### Weather forecast by numerical weather prediction models

People always made efforts in order to understand the complicated laws that govern the universe.

##### Intoduction

People always made efforts in order to understand the complicated laws that govern the universe. Ancient civilizations because of their little knowledge, created myths in order to explain the complex and phenomena. Later, some primitive methods have been created to predict some periodical phenomena, such as the season changes and the motions of the celestial bodies. Gradually, divinities were replaced by cycles, shapes, numbers and mathematics.

Nowadays, while one theory reverses the other and one standard replaces the other, something remains stable: the laws that rule nature are mathematical and God is geometrician. In 1587, Newton in his book “Principia Mathematica“ claimed that the nature laws could be described by mathematical methods. Newton described the physical laws by using complicated mathematical equations that not only were correlating the physical parameters but also were calculating their derivatives. Equations that include ratios of changes are known as differential equations and are the basic mathematical tool for the description of the atmosphere motions. The solution of these equations is unique only in case that the initial values of all the parameters are known accurately.

It is considered that the earth with the atmosphere make a closed system that follows a unique and a theoretically predictable track. Since it is known an initial condition of the atmosphere (from weather observations), it can be determined its future motion. In this way, the prediction which is made, is definite. Figure 1. Products of a prediction model in a case of a cyclone in Ionian sea in 15-01-1995