
^{1}Department of Meteorology, Naval Postgraduate School, Monterey, CA, USA ^{2}NOAA's Hurricane Research Division, Miami, FL, USA ^{*}current address: Institut für Physik der Atmosphäre, Johannes GutenbergUniversität, Mainz, Germany Abstract. A major impediment to the intensity forecast of tropical cyclones (TCs) is believed to be associated with the interaction of TCs with dry environmental air. However, the conditions under which pronounced TCenvironment interaction takes place are not well understood. As a step towards improving our understanding of this problem, we analyze here the flow topology of a TC immersed in an environment of vertical wind shear in an idealized, threedimensional, convectionpermitting numerical experiment. A set of distinct streamlines, the socalled manifolds, can be identified under the assumptions of steady and layerwise horizontal flow. The manifolds are shown to divide the flow around the TC into distinct regions. The manifold structure in our numerical experiment is more complex than the wellknown manifold structure of a nondivergent point vortex in uniform background flow. In particular, one manifold spirals inwards and ends in a limit cycle, a mesoscale dividing streamline encompassing the eyewall above the layer of strong inflow associated with surface friction and below the outflow layer in the upper troposphere. From the perspective of a steady and layerwise horizontal flow model, the eyewall is well protected from the intrusion of environmental air. In order for the environmental air to intrude into the innercore convection, timedependent and/or vertical motions, which are prevalent in the TC innercore, are necessary. Air with the highest values of moistentropy resides within the limit cycle. This "moist envelope" is distorted considerably by the imposed vertical wind shear, and the shape of the moist envelope is closely related to the shape of the limit cycle. In a first approximation, the distribution of high and lowθ_{e} air around the TC at low to midlevels is governed by the stirring of convectively modified air by the steady, horizontal flow. Motivated by the results from the idealized numerical experiment, an analogue model based on a weakly divergent point vortex in background flow is formulated. The simple kinematic model captures the essence of many salient features of the manifold structure in the numerical experiment. A regime diagram representing realistic values of TC intensity and vertical wind shear can be constructed for the pointvortex model. The results indicate distinct scenarios of environmental interaction depending on the ratio of storm intensity and verticalshear magnitude. Further implications of the new results derived from the manifold analysis for TCs in the real atmosphere are discussed. Citation: Riemer, M. and Montgomery, M. T.: Simple kinematic models for the environmental interaction of tropical cyclones in vertical wind shear, Atmos. Chem. Phys., 11, 93959414, doi:10.5194/acp1193952011, 2011. 
