### Weather forecast by numerical weather prediction models

##### The conversion of atmosphere from continuous to discrete mean.

The behavior of atmosphere is determined by a set of natural laws and it can be expressed by mathematical equations. The atmospheric forecast model is a system which simulates the physical processes that take place in the real atmosphere. Although the atmosphere is a continuous mean the model equations are solved in a discrete three dimencional grid.

In numerical weather prediction the atmosphere is a mean, which is consisted by grid points. (Figure 2). Atmospheric model’s using three-dimension (Figure 3). The results eventually arise only to the specific points. For the rest of the computer is completely unaware.

Also we accept that time is not continuous and everything happens in discrete time intervals. Also we accept that time is not continuous and everything happens in discrete time intervals.Certainly the weather prediction for so small time step is not so important, however, iteration of calculations leads to weather forecast of the following days or week Actually, millions of computations are made, always based on certain principles, which is exactly what a computer can do very well .