Seasonal Climate Outlook

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.

SSF forecast of the probability of exceeding median rainfall for April to June 2018. Indicating a drier than normal outlook (less than 40% chance) of receiving median rainfall for southern grainbelt and neutral elsewhere.
SSF forecast of the probability of exceeding median rainfall for April to June 2018

Percent Consistent skill of the SSF at forecasting April to June rainfall using data up to and including March. Skill is 50–75% consistent.
Percent Consistent skill of the SSF at forecasting April to June rainfall using data up to and including March

Pages