Mechanisms Controlling the Complex Track of Typhoon Khanun (2023) around the Ryukyu Islands

Abstract In early August 2023, Typhoon Khanun exhibited stagnant motion around the Ryukyu Islands, moving northwestward, eastward, and then northward. This study examined the environmental factors controlling its complex trajectory using atmospheric data assimilation and typhoon forecast model results. The northwestward-to-eastward shift was primarily caused by the weakening of the subtropical high north of the typhoon and its nearly simultaneous strengthening to the south, while midlatitude westerlies had limited influence. The subsequent eastward-to-northward turn was driven by the intensification of the subtropical high to the typhoon’s east. These changes of the subtropical high were linked to the propagation of upper-level Rossby wave packets from an anticyclonic circulation anomaly over northeastern China, which developed under the influence of a tropical depression that evolved from Typhoon Doksuri.