Summary
Rainfall in the South West Land Division, for May to July, is likely to be below average, based on a survey of 20 international models.
- The Bureau of Meteorology’s seasonal outlook for May to July 2023, is indicating 20-30% chance of exceeding median rainfall for the SWLD, with medium skill (55-75%). The current longer-term outlook (at time of writing) for winter, June to August 2023, is also 20-30% chance of exceeding median rainfall with slightly poorer skill (50-65%).
- Temperature outlooks for May to July 2023, from the Bureau indicate an 80% chance of above average day-time maxima. Skill is moderate to good 65-75%. For night-time minima for the SWLD, the Bureau is indicating 65-80% chance of exceeding above average temperatures. Skill is mostly poor at 45-50%.
- April rainfall was average to above average, with Walpole receiving 254 mm. April maximum and minimum temperatures were very much below average.
Things to watch out as the season unfolds.
- Mean sea level pressure over the South West Land Division is forecast to be high (high pressure system), resulting in blocking highs, which will suppress rainfall from winter cold fronts.
- The Bureau of Meteorology puts out a national severe weather outlook for April- August and looks at likelihood compared to recent decades. The current watch points for the SWLD include bushfire, drought and heatwave.
- Chances of both an El Niño and a positive Indian Ocean Dipole developing from June. 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.
Three Month Outlook for the south-west of Western Australia
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 May to July 2023, is indicating 20-30% chance of exceeding median rainfall for the SWLD, with medium skill (55-75%). The current longer-term outlook (at time of writing) for winter June to August is also is 20-30% chance of exceeding median rainfall with slightly poorer skill (50-65%).
Temperature outlooks for May to July 2023, from the Bureau indicate an 80% chance of above average day-time maxima. Skill is moderate to good 65-75%. For night-time minima for the SWLD, the Bureau is indicating 65-80% chance of exceeding above average temperatures. Skill is mostly poor at 45-50%.
