Coastal flooding poses the greatest threat to human life and is often the most common source of damage from coastal storms. From 1980 to 2020, the top 6, and 17 of the top 25, costliest natural disasters in the U.S. were caused by coastal storms, most of these tropical systems. The Delaware and Chesapeake Bays, two of the largest and most densely populated estuaries in the U.S. located in the Mid-Atlantic coastal region, have been significantly impacted by strong tropical cyclones in recent decades, notably Hurricanes Isabel (2003), Irene (2011), and Sandy (2012). Current scenarios of future climate project an increase in major hurricanes and the continued rise of sea levels, amplifying coastal flooding threat. We look at all North Atlantic tropical cyclones (TC) in the International Best Track Archive for Climate Stewardship (IBTrACS) database that came within 750 km of the Delmarva Peninsula from 1980 to 2019. For each TC, skew surge and storm tide are computed at 12 NOAA tide gauges throughout the two bays. Spatial variability of the detrended and normalized skew surge is investigated through cross-correlations, regional storm rankings, and comparison to storm tracks. We find Hurricanes Sandy (2012) and Isabel (2003) had the largest surge impact on the Delaware and Chesapeake Bay, respectively. Surge response to TCs in upper and lower bay regions are more similar across bays than to the opposing region in their own bay. Distance from Delmarva and relative location of storm track play a role in the magnitude and variability of surge, although distance itself is not a strong predictor. TCs that impacted lower bay more than upper bay regions tended to stay offshore east of Delmarva, whereas TCs that impacted upper bay regions tended to stay to the west of Delmarva. Although tropical cyclones are multi-hazard weather events, there continues to be a need to improve storm surge forecasting and implement strategies to minimize the damage of coastal flooding. Results from this analysis can provide insight on the potential regional impacts of coastal flooding from tropical cyclones in the Mid-Atlantic.

Coastal flooding is one of the most costly and deadly natural hazards facing the US Mid-Atlantic region today. Impacts in this heavily populated and economically significant region are caused by a combination of the location’s exposure and natural forcing from storms and sea-level rise. Tropical cyclones (TCs) and mid-latitude (ML) weather systems each have caused extreme coastal flooding in the region. Skew surge was computed over each tidal cycle for the past 40 years (1980 – 2019) at several tide gauges in the Delaware and Chesapeake Bays to compare the meteorological component of surge for each weather type. Although TCs cause higher mean surges, ML weather systems can produce surges just as severe and occur much more frequently, peaking in the cold season (Nov – Mar). Of the top 10 largest surge events, TCs account for 30-45% in the Delaware and upper Chesapeake Bays and 40–45% in the lower Chesapeake Bay. This percentage drops to 10-15% for larger numbers of events in all regions. Mean sea-level pressure and 500 hPa geopotential height (GPH) fields of the top 10 surge events from ML weather systems show a low-pressure center west-southwest of Delmarva and a semi-stationary high-pressure center to the northeast prior to maximum surge, producing strong easterly winds. Low-pressure centers intensify under upper-level divergence as they travel eastward, and the high-pressure centers are near the GPH ridges. During lower bay events, the low-pressure centers develop further south, intensifying over warmer coastal waters, with a south-shifted GPH pattern compared to upper bay events.