Seasonal Climate Outlook

Summary

The Department of Agriculture and Food, Western Australia’s Statistical Seasonal Forecast (SSF) system is indicating below median rainfall for the majority of the South-West Land Division (which includes the wheatbelt) for June to July and June to October 2017.The month of May is not included in this forecast as SSF was indicating a wet May which is inconsistent when compared to the rest of the outlook and to other models and to Indian Ocean and mean sea level pressure climate conditions.

  • The SSF is indicating 0-40% chance of exceeding median rainfall for June to July for the majority of the wheatbelt. For the south coast this has increased to 40-70% chance of exceeding median. The most probable decile range map indicates decile 2-3 rainfall is most likely for the majority of the wheat-belt for June to July. Predictive skill based on April conditions is poor to moderate (50-75% consistent).
  • The Bureau of Meteorology’s current seasonal outlook indicates the South-West Land Division (SWLD) has a 20-35% chance of exceeding median rainfall for May to July. Predictive skill is moderate to good (55-75% consistent).
  • Temperature outlooks for May to July from the Bureau indicate a 65-80% chance of above normal day-time maxima for the SWLD. Skill is moderate to good at 55-75% consistent. Minimum temperature outlooks indicate a 55-75% chance of above normal night-time minima for the SWLD, with skill poor to moderate at 50-65% consistent.
  • DAFWA’s SSF is indicating a 20-60% chance of exceeding median rainfall for April to October. The most probable decile range map indicates rainfall decile of 2-3 for the majority of the SWLD. Predictive skill based on March conditions is poor to good (50-75% consistent).
  • April rainfall in the SWLD was the eighth driest on record. Maximum temperatures were above average to average whilst minimum temperatures were below average to average.

Three month outlook for the south-west of Western Australia

Statistical Seasonal Forecasting (SSF)

DAFWA’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 web page.

For the month of May, SSF was indicating very high chances of receiving median rainfall which is not in-line with the other months in the outlook or with other models. For the month of April the Pacific Ocean was warmer than normal and this is what was driving the wet outlook for May. For this reason May is not included in the outlooks.

The SSF forecast for June to July 2017 is indicating a 0-40% chance of exceeding median rainfall for the majority of the wheatbelt. For the south coast this has increased to 40-70% chance of exceeding median. The most probable decile range map indicates decile 2-3 rainfall is most likely for June to July for the majority of the SWLD and decile 4-7 along the south coast and decile 8-9 for the south-west corner and eastern parts of the Esperance shire. Predictive skill based on April conditions is poor to moderate (50-75% consistent).

SSF forecast of probability of exceeding median rainfall for June to July 2017, indicating 0-40 per cent chance of exceeding median rainfall
SSF forecast of probability of exceeding median rainfall for June to July 2017

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

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