Tornadoes · United States · Illinois · 1977

F4 tornado, Logan and DeWitt counties, Illinois, May 5, 1977

This F4 tornado ran 7.3 miles across Logan and DeWitt counties on May 5, 1977, touching down at 8:20 PM CDT and reaching 1,000 yards wide. It killed nobody and injured 2, and did $500,000 to $5 million of property damage.

The rating scale

Tracks are drawn in the color of the rating. The Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.

  1. F040 to 72 mph

    Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

  2. F173 to 112 mph

    Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

  3. F2113 to 157 mph

    Considerable damage. Roofs torn off well-built houses, frame homes shifted on their foundations, mobile homes destroyed, large trees snapped or uprooted, cars lifted off the ground.

  4. F3158 to 206 mph

    Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

  5. F4207 to 260 mphthis tornado

    Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

  6. F5261 to 318 mph

    Incredible damage. Strong frame houses swept off their foundations, car-sized missiles thrown more than 100 meters, steel-reinforced concrete badly damaged, high-rise buildings deformed.

  7. Unrated

    The survey recorded a tornado but could not put a number on it, most often because it crossed open country and damaged nothing a rating can be read from.

The record

Rating
F4
Date
May 5, 1977
Touchdown
8:20 PM CDT (01:20 UTC)
Path length
7.3 miles (11.7 km)
Path width
1,000 yards (914 m)
Deaths
0
Injuries
2
Property damage
$500,000 to $5 million
Counties
Logan and DeWitt counties
Touchdown point
40.250, -89.250
Lift-off point
40.330, -89.120
Record number
234

The air that afternoon

The radiosonde launches on either side of the tornado, from the nearest station that was launching then, drawn and analyzed the way Storm Lab does: the same diagram, the same parcel and shear definitions SPC's mesoanalysis uses.

Peoria Regional, IL (KPIA), 00:00Z

1.3 hours before the tornado, 55 km from the path. May 6, 1977.

Skew-T log-pSkew-T log-p diagram, Peoria Regional, IL at 00:00Z on 1977-05-06Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 2696 joules per kilogram, CIN -4, lifted condensation level 999 meters above ground. Wind barbs in knots down the right edge.LCLEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Peoria Regional, IL at 00:00Z on 1977-05-06The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity 42 square meters per square second, 0 to 6 km bulk shear 31 knots.193958Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
2696 J/kg
Mixed-layer CIN
-4 J/kg
Surface CAPE
2972 J/kg
Mixed-layer LCL
999 m above ground
0-6 km bulk shear
31 kt
0-1 km bulk shear
11 kt
0-1 km storm-relative helicity
42 m²/s²
0-3 km storm-relative helicity
83 m²/s²
Significant tornado parameter
0.8
Supercell composite
4.1
0-3 km lapse rate
6.9 K/km

Open this sounding in Storm Lab

Peoria Regional, IL (KPIA), 12:00Z

10.7 hours after it, 55 km from the path. May 6, 1977.

Skew-T log-pSkew-T log-p diagram, Peoria Regional, IL at 12:00Z on 1977-05-06Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 89 joules per kilogram, CIN -23, lifted condensation level 699 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Peoria Regional, IL at 12:00Z on 1977-05-06The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity 14 square meters per square second, 0 to 6 km bulk shear 38 knots.193958Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
89 J/kg
Mixed-layer CIN
-23 J/kg
Surface CAPE
15 J/kg
Mixed-layer LCL
699 m above ground
0-6 km bulk shear
38 kt
0-1 km bulk shear
3 kt
0-1 km storm-relative helicity
14 m²/s²
0-3 km storm-relative helicity
-56 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
5.3 K/km

Open this sounding in Storm Lab

The surface observations

Bloomington/Norm (BMI), 31 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
00:00 UTC230° 8 kt1006.4

From the Iowa Environmental Mesonet's archive of airport observations.

This ground now

The live radar over the trackEvery 1977 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

The other tornadoes of May 5, 1977

13 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
May 52:50 PM CDTF1Hardeman, TX0.110$500 to $5,000
May 52:50 PM CDTF1Hardeman, TX0.110
May 53:55 PM CDTF0Martin, TX0.110
May 56:40 PM EDTF1Person, NC0.530$500 to $5,000
May 55:45 PM CDTF1Des Moines, IA14.1100
May 55:45 PM CDTF0Dickens, TX0.110
May 56:00 PM CDTF0Stonewall, TX0.110
May 57:30 PM EDTF1Edgecombe, NC1.523$5,000 to $50,000
May 56:40 PM CDTF1Shawnee, KS1.930$500 to $5,000
May 57:15 PM CDTF1Wichita, TX7.810
May 57:30 PM CDTF1Wichita, TX6.210
May 58:30 PM CDTF1Stephens, OK0.550$5,000 to $50,000
May 510:00 PM CDTF0Starke, IN0.210$50 to $500

What this means

Ratings are the survey's, read off the damage rather than measured; the rating scale is above. Tornado counts rise through the record as reporting improved, so a year in the 1950s is not comparable with one today except for the strongest tornadoes, which were always noticed.

Sources

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.