Why Superstorm Sandy's Track Was So Unprecedented

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S​uperstorm Sandy was the costliest, most destructive storm to strike the northeastern United States in modern times, due largely to its unprecedented left turn into New Jersey.

I​t has been 10 years since Sandy grew into a giant off the East Coast, then slammed ashore as the deadliest storm of tropical origin in the Northeast since 1972. Sandy claimed 159 lives in the U.S., 72 during the storm and another 87 in its aftermath.

(Visit our Superstorm Sandy page for more coverage of the 10th anniversary.)

S​andy's damage toll of $81.9 billion (adjusted for inflation) still makes it the nation's fourth-costliest weather disaster since 1980, topped only by hurricanes Katrina, Harvey and Maria.

I​ts record size, devastating record storm tides along the coast from Connecticut to Lower Manhattan down to the Jersey Shore and Delaware River in Philadelphia, and even heavy snow in the Appalachians will never be forgotten.

Let's focus on how bizarre Sandy's track was and how that happened.

U​nprecedented Sharp Left Turn

Once it left the Caribbean after hammering eastern Cuba, Hurricane Sandy took an S-shaped path through the central Bahamas, then well off the Southeast coast from Oct. 25-28, 2012.

I​n the 24 hours that followed, Sandy curled sharply northwest then plowed directly into the New Jersey shore just north of Atlantic City on the evening of Oct. 29, 2012, as it transitioned to a still intense post-tropical cyclone.

N​ew Jersey is no stranger to hurricanes. According to NOAA's best track database, 25 other hurricanes before Sandy had tracked within 100 miles of the Garden State in records dating to 1858.

B​ut the large majority of those past hurricanes were moving northeastward parallel to the Jersey Shore, as you can see by the large number of gray lines in the animation below.

O​ne of those, Hurricane Irene, was a close-call scenario for storm surge in the New York City metro one year before Sandy, but led to severe inland flooding in parts of New York and Vermont.

W​hile there were a few past tracks that took a more northward jog inland near or over New Jersey, including Connie in 1955 and a September 1903 hurricane, Sandy's almost westward track into New Jersey was unlike any other in recent history.

At the time of the study, it was unknown what, if any, role climate change had played in Sandy's track.

However, a 2021 modeling study found sea-level rise from climate change was responsible for an additional $8.1 billion in damage from Sandy.

This weird path was challenging to forecast.

Yet one particular model – the "European model" run by the European Centre for Medium-Range Weather Forecasts – performed exceptionally well hinting at this Sandy curve potential eight days before landfall, as we detailed in a comprehensive recap shortly after Sandy.

W​hy Sandy Turned Left

By late October, the jet stream over the U.S. is stronger, as cold air plunges into the U.S. become more common in the fall. This stronger, southward-plunging jet usually sweeps hurricanes away from the East Coast out to sea.

I​n late October 2012, that strong jet stream was there, but there was a problem downstream.

High pressure aloft near southern Greenland strengthened and expanded into eastern Canada. That set up a giant blocking pattern in the winds, similar to a large rock in a small creek.

I​nstead of the jet stream sweeping Sandy away from the East Coast, the jet was forced to dive southward into the Ohio Valley and Southeast.

T​he flow around these two features grabbed Sandy and forced it sharply inland over the mid-Atlantic states.

B​y Halloween morning, about 36 hours after its New Jersey landfall, Sandy's post-tropical remnant low was still swirling over northeast Ohio, rather than far out in the North Atlantic as you'd expect from a more typical storm like this to affect the Northeast.

I​t's a weather pattern meteorologists who covered it won't soon forget, ranking with the equally strange pattern that led to 1991's Perfect Storm.

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