The Role of Atmospheric Patterns and ENSO Phases on Extreme Precipitation Associated With Floods in the Eastern Rivers Basin of Pakistan

Abstract In Pakistan, millions of people are influenced annually by flash floods in the monsoon season (June–September). The eastern river basin, situated in the northeastern part of the country, is especially susceptible to devastating floods. This study examines the frequency and persistence of Extreme Precipitation Events (EPEs) and associated high river flows in the eastern basin, focusing on major historical floods between 1986 and 2020. The long‐term observational precipitation data was used to identify and analyze EPEs applying the peak over threshold method. Furthermore, Climate Hazards Group Infrared Precipitation with Station data (CHIRPS) and ERA5 reanalysis data sets were evaluated for comparative assessment of precipitation extremes. The analysis of five selected EPEs shows consistent synoptic‐scale patterns, including the westward movement of low‐pressure areas (LPAs), strong upper‐level divergence, and higher moisture transport both from Bay of Bengal (BoB) and Arabian Sea. Essential atmospheric features include low mean sea level pressure, upper‐level cyclonic and anticyclonic anomalies, and strong moisture convergence at 850 hPa. These dynamics, especially their interaction with westerly troughs, consistently intensify precipitation over the region. The results highlight recurring atmospheric signatures that can enhance flood forecasting and early warning systems. EPEs and high stream flows occur frequently during El Niño‐Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) neutral phases, particularly when both phenomena are simultaneously neutral. The analysis shows that ENSO‐ neutral conditions during pre‐monsoon season (March–May) are significantly linked with increased monsoon EPEs. This relationship is strongly associated with SST anomalies, with the highest correlations observed for the pre‐monsoon season: ENSO ( r = 0.51, p = 0.03) and the IOD ( r = 0.55, p = 0.02). Both correlations are statistically significant at the 95% confidence level. These results suggest that neutral ENSO and IOD phases play a dominant role in driving EPEs in the eastern river basin.