Abstract
This article investigates the emergence of hurricanes from chaotic swirling motions in a threeβlayer model of the tropical troposphere that includes basic parametrizations of cumulus convection and airββsea interaction. The chaotic flow is referred to as diabatic Ekman turbulence (DET), in order to emphasize that cumulus convection and Ekman pumping are critical to its behaviour. The time required for hurricane formation in DET is examined over a broad range of seaβsurface temperatures, tropical latitudes and surface exchange coefficients for moist entropy and momentum. The mean trends are sensible, but for a given set of parameters, the genesis time can vary significantly with subtle changes to the initial turbulence. Moreover, hurricanes do not always form. In the event that a tropical depression develops into a hurricane, the process is highly asymmetric. Intensification involves a shearβflow instability, the production of mesovortices and contraction of the basic circulation. Despite the complex evolution, the intensification rate is largely consistent with the expectations of a quasiβlinear stability analysis. Properties of mature hurricanes and the nature of their fluctuations are discussed in the context of the model. Copyright Β© 2009 Royal Meteorological Society