February 20, 2014 Tornado Outbreak

Last updated:  3/17/2014
Updated main track map; added maps for Mechanicsburg, Pana/Tower Hill, Shumway; added Google interactive track maps


Tornado photographed near Concord by Teresa Thompson


Summary:

A powerful late winter storm system brought much warmer conditions, as well as severe weather, to parts of the Midwest on Thursday, February 20.  Storm survey results indicate 11 tornadoes occurred over central and southern Illinois, with most of them between the I-72 and I-70 corridors of central Illinois (the main exception was an EF-1 tornado south of Murphysboro, in far southern Illinois).  In addition to the tornadoes, strong winds accompanied the severe storms, which moved through the state during the afternoon hours.  Even behind the storms, the intensifying parent storm system produced wind gusts of 45 to 65 mph which persisted well into the evening.

This map shows the results of the storm surveys in central Illinois.  Ten tornadoes occurred, with the longest one on the ground for about 22 miles, from near Nokomis to northeast of Pana.  

Tornado track map from February 20. Google Map display of the 02/20/14 storm survey

Seven of the tornadoes occurred in the Lincoln NWS coverage area:

Location Intensity and Peak Wind Path Length Fatalities Injuries
Concord/Arenzville (Morgan and Cass Counties) EF-0 (80 mph) 5.6 miles 0 0
Divernon (Sangamon County) EF-0 (80 mph) 0.2 mile 0 0
Mechanicsburg/Illiopolis (Sangamon County)          *Google Map* EF-1 (110 mph) 9.0 miles 0 0
Nokomis, Pana, Tower Hill (Montgomery, Christian and Shelby Counties)    *Google Map* EF-2 (115 mph) 22.2 miles 0 1
Findlay (Shelby County) EF-0 (75 mph) 0.3 mile 0 0
Shumway (Effingham County) EF-1 (95 mph) 1.5 miles 0 0
Chrisman (Edgar County) EF-0 (80 mph) 2.0 miles 0 0

Tornado Tracks KML

Damage Survey Points KML

Damage Survey Photos KML

 

Survey results from the St. Louis NWS office are available for the following tornadoes:

Overview:

A 991mb low pressure over eastern Kansas during the morning of February 20th rapidly deepened to 983mb as it tracked into southwestern Wisconsin by evening.  As the low passed to the northwest of central Illinois, southerly winds pulled much warmer air northward into the area, resulting in high temperatures soaring well into the 50s and 60s. The warm/moist air flowing over the cold/snow-covered ground led to the development of widespread dense fog along and north of a Canton to Bloomington-Normal line during the late morning and afternoon. Visibilities across this part of the state were reduced to near zero at times before southerly winds increased sufficiently to scour out the fog by late afternoon.

As a trailing cold front approached from the west, scattered thunderstorms developed across northern and central Missouri by early afternoon.  The big question of the day was how far north into central Illinois could these strong to potentially severe thunderstorms survive, especially given the lingering snow cover north of the I-72 corridor.  Here is a map showing the measured snow depth as of 7 AM February 21st.  This is a good approximation as to where snow cover existed as the storms came into central Illinois during the afternoon of the 20th.  Note that at least 1 inch of snow remained on the ground along and north of a Quincy, to Bloomington, to Hoopeston line, with as much as 5 to 7 inches from the Peoria area northward.  

Snow depth on the morning of February 20

The storms only had modest instability to work with, but plenty of low-level wind shear in the vicinity of the rapidly strengthening surface low to the west.  As they tracked northeastward, several of the cells began to rotate and tornado warnings were subsequently issued.  The first confirmed tornado across NWS Lincoln's County Warning Area occurred 2.5 miles northwest of Concord in Morgan County shortly before 3 PM.  No damage was reported with this short-lived weak tornado as it tracked across rural areas of Morgan and Cass counties.  Later in the afternoon, two tornadoes touched down in Sangamon County, including an EF-1 tornado 4 miles south of Mechanicsburg that damaged numerous outbuildings and the roofs of several homes and flipped over a trailer.  The strongest tornado of the day touched down about 3 miles south of Pana in Christian County at 4:20 PM then tracked northeastward to just north of Tower Hill in Shelby County.  It created EF-2 damage at times, including major roof damage to a house 3 miles northwest of Tower Hill.  Other tornadoes occurred in Effingham and Edgar counties: however, they were short-lived and did minimal damage.

Once the cold front exited central Illinois during the evening of February 20th, very strong westerly winds developed due to an intense pressure gradient between the deep low over southwestern Wisconsin and a high over the Plains.  Winds gusted to between 45 and 55 mph at times, with Capital Airport in Springfield recording a peak wind gust of 64 mph.

In addition to the winds, the rapidly melting snow, combined with the rainfall from the storms, produced widespread flooding in farm fields and low lying areas, as the frozen ground did not allow the water to soak into the soil.  Some rivers and creeks came out of their banks as well.  Several area roads were impassible due to the high waters.


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