Superstorm Sandy, 11 years later: How it became the unique system that ravaged Long Island, region

Superstorm Sandy started as a ripple on Oct. 11, 2012, when a wave of low pressure in the easterly trades left the west coast of Africa and moved west over the Atlantic toward the Caribbean. When it later merged with two other weather systems, it become one of the most powerful and unusual storms to ever hit Long Island.

Early development was slow, but by Oct. 20, falling pressures and reduced wind shear over the Caribbean began to yield conditions more conducive to the birth of the tropical storm Sandy would become.

Wind speed started at 28 mph, though in coming days it would accelerate to an estimated high of 115 mph before slowing. 

By Oct. 24, centered off Kingston, Jamaica, Hurricane Sandy had been born. It grew immense, generating storm-force winds across an area a fifth the size of the continental United States. On Oct. 29, a Monday, it made landfall in New Jersey as a post-tropical cyclone, the name given to hurricanes that have lost their tropical characteristics. And from there it would take aim at Long Island. 

Sandy's strike here was indirect, but the consequences were catastrophic.

Across two counties, it killed at least 13 people and destroyed or damaged 100,000 homes. The storm submerged miles of shoreline. According to a 2019 Suffolk County report, it ruined 100,000 automobiles and produced 2.5 million cubic yards of waste, from snapped trees to hazardous household substances — so much material that it took workers about a year and a half to clear it. 

An unusual storm

Part of what made Sandy so rare was the track it took when it approached the New York region.

The storm's westward turn toward the East Coast was "highly unusual," said Anthony Broccoli, distinguished professor of atmospheric science at Rutgers University.

Reviewing tracks for dozens of recorded storms near Atlantic City, near where Sandy made landfall, he found only one that was similar to Sandy’s, for a storm that passed through the area about a century ago.

Also unusual were the system’s size and low pressure, which can factor into intensity. Some government monitoring agencies said Sandy had the lowest sea-level pressure ever recorded north of North Carolina in the United States. A National Ocean Service station at Atlantic City recorded 945.5 millibars. A typical reading is 1013.25 millibars.

As Broccoli’s search of storm tracks suggested, the precise combination of factors that created Sandy’s track may be rare, though he noted “the way atmosphere works, just because something hasn’t happened in a long time doesn’t guarantee it will be a long time before it happens again.” 

Unfortunately for Long Island, it may not need to. Rising sea levels mean that in coming years “it may not take a storm as strong as Sandy or on as unusual a track as Sandy to produce the same kind of flooding,” Broccoli said.

This account of the storm’s life cycle is drawn primarily from expert interviews, a 2013 report by the National Oceanic and Atmospheric Administration’s National Hurricane Center and Adam Sobel’s 2014 book “Storm Surge: Hurricane Sandy, Our Changing Climate, and Extreme Weather of the Past and Future.”

Sandy developed from a confluence of factors. These included winds rotating around an area of low pressure while warm sea surface temperatures and hot, humid air provided energy for the storm.  

There was also very little wind shear in the system, or shifts in wind direction and speed at different altitudes that can tear a developing storm apart. And that allowed it to keep growing. 

Thousands of miles north and miles above the Earth’s surface, conditions also were being primed. A periodic ripple in the high-altitude jet stream called the North Atlantic Oscillation was moving an area of low pressure “trough” over the eastern United States, and an area of high pressure “ridge” south of Greenland. In coming days, the trough would guide Sandy north and west and the ridge would block it from moving offshore. 

On Oct. 25, Sandy made landfall in Cuba as a Category 3 hurricane, weakening as it moved north to the Bahamas. Tropical cyclones often lose power at landfall because they are separated from the warm ocean waters that fuel them. But landfall also made the storm grow; in coming days its radius of maximum winds would extend hundreds of miles. 

“While the core was over Cuba, the outer spiral bands were still over water,” said meteorologist Jeff Masters, co-founder of the forecast site Weather Underground and a blogger for Yale Climate Connections. “The outer portions of the storm tend to invigorate because the warm ocean waters can no longer feed the core. Once the center moved back over water, Sandy now had this area of larger heavy thunderstorm activity that enabled it to be a bigger storm.” 

Power from weather systems joining 

As Sandy moved into the Bahamas, it was still in the tropics but began to exhibit signs of changing structure and mechanics as it interacted with a separate low-pressure cyclone moving at high altitude from the west. 

The introduction of this second cyclone temporarily weakened Sandy by introducing wind shear and dry, cold air that impeded its ability to gather energy. But as these two cyclones joined, the resulting hybrid’s strong winds covered a larger area than Sandy had after the Cuba interaction, while maintaining a warm core of convection-created energy at its center. 

On Oct. 27, Sandy was off the Carolinas. After the first interaction, Sandy was only a Category 1 hurricane, but it remained vast, with a 520-mile radius big enough to hold several smaller hurricanes and abnormally low pressure signaling its destructive potential.

National Weather Service advisories warned that “gale-force” winds would reach the area by Monday morning, with a 4- to 8-foot storm surge on Long Island Sound.

On Oct. 29, Sandy, passing Cape Hatteras, encountered an area of high pressure that prevented the cyclone from moving out to sea. The storm had strengthened as it passed over the warmer waters of the Gulf Stream. At 8 a.m., the storm reached wind speeds of about 98 mph, 220 miles southeast of Atlantic City.

Meanwhile, a second and larger area of low pressure moving from the Great Lakes into the southeastern United States produced what Sobel, a Columbia University professor of applied physics, math and earth and environmental sciences, called “the final extratropical transition.” This cold air didn’t immediately kill Sandy’s central convection; rather, it became a second power source, providing what Sobel wrote was a “jolt of energy” before landfall. 

“You have this storm turning at the same time as low pressure in the upper atmosphere was bringing cold air to where it could influence Sandy,” Broccoli said. The cold air infusion created a front, the denser cooler air pushing the warmer air up.

“Instead of weakening when it lost the warmth of a tropical ocean, Sandy maintained its strength and, by some measures, strengthened, because now it was drawing energy from the contrast between colder and warmer air,” Broccoli added. 

News 12 Long Island meteorologist Rich Von Ohlen likened the meeting of the systems to a “head-on collision” of two bowling balls, sending Sandy careening inland. 

The storm made landfall near Brigantine, New Jersey, just northeast of Atlantic City, with wind speeds of about 81 mph. But the new power source meant Sandy’s wind field was more distributed than it would have been if the storm had made landfall as a conventional tropical cyclone, with high winds concentrated at the eyewall, impacting not just the New Jersey coast, but also New York City, Long Island and New England.   

The storm’s counterclockwise flow and its turn to the west meant that, at impact, "The winds are blowing in the same direction as the storm is moving,” Broccoli said. “Those winds were pushing water into the coastline of New York and New Jersey. It was like pushing water into a corner.” 

Sandy caused water levels to rise along the East Coast from Florida to Maine, but on Long Island the storm surge was particularly intense: 12.65 feet above normal tide levels at Kings Point, on the western end of Long Island Sound, and from 3 to more than 5 feet at locations on the South Shore, resulting in 3 to 6 feet of inundation along the low-lying coast. 

Powerful waves there accompanied the surge, which occurred at a time when the normal astronomical tides were already high. “There was nothing from anywhere that could have helped us out,” Von Ohlen said. “We had three tide cycles where that wind was at least gale-force or more.” 

Superstorms in the future?

Whether the precise circumstances that aligned to create the first Sandy will make a second or third such superstorm is difficult to predict, experts say. But some major storms, like Hurricane Otis that struck Acapulco this week, seem to be intensifying faster, fueled by warmer seas. And, experts say, some of the baseline conditions that make Long Island vulnerable are getting worse. 

Sea levels along New York's coast and in the Hudson River already have risen more than a foot since 1900. That rise is projected to continue and accelerate. Using 2000 sea levels as a baseline, 2014 updates to New York State’s ClimAID report — commissioned to assess climate change impacts and adaptive strategies — projects sea level rise of 4 to 8 inches in the 2020s, 11 to 21 inches in the 2050s and 21 to 50 inches by 2100. The rise is driven by increasing temperatures that cause ocean water to expand, though melting ice also contributes. 

If those projections are borne out, even a modest surge from a typical winter storm could cause major flooding, said Nelson Vaz, warning coordination meteorologist at the National Weather Service’s New York office. 

The local weather impacts of a hotter, more energized climate are not yet fully understood — some research suggests the area will experience fewer storms — “but a higher percentage of those could be stronger hurricanes and stronger Nor’easters,” Vaz said.

“Warmer atmosphere, warmer water, greater temperature gradients and more water in the atmosphere can create heavier precipitation events, and warm water temperatures allow more thunderstorm activity, intensifying tropical systems.”