Parts of the southeastern United States were already experiencing dangerous swells and rip tides Thursday as Hurricane Irene exited the Bahamas. On Friday afternoon, ahead of Hurricane Irene’s forecasted arrival in North Carolina tomorrow, high waves and storm surge were beginning to impact the state’s Outer Banks, according to catastrophe modeling firm AIR Worldwide, which is tracking the storm and reported on its possible route and effects late Friday afternoon.
Dr. Tim Doggett, principal scientist at AIR Worldwide, said that the current forecast indicates Irene will likely hit North Carolina’s Outer Banks rather than bypassing them, and go on to make a second landfall on or near Long Island, New York. Virginia, Maryland, Delaware, New Jersey, Connecticut, Massachusetts, Rhode Island and Vermont are all in the vicinity of Irene’s projected path, meaning the major cities of New York, Philadelphia, Washington D.C. and Boston are projected to be affected by tropical storm conditions.
The National Hurricane Center (NHC) projection as of Friday afternoon indicated Irene will make its first landfall along the Outer Banks at around 2 p.m. Saturday, and another landfall somewhere between New Jersey and Cape Cod—with Long Island the most likely landfall location—around 2 p.m. Sunday afternoon. This timing could be good news for the New York / Long Island region as it corresponds with low tide, thus potentially mitigating storm surge levels, according to AIR.
Up to 50 million people from the Carolinas to New England could be affected by Irene.
Airlines began to cancel flights on Thursday, and hundreds of flights are likely to be cancelled through this weekend. Amtrak is cancelling train travel south of Washington, D.C. Operations at some oil refineries situated along the east coast in Virginia, Delaware, Pennsylvania and New Jersey—accounting for seven percent of the nation’s refining capability, according to the Energy Information Administration—are also expected to be shut down.
In North Carolina, roughly 200,000 tourists and local residents in three coastal counties have been ordered to evacuate. Both the governor, Beverly Perdue, and President Barack Obama, have declared states of emergency in North Carolina. States of emergency have also been declared in Maryland, Virginia, Delaware, New Jersey and New York. In parts of Delaware, Maryland and New Jersey, mandatory evacuations have been ordered. The mayor of New York said he could decide as early as Friday night whether to evacuate New Yorkers in low-lying areas, like Coney Island in Brooklyn.
Because Irene may strike the nation’s capital, federal officials postponed the dedication of the Martin Luther King Jr. memorial on the National Mall; it had been scheduled for Sunday. In New York City—which will likely be hit with tropical storm conditions, which include heavy rain and winds of 39 to 73 mph—the mass-transit system could shut down if Hurricane Irene arrives as is currently predicted (on Sunday). According to the Metropolitan Transportation Authority chairman, the safety of riders cannot be guaranteed if sustained winds reach above 39 miles per hour, and thus residents should prepare for interruptions in transit service.
To the north, in New England, the exact impact of the hurricane remains uncertain, though forecasters say to expect a “very significant and potentially damaging event” across the southern part of the region. Some areas are expected to get 5 to 10 inches of rain. Wind gusts could bring down trees, causing widespread extended power outages.
Irene has been downgraded from a major hurricane to Category 2 strength (with 105 mph winds). While some intensification is possible, Irene is not expected to achieve Category 3 status again. However, there is considerable uncertainty in both track and intensity forecasts.
“Irene is expected to weaken after passing North Carolina due to increased wind shear and cooler waters in the higher latitudes,” said. Doggett. “While it may maintain Category 2 strength as it tracks north to New Jersey, it is likely to be a rapidly weakening Category 1 hurricane at its second landfall, on Sunday. Scenarios that keep most of the storm’s footprint over water between North Carolina and New York show a longer period of sustained intensity, as the hurricane feeds off the Atlantic’s heat and moisture.”
Doggett said that in New England, the extent of Irene’s damage footprint is highly dependent on the storm’s track as it approaches this region. “If Irene cuts through Connecticut or Rhode Island, its stronger winds—on the right-hand side of the storm—will impact eastern Massachusetts. Forecast models which take Irene left of the NHC central track are considerably weaker than those to the right, owing to the interaction of the hurricane with land,” he said.
After exiting New England, Irene is expected to accelerate considerably, as is common for storms at this latitude; the storm may reach the Canadian border slightly after midnight Sunday.
Storm surge from Irene will raise water levels by as much as 11 feet along parts of the North Carolina coast and as by much as 8 feet in parts of the Chesapeake Bay. Locations well away from the coasts of North Carolina to New England could receive tropical storm-force winds (39-73 miles per hour) and 5 to 10 inches of rain; because much of this area is already saturated from downpours earlier this year, residents were warned to expect heavy flooding.
As high coastal winds and severe flooding are possible all the way from North Carolina north to New England, the current forecast track for Irene is not good news. A similar and notable hurricane was 1985’s Hurricane Gloria, which affected the New York, New Jersey and the New England states. Gloria struck Cape Hatteras with 105 mph winds, Long Island, New York, with winds of about 90 mph, and the coast of Connecticut with roughly 80 mph winds. AIR estimates that Gloria would produce about $2.5 billion in insured losses if it were to recur today. When Gloria was impacting Long Island, it was a bit smaller than Irene is today. Often, hurricane wind fields will expand as they track through the middle latitudes, so Irene’s footprint could be considerably wider than Gloria’s.
“Again, it should be noted that the long term forecast along northeastern U.S. states is subject to potentially large errors in both track and intensity,” said Doggett. “Furthermore, due to Irene’s proximity to the U.S. coastline, any deviation in its forecast path could change its landfall point and intensity, with significant implications for damage and loss.”
According to AIR, the majority of single-family residential structures along the U.S. east coast are of wood-frame construction. At Category 2 wind speeds, these structures can experience significant damage to the roof, roof covering and wall cladding. Failure of roof structures often occurs because of improper fastening between the roof sheathing and building frame. At Category 2 wind speeds there may also be numerous cases of damage due to downed trees—a possibility exacerbated by soils already saturated from recent heavy rainfall.
Mobile or manufactured homes and light metal structures are much more vulnerable than other construction types; these buildings could experience structural damage, AIR said. Engineered structures such as reinforced concrete and steel buildings should experience less damage compared to wood-frame and masonry structures; they may exhibit isolated instances of nonstructural damage, such as that to windows and roof coverings.
Recent damage data analyses have indicated that building vulnerability can change significantly over time due to changes in building code and code enforcement, changes in material and construction practices, and structural aging. North Carolina has a long history of evolving building codes. AIR said it expects newer structures in the region will perform better than older structures.