Why there is a huge weather change coming this summer

Here comes the rain again.

That’s the song Australia’s Bureau of Meteorology was singing Tuesday as it declared that La Niña has developed in the Pacific Ocean.

The move officially upgrades La Niña to an active event, meaning recent changes in ocean temperatures and weather patterns over the Pacific are now likely to remain until at least the end of the year.

What is La Niña?

Both La Niña and its counterpart El Niño are known as climate phenomena. The oceans switch between these states roughly every two to seven years, depending on the wind and ocean conditions across the Pacific Ocean between Australia and South America.

“What this means is that we’ve got warmer ocean water near Australia and cooler water off South Australia and that tends to favour rainfall and cloudiness near Australia,” BOM Manager of Climate Operations Dr Andrew Watkins explained.

As a result, we can expect “more rain and cooler temperatures over the coming months,” he said.

According to the Bureau, La Niña typically results in above-average spring rainfall for Australia, particularly across eastern, central and northern regions. It can also mean cooler days, more tropical cyclones, and an earlier onset of the first rains of the wet season across the northern part of the country.

A ‘dynamic’ and possible wet Christmas period

The last La Niña event occurred from 2010-2012 and resulted in one of Australia’s wettest two-year periods on record, leading to widespread flooding in many parts of Australia following record rainfalls.

The BOM says its models do not currently anticipate this event will be as strong as the La Niña of 2010–12, which was one of the four strongest La Niñas events on record.

Nonetheless, Weatherzone meteorologist Ben Domensino said the weather pattern persisting into next year means the country is in for a dynamic Christmas and New Year’s period.

“Models suggest that it will persist into the start of 2021, meaning Australia is in for a dynamic end to the year, with an increased likelihood of rain, floods and tropical cyclones,” he wrote on Twitter.

Could more cyclones be on the way?

The north of the country might seen an increase of extreme weather events, according to climatologists.

“Typically with La Niña, we do see more tropical cyclones than normal,” Dr Watkins said. “Typically we see around nine to 11 tropical cyclones in any given season, this [La Niña] usually would push up the number.

“It’s always important to prepare early, but this year could be a little higher risk.”

For those in areas prone to flooding, Dr Watkins also urged the public to keep abreast of any warnings during times of heavy rainfall in the coming months.

What impact will La Niña have on the bushfire season?

While it’s impossible to avoid summer bushfires, particularly with the impact of global warming, Dr Watkins said the conditions brought on by the weather system should help in reducing the summer’s fire risk.

“We can’t avoid some fires in any summer now, La Niña though with a bit of extra rainfall will hopefully keep those fires a little smaller and a little shorter than what we’ve seen in recent years,” he said.

“So it reduces the bushfire potential a little but doesn’t extinguish it completely.”

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