EF0 tornado, Oakwood to Grafton, North Dakota, May 28, 2015

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

May 28, 2015

Touchdown

5:17 PM CDT (22:17 UTC)

Lifted

5:21 PM CDT (22:21 UTC)

On the ground

4 minutes

Path length

2.0 miles (3.2 km)

Path width

100 yards (91 m)

Deaths

0

Injuries

0

County

Walsh County

Touchdown point

48.370, -97.240

Lift-off point

48.365, -97.199

Record number

1505281617-01

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 85 mph.

• Several 12 to 18 inch diameter cottonwood trees were snapped at a farmstead.
• Large tree branches broken down is two shelterbelts along path.

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

By the afternoon of the 28th, a weak surface low was located over northeast North Dakota with a warm front extending out to the east. Temperatures rose into the mid to upper 70s with dew points in the low 60s. Showers and thunderstorms flared up along the Red River Valley into northwest Minnesota, producing large hail and strong wind gusts.

The tornado tracked for about two miles across southern Acton Township. Several medium to large cottonwood trees twelve to eighteen inches in diameter were snapped near the ground and numerous tree branches and limbs were broken off in shelterbelts along the path. Peak winds were estimated at 85 mph.

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

6 minutes of warning. NWS FGF issued a tornado warning for this county at 22:11 UTC, 6 minutes before the tornado touched down, in force until 22:29 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 Marginal Risk. The outlook in force was issued at 19:32 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.

Grafton (GAF), 12 km from the path, in the two hours either side.

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

The Fargo/Grand Forks radar (KMVX), 94 km away, was scanning. The volume nearest the touchdown began at 22:18 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 2015 tornado in North DakotaEvery tornado in North Dakota since 1950Warnings in force in North Dakota nowThe forecast where you are

13 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.