Why can't it rain in Guangping, Handan City, Hebei Province?

It rained in Guangping, Handan City, Hebei Province, but it didn't rain, which involves the probability and confusion of weather forecast.

In fact, the short-term weather forecast is relatively accurate, but it is not accurate for a long time. This is due to chaotic phenomena, such as Lorenz equation of weather forecast model, and nonlinear terms lead to sensitivity and chaos to initial values. A small disturbance of the initial value will lead to a big change in the later period, so the long-term weather forecast is not accurate, but from the image, the short-term weather forecast is relatively accurate. The weather process is a nonlinear dynamic system. The most obvious feature of nonlinear system is chaos, that is, it may fall into chaotic state: even if the difference is only one tenth of the initial value, after a certain time (usually not too long), the behavior of the system is no longer similar. That is to say, in the weather forecast, the error of the fourth decimal place when measuring data will lead to inaccurate long-term forecast. With the current technical means, this accuracy is far from being achieved.