Australia faces a hot autumn with Sydney sea temperatures warm enough for a tropical cyclone | Australia weather

Much of Australia is facing a hotter than usual autumn with sea temperatures in Sydney now so warm they could support the formation of tropical cyclones.

Sea temperatures are required to be above 26.5C for tropical cyclones to form. Temperatures recorded in Sydney by Manly Hydraulics Laboratory have surpassed this temperature, twice recording temperatures of 26.75C in the last week.

This temperature is approximately 3C above average for March, and the highest recorded in Sydney since 1992, making the temperature of the Tasman Sea akin to Queensland’s tropical waters. The previous record was 26.6C in February 2022.

Moninya Roughan, a professor of oceanography at the University of New South Wales, said rising temperatures were largely due to climate change. She said the La Niña climate pattern experienced over the last few years lowered temperatures, but now that El Niño was in effect, it was as if “we’ve turned off the air conditioner and all of a sudden we’re seeing the consequences of the ocean continuing to absorb heat”.

She said this year’s median ocean temperatures were “off the charts”.

“I shudder to think about what might happen if sea temperatures continue to rise,” Roughan said.

“What we’re seeing right now is an extreme ocean warming event … ocean organisms die, habitats die … they get stressed and may not recover.”

However, because the other atmospheric conditions necessary for the formation of cyclones – including wind speeds above 63km/h and a warm cored, non-frontal low pressure system – were not present, the risk of a cyclone was unlikely.

The BoM senior climatologist Hugh McDowell said Australia was unlikely to get tropical cyclones that far south, given that the temperatures recorded were not in an area large enough to generate a cyclone.

“With climate change, we’re seeing things we don’t expect,” he said. “We’re seeing unprecedented weather all the time and we’re expected to see more extremes with climate change in the future.”

According to the BoM, tropical cyclones normally occur in northern Australia between November and April. Australia averages 11 tropical cyclones a year, however, typically only four of these reach land.

McDowell said the tide of hot weather was caused by climate change.

He said that while data from the first few weeks of autumn was still preliminary, Australia would probably exceed median maximum temperatures “pretty much everywhere”, signalling that the rest of autumn would present unusually warm temperatures.

“It’s hard to say whether we’ll see a record breaking autumn or not, but the summer that’s just passed was the third warmest on record.”

McDowell said that while Australians were set for a warm autumn, “it’s not something we haven’t seen before” – 2022 saw March record its fourth highest temperature, with its second highest temperature recorded in 2019.

He said winter was shaping up to be warmer than average, with temperatures likely to exceed expected median minimum and maximum temperatures.

A cold front was expected on Friday, but summer temperatures were expected to linger for another few weeks before cooling.

Victoria, South Australia and Tasmania were just emerging from a severe heatwave, with temperatures in some areas soaring into the high 30s and early 40s over the past few days.

In Sydney, the average maximum temperature for March was 28.3C, driven by an autumn record of seven consecutive maximum temperatures above 28C. This average maximum temperature was 3.5C above the long-term average, and above the 2023 March record of 27.6C.

Weather provider Weatherzone reported that there was a high chance of a small tropical cyclone (category 1) occurring off the coast of Western Australia this weekend, with high winds, heavy rains and rough seas expected to be felt in Pilbara.