Environmental Characteristics of Eyewall Replacement Cycles

Eyewall replacement cycles (ERCs) involve the formation of the secondary eyewall, its contraction, and eventual replacement of the primary eyewall. These cycles frequently occur in intense tropical cyclones (TCs), and they are associated with dramatic structural and intensity changes. In this study, the environmental characteristics of ERCs are examined using the Navy Operational Global Atmospheric Prediction System (NOGAPS) global analysis. First, concentric eyewalls are objectively identified using satellite microwave imagery in the North Atlantic and western North Pacific Ocean basins from 2003-2011. Next, four different categories are defined based upon the unified set of different observed TC intensity changes before and after the observation of concentric eyewalls. Then, the environmental composites are constructed for each of these categories using the NOGAPS analysis. Statistical significance tests are used to assess environmental similarities and differences between the groups, lending insight into the relative roles of environment and internal dynamical TC processes in eyewall replacement cycles and associated intensity changes.