Seasonal Climate Outlook

Summary

The Department of Primary Industries and Regional Development’s (DPIRD) Statistical Seasonal Forecast (SSF) system is indicating a 60-80% chance of exceeding median rainfall for autumn, March to May 2018 for the majority of the grainbelt.

  • The SSF is indicating a 60-80% chance of exceeding median rainfall for the majority of the South West Land Division (SWLD) for autumn, March to May 2018. The most probable decile range map indicates decile 8-10 rainfall is most likely. Predictive skill based on February conditions is poor to good (50-70% consistent). However, the long-term trend has been for drier autumn and early winter periods for the WA grainbelt and this outlook should be treated with caution.
  • The Bureau of Meteorology’s current seasonal outlook indicates a 40-50% chance of exceeding median rainfall for March to May 2018 for the SWLD. Predictive skill is poor to moderate (45-65% consistent). 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 autumn, March to May 2018 from the Bureau indicate a 55-80% chance of above normal day-time maxima for the SWLD. Skill is poor to moderate at 45-65% consistent. Minimum temperature outlooks indicate a 70-80% chance of above normal night-time minima for the SWLD, with poor to moderate skill at 45-65% consistent.
  • February rainfall in the SWLD was average to above average due as thunderstorms and showers brought rainfall to the Division, particularly to eastern parts. February maximum and minimum temperatures were below average, especially daytime maxima.

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 WA 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 a 60-80% chance of exceeding median rainfall for the majority of the SWLD. The most probable decile range map indicates decile 8-10 rainfall is most likely. Predictive skill based on February conditions is poor to good (50-70% consistent). However, the long-term trend has been for drier autumn and early winter periods for the WA grainbelt and this outlook should be treated with caution. 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 March to May, autumn 2018. Indicating a wetter than normal outlook (60-80% chance) of receiving median rainfall for the majority of the grainbelt.
SSF forecast of the probability of exceeding median rainfall for March to May, autumn 2018

Percent Consistent skill of the SSF at forecasting March to May rainfall using data up to and including February.  Skill is between 50 and 70 percent consistent.
Percent Consistent skill of the SSF at forecasting March to May rainfall using data up to and including February