Role of the strengthened El Niño teleconnection in the May 2015 floods over the southern Great Plains

The climate anomalies leading to the May 2015 floods in Texas and Oklahoma were analyzed in the context of El Niño teleconnection in a warmer climate. A developing El Niño tends to increase late-spring precipitation in the southern Great Plains, and this effect has intensified since 1980. Anthropogenic global warming contributed to the physical processes that caused the persistent precipitation in May 2015: Warming in the tropical Pacific acted to strengthen the teleconnection toward North America, modification of zonal wave 5 circulation that deepened the stationary trough west of Texas, and enhanced Great Plains low-level southerlies increasing moisture supply from the Gulf of Mexico. Attribution analysis using the Coupled Model Intercomparison Project Phase 5 single-forcing experiments and the Community Earth System Model Large Ensemble Project indicated a significant increase in the El Niño-induced precipitation anomalies over Texas and Oklahoma when increases in the anthropogenic greenhouse gases were taken into account.