Extreme atmospheric wind and precipitation events have created extensive multiscale coastal, inland, and upland flooding in United States (U.S.) coastal states over recent decades, some of which takes days to hours to develop, while others can take only several tens of minutes and inundate a large area within a short period of time, thus being laterally explosive. However, their existence has not yet been fully recognized, and the fluid dynamics and the wide spectrum of spatial and temporal scales of these types of events are not yet well understood nor have they been mathematically modeled. If present-day outlooks of more frequent and intense precipitation events in the future are accurate, these coastal, inland and upland flood events, such as those due to Hurricanes Joaquin (2015), Matthew (2016), Harvey (2017) and Irma (2017), will continue to increase in the future. However, the question arises as to whether there has been a well-documented example of this kind of coastal, inland and upland flooding in the past? In addition, if so, are any lessons learned for the future? The short answer is “no”. Fortunately, there are data from a pair of events, several decades ago—Hurricanes Dennis and Floyd in 1999—that we can turn to for guidance in how the nonlinear, multiscale fluid physics of these types of compound hazard events manifested in the past and what they portend for the future. It is of note that fifty-six lives were lost in coastal North Carolina alone from this pair of storms. In this study, the 1999 rapid coastal and inland flooding event attributed to those two consecutive hurricanes is documented and the series of physical processes and their mechanisms are analyzed. A diagnostic assessment using data and numerical models reveals the physical mechanisms of downstream blocking that occurred.

Sea breezes have been observed to move inland over 100 km. These airmasses can be markedly different from regional airmasses, creating a shallow layer with differences in humidity, wind, temperature and aerosol characteristics. To understand their influence on boundary layer and cloud development on subsequent days, we identify their frequency and characteristics. We visually identified sea breeze fronts on radar passing over the Savannah River Site (SRS) between March and October during 2015–2019. The SRS is ~150 km from the nearest coastal location; therefore, our detection suggests further inland penetration. We also identified periods when sea breeze fronts may have passed but were not visually observed on radar due to the shallow sea breeze airmass remaining below the radar beam elevation that ranges between approximately 1–8 km depending on the beam angle and radar source (Columbia, SC or Charleston, SC). Near-surface atmospheric measurements indicate that the dew point temperature increases, the air temperature decreases, the variation in wind direction decreases and the aerosol size increases after sea breeze frontal passage. A synoptic classification procedure also identified that inland moving sea breezes are more commonly observed when the synoptic conditions include weak to moderate offshore winds with an average of 35 inland sea breezes occurring each year, focused primarily in the months of April, May and June.

Pietrafesa, L.J.; Bao, S.; Gayes, P.T.; Carpenter, D.D., and Kowal, J.C., 2022. Variability and trends of the Florida current and implications for the future of the Gulf Stream. Journal of Coastal Research, 38(6), 1096–1103. Coconut Creek (Florida), ISSN 0749-0208. The Gulf Stream, the North Atlantic Ocean Basin Western Boundary Current, plays a key role in moderating the climate of the North Atlantic Ocean Basin and surrounding landmasses. However, the Gulf Stream has been widely reported in the public media to be slowing down in its volumetric transport to the north, related to the reported weakening of the Atlantic Meridional Overturning Circulation. The recent exposé claims that the Gulf Stream may be in the throes of an irreversible collapse. This would have serious implications for the future climate of not only the United States, Canada, Greenland, Iceland, Scandinavia, the British Isles, and Europe, but for the entire planet, per se. In this study, investigations of the volumetric flux of the Florida Current took place that constitutes the formative beginning of the Gulf Stream at the Florida Straits to determine if there is evidence of a slowing of this major Western Boundary Current at the latitude of its beginning source. Findings include multiple, well-defined frequency and amplitude modulated internal modes of current variability in the 38-year record of Florida Current volumetric transport, ranging from weekly to monthly to seasonally to annually to interannually and decadal. The time series reveals an overall slowing of approximately 0.98×106 meters3/second (equivalent to approximately one Sverdrup), or a 2.795% drop over the nearly four past decades of daily observations.

This study addresses the limitations of and the common challenges faced by one-dimensional river-routing methods in hydrological models, including the National Water Model (NWM), in accurately representing coastal regions. We developed a two-way coupling between the NWM and the Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM). The approach demonstrated improvements in modeling coastal river dynamics, particularly during extreme events like Hurricane Matthew. The coupled model successfully captured tidal influences, storm surge effects, and complex river–river interactions that the standalone NWM missed. The approach revealed more accurate representations of peak discharge timing and magnitude as well as water storage and release in coastal floodplains. However, we also identified challenges in reconciling variable representations between hydrological and hydraulic models. This work not only enhances the understanding of coastal–riverine interactions but also provides valuable insights for the development of next-generation hydrological models. The improved modeling capabilities have implications for flood forecasting, coastal management, and climate change adaptation in vulnerable coastal areas.

The North Carolina State University Coastal and Estuary Model & Environmental Prediction System (CEMEPS) is a coupled system of mathematical models. CEMEPS contains a suite of interactively linked atmospheric, oceanic, estuary and river model components. The model architecture couples mesoscale atmospheric models or event models such as hurricanes or a suite of atmospheric variable parameterizations to ocean basin, continental margin, and estuary hydrodynamic models to a river interaction model. So, winds and precipitation are both observed and modeled and water waves and currents and water levels are predicted. Thus, full storm surge and event-related estuary to inland flooding can be accurately determined well in advance of a storm. CEMEPS output is routinely used by the North Carolina Office of the National Weather Service to make forecasts of coastal and estuary flooding during the passage of Tropical and Extra-Tropical Cyclones. While the model system is currently focused on the coasts of the Carolinas, CEMEPS could be ported to all coasts, including the U.S. Atlantic seaboard, the Gulf coast, the Pacific coast and the Great Lakes. The goal of CEMEPS is to improve the capacity of coastal communities to reduce flood impacts.