Wow, the heavy rains just keep on coming in July. Last night it was central Illinois (left panel), and the day before that was northern Illinois (right panel). Click to enlarge maps.
It’s no surprise then that Illinois has had abundant rainfall in July as shown in the figure below with total rainfall (left panel) and departures from normal (right panel). Like the children of Lake Wobegon, all of Illinois is above average on rainfall (except for a few small pockets), as denoted by the shades of green and blue in the right panel.
Through yesterday, the statewide average rainfall was 6 inches, which is approximately double the normal rainfall for July thus far. It also puts us at number 8 in the top ten list of the wettest Julys on record for Illinois with more rain on the way this week. It would be hard to beat the top two spots with the current NWS forecast, but moving all the way up to #3 is possible.
Top Ten Wettest Julys in Illinois
- 1958 with 8.10″
- 1992 with 7.61″
- 1915 with 6.73″
- 1993 with 6.61″
- 1981 with 6.46″
- 1969 with 6.31″
- 1896 with 6.11″
- 2016 with 6″
- 1907 with 5.97″
- 2008 with 5.91″
The Climate Prediction Center released their latest monthly and seasonal forecast today. We are still in between El Niño and La Niña. According to CPC, “La Niña is favored to develop during August – October 2016, with about a 55-60% chance of La Niña during the fall and winter 2016-17.”
For August, the southern half of Illinois has an increased chance of above-normal temperatures (top row in the figure). The northern half has “EC” or equal chance of above, below, or near-normal temperatures. Western Illinois is part of a larger area in the western Corn Belt with an increased chance of above-normal rainfall. The rest of Illinois is in the “EC” category.
For August-October (bottom row), the entire US has an increased chance of above-normal temperatures. Illinois has equal chances of above, below, and near-normal precipitation. The increased chance of above-normal temperatures for Illinois continues in the September-November and October-December outlooks before it goes away this winter.
So bottom line – possibly wetter in western IL and warmer in southern IL in August (compared to normal) and a possibly warmer fall. Personally, I wouldn’t pay too much attention to this winter’s forecast until this La Niña shows up or not.
Temperature and precipitation normals refer to the 1981-2010 averages.
The thunder is rumbling outside my window as I write this.Here is the radar/rain-gauge estimated rainfall for July (first map). Areas in green received only 1 to 2 inches, yellow 2 to 3 inches, oranges and reds 4 to 10 inches.
The second map shows these rains as a departure from normal for the first 18 days of July. There are several bands of above-normal rainfall across north-central and central Illinois. But the largest rainfall departures of plus 4 to 8 inches are in counties south of Carbondale.
The three wettest spots in Illinois as of this morning are Rosiclare wth 10.70 inches, Smithland Lock and Dam with 9.66 inches, and Carbondale with 9.49 inches. One of the driest spots in the state is Mundelein (Lake County) with 0.91 inches.
Illinois is not the only wet state in July. Substantial rains have fallen across Iowa, Missouri, Kentucky, and much of Indiani.
Departure from Normal
Illinois is off to a warm start to 2016. The first half of the year averaged 49.7 degrees, 2.8 degrees above normal and the 7th warmest January-June on record. Every month except May was above-normal for temperatures. Statewide records go back to 1895. Normals are represented by the 1981-2010 average.
The statewide average precipitation for the first half of 2016 was 16.24 inches, 3.59 inches below normal and the 26th driest on record. Every month except March was below-normal for precipitation. Most of the dryness in 2016 was centered in western Illinois. We would have had more drought problems in 2016, except that precipitation in November and December of 2015 was 6 inches above normal, leaving soils saturated and river, streams, and wells fully recharged.
Here are the monthly departures for temperature and precipitation for Illinois in 2016.
I hear the joke about meteorologists all the time – “I wish I got paid for being right only half the time”. Despite the misperception by some, the forecasting skills at the NWS offices are very good. Skills have improved over the years, not only for routine forecasts of temperature and precipitation, but also for critical severe weather. There are still meteorological surprises every once in awhile, but most of the “it came without warning” cases did indeed have warnings associated with them.
Here is an example where the National Weather Service did a good job of forecasting when and where the rain would fall from this last system over a 5-day period. It is a product called the quantitative precipitation forecast (QPF). I’ve really been impressed with this product over the past few years and rely on it routinely. The first map is the potential 5-day rainfall totals made on July 1. The second map is the actual 5-day rainfall totals over the forecasted period (July 1-5).
Unfortunately, the color schemes is different between the two maps. In general, the areas in red in the first map were expected to receive 2 to 5 inches of rain, while the areas in yellow and red in the second map did receive 2 to 5 inches of rain. Overall, the amounts and overall pattern match up well. Kudos to the folks at NWS.
By the way, more rain is likely on the way over the next five days (last map), with amounts of 1 to 2 inches expected across Illinois.
You can monitor the NWS quantitative precipitation forecasts (QPF) at http://www.wpc.ncep.noaa.gov/qpf/day1-7.shtml
Forecasted – next 5 days.
Temperature: June in Illinois ended up being warmer and drier than normal for most of the state. The statewide average temperature was 74.8 degrees, which was 2.9 degrees above normal and the 14th warmest June on record. DuQuoin had the warmest reading of the state when they reached 102 on June 16.
Precipitation: The statewide average rainfall for June was 3.04 inches, 1.17 inches below normal and the 30th driest June on record. However, that doesn’t tell the whole story. Western and southern Illinois were much drier with many locations reporting less than an inch of rainfall. One of the driest totals was at Pittsfield with only 0.13 inches of rain for the entire month. Meanwhile eastern and northern Illinois were much wetter with amounts of 3 to 5 inches common. A few spots were even wetter. For example, the wettest monthly total was Streator with 9.71 inches of rain.
Much of western and southern Illinois has been dry in June. In the first map below, areas in the darker shades of orange are 2 to 4 inches below normal on rainfall for the month. Meanwhile, areas in eastern-central and northern Illinois have been near to above normal. A few areas have been downright wet (shaded in blue). Temperatures have been running 4 to 5 degrees above normal.
However, this picture could change dramatically with the National Weather Service models indicating that up to 6 inches of rain could potentially fall over the next 5 days (second map). While that area certainly needs rain, it is almost too much of a good thing. Depending on how fast the rain falls, some of it will likely run off instead of having a chance of soaking in.
Here is the 5-day precipitation forecast showing the potential rainfall totals. Areas shaded in red are expected to received between 2.5 and 5.0 inches.