Abstract
Meteorologists have long been concerned with questions of predictability, and it is not surprising that this interest has led to fundamental contributions to the theory of chaotic systems. Especially important has been the work of the American meteorologist, E N Lorenz; in his seminal paper of 1963, he stripped the fluid dynamics of thermal convection down to a set of three coupled nonlinear differential equations, and found by numerical experiment that even this simple-looking system with only three degrees of freedom can have very complex time-evolution. The system's behaviour can be so sensitive to the details of the initial conditions that the flow soon becomes 'unpredictable' and deterministic chaos reigns.