Tropical Climate Update

Monsoon trough contracts north of Australia

Much of tropical northern Australia recorded widespread heavy rainfall during the past week associated with the monsoon trough in the region. By 18 February the monsoon contracted northwards of the Northern Territory and it is now offshore. With the contraction of the monsoon, a ridge is directing drier south-easterly winds into southern and central parts of the Northern Territory, Western Australia and southwest Queensland.

For the fortnight beginning 22 February, rainfall is likely (60% to 80% chance) to be below average across northern parts of Western Australia, the Northern Territory and Queensland, with rainfall in the typical range further south. Maximum and minimum temperatures are likely to be above average across almost all of northern Australia.

Severe Tropical Cyclone Zelia

Severe Tropical cyclone (TC) Zelia developed as a low off the Kimberley coast in Western Australia in very warm ocean temperatures over the past week. It reached TC intensity on 12 February, rapidly intensifying to a Category 5 severe tropical cyclone late on 13 February. It crossed the coast near the mouth of the De Grey River, around 55 km to the north-east of Port Hedland, on the afternoon of 14 February as a Category 4 system. Zelia was the first TC to cross the mainland Australian coast in the 2024–25 season, the latest first crossing since the 2016–17 season. Zelia rapidly weakened and was downgraded to a tropical low as it moved inland on 15 February.

The heaviest rain from Zelia was along the Pilbara coast east of Port Hedland. The 4-day rainfall totals to 9am on 15 February of 678.4 mm at De Grey and 555.4 mm at Pardoo Station were respective annual records for these stations, each with around 100 years of daily observations. Further north-east, the 341.8 mm at Mandora was a February 4-day record (103 years of data) while inland Telfer Aero also had a February record with 280.4 mm (52 years of data).

As ex-TC Zelia passed over inland Pilbara, there was widespread heavy rainfall with daily totals of 80 to 200 mm to 9 am on 15 February, with the highest total of 278.0 mm recorded at Upper North Pole. Major flooding was recorded along the De Grey River.

Zelia was the 5th tropical cyclone in the Australian region for the 2024–25 season, and the 4th to reach severe tropical cyclone intensity (Category 3 or above).

Tropical low 20U

A weak tropical low (20U) moved along the monsoon trough from Queensland's Gulf of Carpentaria region towards the north-east tropical coast on 10 February, bringing heavy falls to parts of Cape York Peninsula. By 12 February, it had moved eastwards into the Coral Sea, bringing an end to the heavy rain along the north-east tropical Queensland coast.

For the latest details on tropical low and tropical cyclone development, check the Tropical cyclone 7 day cyclone forecast.

Madden–Julian Oscillation in the western Pacific

Over the week ending 15 February, a moderate to strong pulse of the Madden–Julian Oscillation (MJO) has progressed eastwards across the Western Pacific, enhancing tropical activity over the region, and contributing towards enhanced cloudiness and convection across northern Australia.

Climate model forecasts indicate the MJO is likely to continue to progress eastwards into the Western Hemisphere and Africa region over the coming week. However, models show a large spread in possible strength. The majority show the MJO is likely to weaken and become indiscernible as it progresses eastwards into the American latitudes, but some models maintain a weak to moderate strength MJO over the coming week to fortnight. When in the Western Hemisphere and Africa region, the MJO typically suppresses cloudiness and rainfall over northern Australia, which is consistent with the two-week outlook.