Temperature

In contrast to November, which had been colder than normal for all first order stations in Alaska and brought new record lows to the Interior; December brought lots of relief with mostly above normal temperatures. Twelve of the 20 first order stations were seasonally above normal, with some exhibiting very high positive deviations. In declining order these are: Gulkana (11.1°F), Fairbanks (8.1°F), McGrath (6.9°F), Big Delta (6.1°F) and Anchorage (4.4°F). The eight stations which were seasonally below normal were much closer to their normals, with a maximal deviation of ‑3.0°F observed for Nome. The mean monthly deviation of all stations is computed at 2.0°F above the long-term climatic value.

 

Normally, the three mid winter months of December, January and February are the coldest of the year, and this is clearly demonstrated in the long-term averages. However, in 2011, 15 of the 20 first stations analyzed were colder in November than in December, which is quite unusual. In addition, one station (Kodiak) had the identical temperature of 28.4°F for both months. The greatest difference in temperature was found for Gulkana (12.7°F) and Fairbanks (12.2°F), with December being substantially warmer than November. Not only were the mean temperatures, but also the daily minima were frequently lower in November than in December. For more details, see the table below, which presents the mean values, the 30-year Normals (1991-2010), and the deviations from these normals.

 

 

 

In general, for the first two-thirds of December, above normal temperatures were observed, but during the last 10 days of the month the temperatures dropped sharply, with monthly minima observed towards the end of the month. More details are given later in the text when special events are discussed.

 

Daily temperature ranges and precipitation for Kodiak for December 2011. Note the warmer than normal first two-thirds of the month with two record warm events, and colder than normals last one-third with three record cold events.

 

 

 

Precipitation

Precipitation totals for December were generally above the average; 18 stations measured values exceeding expectation, while only two stations were below the norm, one of these just slightly so (Annette -4%). The other (Kodiak) recorded a lower value of -32%. The mean of the deviations expressed as percentages gave a value of +82%, a substantial deviation for such a large area as Alaska, or otherwise stated, Alaska was wet in December with, on average, nearly 80% additional precipitation. The most extreme values expressed as percentages above normal were found in Barrow (329%), Bettles (251%), McGrath (162%), Kotzebue (146%), Anchorage (138%) and Talkeetna (111%). For more details, see the table below:

 

 

Looking of snowfall, also expressed as percentage above or below normal, Barrow had the highest deviation (+349%), followed by Kotzebue (+205%) and Valdez (+112%) above normal. On the other side of the spectrum, Annette, in the southeast corner of Alaska, reported a deviation of -64%. It should be noted that only 15 of the 20 stations supplied snowfall observations. The high snowfall experienced in Kotzebue resulted in a mean snow depth of 42", 282% above normal.

 

Distinctive Events

At the beginning of the month, a storm hit Alaska, bringing strong winds, warm air and precipitation. The 4^th saw temperatures soar to 51°F in Big Delta, a new record for this day, smashing the old record of 40°F set in 1969. An increase in a record by 11°F is uncommon; hence this was an extraordinary event. The cause was strong southerly flow across the Alaska Range, called Chinook winds, which are gusty in nature. Chinook winds are created when the air is cooled moist-adiabatical as it rises due to precipitation on the south side of the Alaska Range, but descends dry-adiabatical on the north side of the range. As the dry adiabatical rate is higher than the moist-adiabatic rate, the air arrives warmer in Interior Alaska than it started out with on the south side of the Range.

 

As there were a large number of new daily records, we are not able to discuss all of these individually, but make only some remarks on a few extra-ordinary occurrences, admittedly a somewhat subjective assessment. However, all the records are listed in the table below in which the temperatures are given in °F, snowfall and precipitation in inches and atmospheric pressure in inches of mercury.

 

The storm that moved over Alaska at the beginning of the month brought on the 3^rd December at St. Paul Island in the Southern Bering Sea a wind gust of 74 mph, and one day later a gust of 118 mph was recorded at Glen Alps near Anchorage. On the 4^th, the maximum temperature of +47°F was recorded in Fairbanks - a balmy temperature for Interior Alaska in winter. A mean temperature for the day was 37°F, a rare event, as mean daily temperatures above freezing are infrequent in deep winter in Fairbanks. Also on the 4^th, at Barrow in Northern Alaska, average wind speeds were recorded at 30 mph, with gusts exceeding 50 mph. These are high and uncommon values, however they do not represent new records. More unique was the precipitation record of Barrow with 0.33" (water-equivalent), beating the previous record for the 4^th December of 0.19 set in 1922. This was associated with a new snowfall record of 6.5", surpassing the old record of 2.5" set also on this day in 1922. Both these values are in fact new records for all days of December. The previously highest precipitation amount for any day in December had occurred on 13^th December 1930 with 0.26", and the highest amount of snowfall (5.0") had been observed on 29^th December 1922. Also Nome and Kotzebue reported new snowfall and precipitation records during the first part of the month (see table). Further, in Valdez 2.80 of precipitation were recorded on the 4^th, which more than doubled the old record of 1.37 set in 1984. Interestingly, this was associated with a record high in atmospheric pressure of 30.55. Normally, large precipitation amounts are associated with low-pressure systems. The total monthly amount of snowfall in Valdez was 144, a new record for the month, surpassing the old record of 137 set in 1991.

December Records

 

 

Date	Station	Element	New Record	Old Record	Year of old Record
12/02/11	Kodiak	High Temperature	47	46	1992
12/03/11	King Salmon	High Temperature	51	48	2002
12/03/11	Kotzebue	Snowfall	5	4.9	2010
12/03/11	Nome	Snowfall	6.5	6.2	1979
12/03/11	Big Delta	High Temperature	46	42	1963
12/03/11	UAF West Ridge	High Temperature	45	44	1948
12/03/11	North Pole	High Temperature	49	47	1968
12/04/11	Barrow	Precipitation	0.33	0.19	1922
12/04/11	Barrow	Snowfall	6.5	2.5	1922
12/04/11	King Salmon	High Temperature	46	45	2008
12/04/11	Valdez	Precipitation	2.8	1.37	1984
12/04/11	Valdez	Pressure	30.55	30.41	2000
12/04/11	Kotzebue	Snowfall	3	2.1	1978
12/04/11	Big Delta	High Temperature	51	40	1969
12/06/11	Valdez	Pressure	30.57	30.41	2000
12/06/11	Kotzebue	Snowfall	2.6	2	1997
12/06/11	Nome	Snowfall	4.1	3.9	1993
12/07/11	Kotzebue	Precipitation	0.32	0.27	2002
12/07/11	Kotzebue	Snowfall	6.5	3	2002
12/07/11	Nome	Snowfall	5.6	4.4	1981
12/08/11	Kotzebue	Precipitation	0.34	0.2	1981
12/08/11	Kotzebue	Snowfall	6	2.4	1987
12/08/11	Valdez	Snowfall	12	11.9	1985
12/10/11	Nome	Snowfall	4.5	4.1	2007
12/10/11	Kotzebue	Snowfall	5.7	2.1	1978
12/10/11	Kotzebue	Precipitation	0.29	0.14	2007
12/11/11	Valdez	Snow Depth	20.3	14.9	2001
12/11/11	Valdez	High Temperature	40	40	2002
12/11/11	King Salmon	Snowfall	10	3	1963
12/11/11	Kotzebue	Precipitation	0.16	0.12	1950
12/11/11	Valdez	High Temperature	40	40	2002
12/11/11	Valdez	Snowfall	20.3	14.9	2001
12/13/11	Bettles	Snowfall	4	4	1955
12/17/11	Valdez	Snowfall	20	18.6	1978
12/18/11	Kodiak	High Temperature	44	44	1985
12/27/11	Kodiak	Low Temperature	4	4	1951
12/28/11	Cold Bay	Low Temperature	3	3
12/30/11	King Salmon	Low Temperature	-29	-25	1997
12/30/11	Kodiak	Low Temperature	3	5	2006
12/31/11	Kodiak	Low Temperature	-3	2	1974

 

 

This information consists of preliminary climatological data compiled by the Alaska Climate Research Center, Geophysical Institute, University of Alaska Fairbanks. This summary is based on the 20 first order stations in Alaska operated by the National Weather Service. Extreme events of other stations are also mentioned. It should be noted that the new climate normals for the time period of 1981-2010 are applied for the calculations of the deviations, and they can be slightly different from the old normals (1971-2000), which were in use up until end of July 2011.