The Quantitative Theory of Cyclone Development

The title of this article indicates its principal theme but not its full scope, for although we shall explain the method of formulating and solving certain theoretical problems and shall interpret the answers in terms of the initial stages of development of extratropical cyclones and anticyclones, our analysis has also a wider significance. Not only does a fundamentally similar theoretical analysis apply to a wide variety of development problems (including, for example, the development of “long” waves as well as the shorter “frontal” waves and even phenomena due primarily to ordinary convective instability) so that a comprehensive analysis is desirable, but this analysis gives results of primary importance in the theory of development in general, that is, from the point of view of the general forecasting problem. We shall infer from our results that there exist, in general, certain ultimate limitations to the possibilities of weather forecasting. Certain apparently sensible questions, such as the question of weather conditions at a given time in the comparatively distant future, say several days ahead, are in principle unanswerable and the most we can hope to do is to determine the relative probabilities of different outcomes. The full significance of our theoretical problems becomes apparent only when it is clear what kind of question we should attempt to answer.