Tornadoes · United States · North Dakota · 2015

EF1 tornado, Tolna, North Dakota, July 23, 2015

This EF1 tornado ran 0.5 miles across Nelson County on July 23, 2015, touching down at 10:36 PM CDT and reaching 350 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 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 23, 2015
Touchdown
10:36 PM CDT (03:36 UTC)
Lifted
10:40 PM CDT (03:40 UTC)
On the ground
4 minutes
Path length
0.5 miles (0.8 km)
Path width
350 yards (320 m)
Deaths
0
Injuries
0
County
Nelson County
Touchdown point
47.830, -98.440
Lift-off point
47.830, -98.430
Record number
1507232136-01

The damage survey

17 damage points were recorded along this path by NWS FGF, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 110 mph.

  • Quonset destroyed and blown into shelter belt

Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.

What the Weather Service recorded

Thunderstorms formed along a cold front during the evening hours of July 23rd. These storms produced large hail, strong winds, and a few tornadoes.

The tornado uprooted several trees, bent a tower, and blew a quonset storage building off its foundation. Most of the damage occurred in the vicinity of Lee Avenue on the south side of Tolna, including the city park area. A power outage also occurred as the tornado hit. Peak winds were estimated at 110 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.

The county was under a severe thunderstorm watch, issued at 21:04 UTC and running to 05:24 UTC.

Issued (UTC)ExpiredProductOffice
21:04 UTC05:24 UTCSevere Thunderstorm WatchFGF
02:54 UTC04:00 UTCSevere Thunderstorm WarningFGF
03:09 UTC04:15 UTCSevere Thunderstorm WarningFGF
03:40 UTC04:45 UTCSevere Thunderstorm WarningFGF
04:14 UTC04:36 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 Slight Risk, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 00:55 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), 00:00Z

3.6 hours before the tornado, 208 km from the path. July 24, 2015.

Skew-T log-pSkew-T log-p diagram, Bismarck Municip, ND at 00:00Z on 2015-07-24Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 1074 joules per kilogram, CIN -71, lifted condensation level 2327 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 00:00Z on 2015-07-24The 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 74 square meters per square second, 0 to 6 km bulk shear 25 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
1074 J/kg
Mixed-layer CIN
-71 J/kg
Surface CAPE
2231 J/kg
Mixed-layer LCL
2327 m above ground
0-6 km bulk shear
25 kt
0-1 km bulk shear
17 kt
0-1 km storm-relative helicity
74 m²/s²
0-3 km storm-relative helicity
137 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.0
0-3 km lapse rate
8.5 K/km

Open this sounding in Storm Lab

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

8.4 hours after it, 208 km from the path. July 24, 2015.

Skew-T log-pSkew-T log-p diagram, Bismarck Municip, ND at 12:00Z on 2015-07-24Temperature 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 -84069, lifted condensation level 1075 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 12:00Z on 2015-07-24The 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 -92 square meters per square second, 0 to 6 km bulk shear 43 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
0 J/kg
Mixed-layer CIN
-84069 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
1075 m above ground
0-6 km bulk shear
43 kt
0-1 km bulk shear
16 kt
0-1 km storm-relative helicity
-92 m²/s²
0-3 km storm-relative helicity
33 m²/s²
Significant tornado parameter
0.0
Supercell composite
-0.0
0-3 km lapse rate
3.8 K/km

Open this sounding in Storm Lab

The surface observations

Devils_lake (DVL), 47 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
01:55 UTC80.669.8100° 7 kt1005.1
02:15 UTC80.669.8100° 9 kt1005.1
02:35 UTC73.462.6360° 9 kt1005.8VCTS
02:55 UTC66.257.2330° 18 kt251006.8TS
03:15 UTC66.259280° 9 kt271006.8TS
03:35 UTC6860.890° 7 kt1006.8TS
03:55 UTC66.260.890° 11 kt1005.8TS
04:15 UTC66.260.810° 7 kt1005.1TS
04:35 UTC64.457.270° 10 kt1006.1
04:55 UTC64.457.2100° 13 kt1005.1
05:15 UTC66.259110° 15 kt1005.1
05:35 UTC66.259110° 9 kt181006.1

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

The radar

The Fargo/Grand Forks radar (KMVX), 90 km away, was scanning. The volume nearest the touchdown began at 03:35 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
02:40 UTCTSTM WND DMGWebsterRamsey, NDAN ALMOST COMPLETED NEW SEED BUILDING WAS BLOWN OVER. THIS BUILDING WAS WOODEN FRAMED WITH ABOUT 10 RAFTERS LEFT TO PUT ON BEFORE COMPLETION. TIME ESTIMATED FROM RADAR.
03:27 UTCTSTM WND GST 5925 E New RockfordEddy, NDNDAWN 8 MILES NORTH OF MCHENRY...PEAK MEASURED GUST.
03:36 UTCTORNADOTolnaNelson, NDTHIS TORNADO BEGAN AROUND 1036PM AND ENDED AROUND 1040PM IN THE TOWN OF TOLNA. ESTIMATED PEAK WINDS ARE AROUND 110 MPH...WHICH IS AN EF-1 RATING. DAMAGE INCLUDED SEVERAL UPROOTED TREES...A BENT TOWER...AND A QUONSET STOR
03:40 UTCTSTM WND DMGTolnaNelson, NDHIGHWAY SUPERINTENDANT REPORTED TREES FALLING ONTO ROOF OF CITY SHOP. ROW OF TREES DOWN WITHIN CITY PARK. 60 BY 40 FOOT BUILDING SOUTH END OF TOWN TOTALLY DEMOLISHED.
03:40 UTCTSTM WND DMGTolnaNelson, NDEM RELAYED THE FOLLOWING...FARMERS UNION - EXTENSIVE DAMAGE TO A LEAN TO. MINOR DAMAGE TO SEVERAL GARAGES. BUILDING ON A HOMEOWNERS PROPERTY SUFFERED TOTAL LOSS. NUMEROUS TREES DAMAGED THROUGHOUT THE CITY.
03:48 UTCTSTM WND GST 612 Ne PekinNelson, NDNDAWN NEAR PEKIN.
04:05 UTCTSTM WND DMG9 Sse MichiganNelson, NDSEVERAL LARGE 6-8 FOOT LONG BRANCHES BROKEN OFF AND LAYING ON THE GROUND...AT LEAST 5-6 INCHES IN DIAMETER. TIME ESTIMATED FROM RADAR.

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

This ground now

The live radar over the trackEvery 2015 tornado in North DakotaEvery tornado in North Dakota since 1950Warnings in force in North Dakota nowThe forecast where you are

The other tornadoes of July 23, 2015

7 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
July 234:47 PM CDTEF0Thomas, NE0.110
July 238:30 PM CDTEF1Beadle, SD2.8440$50,000
July 2310:07 PM CDTEF0Miner, SD0.7150
July 2310:25 PM CDTEF0Miner, SD0.8250
July 2310:49 PM CDTEF0Miner, SD1.6250
July 2311:51 PM CDTEF1Traill, ND0.425
July 2312:46 AM CDTEF1Norman, MN5.4500

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.