Over the past 48 hours, Hurricane Sandy has been progressing largely as forecast, both in terms of track and intensity. Late Friday night, the storm had weakened to a tropical storm from high wind shear and dry air, but regained hurricane status by Saturday morning. As of the National Hurricane Center’s (NHC) 2 PM EDT advisory today, Hurricane Sandy is located 270 miles southeast of Cape Hatteras, NC, and 575 miles south of New York City and is moving to the northeast with a forward speed of 14 mph. Sandy packs maximum sustained winds of 75 mph (Category 1 on the Saffir-Simpson Scale) and is expected to maintain near hurricane strength up to its landfall on the U.S. east coast.
A sharp turn toward the west is expected on Monday as Sandy interacts with a mid-latitude trough approaching over the east coast, after which Sandy will begin transitioning into an extratropical system. The official NHC track forecast brings the center of the storm over the coast of New Jersey, near Atlantic City, late Monday night or early Tuesday morning. However, there is still considerable uncertainty as to when the westward turn will happen, which will have a significant impact on where along the coast Sandy will make landfall. The latest operational forecast model runs include landfall locations that span from Delaware north to Nova Scotia. The NHC’s cone of uncertainty (representing a 60% to 70% confidence interval) encompasses landfall locations from Maryland to the western end of Long Island, NY.
However, given the large size of the storm (tropical storm force winds extend some 530 miles from the center), a vast portion of the northeastern United States may experience damaging winds, coastal surge, and inland flooding. Further, after the storm completes its extratropical transition, its remnants could linger in the northeast for several days. The effects of Hurricane Sandy are thus likely to be felt well before and after landfall and could extend far beyond its landfall location.
A state of emergency has been declared in Delaware, New Jersey, Connecticut, New York, and Massachusetts. The governor of Delaware has ordered the mandatory evacuation of 50,000 coastal residents by this evening because of flood risk. The governor of New Jersey has ordered Atlantic City’s 12 casinos to close by 4 p.m. this afternoon, and mandatory evacuations are in place for towns along the coast (including Atlantic City) from Cape May through all of Long Beach Island. Other coastal evacuations are in place along the northeastern seaboard, including parts of Long Island, NY, and vulnerable, low-lying areas of Massachusetts.
In New York City, the Metropolitan Transportation Authority will begin suspending service at 7 p.m. tonight. The suspension will affect the subway and bus systems, the Metro-North Railroad, and the Long Island Railroad. Some service is expected to be restored 12 hours after the storm passes. Bridge travel in the metropolitan area will also be curtailed or suspended, depending on wind speeds.
Residents from Delaware to Maine have been urged to prepare for the storm’s impact by stocking supplies, boarding up windows, securing outdoor furniture, and staying indoors. Some 60,000 National Guard troops have been mobilized in preparation to assist local authorities, and hundreds of storm shelters have been set up across the region. Utility companies are preparing to deal with massive power outages, which are expected to be extensive and long-lasting in some areas. In total, an estimated 50 to 60 million people are expected to be affected by Hurricane Sandy, according to NOAA officials.
The majority of the coastline from North Carolina to southern Maine is likely to experience sustained winds in excess of 40 mph over the next several days. This is likely to cause extensive tree damage, which will damage buildings and trigger power outages. Direct wind damage to structures is expected to be primarily nonstructural in nature. The majority of single-family residential structures along the U.S. east coast are of wood-frame construction. At the forecast wind speeds, these structures may experience damage to roof coverings and wall claddings. 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 the possibility of significant damage as a result of storm surge. The arrival of the storm around the same time as the full moon will enhance the surge during high tide. Peak surge heights of 4 to 8 feet are expected in parts of the coast from North Carolina to Cape Cod. Depending on the tidal cycle, extreme coastal flooding is possible in some bays, as strong winds coming from the east will force water westward. East-facing bays like Long Island Sound, Raritan Bay, and New York City Harbor may experience near-record surge heights of up to 11 feet. Flood walls in Manhattan are five feet above mean sea level, indicating a good possibility that Sandy’s surge can inundate parts of the subway system.
Heavy rainfall accumulations of 4 to 8 inches are expected over much of the mid-Atlantic, with a maximum of 12 inches possible in isolated areas. The heaviest rains are expected on the south side of the storm. Fortunately, soil moisture and river levels are low to average over much of the region, which will moderate the possibility of catastrophic river flooding. This is in contrast to the heavily saturated soils at the time of Hurricane Irene’s arrival, which caused several billions of dollars of flood damage.
The AIR tropical cyclone team continues to monitor Sandy closely and will provide additional information on the development and impacts of this storm.Source:NHC