No Two Hurricanes Are Alike

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Hurricane strikes in the Middle Atlantic states are rare occurrences, with Delaware and New Jersey only seeing two direct hurricane landfalls since 1800 along its shorelines, the Cape May Hurricane of 1821 (which made landfall in the Outer Banks initially) and the hurricane of 1903. Despite the region’s occasional impacts from tropical cyclones, usually in the form of heavy rainfall, the occasional brushing by a cane that races up the East Coast, or a Carolinas hit such as Isabel that results in some off the wall flooding, a direct landfall from a hurricane in our region is a rarity.

That rarity is the result of several factors. From the position of our coastline running roughly south-southwest to north-northeast along the Atlantic to tropical cyclones encountering upper level winds from the west or southwest that push the storm farther east as approaching storms gain latitude, to cooler sea surface temperatures which begin to take strength from tropical cyclones. There are many things that work against hurricanes making a direct landfall in our region.

However, what if a hurricane landfall was closer to us than Isabel, which struck the North Carolina Outer Banks in September 2003?

Bill Read, the incoming director of the National Hurricane Center, spoke on Friday night at the University of Delaware to the Delaware Valley chapter of the American Meteorological Society. Read, a Wilmington area native, spoke about not only the impacts of Hurricane Isabel on Delaware itself, but also spoke about the what-if scenario of Hurricane Isabel striking farther up the Atlantic Coast.

Using SLOSH model technology, Read during his presentation spoke about the potential surge impacts of a Category 2 Hurricane strike in the vicinity of Chincoteague, VA, which is about 190 miles north-northeast of Cape Hatteras and about 250 miles northeast of Cape Outlook, where Isabel made landfall. Had Isabel made landfall slightly farther up the coast, following the same track (northwest direction) and intensity (105 mph), storm surge figures in the Delaware Bay would have been significantly higher. For instance, at Delaware City the surge in 2003 was 8.6 feet. If an Isabel-type storm made landfall farther north, the surge at Delaware City would have been closer to 13 feet.

At times, what gets forgotten by those who are not familiar with hurricanes is that damage associated with them is not confined to a single point such as the coordinates that are given out on the news and in storm reports, but it is an area of low pressure that can take a number of different shapes and sizes. A larger storm, such as Isabel, will do more damage over a wider area of real estate. whereas a smaller hurricane (you may remember Hurricane Charley from 2004) will impact a smaller area.

Hurricanes also are driven by other forces in the atmosphere, typically taking the path of least resistance through the atmosphere. Isabel was somewhat unique in that the trajectory of the storm was northwest through the Mid-Atlantic and into Canada, thanks to a strong area of high pressure over Maine. The pressure difference between an abnormally strong (for September) high pressure and a strong low pressure (Isabel) resulted in a wide swath of tropical-storm force winds across the Mid-Atlantic. Had Isabel not been as strong or as big of a storm, the resulting pressure gradient might have been less and although it would have been windy, we might not have seen as strong an impact.
Hurricanes do impact our region to varying degrees, whether they be direct landfalls such as the cases of 1821 and 1903, or the soaking ex-hurricanes like Floyd that impact us, or the brush-by storms such as Gloria and Isabel that can bring us wind, water, and waves. With the combination of increasing population along the Delaware and New Jersey coastlines and a population that has a relatively thin hurricane history under its belt, it is always best for these coastal regions to be cognizant of the potential of hurricane impact, whether it be the soaker that Floyd was, the windbag that Isabel was, or the rare landfalling hurricane such as the Vagabond Storm of 1903. While these storms each brought a different outcome to the table, the impacts were felt nonetheless here in the Delaware Valley.

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