Tornadoes · United States · Wisconsin · 2020
EF0 tornado, Zenda to Lake Geneva, Wisconsin, August 10, 2020
From Zenda to Lake Geneva, this EF0 tornado ran 3.3 miles across Walworth County on August 10, 2020, touching down at 3:38 PM CDT and reaching 50 yards wide. It killed nobody, and did $12,000 of property damage.
The rating scale
Tracks are drawn in the color of the rating. The Enhanced Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.
EF065 to 85 mphthis tornado
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
EF186 to 110 mph
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
EF2111 to 135 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.
EF3136 to 165 mph
Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.
EF4166 to 200 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
EF5over 200 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
- EF0
- Date
- August 10, 2020
- Touchdown
- 3:38 PM CDT (20:38 UTC)
- Lifted
- 3:42 PM CDT (20:42 UTC)
- On the ground
- 4 minutes
- Path length
- 3.3 miles (5.3 km)
- Path width
- 50 yards (46 m)
- Deaths
- 0
- Injuries
- 0
- Property damage
- $12,000
- County
- Walworth County
- Touchdown point
- 42.557, -88.446
- Lift-off point
- 42.593, -88.405
- Record number
- 2008101438-01
The damage survey
73 damage points were recorded along this path by NWS MKX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 94 mph.
- Splatter on side of building?
- Tree is 30 feet to the south
- trunk snapped in middle. didn’t fall on house to NE
- not sure where this came from. further south
Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.
What the Weather Service recorded
A line of severe thunderstorms ahead of an approaching cold front brought two tornadoes, flash flooding, and straight-line wind damage to far southern WI.
Weak tornado started on the southeast end of Geneva Lake and went through the southeast side of Lake Geneva. Mainly tree damage along the path, but some minor structural damage in the business district bounded by highways 120, 50 and 12. Path appeared to end just south of the Grand Geneva resort.
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. One was issued for the county at another hour that day.
The county was under a severe thunderstorm watch, issued at 16:26 UTC and running to 22:23 UTC.
| Issued (UTC) | Expired | Product | Office |
|---|---|---|---|
| 16:26 UTC | 22:23 UTC | Severe Thunderstorm Watch | MKX |
| 19:29 UTC | 20:30 UTC | Severe Thunderstorm Warning | MKX |
| 20:13 UTC | 21:00 UTC | Severe Thunderstorm Warning | MKX |
| 20:42 UTC | 20:58 UTC | Tornado Warning | MKX |
| 21:34 UTC | 00:45 UTC | Flood Advisory | MKX |
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, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 19:38 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
8.6 hours before the tornado, 201 km from the path. August 10, 2020.
- Mixed-layer CAPE
- 1683 J/kg
- Mixed-layer CIN
- -223 J/kg
- Surface CAPE
- 2014 J/kg
- Mixed-layer LCL
- 894 m above ground
- 0-6 km bulk shear
- 19 kt
- 0-1 km bulk shear
- 18 kt
- 0-1 km storm-relative helicity
- 80 m²/s²
- 0-3 km storm-relative helicity
- 96 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.1
- 0-3 km lapse rate
- 3.8 K/km
Davenport, (KDVN), 00:00Z
3.4 hours after it, 201 km from the path. August 11, 2020.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- -3409 J/kg
- Surface CAPE
- 75 J/kg
- Mixed-layer LCL
- 1429 m above ground
- 0-6 km bulk shear
- 43 kt
- 0-1 km bulk shear
- 9 kt
- 0-1 km storm-relative helicity
- -60 m²/s²
- 0-3 km storm-relative helicity
- -33 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
- 0-3 km lapse rate
- 4.4 K/km
The radar
The Milwaukee radar (KMKX), 45 km away, was scanning. The volume nearest the touchdown began at 20:38 UTC.
Open the radar archive at this moment, over the track
Reflectivity and velocity, decoded from the Level II archive in the browser. Volumes take a few seconds to open the first time.
What was reported nearby
Local storm reports within 60 km of the path, in the three hours either side.
| Time (UTC) | Report | Where | County | Remark |
|---|---|---|---|---|
| 19:30 UTC | TSTM WND DMG | 4 W Avalon | Rock, WI | TREE DOWN ACROSS ROAD AT LOCATION. REPORT RELAYED VIA PICTURE ON SOCIAL MEDIA. TIME ESTIMATED FROM RADAR. |
| 20:38 UTC | TSTM WND DMG | 1 Sse Lake Geneva | Walworth, WI | MULTIPLE TREES DOWN ON LAKE GENEVA BLVD AND WEST SOUTH STREET. REPORT PASSED ALONG BY BROADCAST MEDIA. TIME ESTIMATED FROM RADAR. |
| 20:38 UTC | TSTM WND DMG | Lake Geneva | Walworth, WI | MULTIPLE REPORTS OF TREES AND TREE LIMBS DOWN IN THE CITY OF LAKE GENEVA. TIME ESTIMATED BASED ON RADAR. |
| 20:38 UTC | TORNADO | 1 S Lake Geneva | Walworth, WI | STORM SURVEY CREW FOUND DAMAGE CONSISTENT WITH A HIGH END EF-0 IN LAKE GENEVA. WINDS UPWARDS OF 80 MPH OCCURRED AND MUCH OF THE DAMAGE WAS TO TREES. LARGE LIMBS AND TREE TRUNKS KNOCKED DOWN OR SNAPPED. TIME IS ESTIMATED |
| 20:45 UTC | TSTM WND DMG | 2 Ssw Camp Lake | Kenosha, WI | CORRECTS PREVIOUS FLOOD REPORT FROM 2 SSW CAMP LAKE. NUMEROUS TREES DOWN AND SNAPPED AT WILMOT AND 286TH. REPORT RELAYED VIA SOCIAL MEDIA. TIME ESTIMATED FROM RADAR. |
| 20:45 UTC | FLOOD | 2 Ssw Camp Lake | Kenosha, WI | NUMEROUS TREES DOWN AND SNAPPED AT WILMOT AND 286TH. REPORT RELAYED VIA SOCIAL MEDIA. TIME ESTIMATED FROM RADAR. |
| 20:45 UTC | TORNADO | 2 Ssw Camp Lake | Kenosha, WI | DAMAGE TO BUILDINGS AND TREES CONSISTENT WITH A LOW END EF-1 TORNADO OCCURRED IN NORTHERN ILLINOIS JUST SOUTH OF THE WISCONSIN STATE LINE. THIS TORNADO PROCEEDED NE INTO WISCONSIN TOWARDS CAMP LAKE WHERE MAINLY TREE DAMA |
| 20:47 UTC | TSTM WND DMG | 1 Se Camp Lake | Kenosha, WI | TREE SNAPPED AT LOCATION. REPORT RELAYED VIA SOCIAL MEDIA. TIME ESTIMATED FROM RADAR. |
| 20:47 UTC | TSTM WND DMG | Camp Lake | Kenosha, WI | MULTIPLE REPORTS OF TREES AND WIRES DOWN AROUND THE CAMP LAKE AREA. |
| 20:52 UTC | TSTM WND DMG | 1 E Powers Lake | Kenosha, WI | TREES DOWN AROUND THE INTERSECTION OF HWY Z AND HWY P IN POWERS LAKE. |
| 20:55 UTC | TSTM WND DMG | Pell Lake | Walworth, WI | REPORTS RELAYED VIA SOCIAL MEDIA OF POWERLINES AND LARGE TREE BRANCHES DOWN WITH ESTIMATED 70 MPH WINDS. TIME ESTIMATED BASED ON RADAR. |
| 20:55 UTC | TSTM WND GST 70 | Paddock Lake | Kenosha, WI | |
| 21:00 UTC | TSTM WND DMG | Elkhorn | Walworth, WI | NUMEROUS REPORTS OF TREES, TREE LIMBS, AND POWERLINES DOWN ACROSS WALWORTH COUNTY. |
| 21:07 UTC | TSTM WND DMG | 1 Wnw Kenosha | Kenosha, WI | LARGE TREE BRANCHES DOWN IN THE CITY OF KENOSHA. REPORT RELAYED VIA SOCIAL MEDIA. |
| 21:09 UTC | TSTM WND GST 60 | Powers Lake | Kenosha, WI | |
| 21:10 UTC | TSTM WND DMG | Union Grove | Racine, WI | SEVERAL REPORTS OF TREE DOWN IN UNION GROVE. TIME ESTIMATED BY RADAR. |
| 21:13 UTC | TSTM WND DMG | 1 Ssw Elmwood Park | Racine, WI | TWO MATURE PINE TREES DOWN AROUND LATHROP AVE AND FOXWOOD RD IN MT. PLEASANT. TIME ESTIMATED BY RADAR. |
| 21:13 UTC | TSTM WND DMG | 2 Wnw Elmwood Park | Racine, WI | LARGE LIMBS DOWN AND DAMAGE TO SIDING. REPORT RELAYED VIA SOCIAL MEDIA. TIME ESTIMATED FROM RADAR. |
| 21:15 UTC | TSTM WND DMG | Elmwood Park | Racine, WI | LARGE TREE LIMBS DOWN AT LOCATION. |
| 21:21 UTC | TSTM WND DMG | North Bay | Racine, WI | LARGE BRANCHES DOWN. REPORT RELAYED VIA SOCIAL MEDIA. TIME ESTIMATED FROM RADAR. |
| 21:48 UTC | FLOOD | Waterford | Racine, WI | FLOODING OVER INTERSECTION OF JEFFERSON ST. AND WASHINGTON ST. IN WATERFORD. |
| 21:49 UTC | HEAVY RAIN 3.9 | 1 N Elkhorn | Walworth, WI | 3.9â RAINFALL MEASURED AS OF 4:49PM. ROADWAY FLOODING JUST WEST OF INTERSECTION OF HWY 67 AND HIDDEN TRAIL RD. |
| 21:49 UTC | HEAVY RAIN 3.9 | 1 N Elkhorn | Walworth, WI | 3.9 RAINFALL MEASURED AS OF 4:49PM. ROADWAY FLOODING JUST WEST OF INTERSECTION OF HWY 67 AND HIDDEN TRAIL RD. |
| 21:55 UTC | TSTM WND DMG | 2 Nnw Elmwood Park | Racine, WI | LARGE TREE LIMBS DOWN AT LOCATION. |
| 21:55 UTC | HEAVY RAIN 2.55 | Kenosha | Kenosha, WI | RAINFALL AS 4:55 PM. |
| 22:00 UTC | TSTM WND DMG | 1 N Elmwood Park | Racine, WI | TREE REPORTED DOWN AT LOCATION. |
| 22:00 UTC | FLOOD | 2 Wnw Wind Point | Racine, WI | FOUR CARS STALLED IN 2 TO 3 FEET OF STANDING WATER ON DOUGLAS AVE. NEAR MIDDLE RD. |
| 22:01 UTC | FLOOD | 4 W Franksville | Racine, WI | FLOODING OVER ROADWAY REPORTED AT 51ST ST AND 2 MILE ROAD IN RACINE CTY. |
| 22:07 UTC | FLOOD | 1 E Franksville | Racine, WI | CORRECTS PREVIOUS FLASH FLOOD REPORT FROM 1 E FRANKSVILLE. FLOODING ON NORTHWESTERN AVE IN RACINE CTY. |
| 22:07 UTC | FLOOD | 2 W Franksville | Racine, WI | WATER OVER ROADWAY ON GOLF RD. |
| 22:07 UTC | FLASH FLOOD | 1 E Franksville | Racine, WI | FLOODING ON NORTHWESTERN AVE IN RACINE CTY. |
| 22:07 UTC | FLASH FLOOD | 2 Wnw Racine | Racine, WI | A SINK HOLE FORMED ALONG THE ROAD IN QUARRY LAKE PARK AS A RESULT OF FLASH FLOODING. TIME ESTIMATED BASED OFF RADAR. |
| 22:13 UTC | FLOOD | 2 Ese Oak Creek | Milwaukee, WI | WATER ACROSS ROADWAY. REPORT RELAYED VIA SOCIAL MEDIA. |
| 22:20 UTC | FLOOD | 1 Nne Elkhorn | Walworth, WI | STREET FLOODING ON 1ST AVE IN ELKHORN. VIDEO AND REPORT RELAYED VIA BROADCAST MEDIA. |
| 22:25 UTC | FLOOD | 2 S Oak Creek | Milwaukee, WI | WATER OVER THE ROAD AT THE INTERSECTION OF ELM RD & NICHOLSON RD. IN OAK CREEK. |
| 22:32 UTC | HEAVY RAIN 3 | 1 Nnw Racine | Racine, WI | 3 INCHES OF RAIN IN JUST UNDER AN HOUR WITH STREET FLOODING. |
From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.
This ground now
The live radar over the trackEvery 2020 tornado in WisconsinEvery tornado in Wisconsin since 1950Warnings in force in Wisconsin nowThe forecast where you are
The other tornadoes of August 10, 2020
26 more were confirmed in the United States that day.
| Date | Time | Rating | Where | Path (mi) | Width (yd) | Deaths | Injuries | Damage |
|---|---|---|---|---|---|---|---|---|
| August 10 | 11:30 AM CDT | Unrated | Marshall, IA | 1.0 | 50 | |||
| August 10 | 11:36 AM CDT | Unrated | Marshall, IA | 0.4 | 50 | |||
| August 10 | 11:39 AM CDT | EF1 | Marshall, IA | 2.9 | 100 | $20,000 | ||
| August 10 | 12:01 PM CDT | Unrated | Tama, IA | 1.5 | 40 | |||
| August 10 | 12:31 PM CDT | Unrated | Linn, IA | 0.9 | 40 | |||
| August 10 | 12:32 PM CDT | EF0 | Grant, WI | 0.6 | 50 | $15,000 | ||
| August 10 | 2:12 PM CDT | EF0 | Stephenson, IL | 4.6 | 50 | |||
| August 10 | 2:37 PM CDT | EF0 | Winnebago, IL | 1.6 | 50 | |||
| August 10 | 2:47 PM CDT | EF1 | Winnebago, IL | 9.2 | 300 | |||
| August 10 | 2:50 PM CDT | EF0 | DeKalb, IL | 6.3 | 40 | |||
| August 10 | 2:59 PM CDT | EF1 | LaSalle, IL | 0.9 | 150 | |||
| August 10 | 3:05 PM CDT | EF1 | McHenry, IL | 5.7 | 200 | |||
| August 10 | 3:12 PM CDT | EF1 | Kane, IL | 1.2 | 40 | |||
| August 10 | 3:15 PM CDT | EF1 | Kendall, IL | 14.4 | 250 | |||
| August 10 | 3:35 PM CDT | EF1 | DuPage, IL | 0.4 | 100 | |||
| August 10 | 3:39 PM CDT | EF1 | DuPage, IL | 2.1 | 200 | |||
| August 10 | 3:41 PM CDT | EF1 | Lake, IL to WI | 6.3 | 150 | $250,000 | ||
| August 10 | 3:54 PM CDT | EF1 | Cook, IL | 4.8 | 300 | |||
| August 10 | 3:57 PM CDT | EF0 | Cook, IL | 2.0 | 350 | |||
| August 10 | 3:59 PM CDT | EF1 | Cook, IL | 3.2 | 300 | |||
| August 10 | 4:04 PM CDT | EF0 | Kankakee, IL | 1.5 | 150 | |||
| August 10 | 5:05 PM EDT | EF1 | Washington, NY | 1.5 | 100 | $75,000 | ||
| August 10 | 4:15 PM CDT | EF0 | Newton, IN | 0.9 | 40 | |||
| August 10 | 6:32 PM EDT | EF1 | Saint Joseph, IN | 2.4 | 100 | |||
| August 10 | 6:55 PM EDT | EF1 | Kosciusko, IN | 3.1 | 100 | |||
| August 10 | 7:43 PM EDT | EF0 | Kosciusko, IN | 0.2 | 50 |
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.