctica.
Positive values are expected until at least early 2021. A positive SAM at this time of year typically increases the chance of rainfall in eastern Australia.
The Madden–Julian Oscillation (MJO) is weak, and currently located over the eastern parts of the Maritime Continent. It is forecast to move east and remain weak over the next fortnight, before possibly strengthening again in the western Indian Ocean in January.
Climate change is also influencing the Australian climate. Rainfall across northern Australia during its wet season (October–April) has increased since the late 1990s, with a greater proportion of high intensity short duration rainfall events.
Nationally averaged rainfall for December 2020 is likely to be in the ten wettest on record while climate outlooks for January to March 2021 indicate rainfall is likely to be above average for most of the eastern third of the country.
