Tropical cyclones are hard to predict – that’s one of the things that makes them so dangerous.
Once formed, their movement can be very erratic.
A research team at Griffith University in Brisbane is trying to discern the behaviour of cyclones better, by examining five decades of historic cyclone tracks around Queensland.
But these records aren’t perfect for analysing and predicting cyclones in more detail.
“There are constraints in terms of the evolving satellite technology and wind speed measurement that makes using historical track data a problem,” says John Miller, a PhD candidate at Griffith and lead author on a paper describing the research, published in Natural Hazards.
Instead, the researchers calculated cyclone power, track curvature (the wiggliness of the track) and location using an algorithm to reduce the effect of faulty records.
With this analysis, the researchers could divide the cyclones into three different “clusters”.
Cluster 1 cyclones started in the southeasterly part of the Coral Sea and headed southeast, occasionally hitting land in southeast Queensland.
Cluster 2 cyclones generally formed closer to the coast in the Coral Sea and moved east to west, sometimes making landfall in Queensland.
Cluster 3 cyclones started partly in the Coral Sea, but mostly west over the Gulf of Carpentaria, with cyclones usually moving west-southwest and hitting land. These cyclones could travel long distances over land.
“A previous study into why that could have been happening suggested that they regained energy from the moisture in the soil, over northwest of Australia, and then they had that energy then to propagate long distances,” says Miller.
While cyclones are probably becoming less frequent as the climate warms, they may also be getting more intense when they do form – and coming into contact with more people.
“There’s still a little bit of uncertainty around tropical cyclone trends, although it seems that some recent studies have indicated decreasing frequencies of tropical cyclones both in Australia and globally,” says Miller.
In this analysis, while cyclone frequency decreased overall, Cluster 1 cyclones are the only group with a marked drop.
But, points out Miller, these cyclones are also the most likely to go close to the highly populated southeast Queensland.
Next, the researchers are aiming to see what’s driving cyclone behaviour – including climatic changes. After that, they’ll be investigating how the cyclones change waves and swell.