Tornadoes · United States · Utah · 2021

Unrated tornado, Marriott, Utah, July 28, 2021

This Unrated tornado ran 0.2 miles across Weber County on July 28, 2021, touching down at 5:30 PM MDT and reaching 10 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 28, 2021
Touchdown
5:30 PM MDT (23:30 UTC)
Lifted
5:31 PM MDT (23:31 UTC)
On the ground
1 minutes
Path length
0.2 miles (0.3 km)
Path width
10 yards (9 m)
Deaths
0
Injuries
0
County
Weber County
Touchdown point
41.239, -111.982
Lift-off point
41.241, -111.979
Record number
2107281730-01

What the Weather Service recorded

An active monsoon surge brought several back-to-back days of thunderstorms producing heavy rain, damaging wind gusts, and hail across the state.

LANDSPOUT. A weak, but well-formed, landspout tornado was observed in multiple videos shared via social media.

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.

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 General Thunderstorms Risk. The outlook in force was issued at 20:00 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.

Salt Lake City I, UT (KSLC), 12:00Z

11.5 hours before the tornado, 52 km from the path. July 28, 2021.

Skew-T log-pSkew-T log-p diagram, Salt Lake City I, UT at 12:00Z on 2021-07-28Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 104 joules per kilogram, CIN -191, lifted condensation level 2082 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 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, Salt Lake City I, UT at 12:00Z on 2021-07-28The 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 67 square meters per square second, 0 to 6 km bulk shear 12 knots.1939Sfc1 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
104 J/kg
Mixed-layer CIN
-191 J/kg
Surface CAPE
101 J/kg
Mixed-layer LCL
2082 m above ground
0-6 km bulk shear
12 kt
0-1 km bulk shear
9 kt
0-1 km storm-relative helicity
67 m²/s²
0-3 km storm-relative helicity
48 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
6.9 K/km

Open this sounding in Storm Lab

Salt Lake City I, UT (KSLC), 00:00Z

0.5 hours after it, 52 km from the path. July 29, 2021.

Skew-T log-pSkew-T log-p diagram, Salt Lake City I, UT at 00:00Z on 2021-07-29Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 242 joules per kilogram, CIN -88, lifted condensation level 2422 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 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, Salt Lake City I, UT at 00:00Z on 2021-07-29The 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 16 square meters per square second, 0 to 6 km bulk shear 15 knots.1939Sfc1 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
242 J/kg
Mixed-layer CIN
-88 J/kg
Surface CAPE
743 J/kg
Mixed-layer LCL
2422 m above ground
0-6 km bulk shear
15 kt
0-1 km bulk shear
11 kt
0-1 km storm-relative helicity
16 m²/s²
0-3 km storm-relative helicity
39 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
8.5 K/km

Open this sounding in Storm Lab

The surface observations

Ogden-Hinckley Municipal (OGD), 6 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
21:30 UTC250° 7 kt1020.3
21:35 UTC260° 5 kt1020.3
21:40 UTC270° 5 kt1020
21:45 UTC 8 kt1020
21:50 UTC290° 5 kt1020
21:53 UTC9553270° 5 kt1020
21:55 UTC250° 8 kt1020
22:00 UTC110° 2 kt1020
22:05 UTC50° 2 kt1020
22:10 UTC 1019.6
22:15 UTC300° 5 kt1019.6
22:20 UTC290° 8 kt1019.6
22:25 UTC270° 5 kt1019.6
22:30 UTC 1019.3
22:35 UTC190° 5 kt1019.3
22:40 UTC200° 7 kt1019.3
22:45 UTC190° 7 kt1019.3
22:50 UTC150° 10 kt151019.3
22:53 UTC9654150° 11 kt171019.3
22:55 UTC130° 13 kt1019.3
23:00 UTC 11 kt1019
23:05 UTC150° 10 kt151019
23:10 UTC140° 7 kt1019
23:15 UTC160° 7 kt1019
23:20 UTC170° 5 kt1019
23:25 UTC 9 kt1019
23:30 UTC 10 kt1019
23:35 UTC170° 8 kt1019
23:40 UTC0° 0 kt1019
23:45 UTC0° 0 kt1019
23:50 UTC130° 7 kt1019
23:53 UTC9554 5 kt1019
23:55 UTC60° 7 kt1019
00:00 UTC 18 kt221019
00:05 UTC 20 kt1019
00:10 UTC 19 kt271019
00:15 UTC 20 kt1019
00:20 UTC 22 kt1019.3
00:25 UTC 20 kt1019.3
00:30 UTC 22 kt271019.3
00:35 UTC 22 kt271019.3
00:40 UTC 1019.3
00:45 UTC 18 kt1019.3
00:50 UTC 16 kt1019.3
00:53 UTC875770° 17 kt1019.3
00:55 UTC70° 15 kt1019.3HZ
01:00 UTC60° 14 kt1019.3
01:05 UTC70° 15 kt1019.3
01:10 UTC60° 15 kt1019.3
01:15 UTC60° 16 kt1019.3
01:20 UTC70° 16 kt1019.3
01:25 UTC60° 17 kt1019.3

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

The radar

The Salt Lake City radar (KMTX), 39 km away, was scanning. The volume nearest the touchdown began at 23:27 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
22:14 UTCTSTM WND GST 60PenroseBox Elder, UTSOCIAL MEDIA VIDEO SHOWS STRONG WINDS AND SMALL HAIL WITH HEAVY RAIN, DAMAGED GARAGE DOOR, TRASH CANS BLOWN AROUND IN WIND.
23:30 UTCTORNADO1 Nw OgdenWeber, UTWEAK BUT WELL FORMED LANDSPOUT OBSERVED IN MULTIPLE VIDEOS SHARED TO SOCIAL MEDIA.

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 UtahEvery tornado in Utah since 1950Warnings in force in Utah nowThe forecast where you are

The other tornadoes of July 28, 2021

10 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
July 288:40 PM CDTEF1Lincoln, WI2.7300
July 289:18 PM CDTEF0Marathon, WI0.2100
July 289:48 PM CDTEF1Saint Croix, WI5.7100$175,000
July 2811:06 PM CDTEF0Waushara, WI0.533
July 2812:10 AM CDTEF1Columbia, WI2.3100$500,000
July 2812:41 AM CDTEF0Columbia, WI0.450
July 2812:41 AM CDTEF0Dane, WI4.850
July 2812:41 AM CDTEF1Dane, WI2.8250
July 2812:47 AM CDTEF1Dane, WI2.4125
July 2812:48 AM CDTEF0Dane, WI3.575$10,000

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.