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    Signs of Winter Abound Across the Northern Hemisphere

    December 05, 2012, 6:09:20 AM EST

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    While much of the United States and eastern Canada has had persistent warmth, a lack of snow or both, cold has begun to romp elsewhere in the Northern Hemisphere. Here are a few examples.

    North America:

    Northwestern and north-central North America have registered some noteworthy cold, especially since late November.

    In Alaska, the last week brought temperature departures of as many as 40 degrees F below normal in southeastern interior Alaska. As many as five days registered 50 degrees F below zero or lower in the area of Tok, along the Alaska Highway, and in more isolated Chicken, near the Yukon border.

    Yukon bore the brunt of Canada's share of the early December arctic outbreak, with no fewer than two nights of 50 degrees below zero F. Mayo reached 53 degrees F below zero, whereas Faro bottomed at 52 degrees below zero F.

    Numerical forecast models show that arctic cold will dominate the weather, apart from some short-term warming Sunday and Monday, in northwestern North America for the next two weeks and beyond.


    590x475_12051534_screen-shot-2012-12-05-at-10

    Forecast of temperature departure from normal, in degrees F, for North America, valid Dec. 19, 2012. This is from the GFS 2-meter "ensemble mean" temperature forecast of 0000 UTC Wednesday, Dec. 5. The forecast of at least 21 degrees F a fortnight hence is remarkable, hinting that continued bitter cold is a "lock," as odds go. (Penn State ewall website)


    East Asia:

    Bitter cold has settled over a vast swath of north Asia. When this happens, it inevitably breaks out southward and eastward, and this is what has begun to happen as of early December.

    First, to show what kind of cold is on offer, here are some recent low temperatures.

    As early as Dec. 2, Tompo dipped to at least 57 degrees below zero. Tompo is east of Yakutsk in Yakutiya, home of the Siberian "pole of cold."

    In Vekhoyansk, at the heart of the "pole," the temperature went below 50 degrees below zero F on Dec. 1 and held here until early Wednesday, Dec. 5, bottoming no higher than 56 degrees below zero.

    Since Dec. 3, the core of lowest temperature has shifted westward to a sparsely settled swath of the Mid Siberian Upland. Yaral'in had at least 30 hours, through Wednesday, with temperature between 57 and 59 degrees below zero F. This stretch was ongoing as of Wednesday "night" (it is essentially night all day at this latitude in December).

    Suhana and Olenek have had readings 50 degrees F or more below zero since Monday, Dec. 3. Olenek reached 58 degrees below zero Wednesday.

    More impressively, Dzalinda began its 50 degrees below zero F stint on Dec. 2, diving as low as 58 degrees below zero, warming only to 53 degrees below zero Wednesday.

    Wednesday, another low of 59 degrees below zero was set at Vivi, along the Lower Tunguska River.


    590x526_12051544_screen-shot-2012-12-05-at-10

    A sampling of current temperatures, as of 1200 UTC Wednesday, Dec. 5, 2012, in north Asia (Siberian Russia). The coldest area is framed by the lower Yenisey (left) and Lena (right) rivers, as well as the Arctic coast. Lake Baykal at bottom.


    Arctic air masses, wherever they are found, tend to flow towards warmth, which would typically be towards the south and east in the Northern Hemisphere. The pressure is usually anomalously high, so the flow is largely driven by gravity.

    Since a mountain barrier, bulwarked by the Highland of Tibet, blocks southward movement from north-central Siberia, arctic air masses here flow mostly towards the southeast; sometimes they target Central Asia or even hop the Ural Mountains to northern Europe.

    As of early December, wintry cold has begun to be felt over northern and northeastern China, the Korean Peninsula and even Japan.

    Wednesday brought the first widespread snow to Korea, including much of northern and western South Korea. By evening, 3 inches covered Seoul.

    Snow in western Korea is often the result of cold air out of northern Asia, crossing the Yellow Sea by way of northeastern China. Thusly moistened, the cold flow of air breeds "sea-effect" snow, sometimes heavy south in areas southward from Inchon.

    Northern Japan has also had some early shots of cold, although snow season here is normally held off, owing to the lingering warmth of the Sea of Japan.

    Going forward, a series of strong lows (or storms) in the Kuril Island/Sakhalin Island region will shunt a strengthened flow of arctic air southeastward out of Siberia, crossing Mongolia and northeastern China to Korea and Japan. I look for even more outbreaks of sea-effect snow, both in western Korea and all along the western side of Japan.

    Europe:

    November was mild to normally cool throughout Europe. Wet, moreover, in some areas, as many residents of the U.K. can attest.

    A shift to cold began last week, before the end of the month, and has gathered momentum during the first days of December.

    Although the cold as of Wednesday has not been severe, outside of Scandinavia and Finland, it has been enough to foster early snowcover along, north and east of the Alps.

    Helsinki, Finland, has turned truly cold, as Wednesday's low of 3 degrees below zero F is almost 30 degrees below normal for the date.

    Going forward, blocking of the normal eastward flow of Atlantic warmth, together with the low ebb of incoming solar energy, will allow cold to persist, if not sharpen, across Europe west of Russia, through at least mid-December.

    Undoubtedly, Europe snowcover will persist, expand and deepen, once again favoring areas along, north and east of the Alps, but the Balkan Peninsula should also see a big boost in snowcover.


    590x504_12051528_screen-shot-2012-12-05-at-10

    A numerical model forecast of snow depth for Europe, valid 0000 UTC Dec. 12, 2012. Standing out is a broad swath from the Balkan Peninsula northeast to Ukraine and Belarus, where the forecast is for a marked deepening and expansion of snowcover versus Wednesday, Dec. 5. Also, westward spread of light snow cover over France and even England.

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