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

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

Landfalling 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, exhibit higher average rain rates in the present and future than the more tropical Hurricane Florence, but Florence exhibits the largest increases in rain rates (34 ± 12% versus 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 greater than 250 mm than Florence (17600±800km^2 and 22400±400km^2 versus 9800±500km^2 ). 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 over-land precipitation.