MELBOURNE, Australia – The El Niño – Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) are neutral, reports the Bureau of Meteorology (BOM) of the Australian Government in its new Climate Driver Update. The Bureau’s ENSO Outlook remains at La Niña WATCH, indicating the chance of La Niña forming in 2020 is around 50%— roughly twice the average likelihood.
In the tropical Pacific Ocean, surface and sub-surface waters have cooled since April 2020. The latest weekly values have continued this trend. All surveyed international climate models anticipate further cooling is likely in the coming months with most models exceeding the La Niña threshold during spring.
Other ENSO indicators, such as the Southern Oscillation Index (SOI), trade winds, and cloudiness near the Date Line are ENSO neutral but show signs consistent with a developing La Niña. The latest trade winds have been stronger than average while the SOI has increased since the beginning of July. Equatorial cloudiness near the Date Line is below average.
Large parts of the eastern Indian Ocean are warmer than average. The Indian Ocean Dipole (IOD) is currently neutral. Half of the six surveyed models indicate negative IOD thresholds could be met or exceeded during spring.
Both La Niña and negative IOD typically increase the chance of above average rainfall across much of Australia during spring.
The Southern Annular Mode (SAM) is positive and is expected to increase to strongly positive values over the coming week before decreasing over August. In winter, a positive SAM typically reduces rainfall in southern parts of the country, but can enhance rainfall in New South Wales and southern Queensland.
The Madden–Julian Oscillation (MJO) is over the Maritime Continent but is forecast to weaken over the coming week. Its influence on rainfall patterns across northern Australia is likely to be weak.
