Eyewall Evolution of Typhoons Crossing the Philippines and Taiwan: An Observational Study

• Main Authors: Kun-Hsuan Chou, Chun-Chieh Wu, Yuqing Wang
• Format: Article
• Language: English
• Published: Chinese Geoscience Union 2011-01-01
• Series: Terrestrial, Atmospheric and Oceanic Sciences
• Subjects: Eyewall contraction; Eyewall breakdown; Eyewall reorganization
• Online Access: http://tao.cgu.org.tw/images/attachments/v226p535.pdf

This study examines the statistical characteristics of the eyewall evolution induced by the landfall process and terrain interaction over Luzon Island of the Philippines and Taiwan. Interesting eyewall evolution processes include the eyewall expansion during landfall, followed by contraction in some cases after re-emergence in warm ocean waters. Best track data, advanced satellite microwave imagers, high spatial and temporal ground-observed radar images and rain gauges are utilized to study this unique eyewall evolution process. An examination of the available microwave images of 23 typhoons crossing the Philippines between 2000 and 2010 shows that most typhoons experienced this kind of eyewall evolution, i.e., the radius of the eyewall for 87% of landfall typhoons increased during landfall; and, the radius of the eyewall for 57% of the cases contracted when the typhoons reentered the ocean after they crossed the Philippines. Furthermore, analyses of large-scale environmental conditions show that small vertical wind shear, high low-level relative humidity and sea surface temperature are important for the reorganization of the outer eyewall and the subsequent eyewall contraction when the typhoons reentered the ocean.