Tornadoes · United States · Iowa · 1964

F2 tornado, Clarke County, Iowa, June 22, 1964

This F2 tornado ran 12.8 miles across Clarke County on June 22, 1964, touching down at 8:00 PM GMT-5 and reaching 400 yards wide. It killed nobody, 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
June 22, 1964
Touchdown
8:00 PM GMT-5 (01:00 UTC)
Path length
12.8 miles (20.6 km)
Path width
400 yards (366 m)
Deaths
0
Injuries
0
Property damage
$50,000 to $500,000
County
Clarke County
Touchdown point
40.930, -93.980
Lift-off point
41.050, -93.780
Record number
468

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.

Omaha, NE (KOAX), 00:00Z

1.0 hours before the tornado, 212 km from the path. June 23, 1964.

Skew-T log-pSkew-T log-p diagram, Omaha, NE at 00:00Z on 1964-06-23Temperature 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 -25027, lifted condensation level 3633 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, Omaha, NE at 00:00Z on 1964-06-23The 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 161 square meters per square second, 0 to 6 km bulk shear 68 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
-25027 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
3633 m above ground
0-6 km bulk shear
68 kt
0-1 km bulk shear
30 kt
0-1 km storm-relative helicity
161 m²/s²
0-3 km storm-relative helicity
266 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
6.2 K/km

Open this sounding in Storm Lab

Omaha, NE (KOAX), 12:00Z

11.0 hours after it, 212 km from the path. June 23, 1964.

Skew-T log-pSkew-T log-p diagram, Omaha, NE at 12:00Z on 1964-06-23Temperature 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 -87228, lifted condensation level 3653 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, Omaha, NE at 12:00Z on 1964-06-23The 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 116 square meters per square second, 0 to 6 km bulk shear 42 knots.1939587897117Sfc1 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
-87228 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
3653 m above ground
0-6 km bulk shear
42 kt
0-1 km bulk shear
19 kt
0-1 km storm-relative helicity
116 m²/s²
0-3 km storm-relative helicity
235 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
4.1 K/km

Open this sounding in Storm Lab

This ground now

The live radar over the trackEvery 1964 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

The other tornadoes of June 22, 1964

17 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
June 222:00 AM GMT-5F2Lincoln, SD16.110
June 222:45 AM GMT-5F2Minnehaha, SD10.010$5,000 to $50,000
June 223:40 AM GMT-5F1Charles Mix, SD0.110
June 223:30 PM GMT-5F0Marshall, KS0.110
June 223:30 PM GMT-5F1Carroll, IA0.5100$5,000 to $50,000
June 224:10 PM GMT-5F0Nemaha, KS0.110
June 226:00 PM GMT-5F1Buchanan, MO1.050$5,000 to $50,000
June 226:30 PM GMT-5F0Hemphill, TX1.017
June 228:20 PM GMT-4F1York, SC1.553$5,000 to $50,000
June 227:30 PM GMT-5F2Dallas, IA9.7200$50,000 to $500,000
June 227:40 PM GMT-5F2Decatur, IA1.0200$50,000 to $500,000
June 228:00 PM GMT-5F3Fremont, IA8.0400$50,000 to $500,000
June 228:00 PM GMT-5F4Fremont, IA11.9400$50,000 to $500,000
June 228:15 PM GMT-5F1Tama, IA2.0300$50,000 to $500,000
June 228:30 PM GMT-5F2Marion, IA6.4200$5,000 to $50,000
June 229:00 PM GMT-5F1Bourbon, KS0.110$5,000 to $50,000
June 229:45 PM GMT-5F1Monroe, IA5.4200$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.