Various aspects of the propagation of an intense laser beam through the atmosphere are considered. The basic laser‐fluid equations are presented and a linearized analysis of these equations is given which predicts a very low power threshold for Brueckner‐Jorna‐type convective instabilities. Another class of instabilities is predicted to be of more practical importance than the convective instabilities and an effective Reynolds number is derived which may help to characterize these turbulent instabilities. In the following paper by the same authors a computer solution of the full set of nonlinear equations is described and the initial development of the laser‐fluid interaction is investigated.