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Called "initial twin" conditions, they look almost the same until you really get up close - just like real twins.The 7-day weather forecast is a medium-range weather forecast based on a number of reliable weather models which reflect the weather we experience in Malta. They tested some well-established models with initial conditions that had only tiny differences. Researchers from Penn State University now report that they have found the limit of our forecasts. So, a butterfly flapping its wings in China (a tiny effect that the models would miss) could change the course of a storm in Australia weeks later. That's where even small rounding on those initial conditions - say, measuring the temperature to only 1 decimal place - will always fail to produce the same results as you would get without any rounding.Īnd those small corrections add up to a lot of error. ( ABC News: James Carmody)Įven though computers will continue to get faster, researchers have found that there's an upper limit to how far in the future we will be able to make useful predictions.īlame butterflies. Improved technology gives communities more time to prepare for severe weather. Timing is key the model needs to run quickly enough that the initial conditions are still roughly true, otherwise it might be putting out information that doesn't consider what's actually happening on the ground.

They can crunch much more data using more complex algorithms much faster than ever before. This is largely thanks to improvements in supercomputers.

Since we began using numerical weather prediction models about 60 years ago, their accuracy and reach have steadily improved. This eventually means that the model stops producing reliable results. We often have to rely on inferring things like wind speed and direction from satellites rather than measuring them directly.Īny small errors at the start begin to grow, slowly at first, and more rapidly with each time step as they get carried forward during each model run. The initial conditions are incredibly important and incredibly hard to get right, especially in a place like Australia where observation stations are few and far between. There are many forecast models, each using slightly different equations, and each model is run several times a day. One of these cycles is called a "model run", and they can take hours to complete - even for a supercomputer. The Bureau of Meteorology uses a number of different computer models for its forecasts.