Home Climate Change La Niña past ...

La Niña past peak, but influence is expected to continue in the broader Pacific Basin, says Bom

La Niña Alert ENSO

MELBOURNE, Australia – The 2020–21 La Niña continues to influence Australia and the broader Pacific Basin says the Bureau of Meteorology (BOM) of the Australian Government. In terms of typical indicators of La Niña, however, this event has peaked. Climate model outlooks indicate the El Niño–Southern Oscillation (ENSO) will return to neutral during autumn, that is, neither La Niña nor El Niño. The wetter influence from La Niña is likely to continue for the shorter term, with three-month climate outlooks indicating above average rainfall is likely for parts of northern Australia.

In the tropical Pacific Ocean, sea surface temperatures remain similar to last fortnight’s, with a cooler than average tongue of water still present across the central to western Pacific. Beneath the surface, cooler water is still present. In the atmosphere, the Southern Oscillation Index (SOI) still clearly remains within the La Niña range, and cloudiness near the Date Line is below average, a typical La Niña atmospheric pattern.

The Madden–Julian Oscillation (MJO) is currently located over the central Pacific Ocean and is expected to move eastwards during the coming fortnight towards the tropical Americas. When the MJO is over the Americas at this time of the year, tropical areas across northern Australia would typically be drier than average.

The Southern Annular Mode (SAM) has recently been positive, but forecasts expect a return to neutral values in coming days. Typically, a positive SAM during summer increases the chance of above average rainfall across parts of eastern Australia. During the autumn months, SAM has little influence on Australian rainfall.

The Indian Ocean Dipole (IOD) is currently neutral. The IOD typically has little influence on Australian climate from December to April.

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.