Increased rainfall volume from future convective storms in the US

Mesoscale convective system (MCS)-organized convective storms with a size of ~100 km have increased in frequency and intensity in the USA over the past 35 years ¹, causing fatalities and economic losses ² . However, their poor representation in traditional climate models hampers the understanding of their change in the future ³ . Here, a North American-scale convection-permitting model which is able to realistically simulate MSCs ⁴ is used to investigate their change by the end-of-century under RCP8.5 (ref. ⁵ ). A storm-tracking algorithm ⁶ indicates that intense summertime MCS frequency will more than triple in North America. Furthermore, the combined effect of a 15-40% increase in maximum precipitation rates and a significant spreading of regions impacted by heavy precipitation results in up to 80% increases in the total MCS precipitation volume, focussed in a 40 km radius around the storm centre. These typically neglected increases substantially raise future flood risk. Current investments in long-lived infrastructures, such as flood protection and water management systems, need to take these changes into account to improve climate-adaptation practices.