Tornadoes · United States · Nebraska · 2017

EF0 tornado, Potter to Brownson, Nebraska, August 15, 2017

From Potter to Brownson, this EF0 tornado ran 6.8 miles across Cheyenne County on August 15, 2017, touching down at 6:10 PM MDT 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
August 15, 2017
Touchdown
6:10 PM MDT (00:10 UTC)
Lifted
6:25 PM MDT (00:25 UTC)
On the ground
15 minutes
Path length
6.8 miles (10.9 km)
Path width
50 yards (46 m)
Deaths
0
Injuries
0
County
Cheyenne County
Touchdown point
41.330, -103.310
Lift-off point
41.320, -103.180
Record number
1708151810-01

What the Weather Service recorded

Thunderstorms produced large hail, strong winds, locally heavy rain and a weak tornado across portions of the Nebraska Panhandle.

A weak tornado touched down in open country eight miles north of Potter. The tornado was obscured by heavy rain. The tornado moved east and lifted 10 miles northeast of Potter. No damage was reported.

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

The warnings

26 minutes of warning. NWS CYS issued a tornado warning for this county at 23:44 UTC, 26 minutes before the tornado touched down, in force until 00:30 UTC.

The county was under a severe thunderstorm watch, issued at 22:05 UTC and running to 01:37 UTC.

Issued (UTC)ExpiredProductOffice
22:05 UTC01:37 UTCSevere Thunderstorm WatchCYS
23:44 UTC00:30 UTCTornado WarningCYS
00:20 UTC01:00 UTCTornado WarningCYS
00:52 UTC01:26 UTCSevere Thunderstorm WarningCYS
01:20 UTC04:15 UTCFlood AdvisoryCYS

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. The outlook in force was issued at 19:53 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.

Denver, CO (KDEN), 00:00Z

0.2 hours before the tornado, 162 km from the path. August 16, 2017.

Skew-T log-pSkew-T log-p diagram, Denver, CO at 00:00Z on 2017-08-16Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 467 joules per kilogram, CIN -27, lifted condensation level 2755 meters above ground. Wind barbs in knots down the right edge.LCLEL10008507005003002001001 km2 km3 km6 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, Denver, CO at 00:00Z on 2017-08-16The 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 -37 square meters per square second, 0 to 6 km bulk shear 29 knots.193958Sfc1 km3 km6 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
467 J/kg
Mixed-layer CIN
-27 J/kg
Surface CAPE
735 J/kg
Mixed-layer LCL
2755 m above ground
0-6 km bulk shear
29 kt
0-1 km bulk shear
10 kt
0-1 km storm-relative helicity
-37 m²/s²
0-3 km storm-relative helicity
77 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.2
0-3 km lapse rate
9.9 K/km

Open this sounding in Storm Lab

Denver, CO (KDEN), 12:00Z

11.8 hours after it, 162 km from the path. August 16, 2017.

Skew-T log-pSkew-T log-p diagram, Denver, CO at 12:00Z on 2017-08-16Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 41 joules per kilogram, CIN -62, lifted condensation level 1589 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 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, Denver, CO at 12:00Z on 2017-08-16The 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 0 square meters per square second, 0 to 6 km bulk shear 16 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
41 J/kg
Mixed-layer CIN
-62 J/kg
Surface CAPE
468 J/kg
Mixed-layer LCL
1589 m above ground
0-6 km bulk shear
16 kt
0-1 km bulk shear
14 kt
0-1 km storm-relative helicity
0 m²/s²
0-3 km storm-relative helicity
37 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
6.6 K/km

Open this sounding in Storm Lab

The radar

The Cheyenne radar (KCYS), 132 km away, was scanning. The volume nearest the touchdown began at 00:12 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
23:00 UTCHEAVY RAIN 1.65 Nw HarrisburgBanner, NE
23:18 UTCTSTM WND GST 5814 N KimballBanner, NEESTIMATED GUSTS 55-60 MPH.
23:18 UTCHAIL 114 N KimballBanner, NE
23:23 UTCHAIL 2.757 Se HarrisburgBanner, NE
23:42 UTCHAIL 15 Se HarrisburgBanner, NENICKEL TO QUARTER SIZE HAIL ACCUMULATED 3-4 INCHES DEEP ON HIGHWAY 71.
23:55 UTCHAIL 1.57 N DixKimball, NE
00:10 UTCTORNADO8 N PotterCheyenne, NEPOSSIBLE RAIN-WRAPPED TORNADO ON THE GROUND.
00:23 UTCTORNADO10 Ne PotterCheyenne, NETORNADO ON GROUND.
00:25 UTCHAIL 19 Ne PotterCheyenne, NE
01:13 UTCHAIL 1.2510 E GurleyCheyenne, NEHAND HELD ANEMOMETER RECORDED 72 MPH.
01:13 UTCHAIL 1.2510 E GurleyCheyenne, NEHAND HELD ANOMETER RECORDED 72 MPH.

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 NebraskaEvery tornado in Nebraska since 1950Warnings in force in Nebraska nowThe forecast where you are

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.