Tornadoes · United States · Missouri · 1973

F3 tornado, Cedar County, Missouri, April 20, 1973

This F3 tornado ran 1.0 miles across Cedar County on April 20, 1973, touching down at 2:30 PM CST and reaching 50 yards wide. It killed nobody, and did $5,000 to $50,000 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 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 mphthis tornado

    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
F3
Date
April 20, 1973
Touchdown
2:30 PM CST (20:30 UTC)
Path length
1.0 miles (1.6 km)
Path width
50 yards (46 m)
Deaths
0
Injuries
0
Property damage
$5,000 to $50,000
County
Cedar County
Touchdown point
37.570, -93.800
Record number
199

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.

Springfield, MO (KUMN), 12:00Z

8.5 hours before the tornado, 75 km from the path. April 20, 1973.

Skew-T log-pSkew-T log-p diagram, Springfield, MO at 12:00Z on 1973-04-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 804 joules per kilogram, CIN -36, lifted condensation level 866 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, Springfield, MO at 12:00Z on 1973-04-20The 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 254 square meters per square second, 0 to 6 km bulk shear 57 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
804 J/kg
Mixed-layer CIN
-36 J/kg
Surface CAPE
975 J/kg
Mixed-layer LCL
866 m above ground
0-6 km bulk shear
57 kt
0-1 km bulk shear
36 kt
0-1 km storm-relative helicity
254 m²/s²
0-3 km storm-relative helicity
318 m²/s²
Significant tornado parameter
1.4
Supercell composite
6.9
0-3 km lapse rate
5.2 K/km

Open this sounding in Storm Lab

Springfield, MO (KUMN), 00:00Z

3.5 hours after it, 75 km from the path. April 21, 1973.

Skew-T log-pSkew-T log-p diagram, Springfield, MO at 00:00Z on 1973-04-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 1655 joules per kilogram, CIN -11, lifted condensation level 814 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, Springfield, MO at 00:00Z on 1973-04-21The 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 289 square meters per square second, 0 to 6 km bulk shear 62 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
1655 J/kg
Mixed-layer CIN
-11 J/kg
Surface CAPE
1943 J/kg
Mixed-layer LCL
814 m above ground
0-6 km bulk shear
62 kt
0-1 km bulk shear
33 kt
0-1 km storm-relative helicity
289 m²/s²
0-3 km storm-relative helicity
358 m²/s²
Significant tornado parameter
3.9
Supercell composite
13.7
0-3 km lapse rate
7.2 K/km

Open this sounding in Storm Lab

The surface observations

Springfield (SGF), 52 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
19:00 UTC7165160° 20 kt321008.1
20:00 UTC7166180° 20 kt311008.5
21:00 UTC7166170° 18 kt261008.8
22:00 UTC7367170° 17 kt241008.5

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

This ground now

The live radar over the trackEvery 1973 tornado in MissouriEvery tornado in Missouri since 1950Warnings in force in Missouri nowThe forecast where you are

The other tornadoes of April 20, 1973

22 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
April 2012:15 AM CSTF3Pontotoc, OK7.910021$500,000 to $5 million
April 207:30 AM CSTF1Logan, AR0.110$500 to $5,000
April 207:50 AM CSTF2Logan, AR1.55002$5,000 to $50,000
April 2010:15 AM CSTF3Boone, AR7.8500119$500,000 to $5 million
April 2012:15 PM CSTF1Washington, IA2.0350$5,000 to $50,000
April 201:00 PM CSTF0St. Clair, MO5.717$500 to $5,000
April 201:08 PM CSTF1St. Clair, MO13.017$50,000 to $500,000
April 201:10 PM CSTF2St. Clair, MO5.717$5,000 to $50,000
April 201:50 PM CSTF1Cooper, MO0.110$500 to $5,000
April 202:30 PM CSTF3Pettis, MO5.050$500 to $5,000
April 201:55 PM MSTF0Navajo, AZ0.110
April 204:00 PM CSTF0Davis, IA2.0150$500 to $5,000
April 204:55 PM CSTF2Carroll, MO5.010$5,000 to $50,000
April 205:05 PM CSTF1St. Clair, MO9.810$5,000 to $50,000
April 205:15 PM CSTF3Benton, MO19.41004$50,000 to $500,000
April 205:30 PM CSTF4Macon, MO3.844013$5,000 to $50,000
April 206:00 PM CSTF2Benton, MO2.010$50,000 to $500,000
April 206:25 PM CSTF3Benton, MO10.1100$50,000 to $500,000
April 206:35 PM CSTF2Cooper, MO2.350$5,000 to $50,000
April 206:35 PM CSTF3Scotland, MO9.5440$50,000 to $500,000
April 207:25 PM CSTF2Pettis, MO2.0508$500,000 to $5 million
April 2010:40 PM CSTF3Dade, MO7.81006$500,000 to $5 million

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.