Russian Coastline Freezes in last Ten days
With the Canadian Arctic already frozen over, the action has moved to the Russian side. The image above shows East Siberian and Laptev basins filling in completely. Meanwhile on the right Kara Sea has gone from open water to nearly half of last March maximum. Kara went from 114k km2 on day 298 to 435k km2 yesterday, 47% of March max.
The graph shows MASIE reporting ice extents totaling 9.0M km2 yesterday, matching the 11 year average (2007 to 2017 inclusive). Notice that 2018 lagged the average by 900k km2 on day 296 and overcame that gap in 13 days. Presently, 2018 is tracking 300k km2 above 2007, 600k km2 more than 2012, and 1.3M km2 more than 2016. NOAA’s Sea Ice Index continutes to match MASIE through this period.
The current IMS Snow and Ice Chart shows how snow is covering Siberia completely, and has spread over northern and eastern canada. Snow cover is an important indicator for the coming Arctic and NH winter, as explained by Dr. Judah Cohen in his latest AER arctic oscillation update (here). Excerpts in italics with my bolds.
What unfolds next with the stratospheric PV (Polar Vortex) and troposphere-stratosphere coupling could be critical for determining the average temperature for the winter (December-January-February). Currently the GFS is predicting that the vertical transfer of energy from the troposphere to the stratosphere will become relatively quiet after this week. This will allow the stratospheric PV to recover and strengthen the second half of November. If the stratospheric PV becomes relatively strong and circular in shape in early December and couples to the mid and lower troposphere, this will likely result in a mild to extremely mild pattern across much of the NH including the Eastern US and northern Eurasia. At least for the Eastern US, it will be very difficult to recover from a mild start to winter and the winter temperatures would likely average mild regardless of what transpired the remainder of winter. Across northern Eurasia including Europe I think the outcome is a little more in doubt, as we saw last winter, Northern Eurasia and Europe can still average below normal for winter even with a mild start.
However an alternate path is that the energy pulse predicted for this week is not unique but is followed by subsequent pulses that further perturb the stratospheric PV. I see no evidence of this from the latest GFS forecasts, however in my opinion the NH tropospheric circulation remains favorable for subsequent PV disruptions. I think the place to watch is Siberia. As long as Siberia remains cold further energy pulses are likely with disruption to the stratospheric PV. However if Siberia turns mild for an extended period then we should expect a relatively strong PV for at least several weeks.
I would also like to note several trends. Snow cover extent remains above normal across North America. I do believe that snow cover can foreshadow the weather and the early season cold air outbreak across Eastern North America was at least preconditioned by the extensive snow cover for the entire fall this year. As long as the snow cover remains extensive and resilient, eastern North America remains at risk for subsequent cold air or Arctic outbreaks. However in the near term snow cover advance has been most impressive across Asia and with the more extensive snow cover, cold air is building across Siberia and is predicted to become more widespread. And just as I discussed above how long the snow and cold persist across Asia could be critical for the character of the winter not just locally but even remotely including the Eastern US.
via Science Matters
November 6, 2018 at 09:44AM