A wide view of a sandy Australian beach from low coastal dunes, with waves rolling onto the shoreline beneath towering storm clouds. Dark rain shafts hang over the ocean to the left, while patches of blue sky and bright white cloud remain overhead. Vegetation and rocky outcrops line the dunes in the foreground, and the coastline curves away into the distance.

Briefing Note: Weather Systems

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Weather Systems: The ultimate cause of weather

Have you checked the weather forecast today yet? Wherever you live, and whatever your work and lifestyle may be, the weather defines so many things about your life. From the clothes you wear to the water you drink, the food you can buy, the cost of electricity, the choice between wearing sunscreen or taking an umbrella, and the materials and design for building a house.

Future climate risk is the risk of future weather

Weather systems shape our everyday lives by forming the weather we experience, from the weather resources we depend on to disruptive high-impact weather. This influence will only increase as our economy becomes more weather-dependent and the distribution and reliability of water, wind, and solar resources change.

Climate is weather accumulated over time, and all weather stems from weather systems. Their combined impact over weeks can shape an entire season, which is why we feel climate change through changes in weather systems.

Humans can only influence the weather in limited ways, such as through local land-use changes. We cannot control weather systems or dictate their effects. To adapt to climate change, we must learn how weather systems function, how they might change, and what impacts they will have on the Earth’s surface.

What is 21st Century Weather doing?

21st Century Weather is deepening our understanding of weather systems, their behaviour, impacts and how they will change. We are developing higher-resolution models to capture the fine-scale details that can impact weather systems and the weather conditions they produce.

Understanding the dynamics of weather systems reveals how systems across different scales interact to produce high-impact weather, such as bushfires, heatwaves and storms, or weather resources such as wind power.

With our industry partners, we are examining how changes in weather systems will shape an increasingly weather-reliant energy system. Key questions include: how reliable will wind and solar resources be, which regions face the greatest disruption risk, and whether renewable energy supply will match demand peaks. The answers underpin every aspect of infrastructure planning, from where to locate generation assets, how to diversify energy sources and design storage solutions. This is the core mission of 21st Century Weather.

We are also testing whether climate models can accurately simulate the weather systems that matter most, including those driving bushfires. That requires knowing how well we can observe weather systems using global observational networks, from satellites and ships to weather balloons, and how faithfully models represent them.

What is a ‘weather system’?

Weather systems are organised atmospheric structures that last days to weeks. They are the familiar highs and lows on weather maps. Weather systems can change winds, produce thunderstorms, lightning, hail and bring rain. We experience them on the ground through changes in temperature, humidity and other weather elements.

Weather systems vary enormously in shape and size. Tropical cyclones span hundreds or even thousands of kilometres, while thunderstorms can be just a few kilometres wide. Though they shape the weather near the surface, much of what drives them happens high up in the atmosphere. Powerful bands of wind, called jet streams, often determine where weather systems form and travel. These air currents meander and undulate, like waves at the beach, stirring the warmer air near the equator with the cooler polar air. Each weather system has recognisable characteristics, yet no two are exactly alike.

Himawari satellite image overlaid with mean sea level pressure (left). Example of weather systems identified with objective algorithms and their associated precipitation (right). Coloured outlines denote weather objects; shading denotes precipitation. High precipitation coincides with a bomb cyclone over the Great Australian Bight, as shown by the overlap of the cyclone object and a front embedded in a moist rising airstream, also known as a warm conveyor belt.

One way of identifying weather systems is “synoptic weather typing”. Objective algorithms classify each day into a distinct type, which can then be linked to the surface weather, resources or high-impact weather it produces. By reducing the full complexity of weather systems to a single daily type, this method provides a powerful yet practical link between regional weather and larger-scale climate.

The weather types defined by Barnes et al. (2025) classify weather systems to help us trace the drivers of high-impact weather and weather resources. Capturing these processes across the Australian continent can improve our decision-making.

Weather systems are changing, but how will they change in a warming world?

Small changes in a weather system can dramatically alter conditions near the Earth’s surface, and the surface weather is what we experience and depend on every day.

The inner workings of weather systems are complex, making it hard to pin down exactly how they will change in a warming world. Yet those details matter as they translate directly into weather. How weather systems will shift in frequency and structure is among the most pressing research questions of our time. Answering this question is essential to estimate future access to weather resources, understand our risk from high-impact weather, and support societal decision-making.

What we do know is that a warmer atmosphere can hold more water vapour, providing extra fuel for weather systems. This is likely to intensify the rainfall that weather systems bring, and some weather systems, such as the strongest tropical cyclones, may produce stronger winds. We also expect the jet streams to shift poleward, dragging weather systems with them. The net effect on surface weather remains only partially understood, as changes in location and intensity can amplify or dampen each other depending on the region.

Every extreme event is a weather event

In January 2026, Melbourne hit 44.4°C. The heatwave was followed by devastating bushfires in Victoria and a state of disaster. Climate change made the intense heatwave five times more likely, but weather systems caused it.

Upper-level high-pressure systems forced air downwards to the surface. As air parcels descended and their pressure increased, the air compressed and heated up, much like an air pump when inflating a tyre.

Australia’s exposure to climate risk is growing fast. Insurance losses from weather and climate have more than tripled since the late 1990s, now costing around 0.7% of GDP every five years, totalling billions of dollars. As climate change drives larger shifts in weather systems, the gap between events narrows, leaving less time to recover. Every decision made today about energy, water, food, the environment and regional security is, at its core, a climate decision.

Many extreme weather events, such as heatwaves and heavy rain, are expected to intensify. The key question is by how much, and the answer lies in the underlying weather systems. Dynamical changes in weather systems represent one of the greatest challenges in climate prediction.

Current knowledge gaps

Weather systems are deeply interconnected, so it is hard to isolate their individual characteristics and impacts. The atmosphere is chaotic; small fluctuations can grow rapidly, making predictions tricky.

The Melbourne heatwave illustrates this complexity. Besides the upper-level highs, masses of moist air from Western Australia and a tropical cyclone off the northwest coast also played a role in intensifying the heatwave. Shift any one ingredient slightly, and the heatwave’s intensity or duration could have been very different.

A hotter climate means more frequent, more intense and longer heatwaves, as well as more very hot days. Nevertheless, key processes, such as how distant thunderstorms and tropical cyclones can remotely amplify heatwaves, are less well understood and consequently are represented inadequately in climate models.

Technical barriers

Weather system research is data-hungry. High-resolution climate models, down to kilometre scales, are needed to resolve key features of weather systems. They must be analysed at minute-to-hourly intervals while also running long enough to capture weather-climate interactions. This huge computational demand is currently severely constrained by Australia’s ageing computing infrastructure.

Sparse atmospheric observations limit our ability to directly measure key features of weather systems. To fill these gaps, researchers combine models and observations into “reanalyses”, which are a consistent but imperfect snapshot of the Earth at a given moment. They are our best estimate of the truth, but they are estimates nonetheless.

Producing reanalyses demands enormous data and computing power, which is why expanding global observing systems and investing in improving climate models remain urgent priorities.

What are the weather systems that matter the most to you?

If you have questions about weather systems and how they interact with your life or work, reach out via hello@21centuryweather.org.au. You can download a PDF copy of briefing note here.

Wild surf and dark storm clouds over Surfers Paradise as Tropical Cyclone Alfred approaches the Gold Coast in 2025. (Photo: Shirley Jayne Photography)