Seasonal Climate Outlook

Recent climate

Ex-tropical cyclone Joyce brought widespread in late January and ex-tropical cyclone Kelvin brought rainfall in the eastern grainbelt and Esperance region in February. March rainfall in contrast was generally below average in the grainbelt. As a consequence, the forecast soil water map is indicating low soil water for the majority of the grainbelt. Refer to the Seasonal Climate Information page for the 5 April plant available soil water map. March maximum temperatures were average to above average and minimum temperatures were above average.

In March, the atmospheric pressure was slightly higher than normal over the south-west. The Indian Ocean sea surface temperatures northwest and west of WA are slightly cooler.

The La Niña in the tropical Pacific Ocean has ended, and ENSO neutral conditions now prevail. The ENSO Outlook is inactive, meaning there is little sign of El Niño or La Niña developing in the coming months.

The Indian Ocean Dipole (IOD) is currently neutral. IOD events are unable to form between December and April. Four out of six international models suggest a neutral IOD for autumn and early winter, while two show a shift towards a negative IOD during winter. In a negative IOD, sea surface temperatures in the western Indian Ocean are cooler relative to the east, and this pattern typically supports increased cloudiness to Australia's northwest and greater likelihood of tropical cloudbands bringing rainfall to much of Australia. However, model accuracy during autumn is lower than at other times of year, so these outlooks should be used with caution. See the Bureau of Meteorology’s IOD and Pacific Ocean interaction for details.

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. SAM is currently near neutral, but is expected to be positive by mid-April. In a positive SAM event, the belt of strong westerly winds contracts towards Antarctica. During the summer and autumn months (December through to May) the SAM shows an increasing tendency to remain in a positive phase, with westerly winds contracted towards the South Pole. A positive SAM usually means drier conditions for the south-west corner in autumn and winter.

The table below gives a summary of past month and three month south-west Western Australia (SWWA) climate conditions, and can be used as an indication of what is likely to occur in the near future, if climate conditions follow the current pattern.

Climate indicator Past month Past three months

SWWA rainfall

Below average to average Above average to average

SWWA mean temperature

Above average Average to above average

SWWA atmospheric pressure

Slightly higher Near normal

Indian Ocean sea surface temperature

Cooler Cooler

El Niño/Southern Oscillation (ENSO)

Neutral La Niña

Indian Ocean Dipole (IOD)

Neutral Neutral

Southern Annular Mode (SAM)

Neutral Positive