How Will Precipitation Characteristics Associated with Tropical Cyclones in Diverse Synoptic Environments in the Southeast United States Respond to Climate Change?

Katherine E Hollinger Beatty , Gary M. Lackmann, Jared H. Bowden

Tropical cyclones (TCs) can produce large rainfall totals which lead to devastating flooding, loss of life, and significant damage to infrastructure. Many studies have examined future changes in TC precipitation; however, few have considered changes owing to differences in the synoptic environment during landfall. Here, we focus on three North Atlantic TCs that impacted the southeastern United States: Hurricanes Floyd (1999), Matthew (2016), and Florence (2018). While these storms were impactful when they occurred, how might the impacts of similar systems change in a future climate? We address these questions using a pseudo–global warming (PGW) approach and ensembles of convection-allowing numerical model simulations. With this method, we compare future changes in precipitation characteristics such as accumulated rainfall and rain-rate frequency and distribution to assess how these changes differ as a function of synoptic environment. Hurricanes Matthew and Floyd, which have more synoptic-scale forcing for ascent while over our study region than Hurricane Florence, exhibit higher average rain rates in the present and future, but Hurricane Florence exhibits the largest increases in rain rates with warming (34% ± 12% vs 23% ± 9% and 21% ± 6% for Hurricanes Matthew and Floyd, respectively). When we consider accumulated precipitation, Hurricanes Matthew and Floyd have larger areal increases in precipitation totals greater than 250 mm than Hurricane Florence (17 600 ± 800 km² and 22 400 ± 400 km² vs 9800 ± 500 km², respectively). These results point to the potential for future TCs in synoptically forced environments to have larger spatial footprints of heavy precipitation but smaller increases in rain rate than storms with less synoptic forcing, especially when considering overland precipitation.