Why is the weather forecast of China Meteorological Observatory always inaccurate?

There are many factors involved in weather change, which intersect and influence each other. At present, there is no effective weather model to predict the medium and long-term weather changes, only the changing trend.

The weather system belongs to a non-equilibrium thermodynamic system in thermodynamics, but we still lack a lot of regular understanding of weather changes at present. At present, the weather forecast in one to three days is more accurate, but the medium and long-term forecast in more than three days is not very accurate. This is a worldwide problem.