EF2 tornado, Patch Grove, Wisconsin, September 4, 2012

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 mph

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

3. EF2111 to 135 mphthis tornado

   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

EF2

Date

September 4, 2012

Touchdown

7:37 PM CDT (00:37 UTC)

Lifted

7:43 PM CDT (00:43 UTC)

On the ground

6 minutes

Path length

0.7 miles (1.2 km)

Path width

75 yards (69 m)

Deaths

0

Injuries

0

Property damage

$420,000

Crop damage

$8,000

County

Grant County

Touchdown point

42.909, -90.995

Lift-off point

42.903, -90.984

Record number

1209041837-01

Two rounds of thunderstorms impacted parts of western and central Wisconsin on September 4th and 5th. The first event, which was more significant, produced an EF2 tornado outside of Bloomington (Grant County), large hail and damaging winds during the afternoon and evening of the 4th. The tornado demolished or damaged all the buildings on one farm before dissipating. Several trees and a barn were blown down across western Vernon County between Genoa and De Soto. The largest hail reported was golf ball at Genoa and Red Mound (Vernon County). The second round of storms during the early morning hours of the 5th blew down some more trees across western Vernon County.

A slow moving tornado formed on the edge of a passing severe thunderstorm between Patch Grove and Bloomington. The tornado was mainly confined to one landowner near Hickory and Maine Roads in rural Grant County. Several outbuildings, a barn, and the home were demolished or heavily damaged. Trees on the property were also sheared off or blown over. Considering the roof was torn off and several walls were down or damaged, the tornado was rated an EF2 but it's possible the slow movement allowed the tornado to remain nearly stationary long enough to cause worse damage. Interviews by local residents and video evidence suggests the tornado may have moved to the northwest at times as well.

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

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 20:27 UTC and running to 04:00 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 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 19:40 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), 103 km away, was scanning. The volume nearest the touchdown began at 00:38 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.

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 2012 tornado in WisconsinEvery tornado in Wisconsin since 1950Warnings in force in Wisconsin nowThe forecast where you are

1 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.