Lekima developed concentric eyewalls observed by Kenting Doppler radar on 25 September 2001 and it provided an unprecedented view of the storm°¦s complex and dramatic evolution over about 5.5 hours. Since Taiwan radar network has been established, this is the first typhoon that had concentric eyewalls.

During about 5.5 hours of eyewall replacement cycle, Lekima underwent intensity change, central pressure retrieved by Atkinson and Holliday(1977)wind-pressure relationship indicated it reduced when concentric eyawall formed. As the outer eyewall contracted, the intensity of typhoon stopped increasing and started to weaken. Later, the outer eyewall replaced the inner core and became a new primary eyewall.

The conclusion is in partial agreement with what Willoughby et al.,(1982), Willoughby(1990), Black and Willoughby(1992),Blackwell(2000) have found in their observational studies of Hurricane. The difference is that typhoon exhibited highly asymmetric structure during eyewall replacement cycle.