Tornadoes · United States · Minnesota · 2020

EF1 tornado, Cormorant, Minnesota, July 11, 2020

This EF1 tornado ran 1.5 miles across Becker County on July 11, 2020, touching down at 1:06 PM CDT and reaching 30 yards wide. It killed nobody, and did $20,000 of property damage.

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 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.

The record

Rating
EF1
Date
July 11, 2020
Touchdown
1:06 PM CDT (18:06 UTC)
Lifted
1:12 PM CDT (18:12 UTC)
On the ground
6 minutes
Path length
1.5 miles (2.4 km)
Path width
30 yards (27 m)
Deaths
0
Injuries
0
Property damage
$20,000
Crop damage
$1,000
County
Becker County
Touchdown point
46.740, -96.170
Lift-off point
46.702, -96.168
Record number
2007111206-01

What the Weather Service recorded

During the early afternoon of July 11th, isolated thunderstorms formed between Langdon (ND), Hillsboro (ND), and Alexandria (MN). One of these storms produced a tornado over southwest Becker County (MN), southwest of Detroit Lakes, Minnesota.

A rope tornado meandered southward for about 1.5 miles, tracking through a wind farm area with a mix of pastureland and gravel quarries. At an abandoned farmstead, it tore more of the roof off a barn and roofing panels off other farm buildings. Peak winds were estimated at 95 mph.

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. One was issued for the county at another hour that day.

Issued (UTC)ExpiredProductOffice
18:07 UTC18:26 UTCTornado WarningFGF

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 16:51 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.

Aberdeen, SD (KABR), 12:00Z

6.1 hours before the tornado, 266 km from the path. July 11, 2020.

Skew-T log-pSkew-T log-p diagram, Aberdeen, SD at 12:00Z on 2020-07-11Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 550 joules per kilogram, CIN -117, lifted condensation level 1119 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, Aberdeen, SD at 12:00Z on 2020-07-11The 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 5 square meters per square second, 0 to 6 km bulk shear 28 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
550 J/kg
Mixed-layer CIN
-117 J/kg
Surface CAPE
431 J/kg
Mixed-layer LCL
1119 m above ground
0-6 km bulk shear
28 kt
0-1 km bulk shear
15 kt
0-1 km storm-relative helicity
5 m²/s²
0-3 km storm-relative helicity
49 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.2
0-3 km lapse rate
5.6 K/km

Open this sounding in Storm Lab

Aberdeen, SD (KABR), 00:00Z

5.9 hours after it, 266 km from the path. July 12, 2020.

Skew-T log-pSkew-T log-p diagram, Aberdeen, SD at 00:00Z on 2020-07-12Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 4 joules per kilogram, CIN -7, lifted condensation level 1636 meters above ground. Wind barbs in knots down the right edge.LCLEL10008507005003002001001 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, Aberdeen, SD at 00:00Z on 2020-07-12The 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 -1 square meters per square second, 0 to 6 km bulk shear 28 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
4 J/kg
Mixed-layer CIN
-7 J/kg
Surface CAPE
27 J/kg
Mixed-layer LCL
1636 m above ground
0-6 km bulk shear
28 kt
0-1 km bulk shear
9 kt
0-1 km storm-relative helicity
-1 m²/s²
0-3 km storm-relative helicity
12 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
5.9 K/km

Open this sounding in Storm Lab

The surface observations

Detroit Lakes (DTL), 24 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
16:15 UTC73.460.80° 0 kt1014.9
16:35 UTC73.462.60° 0 kt1014.9
16:55 UTC73.460.80° 0 kt1014.9
17:15 UTC73.460.80° 0 kt1014.9
17:35 UTC73.460.80° 0 kt1014.9
17:55 UTC73.460.80° 0 kt1014.9
18:15 UTC75.259360° 3 kt1015.2
18:35 UTC75.2590° 0 kt1014.9
18:55 UTC75.259190° 4 kt1014.9
19:15 UTC73.460.8200° 9 kt1015.2VCTS
19:35 UTC69.859220° 10 kt161014.9
19:55 UTC73.459200° 3 kt1014.6

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

The radar

The Fargo/Grand Forks radar (KMVX), 125 km away, was scanning. The volume nearest the touchdown began at 18:02 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
18:06 UTCTORNADO 13 E RollagBecker, MNA ROPE TORNADO MEANDERED SOUTHWARD FOR ROUGHLY 1.5 MILES TO AROUND 5 WSW OF CORMORANT BY 112 PM CDT. THIS TORNADO TRACKED THROUGH A WIND FARM AREA WITH A MIX OF PASTURELAND AND GRAVEL QUARIES. AT AN ABANDONED FARMSTEAD,
18:06 UTCTORNADO2 Wnw CormorantBecker, MNMULTIPLE FUNNEL CLOUDS WITH OCCASIONAL BRIEF TOUCHDOWNS.
18:25 UTCFUNNEL CLOUD3 E Pelican RapidsOtter Tail, MNFUNNEL VIEWED NEAR THE CLOUD BASE, LOOKING TOWARDS LAKE LIDA FROM PELICAN RAPIDS.
18:43 UTCFUNNEL CLOUD3 E Fergus FallsOtter Tail, MNA FUNNEL CLOUD TRACKED SOUTHEASTWARD OFF THE EAST EDGE OF FERGUS FALLS FOR A FEW MINUTES. REPORTS STATE IT CAME NEARLY HALFWAY DOWN TO THE GROUND AT ONE POINT. PHOTOS AND REPORTS ALSO POSTED VIA BROADCAST AND SOCIAL MEDI
18:45 UTCFUNNEL CLOUD4 Ese Fergus FallsOtter Tail, MNFUNNEL CLOUD MADE IT HALFWAY TO THE GROUND BEFORE GOING BACK UP.
19:31 UTCFUNNEL CLOUD5 Ene Fergus FallsOtter Tail, MNPUBLIC AND STORM SPOTTER REPORTS RECEIVED OF A PERISTENT FUNNEL CLOUD RANGING FROM ONE THIRD TO ONE HALF THE WAY DOWN TO THE GROUND OVER A FEW MINUTE TIMEFRAME.
19:40 UTCFUNNEL CLOUD5 Ene Fergus FallsOtter Tail, MNFUNNEL HALF WAY TO THE GROUND.

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

This ground now

The live radar over the trackEvery 2020 tornado in MinnesotaEvery tornado in Minnesota since 1950Warnings in force in Minnesota nowThe forecast where you are

The other tornadoes of July 11, 2020

4 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
July 113:31 PM EDTEF0Cumberland, ME4.9100$4,000
July 113:09 PM CDTEF0Nicollet, MN2.4125$25,000
July 117:59 PM CDTEF0Randall, TX0.145
July 1112:04 AM CDTEF0Cleveland, OK0.210$20,000

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.