Whether you’re planning a weekend hike, deciding what to wear to work or preparing your home for severe storms, the weather forecast is essential. You might instinctively grab your smartphone and check an app for an instant weather update.

But how many times have you looked at your app, only to step outside and see the sky painting a different picture than what’s on your screen?

As a meteorologist who operates a weather station network in Wisconsin, I’ve heard many of the same cliches time and again: “The weatherman is always wrong!” “Just wait five minutes and the weather will be different!”

Before you blame the local forecasters, let’s talk about where the data in your weather app comes from, and why it might not always show what you expect. It’s why my colleagues and I are working to bring forecast data closer to home.

The nuts and bolts of weather forecasting

Earth is huge. It has a diameter of 7,926 miles (12,756 kilometers) at the equator and has 62 miles (100 kilometers) of atmosphere overhead.

If you want a perfect weather forecast, you will have to precisely measure every molecule of the atmosphere, land and water, and perfectly predict how they will interact with each other for the next minute, day or week. This is, of course, physically impossible.

Instead, scientists run computer models. These models take the observations we do have and simulate the weather on a large scale to a remarkable degree of accuracy. In fact, storm track forecasts........

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