Tropical Climate Update

Delayed monsoon arrives across the Australian tropics

A monsoon trough has formed and extends from the Top End of the Northern Territory to northern Queensland. The arrival of the monsoon - on 10 January 2024 - was delayed, compared to the typical late-December onset. This delay may be due, in part, to the El Niño event of 2023.

While the arrival of the monsoon was later than normal, it brought welcome relief from the persistent build up conditions being experienced across northern Australia. Despite the delayed onset, it was earlier than historic records of late monsoon arrival across the tropics. The greatest delay was recorded for the 1972–73 season, with monsoon arrival on 25 January 1973. The last time the monsoon was delayed by a similar degree to the current season was in was in 2019–20 when the monsoon formed on 18 January 2020.   

Monsoon trough brings increased tropical activity across northern Australia

The arrival of the monsoon brought heavy rainfall, gusty winds and cooler conditions across the tropics. Rainfall totals of greater than 100 mm were recorded across much of tropical northern Australia. Some areas in northern Queensland and large parts of the Northern Territory received more than 200 mm for the week ending 15 January, while a small area on the North Tropical Coast and Tablelands district of Queensland received more than 400 mm.

The highest weekly total was 798.0 mm at Marco Street Alert weather station, inland from Innisfail, Far North Queensland. The highest daily rainfall total during the week ending 15 January was 334.4 mm at Port Keats Airport (Wadeye), Northern Territory, in the 24 hours to 9am on 15 January.

The arrival of the monsoon has also brought a tropical low (03U) that formed in the Arafura Sea and is currently deepening south-east of Darwin, bringing strengthening wind and increasing rainfall across the Top End. The low is currently forecast to move slowly to the southeast over the Northern Territory and is expected to bring heavy rainfall across the northwestern Northern Territory and Gregory Districts.

Catchments across the Top End, including that for the Victoria River, have been relatively wet due to intermittent rainfall over the past few weeks. The forecast rainfall will likely saturate catchments further, leading to an increased risk of riverine flooding in these areas. A flood watch has been issued for northwestern parts of the Northern Territory.

The monsoon trough has also bought about the development of a tropical low (05U) offshore of Cairns, Queensland. At this stage, this tropical low has a low chance of approaching the Australian coast, potentially as a tropical cyclone, next week. However, it may bring increased chance of rain, over the coming 7 days, to the far northern Queensland coast, in areas that have been recovering from the heavy rainfall that resulted from Tropical Cyclone Jasper in December 2023.

Tropical Cyclone Anggrek formed to the north-west of the Cocos Islands.

To the north-west of the Cocos (Keeling) Islands in the Indian Ocean, Tropical Cyclone Anggrek (TC Anggrek) has formed. It is currently a category 1 cyclone and is located an estimated 455 km north-west of the Cocos Islands. TC Anggrek currently has sustained winds of 75 km/h near its centre and wind gusts of up to 100 km/h.

TC Anggrek is expected to be slow moving, north-west of the Cocos Islands during 16 January 2024. It will likely build to a category 2 system before moving to the south on 17 and 18 January. While there is large uncertainty in the movement of TC Anggrek on the weekend, it is currently forecast to start weakening by then.

The Australian Federal Police have issued a Blue Alert for TC Anggrek. All residents and tourists on the island are to listen and watch for cyclone advice warning updates on local radio and TV as well as Cocos Keeling Island Facebook pages (Cocos Blackboard, Cocos Police and IOT News).

For further information on cyclone warnings, visit the Bureau’s Cyclone Forecast Service

Madden–Julian Oscillation to strengthen as it moves across the  Maritime Continent

A moderate Madden–Julian Oscillation (MJO) pulse is currently in the western Maritime Continent. International climate models are in an agreement that the MJO is likely to strengthen and move eastwards across the Maritime Continent to the Western Pacific over the coming fortnight.

At this time of year, when the MJO is active in the Maritime Continent and western Pacific, the chance of enhanced tropical activities and above average rainfall typically increase across northern Australia.