Tornadoes · United States · Illinois · 2002
F0 tornado, Zion, Illinois, April 18, 2002
This F0 tornado ran 0.1 miles across Lake County on April 18, 2002, touching down at 7:43 PM CDT and reaching 20 yards wide. It killed nobody.
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.
F040 to 72 mphthis tornado
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
F173 to 112 mph
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
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.
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.
F4207 to 260 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
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.
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
- F0
- Date
- April 18, 2002
- Touchdown
- 7:43 PM CDT (00:43 UTC)
- Path length
- 0.1 miles (0.2 km)
- Path width
- 20 yards (18 m)
- Deaths
- 0
- Injuries
- 0
- County
- Lake County
- Touchdown point
- 42.450, -87.800
- Lift-off point
- 42.450, -87.800
- Record number
- 28
What the Weather Service recorded
Severe Thunderstorms moved across far northern Illinois during the evening of Thursday April 18th. Hail 2 and 1/2 inches in diameter fell in Forreston in Ogle county causing minor damage to parked cars. Several three foot diameter trees were broken off 10 feet above the ground in a cemetary west of Rockford in Winnebago county. Winds were measured at 66 mph in Lake Villa at 715 pm CDT. The most significant damage was in a retirement community northeast of the intersection of highway 60 and Peterson road near Round Lake Park. The winds damaged roofs, porches and windows on 15 to 20 homes. The damage was confined to a narrow path about a block wide and half a mile long. Further east in Lake county, an F0 tornado briefly touched down on the beach east of Zion before moving offshore as a waterspout.
From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.
The warnings
No tornado warning for this county appears in the archive as in force at the moment the tornado touched down.
| Issued (UTC) | Expired | Product | Office |
|---|---|---|---|
| 00:23 UTC | 02:00 UTC | Marine Warning | LOT |
| 04:12 UTC | 06:15 UTC | Marine Warning | LOT |
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 no categorical risk area, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 20:17 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.
Green Bay/Straub, WI (KGRB), 00:00Z
0.7 hours before the tornado, 227 km from the path. April 19, 2002.
- Mixed-layer CAPE
- 188 J/kg
- Mixed-layer CIN
- -106 J/kg
- Surface CAPE
- 514 J/kg
- Mixed-layer LCL
- 2321 m above ground
- 0-6 km bulk shear
- 42 kt
- 0-1 km bulk shear
- 37 kt
- 0-1 km storm-relative helicity
- 216 m²/s²
- 0-3 km storm-relative helicity
- 288 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
- 0-3 km lapse rate
- 7.0 K/km
Green Bay/Straub, WI (KGRB), 12:00Z
11.3 hours after it, 227 km from the path. April 19, 2002.
- Mixed-layer CAPE
- 1 J/kg
- Mixed-layer CIN
- 0 J/kg
- Surface CAPE
- 11 J/kg
- Mixed-layer LCL
- 617 m above ground
- 0-6 km bulk shear
- 56 kt
- 0-1 km bulk shear
- 9 kt
- 0-1 km storm-relative helicity
- -26 m²/s²
- 0-3 km storm-relative helicity
- 173 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
- 0-3 km lapse rate
- 2.6 K/km
The surface observations
Waukegan (UGN), 6 km from the path, in the two hours either side.
| Time (UTC) | Temp (°F) | Dew point (°F) | Wind | Gust (kt) | Pressure (mb) | Weather |
|---|---|---|---|---|---|---|
| 22:55 UTC | 85 | 57 | 200° 11 kt | 1006.8 | ||
| 23:55 UTC | 85 | 54 | 200° 14 kt | 22 | 1006.8 | VCTS |
| 00:42 UTC | 60.8 | 57.2 | 330° 11 kt | 38 | 1008.5 | +TSRA BR |
| 00:48 UTC | 62.6 | 57.2 | 330° 9 kt | 26 | 1007.5 | +TSRA BR |
| 00:55 UTC | 62 | 59 | 310° 6 kt | 1007.1 | -TSRA BR | |
| 01:06 UTC | 64.4 | 57.2 | 340° 10 kt | 1007.5 | VCTS -RA | |
| 01:13 UTC | 62.6 | 57.2 | 330° 8 kt | 1007.8 | -TSRA | |
| 01:55 UTC | 64 | 61 | 0° 0 kt | 1007.1 |
From the Iowa Environmental Mesonet's archive of airport observations.
This ground now
The live radar over the trackEvery 2002 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are
The other tornadoes of April 18, 2002
13 more were confirmed in the United States that day.
| Date | Time | Rating | Where | Path (mi) | Width (yd) | Deaths | Injuries | Damage |
|---|---|---|---|---|---|---|---|---|
| April 18 | 1:39 AM CDT | F0 | Alfalfa, OK | 0.8 | 75 | |||
| April 18 | 4:49 PM CDT | F0 | Lincoln, WI | 0.1 | 25 | |||
| April 18 | 4:57 PM CDT | F0 | Oneida, WI | 0.1 | 25 | |||
| April 18 | 5:33 PM CDT | F0 | Oneida, WI | 0.1 | 25 | |||
| April 18 | 6:00 PM CDT | F0 | Hardin, IA | 0.2 | 25 | $1,000 | ||
| April 18 | 6:29 PM CDT | F0 | Price, WI | 0.1 | 40 | |||
| April 18 | 6:30 PM CDT | F0 | McPherson, KS | 0.5 | 55 | |||
| April 18 | 6:30 PM CDT | F0 | Grundy, IA | 0.2 | 30 | $1,000 | ||
| April 18 | 6:49 PM CDT | F0 | Polk, IA | 0.3 | 30 | $1,000 | ||
| April 18 | 6:50 PM CDT | F1 | Polk, IA | 8.5 | 60 | $10,000 | ||
| April 18 | 7:08 PM CDT | F0 | Black Hawk, IA | 0.3 | 30 | $1,000 | ||
| April 18 | 7:13 PM CDT | F1 | Marathon, WI | 14.0 | 100 | $1.4 million | ||
| April 18 | 7:32 PM CDT | F0 | Marathon, WI | 0.1 | 25 |
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.