Polar Vortex Behind U.S. Cold Blast
An image captured by a NOAA satellite on Jan. 6 shows an area of low pressure from the polar vortex over North America.
Winter Storm Hercules brought heavy snow and fierce winds to the Midwest and Northeast and has been blamed for at least nine deaths so far. Here, drivers in Cleveland battle high winds and heavy snowfall as they navigate on The Detroit Shoreway on Cleveland's West Side.NEWS: Snowstorm Slams U.S. Northeast
This satellite image taken on January 3, 2014 by the Suomi NPP satellite shows the blanket of snow that stretches from the Midwest across to New England.
The Washington Post/Getty Images
A pedestrian walks along Carroll Creek in Frederick, Md.PHOTOS: Blizzard Nemo Slams Into U.S. East Coast
Firefighters in Brooklyn, N.Y. dig out of their firehouse after Hercules deposited up to 8 inches of snow in the area.NEWS: 'Snowquester' Storm Seen from Space
Headlights of a car illuminate the street on Cleveland, Ohio's W. 112th St. after power was lost.Naming Nemo: How the Storm Got Its Name
A snow plow removes snow on a street near a statue put on a bench in New York.
Being in the doghouse isn't always bad, especially for this Brooklyn, N.Y. dog scooting into an actual doghouse, during the fun of newly fallen snow.PHOTOS: Winter Wonderland
A husky in Somerville, Ma., with snow-fearlessness in its genes, waits for its owner outside of a store.
A Brighton, Ma. resident takes his son and puppy to a dog park for some fun before the storm worsens.
A branch and its berries in St. Michael's, Md. bear up under the weight of Hercules.
A young man snowboards in Chicago's Humboldt Park. An unexpected look for a beach, but that's winter for you.
A Cleveland, Ohio resident clears snow in the Edgewater neighborhood of the city.
Twitter users, too, have been photographing the new year's winter weather. From Twitter user @GutterIsATool: @Discovery_News Here's a good #snowstorm pic from the NHL Winter Classic in Ann Arbor, MI.
From Twitter user @RiverROC1: #NORDHOUSE DUNES WILDERNESS, MANISTEE NATION FOREST, MICHIGANpic.twitter.com/zYca7K34Qx
From Twitter user @JPMajor: @Discovery_News 27" drifts in my back yard here in RI!pic.twitter.com/Oey5BKzaIj
The latest public enemy No. 1 comes complete with an ominous, super-villain name and a tendency to waver drunkenly around the Northern Hemisphere, leaking great, vast gasps of frigid Arctic air into normally more temperate latitudes.
But what is the polar vortex, and why has it been making so much trouble over the last few winters?
First off, there's the scary name. It comes from the fact that when viewed from above the North Pole, the polar vortex forms a river of air that spins in a rough circle, around the hemisphere from west to east. It's always been there, but most of the time it minds its own business and serves as a wall of wind to hold wintry Arctic air where it belongs -- in the Arctic. But this week it's not doing that.
“That wind can look like an ellipse or it can be wavier,” explained James Overland, a senior scientist at the NOAA/Pacific Marine Environmental Laboratory in Seattle. “That wavy pattern is what we are seeing today.”
The waviness is usually bad news for the Eastern United States because that region is already on the edge of a back up and turn in the vortex's river of air, caused by the obstruction of the Greenland's mountains, Overland said.
The wavier the vortex, the more likely it will swerve even more as it veers over and around Greenland, sending a lobe of Arctic air down the center of North America and over the East Coast like a blast straight from the hyperborean lungs of Jack Frost. The past four out of five winters have seen seen more of these blasts, Overland said. Which naturally prompts the question: Why?
“The atmosphere will often repeat itself,” said forecaster Bob Oravec with the National Weather Service in Maryland.
Historic cold events in January 1994, 1985 and during the 2009 first inauguration of President Barack Obama, for instance, happened when the atmospheric patterns looked similar to what we are seeing this week. But that doesn't explain why extreme winter weather may be on the rise.
“We can't really explain why we tend to have more extreme events,” said Overland. “But it's clear that we are.”
And while some non-scientists and lobbyists argue the cold waves disprove tomes of peer reviewed science on global warming, the scientists themselves are not suggesting this at all -- although they have a range of opinions on the cause of the events.
On one hand some researchers put it down to dumb luck, Overland said. After all, four out of five winters isn't a lot to go on. On the other hand, there have already been connections found between Arctic warming changes in the northern jet stream which cause weather patterns to slow and increase the changes of heat waves and droughts. Perhaps the dramatic warming of the Arctic is changing the wintertime behavior of the polar vortex as well.
Whatever the cause, Overland points out that the waviness of the polar vortex is not permanent, and can switch back and forth, from wavy to a nice, tight circular pattern in a matter of weeks, as has happened already a few times this fall and winter.
“It's not a prolonged event,” agreed Oravec. By the end of the week the worst of the cold will have moderated, he said.