Is La Niña Really Coming? We say yes then no.
- Simon Hutt
- Dec 2
- 3 min read
A clear, simple breakdown of what BoM's call means — And why it may not behave as expected.
Australia’s Bureau of Meteorology (BoM) has officially stated that La Niña conditions are now present in the Pacific Ocean. Ocean temperatures have cooled enough, pressure patterns have shifted, and key indicators such as the Southern Oscillation Index (SOI) have moved into La Niña territory.
On paper, it meets the definitions. But here’s the important part:
This is a weak and potentially short-lived La Niña, forming in a very unusual climate environment — and it may not deliver the classic “wet Australian summer” people expect.
Below is a clear explanation of why.
1. What BoM is Saying — The Simple Version
BoM and several major climate agencies internationally now agree that:
The tropical Pacific has cooled enough to meet La Niña thresholds
Atmospheric signals (winds, pressure, cloud patterns) support that diagnosis
La Niña will likely persist through summer,
But probably fade back to “neutral” by early 2026
That means La Niña is real — but only just.
It is not a powerful, long-running event like 2010–2012.It is more like a borderline, weak La Niña that might only last a few months.
2. Why This La Niña May Not Behave Like a Normal One
This is the part causing confusion. Traditionally, Australians expect La Niña to mean:
More rainfall over the east
Cooler daytime temperatures
Higher risk of flooding
Wetter cropping seasons
But this year’s conditions are far from normal, and several factors are pushing in different directions.
Here are the big ones:
A. The oceans around Australia are extremely warm
Sea surface temperatures near Australia have been running as much as 1.5–3°C above normal in some regions. Warm local waters tend to create:
More heat
More humidity
More thunderstorms in some areas
But not necessarily widespread rainfall
In short: warm oceans rewrite the usual rulebook.
B. The Indian Ocean Dipole (IOD) is fading fast
A negative IOD (often very wet for southern Australia) was active earlier in spring —but is now weakening and expected to return to neutral.
This means Australia is losing one of its typical “wet” drivers at exactly the moment La Niña is being declared.
C. SAM (the Southern Annular Mode) is wobbling
At times in recent weeks the SAM has been negative, which brings:
More cold fronts into southern Australia
But drier weather into NSW and QLD
A negative SAM can work against La Niña, especially in eastern inland regions.
D. Sub-seasonal and tropical patterns are unstable
The tropical atmosphere (trade winds, cloud zones, the MJO) has been flickering in and out of La-Niña-like patterns.
This inconsistency weakens the La Niña “signal” on Australia.
3. BoM’s Own Rainfall Outlook Doesn’t Look Like Classic La Niña
This is the most telling part.
Despite declaring La Niña, BoM’s official summer rainfall forecast shows:
• No strong wet signal for large parts of eastern Australia
(including some key cropping and inland regions)
• Potentially drier-than-average conditions inland
(particularly in WA and parts of QLD/NSW)
• Hotter-than-average temperatures almost everywhere
That’s not the classic La Niña pattern people expect.
It suggests that although the Pacific meets the technical criteria, Australia may not feel the full “La Niña effect” this time.
4. So What Does This Mean in Practical Terms?
1. Yes — La Niña is underway.
The ocean and atmosphere meet the definitions.
2. But it is weak, short-lived, and forming in a very warm climate backdrop.
**3. Therefore: Do NOT expect a classic wet La Niña summer.**
Instead, expect:
A messy climate pattern
Hotter conditions than usual
Local storms in some regions
Patchy rainfall rather than widespread wet seasons
And no guaranteed drought relief for southern Australia
This matches BoM’s own long-range outlooks.
5. The Bottom Line
BoM has declared La Niña, but this is a borderline, short-term event in a highly unusual ocean environment. The usual Australian La Niña impacts — widespread rain, cooler days, strong east-coast wet seasons — are unlikely to fully materialise. Treat this La Niña as a weak background climate influence, not a guarantee of wet conditions.
That’s the clear message:
La Niña is real —but the results may not look like La Niña.
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