32-Foot-Plus Waves From Hurricane Sandy Topple Records

By Andrew Freedman

Hurricane Sandy has already broken dozens of records, from the lowest air pressure reading ever recorded in the Northeast to the highest storm surge on record in Lower Manhattan. After reviewing wave height data, the National Weather Service office in Philadelphia has determined that the wave heights recorded at two buoys — including one monster 32.5-foot significant wave height at a buoy near the entrance to New York Harbor — set records for the largest waves seen in this region since such records began in 1975.

NASA visualization of the wind field associated with Hurricane Sandy as it approached the Mid-Atlantic coast on Oct. 28, 2012. This map was produced with data from a radar scatterometer on the Indian Space Research Organization’s (ISRO) Oceansat-2. Wind speeds above 40 mph are yellow; above 50 mph are orange; and above 60 mph are dark red.
Click to enlarge the image. Credit: NASA.

One of the buoys is located near the entrance to New York Harbor, about 15 nautical miles southeast of Breezy Point, N.Y., which sustained heavy damage from a merciless combination of coastal flooding and a fire that spread out of control. The harbor entrance buoy recorded a significant wave height of 32.5 feet at 8:50 pm on Oct. 29, beating the previous record set during Hurricane Irene by 6.5 feet! Records at that buoy extend only to 2008, which minimizes the historical significance of the record somewhat.

Significant wave height measures the average of the top third of the highest waves, which means that individual waves were actually higher than the 32.5-foot measurement.

The other buoy that set a significant wave height record is located 30 nautical miles south of Islip, Long Island, and during the evening of Oct. 29, the wave heights at that location built to a maximum height of 31 feet. That was the highest seen at that location since that buoy began operation in 1975, and exceeded the previous record of 30 feet, which was set during a fierce nor'easter on Dec. 11, 1992. 

“BASED ON THE THE INFORMATION PROVIDED . . . IT IS SAFE TO SAY THAT BOTH NATIONAL DATA BUOY LOCATIONS NEAREST SANDY HOOK . . . ACHIEVED A RECENT RECORD EXTREME SEA STATE ON TOP OF AND PROBABLY VERY CLOSE TO THE TIME OF THE RECORD STORM TIDE AT SANDY HOOK. ONE CAN INFER FROM THE DATA THAT THESE WAVE HEIGHTS WERE THE LARGEST SINCE RECORD KEEPING BEGAN IN THIS PORTION OF THE WESTERN ATLANTIC IN 1975,” the Weather Service said.

Hurricane Sandy, which made landfall as a post-tropical storm near Atlantic City on Oct. 30, had an extraordinarily expansive tropical storm-force wind field that extended nearly 1,000 miles from the center of the storm. That enabled it to churn the sea into a frenzy, building massive waves that battered the coastlines of New Jersey, New York, and Connecticut.

According to Jeff Masters of Weather Underground, since 1988, only one tropical storm and no hurricane has had a larger area of tropical storm-force winds. “Most incredibly, 10 hours before landfall (9:30 am EDT October 30), the total energy of Sandy's winds of tropical storm-force and higher peaked at 329 terajoules — the highest value for any Atlantic hurricane since at least 1969. This is 2.7 times higher than Katrina's peak energy, and is equivalent to five Hiroshima-sized atomic bombs,” Masters wrote on his blog. 

At The Battery in Lower Manhattan, the water level, driven by these strong winds, reached a record 13.88 feet above the average low tide level, which included a surge component of 9.23 feet. That set an all-time record for the location.

Sandy Hook, N.J., which is a spit of land that juts into the Atlantic pointing toward New York City from the extreme northeastern part of the state, also saw record coastal flooding during Sandy. The water level there rose to 13.31 feet above the average low tide level before the gauge malfunctioned. Or to put it another way, the water level at Sandy Hook rose to 8.1 feet above the average high-tide line.

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