Tornadoes · United States · Wyoming · 2010

EF0 tornado, Bill, Wyoming, June 20, 2010

This EF0 tornado ran 0.3 miles across Converse County on June 20, 2010, touching down at 5:20 PM MDT and reaching 25 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 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.

The record

Rating
EF0
Date
June 20, 2010
Touchdown
5:20 PM MDT (23:20 UTC)
Lifted
5:25 PM MDT (23:25 UTC)
On the ground
5 minutes
Path length
0.3 miles (0.4 km)
Path width
25 yards (23 m)
Deaths
0
Injuries
0
County
Converse County
Touchdown point
43.147, -105.545
Lift-off point
43.147, -105.545
Record number
1006201720-01

What the Weather Service recorded

Daytime heating in combination with increasing moisture provided an environment suitable for hail and tornado formation. The remaining stability capping the environment was eroded by mid afternoon.

Estimated path length and width due to no storm survey being conducted. No damage was reported.

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

The warnings

No tornado warning for this county appears in the archive as in force at the moment the tornado touched down. One was issued for the county at another hour that day.

The county was under a tornado watch, issued at 19:30 UTC and running to 01:38 UTC.

Issued (UTC)ExpiredProductOffice
19:30 UTC01:38 UTCTornado WatchCYS
23:49 UTC00:30 UTCTornado WarningCYS

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 Slight Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 19:58 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

11.3 hours before the tornado, 232 km from the path. June 20, 2010.

Skew-T log-pSkew-T log-p diagram, Riverton, WY at 12:00Z on 2010-06-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 201 joules per kilogram, CIN -195, lifted condensation level 1519 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 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 2010-06-20The 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 -5 square meters per square second, 0 to 6 km bulk shear 36 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
201 J/kg
Mixed-layer CIN
-195 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
1519 m above ground
0-6 km bulk shear
36 kt
0-1 km bulk shear
8 kt
0-1 km storm-relative helicity
-5 m²/s²
0-3 km storm-relative helicity
46 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
5.2 K/km

Open this sounding in Storm Lab

Riverton, WY (KRIW), 00:00Z

0.7 hours after it, 232 km from the path. June 21, 2010.

Skew-T log-pSkew-T log-p diagram, Riverton, WY at 00:00Z on 2010-06-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 257 joules per kilogram, CIN -16, lifted condensation level 2928 meters above ground. Wind barbs in knots down the right edge.LCLEL10008507005003002001001 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 2010-06-21The 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 58 square meters per square second, 0 to 6 km bulk shear 30 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
257 J/kg
Mixed-layer CIN
-16 J/kg
Surface CAPE
1500 J/kg
Mixed-layer LCL
2928 m above ground
0-6 km bulk shear
30 kt
0-1 km bulk shear
11 kt
0-1 km storm-relative helicity
58 m²/s²
0-3 km storm-relative helicity
135 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.1
0-3 km lapse rate
10.0 K/km

Open this sounding in Storm Lab

The radar

The Cheyenne radar (KCYS), 230 km away, was scanning. The volume nearest the touchdown began at 23:19 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
23:22 UTCTORNADO15 Wsw BillConverse, WY
23:45 UTCTORNADO16 W BillConverse, WYSPOTTER REPORTED TORNADO ON THE GROUND FOR 5 MINUTES 30 MILES NORTH/NORTHEAST OF GLENROCK.

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

This ground now

The live radar over the trackEvery 2010 tornado in WyomingEvery tornado in Wyoming since 1950Warnings in force in Wyoming nowThe forecast where you are

The other tornadoes of June 20, 2010

8 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
June 203:25 PM CDTEF0Scott, KS0.9100
June 203:43 PM CDTEF0Scott, KS0.5100
June 205:55 PM EDTEF0Putnam, FL3.410
June 204:24 PM MDTEF2Yellowstone, MT0.7120$30 million
June 204:26 PM MDTEF0Platte, WY7.2100
June 205:57 PM MDTEF0Pennington, SD0.120$2,000
June 207:20 PM CDTEF0Jewell, KS0.120
June 207:50 PM CDTEF2Nuckolls, NE1.51,300

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.