September 2011 – Page 2 – Illinois State Climatologist

September 21, 2011

Return of the Soil Moisture in Illinois

The natural rhythm of soil moisture in Illinois is to be abundant in spring (sometimes to the point of water standing in fields), followed by a prolonged draw-down during the growing season. Historically, soils are usually at their driest at the end of August and early September. However, soil moisture begins to recover in the September/October time frame as the temperatures cool and crops are harvested, even if rains are below average.
We are seeing some recovery in soil moisture now, according to our soil moisture network maintained at the Illinois State Water Survey. Here is the average soil moisture in the top 20 inches, expressed as a percent of what we saw on June 1 when soil moisture was very high. In other words, values near 100% show a near full recovery while values less than 100% need more rain to recover.

Belleville: 88%
Big Bend: 93%
Bondville: 57%
Brownstown: 68%
Champaign: 75%
Carbondale: 52%
DeKalb: 75%
Dixon Springs: 106%
Fairfield: 89%
Freeport: 86%
Monmouth: 55%
Olney: 78%
Peoria: 87%
Perry: 47%
Springfield: 67%
Stelle: 71%
St. Charles: 58%
Rend Lake: 71%

September 19, 2011

Monthly Precipitation during 2011 Drought

I have created a new web page that contains the monthly precipitation totals during the 2011 drought, along with links to the 1980-2010 normals (where available). I will keep this page updated as we move into fall.
Link: The 2011 Drought in Illinois

September 16, 2011

First Half of September – Cool and Dry

Based on preliminary data, the first half of September in Illinois has been cooler and drier than average. The statewide average temperature was 67.6 degrees, 2.1 degrees below average. The statewide average precipitation was 1.26 inches, 0.26 inches below average or 83 percent of average.

September 1-15 precipitation in Illinois — September 1-15, 2011, precipitation in Illinois.

September 15, 2011

October and Fall – Warm and Dry in Illinois

The NWS Climate Prediction Center has released their outlooks for October and October-December. For Illinois there is an increased chance that temperatures will be above-average in both the October and October-December time frames. Also there is an increased chance that precipitation will be below-average in both October and October-December.
As posted earlier, this forecast is consistent with the known impacts of the rejuvenated La Niña event occurring in the Pacific Basin. La Niña tends to give us warmer and drier than average conditions in fall. Last fall was a classic example of this with temperatures 1.2 degrees above average and precipitation 12% below average.

seasonal outlook — The October and October-December outlooks of temperature and precipitation from the NWS Climate Prediction Center. Click to enlarge.