The U.S. Drought Monitor released the latest drought map, showing that the “severe” D2 drought has expanded across much of northern Illinois. Only an area in the northeast part of the state remains in moderate drought (first figure).
The Climate Prediction Center also released their drought outlook today. They expect the drought in the central U.S. to persist over the next 3 months (second figure).
Higher Risk of Hot, Dry Conditions for August and Fall
The Climate Prediction Center delivered more bad news for Illinois today. Their outlook for August includes an increased chance of above-normal temperatures across Illinois and much of the U.S. It includes an increased chance of below-normal precipitation for all of Illinois and much of the Midwest.
Their outlook for the 3-month period for August-October includes an increased chance of above-normal temperatures for Illinois and much of the eastern two-thirds of the U.S. and below-normal precipitation for Illinois and much of the Midwest.
Comparison of 2012 to 1988 in Illinois
Precipitation
The first figure shows the statewide precipitation departures by month for both 1988 (blue) and 2012 (red) in Illinois, using the 1981-2010 average as normal. There are several interesting features:
- the period from January to March was actually drier in 2012 than 1988;
- the 1988 drought started abruptly in April with dramatically less precipitation; April 2012 was dry but less so than February or March;
- the precipitation departures in May and June of 1988 were slightly more severe (1/2 inch drier for each month) than 2012;
- by the end of June, the precipitation deficit was 7.83 inches in 1988 and 7.25 inches in 2012;
- while less severe than June, precipitation continued to be below normal from July to October in 1988; real relief did not arrive until November.
Monthly precipitation departure in Illinois for 1988 (blue) and 2012 (red). Click to enlarge.
Temperature
The next figure shows the statewide temperature departures by month for both 1988 (blue) and 2012 (red) in Illinois. There are several interesting features here as well:
- temperatures from January to March in 2012 were much warmer than normal while they were much cooler than normal in 1988; in fact, January and February was significantly colder in 1988;
- temperatures in April, May, and June were all above normal in 2012;
- it wasn’t until May that temperatures in 1988 started to be warmer than normal;
- warmer than normal temperatures continue in 1988 until October.
Summary
In summary, the 1988 drought started later than the 2012 drought, but once started it was more intense in the April-June period. However, temperatures were much warmer in 2012 than in 1988. In my opinion, those two factors balance out, making the the 1988 and 2012 very comparable at this point.
How is July unfolding? For the first 17 days of July, the precipitation amounts are identical between 1988 and 2012 at 0.8 inches (40% of normal for that period). However, temperatures for the first 17 days of July 1988 averaged 79.1 degrees, 3.3 degrees above normal. For this July, the average temperature was 82.3 degrees, 6.5 degrees above normal.
Southern Illinois: Tale of Extreme Back to Back Years
The conditions in southern Illinois could not be farther apart than the last two years. Last year finished as being one the wettest on record while this year is shaping up to be one of the driest on record.
Here are some startling statistics for Carbondale. From January 1 to July 17 this year, Carbondale has received only 12.66 inches. For the same period last year, Carbondale had already received 44.62 inches. That is about four times more rainfall last year than this year up to this point. Carbondale went on to accumulate 69.97 inches in 2011, making it the second wettest year in Carbondale history. The table below shows the monthly rainfall in inches for 2011, 2012, and normal. Below the table are maps showing the year to date rainfall in 2011 and 2012.
Total69.9712.6647.17
| Month | 2011 | 2012 | Normal |
| January | 1.54 | 3.02 | 3.06 |
| February | 3.93 | 1.74 | 3.08 |
| March | 5.34 | 3.92 | 4.15 |
| April | 14.84 | 2.17 | 4.45 |
| May | 7.41 | 0.40 | 5.37 |
| June | 7.93 | 0.99 | 4.51 |
| July | 4.97 | 0.42* | 3.66 |
| August | 1.37 | – | 3.26 |
| September | 7.41 | – | 3.14 |
| October | 1.89 | – | 3.81 |
| November | 8.21 | – | 4.63 |
| December | 5.13 | – | 4.05 |
| Total | 69.97 | 12.66 | 47.17 |
*as of July 17, 2012
