‘Unusually large’ multi-state storm causing severe weather for Australia’s east – with more on the way

A severe thunderstorm is a powerful storm capable of producing dangerous weather. In this event, the Bureau of Meteorology warned about hail, damaging winds, flash flooding and power outages. These hazards can affect communities quickly, leaving little time to prepare or travel safely.

The system was unusually large because it crossed several regions and states at once. A broad line of storms had already moved through western New South Wales. Another line extended from the Snowy Mountains to the Queensland border, while further storms were being watched behind it.

This was described as a “multi-state system of storms” by bureau meteorologist David Crock. Severe weather was possible across southern Queensland, western NSW, the ACT and eastern Victoria on Sunday. Storm activity was expected to continue into Monday, especially in northern NSW and southern Queensland, as the cold front moved east.

The affected area was exceptionally broad, covering parts of several states and one territory. Severe thunderstorms were likely across southern Queensland, western New South Wales, the Australian Capital Territory and eastern Victoria. This meant the system threatened both inland and coastal communities rather than one small location.

The Bureau of Meteorology issued a warning for Sydney, greater Wollongong and parts of the Blue Mountains, Hawkesbury, Gosford, Wyong, Wollondilly and Wingecarribee. Wind gusts of up to 100km/h were recorded in central-western NSW around midday Sunday. A broad storm line had already crossed western NSW.

The risk was expected to continue beyond Sunday. Northern NSW and southern Queensland faced further storm activity into Monday as the cold front pushed east. Other regions, including Tasmania and Western Australia, were forecast to see showers or cooler conditions rather than the main severe-storm threat.

Severe thunderstorms matter because they can produce several damaging hazards in a short time. Hail can harm property and crops. Strong winds can damage buildings, trees and infrastructure. Flash flooding can rise quickly, while power outages can disrupt homes, businesses and emergency services.

The article recorded wind gusts of up to 100km/h in central-western NSW around midday Sunday. It also reported a broad storm line moving through western NSW. Across southern Queensland, days of torrential rain had already produced eight flood warnings, showing how storms can worsen existing water problems.

These risks were spread across a huge area on Sunday afternoon, including southern Queensland, western NSW, the ACT and eastern Victoria. Storms were expected to continue into Monday in northern NSW and southern Queensland. The Mary River downstream of Gympie was forecast to reach major flood levels at Tiaro.

Severe storms and major flood warnings occurred together because southern Queensland had already received exceptionally heavy rain. Rainfall had been several times above the monthly average after a very dry September. When more storms arrive, water can accumulate rapidly and rivers can rise to dangerous levels.

Areas around the Sunshine Coast received between 200mm and 400mm in the past week. Eight flood warnings were in place across southern Queensland. The Mary River downstream of Gympie was forecast to reach major flood levels at Tiaro on Sunday evening and into Monday. These details show how rainfall had moved beyond isolated storm impacts into river flooding.

Northern NSW and southern Queensland were expected to remain stormy into Monday as the cold front continued east. Crock called Monday the “last big bang” of the system. Its departure was expected to bring relief to people in south-east Queensland, although flood effects could continue as rivers responded.

High pressure is an area where air is generally sinking and weather systems can be steered or slowed. In this case, an area of high pressure sat over the Tasman Sea for 10 days. According to the Bureau of Meteorology, it blocked weather fronts from moving through normally.

That blocking pattern helped keep storms and rain over southern Queensland. The region experienced a sharp shift from a very dry September to October rainfall multiple times above average. Sunshine Coast areas received between 200mm and 400mm during the past week, while flood warnings developed across southern Queensland.

The pattern eventually changed when a strong enough system pushed the high-pressure block away. Crock said this typically brings severe weather. A cooler front then moved from the west, drawing tropical moisture from the north and triggering storms across central NSW and Canberra. Storms continued into Monday as the front advanced.

A cold front is the leading edge of cooler air moving into warmer air. As it advanced from the west, it lifted and displaced warmer air near the ground. That rising air can help clouds grow into thunderstorms when enough moisture is available.

In this case, the front dragged tropical moisture south from the north. The Bureau of Meteorology said the combination brought storm conditions to central New South Wales and Canberra on Sunday afternoon. A large storm line extended from the Snowy Mountains to the Queensland border, with another possible band being monitored behind it.

The setup also explains why the storm threat spread across a wide area. Cooler air continued pushing east while moist air fed the developing storms. Activity was expected through Sunday evening and into Monday in northern NSW and southern Queensland. The front’s progress was expected to produce the system’s final major burst on Monday.

A warmer climate changes the background conditions in which rain and storms develop. Warmer air can hold more moisture, which may intensify heavy rainfall when that moisture is released. Climate change can also shift rainfall patterns and increase the likelihood of some extreme weather, although the article does not link this particular storm directly to global heating.

The article reports that global heating has warmed Australia by about 1.5C since 1910. Its long-range forecast for November to January suggests rainfall will be above average across most of the country, except the far north and much of Tasmania. November is also expected to be warmer than usual across southern Australia.

Night-time temperatures are forecast to be well above average over much of the country. These trends matter because warmer nights provide less relief from daytime heat. They also show why rainfall forecasts and climate monitoring are important for preparing for floods, storms and changing seasonal conditions.