La Niña Officially Declared as Summer Approaches Australia

Key Takeaways

• La Niña has been declared off Australia, just days ahead of summer, but it is expected to be weak and short-lived.
• The event is not expected to have a significant impact on the weather due to a counteracting weather phenomenon called the negative southern annular mode.
• The negative southern annular mode is a shift in strong westerly winds over Australia that can counteract the influence of La Niña’s easterly winds.
• La Niña is expected to bring increased rainfall, storms, and tropical cyclones to the northern and eastern parts of Australia, but the impact is likely to be minimal.
• The Bureau of Meteorology’s long-range summer weather forecast predicts near or below average rainfall and abnormally warm days for much of the country.

Introduction to La Niña
The Bureau of Meteorology has declared that La Niña is underway off Australia, just days ahead of summer. This declaration comes after conditions consistent with the weather phenomenon have been observed in the Pacific Ocean since early October. La Niña is a phase of the Pacific Ocean phenomenon called the El Niño–Southern Oscillation, which affects weather patterns roughly every two to seven years. The event occurs when equatorial winds become stronger, changing the ocean currents, and is synonymous with increased rainfall, storms, and tropical cyclones in the northern and eastern parts of Australia.

La Niña Declaration and Impacts
The Bureau of Meteorology’s La Niña declarations are mostly retrospective, meaning conditions need to be present in the ocean and atmosphere for some time before it can be determined that the event is occurring. The declaration comes after warmer-than-average waters were observed across much of the Australian region, with sea surface temperatures the second warmest on record for October. Meteorologists forecast that the unusually warm conditions are likely to continue from December through to February, particularly for the east coast. However, this year’s La Niña appears to be quite weak and forecast to be short-lived, with levels returning to neutral by early 2026.

Counteracting Weather Phenomenon
One of the reasons why La Niña is not having too much of an influence on the weather is because of the ongoing negative southern annular mode in the Southern Hemisphere, which has been in place since early October. The southern annular mode is a shift in strong westerly winds over Australia, which can counteract the influence of La Niña’s easterly winds. This counteracting phenomenon is expected to continue into early summer, minimizing the impact of La Niña on the weather. The Bureau of Meteorology’s latest long-range outlooks predict near or below average rainfall and abnormally warm days for much of the country this summer.

El Niño–Southern Oscillation and Climate Drivers
La Niña is one of the phases of the El Niño–Southern Oscillation, which affects weather patterns roughly every two to seven years. The phenomenon is considered one of the most important climate drivers in our region, having a large impact on Australia, as well as every other continent in the world, particularly South America, Asia, and Africa. El Niño and neutral are the other phases of the El Niño–Southern Oscillation, with El Niño typically leading to drier conditions, higher temperatures, and a greater risk of heatwaves and bushfires in northern and eastern parts of the country. Understanding the El Niño–Southern Oscillation and its phases is crucial for predicting and preparing for extreme weather events.

Conclusion and Forecast
In conclusion, while La Niña has been declared off Australia, its impact is expected to be minimal due to the counteracting negative southern annular mode. The Bureau of Meteorology’s long-range summer weather forecast predicts near or below average rainfall and abnormally warm days for much of the country. It is essential to stay informed about the latest weather forecasts and warnings to prepare for any potential extreme weather events. As the summer months approach, it is crucial to be aware of the potential risks and take necessary precautions to stay safe. The Bureau of Meteorology will continue to monitor the situation and provide updates on the La Niña event and its impacts on the weather.