A number of anomalous events have been observed that could be contributory factors, as more data becomes available there will be greater clarity, for now it’s largely speculation and some conjecture.
One factor that is almost certainly influencing the jet is the formation of opposing Rossby Waves, these winds work against the anticlockwise movement of the jet stream and if the two systems impact head on then the jet stream can stall.
The most obvious manifestation of this occurred in 2010 when the jet stream effectively ground to a halt creating a virtual traffic jam of weather systems around the world. At the time there was an area of particularly hot weather over Russia, this remained locked in place and so amplified the warming, the outcome was the devastating heatwave that crippled Moscow and claimed 50,000 lives.
This same stalling event ensured the failure of the jet to migrate across the Himalayan Plateau such that when the seasonal Monsoon cell migrated across Pakistan it was blocked in it’s northerly/easterly track. The result was that the rains fell in a concentrated area bringing flooding to 40 million Pakistanis.
If the Rossby Waves impact upon the jet at a more obtuse angle then the result can be to knock the jet off-course, this can push the jet to a more northerly or southerly flow.
The propagation of Rossby waves, as with many wind systems, is a combination of temperature (pressure) gradients and the coriolis effect.
The Coriolis force sets in motion a circulatory wind pattern, the fluidity of which allows shearing that impacts upon the Coriolis force along the sheared coordinate, this occurs a s a consequence of changes to the Coriolis force with latitude. The phase velocity of the waves sees a westward movement of the air mass whilst, at the same time, the group velocity can be eastward or westward. It’s this westward component that works in opposition to the jet stream.
The most pronounced warming is occurring in the Arctic region, this is creating greater temperature gradients across the mid to northerly latitudes – right where the jet stream and Rossby waves interact. It’s thought that the enhanced Arctic warming is affecting the northern hemispheric temperature and pressure gradients that in turn are impacting upon the propagation of Rossby waves.
Specifically what we’ve seen happening in the US is the formation of a large meander in the jet stream, something that is typical of Rossby wave opposition. This began several weeks ago as a deviation in the jet stream as it passed over Canada, it become ever more pronounced as the jet edged further southward until it created a “drop”, a very large meander that extends down across large parts of North America.
The jet stream itself acts as a barrier against the north-south and south-north migration of weather systems. If for example, a weather system moves northward into the path of the jet stream, the jet will drag they system off to the east, and in respect of North America this means propelling the system out across the Atlantic.
The barrier acts to keep cold Polar air to the north of it and the warmer air to the south. When a large meander develops it allows the cold air to flood down from the Arctic and the result is the cold wintry conditions affecting much of North America.
Whilst we have a good understanding of Rossby waves and their impact upon the circumpolar jet, we can’t say with as much certainty how they are being affected by global warming. It’s safe to say that they are, this much is a given, but quite how that works is something that remains to be determined.
Another influential factor is the circulation of wind in the Arctic itself. This is governed by the presence of an anticyclonic air-mass over Canada and a cyclonic one over Siberia creating an established flow of wind from the high to the low pressure area.
Since the mid 1980’s it had been predicted that global warming would disrupt the wind patterns and the first instance of this happened in 2000 when a complete reversal of wind patterns occurred, an event known as an Arctic Dipole Anomaly. Since then it’s happened a further nine times.
When the anomaly is in it’s positive phase there is, in essence, a reversal of warm and cool. Those places that are normally bitterly cold become much warmer and the milder places experience unusual cold.
The impacts are felt far beyond the Arctic as the contrary winds are now in opposition with the jet stream and can push it far from it’s normal course, bringing disrupted weather to much of North America and Europe.
In your question you mentioned various influential factors such as the NOA, ENSO etc. These are cyclical events that regularly switch from the positive phase to the negative one. They are clearly influential in respect of some aspects of the climate but the correlation between such oscillations and any of the jet streams (there are four of them) is indistinguishable amongst the normal variation.
If there was a correlation we would expect to see regularity in the changing dynamics of the jet streams, such as more southerly meanders coinciding with a high NOA Index. However, such characteristics are not evident; that’s not to say they don’t exist, there will of course be an influential factor, just that it’s a very small one.
That said, climatic signals are subject to amplification and attenuation, rather like the butterfly effect, such that a small and seemingly insignificant event can be compounded into something much greater. Whilst unlikely, we can’t rule out the possibility that a given sequence of oscillatory events can, in certain circulmstances, act as a trigger.
We've just completed a LONG String of Mild Winters in the U.S.. And now Ma Nature is "even"-ing up the Score" a little. Most of the REST of the Northern Hemisphere- has had an unusually Mild Winter this Time around... It was just "Our Turn"- to Share in what Everyone ELSE had to Deal with- in previous Years... :)
Winter but temps were lower than normal Polar vortex went further south than normal and brought the bitter cold along with it. Arctic melt warming the ocean, creating more evaporation and effected the jet stream
I'm having trouble coming up with an answer, especially when I see so many homeless folks living under the bridge overpasses that are freezing right now.
Weather
And no, the cold weather was not caused by global warming. It happened in spite of global warming. It happened because global warming has very little effect on very cold weather.
http://jcmooreonline.com/wp-content/uplo...
Because fear sells advertising and keeps people glued to their tv's. It wasn't really any colder than usual. People just have such short memories that they can be told how bad it is again and again and they will believe it.
It is because of the climatic change over there and particularly due to the blow of heavy cold air.
due to too much water vapor from burning fossil fuels
You forget to include the sun and ozone
the government is behind this, im from NY but im currently in Germany and there still no snow, every where else is going thru global warming except the states.. im hearing if you put a lighter to a snow ball it wont melt it will turn black or burn like plastic, if i waas there i would test it to see if its true
Let's look at the winter outlook for the US coming out in the fall <>.http://www.noaanews.noaa.gov/stories2013/20131121_winteroutlook.html>. We see no signs that there will be such a pronounced cold spell over the E US and Midwest. Clearly the polar jet is scrunched further south this year which is allowing colder temps; this is obvious. I don't see much about causation of this phenomenon, though. Did it have anything to do with suppression of the N Atlantic current due to stratification allowing colder air to push south, a blocking pattern over the W US, some phenomenon allowing for unusually cold air in Canada, etc...? Or perhaps are there more inconspicuous variables at play such as the strong typhoon season in SE Asia and weak hurricane season in the Atlantic in previous months, the ENSO and/or NAO readings, or the Indian monsoon? When doing at least a simple search online, I don't see much, if anything, about causation. People are either saying, well there's climate change and, oh hey, look at the jet stream, or ope, I guess climate change has been debunked. People's over-simplifications of something complex is worrisome. Any climatologists out there that can shed some light on this year's cold spell? Any and all ideas about WHY the polar air is sitting further south would be much appreciated. Thanks.
Al Gore forgot to pay his fuel bill.
Because solar activity is on the decline.
It's the Sun that drives climate --- not human activity.
Learn all about it in the videos below.
Top climate scientists say there is no man-made Global Warming.
The Great Global Warming Swindle
