"The relationship between the different natural variables (humidity, wind, temperature, etc.) is not linear"
The variable parameters on which we base the mathematical calculations of predictions make it impossible to predict the future with 100% security.
"The atmosphere is chaotic. Physically it means that there is a predictability limit beyond which the system under consideration forgets the source information."
It is composed of an infinite number of motions affecting different sizes. You can observe movements on a planetary scale, the fast flow at altitude of the jet stream and movements that occur at reduced scales the breezes, up to those affecting infinitely smaller volumes, the so-called molecular movements. The atmosphere is therefore comparable to a Matrioska Doll.
Each dimensional level of the atmosphere represents a volume in which a movement in its own right and different from the others takes place. Unfortunately, movements within the various volumes are not observable and fully described, and the analytical mathematization through meteorological instrumentation brings with it simplifications of the phenomena, which become gross errors in the prediction.
Nature is a complex system and includes those physical processes that the weather forecasting model is not able to represent in detail, since they take place within very small dimensional scales, which are not solvable by the model radiative processes, convection, ground flows, cloud micro physics.
These micro volumes, however, cannot be overlooked as they affect the flow that develops in the larger scales: parametrizes. It therefore happens that between two metric scales defined by the forecast model, the micro-scalar motions are infused and cause the removal from a just representation of the fluid atmosphere, erroneous prediction.
Meteorology is therefore a science that studies dynamic systems, starting from initial conditions imposed in order to solve mathematical equations that describe phenomena and their future evolutions. This discipline, however, is linked to Lorenz's theory of deterministic chaos.
"The atmosphere is the ideal prototype of everything in physics that is regulated by deterministic laws but which exhibits chaotic behavior," says Ravagnan of Meteomed