Why is the weather forecast on the computer so inaccurate? Thank you.

Weather forecast also needs data. Since data is needed, there must be an observation station. China has a territory of 9.6 million square kilometers. Even counting the simplest, the Observatory will not add up to five figures. So what does this mean? This shows that it is impossible for us to know the values of temperature, humidity, wind direction and other data in every place at every moment. This shows that the data of an observatory should represent the situation of a region, but will the weather conditions in this region be exactly the same? The answer is obviously no, maybe it is raining in the east and sunny in the west. If the data used in the forecast is inaccurate, the accuracy of the weather forecast can be imagined. So how to solve this problem? That's the encryption of the observatory, but it will consume a lot of manpower and material resources, and it is obviously impossible to build an observatory. At present, the main forecasting methods are numerical forecasting and manual correction. What is the numerical forecast? Simply put, it is to program the equation of motion into the computer, then import the observation data, and use the computer to calculate the future weather conditions. Maybe some people will say it's nothing. It looks very simple. However, the computational complexity of numerical prediction is too large. How big is it? The most advanced computer in the world, that is, the computer with trillions of times per second, which is often mentioned in the news, is what the Meteorological Bureau needs most besides military applications. If there is no fast computer, it is likely that you will have to calculate tomorrow's weather, and the calculation results will not come out until the day after tomorrow, so what is the significance of such numerical forecast? Moreover, the result of numerical prediction can not be calculated everywhere, and it also represents an area with a point. Moreover, for some reason, the distance between two points cannot be infinitely reduced. There are many reasons why the weather forecast is inaccurate.