The winter of 2011-2012 has taken on a completely different character compared to the previous few winters which started off cold. After the 6th warmest December on record (tie), January 2012 concluded with an average temperature 4.8 degrees warmer than normal (1981-2000 normal), the 17th warmest on record (tied with 1876) since 1871.
Precipitation was 0.62” below normal with a notable 3.9” snowfall deficit.
2012 broke the string of three straight colder than average Januarys (from 2009-2011), and was more comparable to the mild Januarys of 2006-2008. 2012’s 40.8 average temperature in January at Reagan National was slightly warmer than 2007’s 40.7 and 2008’s 40.0, but considerably cooler than 2006’s 43.1.
None of these recent warm years compare to the warmest January on record: the torching 48.0 from January 1950. That was a full 12 degrees above normal - a stunning anomaly for a monthly average.
You can see how much warmer January 1950 was compared to this year in the daily average comparison chart above.
Yesterday’s high of 66 brought the monthly total of 60+ days to 6. In 1950, we had 14, including an incredible 6 days of 70 or higher.
2012 tied for 13th (with six other years) for most 60 degree days.
Here are the 60+ counts for other years (years since 2000 in bold):
1890, 1916, 1974, 2006: 9
1874, 1876, 1937, 1947: 7
1949, 1951, 1952, 1967, 1990, 2007, 2012: 6
Where did temperatures spend most of their time in January? The month experienced significant volatility at times as the coldest reading of 17 on January 4 was followed by the month’s warmest reading of 68 only three days later on January 7. Highs in the 40s marginally edged out highs in the 50s for January. Lows concentrated in the 30s but about one third of the month’s days had lows in the colder 20s.
In terms of records, Dulles hoarded them all, setting three for warm temperatures. On January 26 and 27, it tied the records for warmest low temperature (from 1967 and 1974), only dropping to 40 and 39. And on January 31, it set a new high temperature record of 66 (old record 65 from 1993).
Like November and December, we saw a lack of “high-latitude blocking”. This usually takes the form of strong high pressure around Alaska, the North Pole, and/or around Greenland which sends cold air south. Not until the very end of January did we start to see some Arctic and Greenland high pressure ridges forming, but so far, they have mostly sent cold air to Europe. The Lower 48 mainly saw a flood of mild air from the Pacific ocean, enhanced by warm phases of a feature known as the Madden-Julian Oscillation (MJO) that Greg discussed yesterday. In contrast, a persistent cold vortex in the vicinity Alaska kept it in the deep freeze with record cold, as Jason reported yesterday.
A look ahead to February
As both Wes and Greg wrote recently, some signs of changes ahead could give us better opportunities for at least some cold and even more snow in the weeks ahead. Wes’ former employer, the National Weather Service is less enthused as they favor a warm month with little guidance on precipitation (equal chances of anything happening).
The National Weather Service publishes nice monthly assessments usually within a week of the close of each month (should be available shortly):
Historical Washington, DC data provided by Speedwell Weather and NOAA
(Jason Samenow and Ian Livingston contributed to this post)