Why do so few cyclones reach their maximum potential intensity? What is it that limits tropical cyclone intensification? We examine these questions here by way of the following hypotheses:

*All tropical cyclones intensify to their thermodynamic limit unless there is an inhibiting factor; and,

*Inhibiting factors dominate tropical cyclone intensification.

In posing this hypothesis we are following the arguments of Merrill (1985) that cyclone intensification is defined largely by the inhibiting, rather than the enhancing characteristics of the environment. Our approach is to conduct a range of numerical simulations to examine the impacts of a wide variety of internal and external processes on cyclone intensification. Here we shall focus on the impact of internal convective processes and cyclone movement versus vertical wind shear. We show that subtle variations in convection can make a substantial impact on the development of downdrafts and cyclone asymmetries, with consequences for intensification. Whilst vertical shear has a substantial effect on the maximum intensity that can be achieved, so does cyclone movement and the two must be separated out for full understanding of the related processes.