Evo jedne dobre, opširne analize i projekcija za dalji razvoj trenutne situacije, kome nije dosadno da krcka ovaj tekst na engleskom (boldovao sam zanimljivije djelove) :
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The AO is currently positive and is predicted to trend negative but still remain near neutral.
The negative AO trend is reflective of the model forecast of initial low pressure/geopotential heights over the North Atlantic side of the Arctic transitioning to more high pressure/geopotential heights. The models are predicting that the dominant geopotential height rise will be near Scandinavia and the Barents Kara Seas with downstream troughing over East Asia. This has significant implications for the strength of the polar vortex in January.
With high pressure strengthening in the Barents Kara Seas, temperatures should turn cold first across Siberia and Central Asia and then eventually across East Asia. However for now, blocking across northwest Asia will prevent the westward flow of cold air from Siberia into Europe.
Models are also predicting rising pressure/geopotential heights across western North America, in part in response to some initial perturbing of the polar vortex. This will likely result in deepening troughing across eastern North America and a cooling trend in temperatures for the Eastern United States.
The atmosphere is currently experiencing a pulse of energy transfer from the troposphere to the stratosphere that will last the remainder of the week.
The models are predicting a second pulse during the first week of January and we continue to anticipate even further energy transfer. This will begin to perturb or disturb the polar vortex starting this week, which will likely peak sometime in January. High snow cover and low sea ice this past fall favored a weakening of the polar vortex preferentially in January. The latest weather model forecasts increase our confidence in a weakening or perturbed polar vortex in January (the GFS more so than the ECMWF and this needs to be closely monitored). Following the polar vortex weakening the negative phase of the AO, cold temperatures and potentially an increase in snowstorms is favored across the Northern Hemisphere mid-latitudes including the Eastern United States, Europe and East Asia.
Impacts
Currently the AO remains positive with low geopotential heights dominating the high latitudes and high geopotential heights across the mid-latitudes. This pattern has resulted in very mild temperatures across northern Europe, the Eastern United States and to a lesser degree East Asia. However Siberia and Central Asia have turned cold, which has important implications for our AO forecast for mid to late winter as a
cold east Eurasia/warm west Eurasia is favorable for increased energy transfer from the troposphere to the stratospheric polar vortex.Low pressure/geopotential heights dominate the Arctic basin and the high latitudes of both the North Pacific and North Atlantic, resulting in a strongly positive AO. In contrast the mid-latitudes are dominated by high pressure/geopotential heights. Initially the three dominant areas of positive geopotential height anomalies are centered over the Eastern United States, Central Europe and East Asia. The ridging dominating the population centers of the Northern Hemisphere (NH) has resulted in mild to very mild temperatures for the Eastern United States, Europe and to a lesser degree East Asia. Exceptions to the high geopotential heights over the continents are troughs or low geopotential heights in Western Siberia/Central Asia and Western North America. This has resulted in cold temperatures for Siberia, Central Asia, Alaska and northwest Canada. However with time, the models are suggesting that the regions of dominant positive geopotential height anomalies will be centered in western North America, Scandinavia/Barents-Kara Seas and East Asia. The ridging in western North America will help to deepen lower geopotential heights and troughing across eastern North America. Therefore we expect a gradual return of more typical winter weather for the Eastern United States. Similarly for East Asia potentially colder weather is likely as cold air in nearby regions of Siberia and Central Asia filters into the region. The region least likely to see a near-term transition to cold temperatures is Northern Europe and northwest Asia. The predicted geopotential heights rise over northern Scandinavia and the Barents-Kara Seas will block the westerly flow of air from Siberia towards Europe and allowing a more mild maritime flow of air to dominate European weather.
Longer term we continue to expect that variability in the polar vortex to strongly influence NH weather patterns. It is becoming less of a question if the polar vortex weakens and more of a question of when.
A robust transfer of energy from the troposphere to the stratosphere is underway and will continue the entire week. However with the polar vortex at or near record strength, much of the energy is currently being deflected. Still enough energy is absorbed to stretch the polar vortex so as to increase cross-polar flow from Siberia into eastern North America and commence a cooling trend. The models are now predicting a second pulse of energy the first week of January. This is likely to perturb the polar vortex even further. And we anticipate further pulses of energy. The predicted circulation pattern of ridging in the Barents-Kara Seas/Northwest Eurasia and troughing in East Asia/the North Pacific is optimal for exciting energy pulses from the troposphere to be absorbed into the stratospheric polar vortex. Therefore we continue to anticipate even more pulses of energy transfer into mid-January. The duration and the strength of this energy transfer will strongly influence the variability of the polar vortex. We continue to anticipate that the polar vortex will be sufficiently perturbed/weakened to allow colder weather to spread over the Northern Hemisphere mid-latitudes starting in January.
Still, If the energy transfer is not sufficiently strong over the next month or so to weaken the polar vortex, then the winter AO is likely to average positive in the mean and a mild weather pattern will dominate the mid-latitude continents for the remainder of the winter. "
https://www.aer.com/science-research/climate-weather/arctic-oscillation
