Monday, December 24, 2012

Warming Up, But Still Cold

Courtesy of NWS Alaska Region
Winds aloft are now southerly over most of Interior Alaska. This is both warming the airmass and brought some areas of clouds that had been over the YT into region. The NOAA-18 Polar Orbiter infrared image from 619am AST Monday tells the tale. Clouds were mostly confined to areas north of 67N, after bringing somewhat "less cold" temperatures places that had been very cold, with highs Sunday of -22F at Eagle and -30F at Tok.

The warming in valleys that don't get any wind will be slow and limited because at this point there is no deep cloud layer likely to survival crossing the Chugach and Alaska Ranges over the next few days. Any place that does get wind though will see much warmer temperatures: compare the 9am AST Monday temperature of +1F at Nenana and -29F at Fairbanks International.

So what does this mean for the cold December in Fairbanks? The average temperature (at the Airport) for the first 23 days of the month is -23.0F, and this is about the bottom. I expect the final eight days of the month will finish up averaging a bit below normal (today and Christmas Day significantly so). At this point there does not seem to be a path for December 2012 to be in the top five coldest Decembers, even just considering the Weather Bureau/NWS era (since 1929), though this will very likely be the coldest December since 1980, when the monthly mean was -24.0F. This is yet another case (like, e.g. January 2006) where the lack of extremely low temperatures is keeping the mean temperature from being super low. No calendar day this month has had a high temperature in the -40s, and the monthly minimum of -48F is pretty underwhelming by historic standards. While urban effects/ice fog are playing some role, it can't be the whole story: December 2012 minimum temperatures of -58F at Tok and Chicken, -54F at Eagle Co-op, -55F at the Fort Yukon AWOS are all historically way off the mark.

No comments:

Post a Comment