Tornadoes · United States · Colorado · 2021

Unrated tornado, Lamar Arpt, Colorado, July 6, 2021

This Unrated tornado ran 0.2 miles across Prowers County on July 6, 2021, touching down at 2:14 PM MDT and reaching 20 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 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.

The record

Rating
Unrated
Date
July 6, 2021
Touchdown
2:14 PM MDT (20:14 UTC)
Lifted
2:17 PM MDT (20:17 UTC)
On the ground
3 minutes
Path length
0.2 miles (0.3 km)
Path width
20 yards (18 m)
Deaths
0
Injuries
0
County
Prowers County
Touchdown point
37.880, -102.690
Lift-off point
37.880, -102.686
Record number
2107061414-01

What the Weather Service recorded

Another active day with showers and thunderstorms occurring across southern Colorado, especially along the eastern mountains and into the I-25 corridor. While there was an isolated severe threat, the main risk on this day was heavy rainfall with flash flooding.

Two brief landspout tornadoes occurred simultaneously.

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.

Issued (UTC)ExpiredProductOffice
19:43 UTC20:15 UTCSevere Thunderstorm WarningPUB
20:11 UTC20:45 UTCSevere Thunderstorm WarningPUB
20:32 UTC20:46 UTCSevere Thunderstorm WarningPUB
20:42 UTC21:15 UTCSevere Thunderstorm WarningPUB

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 Marginal Risk. The outlook in force was issued at 19:59 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

8.2 hours before the tornado, 226 km from the path. July 6, 2021.

Skew-T log-pSkew-T log-p diagram, Denver, CO at 12:00Z on 2021-07-06Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 1 joules per kilogram, CIN -341, lifted condensation level 1241 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°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 2021-07-06The 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 -41 square meters per square second, 0 to 6 km bulk shear 15 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
1 J/kg
Mixed-layer CIN
-341 J/kg
Surface CAPE
30 J/kg
Mixed-layer LCL
1241 m above ground
0-6 km bulk shear
15 kt
0-1 km bulk shear
8 kt
0-1 km storm-relative helicity
-41 m²/s²
0-3 km storm-relative helicity
11 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

3.8 hours after it, 226 km from the path. July 7, 2021.

Skew-T log-pSkew-T log-p diagram, Denver, CO at 00:00Z on 2021-07-07Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 117 joules per kilogram, CIN -37, lifted condensation level 2096 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°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 2021-07-07The 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 -30 square meters per square second, 0 to 6 km bulk shear 14 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
117 J/kg
Mixed-layer CIN
-37 J/kg
Surface CAPE
457 J/kg
Mixed-layer LCL
2096 m above ground
0-6 km bulk shear
14 kt
0-1 km bulk shear
6 kt
0-1 km storm-relative helicity
-30 m²/s²
0-3 km storm-relative helicity
65 m²/s²
Significant tornado parameter
0.0
Supercell composite
-0.2
0-3 km lapse rate
8.6 K/km

Open this sounding in Storm Lab

The surface observations

Lamar (LAA), 21 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
18:15 UTC60° 4 kt1017.3
18:20 UTC30° 5 kt1017.3
18:25 UTC110° 7 kt1017.3
18:35 UTC300° 2 kt1016.9
18:40 UTC120° 2 kt1016.9
18:45 UTC60° 5 kt1016.9
18:50 UTC120° 8 kt1016.9
18:53 UTC8864100° 9 kt1016.9
19:05 UTC80° 9 kt1016.6
19:10 UTC80° 5 kt1016.6
19:15 UTC110° 10 kt151016.6
19:20 UTC70° 9 kt141016.6
19:25 UTC60° 11 kt1016.6
19:35 UTC876160° 12 kt1016.6VCTS
19:35 UTC60° 11 kt1016.6
19:40 UTC50° 11 kt1016.6
19:45 UTC40° 9 kt141016.9
19:45 UTC866140° 9 kt1016.9TS
19:50 UTC 16 kt221017.3
19:53 UTC8363360° 15 kt241017.3TS
20:05 UTC 15 kt1017.3
20:06 UTC7764330° 13 kt241017.3TS
20:10 UTC 14 kt1017.6
20:15 UTC 11 kt1017.6
20:20 UTC 10 kt1017.6
20:25 UTC330° 5 kt1017.3
20:30 UTC360° 7 kt1017.3
20:35 UTC350° 8 kt1017.3-RA
20:37 UTC7564350° 6 kt1017.3VCTS -RA
20:50 UTC130° 4 kt1017.3-RA
20:53 UTC75670° 0 kt1016.9-RA
20:55 UTC0° 0 kt1016.9-RA
21:00 UTC160° 2 kt1017.3-RA
21:05 UTC180° 5 kt1017.6-RA
21:10 UTC160° 9 kt1017.6-RA
21:15 UTC170° 8 kt1017.6
21:25 UTC 13 kt1017.6
21:30 UTC170° 11 kt171017.6
21:35 UTC170° 11 kt1017.6
21:40 UTC170° 9 kt1017.3
21:45 UTC170° 10 kt1017.3
21:50 UTC170° 10 kt1017.3
21:53 UTC7466170° 11 kt1017.3
21:55 UTC160° 10 kt1017.3
22:00 UTC170° 9 kt1017.3
22:05 UTC190° 11 kt1017.6
22:10 UTC210° 11 kt1017.3

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

The radar

The Pueblo radar (KPUX), 146 km away, was scanning. The volume nearest the touchdown began at 20:14 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
20:14 UTCTORNADO15 Ssw LamarProwers, CO2 LANDSPOUT TORNADOES OCCURRING SIMULTANEOUSLY. TIME BASED ON RADART. PHOTOS OF LANDSPOUTS SEEN ON SOCIAL MEDIA.
20:22 UTCFUNNEL CLOUDLamarProwers, COSPOTTER ID (AD317) NOT SHOWING UP IN SEARCH. HAD SEEN WHAT APPEARS TO BE A FUNNEL CLOUD WITH NO VIEW OF THE BASE, FROM ABOUT 15 MILES SW OF LOCATION.

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 July 6, 2021

1 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
July 66:11 PM MDTUnratedBlaine, MT4.930

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.