Tornadoes · United States · Wyoming · 2018

EF2 tornado, Mayoworth, Wyoming, June 1, 2018

This EF2 tornado ran 1.0 miles across Johnson County on June 1, 2018, touching down at 12:16 PM MDT and reaching 300 yards wide. It killed nobody.

The rating scale

Tracks are drawn in the color of the rating. The Enhanced Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.

  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 mph

    Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

  3. EF2111 to 135 mphthis tornado

    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.

The record

Rating
EF2
Date
June 1, 2018
Touchdown
12:16 PM MDT (18:16 UTC)
Lifted
12:21 PM MDT (18:21 UTC)
On the ground
5 minutes
Path length
1.0 miles (1.7 km)
Path width
300 yards (274 m)
Deaths
0
Injuries
0
County
Johnson County
Touchdown point
44.029, -107.106
Lift-off point
44.042, -107.115
Record number
1806011216-01

What the Weather Service recorded

An upper level low and potent jet dynamics moved across Wyoming and brought severe weather to portions of central Wyoming. The strongest thunderstorms moved across eastern Washakie and western Johnson counties. Two tornadoes touched down and downed many trees along the Washakie / Johnson County border. The storms also produced large hail up to the size of ping pong balls. Another strong thunderstorm produced nickel size hail at Winchester.

An EF-2 tornado with maximum winds at 120 mph, touched down in the higher elevations of western Johnson county. This tornado touched down in a large forested area, downing or snapping nearly a thousand trees throughout its path.

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

The warnings

13 minutes of warning. NWS RIW issued a tornado warning for this county at 18:03 UTC, 13 minutes before the tornado touched down, in force until 18:30 UTC.

The county was under a severe thunderstorm watch, issued at 17:47 UTC and running to 22:03 UTC.

Issued (UTC)ExpiredProductOffice
17:10 UTC17:39 UTCSevere Thunderstorm WarningRIW
17:28 UTC18:15 UTCSevere Thunderstorm WarningRIW
17:47 UTC22:03 UTCSevere Thunderstorm WatchRIW
18:03 UTC18:30 UTCTornado WarningRIW

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 forecast that day

The Storm Prediction Center had this point in a Marginal 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 air that afternoon

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.

Riverton, WY (KRIW), 12:00Z

6.3 hours before the tornado, 149 km from the path. June 1, 2018.

Skew-T log-pSkew-T log-p diagram, Riverton, WY at 12:00Z on 2018-06-01Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 0 joules per kilogram, CIN -74503, lifted condensation level 2523 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 km2 km3 km6 km9 km12 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Riverton, WY at 12:00Z on 2018-06-01The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity -2 square meters per square second, 0 to 6 km bulk shear 59 knots.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
0 J/kg
Mixed-layer CIN
-74503 J/kg
Surface CAPE
9 J/kg
Mixed-layer LCL
2523 m above ground
0-6 km bulk shear
59 kt
0-1 km bulk shear
8 kt
0-1 km storm-relative helicity
-2 m²/s²
0-3 km storm-relative helicity
35 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
6.3 K/km

Open this sounding in Storm Lab

Riverton, WY (KRIW), 00:00Z

5.7 hours after it, 149 km from the path. June 2, 2018.

Skew-T log-pSkew-T log-p diagram, Riverton, WY at 00:00Z on 2018-06-02Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 0 joules per kilogram, CIN -90187, lifted condensation level 2905 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 km2 km3 km6 km9 km12 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Riverton, WY at 00:00Z on 2018-06-02The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity 19 square meters per square second, 0 to 6 km bulk shear 25 knots.193958Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
0 J/kg
Mixed-layer CIN
-90187 J/kg
Surface CAPE
93 J/kg
Mixed-layer LCL
2905 m above ground
0-6 km bulk shear
25 kt
0-1 km bulk shear
15 kt
0-1 km storm-relative helicity
19 m²/s²
0-3 km storm-relative helicity
50 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
9.0 K/km

Open this sounding in Storm Lab

The radar

The Riverton/Lander radar (KRIW), 154 km away, was scanning. The volume nearest the touchdown began at 18:14 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.

What was reported nearby

Local storm reports within 60 km of the path, in the three hours either side.

Time (UTC)ReportWhereCountyRemark
17:32 UTCHAIL 1.53 N Big TrailsWashakie, WYTHUNDERSTORM INITIALLY PRODUCED PING PONG BALL SIZED HAIL BEFORE PRODUCING LOTS OF HALF-INCH DIAMATER HAIL.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

This ground now

The live radar over the trackEvery 2018 tornado in WyomingEvery tornado in Wyoming since 1950Warnings in force in Wyoming nowThe forecast where you are

The other tornadoes of June 1, 2018

14 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
June 112:11 PM MDTEF2Washakie, WY1.0300$20,000
June 11:34 PM MDTEF0Campbell, WY1.025
June 11:41 PM MDTEF3Campbell, WY3.82002
June 11:55 PM MDTEF1Campbell, WY0.525$50,000
June 11:59 PM MDTEF1Campbell, WY4.650
June 14:26 PM MDTEF0Dunn, ND0.350
June 14:34 PM MDTEF2Dunn, ND3.5200$175,000
June 15:53 PM CDTEF0Morton, ND7.3100$5,000
June 15:55 PM CDTEF0McKenzie, ND0.350
June 16:25 PM CDTEF0Mercer, ND1.475
June 17:36 PM CDTEF0Walworth, SD0.110
June 18:43 PM CDTUnratedKent, TX0.030
June 19:14 PM CDTEF0Valley, NE0.040
June 19:59 PM CDTEF0Madison, NE0.150

What this means

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.

Sources

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.