Numerical modelling studies have shown that asymmetries in vertical motion develop when a tropical cyclone is influenced by environmental vertical shear. In unsaturated flow the orientation of the vertical motion asymmetry is related to the direction of the vertical tilt, or to the shear direction if the vortex has no vertical tilt. The asymmetry is wavenumber one, with ascent 'downtilt right' (i.e. to the right of an observer facing in the direction of the vortex tilt) and descent 'downtilt left'. If the vortex does not have a vertical tilt, 'downtilt' is replaced by 'downshear'. When the inner-core becomes saturated, the orientation of the vertical motion changes such that the ascent in the inner-core is enhanced 'downshear left' and suppressed 'downshear right'. Observational studies show enhanced eyewall convection 'downshear left' and reduced convection 'downshear right', in agreement with the numerical modelling results when the inner-core of the tropical cyclone is saturated.

The aim of this study is to increase our understanding of the changes in the asymmetric vertical motion when the inner-core of a tropical cyclone saturates. We will present results from numerical experiments of idealised tropical cyclones in vertical shear using both a model with a simplified representation of moisture and a full-physics model.