Introduction

Hurricanes are complex dynamical systems whose intensities at any given time are affected by a variety of physical processes, some of which are internal and others of which involve interactions between the storms and their environments. Many of these processes are poorly understood, and there is presently little of any skill in forecasts of the intensity change of individual storms. While numerical weather prediction models are showing impressive skill in forecasts of hurricane tracks, computer power limits their horizontal resolution to values well below those necessary to resolve eyes and eyewalls properly, so that intensity is not well predicted.

Although it is at present very difficult to forecast individual intensity, it is generally agreed that there exist thermodynamic limits to intensity that apply in the absence of significant interaction between storms and their environment. While there remains some uncertainty about how to calculate such limits, they do appear to provide reasonable upper bounds on the intensities of observed storms, and recent evidence suggests that they may even be useful for predicting the change in intensity of individual cyclones. One particular advantage of limit calculations is they depend only on sea surface temperature and the vertical temperature structure of the atmosphere, so they are easily calculable from standard data sets. Our purpose here is to briefly review the physical basis of the limit calculations and to show examples of their utility in estimating the maximum storm intensity that may be expected over a long period of time in a given location.