Single Doppler radar observation of the concentric eyewall in Typhoon Saomai, 2006, near landfall

Landfalling Typhoon Saomai (2006) was observed by the CINRAD WSR-98D radar on the southeast coast of China. This study documents the formation and evolution of a concentric eyewall episode using the axisymmetric circulation derived from the ground-based velocity track display technique. Saomai's outer eyewall formed after reaching its peak intensity, ~5 hours before landfall. Updraft, tangential wind maximum and shallow low-level inflow coincided with the high reflectivity and voriticity ring in both inner and outer eyewalls, surrounding a moat region characterized by weak downward motion and lower reflectivity. The subsidence and rain-free moat region between the two eyewalls was filled with rain and upward motion prior to landfall, indicating a breakdown in the outer eyewall which was a barrier to radial inflow. Meanwhile, the outer vorticity maximum flattened and the central pressure dropped 9 hPa. The eyewall replacement cycle didn't complete probably due to the landfall.