Updating forecasts
Updates are a normal part of the forecasting process. They do not mean earlier forecasts were incorrect.
Forecasts are based on the best information available at the time. They are updated as new information becomes available.
To keep forecasts as accurate as possible, we continually collect new observations. This recorded weather data comes from weather stations, radar, satellites and other parts of Australia's observation network.
We use the latest observations to build a clearer picture of the weather patterns, then update the forecasts with the most recent information. Learn how meteorologists forecast weather.
Why do forecasts change?
Forecasts change because the atmosphere changes.
Forecasting is a science based on probability. This means a forecast tells us how likely it is that a weather pattern will happen.
Looking further ahead means there are more possible weather scenarios. There is also less confidence in what will happen.
As we get closer to the forecast period, we get a clearer picture of the most likely outcome. For example:
- Yesterday's forecast might show a high chance of 20 mm of rain in your area.
- Overnight, latest observations come in and are processed by the weather model.
- A meteorologist assesses information from the model. They identify a weather system developing differently since the last forecast.
- The meteorologist applies their knowledge and expertise. They might assess the geography, look at other weather models, and real-time observations from local weather stations.
- The forecast is updated to show only 5 mm of rain for the area, instead of 20 mm.
The update does not mean the earlier forecast was wrong. It means the forecast is using the latest information.
This is why the latest forecast is always your best guide. It reflects the most recent observations, weather model guidance and meteorological expertise.
Weather models and forecast updates
Weather models use observations and mathematical calculations to simulate how the atmosphere may behave in the future.
As we get closer to the forecast period, the most recent observations help the model narrow the range of possibilities. Based on the new data, it rules out some of the earlier options. It might also present new possibilities.
Even small differences in current weather conditions can have a big impact on the forecast several days ahead. This is why forecasts further into the future are less certain than forecasts for the next few days.
Learn more about weather models and the accuracy of forecasts.