Tornadoes · United States · North Dakota · 2017

EF0 tornado, Tolna to Mapes, North Dakota, September 1, 2017

From Tolna to Mapes, this EF0 tornado ran 0.1 miles across Nelson County on September 1, 2017, touching down at 5:30 PM CDT and reaching 50 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
September 1, 2017
Touchdown
5:30 PM CDT (22:30 UTC)
Lifted
5:31 PM CDT (22:31 UTC)
On the ground
1 minutes
Path length
0.1 miles (0.1 km)
Path width
50 yards (46 m)
Deaths
0
Injuries
0
County
Nelson County
Touchdown point
47.920, -98.420
Lift-off point
47.920, -98.419
Record number
1709011630-01

What the Weather Service recorded

During the early evening of September 1st, a line of thunderstorms formed between Stump Lake, in Nelson County, and Pembina, in Cavalier County. However, one cell on the far southern end of the line quickly became the strongest storm, and it would hold together as the storm tracked to the south-southeast, through Griggs, Steele, and Cass counties, before weakening. This cell produced several weak tornadoes, funnel clouds, and large hail.

A brief tornado touchdown with water swirl was noted over the north end of Stump Lake. As the tornado lifted, the funnel continued to track to the east. Peak winds were estimated at 70 mph.

This tornado touched down just east of Stump Lake and tracked to the east. Photos showed a persistent rope tornado with intermittent dust swirls. Peak winds were estimated at 80 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
22:40 UTC23:15 UTCTornado WarningFGF
23:12 UTC23:45 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 Marginal 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.

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

10.5 hours before the tornado, 214 km from the path. September 1, 2017.

Skew-T log-pSkew-T log-p diagram, Bismarck Municip, ND at 12:00Z on 2017-09-01Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 143 joules per kilogram, CIN -272, lifted condensation level 1132 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 2017-09-01The 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 224 square meters per square second, 0 to 6 km bulk shear 22 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
143 J/kg
Mixed-layer CIN
-272 J/kg
Surface CAPE
708 J/kg
Mixed-layer LCL
1132 m above ground
0-6 km bulk shear
22 kt
0-1 km bulk shear
16 kt
0-1 km storm-relative helicity
224 m²/s²
0-3 km storm-relative helicity
281 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
5.1 K/km

Open this sounding in Storm Lab

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

1.5 hours after it, 214 km from the path. September 2, 2017.

Skew-T log-pSkew-T log-p diagram, Bismarck Municip, ND at 00:00Z on 2017-09-02Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 52 joules per kilogram, CIN -63, lifted condensation level 1869 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 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 2017-09-02The 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 -2 square meters per square second, 0 to 6 km bulk shear 41 knots.1939587897Sfc1 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
52 J/kg
Mixed-layer CIN
-63 J/kg
Surface CAPE
116 J/kg
Mixed-layer LCL
1869 m above ground
0-6 km bulk shear
41 kt
0-1 km bulk shear
3 kt
0-1 km storm-relative helicity
-2 m²/s²
0-3 km storm-relative helicity
25 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
8.0 K/km

Open this sounding in Storm Lab

The radar

The Fargo/Grand Forks radar (KMVX), 93 km away, was scanning. The volume nearest the touchdown began at 22:30 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
22:25 UTCHAIL 0.5Stump LakeNelson, NDHEAVY RAIN AND SMALL HAIL AT STUMP LAKE PARK.
22:30 UTCTORNADO 09 Ssw LakotaNelson, NDA BRIEF TOUCHDOWN WITH WATER SWIRL WAS NOTED OVER THE NORTH END OF STUMP LAKE. TOUCHDOWN WAS A MINUTE OR LESS WITH AN ESTIMATED TRACK LENGTH OF AROUND A QUARTER MILE. TIME NOTED BY PHOTO. FUNNEL CONTINUED TRACKING EAST.
22:30 UTCTORNADO7 Ssw LakotaNelson, NDA BRIEF TOUCHDOWN WITH DUST SWIRL WAS NOTED NORTHEAST OF STUMP LAKE.
22:38 UTCTORNADO 09 S LakotaNelson, NDTHIS TORNADO TOUCHED DOWN JUST EAST STUMP LAKE AND WEST OF HIGHWAY 1. IT TRACKED EASTWARD OVER MAINLY OPENED FIELDS FOR NEARLY 5 MILES AND ENDED AROUND 8.5 S OF MAPES AROUND 554 PM CDT. PHOTOS SHOW A PERISISTENT ROPE TOR
22:38 UTCTORNADO7 S LakotaNelson, NDA TORNADO TRACKED TO THE EAST SOUTHEAST FOR ABOUT TWO MILES OVER MAINLY OPENED FIELDS IN NORTHEAST WAMDUSKA TOWNSHIP. BRIEF DUST SWIRLS WERE NOTED BY MULTIPLE OBSERVERS. THIS TORNADO LIKELY ENDED BY 545 PM CDT.
22:38 UTCTORNADO7 S LakotaNelson, NDA TORNADO TRACKED TO THE EASTWARD OVER MAINLY OPENED FIELDS FROM NORTHEAST WAMDUSKA TOWNSHIP INTO NORTHEAST CENTRAL TOWNSHIP. MULTIPLE REPORTS AND PHOTOS SHOWED A PERSISTENT ROPE TORNADO WITH EPISODIC DUST SWIRLS THROUGH
22:59 UTCHAIL 15 Nnw McvilleNelson, NDHEAVY RAIN WITH A FEW DIME TO QUARTER SIZED HAIL.
23:25 UTCHAIL 1.254 Ese McvilleNelson, NDA FEW HAIL UP TO HALF DOLLAR SIZED JUST NORTH OF HIGHWAY 15...IN NORTHWEST LEE TOWNSHIP.
23:56 UTCHAIL 1.54 W SharonGriggs, NDOCASSIONAL NICKEL TO PING PONG BALL SIZED HAIL IN VERY HEAVY RAIN ACROSS SOUTHEAST LENORA TOWNSHIP.
23:56 UTCHAIL 1.55 W SharonGriggs, NDOCASSIONAL NICKEL TO PING PONG BALL SIZED HAIL IN VERY HEAVY RAIN ACROSS SOUTHEAST LENORA TOWNSHIP.
00:15 UTCFUNNEL CLOUD6 Ne CooperstownGriggs, NDBRIEF FUNNEL CLOUD OBSERVED JUST WEST OF THE STEELE COUNTY COUNTY LINE IN FAR SOUTHEAST ROMNESS TOWNSHIP.
00:15 UTCFUNNEL CLOUD7 Ne CooperstownGriggs, NDFUNNEL CLOUD OBSERVED JUST WEST OF THE STEELE COUNTY COUNTY LINE IN FAR SOUTHEAST ROMNESS TOWNSHIP.
00:16 UTCTORNADO 07 Ne CooperstownGriggs, NDTHIS TORNADO TRACKED INTERMITTENTLY FOR ABOUT 2 MILES ACROSS A PORTION OF THE SHEYENNE RIVER VALLEY AND ALONG THE STEELE COUNTY LINE TO AROUND 7 WSW OF FINLEY BY 722 PM CDT. LARGE TREE BRANCHES WERE BROKEN DOWN IN VARIOU
00:25 UTCHAIL 1.55 S SharonSteele, NDVERY HEAVY RAIN WITH OCASSIONAL LARGE HAIL... A FEW UP TO GOLF BALL SIZED.
00:25 UTCHAIL 1.755 S SharonSteele, NDVERY HEAVY RAIN WITH OCASSIONAL LARGE HAIL... A FEW UP TO GOLF BALL SIZED.
00:25 UTCHAIL 1.756 S SharonSteele, NDVERY HEAVY RAIN WITH OCASSIONAL LARGE HAIL... A FEW UP TO GOLF BALL SIZED.

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

This ground now

The live radar over the trackEvery 2017 tornado in North DakotaEvery tornado in North Dakota since 1950Warnings in force in North Dakota nowThe forecast where you are

The other tornadoes of September 1, 2017

2 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
September 15:38 PM CDTEF0Nelson, ND6.0150
September 17:16 PM CDTEF0Griggs, ND1.7150$1,000

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.