Australian tropical cyclone season long-range forecast

Below average number of tropical cyclones is likely for Australia in 2023–24

• There is likely to be a below average number of tropical cyclones for the 2023–24 Australian tropical cyclone season (November to April).
• On average, 11 tropical cyclones form in a season in the Australia region, with 4 typically crossing the Australian coast, since reliable records began in 1969–70.
• The El Niño event in the tropical Pacific Ocean has influenced this year's tropical cyclone season forecast.
• In El Niño years, the first cyclone to make landfall on the Australian coast typically occurs later than normal, around the second week of January. This is compared to all years where the date of the first tropical cyclone to make landfall over Australia is typically in early January.
• El Niño typically reduces the total number of tropical cyclones which form in the Australian region (compared to the long-term average), as well as the number of coastal crossings; however, at least one tropical cyclone has crossed the Australian coastline in every season since reliable records began in the 1970s.
• Cyclone formation is rarely evenly spread throughout the season; quiet periods are often followed by bursts of activity.
• Tropical lows that do not intensify into cyclones, or lows that are the remnants of older cyclones, can still produce damaging winds, widespread rainfall, and dangerous flooding. These impacts can extend beyond the tropics into southern areas of the country.
• The number of tropical lows that form during El Niño years is typically fewer than the number that form during ENSO-neutral or La Niña years.
• In recent decades the frequency of tropical cyclone formation in the Australian region has decreased. Since 2000, the average number of tropical cyclones that form in a season has reduced to 9. However, the output of the Seasonal forecast uses the long-term average of 11 per season.

Seasonal forecast influences

This forecast is based on the analysis of El Niño–Southern Oscillation (ENSO) oceanic and atmospheric indicators over the preceding July to September. El Niño conditions were established in the tropical Pacific in September 2023. Prior to that, the last El Niño declared by the Bureau was in 2015–16. During July and August 2023, oceanic patterns were El Niño-like, but the atmospheric response to the warm sea surface temperatures in the central and eastern Pacific was not apparent. Climate models suggest this El Niño will persist until at least the end of the coming Australian summer.

Tropical cyclone activity in the Australian region has large variability from year to year, due to the influence of naturally occurring climate drivers, such as ENSO. In recent decades, the annual total of tropical cyclones that have formed in the Australian Region has also decreased, from an average of 11 across all seasons since Australian records began in 1969–70, to an average of 9 for the period since 2000–01.

Forecast by region

For 2023–24, the forecast indicates a likely below average number of tropical cyclones in all regions.

• The Australian region has a 80% chance of having less tropical cyclones than average. Typically, 11 tropical cyclones form or pass through the Australian region in a season, with around four of these crossing the Australian coast. Historical forecast accuracy for the Australian region is moderate-to-high.
• The Western region has a 72% chance of having less tropical cyclones than average. Typically, at least one tropical cyclone in the Western region creates coastal impacts, regardless of the number that make landfall. Each season, an average 7 tropical cyclones form in, or pass through, the Western region. Historical forecast accuracy for the Western region is moderate.
• The Northwestern sub-region has a 75% chance of having less tropical cyclones than average. Typically, 5 cyclones form in or pass through this area each season, and around 3 of these, or their associated tropical lows, affect coastal areas of the Northwestern sub-region. Historical forecast accuracy for this region is moderate.
• The Eastern region has a 76% chance of having less tropical cyclones than average. The season average number of tropical cyclones for this region is 4, and typically one of these makes landfall. Historical forecast accuracy for this region is moderate-to-high.
• The Northern region has a 61% chance of having less tropical cyclones than average. Typically, the Northern region experiences 2 or 3 cyclones each season. About 75% of tropical cyclones in the Northern region affect coastal regions in some way. Historical forecast accuracy for this region is low.

The tropical cyclone season typically runs from 1 November to 30 April, although tropical cyclones can and do form outside of those bounds. All tropical cyclones that are active between 1 July and 30 June the following year count towards the season total. The broader Australian region covers the area south of the Equator and between 90°E and 160°E, and includes Australian, Papua New Guinea, and Indonesian areas of responsibility.