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Scientists Model likelihood of Category Five Hurricane at Outer Banks

In June of 2004, Geologists at LSU released a study which summarized the last 100 years of hurricane landfall and the associated storm frequencies on the Atlantic Oceans US Coastline. Geologists found that the top three likely places for a hurricane to make landfall include southern Florida, the North Gulf Coast between East Texas and the Florida Panhandle and surprisingly, the Outer Banks of North Carolina.

The study showed that the storm frequency in South Florida is lessening, while in North Carolina, specifically at the most easterly stretch of the Outer Banks, Cape Hatteras, the number of storms and subsequent hurricanes that make land fall is increasing.

The 90 mile stretch of barrier islands that compose the Outer Banks, stretching from the Virginia Border and ending at Cape Hatteras, has seen more than its share of hurricanes. The islands are not anchored to any land mass or coral, they are merely sand bars peeking through the ocean. As “free floating” islands, with an irregular coast line and a severe continental slope, the Outer Banks have all of the geographical properties that attract a Hurricane. At Cape Hatteras, the furthest easterly point, the Banks extend 13 miles into the Atlantic Ocean from the nearest land mass and are a mere 40 miles from the Gulf Coast Current – the “highway” used by most hurricanes.

With Hazel, in 1959 (a category 4), in 1996 Fran (category 3) and in 1999 Floyd (category 2), the frequency, the severity and the further odds of tropical storms hitting North Carolina continues to keep meteorologists on the look out, according to the State Climate Office. The SCO, like the geologists at LSU, used history as a precursor for determining the storm future of the Outer Banks.

“North Carolina has a long and notorious history of destruction by hurricanes. Ever since the first expeditions to Roanoke Island in 1586, hurricanes are recorded to have caused tremendous damage to the state. Reliable classification of the intensity of tropical cyclones began in 1886. Since that time, there have been 951 tropical cyclones that have been recorded in the Atlantic Ocean and the Gulf of Mexico. Approximately 166 or 17.5% of those tropical cyclones passed within 300 miles of North Carolina

The coast of North Carolina can expect to receive a tropical storm or a hurricane once every four years, while a tropical cyclone affects the state every 1.3 years.” SCO

What Does the Future Hold?

With historical information in hand, the SCO focused its studies on the increased storm activity during the last thirty years. Not only has the frequency of tropical storms increased along the North Carolina Coast, but also the intensity (measured by the amount of damage) has increased. Their hypothesis is that future storms will be far greater in quantity, and far more intense. Their objectives included studying the effects of El Nino and La Nina on the sea surface temperature (SST). Noted by the SCO was the logical increase of the number of tropical storms and subsequent Hurricanes during El Nino. A Hurricane derives its power from the heat and condensation of the water over which it travels; a warmer water temperature like that experienced during El Nino “fuels” a tropical storm and increases the probable intensity of a powerful hurricane, like Katrina.

What would happen to the Outer Banks after a Category Five Hurricane?

North Carolina has never seen the likes of a category five Hurricane with sustained winds of greater than 155 mph and sea surges of 15-18’ feet. A hurricane of this magnitude along with associated sea surges is likely to eradicate all or portions of the islands. Many times during the past century, the islands have been inundated, leaving only traces of sand and protective dunes, and this during category two hurricanes.

The Outer Banks are less than ½ mile wide in many spots, and a 15-18’ storm surge, has the potential to completely flood the barrier islands, causing them to disappear from the coastline. The coastline is so fragile, and the continental slope is so severe that scientists seek grants from agencies such as Sea Grant to fund an ongoing study to track the shape of the coast and the erosion every five years. The studies show the current position of the islands via satellite photos and compare them for loss of coast line to the previous picture.

Reviewing these maps shows that the coast line is receding from .5 to 1.5’ each year and that the islands are migrating to the south. Rising sea-levels and prevailing northeast winds, cause the Outer Banks to move towards land. During a hurricane, the winds wash away homes, and form new inlets while closing others and the entire coast line can change in a matter of hours as the sand is swept further out to sea. One category five hurricane could remove the all of the protective dunes, man made improvements and cause ocean water to enter the estuaries destroying much of the islands beauty and eco-system, leaving behind sand bars visible only during low tide.

Where would the people go?

There are about 49,000 year round inhabitants of the Outer Banks. This number swells to 250,000 during the summer and beginning of hurricane season. The evacuations routes are simple – one way onto the islands, and one way off. Visitors are asked to familiarize themselves with the well marked routes when entering the Outer Banks. The state of North Carolina has a strict evacuation policy and requires that those who stay behind and refuse evacuation sign a notification form listing next of kin. This is enforced by public officials going door to door during an evacuation procedure.

In the case of category two hurricanes, millions of dollars of damage is incurred, in the case of a category five hurricane, North Carolina can expect nothing less than a complete rebuilding of the Outer Banks.