Summary
Rainfall in the South West Land Division, for April to June, is likely to be below average, based on a survey of 22 international models.
- The Bureau of Meteorology’s seasonal outlook for April to June 2023, is indicating 20-40% chance of exceeding median rainfall for the SWLD, with medium skill (55-65%). The current longer-term outlook (at time of writing) for May to July 2023 is 25-45% chance of exceeding median rainfall with slight poorer skill (50-65%).
- Temperature outlooks for April to June 2023, from the Bureau indicate a 80% chance of above average day-time maxima. Skill is moderate to good 55-65%. For night-time minima for the SWLD, the Bureau is indicating 70-80% chance of exceeding above average temperatures, with the higher chances along the coast. Skill is poor at 45-50%
- March rainfall was above average for the Central West and Central Wheatbelt Forecast districts. March maximum temperatures were above average. Minimum temperatures were average to above average.
Things to watch out as the season unfolds.
- Chances are rising of an El Niño developing from June. The BoM has issued an El Niño alert, which means the chances of this event are greater than normal.
- There may also be a positive Indian Ocean Dipole IOD event from late winter.
- If an El Niño coincides with a positive IOD, there is a clear signal for reduced winter-spring rainfall for large parts of the South West Land Division. The last time this happened was in 2015 – when much of the grainbelt received only decile 2-3 growing season (May to October) rainfall. Statewide grain harvest that year was around 15 mt (source GIWA).
Three Month Outlook for the south-west of Western Australia
DPIRD’s Statistical Seasonal Forecast (SSF) system, which was operational from 2012 until March 2023, will no longer be published due to advances in dynamical seasonal forecasting models, such as the Bureau’s ACCESS-S2 model.
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 United Kingdom Meteorological Office.
The Bureau of Meteorology’s seasonal outlook for April to June 2023, is indicating 20-35% chance of exceeding median rainfall for the SWLD, with medium skill (55-75%). The current longer-term outlook for May to July 2023 is 25-45% chance of exceeding median rainfall with slightly poorer skill (50-60%).
Temperature outlooks for autumn, March to May 2023, from the Bureau indicate an 80% chance of above average day-time maxima. Skill is moderate to good 65-100%. For night-time minima for the SWLD, the Bureau is indicating 70-80% chance of exceeding above average temperatures, with the higher chances along the coast. Skill is mostly poor at 45-65%.
There are numerous models which provide seasonal outlooks for the South West Land Division. These models vary in the amount of skill they have for our part of the world. 22 models from different organizations are reviewed to give a model summary for the next three months.
The majority of models are indicating below normal chances of exceeding median rainfall for the SWLD for April to June 2023.
