Authors: Suma B. Battula, Jason M. Cordeira, F. Martin Ralph – Center for Western Weather and Water Extremes, UCSD/Scripps Institution of Oceanography, La Jolla, California
Presentation Type: Lightning Talk and Poster
Title: Characteristics and skill of extreme precipitation related to atmospheric rivers and non-atmospheric rivers over the Southeast U.S.
Abstract: The results of prior work indicate that the Southeast United States (SEUS) region contains extreme Quantitative Precipitation Forecast (QPF) skill that is lower than other regions in the U.S. (e.g., the Western and Northeast US). Similarly, previous investigations have identified that atmospheric rivers (AR) play a key role in extreme precipitation events in this region (e.g., Nashville flood on May 2, 2010) and that such non-tropical processes with higher integrated vapor transport (IVT) potentially have greater QPF skill than those with lower IVT.
In this study, KMeans clustering is used to identify six distinct synoptic patterns leading to extreme precipitation in Tennessee during the period 2001-2020. These patterns exhibited distinct seasonality, with three patterns occurring in the cool season, two in the warm season, and one in the transition season. The identified patterns also demonstrate that extreme precipitation events are strongly associated with enhanced IVT and ARs over the SEUS., in addition to tropical cyclones and mesoscale convective systems. An analysis of the QPF skill associated with each pattern, derived from the GEFS Reforecast dataset, illustrates that the cool season pattern with the highest IVT and largest fraction of ARs has better skill, whereas the warm season pattern with the highest CAPE and IWV has worse skill at multiple lead times. These results provide insights into the dynamical characteristics and predictability of extreme precipitation by storm type across the SEUS.