Hurricane Irene (U.S.)

Landfall | Summary
Posting Date: August 27, 2011, 11:30:00 AM

Current Conditions The eye of Hurricane Irene made landfall near Cape Lookout, North Carolina at about 7:30 am EDT, Saturday, August 27. As of the National Hurricane Center’s (NHC) 11:00 am advisory, Irene—now a Category 1 storm (down from Category 2 status yesterday)—is located about 80 miles west of Cape Hatteras, North Carolina. Irene is moving to the north-northeast at about 15 mph, and this forward motion is expected to continue over the next 24 hours. Maximum sustained winds are near 85 mph. Additional weakening is forecast as Irene traverses eastern North Carolina. Once the storm exits North Carolina and begins its way towards Long Island, it will enter an area of increased wind shear—possibly up to 30 knots. (To view current environmental conditions that affect tropical cyclone activity in the North Atlantic, visit AIR's ClimateCast.) This should prevent Irene from reintensifying; however the very large size of this system will likely prevent any very rapid weakening and Irene is expected to maintain hurricane status at least until second landfall on Long Island. As noted, Irene is still a very large storm. Hurricane force winds extend outward up to 90 miles from the center and tropical storm force winds extend outward to 260 miles. Hurricane warnings extend northward from North Carolina through RI and Cape Cod. Tropical storm warnings extend all the way to the border between Massachusetts and New Hampshire. Eastern North Carolina is currently experiencing battering winds and heavy rainfall. Instruments measured a sustained wind of near 60 mph and a gust of 84 mph at Cape Hatteras, 60 miles from the center of the storm at 8:00 am. Rainfall accumulations of 6 to 10 inches, with isolated amounts up to 15 inches, are expected. Storm surge of up to 9 feet above ground level in North Carolina level is likely to cause severe beach erosion and possibly structural damage to properties on the Outer Banks. Exposure at Risk The majority of single-family residential structures along the U.S. east coast are of wood-frame construction. At wind speeds associated with a strong Category 1 hurricane, these structures can experience damage to roof coverings and wall claddings. Failure of roof structures may occur in instances of improper fastening between the roof and building frame. Despite weakened wind speeds, Irene’s heavy rainfall accumulations could result in widespread damage to homes as a result of downed trees—a possibility exacerbated by the large geographic extent of the storm and, in some areas, by soils already saturated from previous heavy rainfall. It should be noted that the vulnerability of mobile (manufactured) homes and light metal structures is much greater than that of other construction types; these buildings could experience more significant damage. Engineered structures such as reinforced concrete and steel buildings should experience little wind damage, though there may be isolated instances of nonstructural damage, such as that to windows and roof coverings. Exposure in low-lying areas is subject to possibly significant damage as a result of storm surge. Reported Impacts Irene has caused the cancellation of hundreds of flights up and down the Eastern Seaboard. The New Jersey and New York transit systems are expected to shut down by noon today. Mandatory evacuations have been ordered in parts of North Carolina, Delaware, Maryland, New Jersey, and New York, including in lower Manhattan. About 370,000 residents in New York have been ordered to evacuate their homes. The mayor of New York City suspended bridge tolls out of the city to encourage compliance. President Obama has declared emergencies for North Carolina, Virginia, New Jersey, New York, Connecticut and Massachusetts. Even before Irene crossed the North Carolina coast, some 26,000 households were without power on Saturday morning. That number had risen to over 200,000 by 9:00 am. Residents and business-owners have been advised to expect, and prepare for, widespread power outages all along the East Coast and into western Connecticut and Massachusetts. The National Weather Service reported that rain is falling at the rate of 1 to 2 inches an hour in several counties along North Carolina’s Outer Banks and in counties inland from there. Officials in Hyde County, NC, have reported than the ocean has overrun State Highway 12 on Ocracoke Island. Highway 12 connects villages on the Outer Banks to the mainland. Forecast Track and Intensity The forecast track for Hurricane Irene is very close to the track as discussed yesterday. On this track, Irene is expected to exit the North Carolina coastline and be back over water just after 2 PM today. The forecast then brings the eye of the storm up and very close to the New Jersey coastline, and inland again on Long Island. The strongest winds will be in the northeast quadrant of the storm system. The latest indications suggest that Irene could maintain hurricane strength as far inland as Hartford, where it should arrive by mid-day on Sunday. Although Irene will encounter both cooler ocean temperatures and increased vertical wind shear as it travels northward, the sheer size of the storm is likely to prevent rapid weakening. It should be noted, however, that there is considerable uncertainty in both track and intensity forecasts. Of major concern is the storm surge that Irene could bring to New York and New England. Storm surge is forecast to raise water levels by as much as 4 to 8 feet above ground level from the North Carolina/Virginia border northward to Cape Cod. There is a chance that the surge could over-top lower Manhattan’s flood walls and enter the city’s subway system. Such a scenario could result in large business interruption losses. Other vulnerable low-lying areas in the state include Coney Island and Manhattan Beach in Brooklyn, where evacuations are still urgently taking place. Low-lying towns along the Connecticut coastline and Rhode Island’s Narragansett Bay and Massachusetts’ Buzzards Bay are also at risk. It should be noted that the degree and extent of storm surge along the most populated stretches of the coast are highly uncertain at this stage. Because Irene is such a large and persistent storm, surge levels could be higher than might be expected from Category 1 wind speeds. It should also be noted that insured losses will be highly sensitive to how surge levels ultimately materialize. With rainfall amounts of 6 to 10 inches expected across the region, flooding is another significant threat. River flood and flash flood watches and warnings have been issued for much of New England, as far north as northwest Maine. The heavy precipitation and Irene’s large wind field could also result in widespread damage from downed trees. The last time New England was significantly impacted by a hurricane was in 1991, when Hurricane Bob made landfall near Newport, Rhode Island as a Category 2 storm and tracked just east of Boston. If Hurricane Bob were to recur today, AIR estimates it would produce insured losses of about USD 2.4 billion. Irene is currently expected to track well west of Boston, possibly as a weak Category 1 hurricane, but more likely as a tropical storm. Again, it should be noted that the forecast for Hurricane Irene along the East Coast of the United States is still subject to potentially large errors in both track and intensity. Furthermore, due to Irene’s proximity to the US coastline, any deviation in its forecast path could change its landfall point and intensity, with significant implications for damage and loss. AIR continues to closely monitor Irene’s progress and will provide updates as warranted.

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Posting Date: August 27, 2011, 11:30:00 AM