Understanding hurricanes

Hurricanes are one of the most fascinating of all atmospheric phenomena. Much of their intricate dynamics and thermodynamics can be explained within the realm of classical physics. However, some of their secrets remain to be unlocked. Many aspects of these weather systems are discussed by Emanuel (2005) in his erudite book entitled "Divine wind: The history and science of hurricanes". In the decade since this book appeared, further progress has been made in understanding these storms. New insights have been obtained from idealized thought experiments using numerical model simulations, supported by aircraft reconnaissance data and dropsonde soundings. These insights have led to a new paradigm for understanding hurricane intensification and structure change. Some of the key elements of recent findings will be reviewed in this article. Most previous theories of hurricanes are based on the assumption that, to a first approximation, the storms are axisymmetric. However, this assumption is really only valid for mature storms and then only in the inner core region of these storms. Nevertheless, the assumption proves to be a useful starting point for understanding some of the basic features of storms in an environment with weak vertical shear.