MELBOURNE, Australia – El Niño continues in the tropical Pacific Ocean. Model forecasts and observations indicate sea surface temperatures in the central tropical Pacific have peaked and are now declining, reports the Bureau of Meteorology of the Australian Government in its latest update.
Sea surface temperatures in the tropical Pacific are expected to return to neutral El Niño–Southern Oscillation (ENSO) levels in the southern hemisphere autumn 2024.
Some atmospheric indicators, such as cloudiness near the Date Line, are close to normal levels. The Southern Oscillation Index (SOI) has recently increased. The SOI tends to be more volatile during the northern Australian wet season as transient tropical systems can influence the 30-day SOI.
The typical drying influence of El Niño on Australia’s climate usually reduces during summer, especially in the east; however, below median rainfall is still often observed in north-east Australia. As we have seen this year and through historical data, high-impact rainfall events can occur during El Niño years, particularly during October to April when severe storm frequency peaks.
The Southern Annular Mode (SAM) is currently positive. It is expected to weaken to neutral levels over the coming fortnight. SAM has been positive for much of December and January. During summer, positive SAM increases the chance of above average rainfall for parts of eastern NSW, south-eastern Queensland, eastern Victoria, and north-eastern Tasmania, but increases the chance of below average rainfall for western Tasmania. Rainfall increases are due to the positive SAM shifting westerly winds further south, increasing onshore flow over south-east Australia. Neutral SAM has little influence away from normal on Australian rainfall patterns.
The positive Indian Ocean Dipole (IOD) event has weakened from the strong values seen in late 2023. IOD events typically breakdown as the monsoon trough shifts south into the southern hemisphere. Due to the strength of the positive IOD in 2023, the event decay has been later than usual. Model forecasts and observations suggest the positive IOD is near its end, with the majority indicating the IOD index will fall below +0.4 °C in the coming weeks.
The Madden–Julian Oscillation (MJO) is currently over the Maritime Continent. International climate models suggest it is likely to move eastwards and weaken as it moves towards the Western Pacific, with most models forecasting it to restrengthen to between a moderate to strong level once in the Western Pacific. At this time of year, when the MJO is in the Maritime Continent and the Western Pacific, the chance of above average rainfall typically increases across northern Australia.
The World Meteorological Organization (WMO) has confirmed that 2023 was the warmest year on record. The WMO estimated global temperatures in 2023 were 1.45 ± 0.12 °C above the 1850–1900 average, exceeding the previous record warm years of 2016 and 2020, with 1.29 ± 0.12 °C and 1.27 ± 0.12°C respectively. Individually, the past 10 years have been the warmest 10 years on record.
Australia’s climate has warmed by 1.48 ± 0.23 °C between 1910, when national records began, and 2022. There has been an increase in extreme heat and fire weather associated with the warming. There has also been a trend towards a greater proportion of rainfall from high intensity, short duration rainfall events, especially across northern Australia.
