Tornadoes · United States · Illinois · 1974

F1 tornado, Ogle County, Illinois, April 21, 1974

This F1 tornado ran 0.1 miles across Ogle County on April 21, 1974, touching down at 4:15 PM CDT and reaching 10 yards wide. It killed nobody and injured 2, 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 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
April 21, 1974
Touchdown
4:15 PM CDT (21:15 UTC)
Path length
0.1 miles (0.2 km)
Path width
10 yards (9 m)
Deaths
0
Injuries
2
Property damage
$50,000 to $500,000
County
Ogle County
Touchdown point
42.050, -89.270
Record number
324

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

9.3 hours before the tornado, 156 km from the path. April 21, 1974.

Skew-T log-pSkew-T log-p diagram, Peoria Regional, IL at 12:00Z on 1974-04-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 53 joules per kilogram, CIN -239, lifted condensation level 1023 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 1974-04-21The 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 392 square meters per square second, 0 to 6 km bulk shear 50 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
53 J/kg
Mixed-layer CIN
-239 J/kg
Surface CAPE
24 J/kg
Mixed-layer LCL
1023 m above ground
0-6 km bulk shear
50 kt
0-1 km bulk shear
42 kt
0-1 km storm-relative helicity
392 m²/s²
0-3 km storm-relative helicity
389 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
5.4 K/km

Open this sounding in Storm Lab

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

2.7 hours after it, 156 km from the path. April 22, 1974.

Skew-T log-pSkew-T log-p diagram, Peoria Regional, IL at 00:00Z on 1974-04-22Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 143 joules per kilogram, CIN -110, lifted condensation level 1275 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 1974-04-22The 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 146 square meters per square second, 0 to 6 km bulk shear 67 knots.1939587897117136Sfc1 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
143 J/kg
Mixed-layer CIN
-110 J/kg
Surface CAPE
6 J/kg
Mixed-layer LCL
1275 m above ground
0-6 km bulk shear
67 kt
0-1 km bulk shear
23 kt
0-1 km storm-relative helicity
146 m²/s²
0-3 km storm-relative helicity
162 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.1
0-3 km lapse rate
6.0 K/km

Open this sounding in Storm Lab

The surface observations

Rockford (RFD), 22 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
19:36 UTC180° 17 kt341006.4
20:00 UTC6559180° 22 kt301006.4-TSRA
20:18 UTC180° 20 kt361005.8
21:00 UTC7060190° 25 kt351004.7
21:24 UTC190° 24 kt331004.7
22:00 UTC6858200° 18 kt301004.7-SHRA
22:02 UTC190° 20 kt261004.7
22:32 UTC220° 13 kt1006.1
23:00 UTC6055330° 6 kt1005.4-TSRA

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

This ground now

The live radar over the trackEvery 1974 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

The other tornadoes of April 21, 1974

13 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
April 212:40 PM CDTF2Henry, IL2.050$500 to $5,000
April 213:00 PM CDTF1Wise, TX0.1101$500 to $5,000
April 213:40 PM CDTF4Fond du Lac, WI26.020035$500,000 to $5 million
April 214:00 PM CDTF3Dodge, WI22.2200$500,000 to $5 million
April 214:20 PM CDTF1Dickinson, MI0.110$50 to $500
April 214:25 PM CDTF2Marinette, WI2.7200$5,000 to $50,000
April 214:30 PM CDTF3Dodge, WI58.6200218$500,000 to $5 million
April 214:48 PM CDTF1Lonoke, AR4.7100$5,000 to $50,000
April 214:55 PM CDTF1Ogle, IL0.110$50,000 to $500,000
April 215:45 PM CDTF2Lamar, TX0.310$5,000 to $50,000
April 216:05 PM CDTF1Red River, TX1.010
April 216:15 PM CDTF2Lamar, TX1.0106$5,000 to $50,000
April 216:50 PM CDTF2Kaufman, TX1.0200

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.