Photograph by Mario Tama, Getty Images
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Homes in Seaside Heights, New Jersey sit in ruins on the Atlantic Ocean waterfront after being destroyed by Hurricane Sandy on October 31, 2012. At least 147 people were reportedly killed by Sandy, and New Jersey suffered massive damage and power outages.

Photograph by Mario Tama, Getty Images

Hurricane Sandy, explained

Superstorm Sandy was actually several storms wrapped together, which made it one of the most damaging hurricanes ever to make landfall in the U.S.

A “raging freak of nature” is how National Geographic described Hurricane Sandy when it hit land in fall 2012.

From beginning to end, Hurricane Sandy's progression caused deadly flooding, mudslides, and destructive winds from the Caribbean to the U.S. East Coast. An unusual combination of hurricane conditions and cold fronts made Sandy particularly potent. In the nine days that Sandy raged, it killed 70 people in the Caribbean and almost 150 people in the U.S.

The National Oceanic and Atmospheric Administration estimates Sandy caused at least $70 billion in damages, making it among the costliest storms in U.S. history.

Though Sandy is often described as an anomaly, for many it was a call to action. The disaster showed how vulnerable wider areas of the United States are to extreme weather events, particularly in a time when scientists warn that climate change is threatening sea-level rise and hotter temperatures. Since the storm, affected regions have rethought their disaster plans to try and increase their preparedness.

How did Sandy form?

On October 22, 2012, a tropical depression formed off the northeast coast of Nicaragua in the Caribbean Sea. Two days later, it strengthened and officially became a Category 1 hurricane as it moved northeast. Hurricane Sandy passed over Jamaica, the Dominican Republic, and Haiti.

It pummeled Haiti with rain, setting off a torrent of mudslides that killed at least 50 people. By October 26, it had passed over Puerto Rico and Cuba, damaging the historic city of Santiago de Cuba.

Over the next few days, Hurricane Sandy continued north. It weakened to a tropical depression once reaching the Bahamas on October 27, but then it quickly restrengthened into a Category 1 hurricane. NOAA reports that this reformed structure was unusual and was spurred by warm waters. The tempest became huge, with a radius that stretched 100 miles.

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The wide-reaching storm progressed up the U.S. East Coast. It stayed several hundred miles offshore when passing the Carolinas, but it still pushed large waves and massive amounts of rain ashore. Roads were washed away in the Outer Banks.

Sandy moved past Delaware and New Jersey, unleashing more havoc as it collided with a cold front heading east toward the Atlantic. A separate high-pressure storm to the north of Sandy prevented it from moving away from shore, effectively trapping the now combined storm systems along the coast. Sandy's winds now extended 1,000 miles along the coast.

Because it became a hybrid of two storm systems and grew to be so immense, the press dubbed Sandy a Frankenstorm at the time.

A full moon added to the deadly storm surge that resulted, which increased the tide pushed ashore by a foot.

As the tropical storm system mixed with cooler air, it lost its hurricane structure but retained its intense winds. It was ultimately dubbed a superstorm, an unofficial designation given to large storms that don't easily fit into a single classification.

As the superstorm hit the coasts of New Jersey and New York, it packed a wallop. Parts of New York City near lower Manhattan, Brooklyn, and Staten Island flooded, temporarily paralyzing the city's subway system. As it progressed Sandy dropped a deluge of snow in the Appalachian Mountains in Virginia, West Virginia, and North Carolina.

Over 8 million people lost power during the story, and outages were seen for days in some major cities, while outlying areas were without power for weeks. Power outages from Sandy were experienced as far west as Michigan.

On October 30, the storm began to weaken as it moved inland before finally dissipating the next day over Pennsylvania. Even as the remains of Sandy moved west of Pittsburgh, the tempest's immense size continued to push storm surges toward New York and cause additional flooding. At its maximum size the storm covered a quarter of the continental U.S.

Sandy's aftermath

Two years after Sandy, experts broke down why the storm was so deadly. All but one European weather model had predicted the storm would turn and travel out to sea instead of striking the U.S. Just before the storm hit, the National Hurricane Center put local weather offices in charge of issuing advisories. Many people chose not to evacuate.

Many homes along the East Coast were destroyed, with parts of the Jersey Shore and Staten Island particularly impacted. As long as five years after, some residents were still rebuilding, with many relocating to higher ground. Thousands of people were temporarily left homeless, and more than 20,000 households were displaced a year after the storm hit.

Though the storm itself wasn't as strong as other infamous hurricanes, a combination of weather factors and the fact that much of the region was unprepared for it contributed to high levels of damage.

Sandy is considered the fourth most expensive storm in U.S. history, and more than 600,000 housing units were destroyed in New Jersey and New York. The government of New York City estimates that $19 billion in damage was inflicted on the city alone. Five years after Sandy, more than a thousand New Jersey residents reported still being unable to return home.

A report published by the city of New York outlines where the region was vulnerable to a storm the size of Sandy. It found that while some infrastructure like flood walls was out-of-date, the city also did not have sufficient plans in place to deal with the disaster. Most businesses and homeowners in New York City did not have flood insurance, having never suspected a storm the size of Sandy could reach so far north.

As a result, Hurricane Sandy served as a wakeup call for many in the region.

In addition to providing state funding to help struggling people rebuild their homes, New York and New Jersey also invested in rebuilding their outdated infrastructure meant to prevent flooding. Even in 2019, some East Coast cities are still pushing for additional funding to rebuild dunes and barriers destroyed by Sandy.

New York Governor Andrew Cuomo said at the time that his state's infrastructure needed to be rethought, not just rebuilt. Climate experts predict that extreme weather events like Sandy will become more common as the planet warms, warning that leaders need to both prepare for a more uncertain world and work to reduce emissions of heat-trapping greenhouse gases.