Tornadoes · United States · North Dakota · 2020

EF0 tornado, Osnabrock to Milton, North Dakota, August 9, 2020

From Osnabrock to Milton, this EF0 tornado ran 0.3 miles across Cavalier County on August 9, 2020, touching down at 11:58 AM CDT and reaching 40 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
August 9, 2020
Touchdown
11:58 AM CDT (16:58 UTC)
Lifted
11:59 AM CDT (16:59 UTC)
On the ground
1 minutes
Path length
0.3 miles (0.5 km)
Path width
40 yards (37 m)
Deaths
0
Injuries
0
Crop damage
$50,000
County
Cavalier County
Touchdown point
48.670, -97.975
Lift-off point
48.670, -97.968
Record number
2008091058-01

What the Weather Service recorded

A cold front moved across eastern North Dakota and the northwest quarter of Minnesota on Sunday, August 9th. Abundant moisture remained in place, with dew points in the upper 60s to lower 70s. Thunderstorms formed across the area, producing large hail, damaging wind gusts, and tornadoes.

A brief touchdown was noted and photographed in an open field, before the tornado became engulfed in downburst winds and heavy rain. The tornado likely tracked for a half mile or less and ended by 1059 am CST. Peak winds estimated to 80 mph.

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

The warnings

16 minutes of warning. NWS FGF issued a tornado warning for this county at 16:42 UTC, 16 minutes before the tornado touched down, in force until 17:18 UTC.

Issued (UTC)ExpiredProductOffice
16:28 UTC17:30 UTCSevere Thunderstorm WarningFGF
16:42 UTC17:18 UTCTornado WarningFGF
17:21 UTC17:53 UTCSevere Thunderstorm 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 Slight Risk, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 16:16 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.

Bismarck Municip, ND (KBIS), 12:00Z

5.0 hours before the tornado, 294 km from the path. August 9, 2020.

Skew-T log-pSkew-T log-p diagram, Bismarck Municip, ND at 12:00Z on 2020-08-09Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 2140 joules per kilogram, CIN -174, lifted condensation level 843 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, Bismarck Municip, ND at 12:00Z on 2020-08-09The 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 95 square meters per square second, 0 to 6 km bulk shear 27 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
2140 J/kg
Mixed-layer CIN
-174 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
843 m above ground
0-6 km bulk shear
27 kt
0-1 km bulk shear
18 kt
0-1 km storm-relative helicity
95 m²/s²
0-3 km storm-relative helicity
127 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.5
0-3 km lapse rate
3.4 K/km

Open this sounding in Storm Lab

Bismarck Municip, ND (KBIS), 00:00Z

7.0 hours after it, 294 km from the path. August 10, 2020.

Skew-T log-pSkew-T log-p diagram, Bismarck Municip, ND at 00:00Z on 2020-08-10Temperature 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 -88271, lifted condensation level 2738 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 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, Bismarck Municip, ND at 00:00Z on 2020-08-10The 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 -79 square meters per square second, 0 to 6 km bulk shear 46 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
-88271 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
2738 m above ground
0-6 km bulk shear
46 kt
0-1 km bulk shear
11 kt
0-1 km storm-relative helicity
-79 m²/s²
0-3 km storm-relative helicity
-104 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
7.1 K/km

Open this sounding in Storm Lab

The radar

The Fargo/Grand Forks radar (KMVX), 136 km away, was scanning. The volume nearest the touchdown began at 17:00 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
15:40 UTCHAIL 0.755 Ne WhitmanWalsh, NDPEA TO DIME SIZED HAIL.
15:40 UTCHAIL 0.755 Ne WhitmanWalsh, NDPEA TO DIME SIZED HAIL.
15:45 UTCHAIL 15 W FordvilleWalsh, ND
15:45 UTCHAIL 15 W FordvilleWalsh, ND
15:45 UTCHAIL 18 W FordvilleWalsh, ND
15:45 UTCHAIL 18 W FordvilleWalsh, ND
16:43 UTCHAIL 15 Wnw OsnabrockCavalier, NDNICKEL TO QUARTER SIZED HAIL AND VERY HEAVY RAIN.
16:43 UTCHAIL 15 Wnw OsnabrockCavalier, NDNICKEL TO QUARTER SIZED HAIL AND VERY HEAVY RAIN.
16:50 UTCTSTM WND DMGMiltonCavalier, NDA FEW LARGE TREE BRANCHES BROKEN DOWN AROUND TOWN.
17:05 UTCHAIL 1.251 S MountainPembina, NDA FEW HAIL LARGER THAN QUARTERS. MOST WERE DIME TO NICKEL SIZED.
17:05 UTCHAIL 1.251 S MountainPembina, NDA FEW HAIL LARGER THAN QUARTERS. MOST WERE DIME TO NICKEL SIZED.

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 North DakotaEvery tornado in North Dakota since 1950Warnings in force in North Dakota nowThe forecast where you are

The other tornadoes of August 9, 2020

12 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
August 92:02 PM CDTEF1LaMoure, ND0.9100$225,000
August 92:13 PM CDTUnratedLaMoure, ND2.2100
August 92:13 PM CDTEF1Pennington, MN22.0200
August 92:17 PM CDTEF1Barnes, ND2.9150
August 92:19 PM CDTUnratedLaMoure, ND0.350
August 92:40 PM CDTEF0Traill, ND2.040
August 93:20 PM CDTEF1Beltrami, MN0.3100
August 96:15 PM EDTEF0Manatee, FL0.2100$20,000
August 97:44 PM CDTEF1Vilas, WI6.2400
August 98:28 PM CDTEF1Vilas, WI5.9250
August 99:12 PM CDTEF1Iron, WI to MI4.6250$70,000
August 99:56 PM CDTEF1Iron, MI3.8250$100,000

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.