Hurricane Sandy, a.k.a. “Frankenstorm”
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Frankenstorm
Born in the tropical waters of the Caribbean Sea on October 22, tropical storm “Sandy” gave little early indication of the death and destruction it would cause just a week later. As the storm churned ominously up the Atlantic Coast in the days before Halloween, some weather trackers began calling Hurricane Sandy “Frankenstorm,” because this hurricane looked particularly scary, even monstrous. Days before it made landfall Monday night, meteorologists warned Sandy might be even more destructive than the infamous “perfect storm” that hammered New England in 1991. That storm became the subject of the popular book and disaster movie of the same name.
There were good reasons to be worried about Frankenstorm, a.k.a. “Perfect Storm II.” For starters, Sandy was taking aim at the much more densely populated New York/New Jersey region. In addition, satellite images showed the storm was unusually broad. Although its sustained winds were clocked at “only” 90 miles per hour, the hurricane’s huge rainbands sprawled out nearly 500 miles from its center as it took aim at the coast. But satellites spotted something else that made the situation even more frightful. Sandy was about to collide head-on with a powerful wintry storm system marching eastward across the United States. On top of that, a strong blast of bitter cold air was plunging south from the Arctic. The merger of all three powerful air masses soon created a hybrid “superstorm” with mind-boggling damage potential.
An Unexpected Track
Most hurricanes that churn up the Atlantic Coast eventually (between 30 and 60 degrees N latitude) are steered by prevailing westerly winds and veer to the northeast, away from land. But Sandy chugged to the north then suddenly twisted towards the Atlantic Coast. Why? A massive wall of high pressure known as a “blocking high” was unluckily parked out in the North Atlantic south of Greenland. Though not uncommon, it was an unusually intense one for this time of year. Like a huge invisible rock in the sky, the stubborn high pressure area kept the westerlies from pushing Sandy out to sea and helped nudge it in the opposite direction, as shown in this NASA time-lapse image. Sustained winds of 60+ mph lashed the coast.
A high pressure system to the northeast prevented Sandy from tracking in that direction, as hurricanes usually do at this time of year. Instead, the enormous cyclone turned toward the Jersey Shore. (Credit: ISRO/NASA/JPL-Caltech)
Full Moon Storm Surge
A hurricane’s fierce winds and low pressure whip up ocean (or lake) water into what’s called a storm surge (Technically, a storm surge is the water’s height above the normal tide level). It didn’t help that its arrival was timed perfectly for the full moon, when tides are at their monthly peak. For example, some shoreline areas in the Mid-Atlantic states normally have a tidal range (the difference between low tide and high tide) of 2–3 feet during half moons. However, during full (and new) moons, the tidal range can reach 5–6 feet. Storm surges of over 10 feet were predicted for some areas, which would increase the height of incoming water by 15-16 feet during a full moon.
Sandy’s timing couldn’t have been worse. The storm pummeled the coastline at two different high tides that were already enhanced by the full moon.
As Sandy hit, the worst-case scenarios unfolded in New York and New Jersey. In New York City, a 9-foot storm surge arriving at high tide brought water levels to a record-smashing 13.88 feet at The Battery, at Manhattan’s southern tip. (The old record of 11.2 feet was set when the great Category 5 hurricane of 1821 slammed into New York City.) Low-lying parts of the city were flooded, including the Brooklyn Battery and Queens-Midtown tunnels and several subway tunnels. Damage to the city’s subway system was described as the worst in its 108-year history, and Governor Andrew Cuomo warned that it could take weeks for the system to be fully functional. In New Jersey, large chunks of Atlantic City were under water. City officials called it the worst storm in the city’s history. An “unusual event” and then an “alert” were declared at Oyster Creek in Lacey Township, the nation’s oldest nuclear plant, after waters rose to six feet above normal sea level. All along the East Coast, Sandy’s “life-threatening” (in the words of the National Weather Service) storm surges poured huge volumes of water over flood barriers designed to protect cities and beaches.
This aerial image shows coastal flooding along Long Island, NY, after Hurricane Sandy had swept through. Property damages will be in the tens of billions of dollars. (Credit: U.S. Coast Guard)
For the Record Books
Sandy’s devastating storm surges tell only part of the story. For hurricanes, “the lower the pressure, the more dangerous the storm” is a useful rule of thumb. Normal atmospheric pressure at sea level is around 1013 millibars. Around the time it made landfall near Atlantic City, Sandy’s atmospheric pressure plunged to a low of 946 millibars. That tied the record set in 1938 by the Great Long Island Express Hurricane for the lowest ever for a storm north of Cape Hatteras, North Carolina. Other hurricanes have had lower pressures, but those low pressures are typically found in more tropical waters.
The superstorm also smashed the record for total kinetic energy (calculated by a formula taking into account wind speed and total area), according to Jeff Masters of the Weather Underground. That’s a big deal considering it beat out storms with much stronger winds, including Category 5 (the highest) hurricanes such as Katrina, Andrew, and Wilma. Because Sandy stretched out over hundreds of miles, it put a huge volume of ocean water into motion. That energy fueled the storm surge.
Perfect Storm Sequel?
Unfortunately, Sandy was (and remains) a real-life nightmare, not a disaster movie. Despite its official name change to a “post-tropical cyclone” after it made landfall, Sandy more than lived up to its advance hype. Hundreds of thousands of people were forced to flee their homes in states along the coast as the hurricane approached. The potent combo of ferocious winds, downed trees, and storm-surge floods knocked out power to 7.6 million homes and businesses in fifteen states across a band stretching from Maine to the Carolinas. By Wednesday, 40 deaths were already blamed on the storm in the U.S. (It killed at least 67 others in the Caribbean before it reached the United States.) President Obama declared New York and New Jersey federal disaster areas. Air and rail transportation came to a virtual standstill across the region. Hundreds of miles from the storm’s center, blizzard conditions blanketed the Appalachian Mountains of West Virginia and western Maryland, Tennessee, and North Carolina with as much as 30 inches of heavy, wet snow. In Chicago, the city braced for huge swells on Lake Michigan of up to 24 feet, and wind gusts of 60 mph.
Sandy’s not done yet. Although now weakened to a tropical depression (with winds below 39 mph) as it pushes northward towards Canada, Sandy’s still-huge remnants are creating a soggy, windswept mess. The total bill for damages won’t be known for days or weeks, and the effects could linger for years.
Freak Event or the “New Normal”?
Hurricane Sandy unleashed a once-in-a-century storm surge upon New York City and other low-lying coastal areas of the Northeast. Unfortunately, such events are going to be much less rare in this century, according to climate scientists. Global warming means rising seas—due to melting of ice and thermal expansion of seawater—and it also means more severe weather in general. Higher seas and more frequent or more intense storms could make Sandy-like superstorms regular visitors to our shores. A study published this year in Nature Climate Change predicted that the 100-year storm surge that Sandy brought to New York City may occur as often as every three years, or at least as often as every 20 years, if the sea level rises as projected through this century.
Resources
NASA: Videos, descriptions, and satellite images of Hurricane Sandy
NOAA StormCentral: Archive of major storms
Atlantic Oceanographic & Meteorological Laboratories, Hurricane Division: Frequently Asked Questions About Hurricanes
