Tropical Climate Update

Monsoon trough developing near Australia

A monsoon trough is developing to the north of Australia and is expected to move slowly southwards reaching parts of the far north of the Northern Territory and Cape York Peninsula in Queensland during the week. Monsoon onset at Darwin typically occurs at the end of December and the latest onset date on record is 25 January 1973. Hence, if monsoon onset does not occur later this week, then this will be the latest start to the monsoon in Darwin since records commenced in the 1957-58 wet season.

Within the monsoon trough are two tropical lows, one in the Timor Sea and the other in the Torres Strait. The tropical low in the Timor Sea is forecast to move generally southwest over the next week, with a moderate risk of it developing into a tropical cyclone on Thursday. The tropical low in the Torres Strait is expected to slowly intensify and track either towards the southwest or southeast over the next few days, with a low risk of development on Thursday. Conditions are expected to become more favourable from Thursday and as a result, the potential for tropical cyclone development in either the Gulf of Carpentaria or northwestern Coral Sea will increase.

See the Bureau's Tropical Cyclone Outlooks for the Coral Sea, Northern Region including the Gulf of Carpentaria, and the Western Region for more details.

Madden-Julian Oscillation strengthens over Maritime Continent

The Madden-Julian Oscillation (MJO) redeveloped over the Maritime Continent last week, contributing to an increase in cloudiness and rainfall in the region and the development of the monsoon trough near Australia. Models show that the MJO is likely to remain active and move eastwards into the western Pacific Ocean later this week or early next week. When the MJO moves from the Maritime Continent into the western Pacific Ocean at this time of year, convection over the Australian tropics tends to be enhanced, with an increased likelihood of tropical cyclone and monsoon development in the region.

See the Bureau's current MJO monitoring for more information on the MJO.

ENSO Outlook lowered to El Niño WATCH

Recent observations and climate model outlooks suggest the immediate risk of El Niño has passed. However, there remains an increased likelihood that El Niño will develop later in 2019. The Bureau's ENSO Outlook has therefore moved to El Niño WATCH, meaning there is approximately a 50% chance of El Niño developing during the southern hemisphere autumn or winter.

Tropical Pacific sea surface and sub-surface temperatures remain warmer than average, but since late 2018 they have cooled from El Niño-like values towards ENSO-neutral values. Atmospheric indicators such as cloudiness, trade winds and the Southern Oscillation Index all continue to generally remain within the ENSO-neutral range. Three of eight climate models suggest that El Niño may establish by mid- 2019.

See the Bureau's ENSO Wrap-Up for more detail.