Tornadoes · United States · Iowa · 1978

F1 tornado, Lee County, Iowa, July 1, 1978

This F1 tornado ran 5.0 miles across Lee County on July 1, 1978, touching down at 3:30 PM CDT and reaching 30 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 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, estimated from the damage record rather than surveyed
Date
July 1, 1978
Touchdown
3:30 PM CDT (20:30 UTC)
Path length
5.0 miles (8.0 km)
Path width
30 yards (27 m)
Deaths
0
Injuries
0
Property damage
$5,000 to $50,000
County
Lee County
Touchdown point
40.670, -91.230
Record number
516

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), 12:00Z

8.5 hours before the tornado, 137 km from the path. July 1, 1978.

Skew-T log-pSkew-T log-p diagram, Peoria Regional, IL at 12:00Z on 1978-07-01Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 1915 joules per kilogram, CIN -86, lifted condensation level 1139 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 12:00Z on 1978-07-01The 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 117 square meters per square second, 0 to 6 km bulk shear 19 knots.1939Sfc1 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
1915 J/kg
Mixed-layer CIN
-86 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
1139 m above ground
0-6 km bulk shear
19 kt
0-1 km bulk shear
21 kt
0-1 km storm-relative helicity
117 m²/s²
0-3 km storm-relative helicity
138 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
4.8 K/km

Open this sounding in Storm Lab

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

3.5 hours after it, 137 km from the path. July 2, 1978.

Skew-T log-pSkew-T log-p diagram, Peoria Regional, IL at 00:00Z on 1978-07-02Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 2151 joules per kilogram, CIN -8, lifted condensation level 1240 meters above ground. Wind barbs in knots down the right edge.LCLEL10008507005003002001001 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 1978-07-02The 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 12 square meters per square second, 0 to 6 km bulk shear 32 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
2151 J/kg
Mixed-layer CIN
-8 J/kg
Surface CAPE
1896 J/kg
Mixed-layer LCL
1240 m above ground
0-6 km bulk shear
32 kt
0-1 km bulk shear
6 kt
0-1 km storm-relative helicity
12 m²/s²
0-3 km storm-relative helicity
41 m²/s²
Significant tornado parameter
0.3
Supercell composite
1.9
0-3 km lapse rate
7.0 K/km

Open this sounding in Storm Lab

The surface observations

Burlington (BRL), 14 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
19:00 UTC9175290° 6 kt1010.8DZ
20:00 UTC9173270° 6 kt1009.8DZ
20:05 UTC300° 7 kt1009.1
21:00 UTC7363180° 15 kt1009.5TSRA
21:25 UTC110° 6 kt1008.8
22:00 UTC7467120° 5 kt1008.8-SHRA

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

This ground now

The live radar over the trackEvery 1978 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

The other tornadoes of July 1, 1978

7 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
July 14:45 PM ESTF1Bartholomew, IN0.5506$5,000 to $50,000
July 15:20 PM CDTF0Sherman, TX0.410
July 14:30 PM PDTF1Franklin, WA2.310
July 18:02 PM CDTF1Vernon, WI0.1100
July 18:02 PM CDTF1Vernon, WI0.1100
July 18:02 PM CDTF1Vernon, WI0.1100
July 19:43 PM EDTF0Orange, FL0.110$50 to $500

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.