Tornadoes · United States · Iowa · 1975

F1 tornado, Dickinson County, Iowa, May 22, 1975

This F1 tornado ran 0.1 miles across Dickinson County on May 22, 1975, touching down at 8:30 PM CDT and reaching 10 yards wide. It killed nobody, and did $50 to $500 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 mphthis tornado

    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 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
F1
Date
May 22, 1975
Touchdown
8:30 PM CDT (01:30 UTC)
Path length
0.1 miles (0.2 km)
Path width
10 yards (9 m)
Deaths
0
Injuries
0
Property damage
$50 to $500
County
Dickinson County
Touchdown point
43.300, -95.250
Record number
430

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.

Minneapolis, MN (KSTC), 00:00Z

1.5 hours before the tornado, 217 km from the path. May 23, 1975.

Skew-T log-pSkew-T log-p diagram, Minneapolis, MN at 00:00Z on 1975-05-23Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 282 joules per kilogram, CIN -176, lifted condensation level 1894 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, Minneapolis, MN at 00:00Z on 1975-05-23The 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 78 square meters per square second, 0 to 6 km bulk shear 26 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
282 J/kg
Mixed-layer CIN
-176 J/kg
Surface CAPE
1125 J/kg
Mixed-layer LCL
1894 m above ground
0-6 km bulk shear
26 kt
0-1 km bulk shear
14 kt
0-1 km storm-relative helicity
78 m²/s²
0-3 km storm-relative helicity
95 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.8
0-3 km lapse rate
7.6 K/km

Open this sounding in Storm Lab

Minneapolis, MN (KSTC), 12:00Z

10.5 hours after it, 217 km from the path. May 23, 1975.

Skew-T log-pSkew-T log-p diagram, Minneapolis, MN at 12:00Z on 1975-05-23Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 248 joules per kilogram, CIN -172, lifted condensation level 930 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, Minneapolis, MN at 12:00Z on 1975-05-23The 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 230 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
248 J/kg
Mixed-layer CIN
-172 J/kg
Surface CAPE
2 J/kg
Mixed-layer LCL
930 m above ground
0-6 km bulk shear
38 kt
0-1 km bulk shear
23 kt
0-1 km storm-relative helicity
230 m²/s²
0-3 km storm-relative helicity
233 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.6
0-3 km lapse rate
3.7 K/km

Open this sounding in Storm Lab

The surface observations

Spencer (SPW), 15 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
00:00 UTC6855.450° 8 kt1011.2
02:00 UTC6660300° 7 kt1012.2
03:00 UTC66.260.850° 8 kt1011.2

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

This ground now

The live radar over the trackEvery 1975 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

The other tornadoes of May 22, 1975

16 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
May 2211:15 AM MDTF2Bent, CO2.0220$500 to $5,000
May 2211:15 AM MDTF1Bent, CO2.3150
May 222:15 PM CDTF0Sherman, NE0.217$50,000 to $500,000
May 222:30 PM CDTF1Jewell, KS4.933$5,000 to $50,000
May 223:05 PM CDTF0Boone, NE0.217
May 223:13 PM CDTF0Wheeler, NE0.217$500 to $5,000
May 223:40 PM CDTF0Madison, NE0.217
May 224:55 PM CDTF0Cass, NE0.217
May 225:45 PM CDTF2Woodbury, IA0.110$5,000 to $50,000
May 226:10 PM CDTF0Scurry, TX0.520
May 226:40 PM CDTF0Wichita, TX0.110
May 227:30 PM CDTF1Dickinson, IA0.110$50 to $500
May 228:30 PM CDTF1Dickinson, IA0.110$50 to $500
May 228:45 PM CDTF0Hutchinson, TX2.040
May 229:40 PM CDTF0Fisher, TX0.520
May 2210:00 PM CDTF0Howard, TX1.030

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.