EF0 tornado, Clyde, North Dakota, July 11, 2017

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 11, 2017

Touchdown

5:48 PM CDT (22:48 UTC)

Lifted

5:50 PM CDT (22:50 UTC)

On the ground

2 minutes

Path length

0.4 miles (0.6 km)

Path width

100 yards (91 m)

Deaths

0

Injuries

0

County

Cavalier County

Touchdown point

48.770, -98.790

Lift-off point

48.770, -98.790

Record number

1707111648-01

2 damage points were recorded along this path by NWS FGF, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF0. The highest wind the damage implies is 70 mph.

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

After morning showers moved through eastern North Dakota and northwest Minnesota, clouds decreased and allowed for some decent afternoon warming. Highs warmed into the low 90s over all of east central and southeast North Dakota, along with dew point values in the lower 70s. Thunderstorms formed a little later than initially thought, partly due to the morning clouds. The storms initially formed over northeast North Dakota during the late afternoon, but expanded east and southeast throughout the evening. These storms produced large hail, strong winds, and multiple tornadoes. One of the tornadoes had a particularly long track, taking it from just north of the Mayville radar site to just northeast of Hillsboro.

A brief tornado touchdown was noted by an observer near the corner of the intersection of county roads 5 and 20. The tornado tracked through open country. Peak winds were estimated at 70 mph.

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

33 minutes of warning. NWS FGF issued a tornado warning for this county at 22:15 UTC, 33 minutes before the tornado touched down, in force until 23:00 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 19:35 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.

Langdon (D55), 29 km from the path, in the two hours either side.

From the Iowa Environmental Mesonet's archive of airport observations.

The Minot AFB radar (KMBX), 158 km away, was scanning. The volume nearest the touchdown began at 22:46 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 2017 tornado in North DakotaEvery tornado in North Dakota since 1950Warnings in force in North Dakota nowThe forecast where you are

12 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.