Comparison of Extreme Coastal Flooding Events Between Tropical and
Mid-Latitude Weather Systems in the Delaware and Chesapeake Bays for
1980 - 2019
Abstract
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.