La Niña continues and is near its peak, according to the BoM
Note. La Niña is a climatic phenomenon which is part of a natural-global climate cycle known as El Niño-Southern Oscillation (ENSO, El Niño-Southern Oscillation, ENSO for its acronym in English). This global cycle has two extremes: a warm phase known as El Niño and a cold phase, precisely known as La Niña. When there is a regime of strong trade winds from the west, equatorial temperatures decrease and the cold phase or La Niña begins. When the intensity of the trade winds decreases, the surface temperatures of the sea increase and the warm phase begins, El Niño.
La Niña continues in the Pacific
Autumn, in the southern hemisphere, is the typical time of year when ENSO events fade and become neutral again. La Niña increases the chance of above-average rainfall across much of northern and eastern Australia during the summer.
Cooler-than-normal sea surface temperatures persist across the central and eastern tropical Pacific, with warmer-than-average waters in northern Australia.
Something is changing
The coldest subsurface water remains in the eastern tropical Pacific, supporting the cooler waters at the surface. But nevertheless, these cooler groundwaters are starting to warm up. In the atmosphere, patterns remain generally La Niña-like, with decreased cloudiness near the date line and near-average or slightly increased trade winds. The Southern Oscillation Index (SOI) has decreased in magnitude over the last fortnight; however, this is likely related to the transient tropical climate and not to a broader climate signal.
The Madden–Julian Oscillation (Madden–Julian Oscillation , MJO) has weakened after being in the central and eastern Pacific for the past two weeks. Some models predict a strengthening over the western Pacific in the coming days, which would normally lead to increased cloudiness and rain over the eastern maritime continent, including northern Australia and the southwestern Pacific.
The index Southern Annular Mode (SAM) has briefly dipped to negative levels. It is expected to approach positive levels during the rest of January and until the first week of February. A positive SAM during the summer generally brings wetter weather to parts of eastern Australia, but drier than average conditions for western Tasmania.
The Indian Ocean Dipole ( Indian Ocean Dipole , IOD) permanece neutral. The IOD typically has little influence on global weather from December to April.
Climate change continues to influence Australian and global weather. Australia’s climate has warmed by around 1.44°C over the period 1910-2019. Precipitation in northern Australia during the wet season (October-April) has been increasing since the late 1990s. duration, especially in northern Australia.
BoM, Australian Meteorological Office