I am a little late in post this, but March 18, 2015, marked the 90th anniversary of the Tri-State Tornado that struck Missouri, Illinois, and Indiana, on March 18, 1925 (map below).
This was the deadliest tornado in U.S. history with 695 lives lost and occurred long before there were systematic forecasts and warnings of tornadoes. While it predated the common F-scale used to measure tornadoes, it was considered by experts to be an F-5 event. A few years ago there was a push to decide if this was one continuous track or not by examining all the evidence and interviewing survivors. It was hard to decide since there was no weather radar to track the storm. Some of the areas were very sparsely populated, leaving little documentation on the possible track.
Figure from Wilson, John W., and Stanley A. Changnon, Jr. (1971). Illinois Tornadoes. Circular 103. Illinois State Water Survey: Urbana-Champaign, IL.
Click to enlarge. Source NOAA Storm Prediction Center.
So far the 2015 tornado season in Illinois and the rest of tornado alley is incredibly quiet. There are no tornadoes to report this year, except in the far Southeast and one in California. However, this quiet start is no reason to relax if the past few years are a guide.
Historically, the heart of the Illinois tornado season is March to June with two-thirds of our tornadoes occurring during those months. However, in the last few years, we have had more tornadoes occur outside of this period than inside.
And a lot of these tornadoes have been concentrated in just a few days of the year. In fact, 69 percent of the tornadoes in 2012-14 occurred on just 5 days. These high concentrations can put extra strain on forecasting, warning, and recovery operations.
Here is how 2012, 2013, and 2014 looked, compared to the historical averages. Continue reading
In the last 7 days, Illinois has received 1 to 3 inches south of Interstate 70 (map below). Most of that came from storms last weekend. However, the precipitation amounts dropped off rapidly northward in Illinois. Areas in the northern third of the state received little to no precipitation. We are keeping a close eye on the continuing dry conditions in northern Illinois. That area has been persistently dry for several months despite this winter’s snowfall.
NOAA released their Spring Flood Risk today. According to their map, most of Illinois has a minor risk of flooding this spring. An area at risk of moderate flooding is seen in southern Illinois. Sorry for the non-transparent overlay on the map – their map, not mine.
The good news of sorts is that much of the upper Midwest, including northern Illinois has been dry for the last 3-4 months. In the last few weeks, what snow cover we had in the central US is gone, as this map shows.
The NOAA Climate Prediction Center released their latest outlooks for April and beyond today. Areas without shading are labeled EC for equal chances of above, below, and near-average conditions.
Here are the outlooks for April for temperature (left) and precipitation (right). Nothing much to report temperatures but the northern third of Illinois has an increased chance of below-average precipitation. This area has been dry all winter. Click to enlarge.
As the snow turns to mud this week, this is a good time to advertise links for the soil temperatures in Illinois. The Water Survey operates a 19-station network of sites around the state collecting hourly soil temperatures at 4 and 8 inches under grass as well as an estimate under bare ground.
All this information can be found at the Illinois Climate Network Soil Data site. Below is just a screenshot of that page to show where you would find that information on the real web page.
Here is a snapshot of 4-inch soil temperatures as of 10 am, March 13, 2015. Soil temperatures are still near the freezing mark in the northern half of the state, but warm into the 40s and low 50s in the southern half of the state.
While tornadoes can happen any time of the year, the tornado season really starts to ramp up in March in Illinois (see plot below) and remains active through the spring and on into summer. April, May, and June are the three standout months historically. So far 2015 has been very quiet with no severe weather reported in Illinois so far, according to NOAA.
You can see more plots like this on our tornado plots page.
Historical Tornado Tracks