We often hear statements in the media that extreme weather events are likely to increase in frequency and intensity as the world warms, but how the extreme winds associated with those events will change is hard to say. This doesn’t make it easy for decision-makers considering the risks of these events. However our researchers are working hard to try and provide useful insights to help.
While the term ‘extreme’ is used broadly, an extreme wind event is one involving winds strong enough to cause damage. The Bureau of Meteorology defines this as sustained winds of at least gale force (63 km/h), or wind gusts of 90 km/h or more. These damaging winds are caused by a range of different weather systems that affect Australia, including tropical cyclones, tornadoes, severe thunderstorms, east coast lows, and strong cold fronts. These weather systems are often associated with extreme rainfall.
In northern Australia, the strongest recorded wind gusts are associated with tropical cyclones, and even when tropical cyclones weaken to tropical lows they can bring strong winds causing dangerous conditions. For southern Australia, where tropical cyclones are much less of a risk, extreme winds associated with thunderstorms are a key hazard of concern.
Will extreme wind events become more severe in the future?
Challenges and limitations
Understanding the extent of future changes is a challenging and active area of research. It requires an accurate picture of wind behaviour in the past, as well as highly sophisticated weather and climate modelling to develop projections for the future. The localised and sporadic nature of extreme winds means that many events can go undetected by Australia’s weather station network, leaving a limited and incomplete historical observational record of these events. The severity of extreme winds means that recording instruments can fail or be damaged making it impossible to record the true magnitudes. Current climate models do not yet simulate winds in space and time well enough to accurately represent extreme winds. Limited historical or observed records mean the modelled climate simulations cannot be validated as well as other climate variables, like temperature.
Tropical cyclones
Climate Systems Hub researchers found the total number of tropical cyclones observed in the Australian region has decreased in recent decades. This aligns with previous hub research to some extent, where modelled projections suggest the trend of a decrease in tropical cyclones will continue in the future. Climate models suggest we may experience less tropical cyclones, but they will likely be a higher intensity (e.g. Category 3-5). These severe storms bring increased risk of coastal flooding due to increased peak wind speeds, greater rainfall intensity and higher storm surges. Hub researchers are working to address tropical cyclone intensity projection challenges and provide a better understanding of future intensity changes based on the latest climate models for Australia.
Thunderstorms
Modelling extreme wind gusts is still in its infancy, and given the limitations of historical observations, it is too early to say if extreme winds are likely to become more damaging in the future. This doesn’t make it easy for decision-makers when considering the risks of these events. Researchers at the University of Melbourne and the Climate Systems Hub are developing new approaches to apply climate models to extreme winds caused by thunderstorms. These approaches indicate the large-scale environmental conditions that are conducive to extreme
winds caused by thunderstorms. Results suggest conditions favourable for extreme winds caused by thunderstorms will occur more frequently over some parts of Australia due to global warming, particularly during summer. However, some results indicate a potential decrease in frequency for some regions and seasons, depending on the model used and the method being considered.