
Weather forecasts have become much more accurate. A four-day forecast today is as accurate as a one-day forecast 30 years ago. The chart here shows the difference between the forecast and the actual weather outcome for forecasts 3, 5, 7, and 10 days in advance. The metric used here is the “500 hPa geopotential height”, a commonly used meteorological measure of air pressure — which dictates weather patterns. The solid line is for the Northern Hemisphere, and the dashed line is for the Southern. Three-day forecasts have been pretty accurate since the 1980s, and have still gotten a lot better over time. Today the accuracy is around 97%. The biggest improvements we’ve seen are for longer timeframes. By the early 2000s, 5-day forecasts were “highly accurate” and 7-day forecasts are reaching that threshold today. 10-day forecasts aren’t quite there yet but are getting better. This data comes from the European Centre for Medium-Range Weather Forecasts (ECMWF), which produces global numerical weather models and publishes analyses of its errors over time. While national weather agencies use much higher-resolution processing to get local forecasts, these global models provide a crucial input into those more local systems.

With three stops it took 15½ hours from New York to Los Angeles, and the first London to Singapore link in 1934 took eight days with 22 layovers, including Athens, Cairo, Baghdad, Basra, Sharjah, Jodhpur, Calcutta, and Rangoon.[43] But long as it was, it was a considerable improvement on the approximately 30 days needed to travel by ship from South
... See moreVaclav Smil • How the World Really Works: The Science Behind How We Got Here and Where We're Going
The science of weather forecasting is a success story despite the challenges posed by the intricacies of the weather system. As you’ll find throughout this book, cases like these are more the exception than the rule when it comes to making forecasts.
Nate Silver • The Signal and the Noise: Why So Many Predictions Fail-but Some Don't
The National Weather Service’s forecasts are, it turns out, admirably well calibrated46 (figure 4-7). When they say there is a 20 percent chance of rain, it really does rain 20 percent of the time. They have been making good use of feedback, and their forecasts are honest and accurate.
Nate Silver • The Signal and the Noise: Why So Many Predictions Fail-but Some Don't
