Seasonal Climate Outlook

Summary

The Department of Primary Industries and Regional Development’s (DPIRD) Statistical Seasonal Forecast (SSF) outlook for April to June 2022 is indicating mostly neutral (40-60%) probability of above median rainfall for the South West Land Division (SWLD). The longer lead SSF outlook for April to October is also indicating mostly neutral probability of above median rainfall.

• For April to June 2022, the SSF is mostly neutral (40-60%) probability of above median rainfall for the South West Land Division. Less than 40% probability for parts of Central West, South Coastal and South East Coastal forecast districts. Higher (60%) probability for parts of Central Wheatbelt, Lower West and South West forecast districts.  The most probable rainfall decile map indicates decile 2-3 for parts of Central West, Great Southern, South Coastal and South East Coastal forecast districts. Decile 8-9 for Lower West, South West and area around Katanning. Decile 4-7 elsewhere. Predictive skill based on March conditions is moderate to good (60-100% consistent).
• The Bureau of Meteorology’s seasonal outlook for April to June 2022 is indicating neutral (40-60%) chance of above median rainfall for the SWLD.  Predictive skill is moderate to good (55-75% consistent). The current longer-term outlook (at time of writing) for May to July 2022 is lower chances (less than 45%) with similar skill (55-75%).
• Temperature outlooks for April to June 2022, from the Bureau indicate a 60-80% chance of above average day-time maxima, with the higher chances along the coast. Skill is 65-75%. For night-time minima for the SWLD, the Bureau is indicating 70- 80% chance of exceeding above average temperatures skill is 45-55%.
• The SSF forecast for SWLD April to October 2022 rainfall is indicating mostly neutral (40-60%) probability of above median rainfall for the South West Land Division. Less than 40% probability for parts of Central West, South Coastal and South East Coastal forecast districts. Higher probability (above 60%) for the northern part of the central west, part of the lower west, south west forecast districts and around Esperance. Most likely decile range map is indicating decile 2-3 for large part of the SWLD. Decile 8-9 for Lower West, South West and northern part of the Central West forecast district. Decile 4-7 elsewhere. Skill is poor to good at 50 to 75 % consistent.
• March rainfall was average to above average for the SWLD. A series of thunderstorms brought heavy rain to parts of the northern and eastern grainbelt.  March maximum temperatures were mostly average, with minimum temperatures above average. 
• The main climate driver influencing Australia rainfall is the La Niña in the Pacific, which is past its peak. La Niña increases the likelihood of tropical cyclones within the Australian region. The destructive TC Seroja hit Kalbarri on 11 April 2021, so there is still time for a tropical cyclone to develop this season. Another climate driver to look out for is the possibility of a negative Indian Ocean Dipole developing in July. This would bring increased rainfall to eastern grainbelt and cooler days to the south. Although skill is poor at this time of the year, as autumn is the ‘predictability barrier’ for forecasting.

Three Month Outlook for the south-west of Western Australia

Statistical Seasonal Forecasting (SSF)

DPIRD’s Statistical Seasonal Forecast (SSF) system uses historical relationships between global sea surface temperature and sea level pressure with rainfall in South West Land Division to produce forecasts of rainfall for the coming months. Users can click on any station indicated on the map for location-specific forecast information from DPIRD’s Seasonal Climate Information pages.

For April to June 2022, the SSF is mostly neutral (40-60%) probability of above median rainfall for the South West Land Division. Less than 40% probability for parts of Central West, South Coastal and South East Coastal forecast districts. Higher (60%) probability for parts of Central Wheatbelt, Lower West and South West forecast districts.  The most probable rainfall decile map indicates decile 2-3 for parts of Central West, Great Southern, South Coastal and South East Coastal forecast districts. Decile 8-9 for Lower West, South West and area around Katanning. Decile 4-7 elsewhere. Predictive skill based on March conditions is moderate to good (60-100% consistent).

SSF forecast of the probability of exceeding median rainfall for April to June 2022 using data up to and including March.

Percent consistent skill of the SSF at forecasting April to June rainfall using data up to and including March.

Bureau of Meteorology seasonal climate outlook

The Bureau of Meteorology's climate forecast system for monthly and seasonal climate outlooks is the Australian Community Climate Earth-System Simulator – Seasonal (ACCESS–S2). It is a dynamical (physics-based) forecast modelling system and is a collaboration between the Bureau of Meteorology and the UK Meteorological Office.

The Bureau of Meteorology’s seasonal outlook for April to June 2022 is indicating neutral (40-60%) chance of above median rainfall for the SWLD.  Predictive skill is moderate to good (55-75% consistent). The current longer term outlook (at time of writing) for May to July 2022 is lower chances (less than 45%) with similar skill (55-75%).

Temperature outlooks for April to July 2022, from the Bureau indicate a 60-80% chance of above average day-time maxima, with the higher chances along the coast. Skill is 65-75%. For night-time minima for the SWLD, the Bureau is indicating 70- 80% chance of exceeding above average temperatures Skill is 45-55%.

Rainfall outlook for April to June 2022 for Western Australia from the Bureau of Meteorology.

Percent Consistent skill of the Bureau of Meteorology’s outlook for April to June.

Looking at other rainfall forecasting models, the majority of models are indicating neutral chance of exceeding median rainfall for the SWLD for April to June 2022.

Model distribution summary of 13 models outlook for April to June 2022 rainfall in the South West Land Division.

SSF forecast for April to October

The SSF forecast for SWLD April to October 2022 rainfall is indicating mostly neutral (40-60%) probability of above median rainfall for the South West Land Division. Less than 40% probability for parts of Central West, South Coastal and South East Coastal forecast districts. Higher probability (above 60%) for the northern part of the central west, part of the lower west, south west forecast districts and around Esperance. Most likely decile range map is indicating decile 2-3 for large part of the SWLD. Decile 8-9 for Lower West, South West and northern part of the Central West forecast district. Skill is poor to good at 50 to 75 % consistent.

SSF forecast of the probability of exceeding median rainfall for April to October 2022 using data up to and including March.

Percent consistent skill of the SSF at April to October rainfall using data up to and including March.

Recent climate

March rainfall was average to above average for the SWLD. A series of thunderstorms brought heavy rain to parts of the northern and eastern grainbelt.  March maximum temperatures were mostly average, with minimum temperatures above average.  Rainfall since 1 January has been restricted to parts of the north and eastern grainbelt.

1 January to 4 April 2022 rainfall map for the South West Land Division.

In March the atmospheric pressure was normal over the SWLD.

In March, sea surface temperatures were warmer than average around tropical Australia. The April to June, sea surface temperature outlook by the Bureau of Meteorology indicates SSTs are likely to remain warmer than normal around Western Australia

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 neutral and expected to remain neutral over the coming weeks. SAM has little influence on SWLD rainfall during autumn. For more information see the Bureau of Meteorology’s Climate Driver Update.

The Indian Ocean Dipole (IOD) is neutral. It typically has little influence on global climate from December to April due to the influence of the monsoon. Models are indicating the development of a negative IOD event by July. However, model outlooks issued at this time of the year have low skill beyond autumn. Past negative IOD events generally increase rainfall in the eastern grainbelt and bring cooler days to the south.

The 2021–22 La Niña has weakened in the tropical Pacific and is forecast to return to neutral ENSO in late autumn.

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.