Heatwaves and hotter days

The Bureau of Meteorology (BoM) has warned of warmer and drier conditions over spring and summer for parts of Australia following a declaration that El Niño and a positive Indian Ocean Dipole (IOD) are underway.

In its long-range forecast, from October to December, the BoM is predicting maximum temperatures to be at least three times as likely to be unusually warm for most of the country, with the two climate drivers acting as contributing factors.

In Broken Hill, during the last El Niño and positive IOD event, October temperatures averaged 30.9 degrees – the hottest October on period since the dataset for Broken Hill Airport began –, rising to an average of 34.2 degrees throughout December and an average of 34.6 degrees within February. Of the 151 days between October 1, 2015, and February 28, 2016, 104 days were above 30 degrees, 53 were above 35 degrees, and 14 were above 40 degrees.

El Niño events increase the risk of extreme temperature shifts like heatwaves and hotter days and is part of a natural climate cycle that affects global weather and occurs on average every three to five years, the BoM made the El Niño declaration after three of the four El Niño criteria were met, including a sustained response in the atmospheric circulation above the tropic Pacific.

When a positive IOD and El Niño occur together, they tend to draw rain away, and their drying effect is typically stronger and more widespread across Australia. This year marks the seventh time since 1960 that El Niño and a positive IOD have happened at the same time, and the first time since 2015.

“Over spring, their combined impact can increase the chance of below average rainfall over much of the continent and higher temperatures across the southern two-thirds of the country. The Bureau’s three-month forecast for Australian rainfall and temperatures have been indicating warm and dry conditions for some time,” Bureau of Meteorology Climate Manager, Dr Karl Braganza said.

“An established El Niño and positive IOD reinforces our confidence in those predictions. Based on history, it is now also more likely that warm and dry conditions will persist over eastern Australia until autumn. Around two-thirds of Australia’s driest years on record were during El Niño however, no two El Niño or IOD events or their impacts are the same.”

Bureau Senior Climatologist, Catherine Ganter, added that “similar to El Niño, the IOD describes a natural climate cycle brought about by sustained changes in the difference between sea surface temperatures in the tropical western and eastern Indian Ocean”.

It’s nothing new to suggest it gets hot in the Silver City over summer. Average summer temperatures since 2012-13 have hovered between 31.37 (2020-21) and 35.47 (2018-19). By including October and November into the calculations, it remains upwards of 31 degrees. Both the hottest average temperatures recorded in the dataset from January (38.3) and December (35.4) were both in 2019.

But now, heading into the last few months of 2023, there’s the added threat of El Niño and positive IOD event that will take us into a scorching summer period. And while the BoM says their impacts aren’t the same, it’s certainly had its effect on the city the last time the two events occurred.

Given these predictions, it is advisable to follow the recommendations from the Cancer Council to ‘slip, slop, slap, seek, and slide’ in preparations for the heatwave that’s about the descend upon the town.

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