Seasonal Climate Outlook

Recent climate

June rainfall was generally average in the SWLD, and below average in the South Coastal and South East Coastal Districts.June maximum temperatures were above average to very much above average, and highest on record for the whole of Western Australia. June minimum temperatures were above average. Rainfall from 1 April to date has generally been below average in the SWLD.

Rainfall decile map for 1 April to 5 July 2020 in the South West Land Division. Indicating below average rainfall for the majority of the SWLD.
Rainfall decile map for 1 April to 5 July 2020 in the South West Land Division.

In June, the atmospheric pressure was higher than normal over the SWLD.

Recent cooling of the Indian Ocean sea surface temperatures (SST) north-west of Western has reduced the moisture available to weather systems passing the SWLD. The July to September 2020, SST forecast by the Bureau of Meteorology indicates SSTs are likely to become warmer, north of WA.

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 Southern Annular Mode (SAM) is currently near neutral and is forecast to remain near neutral until the end of July. The Bureau now forecasts SAM in their Climate Driver Update.

The Indian Ocean Dipole (IOD) is currently neutral. Half of the international climate models surveyed by the Bureau suggest the development of a negative IOD by the September. Recent cooling in the Indian Ocean has eased outlooks for a negative IOD. A negative IOD typically means increased rainfall for far eastern grainbelt, and average elsewhere.

The El Niño–Southern Oscillation (ENSO) is currently neutral, however, the Bureau has raised their ENSO outlook to a La Nina WATCH. This is due to cooling in the tropical Pacific Ocean in recent months, and model outlooks suggest the likelihood of further cooling. A La Nina is often associated with above average rainfall over eastern, central and northern Australia. For further information, see the Bureau of Meteorology’s new Climate Driver Update .

The table below gives a summary of 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.

Climate Indicator

Climate Indicator Past month Past Three months
SWLD Rainfall Below average Below average to average
SWLD Mean Temperature Very much above average Very much above average
SWLD atmospheric pressure Higher Higher
Indian Ocean Sea surface temperature Normal Warmer
El Niño/Southern Oscillation (ENSO) Neutral Neutral
Indian Ocean Dipole (IOD) Neutral Neutral
Southern Annular Mode (SAM) Near neutral Positive