Why is the weather forecast inaccurate?

First, the theory of meteorology is not perfect. Most theories of meteorology are qualitative descriptions, or based on some preconditions, describe the basic laws of atmospheric motion. However, the motion of the atmospheric system is very complicated and unrepeatable, and human beings' understanding of the laws of atmospheric motion is still quite limited, and they can't fully understand the laws of weather changes. The current weather forecast theory is far from universal.

Second, since it is a forecast, there is the possibility of deviation. Weather forecast is a forecaster's subjective forecast of the future weather based on his own theoretical knowledge, understanding of the weather situation and experience in weather forecast. This is a subjective understanding. To put it bluntly, it is a guess, but this guess comes from the mouth of professionals and uses the technical term "weather forecast". Due to the complexity of weather forecasting theory, forecasters do not fully understand the weather situation and influencing factors, which easily leads to the failure of weather forecasting.

Third, there is still a big gap between the refinement and quantification of weather forecast and people's needs. The existing weather forecast theory is based on meteorological observation. Where the meteorological infrastructure is perfect, it takes at least a few kilometers to get to a station, and most of them only walk dozens or hundreds of kilometers to get to a station, so it is impossible to measure accurately. How can the theory it is based on be accurate? Fine can't be done, let alone quantitative? Imperfect theory, biased understanding and objective and subjective prediction all make it very difficult to refine and quantify the weather forecast, which leads forecasters to have great deviations in the existence, size and duration of the weather forecast, or even the opposite.

Fourthly, the changes of weather system are quite complicated, and there is still a long way to go to accurately forecast. The weather in every place is influenced by local weather system, surrounding weather system, underlying surface and human activities. It is often impossible to calculate whether each factor has an impact on it and how big the impact is. This can be estimated by personal knowledge and experience. And the weather is unevenly distributed in time and space. Theoretically, it is impossible to have exactly the same atmospheric state or exactly the same weather process, and it is "subjective" based on past knowledge and understanding.

Fifth, the relatively large deviation may also be related to the personal ability of the forecaster. The theory is not perfect, so it is difficult to predict accurately. If you meet some careless forecasters, the result can be imagined.