EF1 tornado, (Gcc)Gillette Arpt, Wyoming, June 1, 2018

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

June 1, 2018

Touchdown

1:59 PM MDT (19:59 UTC)

Lifted

2:07 PM MDT (20:07 UTC)

On the ground

8 minutes

Path length

4.6 miles (7.4 km)

Path width

50 yards (46 m)

Deaths

0

Injuries

0

County

Campbell County

Touchdown point

44.379, -105.552

Lift-off point

44.391, -105.460

Record number

1806011359-01

34 damage points were recorded along this path by NWS UNR, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF3. The highest wind the damage implies is 136 mph.

• rebar anchored to frame and blocks
• rebar welded to frame that was anchored to concrete, otherwise unit would have rolled
• building not anchored, likely RFD/straight line winds
• Possible straight line winds and/or tornado

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

A supercell thunderstorm tracked east-northeast across central Campbell County. As the storm approached Gillette, it produced multiple tornadoes. A storm survey, along with photos and video, determined that four tornadoes occurred just west and north of Gillette. The largest tornado was on the ground for about ten minutes and briefly reached EF-3 strength as it tracked about ten miles west-northwest of Gillette. There were two injuries, with significant damage to numerous buildings and homes along its path.

A brief tornado touched down about ten miles west of downtown Gillette between Montgomery Road and Echeta Road, south of the Oriva Hills subdivision. It was on the ground for about four minutes. Since it left no visible damage, the tornado was rated as EF-0.

A short-lived landspout tornado developed three miles north-northeast of downtown Gillette in the Warrior Hills subdivision. It damaged a large shed, flipped a camper onto a vehicle, destroyed another camper, and damaged several wooded fences. Winds were estimated at 80 to 90 mph, giving the tornado a rating as a weak EF-1.

The tornado touched down over the west pit of the Eagle Butte Mine, about seven miles north of downtown Gillette. The tornado traveled east-northeast for about eight minutes before dissipating just east of the Dry Fork Power Plant. The tornado snapped and bent over seven power poles, damaged the control room building at the mine, and damaged several vehicles at the Eagle Butte Mine and Dry Fork Power Plant. With wind speeds estimated at 100 mph, the tornado was rated as an EF-1.

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

19 minutes of warning. NWS UNR issued a tornado warning for this county at 19:40 UTC, 19 minutes before the tornado touched down, in force until 20:15 UTC.

The county was under a severe thunderstorm watch, issued at 17:48 UTC and running to 22:08 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. The outlook in force was issued at 16:45 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.

Gillette (GCC), 5 km from the path, in the two hours either side.

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

The Rapid City radar (KUDX), 215 km away, was scanning. The volume nearest the touchdown began at 19:59 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 2018 tornado in WyomingEvery tornado in Wyoming since 1950Warnings in force in Wyoming nowThe forecast where you are

14 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.