I have been mentioning this, the wacky weather possibly caused by the under reported jet stream split. Now, here is an actual scientist reporting the same thing.
Why Much of North America Skipped Winter
By Wynne Parry | LiveScience.com
January ranked as the fourth-warmest for the 48 U.S. states on record
since 1895. December, too, was above average, although not as
significantly. The final analysis for February is not yet in, but
weather watchers expect last month to rank above average
temperature-wise as well.
Of course, this year hasn't brought early beach weather for everyone; just ask residents of Alaska
and Europe, where a frigid cold snap is blamed for hundreds of deaths.
And the warmth has been blamed for contributing to the slew of
devastating tornadoes that hit the Midwest and southern U.S. on Friday
(March 2).
While scientists have said that global warming willcause an uptick in
extreme weather, they are hesitant to link any one event or even an
unusual season to climate change. Even so, they say, global warming may
play a role in the weird winter weather.
The jet stream
The key to understanding the unusually warm winter lies in the jet stream.
It is made up of high-altitude, westerly winds. Its polar branch, the
one important for determining winter weather, travels over the
mid-latitudes of the Northern Hemisphere in winter, according to Jeff
Masters, director of meteorology at the weather service and news site
Weather Underground.
The polar jet stream divides cold Arctic air to the north from warmer
air to the south. This year, meteorologists say, the jet stream has kept
the cold air bottled up farther north than usual. [Quiz: Test Your Weather Smarts]
As a result, warmer-than-usual temperatures this year have graced much
of the United States, particularly in New England, the Great Lakes and
the Upper Plains, according to Mark Paquette, a meteorologist with
AccuWeather.com. Southern Canada, too, has gotten its share of mild
winter weather
The polar jet stream is influenced by natural patterns, the most
prominent being fluctuations in the Northern Annular Mode, also called
the Arctic Oscillation. When the mode is in its so-called positive
phase, air pressure over the far north remains low, leading to a
stronger jet stream. This keeps the cold Arctic air bottled up to the
north. The negative phase, meanwhile, is associated with a weaker,
meandering jet that allows cold air to spill south.
Reversals
Until late January, the mode was in its positive phase, resulting in warmer temperatures farther north. [6 Signs Spring Has Sprung]
But a reversal of phase allowed the jet stream to meander some, and let
Arctic cold air move down into Eastern Europe. The result was a cold
snap that is blamed for killing hundreds.
The mode has shifted again since then. In fact, a strong jet stream
contributed to the tornados that hit the south and the Midwest last
week, as did the arrival of warm, moist air from the Gulf of Mexico,
according to Masters, who discusses the tornados on his blog.
La Niña and the future
Another large-scale atmospheric pattern, one related to temperatures in the equatorial Pacific Ocean, is also at play. This winter La Niña,
associated with cooler water temperatures in the Pacific, has been in
effect. La Niña is typically associated with drier-than-normal
conditions for the southern and eastern U.S. — largely consistent with
precipitation this winter, according to Deke Arndt, chief of the climate
monitoring branch at the National Climatic Data Center (NCDC) in
Boulder, Colo.
"The dryness looks like what we would expect with La Niña, the warmth
we saw is consistent with the positive Arctic Oscillation," Arndt said.
"The two of them tougher, all else being equal, would tend to produce a
warmer and drier winter, especially east of the Rockies."
Paquette predicts an end to this trend. "Mother Nature or weather
patterns have a way of evening themselves out. I think it only matter of
time before this mild dry pattern flips and we get into a much
different weather pattern."
You can follow LiveSciencesenior writer Wynne Parry on Twitter @Wynne_Parry. Follow
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