Are Eyewall Replacement Cycles Governed Largely by Axisymmetric Balance Dynamics

The authors question the widely held view that radial contraction of a secondary eyewall during an eyewall replacement cycle is well understood and governed largely by the classical theory of axisymmetric balance dynamics. The investigation is based on a comparison of the secondary circulation and derived tangential wind tendency between a full-physics simulation and the Sawyer‐Eliassen balance model. The comparison is made at a time when the full-physics model exhibits radial contraction of the secondary eyewall during acanonical eyewall replacement cycle.It is shownthat theSawyer‐Eliassen model is unable to capture the phenomenology of secondary eyewall radial contraction because it predicts a net spindown of the boundary layer tangential winds and does not represent the boundary layer spinup mechanism that has been articulated in recent work.