Tropical Climate Update

Indian Ocean Dipole influence dissipating, La Niña remains

The Indian Ocean Dipole (IOD) index has been at neutral levels for the past four weeks, as sea surface temperatures (SST) around the horn of Africa (the west IOD pole) have increased, while waters near the Sumatra coast of Indonesia (the east IOD pole) cooled.The negative IOD event will be deemed over if the weekly IOD index remains neutral into December.

The IOD has little influence on Australian climate once the monsoon trough moves into the southern hemisphere (typically December–April).

La Niña continues in the tropical Pacific Ocean, but most of climate models suggest the La Niña event will ease in early 2023. The current long-range forecast for Australia indicates above median rainfall remains likely across parts of eastern Australia during summer 2022-2023.

Read more about climate drivers in the Climate Driver Update

Madden–Julian Oscillation weakening in the tropical America

A moderate Madden–Julian Oscillation (MJO) pulse in the central Pacific is expected to move eastward into the equatorial Americas in the coming week with the majority of models indicating the MJO will weaken.

The MJO influence is mainly associated with below average rainfall in parts of Australia when the pulse is far away from Australia and Maritime Continent region in summer.

Read more about the Madden–Julian Oscillation (MJO)

Monsoon-like conditions may develop in northern Australia

A tropical low may form in the eastern Arafura Sea or Gulf of Carpentaria in the coming days in association with a deepening trough to the north of Australia. The low is expected to move across the Cape York Peninsula to the Coral Sea, but it has a very low chance to develop to tropical cyclone.

The Top End of the Northern Territory and northern Queensland may experience "monsoon-like" thunderstorms and shower activity in the coming week, but wind profiles at Darwin indicate that true monsoonal flows are yet to arrive.

Roughly one third of monsoon onsets at Darwin since 1957 have occurred in late December. On average, the monsoon onset date is 28 December. In La Niña years, onset date is about a week or two earlier, typically in mid-December.