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NASA Asks Where Has All The Snow Gone?

On their science blog NASA has asked ‘What Happened To All The Snow?’ and it’s a good question, considering that the U.S. is currently experiencing a surprising lack of snow that, come spring time, may have serious consequences for communities reliant upon the snow runoff.

“The Mammoth Mountain ski resort in the Sierras of California got more than 200 inches of snow last December,” says NASA climatologist Bill Patzert of the Jet Propulsion Laboratory. “This December they got less than 10 inches.”

It’s not only snow that’s proving a surprising no-show, with temperatures acting oddly as well.

“It’s 86 degrees in Los Angeles today [Wednesday, January 4th],” says Patzert. “Everyone thinks it’s July! In fact, it’s warmer today in LA than it was on July 4th last year. And it’s been in the 60s and 70 even in the Dakotas lately.”

So What’s Going On?

Patzert points to two culprits which, in hindsight, are not so surprising: La Niña and the Arctic Oscillation.

“First of all,” he explains, “we are experiencing a La Niña pattern of sea surface temperatures in the Pacific Ocean. This pushes the jet stream and the cold arctic air northward. On top of that, this year’s Arctic Oscillation has been stronger.”

As can be seen in the image below, the Arctic Oscillation is the whirlpool motion seen circling air around the North Pole. Weaker circling like during 2010 allows cold air to escape the whirlpool and head south over the U.S. However, when the Arctic Oscillation is stronger it better controls the cool air, keeping it mostly hovering over the North Pole.

“This year the whirlpool has been more forceful, corralling the cold air and keeping it nearer the pole. That has reinforced the La Niña impact.”

Be Patient, the Snow Might Come

The corralling action the Arctic Oscillation has implemented has largely kept snow away from the continental United States, but it has simultaneously increased snowfall within the whirlpool.

“The strong positive AO has kept the Jet Stream north,” says Patzert. “Snow-delivering storm tracks are pounding Alaska.”

For example, the small town of Cordova approximately 150 miles east of Anchorage, Alaska, has received more than 18 feet of snow so far this winter turning roads into one-lane “snow canyons”.

“Be patient,” advises Patzert. “We haven’t gotten to the heart of winter. Hold off on selling the new dogsled. There’s plenty of time for snow. It ain’t over till the Siberian Huskies sing.”

So far in the winter of 2011-2012, the "AO Index" has been mostly positive, signaling a strong Arctic Oscillation. "Compare this to last year's negative AO Index and you can see the difference between the two winters," notes Patzert.

Seattle Takes a Pounding

Even as I write this, reports from Seattle, Washington, report that as much as 5 inches of snow has fallen in the city proper, while regions around Washington have received much more, with Tacoma receiving 8 inches and 20 inches falling in Thurston and Lewis counties.

Brad Colman of the National Weather Service said the morning’s steady and widespread snowfall was expected to be “gradually tapering off this afternoon.”

Julie Startup, spokeswoman for the State Patrol in King County, said there is concern about freezing rain hitting.

“Conditions on the roadway are already poor, the last thing we want to add to that is a freezing situation. If the freezing rain comes I’m hopeful people will drive carefully and get off the road,” Startup said.

Thursday is not likely to see anywhere near as much snow, with a mix of snow and rain more likely across the state as temperatures move up into the 30s.

Source: NASA Science
Photo Source: Ben Lakey




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