A rare phenomenon is happening in the Arctic region today. It features the ongoing midwinter distortion of the upper level air pressure configuration, which should have a nicely-compacted, well-rounded shape at this time of year, nothing like this image. We will especially focus on events within the space formed around the light red penetration shape in the Bering strait region:
This opening into the blue zone is wide enough to allow the jetstream pathway that regularly follows the border of the green zone to proceed deeply into the heart of the polar region before the deep green border swings around and heads back out again. The wind that traverses along this pathway is being reinforced by a second jet stream that is closely adjacent, following a regular major pathway that is delineated by the border of the blue zone:
This convoluted breakdown in the normally straighter shape of the green border creates an open highway that is now open for travel by an atmospheric river (AR). This one originated in the central Pacific, and like all other ARs has a natural proclivity to move in the direction of the pole if it can. Usually its progress would be blocked by the jet stream found on an unbroken green border, but not today. We know how to locate this river by looking at the PW map because, like all other ARs it is entirely composed of concentrated precipitable water (PW), a kind of material that is regularly measured and mapped on a globe-wide scale.
This particular river is one of the more potent ones. It has been releasing heavy rainfall throughout the course of its ocean journey, then snow as it crosses eastern Siberia, and finally more snow from the remnants that are able to traverse deeply across the sea ice:
The greenhouse energy effect produced by the heavy concentration of PW this river is composed of far outweighs that of the meager amounts of water vapor that sticks close to the surface. The added volume creates much warmer air temperatures at the surface than would normally be the case, marked by a much lower average amount of PW in the upper part of the atmosphere. Note how the warm zone extends all the way to the pole itself, just because the final remnants of the AR are strong enough to keep wielding considerable leverage over normally extremely dry surface humidity conditions.
The temperature anomalies created by this unusual situation are of interest because of the way extremes are reached on both the warm side and the cold side in nearby regions of land that are not separated by much distance. You will need extra-high magnification to get good readings off this next map. When the AR crosses over far-eastern Siberia it still has considerable strength I can see spots that have warm anomalies in the +24-28C (47F) bracket on color-code scale. Parts of Alaska and the Canadian upper northwest, meanwhile, are suffering from abnormally low amounts of overhead PW, leading to anomalies as low as minus 20-24C (40F). I see actual temperature averages of about -5C in the Siberian anomaly and -35C in the North American cold spots, with respective differences in PW values of 6-7kg and roughly 1.2 kg.
The presence of so much temperature instability deep within the polar zone favors the continuation of unusual irregularity in the upper level air pressure configuration. We may see many more days this winter that are all mixed up, similar to this one.
Carl