Tornadoes · United States · Wyoming · 1991

F1 tornado, Park County, Wyoming, May 18, 1991

Name: F1 tornado, Park County, Wyoming, May 18, 1991
Start: 1991-05-19T01:07:00.000Z
Location: Park County, Wyoming

This F1 tornado ran 0.2 miles across Park County on May 18, 1991, touching down at 7:07 PM MDT and reaching 60 yards wide. It killed nobody.

The rating scale

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

F040 to 72 mph
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
F173 to 112 mphthis tornado
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
F2113 to 157 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.
F3158 to 206 mph
Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.
F4207 to 260 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
F5261 to 318 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.
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: F1
Date: May 18, 1991
Touchdown: 7:07 PM MDT (01:07 UTC)
Path length: 0.2 miles (0.3 km)
Path width: 60 yards (55 m)
Deaths: 0
Injuries: 0
County: Park County
Touchdown point: 44.750, -108.920
Record number: 626

The surface observations

Cody Municipal (Awos) (COD), 27 km from the path, in the two hours either side.

Time (UTC)	Temp (°F)	Dew point (°F)	Wind	Gust (kt)	Pressure (mb)	Weather
00:00 UTC

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

This ground now

The live radar over the track Every 1991 tornado in Wyoming Every tornado in Wyoming since 1950 Warnings in force in Wyoming now The forecast where you are

The other tornadoes of May 18, 1991

5 more were confirmed in the United States that day.

Date	Time	Rating	Where	Path (mi)	Width (yd)	Damage
May 18	2:16 PM CDT	F1	Mississippi, MO	0.8	50	$50,000 to $500,000
May 18	3:30 PM CDT	F0	Adams, IL	0.7	33
May 18	4:36 PM MDT	F2	Minidoka, ID	0.2	50	$50,000 to $500,000
May 18	6:45 PM EDT	F0	Pasco, FL	0.5	50	$5,000 to $50,000
May 18	5:25 PM MDT	F0	Blaine, ID	0.2	50

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.