Perth 28-day rainfall forecast
Chance of rainfall somewhere within district
Issued 27 Jul 2017
The hemispheric long wave pattern has been relatively fast moving in recent weeks. There are eight main troughs. Currently the most significant troughs are near the longitudes of South Africa, the Indian Ocean, Western Australia, New Zealand, the south Pacific, the southeast Pacific, South America, and the Atlantic Ocean. Summary: Over southern and eastern Australia the cold front events with potential to bring widespread rain are now expected about 12 August to 16 August, 16 August to 20 August, and 24 August to 28 August. Rain events originating in the tropics and moving south are possible about 24 July to 28 July. Over Western Australia the strongest cold fronts should occur about 4 August to 8 August, 8 August to 12 August, and 12 August to 16 August.
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.