Tornadoes · United States · Illinois · 1986

F1 tornado, Johnson County, Illinois, May 15, 1986

This F1 tornado ran 6.0 miles across Johnson County on May 15, 1986, touching down at 6:35 PM CDT and reaching 10 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
Date
May 15, 1986
Touchdown
6:35 PM CDT (23:35 UTC)
Path length
6.0 miles (9.7 km)
Path width
10 yards (9 m)
Deaths
0
Injuries
0
Property damage
$5,000 to $50,000
County
Johnson County
Touchdown point
37.420, -88.900
Lift-off point
37.470, -88.750
Record number
291

The warnings

17 minutes of warning. NWS PAH issued a tornado warning for this county at 23:18 UTC, 17 minutes before the tornado touched down, in force until 00:00 UTC.

Issued (UTC)ExpiredProductOffice
22:36 UTC23:15 UTCSevere Thunderstorm WarningPAH
23:18 UTC00:00 UTCTornado WarningPAH

Every warning and watch covering the touchdown point that day, from the Iowa Environmental Mesonet's archive of National Weather Service products. Lead time is measured from the issue of the warning in force to the touchdown time in the database, both of which were recorded to the minute by different people.

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.

Salem-Leckrone, IL (KSLO), 12:00Z

11.6 hours before the tornado, 134 km from the path. May 15, 1986.

Skew-T log-pSkew-T log-p diagram, Salem-Leckrone, IL at 12:00Z on 1986-05-15Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 10 joules per kilogram, CIN -77, lifted condensation level 593 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, Salem-Leckrone, IL at 12:00Z on 1986-05-15The 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 303 square meters per square second, 0 to 6 km bulk shear 36 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
10 J/kg
Mixed-layer CIN
-77 J/kg
Surface CAPE
5 J/kg
Mixed-layer LCL
593 m above ground
0-6 km bulk shear
36 kt
0-1 km bulk shear
27 kt
0-1 km storm-relative helicity
303 m²/s²
0-3 km storm-relative helicity
342 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
5.2 K/km

Open this sounding in Storm Lab

Salem-Leckrone, IL (KSLO), 00:00Z

0.4 hours after it, 134 km from the path. May 16, 1986.

Skew-T log-pSkew-T log-p diagram, Salem-Leckrone, IL at 00:00Z on 1986-05-16Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 1239 joules per kilogram, CIN -5, lifted condensation level 892 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, Salem-Leckrone, IL at 00:00Z on 1986-05-16The 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 127 square meters per square second, 0 to 6 km bulk shear 39 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
1239 J/kg
Mixed-layer CIN
-5 J/kg
Surface CAPE
1829 J/kg
Mixed-layer LCL
892 m above ground
0-6 km bulk shear
39 kt
0-1 km bulk shear
17 kt
0-1 km storm-relative helicity
127 m²/s²
0-3 km storm-relative helicity
192 m²/s²
Significant tornado parameter
0.9
Supercell composite
5.8
0-3 km lapse rate
6.9 K/km

Open this sounding in Storm Lab

The surface observations

Marion Regional (MWA), 38 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
00:00 UTC73.4180° 9 kt1011.5

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

This ground now

The live radar over the trackEvery 1986 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

The other tornadoes of May 15, 1986

23 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
May 153:30 PM CDTF0Boone, IL0.210$500 to $5,000
May 153:30 PM CDTF1Lee, IL1.0101$5,000 to $50,000
May 153:50 PM CDTF0Posey, IN0.210
May 153:55 PM CDTF0Vanderburgh, IN0.210
May 154:45 PM CDTF2Vanderburgh, IN0.210$50,000 to $500,000
May 155:54 PM EDTF3Branch, MI1.2200$500,000 to $5 million
May 155:00 PM CDTF1Stoddard, MO0.5100$500,000 to $5 million
May 156:27 PM EDTF1Crawford, OH9.0120$50,000 to $500,000
May 155:30 PM ESTF1Dubois, IN0.210$500 to $5,000
May 155:51 PM CDTF0Stoddard, MO0.273
May 156:00 PM CDTF0Stoddard, MO0.273
May 157:05 PM EDTF0Huron, OH1.073$5,000 to $50,000
May 155:15 PM MDTF1Crowley, CO0.530
May 156:15 PM CDTF1Stoddard, MO15.0200$5,000 to $50,000
May 156:30 PM CDTF2Scott, MO9.050019$5 million to $50 million
May 156:55 PM ESTF2Daviess, IN0.210$5,000 to $50,000
May 157:30 PM CDTF2Scott, MO4.0400115$500,000 to $5 million
May 157:45 PM CDTF1Coles, IL8.010$50,000 to $500,000
May 158:00 PM CDTF0Pope, IL0.210$500 to $5,000
May 158:04 PM CDTF1Edgar, IL3.5100$5,000 to $50,000
May 158:30 PM CDTF2Edgar, IL5.010
May 158:45 PM ESTF0Fountain, IN5.0140$5,000 to $50,000
May 1510:57 PM EDTF1Trumbull, OH0.830$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.