EF1 tornado, Highland to Pine Knob, Wisconsin, August 7, 2021

1. EF065 to 85 mph

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. EF186 to 110 mphthis tornado

   Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

3. 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.

4. 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.

5. EF4166 to 200 mph

   Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

6. 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.

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.

Rating

EF1

Date

August 7, 2021

Touchdown

5:09 PM CDT (22:09 UTC)

Lifted

5:24 PM CDT (22:24 UTC)

On the ground

15 minutes

Path length

7.7 miles (12.4 km)

Path width

50 yards (46 m)

Deaths

0

Injuries

0

County

Iowa County

Touchdown point

43.080, -90.394

Lift-off point

43.062, -90.243

Record number

2108071609-01

71 damage points were recorded along this path by NWS ARX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF3. The highest wind the damage implies is 160 mph.

• Extensive tree damage east of here.
• Edge of track. More likely inflow than actual tornado.
• Extensive tree damage. House damage might have been by tree.
• Houses were shielded. Severe tree damage.

Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.

A few supercell thunderstorms developed over western Wisconsin and move east into southern Wisconsin. These eventually morphed into more of a thunderstorm complex as they entered southern Wisconsin. Strong to severe storms caused pockets of wind damage and a tornado.

This tornado spawned off of the same storm that produced the EF-3 tornado near Boscobel, but was clearly of a different track. This EF-1 went through mainly rural areas north to northeast of Highland. The main damage occurred to a farm off of Camp Rd, which was close to the beginning of the path. Mainly tree damage was noted along the rest of the path.

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

31 minutes of warning. NWS MKX issued a tornado warning for this county at 21:38 UTC, 31 minutes before the tornado touched down, in force until 22:45 UTC.

The county was under a severe thunderstorm watch, issued at 21:36 UTC and running to 02:00 UTC.

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 Storm Prediction Center had this point in a Slight Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 19:55 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 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.

The La Crosse radar (KARX), 109 km away, was scanning. The volume nearest the touchdown began at 22:09 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.

Local storm reports within 60 km of the path, in the three hours either side.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

The live radar over the trackEvery 2021 tornado in WisconsinEvery tornado in Wisconsin since 1950Warnings in force in Wisconsin nowThe forecast where you are

2 more were confirmed in the United States that day.

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.

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.