Superstorm Sandy

Hurricane Sandy (unofficially referred to as ''Superstorm Sandy'') was an extremely destructive and strong Atlantic hurricane, as well as the largest Atlantic hurricane on record as measured by diameter, with tropical-storm-force winds spanning . The storm inflicted nearly $70 billion (2012 USD) in damage and killed 233 people across eight countries from the Caribbean to Canada. The eighteenth named storm, tenth hurricane, and second major hurricane of the 2012 Atlantic hurricane season, Sandy was a Category 3 storm at its peak intensity when it made landfall in Cuba, though most of the damage it caused was after it became a Category 1-equivalent extratropical cyclone off the coast of the Northeastern United States.

Sandy developed from a tropical wave in the western Caribbean Sea on October 22, quickly strengthened, and was upgraded to Tropical Storm Sandy six hours later. Sandy moved slowly northward toward the Greater Antilles and gradually intensified. On October 24, Sandy became a hurricane, made landfall near Kingston, Jamaica, re-emerged a few hours later into the Caribbean Sea and strengthened into a Category 2 hurricane. On October 25, Sandy hit Cuba as a Category 3 hurricane, then weakened to a Category 1 hurricane. Early on October 26, Sandy moved through the Bahamas. On October 27, Sandy briefly weakened to a tropical storm and then restrengthened to a Category 1 hurricane. Early on October 29, Sandy curved west-northwest (the "left turn" or "left hook") and then moved ashore near Brigantine, New Jersey, as a post-tropical cyclone with hurricane-force winds. Sandy continued drifting inland for another few days while gradually weakening, until it was absorbed by another approaching extratropical storm on November 2.

In Jamaica, winds left 70 percent of residents without electricity, blew roofs off buildings, killed one person, and caused about $100 million (2012 USD) in damage. Sandy's outer bands brought flooding to Haiti, killing at least 54, causing food shortages, and leaving about 200,000 homeless; the hurricane also caused two deaths in the Dominican Republic. In Puerto Rico, one man was swept away by a swollen river. In Cuba, there was extensive coastal flooding and wind damage inland, destroying some 15,000 homes, killing 11, and causing $2 billion (2012 USD) in damage. Sandy caused two deaths and an estimated $700 million (2012 USD) in damage in The Bahamas.

In the United States, Hurricane Sandy affected 24 states, including the entire eastern seaboard from Florida to Maine and west across the Appalachian Mountains to Michigan and Wisconsin, with particularly severe damage in New Jersey and New York. Its storm surge hit New York City on October 29, flooding streets, tunnels and subway lines and cutting power in and around the city. Damage in the United States amounted to $65 billion (2012 USD). In Canada, two were killed in Ontario, and the storm caused an estimated $100 million (2012 CAD) in damage throughout Ontario and Quebec.

Meteorological history

Hurricane Sandy began as a low pressure system which developed sufficient organized convection to be classified as Tropical Depression Eighteen on October 22 south of Kingston, Jamaica. It moved slowly at first due to a ridge to the north. Low wind shear and warm waters allowed for strengthening, and the system was named Tropical Storm Sandy late on October 22. Early on October 24, an eye began developing, and it was moving steadily northward due to an approaching trough. Later that day, the National Hurricane Center (NHC) upgraded Sandy to hurricane status about south of Kingston, Jamaica. At about 1900 UTC that day, Sandy made landfall near Kingston with winds of about 85 mph (140 km/h). Just offshore Cuba, Sandy rapidly intensified to a Category 3 hurricane, with sustained winds at 115 mph (185 km/h) and a minimum central pressure of , and at that intensity, Sandy made landfall just west of Santiago de Cuba at 0525 UTC on October 25. Operationally, Sandy was assessed to have peaked as a high-end Category 2 hurricane, with maximum sustained winds of 110 mph (175 km/h).

After Sandy exited Cuba, the structure of the storm became disorganized, and it turned to the north-northwest over the Bahamas. By October 27, Sandy was no longer fully tropical, as evidenced by the development of frontal structures in its outer circulation. Despite strong shear, Sandy maintained its convection due to influence from an approaching trough; the same that turned the hurricane to the northeast. After briefly weakening to a tropical storm, Sandy re-intensified into a Category 1 hurricane, and on October 28, an eye began redeveloping. The storm moved around an upper-level low over the eastern United States and also to the southwest of a ridge over Atlantic Canada, turning it to the northwest.

Sandy briefly re-intensified to Category 2 intensity on the morning of October 29, around which time it had become an extremely large hurricane, with a record gale-force wind diameter of over 1,150 miles (1,850 km), and an unusually low central barometric pressure of 940 mbar, possibly due to the very large size of the system. This pressure set records for many cities across the Northeastern United States for the lowest pressures ever observed. The convection diminished while the hurricane accelerated toward the New Jersey coast, and the cyclone was no longer tropical by 2100 UTC on October 29. About 2½ hours later, Sandy made landfall near Brigantine, New Jersey, with sustained winds of 80 mph (130 km/h). During the next four days, Sandy's remnants drifted northward and then northeastward over Ontario, before merging with another low pressure area over Eastern Canada on November 2.

Forecasts

On October 23, 2012, the path of Hurricane Sandy was correctly predicted by the European Centre for Medium-Range Weather Forecasts (ECMWF) headquartered in Reading, England nearly eight days in advance of its striking the American East Coast. The computer model noted that the storm would turn west towards land and strike the New York/New Jersey region on October 29, rather than turn east and head out to the open Atlantic as most hurricanes in this position do. By October 27, four days after the ECMWF made its prediction, the National Weather Service and National Hurricane Center confirmed the path of the hurricane predicted by the European model. The National Weather Service was criticized for not employing its higher-resolution forecast models the way that its European counterpart did. A hardware and software upgrade completed at the end of 2013 enabled the weather service to make predictions more accurate and farther in advance than the technology in 2012 had allowed.

Relation to global warming

According to NCAR senior climatologist Kevin E. Trenberth, "The answer to the oft-asked question of whether an event is caused by climate change is that it is the wrong question. All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be." Although NOAA meteorologist Martin Hoerling attributes Sandy to "little more than the coincidental alignment of a tropical storm with an extratropical storm", Trenberth does agree that the storm was caused by "natural variability" but adds that it was "enhanced by global warming". One factor contributing to the storm's strength was abnormally warm sea surface temperatures offshore the East Coast of the United States—more than above normal, to which global warming had contributed . As the temperature of the atmosphere increases, the capacity to hold water increases, leading to stronger storms and higher rainfall amounts.

As they move north, Atlantic hurricanes typically are forced east and out to sea by the Prevailing Westerlies. In Sandy's case, this typical pattern was blocked by a ridge of high pressure over Greenland resulting in a negative North Atlantic Oscillation, forming a kink in the jet stream, causing it to double back on itself off the East Coast. Sandy was caught up in this southeasterly flow, taking the storm on an unusual northwest path. The blocking pattern over Greenland also stalled an Arctic front which combined with the cyclone. Mark Fischetti of ''Scientific American'' said that the jet stream's unusual shape was caused by the melting of Arctic ice. Trenberth said that while a negative North Atlantic Oscillation and a blocking anticyclone were in place, the null hypothesis remained that this was just the natural variability of weather. Sea level at New York and along the New Jersey coast has increased by nearly a foot (300 mm) over the last hundred years, which contributed to the storm surge. One group of scientists estimated that the anthropogenic (human activity-driven) climate change was responsible for approximately 9 cm of sea level rise in New York, which permitted additional storm surge that caused approximately US$8.1B out of the $60 billion in reported economic damage and to an extension of the flood zone to impact approximately 71,000 more people than would have been the case without it. Harvard geologist Daniel P. Schrag calls Hurricane Sandy's 13-foot (4 m) storm surge an example of what will, by mid-century, be the "new norm on the Eastern seaboard".

Preparations

Caribbean and Bermuda

After the storm became a tropical cyclone on October 22, the Government of Jamaica issued a tropical storm watch for the entire island. Early on October 23, the watch was replaced with a tropical storm warning and a hurricane watch was issued. At 1500 UTC, the hurricane watch was upgraded to a hurricane warning, while the tropical storm warning was discontinued. In preparation of the storm, many residents stocked up on supplies and reinforced roofing material. Acting Prime Minister Peter Phillips urged people to take this storm seriously, and also to take care of their neighbors, especially the elderly, children, and disabled. Government officials shut down schools, government buildings, and the airport in Kingston on the day prior to the arrival of Sandy. Meanwhile, numerous and early curfews were put in place to protect residents, properties, and to prevent crime. Shortly after Jamaica issued its first watch on October 22, the Government of Haiti issued a tropical storm watch for Haiti. By late October 23, it was modified to a tropical storm warning.

The Government of Cuba posted a hurricane watch for the Cuban Provinces of Camagüey, Granma, Guantánamo, Holguín, Las Tunas, and Santiago de Cuba at 1500 UTC on October 23. Only three hours later, the hurricane watch was switched to a hurricane warning. The Government of the Bahamas, at 1500 UTC on October 23, issued a tropical storm watch for several Bahamian islands, including the Acklins, Cat Island, Crooked Island, Exuma, Inagua, Long Cay, Long Island, Mayaguana, Ragged Island, Rum Cay, and San Salvador Island. Later that day, another tropical storm watch was issued for Abaco Islands, Andros Island, the Berry Islands, Bimini, Eleuthera, Grand Bahama, and New Providence. By early on October 24, the tropical storm watch for Cat Island, Exuma, Long Island, Rum Cay, and San Salvador was upgraded to a tropical storm warning.

At 1515 UTC on October 26, the Bermuda Weather Service issued a tropical storm watch for Bermuda, reflecting the enormous size of the storm and the anticipated wide-reaching impacts.

United States

Much of the East Coast of the United States, in Mid-Atlantic and New England regions, had a good chance of receiving gale