Tropical Climate Update

Heavy rainfall over western Queensland

The monsoon has remained active across much of northern Australia in the past week. A persistent trough across western Queensland combined with tropical moisture to bring very heavy falls to the region from 23 March. Rainfall totals for widespread areas exceeded 200 mm for the week ending 31 March, with totals exceeding 300 mm in parts of Queensland's Channel Country and Central West. The highest weekly total (at a Bureau gauge) to 31 March was 602.0 mm at Sunbury near Isisford in Queensland's Central West District. This was greater than the site's annual mean rainfall of 379.0 mm, and one of many sites across central and western Queensland that recorded more than their annual mean rainfall for the week.

Many annual station records for daily rainfall were broken during the event. These included:

• 347.0 mm on 27 March at Sunbury (50 years of data), previous record 187.6 mm on 10 May 1989
• 227.8 mm on 27 March at Wahroongha (22 years data), previous record 110.8 mm on 19 June 2016
• 157.6 mm on 26 March at Trinidad (57 years of data), previous record 148.0 mm on 13 Jan 1976
• 158.4 mm at on 26 March Winton Airport (23 years data), previous record 117.4 mm on 28 Jan 2020.

Fortnightly forecast

Monsoonal conditions which affected much of northern Australia during the past fortnight have weakened significantly in recent days. It is unlikely that further monsoonal activity will occur across northern Australia this wet season. The month of April is typically a transitional month, with significantly lower average rainfall than March, ahead of the formal start of the northern dry season in May. Despite the breakdown of the monsoon, for the coming fortnight beginning 5 April 2025, rainfall is likely to be above average across much of northern Australia.

There is an increased chance of unusually cool maximum temperatures in northern Australia, associated with the forecast wet conditions. Unusually cool maximum temperatures are defined as those in the lowest 20% of April daytime temperatures between 1981 and 2018.

Severe Tropical Cyclone Courtney and Tropical Cyclone Dianne

Severe Tropical Cyclone Courtney formed as tropical low 27U to the north-west of Australia on 22 March. The tropical low was named tropical cyclone Courtney after it developed to Category 1 strength on 25 March. The system strengthened as it moved westward, away from mainland Australia. Courtney reached Category 5 severe tropical cyclone strength before entering the South-West Indian Ocean Basin on 29 March. It strengthened slightly in the region, before weakening as it moved over cooler sea surface temperatures. Courtney is expected to continue to weaken as it moves southwards with the addition of drier air entering the system.

Tropical low 28U developed in the monsoon trough off the Kimberley coast of Western Australia on 27 March. The system moved eastwards, before turning southwards towards the Kimberley coast. It strengthened to Category 1 late on 28 March as Tropical Cyclone Dianne. Dianne crossed the coast just north of Derby early on 29 March at Category 2 intensity and rapidly weakened as it moved inland. The system brought rain and some flooding to the region, with 153.2 mm recorded at Derby Aero to 9am on 29 March (the 2nd highest daily March total at the site in 72 years of records).

Tropical Cyclone Dianne was the 10th tropical cyclone to occur in the Australian region in the 2024–25 season, the highest number of tropical cyclones to occur since the 2021–22 season. Severe Tropical Cyclone Courtney also marks the 7th severe tropical cyclone (at least Category 3 strength) for the season; the first time since the 2014–15 season. The official Australian region tropical cyclone season runs from November to April.

For the latest information see the Bureau's 7-day tropical cyclone forecast.

Madden–Julian Oscillation weak

For much of the past week (to 29 March), the Madden–Julian Oscillation (MJO) was located over the Western Pacific region at a relatively weak strength. The influence of the MJO on northern Australia continues to reduce as it moves further away from the Australian region.

Forecasts for the MJO are mixed, with about half of the models indicating a weak or indiscernible signal of the MJO over the next fortnight, while the other half forecast a slight strengthening of the MJO over the western or central Pacific region. At this time of year, an MJO pulse in the central Pacific has only a small influence on rainfall across northern Australia. Current forecasts of the MJO suggest it will not move into Australian longitudes before the end of April.