Tornadoes · United States · Oklahoma · 1973
F1 tornado, Craig and Ottawa counties, Oklahoma, April 21, 1973
This F1 tornado ran 5.1 miles across Craig and Ottawa counties on April 21, 1973, touching down at 8:40 PM CST and reaching 40 yards wide. It killed nobody.
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.
F040 to 72 mph
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
F173 to 112 mphthis tornado
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
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.
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.
F4207 to 260 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
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.
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
- F1
- Date
- April 21, 1973
- Touchdown
- 8:40 PM CST (02:40 UTC)
- Path length
- 5.1 miles (8.2 km)
- Path width
- 40 yards (37 m)
- Deaths
- 0
- Injuries
- 0
- Counties
- Craig and Ottawa counties
- Touchdown point
- 36.630, -95.020
- Lift-off point
- 36.680, -94.950
- Record number
- 218
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), 00:00Z
2.7 hours before the tornado, 109 km from the path. April 22, 1973.
- Mixed-layer CAPE
- 1044 J/kg
- Mixed-layer CIN
- -6 J/kg
- Surface CAPE
- 1343 J/kg
- Mixed-layer LCL
- 643 m above ground
- 0-6 km bulk shear
- 49 kt
- 0-1 km bulk shear
- 18 kt
- 0-1 km storm-relative helicity
- 122 m²/s²
- 0-3 km storm-relative helicity
- 168 m²/s²
- Significant tornado parameter
- 0.9
- Supercell composite
- 4.9
- 0-3 km lapse rate
- 6.7 K/km
Springfield, MO (KUMN), 12:00Z
9.3 hours after it, 109 km from the path. April 22, 1973.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- -10257 J/kg
- Surface CAPE
- 2 J/kg
- Mixed-layer LCL
- 1390 m above ground
- 0-6 km bulk shear
- 67 kt
- 0-1 km bulk shear
- 8 kt
- 0-1 km storm-relative helicity
- -108 m²/s²
- 0-3 km storm-relative helicity
- -58 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
- 0-3 km lapse rate
- 4.8 K/km
The surface observations
Joplin (JLN), 70 km from the path, in the two hours either side.
| Time (UTC) | Temp (°F) | Dew point (°F) | Wind | Gust (kt) | Pressure (mb) | Weather |
|---|---|---|---|---|---|---|
| 01:00 UTC | 70.88 | 63 | 190° 13 kt | 1013.2 | ||
| 02:00 UTC | 70.88 | 61.88 | 190° 13 kt | 1013.9 | -SHRA | |
| 03:00 UTC | 70.88 | 61.88 | 200° 12 kt | 1014.6 | TSRA | |
| 04:00 UTC | 63 | 56 | 180° 15 kt | 1014.2 | TSRA |
From the Iowa Environmental Mesonet's archive of airport observations.
This ground now
The live radar over the trackEvery 1973 tornado in OklahomaEvery tornado in Oklahoma since 1950Warnings in force in Oklahoma nowThe forecast where you are
The other tornadoes of April 21, 1973
11 more were confirmed in the United States that day.
| Date | Time | Rating | Where | Path (mi) | Width (yd) | Deaths | Injuries | Damage |
|---|---|---|---|---|---|---|---|---|
| April 21 | 2:00 PM CST | F4 | Mercer, MO | 14.6 | 440 | 1 | $50,000 to $500,000 | |
| April 21 | 3:40 PM CST | F2 | Iowa, IA | 13.2 | 10 | 6 | ||
| April 21 | 5:43 PM CST | F2 | Mercer, IL | 30.2 | 10 | 2 | $500,000 to $5 million | |
| April 21 | 6:10 PM CST | F1 | Lee, IA | 4.1 | 250 | $5,000 to $50,000 | ||
| April 21 | 8:00 PM CST | F1 | Craig, OK | 0.1 | 120 | $5,000 to $50,000 | ||
| April 21 | 9:00 PM CST | F2 | Cook, IL | 0.2 | 10 | $5,000 to $50,000 | ||
| April 21 | 9:15 PM CST | F1 | Cook, IL | 0.2 | 10 | $5,000 to $50,000 | ||
| April 21 | 9:20 PM CST | F1 | Henry, IA | 1.0 | 150 | $5,000 to $50,000 | ||
| April 21 | 9:35 PM CST | F2 | Jasper, MO | 5.0 | 100 | 2 | $5,000 to $50,000 | |
| April 21 | 10:15 PM CST | F1 | Bureau, IL | 11.6 | 10 | $50,000 to $500,000 | ||
| April 21 | 10:20 PM CST | F1 | Bureau, IL | 8.6 | 60 | $50,000 to $500,000 |
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.