I have found Jeff masters writing/analysis and blogs the best l have ever read. He really is a great analyst.and communicator.
Thanks Ken. A reminder to visit his blogs more often.
Yes l did find this interesting. In particular his report on
the Jet stream
December 2011 jet stream pattern the most extreme on record
The cause of this warm first half of winter is the most extreme configuration of the jet stream ever recorded, as measured by the North Atlantic Oscillation (NAO). The Arctic Oscillation (AO), and its close cousin, the North Atlantic Oscillation (which can be thought of as the North Atlantic's portion of the larger-scale AO), are climate patterns in the Northern Hemisphere defined by fluctuations in the difference of sea-level pressure in the North Atlantic between the Icelandic Low and the Azores High. The AO and NAO have significant impacts on winter weather in North America and Europe--the AO and NAO affect the path, intensity, and shape of the jet stream, influencing where storms track and how strong these storms become. During December 2011, the NAO index was +2.52, which was the most extreme difference in pressure between Iceland and the Azores ever observed in December (records of the NAO go back to 1865.) The AO during December 2011 had its second most extreme December value on record, behind the equally unusual December of 2006. These positive AO/NAO conditions caused the Icelandic Low to draw a strong south-westerly flow of air over eastern North America, preventing Arctic air from plunging southward over the U.S. and Europe.
AND at the same time the
Wild swings in the December Arctic Oscillation
This winter's remarkable AO/NAO pattern stands in stark contrast to what occurred the previous two winters, when we had the most extreme December jet stream patterns on record in the opposite direction (a strongly negative AO/NAO). The negative AO conditions suppressed westerly winds over the North Atlantic, allowing Arctic air to spill southwards into eastern North America and Western Europe, bringing unusually cold and snowy conditions. The December Arctic Oscillation index has fluctuated wildly over the past six years, with the two most extreme positive and two most extreme negative values on record. Unfortunately, we don't understand why the AO varies so much from winter to winter, nor why the AO has taken on such extreme configurations during four of the past six winters. Climate models are generally too crude to make skillful predictions on how human-caused climate change may be affecting the AO, or what might happen to the AO in the future. There is research linking an increase in solar activity and sunspots with the positive phase of the AO. Solar activity has increased sharply this winter compared to the past two winters, so perhaps we have seen a strong solar influence on the winter AO the past three winters. Arctic sea ice loss has been linked to the negative (cold) phase of the AO, like we observed the previous two winters. Those winters both had near-record low amounts of sunspot activity, so sea ice loss and low sunspot activity may have combined to bring a negative
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I get the feeling that when we finally get to predict the Jetstream pattern ( shape and amplitude beyond 2 weeks) and the Artic oscilation and its southern hemisphere counterpart the antartic oscillation we will be in a great position to do some serious seasonal climate modelling.
I also wondered if these two weather variables are related. For example when AO anomaly is extreme then so is the Jetsstream anomaly.?
Is there any correlation between jetstream pattern and AO and AAO anomalies.
I also found it interesting that johnno said that there is an inverse relationship in other parts of the world.
quote
"This Winter so far has been the exact opposite of the 2009/10 Winter when alot of Europe was colder than normal but Northern Africa & the Middle East constantly saw above average tempertures most of that Winter.. This Winter (so far) it seems to have flip flopped"
So when American N/west and europe winter is warmer than average then the north africa and middle east is colder.?
Yep.. Very interesting! There's sure to be some correlation studies on this topic
I don't really follow world climate much at all but good to learn something new
Exxtending this idea of wild jetstreams and strong AAO's we have a bit of that hapening in the southern hemisphere atm
I think the jetstream , sub tropical at least has been quite out of bounds and the AAO has been strongly positive in December at the same time
I noticed Jeff masters was prepared to link some of this activity to solar activity and acknowledged our lack of understanding of jetstream forecsting and AO 's? All interesting and controversial. Love it!