Tropical Climate Update

Cool, windy conditions for northern Australia

For the second time this fortnight, a very strong high-pressure system over southern Australia is significantly influencing weather over northern Australia. Prior to weakening and moving over the Tasman Sea later this week, this high-pressure system will deliver cooler than normal south to southeast winds to most of northern Australia. The enhanced trade winds emanating from this system will also generate strong winds over waters off northern Australia's coasts, with marine wind warnings in effect during the next few days.

Indian southwest monsoon onset delayed

The average onset date of the Indian southwest monsoon, defined as the date monsoon onset occurs at the southwestern coastal city of Kerala, is 1 June. During the past week, the northernmost extent of the monsoon was well south of its normal position for this time of year. As a result, the most recent forecast by the Indian Meteorological Department (IMD) is for monsoon onset to occur around 6 June. Despite the slightly later than normal start to the monsoon, the IMD predicts close to normal rainfall during the monsoon season across India overall.

The El Niño–Southern Oscillation in the Pacific Ocean and temperature patterns across the Indian Ocean have been shown to influence India's monsoon. The delayed onset date this year may be related to the El Niño-like conditions that have been apparent at times in 2019. While a positive Indian Ocean Dipole typically leads to drier than normal conditions across parts of Australia, it is associated with above-average rainfall during the Indian southwest monsoon.

Madden–Julian Oscillation moves over Indian Ocean

During the past week, a moderate to strong pulse of the Madden–Julian Oscillation (MJO) moved eastwards into the tropical western Indian Ocean. The location and strength of this pulse has enhanced cloudiness and rainfall over the northern Indian Ocean, and may contribute to further northwards movement and development of the Indian monsoon. The influence of the MJO over this region may wane in the coming week, with the MJO signal likely to weaken as it tracks further east, prior to moving into Maritime Continent longitudes. As a result, the enhanced rainfall patterns across the north Indian Ocean may reduce to near-average levels.

Read more about the Bureau's MJO monitoring.