Severe Tropical Cyclone Narelle was forecast to be one of the most destructive storms to hit the north Queensland coast in recent memory.
With the storm hitting the coast on Friday morning, climate experts say global heating has likely helped fuel the system.
How might global heating have affected Narelle?
The storm system started its life as a tropical low that formed south of Solomon Islands in the Coral Sea.
But it underwent rapid intensification in the days that followed, developing into a cyclone earlier this week.
In order to form, cyclones need ocean temperatures to be above 26.5C, as well as favourable atmospheric conditions.
Sign up for the Breaking News Australia emailBut climate scientist Andrew Watkins, an adjunct professor at Monash University and a councillor with the Climate Council, says Narelle has been moving over an area of ocean that has seen record high temperatures in recent months.
“The Coral Sea has just recorded its hottest December, hottest February, hottest summer, hottest calendar year and even the hottest financial year,” Watkins says.
He says warmer ocean temperatures are fuel for tropical cyclones like Narelle, and temperatures along its track have been between 1C and 2C warmer than average.
“The Coral Sea is almost half a degree warmer than it was 30 or 40 years ago,” he says.
Australia’s 2024 State of the Climate report notes the Coral Sea was one of the ocean areas that experienced the most warming in recent decades.
How do higher ocean temperatures affect a cyclone?
Ocean temperatures dictate whether a cyclone will form. But they also help the process of convection – where air rises rapidly, often causing storms.
Andrew Dowdy, an associate professor in climate science at the University of Melbourne and an expert on weather extremes, says “these extremely warm sea surface temperatures also help add moisture and heat to the air, making more favourable conditions for convection”.
Dowdy has also been looking at Narelle’s formation and progress using publicly available satellite images that are able to show lightning strikes.
“I saw a strong band of lightning in the eye wall, which shows the intense convection fuelling TC Narelle over these exceptionally warm waters.”
How else might global heating affect Narelle?
Narelle made landfall on Friday morning, at around the time of a high tide.
Watkins says because global heating was pushing up sea levels, this could worsen factors such as inundation, erosion and storm surges.
“It’s not just about the wind and rain,” he says. “When you have a storm surge the winds from a tropical cyclone pools water up against the coast. That coastal inundation and erosion becomes worse each time because the sea level is now higher.”
Global heating also means the rainfall expected from a cyclone is likely to be higher, because a warmer atmosphere can hold more water that can fall as rain.
“A tropical cyclone sucks in moisture from a broad area and even when it is over land it has got that extra moisture available to rain out,” Watkins says.
Is climate change affecting how many cyclones form in Australian waters?
Since the early 1980s, there has actually been a drop in the number of cyclones forming in the Australian region – something climate scientists have predicted.
“The balance of evidence from observations, modelling and understanding of physical processes tells us that severe TCs like this are likely to become more frequent due to climate change,” Dowdy says.
“The weaker TCs, like category one and two systems, might become less frequent, but our buildings are designed to withstand winds from those.”
How does Narelle compare with other recent storms?
There had been uncertainty about whether Narelle would cross the coast as either a category four or category five storm. In the end, it was only 5 km/h short of being a category five system at landfall.
The Queensland premier, David Crisafulli, this week said: “Not since the late 1800s in the far north of this state has a category five system crossed. Category five systems don’t cross the coast that frequently.”
That storm was Tropical Cyclone Mahina, which hit Cape York in March 1899. At least 307 people who were members of a fleet of pearling ships died during the storm surge.
Crisafulli said Narelle would be the biggest system “in living memory” for people living in the region where it was predicted to strike.
The most recent category five storm to cross the Australian coastline was Western Australia’s Ilsa in April 2023, which struck north of Port Hedland with a record wind gust of 289km/h.
The last time Queensland had a category five storm cross the coast was Marcia in 2015, which struck in a relatively uninhabited area north of Yeppoon.
Severe Tropical Cyclone Yasi – one of the state’s most powerful storms on record – struck as a category five storm in 2011, crossing between Innisfail and Cardwell.
