How did the weather forecast come from?

At present, the weather forecast is based on the current weather situation and the forecaster's experience to report tomorrow's weather. Usually, the weather of tomorrow is predicted by three levels of 500, 700 and 850 hectopascals in the air and ground conditions. Weather systems have their own laws of motion, except for some rare weather systems such as typhoons, others come regularly. For example, the arrival of cold air, the speed of movement and the scope of influence are all easy to speculate. According to these conditions, we can predict the weather tomorrow.