Perth 28-day rainfall forecast
Chance of rainfall somewhere within district
Issued 26 May 2018
The hemispheric long wave pattern has remained stable in recent weeks. There are five main troughs. Currently the most significant troughs are near the longitudes of South Africa, the Indian Ocean, Western Australia, the south Pacific, and South America. Summary: Over southern and eastern Australia the cold front events with potential to bring widespread rain are now expected about 5 June to 9 June, 11 June to 15 June, and 27 June to 1 July. Rain events originating in the tropics and moving south are possible about 24 May to 28 May. Over Western Australia the strongest cold fronts should occur about 4 June to 8 June, 8 June to 12 June, and 27 June to 1 July.
This forecast is produced by a multi-model ensemble consisting of dynamical atmospheric models, which are forced by the latest observed atmosphere, ocean, land and ice conditions. The models are designed to simulate features of the real atmosphere, including the daily movement of long and short wave patterns in the Southern Hemisphere.
The future probability of rain in each district is estimated using output from the multi-model ensemble, combined with historical information about the difference between the model forecasts and observed rainfall.
In this deterministic framework the skill of the forecast tends to decrease with time, however the forecasts are updated daily to provide the latest estimates of rainfall probability out to 28 days.