  Atmospheric weather systems are coherent structures consisting of discrete
cloud cells forming patterns of rows/streets, mesoscale clusters and spiral
bands which maintain their identity for the duration of their appreciable life
times in the turbulent shear flow of the planetary Atmospheric Boundary Layer.
The existence of coherent structures (seemingly systematic motion) in turbulent
flows has been well established during the last 20 years of research in
turbulence. Numerical weather prediction models based on the inherently
non-linear Navier-Stokes equations do not give realistic forecasts because of
the following inherent limitations: (1) the non-linear governing equations for
atmospheric flows do not have exact analytic solutions and being sensitive to
initial conditions give chaotic solutions characteristic of deterministic chaos
(2) the governing equations do not incorporate the dynamical interactions and
co-existence of the complete spectrum of turbulent fluctuations which form an
integral part of the large coherent weather systems (3) limitations of
available computer capacity necessitates severe truncation of the governing
equations, thereby generating errors of approximations (4) the computer
precision related roundoff errors magnify the earlier mentioned uncertainties
exponentially with time and the model predictions become unrealistic. The
accurate modelling of weather phenomena therefore requires alternative concepts
and computational techniques. In this paper a universal theory of deterministic
chaos applicable to the formation of coherent weather structures in the ABL is
presented.
