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Comparison of Extreme Coastal Flooding Events Between Tropical and Mid-Latitude Weather Systems in the Delaware and Chesapeake Bays for 1980 - 2019
  • John Callahan,
  • Daniel Leathers,
  • Christina Callahan
John Callahan
Delaware Geological Survey

Corresponding Author:[email protected]

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Daniel Leathers
Department of Geography and Spatial Sciences
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Christina Callahan
Department of Geography and Spatial Sciences
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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.