Vertical Structure of Tropical Cyclones with Concentric Eyewalls as Seen by the TRMM Precipitation Radar

Ten years of data from the Tropical Rainfall Measurement Mission satellite's Precipitation Radar are analyzed to determine the typical vertical structure of the concentric eyewalls of tropical cyclones undergoing eyewall replacement. The vertical structure of the secondary (outer) eyewall is different from the primary (inner) eyewall and also different from the eyewall of single eyewall storms. The upper-troposphere portions of the outer eyewalls are like the rainbands from which they evolve. Their lower-tropospheric portions are more intense and more uniform than rainbands of single eyewall storms, suggesting that these secondary eyewalls are forming from rainbands undergoing axisymmetrization and building from below. The inner concentric eyewalls are more strongly affected by shear than are the eyewalls of single eyewall storms, while the outer eyewalls are relatively unaffected by shear, which suggests the outer eyewall is amplifying the shear-induced asymmetry of the inner eyewall.