Pacific Ocean tracking of El Nino and La Nina

You may recall that last year I pointed out the Bureau of Meteorology (BoM) stopped issuing regular forecasts/watches/alerts specifically for El Niño and La Niña, replacing them with broader long-range outlooks. The announcement about dropping fortnightly El Niño/La Niña watches and alerts came around mid-December 2024.

What’s Changed

The Bureau of Meteorology has updated the way it measures Pacific Ocean temperatures for tracking El Niño and La Niña. Instead of the old method (traditional Niño indices), they’re now using the relative Niño index.

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Why the Change?

In recent years, Bureau forecasts of El Niño and La Niña have often missed the mark.

Measurements show the Pacific Ocean has been warming — but how we measure has also changed a lot over the decades:

Technology has improved dramatically.

The areas covered by observations have expanded.

Data analysis is now far more advanced thanks to computing power.

Research funding has been heavily focused on Climate Change.

Because the old method didn’t fully adjust for these factors, it sometimes made El Niño look more frequent and La Niña less so.

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What the New Method Does

The relative Niño index compares Pacific Ocean temperatures to the broader global tropical average.

This removes the long-term warming effect that shows up in measurements, giving a cleaner signal of whether the Pacific is unusually warm or cool.

It also better matches the rainfall and cloud patterns that drive Australia’s weather.

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What This Means for Australia

The thresholds for declaring El Niño or La Niña remain the same.

Both the new relative Niño values and the old traditional Niño values are still published.

The Bureau’s seasonal outlooks remain the best source for rainfall and temperature forecasts.

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👉 In short:

The Bureau hasn’t always nailed El Niño and La Niña predictions in recent years. By switching to the new relative Niño method — which adjusts for changes in measurements, technology, and the way oceans are analysed — they’re aiming for forecasts that line up better with reality.