The truth behind the accuracy of weather forecasts

Summary

One of the most common questions I'm asked is how accurate weather forecasts are.These queries are normally polite inquisitions; however, online comments on meteorological services can be far more hostile, even implying forecasts are borderline worthless.Let's examine these claims, starting with how accuracy has changed with time.Improving measuresContrary to recent claims that climate change is making forecasting more difficult, an increase in computer power, detailed satellite data, along with an improved scientific understanding of the atmosphere, has greatly advanced the model simulations that are the basis of modern meteorology.This has resulted in temperature forecasts improving by about one day per decade since the 1970s, and according to a Bureau of Meteorology (BOM) spokesperson, the advancements have become even more rapid in recent years."Forecast accuracy for maximum temperature has improved by two days in the last 10 years. This means that the four-day forecast issued today is as accurate as the two-day forecast issued in 2015," they said.Significant improvements have also been made in other fields, like rainfall, wind and cyclone tracks.The map below illustrates how weather models between 1974 and 2010 would have forecast the path of Cyclone Tracy, and there is little doubt if the storm was to occur today, Darwin would be given ample warning.Accuracy for the projected path of Tropical Cyclone Tracy, using models from 1974 to 2010. (Bureau of Meteorology)Are temperature forecasts accurate seven days ahead?The two main fragments of a forecast most Australians consume are temperatures and rainfall.The BOM's verification for maximum temperatures in the 2024-25 financial year shows the forecast was within 2 degrees Celsius of that observed 91 per cent of the time.But how do we judge whether that's a skilled forecast? Darwin residents with little meteorological knowledge could probably match that accuracy by just assuming tomorrow's maximum will hit the long...