Increased flooding and cyclone risk in long-range outlook

Sheep Central, October 10, 2022











INCREASED risks of widespread flooding for eastern and northern Australia and an above average number of tropical cyclones and tropical lows have been predicted in the Bureau of Meteorology’s long-range forecast for Australia’s coming severe weather season.

While severe weather can occur at any time of the year, October to April is the peak time for flooding, tropical cyclones, heatwaves, bushfires and severe thunderstorms.

The 2022-23 long-range forecast includes:

  • An increased risk of an above average number of tropical cyclones and tropical lows
  • An increased risk of widespread flooding for eastern and northern Australia
  • Normal bushfire potential in eastern states, but an elevated risk of grass fire in southern Australia
  • Increased risk of prolonged heatwaves in southern areas with higher humidity
  • Normal risk of severe thunderstorms, but with possible increase in risk of thunderstorm asthma events if conditions are dry in late spring and early summer

The bureau issued Australia’s Tropical Cyclone Season long-range forecast on 10 October in advance of the 1 November to 30 April cyclone season.

This season we have a greater than 70 per cent chance of at least 11 tropical cyclones, which is the long-term average impacting the Australian region.

Communities are urged to prepare now as there is an increased chance that the first tropical cyclone in the Australian region is likely to be earlier in the season.

This reflects the impact of current climate influences including La Niña and a negative Indian Ocean Dipole.

Despite fewer tropical cyclones in recent years, Australia has never had a season without at least one tropical cyclone crossing the coast, since records began in the early 1970s.

The bureau closely monitors tropical weather systems and, where required, issues cyclone watches and warning advice.

It is important to know your weather and know your risk – so you’re ready to act and stay safe.

Stay up to date with the latest forecast and warnings on the bureau’s website or Bureau Weather app. To receive notifications through the app, visit the notifications setting menu to get the warning information you need when it matters most.

People travelling are encouraged to update your location and enable push notifications on the Bureau Weather app to receive warnings directly to your phone.

Follow all advice from your local emergency services on what to do before, during and after severe weather.

The bureau works closely with emergency management agencies and with government at all levels to provide expert insights and to share up-to-date information.

An increased chance of more tropical cyclones

Prepare early as there is an increased chance of tropical cyclones developing earlier in the season between November and April.

This season, there is an increased chance of an above-average number of tropical cyclones including tropical lows in Australia and the surrounding region.

Tropical lows can bring heavy rainfall over land, or when at sea may signal the early stages of tropical cyclone development if they pick up wind and speed.

Australia has an average of 9 to 11 tropical cyclones each year, with around 4 crossing the coast in an average season.

Coastal areas can be affected even when tropical cyclones stay offshore, especially during high tides. The impacts can include damaging or destructive winds, heavy rain leading to flooding, and other hazards such as trees being uprooted due to wet soils, landslips in steep areas and coastal erosion.

Communities are encouraged to stay up to date with forecasts and warnings through the Bureau’s website and BOM Weather app. To receive notifications through the app, visit the notifications setting menu to get the warning information you need when it matters most.

Increased risk of widespread riverine flooding

Localised major flooding can occur in any northern Australia wet season.

This season there is an increased risk of widespread and prolonged riverine flooding across northern and eastern Australia.

Rivers are high, dams are full, and catchments are wet across much of eastern Australia, meaning any rainfall has the potential to lead to widespread flooding.

When the Bureau issues a weather or flood warning for your area, take notice and be ready to act.

Coastal flooding expected around high tides

The highest tides of the year are expected to be unusually high around 23 January 2023 on the New South Wales and southern Queensland coasts, and around 20 February 2023 on northern Queensland coasts, including in the Torres Strait.

We can predict tide heights and times as they are associated with the alignment of the earth, moon and sun orbits. Our tide predictions are sea-level forecasts based on these well-known astronomical patterns and sea-level trends at each location.

Flooding is likely to occur in low-lying areas around these unusually high tides. More severe coastal flooding could occur if coastal or offshore storms are also around at these times.

Grass fire risk increases

Bushfires are always a risk in southern Australia in Summer.

Above-average rainfall over Winter has led to good grass and vegetation growth in many areas, which can increase the risk of grass fires.

While long running large bushfires are less likely than during a drier season such as 2019–20, continuing wet conditions during Spring may further increase grass growth. This could increase fire danger during any period of hot and dry weather over summer.

Areas on the urban fringe next to grasslands may have an increased risk from grass fires.

Fewer heatwaves forecast

This coming summer, more cloud and a wetter landscape can mean a reduced number of extreme heat days compared to recent years.

However, given the long-term warming trend, even in a wet summer, some places will experience heatwaves.

While temperatures may not reach extreme levels, in southern areas heatwaves may last longer, be warmer overnight and be more humid – all of which can increase the risk to human health.

Increased risk of marine heatwaves off eastern Australia – with indications that sea temperatures will be warmer than normal for an extended timeframe. This can affect fisheries and other marine life.

The Bureau of Meteorology is now issuing heatwave warnings direct to the community through the Bureau’s website and the BOM Weather app.

The Heatwave Warning service will provide a public alert that a heat hazard is forecast within the next 4 days and help Australians to prepare for and lessen the impacts of a heatwave event.

Alerts are issued in the same way as for other severe weather events through the Bureau’s website, the BOM Weather app and telephone service.

In the event of a heatwave, heatwave warnings will be issued by the Bureau through the BOM Weather app and Bureau website, as well as media and social media, with health messages relating to heat provided by state and territory agencies.

To receive notifications through the app, visit the notifications setting menu to get the warning information you need when it matters most.

Severe storms and thunderstorms

Severe thunderstorms can cause dangerous conditions such as flash flooding, large hail, damaging winds and even tornadoes.

They are more common during the warmer months, particularly in northern New South Wales, southern Queensland, inland Western Australia and across the tropical north.

Thunderstorm asthma can be triggered by thunderstorms after high grass growth in southern Australia from October to December when pollen levels are highest.

Source: Bureau of Meteorology.


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