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Rapid weakening of Typhoon Chan‐Hom (2015) in a monsoon gyre

2016; Wiley; Volume: 121; Issue: 16 Linguagem: Inglês

10.1002/2016jd025214

2169-8996

Jia Liang, Liguang Wu, Guojun Gu, Qingyuan Liu,

Ocean Waves and Remote Sensing

Abstract A monsoon gyre is a low‐frequency cyclonic circulation over the western North Pacific, which plays important roles in tropical cyclone formation and motion. This study shows that the interaction between a monsoon gyre and a tropical cyclone can lead to a sudden weakening of the tropical cyclone through an observational analysis of Typhoon Chan‐Hom (2015). Typhoon Chan‐Hom (2015) initially moved westward along ~10°N and sharply turned northeastward in the Philippine Sea at 0000 UTC 3 July. Its intensity decreased by 10.3 m s −1 within 12 h during the sudden northward turn. Such a rapid weakening event was failed to predict in all of the operational forecasts. It is found that Chan‐Hom was coalescing with a large‐scale monsoon gyre on the intraseasonal (15–30 day) timescale, while it experienced the sudden track change and rapid intensity weakening. The weak and loosely organized convection on the eastern side of the monsoon gyre at 1200 UTC 2 July rapidly enhanced into the well‐organized convection within 6 h. The strong convection maintaining from 1800 UTC 2 July to 0600 UTC 3 July enhanced inflows outside the radius of 500 km from the tropical cyclone center, which prevented the inward transportation of mass and moisture into Chan‐Hom, leading to the collapsing of the eastern part of the eyewall. As a result, Chan‐Hom underwent the rapid weakening even under a large‐scale environment favorable for intensification. The study suggests that the rapid weakening of a tropical cyclone can result from its interaction with a monsoon gyre.