Heavy rain and strong winds in cyclone Zelia strengthened by human-driven climate-change

Contact Authors

• Davide Faranda, IPSL-CNRS, France  📨davide.faranda@lsce.ipsl.fr   🗣️French, Italian, English

• Tommaso Alberti, INGV, Italy  📨tommaso.alberti@ingv.it   🗣️Italian, English

Citation

• Faranda, D., & Alberti, T. (2025). Heavy rain and strong winds in cyclone Zelia strengthened by human-driven climate-change. ClimaMeter, Institut Pierre Simon Laplace, CNRS. https://doi.org/10.5281/zenodo.14871178

Press Summary (First Published 2025/02/14)

• Cyclones similar to Zelia  are up -1 hPa deeper, up to 27 mm/day (up to 20%) wetter and up to 5 km/h (up to 10%) windier in the present compared to the past. They lead to colder (up to -2°C) conditions over the Australian Coasts.

• This event was associated with very exceptional meteorological conditions 

• We ascribe the strengthened wind and heavier precipitation in cyclone Zelia to human driven climate change and natural climate variability likely played a minor role.

Event Description

Tropical Cyclone Zelia, a Category 5 storm, made landfall on Western Australia's Pilbara coast near Port Hedland on February 14, 2025, bringing destructive winds up to 320 km/h and heavy rainfall. The cyclone caused significant damage, including flash flooding and infrastructure destruction. Authorities issued emergency warnings, closed schools, ports, and roads, and set up evacuation centers to assist affected residents.  In addition to the immediate impacts, Cyclone Zelia disrupted operations in the Pilbara region's mining sector. Major iron ore producers, such as BHP, Rio Tinto, and Fortescue, paused port operations at Port Hedland, Dampier, and Cape Lambert to ensure worker safety. The cyclone's rapid intensification and severe impacts highlight the increasing severity of tropical cyclones in the region, potentially linked to climate change. 

The Surface Pressure Anomalies show a large  negative anomaly, up to -20 hPa over the north coast of Australia with Temperature Anomalies displaying  up to -7°C negative values over the area affected by the cyclone. Precipitation data show extremely high daily amounts of precipitation over the Queensland coast exceeding 400 mm/day over the cyclone area. Wind speed Data indicates strong winds (up to 120 km/h daily) directed from the Ocean towards the coast. These winds enhanced precipitation over the mountain areas of Queensland contributing to the flooding. We remind you that our analysis is based on ERA5 data. This product does integrate some station observations, especially for rain data. The values reported here can be different from those observed at single weather stations.

Climate and Data Background for the Analysis

The Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6) highlights significant concerns regarding climate change and its impact on flooding in Australia. The report indicates that climate change is expected to increase the frequency and severity of heavy rainfall events, leading to more frequent and intense river floods across the country. Since 1982, there has been a decrease in the number of tropical cyclones occurring in the Australian region. However, the proportion of severe cyclones has increased, indicating that while fewer cyclones are forming, those that do are more intense. Projections suggest a continued decrease in the number of tropical cyclones in the Australian region. At the same time, there is an expected increase in the proportion of severe cyclones, with a greater percentage anticipated to reach higher categories. Additionally, an increase in heavy rainfall intensity is projected, leading to more severe flooding events.

Our analysis approach rests on looking for weather situations similar to those of the event of interest having been observed in the past. For this event, we have low confidence in the robustness of our approach given the available climate data, as the event is very exceptional in the data record.

ClimaMeter Analysis 

We analyze here (see Methodology for more details) how events similar meteorological conditions have changed in the present (1987–2023) compared to what they would have looked like if they had occurred in the past (1950–1986) [113°E 123°E 25°S 15°S]. 

The Surface Pressure Changes show that cyclones are up to 1 hPa deeper in the present climate than what they would have been in the past on the Northern coast of Australia. Temperature Changes show that similar events produce temperatures in the present climate that are between 1 ºC and 2 ºC colder than what they would have been in the past, over the Australian coast. The Precipitation Changes show up to 27 mm/day (up to 20%) wetter conditions over the Coastal Areas and the mountains of Queensland. Windspeed Changes indicate windier conditions up to 5 km/h (up to 10%) offshore Australia. We also note that Similar Past Events occur with similar seasonality in the past and present periods. Changes in Urban Areas reveal that Broome and Roebourne experience heavier rain in the present than in the past. Broome also experiences a significant increase in wind (up to 3 km/h). The city of Port Hedland does not experience significant changes.

Finally, we cannot detect the influence of natural climate variability on the event. This means that the changes we see in the event compared to the past may be primarily due to human driven climate change.

Conclusion

Based on the above, we conclude that cyclones similar to Zelia  are up –1 hPa deeper, up to 27 mm/day (up to 20%) wetter and up to 5 km/h (up to 10%) windier in the present compared to the past. They lead to colder (up to –2°C) conditions over the Australian Coasts. We interpret Cyclone Zelia as an event driven by very exceptional meteorological conditions whose characteristics can be ascribed to human driven climate change.