Summary
The Department of Primary Industries and Regional Development’s (DPIRD) Statistical Seasonal Forecast (SSF) system is indicating less than a 40% chance of exceeding median rainfall for April to June 2018 for the southern grainbelt and generally 40-60% (neutral) elsewhere. For April to October, the SSF is indicating a mixed outlook with wetter conditions expected for parts of the northern grainbelt.
- The SSF is indicating less than a 40% chance of exceeding median rainfall for the southern grainbelt for April to June 2018, with a generally neutral chance (40-60%) elsewhere. The most probable decile range map indicates decile 2-3 rainfall is most likely for southern parts, with decile 4-7 rainfall elsewhere. Predictive skill based on March conditions is poor to good (50-75% consistent).
- The Bureau of Meteorology’s current seasonal outlook indicates generally a 40-50% chance of exceeding median rainfall for April to June 2018 for the South West Land Division (SWLD). A neutral outlook (50% chance of exceeding median) does not mean average rainfall is expected. Predictive skill is mostly moderate to good (55-75% consistent). For the individual month of April, the Bureau is indicating a 30-40% chance of exceeding median rainfall for the SWLD. Given this outlook, and the long-term trend for drier autumn and early winter periods, odds favour an average or later-than-average autumn break for parts of southern Australia.
- Temperature outlooks for April to June 2018 from the Bureau indicate close to a 50% chance of above normal day-time maxima for the SWLD. Skill is moderate to good at 55-75% consistent. Minimum temperature outlooks indicate a 55-65% chance of above normal night-time minima for the SWLD, with poor to moderate skill at 50-65% consistent.
- For April to October the SSF is indicating a 60-80% chance of exceeding median rainfall for parts of the northern grainbelt and along the west coast. Along the southern coast the chance is lower at less than 40%, with neutral (40-60%) chance for the eastern grainbelt. The most probable decile rainfall map indicates decile 8-10 most likely for the northern grainbelt and decile 2-3 in southern parts. Predictive skill is poor to good, 50-75% consistent.
- March rainfall in the SWLD was below average to average. March maximum temperatures were average to above average and minimum temperatures were above average.
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 Australia 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 the Seasonal Climate Information page.
The SSF is indicating less than 40% chance of exceeding median rainfall for the southern grainbelt with neutral conditions (40-60%) elsewhere. A small section of the far northern grainbelt has higher chances at 60-80%. The most probable decile range map indicates decile 2-3 rainfall is most likely for southern parts with decile 4-7 rainfall elsewhere. Predictive skill based on March conditions is poor to good (50-70% consistent). The long-term trend has been for drier autumn and early winter periods for the WA grainbelt and this outlook is consistent with that. Most international climate models have a neutral outlook (that is no preference towards either wetter or drier than normal conditions) for this period.