February 3, 2011

La Nina Blamed For The Blizzard Of 2011

Millions of Americans are dealing with an above average year for storms as an atmospheric phenomenon continues to churn in the eastern Pacific Ocean with little chance of dissipating soon.

The current winter storm -- being called the blizzard of 2011 -- is possibly a product of the La Nina phenomenon that has been affecting the tropical Pacific Ocean for the past several months, the same phenomenon that is being blamed for the devastating floods and storms battering eastern Australia.

Here in the US, "Mother Nature has decided to show us what winter is like again," Mike Halpert, deputy director of the federal Climate Prediction Center, told The Associated Press (AP) on Wednesday.

Following several unusually mild winters, "the last couple of winters have been more like what winter should be," Halpert said.

This storm "will long be remembered" because the heavy snow and strong winds created white-out conditions in a large part of the country, including some populous cities, said Louis Uccellini, director of the government's National Centers for Environmental Prediction.

Uccellini told AP's Randolph E. Schmid that the storm was following a classic pattern -- from the Midwest to the Northeast and redeveloping off the eastern seaboard. The huge storm left snow, measured in feet in many areas, and thick ice from Oklahoma and Missouri to the Great Lakes and eastward. Record single-storm snow totals were recorded in Chicago.

Uccellini, a longtime weather expert, says, however, the storm cannot be blamed on climate change.

"You can't relate climate change to individual storm systems. Clearly, there have been similar storms in previous decades. As intense as this storm is, it's equivalent to other major storms that they've seen in past decades," he said.

The real culprit, at least partially, of this storm is more readily the La Nina atmospheric phenomenon in the Pacific. La Nina is a periodic cooling of the surface temperatures of the tropical Pacific Ocean, the opposite of the more well-known El Nino warming.

Both El Nino and La Nina patterns can have major impacts on weather around the world by changing the movement of winds and high and low pressure systems.

"We are linking the storm tracks to the La Nina pattern which dominates the flow coming off the Pacific," Uccellini explained to AP in a telephone interview. "This follows the pattern we would expect through the Ohio Valley and with heavy precipitation to the Great Lakes."

"The storm is going where we would expect it, according to La Nina," added Halpert.

The storm followed a traditional pattern, unlike several storms that previously struck this winter by moving up the East Coast rather than across the Midwest.

Uccellini said the North Atlantic Oscillation has contributed to the snowy season, as it shifted into a negative phase, leaving La Nina in total control.

The North Atlantic Oscillation is a shift in high and low pressure systems. When in the positive phase it can force storms to the north, but when it relaxes, as it currently has done, the US East Coast tends to see an above average amount of cold air and snow.

Halpert also explained that the related Arctic Oscillation has pushed cold weather farther south into the United States than is typically expected.

This current La Nina ocean pattern is expected to last several more months, but will continue to weaken.


Image Caption: Chicago's Lake Shore Drive, with abandoned, snowed-in cars and empty lanes. Credit: Wikipedia   


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