Tornadoes · United States · Illinois · 1998

F1 tornado, Pearl City, Illinois, August 24, 1998

This F1 tornado ran 0.5 miles across Stephenson County on August 24, 1998, touching down at 12:30 PM CDT and reaching 50 yards wide. It killed nobody, and did $80,000 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
August 24, 1998
Touchdown
12:30 PM CDT (17:30 UTC)
Path length
0.5 miles (0.8 km)
Path width
50 yards (46 m)
Deaths
0
Injuries
0
Property damage
$80,000
County
Stephenson County
Touchdown point
42.270, -89.830
Lift-off point
42.270, -89.830
Record number
613

What the Weather Service recorded

Severe thunderstorms developed over North Central Iowa and moved eastward into Illinois blowing down trees, limbs, and powerlines. Numerous homes and farm buildings were damaged by the winds, several vehicles were smashed by falling trees and branches, and thousands of acres of corn and soybeans were damaged or destroyed. In Stephenson County a tornado cut a path through the Pearl City area severely damaging a home and destroying a garage. At the Stephenson County Fair three-fourths of the tents were knocked down. A woman and a kid goat were injured when the tents collapsed. Telephone and electric service was out throughout much of the Elizabeth and Hanover areas due to trees falling on utility lines.

From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.

The warnings

14 minutes of warning. NWS DVN issued a tornado warning for this county at 17:16 UTC, 14 minutes before the tornado touched down, in force until 17:50 UTC.

Issued (UTC)ExpiredProductOffice
17:13 UTC17:45 UTCSevere Thunderstorm WarningDVN
17:16 UTC17:50 UTCTornado WarningDVN

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 forecast that day

The Storm Prediction Center had this point in a Moderate Risk. The outlook in force was issued at 11:01 UTC.

SPC's Day 1 convective outlook as it stood when the tornado began, read at the touchdown point. The same archive is on the radar archive.

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.

Davenport, (KDVN), 12:00Z

5.5 hours before the tornado, 91 km from the path. August 24, 1998.

Skew-T log-pSkew-T log-p diagram, Davenport, at 12:00Z on 1998-08-24Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 2161 joules per kilogram, CIN -158, lifted condensation level 1178 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, Davenport, at 12:00Z on 1998-08-24The 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 54 square meters per square second, 0 to 6 km bulk shear 37 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
2161 J/kg
Mixed-layer CIN
-158 J/kg
Surface CAPE
1258 J/kg
Mixed-layer LCL
1178 m above ground
0-6 km bulk shear
37 kt
0-1 km bulk shear
17 kt
0-1 km storm-relative helicity
54 m²/s²
0-3 km storm-relative helicity
128 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.1
0-3 km lapse rate
3.7 K/km

Open this sounding in Storm Lab

Davenport, (KDVN), 00:00Z

6.5 hours after it, 91 km from the path. August 25, 1998.

Skew-T log-pSkew-T log-p diagram, Davenport, at 00:00Z on 1998-08-25Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 48 joules per kilogram, CIN -493, lifted condensation level 2109 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, Davenport, at 00:00Z on 1998-08-25The 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 276 square meters per square second, 0 to 6 km bulk shear 51 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
48 J/kg
Mixed-layer CIN
-493 J/kg
Surface CAPE
2092 J/kg
Mixed-layer LCL
2109 m above ground
0-6 km bulk shear
51 kt
0-1 km bulk shear
27 kt
0-1 km storm-relative helicity
276 m²/s²
0-3 km storm-relative helicity
441 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.3
0-3 km lapse rate
5.2 K/km

Open this sounding in Storm Lab

The surface observations

Monroe (EFT), 43 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
15:35 UTC7769.80° 0 kt1008.5
15:54 UTC26.621.20° 0 kt1008.8
16:15 UTC7771.60° 0 kt1009.1
16:35 UTC75.271.60° 0 kt1009.5
16:55 UTC75.273.40° 0 kt1009.5
17:15 UTC73.471.6300° 9 kt1011.5-RA
17:35 UTC73.471.6260° 18 kt301013.5
17:55 UTC71.666.2310° 5 kt1011.9RA
18:15 UTC69.869.80° 0 kt1009.5-RA
18:35 UTC69.869.8270° 4 kt1011.2-RA
18:55 UTC69.869.8120° 3 kt1009.8RA FG
19:15 UTC71.669.80° 0 kt1009.5

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

This ground now

The live radar over the trackEvery 1998 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

The other tornadoes of August 24, 1998

2 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
August 249:00 AM EDTF1Medina, OH0.530$70,000
August 2412:30 PM CDTF0Terrebonne Parish, LA0.130

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.