Tropical Climate Update

Weak monsoon trough to the north of Australia

A weak monsoon trough currently sits north of the Australian mainland, extending westwards from a tropical low near Papua New Guinea to another weak tropical low to the northwest of Darwin. Model guidance suggests the trough is likely to remain weak, predominantly due to a lack of strong cross-equatorial winds flowing into the trough from the northern hemisphere.

Even in the absence of significant cross-equatorial wind flow, the monsoon trough could strengthen if a tropical cyclone developed within it. Presently, two low-pressure centres are analysed within the trough, and while there is significant uncertainty in the model guidance, models show an increased probability of one of these lows intensifying during the coming weekend. If a tropical cyclone develops, this would likely become the focus region for any heavy, widespread rainfall associated with the monsoon. Forecast models also indicate that a developing tropical low or cyclone may move southwards, potentially drawing the monsoon trough towards the north Australian coast and increasing the probability of rainfall over the Australian mainland. As with any tropical low or cyclone and potential heavy rainfall, locations and intensity are difficult to forecast and can change significantly in a short period of time.

For up-to-date information on tropical cyclone outlooks and advices in the Australian region, visit the Bureau's Current Tropical Cyclones webpage.

Weakening Madden–Julian Oscillation approaching Australian region

The monsoon trough currently to the north of Australia developed as a moderate to strong pulse of the Madden–Julian Oscillation (MJO) moved into the western Maritime Continent during the past week. At this time of the year, an MJO in this location typically leads to an increase in cloudiness and rainfall north of Australia. During the north Australian wet season (October to April) months, the MJO typically also increases the likelihood of tropical low and cyclone formation and the development of monsoonal conditions.

The current pulse of the MJO weakened significantly in the last few days. Most climate models indicate it will stall and weaken further, potentially becoming indiscernible in a few days. Some models indicate that after becoming indiscernible, the MJO might re-emerge over the Indian Ocean in a week's time and then progress along its usual easterly track back into Maritime Continent longitudes. Despite the forecast weakening of the MJO, its effects are not expected to rapidly dissipate, so the monsoon trough and tropical lows which developed in its presence are expected to persist, with enhanced rainfall continuing for the coming week and beyond. If the MJO re-strengthens in the coming week, the likelihood of active monsoon conditions for northern Australia would increase.

Read more about the Bureau's current MJO monitoring.

Tropical cyclone activity continues across Indian Ocean

Tropical cyclone activity over the Indian Ocean increased as the MJO pulse passed over the Indian Ocean during the past fortnight. Tropical cyclone Haleh which peaked in intensity as the equivalent of a category 4 Australian tropical cyclone, moved far enough south that it transitioned to an extra-tropical cyclone on 8 March while over open waters east of Madagascar.

On 10 March, tropical cyclone Idai formed, rapidly intensifying off the southeast coast of Africa, west of Madagascar, in the Mozambique Channel. This storm is currently at an intensity comparable to an Australian category 4 tropical cyclone, and may strengthen further as it moves towards the Mozambique coast in the coming days.

Further information on Idai is available from the Meteo-France centre at La Réunion.