Extreme Precipitation Trends and Weather System Influences

Extreme precipitation events require abundant atmospheric water vapor and weather conditions that force upward motion. Previous research, based on a catalogue of extreme precipitation events for the period 1908-2009, showed that extratropical cyclones (ETCs), particularly the fronts associated with such systems, are the most important type of weather system for events in the United States. Tropical cyclones are also important in the southeast U.S. This research also showed that the events associated with ETC fronts made a disproportionate contribution to the observed increase in extreme events. This research looked at daily events exceeding the threshold for a 1-in-5yr occurrence. Recently, this catalogue was updated through 2017. The period of 2010-2017 was characterized by a continuation of the upward trend in extreme precipitation occurrences that began about 1980. Analysis of this updated catalogue indicates that fronts continue to make a disproportionate contribution to the upward trend. However, contributions to the upward trend are also made by an increase in events from tropical cyclones and mesoscale convective systems. The talk will describe these basic results and a regional analysis of this updated catalogue.