All weather forecasts are similar, but they all have certain accuracy. Model weather forecast is to design a huge program to calculate weather forecast. By inputting the currently known weather phenomena, the future atmospheric motion state and weather conditions can be calculated. The change of weather is the result of the movement of the atmosphere around the earth. The basic laws of fluid mechanics and thermodynamics in physics can be used to analyze the motion of the atmosphere, and these laws can be written into mathematical equations in mathematical language. People use large computers to solve these mathematical equations, and then predict the future pressure, temperature, wind direction, wind speed and precipitation in a certain area ... Any prediction model can not completely simulate the evolution of the atmosphere, but can only be approximate, so there must be errors. Moreover, the error will accumulate, and the longer the prediction time, the greater the error. Extended data: Note: The forecast of 1.8- 15 days is objectively revised, but it has not been subjectively revised by forecasters, so there is some uncertainty. It can be seen that it is very important for meteorologists to make subjective corrections according to their own occupation and experience. Modify the weather forecast within 2.7 days. Based on the data of current weather conditions obtained from ground observation, high altitude detection, radar satellite and ocean buoy station, the initial field of the model is closer to the actual situation, and the simulated atmospheric change characteristics are more reliable. But for the longer-term prediction, most of the data are completely generated by model calculation, and the credibility is gradually decreasing.