NCAR - Record-Smashing Canadian Arctic Warmth - Largest Monthly Anomaly 37.8F Above Historic Average

[hatrack]

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Just how mild has it been? The map at right shows departures from average surface temperatures for the period from 17 December 2010 to 15 January 2011, as calculated by NOAA’s Earth Systems Research Laboratory. The blue blip along the southeast U.S. coast indicates readings between 3°C and 6°C (5.4–10.8°F) below average for the 30-day period as a whole. That’s noteworthy—and in fact, it was the coldest December in more than a century of record-keeping across south Florida (see PDF summary). Blue also shows up across the UK, where December averaged 5.2°C (9.4°F) below normal.

What really jumps out, though, is a blob of green, yellow, orange, and red covering a major swath of northern and eastern Canada. The largest anomalies here exceed 21°C (37.8°F) above average, which are very large values to be sustained for an entire month.

To put this picture into even sharper focus, let’s take a look at Coral Harbour, located at the northwest corner of Hudson Bay in the province of Nunavut. On a typical mid-January day, the town drops to a low of –34°C (–29.2°F) and reaches a high of just -26°C (–14.8°F). Compare that to what Coral Harbour actually experienced in the first twelve days of January 2011, as reported by Environment Canada (see table at left).

* After New Year’s Day, the town went 11 days without getting down to its average daily high.
* On the 6th of the month, the low temperature was –3.7°C (25.3°F). That’s a remarkable 30°C (54°F) above average.
* On both the 5th and 6th, Coral Harbor inched above the freezing mark. Before this year, temperatures above 0°C (32°F) had never been recorded in the entire three months of January, February, and March.

The extremes have been just as impressive when you look high in the atmosphere above these areas. Typically the midpoint of the atmosphere’s mass—the 500-millibar (500 hPa) level—rests around 5 kilometers (3 miles) above sea level during the Arctic midwinter. In mid-December, a vast bubble of high pressure formed in the vicinity of Greenland. At the center of this high, the 500-mb surface rose to more than 5.8 kilometers, a sign of remarkably mild air below. Stu Ostro (The Weather Channel) found that this was the most extreme 500-mb anomaly anywhere on the planet in weather analyses dating back to 1948. Details are at the conclusion of Ostro’s year-end blog post. Farther west, a separate monster high developed over Alaska last week. According to Richard Thoman (National Weather Service, Fairbanks), the 500-mb height over both Nome and Kotzebue rose to 582 decameters (5.82 km). That’s not only a January record: those are the highest values ever observed at those points outside of June, July, and August.

EDIT

http://www2.ucar.edu/currents/cold-comfort-canadas-record-smashing-mildness