Southwest 28-day rainfall forecast
Chance of rainfall somewhere within district
Issued 21 Aug 2017
The hemispheric long wave pattern has remained stable in recent weeks. There are four main troughs. Currently the most significant troughs are near the longitudes of the southwest Indian Ocean, eastern Australia, the south Pacific, the southeast Pacific, and South America. Summary: Over southern and eastern Australia the cold front events with potential to bring widespread rain are now expected about 25 August to 29 August, 5 September to 9 September, and 20 September to 24 September. Rain events originating in the tropics and moving south are possible about 19 September to 23 September. Over Western Australia the strongest cold fronts should occur about 25 August to 29 August, 4 September to 8 September, and 13 September to 17 September.
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.