TC Lionrock (2016) Touches All the Bases during Its Lifecycle: Monsoon Gyre, Tropical Transition, TC-TC Interactions, a Predecessor Rain Event, and Extratropical Transition

Four tropical disturbances (TCs; Kompasu, Mindulle, Lionrock and TD-14W) developed from cyclonic vortices embedded in a broad monsoon gyre located over the subtropical western North Pacific in mid-August 2016. TC Lionrock was especially noteworthy because: (1) it was an intense cyclone that formed on 19–20 August southeast of Japan via the tropical transition (TT) process, a pathway that is less common in the western North Pacific as compared to the North Atlantic basin, and (2) the storm underwent multiple interactions with TCs Mindulle, Kompasu, and TD-14W that had a significant impact on its track. TC Lionrock subsequently moved southwestward well east of Taiwan as it engaged in a “Fujiwhara-like” cyclonic rotation with TCs Kompasu and Mindulle, as well as TD-14W farther to the east.

TC Lionrock’s southwestward movement ended when it made a tight cyclonic hairpin turn to the northeast prior to undergoing a strong extratropical transition (ET) as it interacted with an unusually deep and intense baroclinic trough. TC Lionrock’s ET was noteworthy because the storm made a Sandy (2012)-like “left hook” towards Japan as it underwent ET. TC Lionrock’s ET culminated in multiple extreme precipitation events that included a predecessor rain event (PRE) and devastating flooding over parts of eastern Asia in late August 2016.

TC Lionrock’s remarkable life cycle from its initial formation by the TT process to its concluding strong ET and accompanying “left hook” toward Japan presents several science opportunities. These opportunities include: (1) investigating the structure and evolution of monsoon gyre formation and the resulting multiple TC interactions within this gyre, (2) documenting the ET of TC Lionrock and its role in observed extreme precipitation events including the aforementioned PRE over eastern Asia, and (3) determining the cumulative downstream impacts of multiple TC-TC, TC-gyre, and TC-baroclinic trough interactions that culminated in the strong ET of TC Lionrock. These science opportunities motivate our investigation of the remarkable life cycle of TC Lionrock in late August 2016.