Australian tropical cyclone season outlook

The tropical cyclone season runs from 1 November to 30 April

2022–23 season Australian region tropical cyclones

  • For the Australian tropical cyclone region, as defined for the Tropical Cyclone Outlook, there were 6 tropical cyclones (Darian, Ellie, Freddy, Gabrielle, Herman and Ilsa) that formed during the northern wet season.
  • Unnamed tropical cyclone 01U formed during July prior to the wet season, increasing the count to 7 tropical cycles for the 2022–23 year.
  • The long-term average (since 1969–70) number of tropical cyclones in the Australian region is 11, while in recent decades (since 2000–01) the average is 9.
  • Only two tropical cyclones (Ellie and Ilsa) made landfall on the Australian mainland with at least Category 1 strength, which is fewer than the long term average of four.
  • Five tropical cyclones reached severe strength (at least Category 3) in the Australian region, with 3 systems (Darian, Herman and Ilsa) reaching Category 5 intensity, the highest rating, the first occasion since 2005–06.
  • When TC Ilsa crossed the Pilbara coast of Western Australia (WA) in April, it was the first coastal crossing of a Category 5 system in Australia since 2015, and the first for WA since 2009.
  • There were around 16 observed tropical lows in the Australia region during the October 2022 to April 2023 period.

Tropical Cyclone Darian

  • Tropical Low 05U formed to the north of Cocos Island on 13 December and remained as a weak system until it began moving southwards on 16 December reaching tropical cyclone strength on 18 December.
  • Tropical Cyclone Darian rapidly intensified to a Category 3 cyclone in 24 hours and continued to intensify, reaching Category 5 cyclone strength on 21 December, before moving in RSMC La Reunion Area of Responsibility.
  • Darian was the first cyclone of the northern wet season and the first to reach Category 5 strength.

Tropical Cyclone Ellie

  • Tropical Low 06U formed within the monsoon trough to the north-west of Darwin in the Timor Sea on 21 December 2022 and intensified quickly as it moved south, reaching Category 1 intensity on the evening of 22 December shortly before crossing the coast as Tropical Cyclone Ellie near Peppimenarti.
  • As a tropical low, Ellie continued moving southeast across central parts of the Northern Territory where heavy rainfall led to flooding in many communities, most notably Timber Creek, and cut major roads.
  • It became slow moving over the inland Kimberley and produced multiple days of heavy rainfall. The Fitzroy River reached its highest levels on record, peaking at 15.81 m on the afternoon of 4 January at Fitzroy Crossing, isolating the town and many other nearby communities and significantly damaging the Great Northern Highway bridge.
  • Heavy rainfall continued to be associated with the system as it traversed the Kimberley producing weekly totals of around 400 mm to 750 mm, eventually dissipating over the southwest of the Northern Territory on 9 January.

Tropical Cyclone Freddy

  • A tropical low 13U was first analysed south of Bali on 5 February 2023 and while tracking slowly south westwards away from the Australian mainland, it developed into a Category 1 system as Tropical Cyclone Freddy on 6 February 2023.
  • Freddy continued to develop as it took a west-southwest track intensifying into a Category 3 (severe) system on 7 February after a period of rapid intensification. Taking a generally westward track, Freddy fluctuated between Category 2 and Category 4 intensity with peak intensity in the Australian region on 12 February.
  • On 14 February Freddy moved into La Reunion's area of responsibility with minimal impacts to the Australian coast, however Freddy was an exceptionally long-lived cyclone which was named for 34 days (to be verified by the WMO) and causing significant impacts in Madagascar, Mozambique and Malawi. The current record of 31 days is held by Hurricane/Typhoon John in 1994.

Tropical Cyclone Gabrielle

  • Tropical low 14U formed in the Coral Sea south of the Solomon Islands on 5 February. The low moved west-southwest and developed into a Tropical Cyclone Gabrielle on 8 February as it passed to the east of Willis Island.
  • Gabrielle turned to the south and then to the southeast and on 10 February intensified into a Category 3 (severe) tropical cyclone as it moved southeast away from the Australian mainland. Gabrielle transitioned into a sub-tropical cyclone as it passed close to Norfolk Island on 11 February. The cyclone had a very large gale radius resulting in high waves causing large boulders to be flung onto the Cascade Pier damaging railings and the pier surface.
  • The low subsequently moved to the south causing significant impact to the North Island of New Zealand.

Tropical low 16U

  • Tropical Low 16U formed during an active burst of the monsoon trough on 22 February to the north of Broome in Western Australia. Tracking north-westerly, 16U crossed the North Kimberley coast on 27 February.
  • The low continued to move east over the Kimberley and into the Northern Territory between 1 and 5 March causing widespread heavy rainfall and flooding of rivers and roads producing weekly totals of around 200 mm to 400 mm.
  • The low drifted over the waters off the Gulf of Carpentaria on 5 and 6 March before moving back inland over northwest Queensland on 7 March. The slow moving low brought more heavy rainfall and flooding rains to the area at the base of the Gulf with weekly totals up to 650 mm until finally dissipating during 10 March.
  • A few sites recorded their highest March or annual daily rainfall on record, including Alexandria which recorded 262.0 mm in the 24 hours to 9 am on 3 March (its highest daily rainfall across a record of 130 years) and Century Mine which recorded 313.4 mm in the 24 hours to 9 am on 8 March (its highest daily rainfall across a record of 20 years) along with an additional 220.2 mm on 9 March.
  • Record breaking floods occurred across northwest Queensland with flood waters leading to evacuations and significant inundation of many rural properties and some towns.

Tropical Cyclone Herman

  • A weak tropical low 21U developed to the north of Cocos Islands on 28 March and tracked to the southeast over open waters.
  • The low rapidly developed and Tropical Cyclone Herman was declared on 29 March. Intensification remained rapid with Herman reaching Category 5 by 31 March.
  • Herman was a small intense system both rapidly intensifying and weakening, and on 2 April Herman turned to the west as a tropical low eventually dissipating over open waters of the Indian Ocean.

Tropical Cyclone Ilsa

  • A tropical low 23U formed in the Timor Sea on 6 April and whilst tracking slowly south westwards developed into a Category 1 system as Tropical Cyclone Ilsa on 11 April.
  • Ilsa rapidly intensified to a Category 5 tropical cyclone before crossing the north Pilbara coast on the evening of 14 April with an estimated maximum 10-minute mean wind intensity of 220 km/h. Major buildings including several pastoral stations sustained severe damage.
  • Ilsa weakened and tracked east south-eastwards inland, producing daily totals up to 100 mm along central parts for the next several days.
  • The peak 219 km/h 10-minute mean wind observation at Bedout Island is the highest ever recorded in Australia and the 289 km/h wind gust was the highest wind gust ever recorded by a Bureau of Meteorology instrument.
  • Ilsa was the first coastal crossing of a 5 system in Australia since 2015, and the first for WA since 2009.

Average to slightly above average number of tropical cyclones likely for Australia in 2021–22

  • An average to slightly-above-average number of tropical cyclones are expected for the 2021–22 Australian tropical cyclone season (November–April).
  • On average, there are 9 to 11 tropical cyclones each season in the Australian region, four of which typically cross the coast.
  • The increased likelihood of La Niña development in the tropical Pacific Ocean and average to warmer-than-average sea surface temperatures to the north of Australia have influenced this year's tropical cyclone outlook.
  • In La Niña years, the first cyclone to make landfall on the Australian coast typically occurs earlier than normal, around the middle of December. During average years, the date of the first tropical cyclone to make landfall over Australia is typically in early January.
  • Even if La Niña doesn't develop, some La Niña-like effects can still occur as tropical Pacific climate indicators approach La Niña thresholds.
  • At least one tropical cyclone has crossed the Australian coast each season since reliable records began in the 1970s.
  • Cyclone formation is rarely spread evenly throughout the season; often quiet periods are 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.
  • Like tropical cyclones, the number of tropical lows that form during La Niña years is typically greater than the number which form during non-La Niña years. 

Outlook influences

This outlook is based on the status of the El Niño–Southern Oscillation (ENSO) over the preceding July to September. ENSO has been in a neutral state since March 2021, with sea surface temperatures across the tropical Pacific Ocean cooling over the past two to three months. Climate models continue this cooling trend over the coming months, with three of seven models surveyed by the Bureau meeting La Niña criteria, while another two models briefly touch La Niña thresholds. The recent cooling combined with model outlooks mean a La Niña WATCH is currently in place. In the past when La Niña WATCH has been reached, a La Niña event has subsequently developed around 50% of the time.

Ocean temperatures are currently average to warmer than average surrounding northern parts of the country. Climate models predict waters to the north of Australia are likely to be warmer than average in the coming 3 months, marginally increasing the likelihood of tropical cyclones developing.

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. The number of tropical cyclones in the Australian region is generally higher with La Niña. In recent decades, the annual number of tropical cyclones that form in the Australian Region has decreased, from an average of 11 in the 50 years since 1970 to 9 since 2000.

Outlook by region

The outlook indicates that an average to slightly-above-average number of tropical cyclones is most likely in the Australian region and all sub-regions for 2020–21.
  • The Australian region has a 65% chance of having more tropical cyclones than average. This also means a 35% chance of fewer tropical cyclones than average. Typically, around 9 to 11 tropical cyclones form or pass through the Australian region in a season, with around four of these crossing the Australian coast in a season. Outlook accuracy for the Australian region is high.
  • The Western region is forecast to experience an average number of tropical cyclones this season, with the likelihood of more than average at 61%. The chance of fewer than average is 39%. Typically, about 15% to 40% of tropical cyclones in the Western region create coastal impacts. The average number of tropical cyclones to form in or pass through the Western region is seven each season. Outlook accuracy for the Western region is low.
  • The Northwestern sub-region has a 62% chance of more tropical cyclones than average and a 38% chance of fewer tropical cyclones than average. Typically, five cyclones form in or pass through this area each season. Around 40% of tropical cyclones, or their associated tropical lows, affect coastal areas of the Northwestern sub-region. Outlook accuracy for this region is moderate.
  • The Northern region outlook suggests a near-average number of tropical cyclones with a 57% chance of more tropical cyclones than average and a 43% chance of fewer tropical cyclones than average. Typically, the Northern region experiences between 2 and 3 cyclones. About three-quarters of the tropical cyclones in the Northern region impact coastal regions. Outlook accuracy for this region is very low.
  • The Eastern region outlook has a 66% chance of more tropical cyclones than average, with a 34% chance of fewer tropical cyclones than average. The average number of tropical cyclones for this region is four, and about a quarter of tropical cyclones in the Eastern region make landfall. Outlook accuracy for this region is low.

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