The May 2015 Texas Floods vs. Strengthened El Niño Teleconnection

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. El Niño tends to increase late-spring precipitation in the southern Great Plains and this effect has intensified since 1980. There was a detectable effect of anthropogenic global warming in the physical processes that caused the persistent precipitation in May of 2015: Warming in the tropical Pacific acted to strengthen the teleconnection towards North America, modification of zonal wave-5 circulation that deepened the anomalous trough to the west of Texas, and an enhanced Great Plains low-level southerlies increasing moisture supply from the Gulf of Mexico. Attribution analysis using the CMIP5 single-forcing experiments and the CESM 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.