Long-lived concentric eyewalls in Typhoon Soulik (2013)

The authors report on western North Pacific Typhoon Soulik (2013), which had two anomalously long-lived concentric eyewall (CE) episodes, as identified from microwave satellite data, radar data, and total precipitable water data. The first period was 25 h long and occurred while Soulik was at category 4 intensity. The second period was 34 h long and occurred when Soulik was at category 2 intensity. A large moat and outer eyewall width were present in both CE periods, and there was a significant contraction of the inner eyewall radius from the first period to the second period. The typhoon intensity decrease was partially due to encountering unfavorable environmental conditions of low ocean heat content and dry air, even though inner eyewall contraction would generally support intensification. The T-Vmax diagram (where T is the brightness temperature and Vmax is the best track-estimated intensity) is used to analyze the time sequence of the intensity and convective activity. The convective activity (and thus the integrated kinetic energy) increased during the CE periods despite the weakening of intensity.