Unrated tornado, Chugwater to Mers Hill, Wyoming, September 10, 2019

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 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. Unratedthis tornado

   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

Unrated

Date

September 10, 2019

Touchdown

4:58 PM MDT (22:58 UTC)

Lifted

5:05 PM MDT (23:05 UTC)

On the ground

7 minutes

Path length

8.5 miles (13.7 km)

Path width

30 yards (27 m)

Deaths

0

Injuries

0

Counties

Platte and Goshen counties

Touchdown point

41.760, -104.720

Lift-off point

41.790, -104.560

Record number

1909101658-01

Severe thunderstorms moved across the southeastern Wyoming High Plains producing large hail over softball size and numerous tornadoes in Platte and Goshen Counties. The highest rating tornado was an EF-2 north of Fort Laramie that was on the ground for close to thirty minutes. Couple residential homes were damaged by the tornado in addition to several livestock and wildlife animals killed by flying debris. The supercell that produced this tornado also produced an earlier tornado in Platte County and passed into Goshen before producing the EF-2 tornado. Later, another supercell tornado produced a shortlived tornado east of Chugwater and dissipated shortly after passing into Goshen County.

Platte County official observed the tornado over the open plains east of the town of Chugwater and as it lifted east of the shared county line with Goshen. No discernible damage was reported with the rope-shaped tornado to rate any higher than unknown. Given the limited access and no visible damage, path length and width should be considered as an estimated value.

Official from Yoder observed the tornado as it moved in from Platte County over the open high plains. No visible damage was reported with the tornado to discern any effective rating besides unknown. Path width and length should be considered as a best estimate given no official survey was performed in addition to remote location.

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

0 minutes of warning. NWS CYS issued a tornado warning for this county at 22:58 UTC, 0 minutes before the tornado touched down, in force until 23:12 UTC.

The county was under a tornado watch, issued at 19:54 UTC and running to 00:31 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, with a 0.02 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 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.

The Cheyenne radar (KCYS), 71 km away, was scanning. The volume nearest the touchdown began at 22:59 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 2019 tornado in WyomingEvery tornado in Wyoming since 1950Warnings in force in Wyoming nowThe forecast where you are

7 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.