EF1 tornado, Wendell to Evansville, Minnesota, August 7, 2010

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, 2010

Touchdown

7:35 PM CDT (00:35 UTC)

Lifted

8:12 PM CDT (01:12 UTC)

On the ground

37 minutes

Path length

21.0 miles (33.8 km)

Path width

100 yards (91 m)

Deaths

0

Injuries

0

Property damage

$25,000

Counties

Grant and Douglas counties

Touchdown point

46.050, -96.100

Lift-off point

46.002, -95.680

Record number

1008071835-01

By late in the day on the 7th, an east-west lying warm front had set up just north of the South Dakota border, extending eastward into west central Minnesota. South of the warm front, temperatures were in the mid to upper 80s with dew points in the lower 70s. Thunderstorms formed along and north of the warm front and several produced tornadoes.

Several short-lived supercell thunderstorms moved across portions of west-central and into east-central Minnesota during the mid to late evening hours of Saturday, August 7th. One of the severe thunderstorms produced a tornado near Evansville, Minnesota, with reports of straight-line wind damage as far east as the northern portions of the Twin Cities. These storms moved into west-central Wisconsin and produced more damaging winds.

This tornado tracked intermittently for nearly 16 miles, to about 3 miles east of Erdahl. At this point, it continued into Douglas County. The tornado broke down numerous trees and large tree limbs along its path. At times, the tornado was wrapped in very heavy rains. Peak winds were estimated at 100 mph.

A National Weather Service Storm Damage Survey from the Grand Forks, North Dakota Office determined that an EF-1 tornado touched down about one mile north of Wendell in Grant County, and had an intermittent track east-southeast through Grant County. It then moved east across northwestern Douglas County to the south side of Evansville, before lifting. Total path length from Grant County into Douglas County was about 21 miles. Damage was confined to large trees, but several power poles were blown down in Evansville, causing a city wide power outage.

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

37 minutes of warning. NWS FGF issued a tornado warning for this county at 23:58 UTC, 37 minutes before the tornado touched down, in force until 01:00 UTC.

The county was under a tornado watch, issued at 22:29 UTC and running to 02:56 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 19:46 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 Fargo/Grand Forks radar (KMVX), 200 km away, was scanning. The volume nearest the touchdown began at 00:37 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 2010 tornado in MinnesotaEvery tornado in Minnesota since 1950Warnings in force in Minnesota nowThe forecast where you are

10 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.