Tropical Climate Update

Australian region

Recent conditions

For the week ending 1 December, widespread tropical moisture generated high rainfall totals across much of northern Australia. Inland troughs over northern Queensland generated rainfall totals in excess of 150 mm. Mostly lower totals were observed across the Northern Territory, but widespread falls of 20–100 mm were observed from southern regions to the Top End of the Territory. The highest falls were in the northern Kimberley region of Western Australia. Due to Severe Tropical Cyclone Fina's landfall, Wyndham Aero saw a weekly rainfall total of 222.8 mm. Widespread weekly rainfall totals of 15 to 50 mm, and locally exceeding 150 mm, were observed across the Kimberley region. Several sites in the Kimberley had their highest November daily rainfall on record, including Wyndham Aero with 147.2 mm to 9am on 26 November.

High humidity and temperatures produced heatwave conditions across parts of the north, particularly for eastern Queensland where some coastal stations had their record high minimum temperature for November on the 29th and 30th.

Severe Tropical Cyclone Fina

After impacting the western Top End of the Northern Territory last week, Severe Tropical Cyclone Fina tracked over the Joseph Bonaparte Gulf in a south-westerly direction towards the northern Kimberley coast. It briefly strengthened to a Category 4 system prior to making landfall near Berkeley River mouth at 9:30 pm AWST on 24 November as a Category 3 system. Despite making landfall on an isolated and sparsely populated coastline, Fina caused significant damage to the Berkeley River Lodge. The 2 caretaker staff at the Lodge took shelter and avoided injury.

Madden–Julian Oscillation

The Madden–Julian Oscillation (MJO) is currently strong, located over the tropical central Pacific region. Forecasts from ACCESS-S and other international models suggest the MJO will rapidly weaken in the coming days as it moves into the tropical Americas, with several models indicating it will become indiscernible. Other models indicate a weak signal slowly tracking through the tropical Americas into mid-December.

At this time of year, the MJO in the central Pacific typically enhances rainfall across parts of north-eastern Australia. An MJO pulse in the tropical Americas is typically associated with below-average rainfall for much of northern and southern Australia.

Australian monsoon update

Recent conditions across the tropical regions north of Australia suggest the onset of the Australian monsoon is still some time off, with wind patterns closer to patterns typically seen in October or November than December. The MJO is also forecast to remain well away from the Maritime Continent. the region north of Australia, in the coming weeks.

Based on current forecasts and typical MJO patterns, conditions are not expected to become favourable for monsoon onset until at least early January 2026. The average date of monsoon onset at Darwin is around 28 December, so the current state of the tropics suggests a later than average onset date.

The long-range forecast for 6 to 19 December, issued on 1 December, indicates that below average rainfall is likely to very likely (60% to over 80% chance) for most of Australia, consistent with the MJO outlook.

The strong MJO over the Pacific may also prevent any further development of the active La Niña event.

International conditions

Tropical activity

The current and forecast location of the MJO suggests low tropical storm and cyclone activity for the Indian Ocean and western North Pacific in the coming fortnight.

Northern hemisphere monsoon systems remain especially active in some regions,  highlighting the anomalous wind patterns currently affecting the earth's tropical regions. Asian countries including Sri Lanka, Indonesia, Thailand, Malaysia and Vietnam suffered catastrophic flooding due to intense rainfall, leading to at least 1,000 reported deaths by 1 December. The exceptional nature of the event was at least in part due to a rare near-equatorial system (Cyclonic Storm Senyar) which formed just north of the equator in the Malacca Stait and tracked westwards over Sumatra and the Malay Peninsula. Further west, Cyclonic Storm Ditwah formed to the south of Sri Lanka, before crossing Sri Lanka's coastline prior to tracking north and dissipating over the Bay of Bengal.

Monsoon activity over the western North Pacific contributed to the development of Typhoon Koto (Verbena), which caused flooding and landslides across parts of the Philippines and Vietnam.