Tropical cyclones are among the most life threatening and destructive natural phenomena on Earth. A dynamical mechanism for cyclone intensification that has been proposed is based on the idea that patches of high vorticity associated with individual convective systems are quickly axisymmetrized, feeding their energy into the circular vortex. In this work, Stochastic Structural Stability Theory (SSST) is used to achieve a comprehensive understanding of this physical mechanism. According to SSST, the distribution of momentum fluxes arising from the field of asymmetric eddies associated with a given mean vortex structure, is obtained using a linear model of stochastic turbulence. The resulting momentum flux distribution is then coupled with the equation governing the evolution of the mean vortex to produce a closed set of eddy/mean vortex equations. We apply the SSST tools to a two dimensional, non-divergent model of stochastically forced asymmetric eddies. We show that the process intensifying a weak vortex is shearing of asymmetric eddies with small azimuthal scale that produces upgradient fluxes. For stochastic forcing with amplitude larger than a certain threshold, these upgradient fluxes lead to a structural instability of the eddy/mean vortex system and to an exponentially growing vortex.
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