Forecast Rainfall Accuracy

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Changes over the forecast period
Forecasts are updated twice a day, becoming more accurate as the date approaches, so it is important to review the forecast regularly. This page presents an example forecast showing changes to the pattern and quantity of the forecast rainfall over a 5 day period.

Comparing forecast and observed rainfall maps
Comparison of Rainfall forecast maps with related Recent rainfall maps can be useful for reviewing the accuracy of the forecasts. The comparison however, needs to allow for the different time period each map date represents. The Recent rainfall maps show rainfall measured over the 24 hour period concluding at 9 am local time of that day, while the rainfall forecast period covers the 24 hours concluding at 12 UTC (10 pm EST, 9:30 pm CST or 8 pm WST) on the previous day.

Example of change over forecast period

Forecast rainfall for Saturday 20th January 2007 ( Larger images are displayed below.)
While general correspondence between each of the forecasts is evident, the most recent maps present more accurate rainfall forecasts.
Forecast on the day Forecast 1 day earlier Forecast 2 days earlier Forecast 3 days earlier Forecast 4 days earlier
Forecast on the day Forecast 1 day earlier Forecast 2 days earlier Forecast 3 days earlier Forecast 4 days earlier

'Recent rainfall'
Observed rainfall for Saturday 20th January 2007
(9am 19 Jan - 9am 20 Jan )

This map shows the recorded rainfall for Saturday 20th. The forecast maps for the same date are shown below. Earlier forecast maps are progressively less accurate.


Forecast rainfall for Saturday 20th January 2007
(10pm 19 Jan - 10pm 20 Jan)

Forecast on 20th January

Forecast 1 day earlier
Forecast 2 days earlier


Forecast 3 days earlier

Forecast 4 days earlier


© Commonwealth of Australia 2008, Bureau of Meteorology