Key points
- Australia’s cyclone season runs from November to April, with around 11 cyclones forming each year.
- Fewer cyclones are forming in Australian waters, but rising ocean temperatures fuel extreme weather.
- Future cyclones may be fewer but stronger, bringing intense rainfall and dangerous storm surges.
In Australia, tropical cyclones are an ongoing threat during our cyclone season, which generally lasts from November to April. On average, the Australian region experiences 11 cyclones a year, although typically only four to five of these cyclones will reach land.
This season there has been 6 tropical cyclones so far with all eyes currently on Cyclone Alfred. Tropical Cyclone Alfred is currently a category two storm, several hundred kilometres off the south-east Queensland coast. According to the Bureau of Meteorology, Alfred is forecast to cross the southeast Queensland coast late on Thursday or early Friday morning. Alfred is expected to cross the coast near Brisbane, although its exact movements remain uncertain. The current cyclone watch area extends from Sandy Cape in Queensland to Grafton in New South Wales.
Prior to Alfred, Tropical Cyclone Zelia, a small but very intense cyclone, crossed the coast at category 4 strength near the De Grey River mouth northeast of Port Hedland, Western Australia on 14 February. Rainfall and flooding caused significant impacts to remote communities in WA's Pilbara region. Severe Tropical Cyclone Zelia was the fifth tropical cyclone in the Australian region for the 2024/25 season, and the first to make landfall.
We’ve got some answers to a few questions you may have about cyclones.
1. What causes tropical cyclones?
Several conditions must be met for a cyclone to form, including thunderstorms over a warm body of water and little change in atmospheric wind speed with height.
Warm and humid air from a warm ocean (typically, at least 26.5 °C in the current climate) rises, resulting in a low-pressure system. Air rushes in to fill the gap but due to the spin of the Earth, it starts spiralling around the low pressure and flows upwards near the centre. Due to the dependence on the Earth’s spin, tropical cyclones typically do not occur within about 5 degrees of the equator.
2. Can tropical cyclones be predicted?
The ability to predict tropical cyclones has radically improved due to developments of global weather models. In Australia, the Australian Community Climate and Earth-Simulator (ACCESS) model is used alongside global models to predict cyclone tracks and intensity.
In the last decade, the accuracy of tropical cyclone forecasts has improved measurably – most notably cyclone track forecasts, which allow for better planning of emergency events and decision making. However, forecasting tropical cyclone intensity, including rapid intensification, is an ongoing challenge and remains an active area of research.
ACCESS was used to predict the path of Tropical Cyclone Yasi, which crossed the coast of North Queensland in 2011. This allowed the community, industry and emergency management agencies to make decisions and plan seven days ahead of the event.
3. Has the frequency of tropical cyclones changed?
Research has shown a statistically-significant downward trend in the annual number of tropical cyclones in the Australian region over the period extending from 1981/82 to 2017/18, during the period of satellite images. The reasons for this downward trend are still being determined but are likely to be due to a combination of both natural variability and longer-term climate change. Additional non-satellite observations suggest there has also been a longer-term reduction in the number of tropical cyclones since 1900.
The Bureau of Meteorology’s satellite record is relatively short and there have been changes in the historical methods of analysis. Combined with the high variability in tropical cyclone numbers and influences of natural variability such as the El Niño-Southern Oscillation, it makes it difficult to attribute trends to any single factor.
However, it is clear that sea surface temperatures off the northern Australian coast have increased – part of a significant warming of the oceans that has been observed in the past 50 years due to increases in greenhouse gases. Warmer oceans tend to increase the amount of moisture that gets transported from the ocean to the atmosphere, and a warmer atmosphere can hold more moisture and so there is a greater potential for intense rainfall events with tropical cyclones.
4. Will the frequency of tropical cyclones change in future?
The underlying warming trend of oceans around the world, which is linked to human-induced climate change, will increase the risk of extreme rainfall events in the short to medium term. Studies in the Australian region point to a potential long-term decrease in the number of tropical cyclones each year in future, on average.
On the other hand, there is a projected increase in their peak intensity, on average. We also expect to see an increase in the proportion of tropical cyclones that reach the more intense categories (category 4 or 5). However, there is large uncertainty in these projections due to challenges associated with modelling tropical cyclone physics in coarse-resolution climate models.
5. What are the impacts of tropical cyclones?
The most severe impacts of tropical cyclones are not just due to strong winds, which slow down once they reach the land, but are also due to heavy rains, damaging waves, and storm surges.
Today, coastal flooding is often caused by storm surges, which occur when strong onshore winds from cyclones combine with their low pressure to elevate sea levels and drive water on to land. Storm surges can be particularly dangerous when they coincide with high or king tides.
Cyclone Yasi in February 2011 was one of the most destructive cyclones to hit Australia. Classified as a Category 5 cyclone, Yasi caused $1.4 billion worth of damage, according to the Insurance Council. Yasi destroyed infrastructure, flattened crops and caused extensive damage to corals on the Great Barrier Reef, but luckily no lives were lost.
6. How will the impacts of tropical cyclones change in future?
With rising sea levels and a projected increase in cyclone intensity, there is likely to be an increased risk of coastal flooding, especially in low-lying areas exposed to cyclones and storm surges. For example, the area of Cairns’ risk of flooding, by a 1-in-100-year storm surge, is likely to more than double by the middle of this century. Extreme rainfall from tropical cyclones is also likely to increase. A potential expansion of tropical cyclone activity toward higher latitudes remains an active area of research, but projections are currently highly uncertain.
7. How can we adapt to expected changes?
In the longer term, better planning and design can help protect homes and infrastructure. This could include making sure new constructions have floor heights above sea level and lower floors are made with flood tolerant materials. Planning codes also need to prevent new development in flood prone areas.
Governments are now taking account of changes in climate and sea level through their planning policies. Just as the building codes and rules for Darwin changed in the wake of Cyclone Tracy, so they should now be re-assessed for each region and locality in Australia to take account of climate change.
More information about cyclone Alfred, forecast and advice is available at the BOM.
This article was originally published in March 2019 on CSIROscope and was updated on March 4, 2025.