Precipitation and Temperatures in December for Illinois
Based on data through December 21, the statewide average precipitation was 2.9 inches, 1.1 inches above average.
The statewide average temperature was 35.6 °F, 4.5 °F above average. That stands in stark contrast to last December when the average temperature was 21.8 °F through this date. Put another way, we are about 13.8 °F warmer this December than last December through the 21st of the month.
Where is the snow?
With the warmer temperatures this December, we have seen lots of rain but not much snow. The two maps show the snowfall for the period of December 1-21, 2011 and the same period for December 2010. Snowfall is lacking throughout much of the Midwest except for the one winter storm earlier this week. Southeast Illinois has reported no snowfall in December while much of the rest of state has seen two inches or less. By this time last December (second map), much of Illinois and the upper Midwest had experienced 10-25 inches of snow.
We just updated the odds of a white Christmas in Illinois, based on 1981-2010 data. We created the map using stations that had at least 20 years of snowfall data during the 1981-2010 period. A year with a white Christmas was defined as having measurable snow on the ground on December 25.
There can be large differences from site to site. Snowfall is notoriously difficult to measures with two nearby sites having different results due to exposure to sun and wind. In general, the odds are about 40-50 percent in the northern third of Illinois, 20-40 percent in central Illinois, and 0-20 percent in southern Illinois.
The NWS released their new monthly and seasonal outlooks today. For January they are calling for an increased chance of above average temperatures for Illinois. Much of Illinois has an increased chance of above average precipitation as well.
The January-March outlook for Illinois is for an increased chance of above average precipitation and above average temperatures.
If you were not looking forward to a repeat of last year’s winter, this is good news. An increased chance of above average temperatures does not mean you will be playing golf in Illinois in mid-January. But it puts you in better shape than January 2011, which came in at 3 degrees below average.
Why the more upbeat forecast? The current La Niña event occurring in the Pacific has been much weaker than expected, and forecasted to stay so for the rest of the winter. These new forecasts for temperature and precipitation reflect the weaker La Niña event. As noted in an earlier post, November was the sixth wettest and ninth warmest on record. And the first half of December has been above average on temperature and precipitation in most locations.
This year has been noteworthy for the number of extreme events across the U.S. In fact, we have had 12 disasters that have exceeded $1 billion in losses each in 2011. We also experienced some $50 billion in total losses for the year. And that is with a fairly quiet hurricane season. Some of those billion dollar disasters had direct impacts on Illinois, including the February blizzard, and the spring flooding.
You can read more about the major disasters this year at http://www.noaa.gov/extreme2011/
NOAA is promoting a new concept called a “Weather Ready Nation”. The idea is to be better prepared and to better respond to weather/climate disasters. This involves better forecasts, better dissemination of forecasts, and closer working relationships among federal, state, and local partners. I’m sure we will hear more about this in coming months.
[Update: The method used to generate the bar-plot part of this graph is apparently flawed. While the line plots show both actual damages and damages adjusted for the Consumer Price Index, they did not make a similar adjustment on the number of 1 billion dollar event. As a result, the number of 1 billion dollar events will climb as prices climb (for example, the destroyed $100k home in 1980 would be worth $250k in 2011). See http://rogerpielkejr.blogspot.com/2012/01/bad-economics-at-noaa.html.]
NOAA has revised their winter outlook for the U.S, according to a recent post on their ClimateWatch Magazine. An earlier outlook had northern Illinois with chances of well below normal temperatures. The new outlook (below) has pulled the colder outlook out of Illinois as well as expanded the area in the southern half of Illinois with an increased chance of above normal temperatures. So overall, a milder winter is expected in terms of temperatures.
The precipitation outlook for this winter remains unchanged for Illinois. Most of the state, except for far western Illinois, has an increased chance of above normal precipitation. Unfortunately, NOAA does not do a snowfall forecast. Research indicates that the Great Lakes region has better chances for above normal snowfall during past La Niña events. However, the weaker than expected La Niña event this winter and the slow start to the snowfall season suggest that the pattern of increased snowfall during La Niña winters may not pan out this year.
The winter outlook covers the period of December-February, the heart of the winter weather season in most of the U.S.
November was an interesting month in Illinois. The four outstanding features were:
the sixth wettest November on record with a statewide average precipitation amount of 5.23 inches, 1.9 inches above average; several sites in southern Illinois had over 9 inches of rain, including Cairo with 9.92 inches (the most of any site in the state);
the end of drought for western and central Illinois as a result of the above average rainfall in November;
the ninth warmest November on record with a statewide average temperature of 45.3 degrees, 3.6 degrees above average;
the snowiest spot in the state was in far southern Illinois, 2.5 inches of snow fell by the morning of November 30 at Grand Chain Dam on the Ohio River. A few sites in northern Illinois reported an inch or less of snow. As was noted in an earlier post, the “normal” snowfall for November ranges from 1 to 2 inches in northern Illinois to no snowfall in southern Illinois – the near opposite of this year. It is just another example of Illinois weather “not playing by the rules.”
Statewide records of temperature and precipitation go back to 1895. Here are the precipitation and snowfall maps for November.