The results of prior work indicated 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). A hypothesis is that this skill is influenced by a diversity of storm types such as Atmospheric Rivers (ARs), Mesoscale Convective Systems (MCS) and Tropical Cyclones (TCs) occurring within distinct synoptic patterns, which have resulted in significant floods such as in Nashville (2010) and Waverly (2021) Tennessee. Similarly, previous investigations have identified that synoptic patterns with higher integrated vapor transport (IVT) potentially have greater QPF skill than those with lower IVT. There is further opportunity to investigate pattern-wise contribution of storm types and QPF skill in SEUS.

This study identified six synoptic patterns associated with heavy precipitation in Tennessee. These patterns exhibited distinct seasonality, with three patterns occurring in the cool season, two in the warm season, and one in the transition season. Approximately, 66 % of heavy precipitation in cool season and 47 % in transition season is associated with coincident ARs and MCS. Pattern-wise QPF skill derived from the GEFS Reforecast dataset illustrated 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 integrated water vapor has worse skill at multiple lead times. These results provide insights into the dynamical characteristics and predictability of heavy precipitation by storm type over the SEUS.