Seasonal Climate Outlook

Recent climate

September rainfall was below average to average for the SWLD. September maximum temperatures were average to above average and minimum temperatures were below average to average, with some frost damage reported,

In September, the atmospheric pressure was higher than normal over the SWLD, reducing rainfall to the SWLD.

Indian Ocean sea surface temperatures north-west of Western Australia are warmer than average, which can favour above average rainfall for parts of Australia.The October to December 2021 SST forecast by the Bureau of Meteorology indicates SSTs are likely to remain warm north of WA as the negative IOD remains.

The Southern Annular Mode (SAM), also known as the Antarctic Oscillation (AAO), describes the north–south movement of the westerly wind belt that circles Antarctica, dominating the middle to higher latitudes of the southern hemisphere. The SAM index is currently positive and is expected to remain so until the end of the month. In a positive SAM phase, the belt of westerly winds contracts towards Antarctica. This results in weaker than normal westerly winds and higher pressures over southern Australia, restricting the passage of cold fronts inland. For more information, see the Bureau of Meteorology’s Climate Driver Update.

The negative Indian Ocean Dipole (IOD) has weakened, with latest IOD values falling shy of negative thresholds. While the negative IOD is near its end, the pattern of sea surface temperatures in the Indian Ocean may still be providing conditions conducive for rainfall across some parts of Australia.

The El Niño–Southern Oscillation (ENSO) is neutral. Climate models indicate further cooling of the tropical Pacific is likely over the coming months, with three of the seven models surveyed by the Bureau' cooling enough to meet La Niña criteria, while two additional models briefly touch La Niña thresholds. As a result, the Bureau's ENSO Outlook is at La Niña WATCH, which means around a 50% chance of La Niña forming. This is approximately double the normal likelihood.

The table below summarises the past month and three-month South West Land Division (SWLD) climate conditions, and can indicate what is likely to occur in the near future if climate conditions follow the current pattern.