EF0 tornado, Grassy Butte, North Dakota, July 22, 2011

1. EF065 to 85 mphthis tornado

   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 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

EF0

Date

July 22, 2011

Touchdown

8:23 PM CDT (01:23 UTC)

Lifted

8:24 PM CDT (01:24 UTC)

On the ground

1 minutes

Path length

0.5 miles (0.7 km)

Path width

30 yards (27 m)

Deaths

0

Injuries

0

Property damage

$100,000

County

McKenzie County

Touchdown point

47.590, -103.260

Lift-off point

47.589, -103.250

Record number

1107221923-01

A severe thunderstorm outbreak materialized over west and south central North Dakota in the late afternoon and evening hours of July 22nd, lasting into the early morning hours of the 23rd. Tornado watch numbers 673, 674, and 675 were in effect for this event. A tornadic storm developed over south central North Dakota along a surface warm front. Much of the severe weather for this event originated over eastern Montana associated with a strong upper level jet streak. This activity pushed into western North Dakota, and tracked eastward throughout the evening. The severe weather event resulted in large hail, high winds, tornadoes, and flash floods.

A brief tornado occurred and resulted in a traffic accident with injuries (indirect). A local newpaper article stated that a semi truck hit a downed power line which cut into the cab of the truck. The line then snapped, sending it into a parked vehicle. The semi truck then collided with a third vehicle. Two people were injured (indirect) during this accident. This chain of events occurred after the tornado had passed, leaving the downed line in its wake. The tornado damage to the power line corresponded to EF0 on the Enhanced Fujita Scale.

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

17 minutes of warning. NWS BIS issued a tornado warning for this county at 01:06 UTC, 17 minutes before the tornado touched down, in force until 01:45 UTC.

The county was under a tornado watch, issued at 22:40 UTC and running to 05:02 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 Moderate Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 00:51 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.

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 2011 tornado in North DakotaEvery tornado in North Dakota since 1950Warnings in force in North Dakota nowThe forecast where you are

4 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.