8 January 2016

All the winter's a weird weather stage; Here are the players

In this photo taken Jan. 10, 2014, the United States side of Niagara Falls in New York has begun to thaw after the recent "polar vortex" that affected millions in the U.S. and Canada. Get ready for weather whiplash as powerful climatic forces elbow each other for a starring role in making winter weird. The spine-chilling polar vortex is taking center stage at least in Europe and much of America bringing persistent cold _ except in Hollywood where soggy El Nino won’t give up the spotlight.
Get ready for weather whiplash as powerful climatic forces elbow each other for starring roles in a weird winter show.
The spine-chilling polar vortex is taking center stage in Europe and bringing persistent cold to much of North America — except in Hollywood, where soggy El Nino won't give up the spotlight.

After El Nino delivered a balmy Christmas Eve to the eastern U.S. and shattered national records with a warm, wet and wild December, Minnesota may host one of the coldest NFL playoff games in history this Sunday, with wind chills around 20 below, meteorologists predict.
"The biggest thing is this whiplash," said University of Oklahoma meteorology professor Jason Furtado. "It's going to be a shock for people."
The center of the cold blast starts this weekend in the U.S. in the upper Midwest, and then moves to the Hudson Bay area next week, while in Europe it starts in the east and north and then spreads, Furtado said. Europe may have to get used to temperatures 20 or so degrees below normal.
"Temperature will be dominated by the impact of the polar vortex," said Judah Cohen, seasonal forecast chief for the private Atmospheric and Environmental Research company outside Boston. It will feel similar to 2013 and 2014, he said.
The fourth front in as many days in San Diego County produced snow on Mount Laguna, Calif., and the area around it, making for a winter wonderland for children and adults alike.|Snowmen were abundant at the recreation area off Sunrise Highway near Mt. Laguna, Calif., Thursday, Jan. 7, 2016.

Americans became painfully familiar with the polar vortex during those winters. This time, America's winter temperatures will depend on when the wet and warm El Nino pushes itself back to prominence, Furtado said.
"We have all of these large and unusual events happening all at the same time and I don't think it has ever happened before," said Rutgers University climate scientist Jennifer Francis.
For a winter this dramatic, it may help to consult the program:
THE CAST
The star is El Nino, a veteran of this stage for a few decades now. This natural warming of the central tropical Pacific occurs every two to seven years or so, and changes weather worldwide, especially in the Americas and Asia. It is closely associated with heavy rain in California, and general warming. It has less effect in Europe because that's further away. With its flipside, La Nina, it is known as the El Nino Southern Oscillation, and it lasts about a year.
Playing off against El Nino is the Arctic Oscillation, and its index measures differences in atmospheric pressure between the Arctic and mid-latitudes. When the AO is positive in the winter, polar air stays trapped up north and the weather is relatively mild further south. When the AO is negative, the cold Arctic air escapes and plunges into lower latitudes, treating the United States and Europe to the polar vortex — a swirling air mass that carries spine-chilling temperatures.
Kathleen O'Brien, of Portland, Maine, and Kathryn McBrady, of Scarborough, Maine, take in the view of a fiery winter sunset overlooking Back Cove, Thursday, Jan. 7, 2016, in Portland, Maine. The former classmates at Catherine McAuley High School are visiting while home on college break. O'Brien is now studying in Italy while McBrady attends Providence College.

The North Atlantic Oscillation is a bit player with a big influence over Europe's weather. As with its Arctic cousin, the more negative its index, the colder the continent becomes.
The jet streams also are important to watch. These rivers of air heavily influence local weather everywhere, carrying storms and clearing skies around the planet. Usually in the winter, the jet stream that affects most people in the United States and Europe moves relatively straight from west to east. But when it weakens, it can plunge south and north and even get stuck at times, creating odd extremes.
Another air pattern playing a small but key role is the Madden-Julian Oscillation, which travels in the warm parts of the Indian and Pacific oceans, and may have triggered changes that "flipped the switch" in December, Furtado said.
Still other characters may be a factor in making the jet streams oscillate more wildly: A huge
Hats and gloves are hung up for anyone in need Monday, Jan. 4, at the Blue Water Center for Independent Living in Port Huron, Mich. This is the second year that BWCIL has set out a clothesline adorned with winter essentials, free for anyone who passes by.
blob of warm water in the northern Pacific, unusually low sea ice levels in the Arctic's Barents Kara sea area; a cool patch of water off Greenland, likely from melting ice sheets and glaciers; winter storm Frank that hit England; and of course man-made climate change.
ACT ONE
This was last month. El Nino appeared in classic form, tying 1997-1998 for the strongest on record. The Arctic Oscillation was very positive, trapping cold air in northern latitudes. With so many warm, wet days further south, spring flowers popped up and trees bloomed in December.
"It's not surprising we were 70 degrees on Christmas Day," said Mike Halpert of the National Oceanic and Atmospheric Administration's Climate Prediction Center in College Park, Maryland.
This photo provided by the National Park Service shows a rockslide that closed Highway 140, one of the access routes to Yosemite National Park, Calif., Thursday morning, Jan. 7, 2016. The rockfall occurred at 5:45 a.m. below the Arch Rock Entrance Station in the area of the October, 2014 Dog Rock Fire, according to a statement released by the park. No injuries were reported.

El Nino often spawns winter tornadoes in the southern U.S. and they appeared on cue, killing two dozen people in just four days. The heavy rain that flooded the Mississippi River Valley isn't usually an El Nino signature though, Cohen said.
ACT TWO
The switch flipped: The Arctic Oscillation and its North Atlantic sidekick went negative big time.
"When it's a negative AO, that's when people start mentioning the words 'polar vortex'," Halpert said.
High surf batters the break wall at Cabrillo Beach in San Pedro, Calif., Thursday morning, Jan. 7, 2016, as another powerful El Nino-driven storm lashed coastal areas of California on Thursday. The storm created waves that forecasters said could reach 16 feet while sending scattered thundershowers across inland areas.

This time, there's cold air, but it's mostly dry so far, despite El Nino, which still spawns a series of rainstorms hitting California. Meteorologists say wetter weather could bring heavy snowstorms, but that's not likely for another week or more, although cities along the Great Lakes may get lake effect snow.
So far the east-moving moisture from El Nino is staying south of the Arctic plunge, but that may change.
For now, the AO is dominating in its fight with El Nino, especially in Europe, Cohen said. NFL players and fans will likely brave temperatures around one below zero in Minneapolis.
ACT THREE
No spoilers here. Will the polar vortex hold the stage for weeks or months? Will the cold AO and wet El Nino combine for whopper snowstorms?
Flagstaff resident Anthony Martinez pushes a motorist out of the snow in Flagstaff, Ariz., Thursday, Jan. 7, 2016. A series of El Nino-related storms dumped heavy snow on the region.

Rutgers' Francis doesn't think the moisture and the cold can keep avoiding each other, saying "we're going to have major major dumps of snow. We just don't know where."
Furtado predicts El Nino will push aside the cold in America, but not in Europe, where it has less of an influence. Cohen is less certain about what will happen as these forces morph and interact over time.
"There's a lot going on; the weather has been crazy," Cohen said. "Expect the unexpected."
(AP)

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