EF1 tornado, Warren Bridge, Wyoming, September 4, 2016

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

September 4, 2016

Touchdown

1:06 PM MDT (19:06 UTC)

Lifted

1:12 PM MDT (19:12 UTC)

On the ground

6 minutes

Path length

2.4 miles (3.9 km)

Path width

300 yards (274 m)

Deaths

0

Injuries

0

Property damage

$1,000

County

Sublette County

Touchdown point

43.066, -110.256

Lift-off point

43.101, -110.253

Record number

1609041306-01

5 damage points were recorded along this path by NWS RIW, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 110 mph.

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

A thunderstorm rapidly developed near Merna, Wyoming, on the afternoon of Sunday, September 4. Southeast wind at the surface coupled with strong southwest flow aloft created a favorable environment in which the storm could rotate. The storm strengthened, began rotating, and moved north across several private ranches and spawned a funnel cloud. The funnel eventually touched down as a tornado and caused areas of considerable tree damage just below The Rim, between Merna and Hoback Ranches. Large, old growth aspen trees of 12 to 15 inches in diameter were snapped in half, and other trees were topped, twisted, and/or uprooted. Hail up to the size of ping pong balls also fell near The Rim during the height of the thunderstorm.

A tornado touched down in open country north of Merna, Wyoming, and caused tree damage along its approximately 2.4 mile path. At its widest, the tornado produced sporadic tree damage approximately 300 yards across. The trees fell on some fence lines, but otherwise caused no property damage.

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

No tornado warning for this county appears in the archive as in force at the moment the tornado touched down.

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 General Thunderstorms Risk. The outlook in force was issued at 16:16 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 Riverton/Lander radar (KRIW), 144 km away, was scanning. The volume nearest the touchdown began at 19:06 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 2016 tornado in WyomingEvery tornado in Wyoming since 1950Warnings in force in Wyoming nowThe forecast where you are

1 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.