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    How Sandy Exploded Into a Superstorm One Year Ago

    By By Andy Mussoline, Meteorologist
    November 01, 2013, 3:36:02 PM EDT

    Superstorm Sandy, the behemoth that wrote a new chapter in modern meteorology, began in textbook fashion in the Caribbean Sea.

    "Sandy formed exactly where we look for development late in the hurricane season," AccuWeather.com Expert Senior Meteorologist Dan Kottlowski said.

    The first sign of life from Sandy occurred exactly one week before the superstorm made its historic landfall. At 11 a.m. EDT Monday, Oct. 22, 2012, the National Hurricane Center (NHC) in Miami declared that Tropical Depression 18 had formed in the southwestern Caribbean Sea, approximately 320 miles south-southwest of Jamaica.

    The depression strengthened into Tropical Storm Sandy only six hours later.

    Essentially every meteorological factor to support strengthening was in place across the Caribbean Sea. Very warm water and a moist atmosphere were among the factors fueling growth.


    Sandy became a Category 1 hurricane with sustained winds of 80 mph at 11 a.m. on Oct. 24, 2012, before making its first landfall just five hours later in southeastern Jamaica. Later that night, it exploded before it made a second landfall in eastern Cuba. Sustained winds reached 115 mph in eastern Cuba, making it a Category 3 hurricane.

    "Sandy's initial northward track was not unusual, but its explosive growth before making a second landfall in eastern Cuba was surprising," Kottlowski said.

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    The hurricane moved into the Bahamas and weakened the following morning of Thursday, Oct. 25, 2012. Sustained winds were 105 mph. By Saturday, Oct. 27, 2012, Sandy was moving away from the Bahamas, struggling to stay a hurricane, with sustained winds around 75 mph for much of the day.

    Despite this weakening, the NHC noted in its review of the storm, that "the structure of the cyclone [Sandy] was quite unusual." The storm grew to an immense size.

    "Tropical storm-force winds (winds in excess of 40 mph) expanded over a huge area on Saturday, Oct. 27, and now extend 450 miles out from the center," NASA's Deputy News Chief in the Office of Communications Rob Gutro said at the time. "Just a day before, those tropical storm-force winds extended outward up to 275 miles."

    "The storm's circulation now reaches more than 2,000 miles," Gutro said.

    To put that in perspective, the distance between Las Vegas and Washington, D.C., is close to 2,000 miles.

    Meanwhile, as Sandy was wreaking havoc in the Caribbean and the Bahamas, the weather in the mid-Atlantic was tranquil. A sprawling high pressure system contributed to the fabled "calm before the storm" in the week leading up toward Sandy's landfall.

    A high resolution visible satellite animation of Hurricane Sandy on Oct. 28, 2012, courtesy of NASA.

    "The day before Sandy struck, the storm was heading northeastward off of the North Carolina coast, and it seemed like Sandy was heading out to sea," Expert Senior Meteorologist Dave Dombek said. "However, looking at the weather maps, you knew that Sandy had to eventually make a sharp left hand turn to the coast."

    "The normal atmospheric west to east steering flow was essentially turned on its side," Dombek said. "It was an exercise in faith at that time, sticking to our guns on the landfall occurring on the Jersey shore."

    The hurricane had one last burst of strengthening the morning of Monday, Oct. 29, 2012, about 205 miles southeast of Atlantic City, N.J., as sustained winds increased to 90 mph. At its peak, the NHC reported that the extent of tropical storm-force winds grew to about 1,000 miles prior to landfall.

    Sandy became the largest tropical cyclone on record according to the NHC.

    "The warm waters of the Gulf Stream contributed to the strength of Sandy off the east coast of the United States," Kottlowski said.

    Shortly after sustained winds increased to 90 mph off the mid-Atlantic coast, it began to take the historic sharp left turn toward the New Jersey coastline.

    "The path Sandy made toward the New Jersey coast was really a worse-case scenario for the mid-Atlantic," AccuWeather.com Meteorologist Mark Mancuso said. "It was crazy."

    Sandy made landfall just north of Atlantic City, N.J., during the evening of Oct. 29, 2012.

    Even worse, Sandy made landfall right at high tide, adding another two to four feet to the storm surge.

    "Unfortunately, not only was it a devastating track for New Jersey, but the timing couldn't have been worse," AccuWeather.com Meteorologist Bernie Rayno said. "The timing correlated exactly with high tide."

    The unprecedented path along with the timing of the storm brought a catastrophic and deadly wall of water into the New Jersey and New York coastlines in addition to staggering damage to the region.


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