Southwest 28-day rainfall forecast
Chance of rainfall somewhere within district
Issued 24 Feb 2018
The hemispheric long wave pattern has been relatively fast moving in recent weeks. There are five main troughs. Currently the most significant troughs are near the longitudes of South Africa, the southwest Indian Ocean, eastern Australia, 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 20 March to 24 March, 24 March to 28 March, and 28 March to 1 April. Rain events originating in the tropics and moving south are possible about 2 March to 6 March, 6 March to 10 March, and 26 March to 30 March. Over Western Australia the strongest cold fronts should occur about 8 March to 12 March, 17 March to 21 March, and 29 March to 2 April.
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.