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Why Is Hurricane Sandy Such a Big Deal?
A view of Hurricane Sandy from GOES East satellite on Sunday, Oct. 27.
Credit: NASA GOES East, Stuart Rankin via Flickr

Some people have asked: Why is Hurricane Sandy such a big deal if it's only a Category 1 hurricane?

There are several reasons. For one, a Category 1 hurricane is nothing to be trifled with, and is capable of causing destruction of property and loss of life.

But what's unusual about now post-tropical Sandy is that it's so large, at least for the Northeast at this time of year. The main reason for its size is that Sandy has been morphing from a tropical cyclone to an extra-tropical cyclone, said Chris Davis, a scientist with the University Corporation for Atmospheric Research in Boulder, Colo. Extra-tropical cyclones, or those outside the tropics, tend to be significantly larger than tropical ones. Although Sandy is huge, its size is not unprecedented, he said. What's more unusual is the location and timing — nor'easters can get this big, but usually occur in the winter, he said. Sandy currently has hurricane-force winds extending up to 175 miles (280 kilometers) from its center, and tropical storm-force winds out to 485 miles (780 km), according to the NHC. That's second only to 2001's Olga in terms of the size of wind field of a storm. (Olga's winds extended out 600 miles (965 kilometers).)

This means that many areas along the coast, from Virginia to Massachusetts, will be lashed with hurricane-force winds for 36 hours or more, according to the National Hurricane Center (NHC).

The large area over which the winds are spread also makes for a large storm surge, since so much water gets piled up and pushed toward the shore. In certain areas, such as the Long Island Sound, the storm surge is concentrated by winds racing to the southwest, funneling waters toward the shore and leaving them nowhere to go but onto land. This is made worse by today's full moon, which already makes for higher than usual tides.

Hurricane Sandy began as a tropical cyclone, fueled by warm water, warm, moist air and the convection these phenomena can create, Davis told OurAmazingPlanet. These hurricanes can be likened to heat engines, transferring heat from the surface of the ocean to higher in the atmosphere.  By contrast, extra-tropical cyclones are driven by a difference in temperatures over a wide area — cold air to the northwest, warm air to the southeast, which then swirls together, Davis said. This process is most efficient over huge distances, said. 

This transition has helped the storm to strengthen before coming ashore, according to the NHC.

About one million people are already without power this evening (Oct. 29), Reuters reported.

This story was provided by OurAmazingPlanet, a sister site to LiveScience. Reach Douglas Main at Follow him on Twitter @Douglas_Main. Follow OurAmazingPlanet on Twitter @OAPlanet. We're also on Facebook and Google+.