Tornadoes · United States · Colorado · 2021

EF0 tornado, Sterling to Powell, Colorado, May 23, 2021

From Sterling to Powell, this EF0 tornado ran 0.0 miles across Logan County on May 23, 2021, touching down at 4:19 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
May 23, 2021
Touchdown
4:19 PM MDT (22:19 UTC)
Lifted
4:20 PM MDT (22:20 UTC)
On the ground
1 minutes
Path length
0.0 miles (0.0 km)
Path width
25 yards (23 m)
Deaths
0
Injuries
0
County
Logan County
Touchdown point
40.680, -102.910
Lift-off point
40.680, -102.910
Record number
2105231619-01

What the Weather Service recorded

Severe thunderstorms developed across Lincoln, Logan and Washington counties. The storms produced damaging thunderstorms wind gusts to 70 mph, hail up to 3 inches in diameter, and 7 brief tornadoes. Two the tornadoes in Logan County were rated EF1; they knocked down several power poles along State Highway 61 east of Sterling and near Proctor.

A tornado touched down and knocked power poles down along State Highway 61.

A tornado touched down briefly in open country.

A tornado touched down and knocked down powers pole near Proctor.

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

The warnings

9 minutes of warning. NWS BOU issued a tornado warning for this county at 22:10 UTC, 9 minutes before the tornado touched down, in force until 22:30 UTC.

The county was under a tornado watch, issued at 18:08 UTC and running to 01:35 UTC.

Issued (UTC)ExpiredProductOffice
18:08 UTC01:35 UTCTornado WatchBOU
21:11 UTC21:45 UTCTornado WarningBOU
21:42 UTC22:15 UTCTornado WarningBOU
22:10 UTC22:30 UTCTornado WarningBOU
22:27 UTC22:50 UTCTornado WarningBOU
23:12 UTC00:56 UTCFlood AdvisoryBOU
23:13 UTC23:45 UTCSevere Thunderstorm WarningBOU

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 Enhanced Risk, with a 0.10 chance of a tornado within 25 miles. The outlook in force was issued at 19:53 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.

Denver, CO (KDNR), 12:00Z

10.3 hours before the tornado, 94 km from the path. May 23, 2021.

Skew-T log-pSkew-T log-p diagram, Denver, CO at 12:00Z on 2021-05-23Temperature 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 -87064, lifted condensation level 1106 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, Denver, CO at 12:00Z on 2021-05-23The 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 73 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
-87064 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
1106 m above ground
0-6 km bulk shear
59 kt
0-1 km bulk shear
13 kt
0-1 km storm-relative helicity
73 m²/s²
0-3 km storm-relative helicity
177 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
5.0 K/km

Open this sounding in Storm Lab

Denver, CO (KDNR), 00:00Z

1.7 hours after it, 94 km from the path. May 24, 2021.

Skew-T log-pSkew-T log-p diagram, Denver, CO at 00:00Z on 2021-05-24Temperature 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 -78658, lifted condensation level 3282 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, Denver, CO at 00:00Z on 2021-05-24The 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 34 square meters per square second, 0 to 6 km bulk shear 60 knots.1939587897117Sfc1 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
-78658 J/kg
Surface CAPE
17 J/kg
Mixed-layer LCL
3282 m above ground
0-6 km bulk shear
60 kt
0-1 km bulk shear
8 kt
0-1 km storm-relative helicity
34 m²/s²
0-3 km storm-relative helicity
132 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
9.5 K/km

Open this sounding in Storm Lab

The surface observations

Sterling (STK), 31 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
20:35 UTC71.660.8160° 21 kt291011.5
20:55 UTC71.659150° 17 kt271010.8
21:15 UTC69.860.8160° 17 kt241010.5
21:35 UTC69.860.8160° 13 kt221010.5-RA
21:55 UTC66.262.6180° 24 kt301011.2+TSRA
22:15 UTC55.455.4160° 11 kt211010.8+TSRA
22:35 UTC53.653.6160° 16 kt251010.2TSRA
22:55 UTC55.453.6170° 14 kt1009.8-VCTSRA
23:15 UTC53.653.6160° 14 kt251011.5-TSRA
23:35 UTC51.851.80° 0 kt1011.5
23:55 UTC53.653.6320° 7 kt1011.5
00:15 UTC53.651.810° 18 kt271012.9

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

The radar

The Cheyenne radar (KCYS), 168 km away, was scanning. The volume nearest the touchdown began at 22:20 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
21:58 UTCHAIL 13 E AtwoodLogan, CO
22:00 UTCTORNADO4 Ese SterlingLogan, COPOWER POLES DOWN ON HIGHWAY 61. LIKELY TORNADO DAMAGE. EXACT LOCATION AND TIME APPROXIMATE.
22:00 UTCTORNADO4 Ese SterlingLogan, COPOWER POLES DOWN ON HIGHWAY 61. LIKELY TORNADO DAMAGE. EXACT LOCATION AND TIME APPROXIMATE.
22:11 UTCHAIL 0.75IliffLogan, COREPORT FROM MPING: DIME (0.75 IN.).
22:11 UTCHAIL 1IliffLogan, COREPORT FROM MPING: QUARTER (1.00 IN.).
22:15 UTCTSTM WND DMGPadroniLogan, COPOWER POLES AND SMALL TREE BRANCHES BLOWN DOWN. TIME ESTIMATED.
22:20 UTCTORNADO4 W FlemingLogan, COLANDSPOUT LIKELY ON BOUNDARY SOUTH OF MAIN MESOCYCLONE.
22:30 UTCHAIL 1.5IliffLogan, CO
22:30 UTCTORNADO1 W ProctorLogan, COEMERGENCY MANAGER REPORTED POWER POLES DOWN NEAR PROCTOR. LIKELY TORNADO DAMAGE. TIME ESTIMATED.
22:35 UTCHAIL 35 Nnw ProctorLogan, COREPORTED VIA FACEBOOK.
22:40 UTCTSTM WND GST 612 E SterlingLogan, COMESONET STATION I-76.

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

This ground now

The live radar over the trackEvery 2021 tornado in ColoradoEvery tornado in Colorado since 1950Warnings in force in Colorado nowThe forecast where you are

The other tornadoes of May 23, 2021

11 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
May 232:00 PM MDTEF0Lincoln, CO0.025
May 232:24 PM MDTEF0Washington, CO0.025
May 232:52 PM MDTEF0Washington, CO0.725
May 233:14 PM MDTEF0Washington, CO0.025
May 233:49 PM MDTEF1Logan, CO0.150
May 233:50 PM MDTUnratedPerkins, SD2.110
May 233:55 PM MDTEF1Custer, SD6.620
May 233:58 PM MDTUnratedPerkins, SD4.310
May 234:04 PM MDTEF1Custer, SD5.910
May 234:29 PM MDTEF1Logan, CO0.150
May 234:45 PM MDTEF0Lincoln, CO0.525

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.