Synoptic and large‐scale drivers of extreme precipitation events in the Himalayas

Abstract Extreme precipitation events (EPEs) in the Western Himalayas (WH) have significant cross‐sector impacts, yet understanding of their seasonal characteristics and synoptic drivers remains inadequate. This study presents an analysis of EPEs across the full annual cycle of the Himalayas from 1979 to 2023, identifying their spatial and seasonal distributions and associated precursor weather regimes. Based on the frequency of seasonal EPEs, the Himalayas are categorized into winter‐dominated (Karakoram, WH, and northwest Central Himalayas [CH]) and summer‐dominated (CH to Eastern Himalayas [EH]). By clustering circulation fields during EPEs, six dominant weather regimes are identified: four monsoon‐driven (Bay of Bengal Low‐Pressure System [BoB‐LPS], Arabian Sea LPS [AS‐LPS], Monsoon‐Break, and Western‐Disturbance Monsoon [WD‐Monsoon]) and two winter‐driven (WH‐WD and CH‐WD). Each regime exhibits a distinct atmospheric circulation pattern. The BoB‐LPS and AS‐LPS regimes are characterized by quasi‐stationary blocking by an anomalous upper‐level anticyclone situated over the WH along with the LPS formed over the BoB and AS, respectively. The Monsoon‐Break cluster reflects a weakened monsoon trough and suppressed convection over the BoB and core monsoon regions. In contrast, the WH‐WD and CH‐WD clusters are associated with upper‐level cyclonic anomalies characteristic of WDs, embedded within broader wave‐train‐like circulation anomalies that are consistent with previously reported North Atlantic Oscillation (NAO)–subtropical jet (STJ)–WD pathways. There is a spatial dipole in composite precipitation: EPEs in monsoon‐driven clusters are associated with anomalous moisture transport from the BoB and AS, which results in dry conditions in the winter‐dominated Himalayas, while EPEs in WD‐driven regimes result from anomalous westerly moisture flow from the AS and associated dry conditions in the summer‐dominated Himalayas. This study offers a synoptic‐scale framework for interpreting the circulation regimes associated with Himalayan EPEs and for identifying conditions that may be favourable for their occurrence.