Weather forecasting: how does it work?

In short: Weather forecasts rely on measurement data, physical models of the atmosphere, and enormous computing power. They become less accurate the further ahead they look.

In more detail: Weather services gather data from weather stations, balloons, satellites, and radar, feeding it into computer models.

In detail

• Data collection: Thousands of measuring points worldwide provide temperature, pressure, humidity, and wind values.
• Numerical models: Supercomputers use physical equations to calculate how the atmosphere will develop.
• Ensemble forecasts: Several slightly varied model runs show the probability of different scenarios.
• Forecast horizon: Beyond about ten days, forecasts become unreliable due to the chaotic nature of weather.
• Local effects: Mountains, coasts, and cities influence weather on a small scale, making forecasting harder.
• Probability figures: “70% chance of rain” means it rained in 70 out of 100 similar past cases.
• Weather apps: Use the same underlying models but may differ in presentation and localisation (luftdruck-und-wetter, wolken-und-wolkenarten).