EF1 tornado, Irvine, Wyoming, July 28, 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

July 28, 2018

Touchdown

4:20 PM MDT (22:20 UTC)

Lifted

4:28 PM MDT (22:28 UTC)

On the ground

8 minutes

Path length

1.8 miles (2.9 km)

Path width

150 yards (137 m)

Deaths

0

Injuries

0

County

Converse County

Touchdown point

42.568, -105.433

Lift-off point

42.550, -105.408

Record number

1807281620-01

10 damage points were recorded along this path by NWS CYS, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF3. The highest wind the damage implies is 155 mph.

• Large rolls of hay were pulled off of a stack and rolled 100 to 200 yards away.
• Home had most windows blown out. Only middle portion of roof structure remained. Limbs from trees were blown into the house and were sticking out of the drywall.
• Quanset hut metal tractor building totally destroyed with debris carried off.
• 7000 lb horse trailer was lofted and (at the time of the storm survey) the only thing found was one of the axels.

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

Thunderstorms produced large hail, damaging winds and a couple tornadoes over portions of Converse and Platte counties.

The second tornado formed as the first tornado was lifting to the west, touching down near the West Fork of La Bonte Creek and Esterbrook Road. The tornado quickly strengthened to EF1 intensity as it moved along La Bonte Creek passing near a ranch house off Esterbrook Road. Most of the damage was to trees that were snapped mid trunk in a 150 yard path. The tornado lifted as it moved east of La Bonte Creek. The NWS survey team lost track of the tornado as it moved southeast into open country, so it is possible that track extended farther than the survey results indicated. The survey team also continued to investigate reports of damage at Esterbrook Campground to the southeast, to see if this damage was associated with the same tornado. Start and end times and locations and times of the tornado were estimated from eyewitness accounts and radar data.

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

31 minutes of warning. NWS CYS issued a tornado warning for this county at 21:49 UTC, 31 minutes before the tornado touched down, in force until 22:30 UTC.

The county was under a tornado watch, issued at 20:40 UTC and running to 04:00 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 Enhanced Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 20:05 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.

Douglas/Converse County Airport (DGW), 27 km from the path, in the two hours either side.

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

The Cheyenne radar (KCYS), 165 km away, was scanning. The volume nearest the touchdown began at 22:21 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

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.