Tornadoes · United States · Iowa · 1967

F2 tornado, Dubuque County, Iowa, April 30, 1967

This F2 tornado ran 2.0 miles across Dubuque County on April 30, 1967, touching down at 10:00 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
April 30, 1967
Touchdown
10:00 PM GMT-5 (03:00 UTC)
Path length
2.0 miles (3.2 km)
Path width
400 yards (366 m)
Deaths
0
Injuries
0
Property damage
$50,000 to $500,000
County
Dubuque County
Touchdown point
42.400, -90.900
Record number
238

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.

Peoria Regional, IL (KPIA), 00:00Z

3.0 hours before the tornado, 221 km from the path. May 1, 1967.

Skew-T log-pSkew-T log-p diagram, Peoria Regional, IL at 00:00Z on 1967-05-01Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 844 joules per kilogram, CIN -124, lifted condensation level 892 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, Peoria Regional, IL at 00:00Z on 1967-05-01The 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 115 square meters per square second, 0 to 6 km bulk shear 34 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
844 J/kg
Mixed-layer CIN
-124 J/kg
Surface CAPE
1212 J/kg
Mixed-layer LCL
892 m above ground
0-6 km bulk shear
34 kt
0-1 km bulk shear
17 kt
0-1 km storm-relative helicity
115 m²/s²
0-3 km storm-relative helicity
147 m²/s²
Significant tornado parameter
0.3
Supercell composite
2.1
0-3 km lapse rate
5.3 K/km

Open this sounding in Storm Lab

Peoria Regional, IL (KPIA), 12:00Z

9.0 hours after it, 221 km from the path. May 1, 1967.

Skew-T log-pSkew-T log-p diagram, Peoria Regional, IL at 12:00Z on 1967-05-01Temperature 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 -13399, lifted condensation level 2324 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, Peoria Regional, IL at 12:00Z on 1967-05-01The 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 179 square meters per square second, 0 to 6 km bulk shear 66 knots.1939587897Sfc1 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
-13399 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
2324 m above ground
0-6 km bulk shear
66 kt
0-1 km bulk shear
28 kt
0-1 km storm-relative helicity
179 m²/s²
0-3 km storm-relative helicity
224 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

The surface observations

Dubuque (DBQ), 16 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
01:00 UTC7062170° 25 kt
02:00 UTC6862170° 23 kt31995.9
03:00 UTC6762180° 24 kt
04:00 UTC5951240° 10 kt

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

This ground now

The live radar over the trackEvery 1967 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

The other tornadoes of April 30, 1967

20 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
April 304:15 PM GMT-5F1Kingsbury, SD0.110
April 304:50 PM GMT-5F2Webster, IA6.8200
April 305:00 PM GMT-5F2Emmet, IA8.2300$500,000 to $5 million
April 305:10 PM GMT-5F2Palo Alto, IA14.0300$50,000 to $500,000
April 305:30 PM GMT-5F2Hancock, IA4.3300$500,000 to $5 million
April 305:33 PM GMT-5F2Emmet, IA1.0200$50,000 to $500,000
April 306:05 PM GMT-5F3Cerro Gordo, IA7.7250$50,000 to $500,000
April 306:20 PM GMT-5F2Lee, IA2.3400$50,000 to $500,000
April 306:28 PM GMT-5F4Worth, IA13.3400$50,000 to $500,000
April 306:30 PM GMT-5F3Worth, IA17.2800$500,000 to $5 million
April 307:00 PM GMT-5F2Waseca, MN9.267$5 million to $50 million
April 307:05 PM GMT-5F1Steele, MN0.210$5 million to $50 million
April 307:05 PM GMT-5F3Freeborn, MN18.4100223$5 million to $50 million
April 307:20 PM GMT-5F4Worth, IA to MN7.65001$500,000 to $5 million
April 307:23 PM GMT-5F4Freeborn, MN38.7100535$5 million to $50 million
April 307:52 PM GMT-5F4Freeborn, MN20.1267622$5 million to $50 million
April 308:00 PM GMT-5F1Buchanan, IA0.150
April 308:00 PM GMT-5F1Poweshiek, IA0.110$5,000 to $50,000
April 308:15 PM GMT-5F2Mower, MN3.810$5 million to $50 million
April 309:10 PM GMT-5F2Olmsted, MN6.810$5 million to $50 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.