Sydney 28-day rainfall forecast
Chance of rainfall somewhere within district
Issued 25 Jan 2020
The hemispheric long wave pattern has remained stable in recent weeks. There are six main troughs. Currently the most significant troughs are near the longitudes of South Africa, the southwest Indian Ocean, Western Australia, eastern Australia, New Zealand, 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 1 February to 5 February, 6 February to 10 February, and 15 February to 19 February. Rain events originating in the tropics and moving south are possible about 9 February to 13 February, and 16 February to 20 February. Over Western Australia the strongest cold fronts should occur about 31 January to 4 February, 7 February to 11 February, and 14 February to 18 February.
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.