Tornadoes · United States · Illinois · 1978

F2 tornado, Macoupin and Montgomery counties, Illinois, May 12, 1978

This F2 tornado ran 34.1 miles across Macoupin and Montgomery counties on May 12, 1978, touching down at 4:50 PM CDT and reaching 700 yards wide. It killed nobody and injured 1, and did $50,000 to $500,000 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 mphthis tornado

    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 mph

    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
F2
Date
May 12, 1978
Touchdown
4:50 PM CDT (21:50 UTC)
Path length
34.1 miles (54.9 km)
Path width
700 yards (640 m)
Deaths
0
Injuries
1
Property damage
$50,000 to $500,000
Counties
Macoupin and Montgomery counties
Touchdown point
39.120, -90.050
Lift-off point
39.480, -89.620
Record number
244

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.

Salem-Leckrone, IL (KSLO), 12:00Z

9.8 hours before the tornado, 108 km from the path. May 12, 1978.

Skew-T log-pSkew-T log-p diagram, Salem-Leckrone, IL at 12:00Z on 1978-05-12Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 0 joules per kilogram, CIN -7395, lifted condensation level 958 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 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, Salem-Leckrone, IL at 12:00Z on 1978-05-12The 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 139 square meters per square second, 0 to 6 km bulk shear 40 knots.19395878Sfc1 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
0 J/kg
Mixed-layer CIN
-7395 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
958 m above ground
0-6 km bulk shear
40 kt
0-1 km bulk shear
16 kt
0-1 km storm-relative helicity
139 m²/s²
0-3 km storm-relative helicity
165 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
4.6 K/km

Open this sounding in Storm Lab

Salem-Leckrone, IL (KSLO), 00:00Z

2.2 hours after it, 108 km from the path. May 13, 1978.

Skew-T log-pSkew-T log-p diagram, Salem-Leckrone, IL at 00:00Z on 1978-05-13Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 949 joules per kilogram, CIN -12, lifted condensation level 570 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, Salem-Leckrone, IL at 00:00Z on 1978-05-13The 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 188 square meters per square second, 0 to 6 km bulk shear 38 knots.19395878Sfc1 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
949 J/kg
Mixed-layer CIN
-12 J/kg
Surface CAPE
2182 J/kg
Mixed-layer LCL
570 m above ground
0-6 km bulk shear
38 kt
0-1 km bulk shear
28 kt
0-1 km storm-relative helicity
188 m²/s²
0-3 km storm-relative helicity
235 m²/s²
Significant tornado parameter
0.9
Supercell composite
9.7
0-3 km lapse rate
5.9 K/km

Open this sounding in Storm Lab

This ground now

The live radar over the trackEvery 1978 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

The other tornadoes of May 12, 1978

25 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
May 121:35 AM CDTF1Caddo Parish, LA4.053$50,000 to $500,000
May 122:00 PM CDTF1Polk, MO3.6100$5,000 to $50,000
May 122:14 PM CDTF1Benton, AR3.050$5,000 to $50,000
May 123:15 PM CDTF2Pulaski, MO19.54004$500,000 to $5 million
May 124:00 PM CDTF1Dent, MO0.110$5,000 to $50,000
May 124:05 PM CDTF1Saint Louis, MO0.550$50,000 to $500,000
May 124:30 PM CDTF1Kaufman, TX0.110
May 125:10 PM CDTF2Stone, AR12.1200$50,000 to $500,000
May 126:00 PM CDTF1Jefferson, MO4.5200$50,000 to $500,000
May 126:20 PM CDTF1Daviess, MO1.02001$50,000 to $500,000
May 126:45 PM CDTF1Hempstead, AR2.0772$5,000 to $50,000
May 127:00 PM CDTF2Macon, IL7.67003$50,000 to $500,000
May 127:00 PM CDTF0Grant, AR0.327
May 127:58 PM CDTF0Arkansas, AR0.350$500 to $5,000
May 128:00 PM CDTF2Trigg, KY15.8800$500,000 to $5 million
May 128:25 PM CDTF3Trigg, KY9.580017$500,000 to $5 million
May 129:05 PM CDTF0Houston, TX0.110
May 129:05 PM CDTF0Houston, TX0.110
May 129:05 PM CDTF0Houston, TX0.110
May 129:20 PM ESTF1Pike, IN1.540$50,000 to $500,000
May 129:35 PM CDTF1Pontotoc, MS14.520018$50,000 to $500,000
May 1210:45 PM EDTF1Letcher, KY14.4400$50,000 to $500,000
May 1210:25 PM CDTF2Coahoma, MS33.4100$5 million to $50 million
May 1212:15 AM CDTF1Morgan, AL3.610011$50,000 to $500,000
May 1212:35 AM CDTF1Marshall, AL8.0200

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.