US Climate Prediction Center Announces La Niña Impact on Australia Explained
A La Niña advisory has been recently issued by the US Climate Prediction Center (CPC). This advisory indicates that La Niña conditions are present in the tropical Pacific Ocean. The CPC expects these conditions to persist for several months.
Understanding La Niña
La Niña is one phase of the El Niño-Southern Oscillation (ENSO). The ENSO comprises three distinct phases: La Niña, El Niño, and neutral conditions. During La Niña events, the central and eastern equatorial Pacific Ocean experiences cooler-than-average surface water. This cooling is accompanied by stronger easterly trade winds.
This phenomenon typically leads to increased cloud formation and rainfall over the western tropical Pacific, particularly affecting regions like Australia.
Details from the La Niña Advisory
The La Niña advisory, issued late last week, specifies that conditions are expected to last through December 2025 to February 2026. A transition to ENSO-neutral conditions is likely by January to March 2026. The CPC defines La Niña based on sea surface temperatures in the central equatorial Pacific. These must be at least 0.5°C cooler than average for a minimum of three consecutive months.
The advisory states, “Collectively, the coupled ocean-atmosphere system reflected La Niña conditions.” Clear atmospheric changes are being observed, supporting this declaration.
Divergence in Definitions: CPC vs. BOM
It is essential to note that the CPC’s definition differs from that of Australia’s Bureau of Meteorology (BoM). While the CPC recognizes ongoing La Niña conditions, the BoM maintains that ENSO remains neutral. The BoM requires more significant and prolonged ocean cooling before declaring a La Niña.
As of now, the Bureau’s model suggests that the tropical Pacific is likely to reach La Niña levels briefly in spring but return to neutral conditions by summer. If a La Niña is declared, it may be weak and short-lived.
Potential Impact on Australia’s Weather
La Niña typically enhances rainfall and lowers daytime temperatures across large areas of Australia, especially in northern, central, and eastern regions. However, the impact of weak or borderline La Niña episodes can be unpredictable.
Currently, a La Niña-like pattern appears established but is expected to be relatively weak and short-lived. Other climate drivers, such as the Indian Ocean Dipole (IOD) and Southern Annular Mode (SAM), along with warmer sea surface temperatures near Australia, are anticipated to exert a stronger influence on the Australian climate in the forthcoming months.
Conclusion
While the La Niña advisory from the CPC signals significant climatic changes, variations in definitions between the CPC and the BoM indicate a complex situation. The forthcoming months will reveal the extent of these conditions on Australia’s weather.
