The science behind Hurricane Sandy: a confluence of trouble
An array of environmental characteristics helps explain its size, slow progress and the many
ways it can cause havoc.
By Neela Banerjee, Washington Bureau - 7:51 PM PDT, October 29, 2012 - WASHINGTON
Hurricane Sandy seems
straight out of a Hollywood
apocalyptic blockbuster. But a
confluence of environmental
and topographical
characteristics helps explain its
vast size, slow progress, storm
surge and multiple methods of
wreaking havoc on the coast
and deep inland, scientists say.
Sandy began as a big storm
when it formed in the
Caribbean, said Katie Garrett, a
meteorologist with the
National Weather Service. It
grew as it moved north into the
mid-Atlantic, fed by
unseasonably warm waters.
Sandy stretches about 940
miles — greater than the
distance from New York to Atlanta — said Jeff Masters, co-founder of WeatherUnderground.com and a former
flight meteorologist with the National Oceanic and Atmospheric Administration's hurricane hunters. Sandy is
the largest such storm to make landfall on the Eastern Seaboard since 1988, when the government acquired the
satellite technology and aircraft to start measuring the size of storms.
Sandy's course, from southeast to
northwest, is not typical, said Rick
Knabb, director of the National
Hurricane Center in Miami.
Although its path is "not 100%
unprecedented," it is unusual for a
storm of such size and strength to
move inland so late in the year,
Knabb said during a telephone
news conference Monday.
Even when Atlantic storms come
ashore, they usually head back out
to sea. Some powerful storms in
recent years did not make landfall at all, kept away by weather patterns. But Sandy was pushed into the midAtlantic states and New England because a high-pressure system near Greenland blocked its progress eastward.
That shift toward the northwest put Sandy on course to mesh with a cold front that began in California last week
and marched across the country, creating what Knabb and others say is an unprecedented weather threat. The
force of the eastward-moving front slowed Sandy, Garrett said, changing the hurricane into a nor'easter.
Even before coming ashore, Sandy had begun
to lose traits typical of tropical storms, such as
thunderstorms at its middle, Garrett said.
Instead, Sandy's merger with the cold front
threatened to cause severe snow in places. In
West Virginia, 3 to 4 feet were predicted in
some areas, with less snow in southwestern
Virginia and western North Carolina. "It's not
just a tropical storm, but a windstorm, a
snowstorm," Garrett said.
Coastal flooding
A 6- to 12-foot storm surge pushed ashore as high tides were peaking
between 6 and 9 p.m. Eastern time Monday.
Sandy also has produced dramatic storm surges.
The swirling movement of its winds created a
big bulge of water that typically moves to a
storm's center. There, the low pressure in the
atmosphere acts like a straw and pulls the water
levels even higher, Masters said. If a storm is
farther out to sea, that bulge eventually sinks.
But because Sandy moved to shallower waters
near the coast, that bulge had nowhere to go but
toward shore, he said.
The slowness of the storm meant it could sit
over the East Coast through several high tide cycles. Scientists were predicting 10- to 11-foot storm surges,
including high tide conditions, in places like New York and New Jersey. Monday night's full moon threatened
to add another foot to the surge, Knabb said. Finally, many inlets and bays in the mid-Atlantic are funnelshaped, which means water can surge in easily, but getting out is a challenge.
Knabb said he didn't expect water levels to return to normal until Wednesday.
neela.banerjee@latimes.com Copyright © 2012, Los Angeles Times
Questions
1. How did Hurricane Sandy begin? How did it grow in the mid-Atlantic?
2. How large was Hurricane Sandy? When was the last time a storm that size hit the eastern seaboard?
3. In what direction did Sandy travel? Why was it unusual for Sandy to make landfall?
4. What weather system pushed Hurricane Sandy into the mid-Atlantic States?
5. What weather system from California “meshed” with Sandy to create an even larger threat? What type of
weather was Sandy’s merger expected to cause?
6. How were Sandy’s dramatic storm surges created? What kind of storm surges and high tide conditions were
predicted?
7. Some are calling Hurricane Sandy a “frankenstorm”. Why is this a good term for the kind of storm that Sandy
evolved into?
8. Look at the “predicted storm surge” section in the “Flooding Severity” figure. Why do you think higher storm
surges are predicted for areas further inland in New Jersey?
9. Look at the “Coastal Flooding” figure. Describe how Hurricane Sandy affected the normal tides in Battery
Park, New York and in Atlantic City, New Jersey.