What Exactly Is the La Niña Weather System and Why Is It Here to Ruin Our Summer Again?


The Bureau of Meteorology is expected to declare that a La Niña weather pattern is confirmed for Australia which could last until at least early next year.

It doesn’t come as too much of a shock, however, as much of Australia has already begun to feel the effects of La Niña. Large parts of the Murray-Darling basin in the Southern Tablelands of NSW have experienced severe flooding in the past few weeks and more rain is on the way. Meanwhile, storms continue to lash Australia’s east coast from Mackay in Queensland and below. Cyclone Paddy also formed near Christmas Island, to the north-east of Australia, but is expected to weaken without making landfall. 

Patterns of weather like this are set to continue throughout the summer as La Niña takes effect across the Southern Hemisphere. Storms, flooding, and heavy rainfall are all predicted for the next few months which could put a dampener on holiday plans and, more importantly, threaten those living in coastal areas.

Having said that, La Niña also brings positives to this wide, sunburnt land. Increased rainfall is something we desperately need in a country that has been in perpetual drought for years. Of course, there can always been too much of a good thing.

It’s hardly surprising that we’re seeing another La Niña system this year, as we experienced much the same last year. Normally these weather patterns last for just a few months, but its not uncommon for them to hang around for several years. Here’s everything you need to know about this meteorological phenomena.

What Is La Nina?

La Niña — or ‘The Little Girl’, in Spanish — is the cold weather counterpart to the warmer weather system El Niño or ‘The Little Boy’. El Niño is named in reference to the baby Jesus, since the changing weather conditions caused by the weather normally take effect around Christmas time.

These two patterns of warming and cooling weather across the Southern Hemisphere makeup what is known as the El Niño Southern Oscillation. This oscillation affects the Pacific Ocean and the countries that border it and is responsible for hurricanes in the Caribbean and cyclones in Australia.

It’s caused by cool water flowing up from Antarctica along the South American coastline where water is around 10°C colder than the Eastern Pacific. In normal years, this water flows deep under the surface of the ocean without causing any major abnormalities. During La Niña events, strong winds push ocean water East, drawing more cold water from Antarctica and cooling the Pacific water temperature, resulting in more cloud cover as the cold water is heated and evaporates. In El Niño events, the cold water cycle is affected and the water in the Pacific Ocean becomes hotter, resulting in less cloud coverage and less rainfall as a result.

The cycles happen irregularly and can last anywhere from five months to several years. The previous La Niña event stretched from 2010 to 2012 and resulted in one of Australia’s wettest two-year periods.

How Will It Affect Australia?

This time, the La Niña event has been less extreme than what we’ve seen in previous years. The Bureau of Meteorology reported last year that, despite the cooling effects of La Niña, spring 2019 was our hottest ever on record and that 2020 was in the top five hottest years on record. This year, temperatures have been above average in northern Australia but cooler than average in the southwest. Rain has not been consistent either, with below-average rainfall in the interior and well above average rainfall along coastal regions.

As we enter our second La Niña year, we can expect similar patterns to last time. This means more cyclones, more flooding, and wild weather proceeding throughout the summer. It will also affect the tides, which have been higher in recent years due to overall global sea-level rise, making them stronger and bigger overall.

People living in coastal regions have already noticed higher ocean levels and this data from the Sydney coastline shows that we’ve already begun experiencing these higher than expected tidal levels.

Is La Niña a Good Thing?

In one sense, yes. The La Niña event will continue to bring extended rainfall and cooler weather to our environment which badly needs a break after long drought seasons and the Black Summer fires. More rainfall will give nature a chance to replenish water in native plant species that will help to protect against fires as they emerge this summer.

But obviously, the wild weather brings with it destruction and coastal erosion which is bad news for those living on the coast. A good 85% of us live within 50KMs of the sea but it will be those right on the water who are going to face the brunt of the coming storms.

La Niña and El Niño are rare weather conditions that scientists are uncertain about how they will be impacted by climate change. It’s fair to say though that more extreme and unpredictable weather will be par for the course as climate change continues to gather speed.

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