Why is weather forecast more difficult than astronomical forecast?

Very good question. I tried to express my own opinion.

I think we will all agree that weather forecast and sky forecast are both numerical forecasts. Its accuracy depends on two points, the first is the accuracy of observation, and the second is the rationality and systematicness of the model.

From the first point of view, the weather forecast did not suffer. There are tens of thousands of stations around the world, and all kinds of data collection methods are of course no less than positioning celestial bodies. Especially in some fields of astronomy, such as meteor shower, the current technology can't see the mother of the meteor at all, so naturally there will be no prediction of the position of individual meteors.

Obviously, the weather forecast suffers from the second point, the establishment of the model. Let's start with the sky forecast. For example, we need to locate the orbit of a near-earth satellite. What factors should be considered? According to high school physics, only the gravity of the earth is considered. But in fact, there will be several factors that will cause perturbation, such as the oblateness of the earth, the atmosphere of the earth, the light pressure of the sun and the perturbation of the moon. Considering these, the accuracy of orbit positioning will become very high. In other words, modern astronomy will investigate the influence of nearly 100 factors on the position of celestial bodies, which is enough to cover almost all the influence and error sources.

Then compare the weather forecast, which is obviously much more complicated. Such as a thunderstorm in summer. The principle is that strong updraft causes water vapor condensation to form convective rain. This kind of weather is sudden and local, so the problem comes. Can you accurately predict where there will be a thunderstorm? Well, let's compare it with boiled water in our daily life. When water is heated, it will bubble and even boil. Can you accurately judge where a pot of water will boil in the next moment? I guess the best physicist can't do it because the system is too complicated. Well, I believe the landlord can understand why there are often "local areas" in the thunderstorm forecast.

In addition, there is another factor that needs to be emphasized. In astronomy, there are few unpredictable disturbances, and even if there are, it will take a very long historical period before the influence will begin to appear (for example, astronomers have calculated that the orbital stability of Mercury is very poor, and there is a probability that 10% will be affected by the disturbance in the next 50 million years). Naturally, this factor can be directly ignored in short-term prediction (tens of thousands of years). However, the weather is not so simple. I believe the landlord has also heard of the butterfly effect, and the corresponding disturbance is everywhere on the earth. If we sneeze, it may become the cause of the typhoon after a while.

Please forgive me for my loose writing. If you have any questions or suggestions, please feel free to discuss with me.