Future Hurricane Could Loop Around and Make Landfall Twice in the U.S., Causing Catastrophic Flooding and Storm Surges

A future hurricane that loops around and makes landfall twice in the northeastern United States could cause severe flooding and storm surges in a "vulnerable" area of New England, according to modeling simulations.

In a study published in Geosciences, a team of scientists simulated a hypothetical but physically plausible storm dubbed "Hurricane Rhody" that slows down after making landfall in New England, makes a loop and returns for a second landfall two days later. The simulation was partly based on Hurricane Ester—which made a similar loop near New England in 1961, but never made landfall—and other storms that have affected the region.

The research was funded by the U.S. Department of Homeland Security and aimed to investigate the potential effects of extreme hurricanes on the coast of southern New England in order to help agencies such as the Federal Emergency Management Agency (FEMA) and the U.S. Coast Guard to better prepare coastal communities for future risks.

The area is especially vulnerable to inland flooding because its rivers are relatively short and shallow, and therefore more likely to produce high discharge during heavy rain. In fact, the region is considered so vulnerable to these powerful storms that FEMA has previously dubbed it the "Achilles' heel of the Northeast."

"Thus, it is important for preparedness planners to be aware of the potential impacts of intense hurricanes on the infrastructure of the region so that evacuation and response plans can be developed," the authors wrote in the study.

The region has experienced several extreme hurricanes since the arrival of European settlers. However, there have been none in recent times, leaving it relatively unprepared for a major storm.

One of the issues that the scientists researched is the growing tendency of hurricanes to "stall" along the North American coast, hovering above a confined region for many hours—as occurred with Harvey, Florence and, most recently, Dorian. Previous research has shown that the average speed of tropical cyclones has slowed since the mid-20th century.

Hurricane stalling is concerning because it can lead to increased rainfall over a given area—causing rivers to overflow and flood—while exacerbating coastal storm surges and the damage caused by strong winds.

At present, it is not clear what is causing hurricanes to stall. Climate change is a possible factor. However, the research in this area is not as definitive as the evidence linking climate change to an increase in hurricane intensity and quantity of rainfall produced.

In the worst case scenario of three simulations tested in the Geosciences study, Rhody approached New England with a forward speed of approximately 45 miles per hour and a maximum wind speed of 130 miles per hour at landfall, making it a Category 4 storm on the Saffir-Simpson Hurricane Wind Scale. After landfall, the storm slowed considerably, moving gradually to the south and making the loop that would eventually bring a second landfall. The simulation showed that this scenario would bring severe flooding and storm surges to the region.

"Because the aim of the study was to raise local awareness of the potentially catastrophic impacts of a major hurricane strike in southern New England, the start time of the Rhody simulation was selected such that the first landfall would occur at the time of astronomical high tide," Isaac Ginis of the University of Rhode Island, who was one of the authors of the study, told Newsweek.

"As a result, the maximum storm surge in the Narragansett Bay reached 7 meters [around 23 feet] causing extensive overland flooding in many areas along the coast. The intense rainfall—up to 20 inches—during the second landfall produced severe inland flooding throughout the state of Rhode Island," he said.

These results have significant implications for emergency management plans in the area, according to the researchers. In 1966, authorities constructed the Fox Point Hurricane Barrier to protect the city of Providence, Rhode Island, from storm surges following the extensive damage caused by two major destructive hurricanes—the Great New England Hurricane of 1938 and Hurricane Carol in 1954—which both made landfall to the west of Narragansett Bay.

In the worst-case Rhody scenario, the simulation indicated that if the barrier remains closed and its pumps fail—because of a power outage or equipment failure, for example—severe flooding would occur to the north. This highlights he vulnerability of northern Narragansett Bay to storm surges and rainfall-driven flooding, the researchers say.

"The important result of this simulation is that the closing of the hurricane barrier led to catastrophic flooding two days later of up to 5 to 6 meters from rainfall and river run-off," Ginis said. "After discussions with Rhode Island emergency managers, it appears the large-scale power outages expected in a severe hurricane will preclude the opening of the barrier."

Ginis said the discharge of the Woonasquatucket and Moshassuck rivers caused elevated waters over 6 meters north of the closed barrier. "These results emphasized the need to ensure that, after a hurricane strike, either the barrier can be opened or the barrier's pumps can be operated to discharge the river inflow across the barrier," he said.

The team's research is already being put to use in the real world. The Rhode Island Emergency Management Agency and FEMA recently conducted a four-day, statewide preparedness exercise attended by more than 150 emergency managers and other decision-makers from all levels of government, solely based on the Hurricane Rhody simulations. According to the scientists, this is the first time that a computer-simulated hurricane scenario has been used for emergency response training.

"Typically, emergency management agencies develop hurricane preparedness and response plans based on historic hurricanes," Ginis said. "But as we have seen in recent storms, such as Hurricane Harvey in 2017 that produced enormous rainfall, a hurricane may do damage through means that are not anticipated by the public and emergency managers and may be very different from previously experienced storms."

Ginis said the Rhode Island area is overdue for another big hurricane, given that the last major one took place in 1954, although the impacts will likely differ from storms that have affected the area in the past.

"The historic hurricanes that affected New England passed through the region relatively fast," he said. "But the increased frequency in hurricane stalling and the associated increase in rainfall will most likely produce in the future the impacts through means very different from previously experienced storms. Our research shows that high-resolution modeling can be used to simulate hurricane scenarios that are not anticipated by the public and emergency managers and help better prepare for future storms."

The researchers did not work out the probability of a Hurricane Rhody scenario occurring. A looping hurricane track like the one made by Rhody is quite rare in the Atlantic ocean—it's more common in the Pacific Ocean. But its main features such as slowing down after the landfall and excessive rainfall are expected to occur more often in the future, according to Ginis.

"Hurricane Rhody represents close to the worst-case scenario for Rhode Island with multiple threats that the emergency agencies need to prepare for and manage with limited resources," he said.

hurricane flooding
Man paddles a boat in floodwaters caused by Hurricane Florence in front of Trinity United Methodist Church near the Crabtree Swamp on September 26, 2018, in Conway, South Carolina. Sean Rayford/Getty Images
Future Hurricane Could Loop Around and Make Landfall Twice in the U.S., Causing Catastrophic Flooding and Storm Surges | Tech & Science