Just when you started packing up your long pants and jackets in preparation for sweltering Australian Christmas and New Years, the Bureau of Meteorology (BOM) has dropped a major bombshell on us. They’ve announced that La Niña is officially underway, which means Australia could be in for a very wet spring and summer this year.
According to the BOM: “La Niña is part of a cycle known as the El Niño-Southern Oscillation (ENSO), a naturally occurring shift in ocean temperatures and weather patterns along the equator in the Pacific Ocean.”
“During La Niña, waters in the central or eastern tropical Pacific become cooler than normal, persistent south-east to north-westerly winds strengthen in the tropical and equatorial Pacific, and clouds shift to the west, closer to Australia.”
What does La Niña mean for weather in Australia?
The BOM states that La Niña typically results in above-average rainfall for Australia – particularly across eastern, central and northern regions.
It will also likely mean cooler days, more tropical cyclones, and an early onset of the first rains of the wet season across the north.
The Bureau has declared that a #LaNiña has developed in the tropical Pacific. Typically during La Niña, there is above average rainfall for eastern, northern and central parts of Australia. pic.twitter.com/4KJeKsVI6A
— Bureau of Meteorology, Australia (@BOM_au) November 23, 2021
BOM’s head of climate operations Dr Andrew Watkins said, of the announcement that:
“La Niña also increases the chance of cooler than average daytime temperatures for large parts of Australia and can increase the number of tropical cyclones that form.
“La Niña is also associated with earlier first rains of the northern wet season, as we’ve observed across much of tropical Australia this year.”
Prior to 2020, the last time Australia experienced a La Niña event was between 2010 and 2012, resulting in one of our wettest two-year periods on record, according to the BOM.
Sadly, this also meant Australians experienced widespread flooding in many parts of the country due to record rainfall. Five of the tropical cyclones that occurred in Australia between 2010 and 2011 were in the severe category, including Tropical Cyclone Yasi, which caused much devastation to far north Queensland.
The last La Niña event occurred in 2020/21, but Watkins stressed that it is not unusual for back-to-back events to occur like this.
The BOM predicts that this year will not see the same intensity as the 2010-2011 La Niña event, “and may even be weaker than in 2020-21 La Niña event”.
“Every La Niña has different impacts, as it is not the only climate driver to affect Australia at any one time. That’s why it is important not to look at it in isolation and use the Bureau’s climate outlooks tools online to get a sense about likely conditions for the months ahead,” Dr Watkins said.
This La Niña event is expected to last until the end of January 2022.
This article was originally published on 30/9/20 and updated to reflect the news of 2021/22 La Niña event.