A Synoptic‐Scale Anticyclone Bridging Typhoon In‐Fa (2021) and the “21·7” Predecessor Rain Event in Henan

Abstract An exceptionally heavy rainstorm (the “21·7” Predecessor Rain Event, 21·7PRE) affected Henan Province, China, from 17 to 22 July 2021, coinciding with Typhoon In‐Fa (2021) over the western North Pacific. This study investigates how In‐Fa remotely influenced the 21·7PRE by decomposing atmospheric fields using the multiscale window transform into basic‐scale (>64 days), intraseasonal‐scale (16–64 days), and synoptic‐scale (<16 days) motions. A prominent mid‐to‐lower‐tropospheric anticyclone, located approximately 880 km west of In‐Fa, acted as intermediary circulation linking the typhoon and the rainfall event. The anticyclone channeled moisture into Henan, producing pronounced meridional moisture convergence and supplying ∼64% of the total moisture during the event. Meanwhile, intraseasonal‐scale easterlies between In‐Fa and the western Pacific subtropical high facilitated westward wave‐energy propagation, which intensified an upper‐level divergence zone over Henan Province. This upper‐level divergence, together with local mesoscale cyclone activity, played a critical role in sustaining the extreme rainfall. These results indicate that Typhoon In‐Fa exterted a substantial remote influence on the 21·7PRE through a synoptic‐scale, cold‐core anticyclonic anomaly that mediated wave‐energy propagation and organized moisture transport. The findings highlight a dynamical pathway by which tropical cyclones can affect distant predecessor rain events beyond classical moisture‐conveyor and subtropical‐high paradigms.