Tornadoes · United States · North Dakota · 2011

EF0 tornado, Sutton to Hannaford, North Dakota, July 17, 2011

From Sutton to Hannaford, this EF0 tornado ran 1.5 miles across Griggs County on July 17, 2011, touching down at 3:16 PM CDT and reaching 75 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
July 17, 2011
Touchdown
3:16 PM CDT (20:16 UTC)
Lifted
3:18 PM CDT (20:18 UTC)
On the ground
2 minutes
Path length
1.5 miles (2.5 km)
Path width
75 yards (69 m)
Deaths
0
Injuries
0
County
Griggs County
Touchdown point
47.342, -98.259
Lift-off point
47.320, -98.255
Record number
1107171416-01

What the Weather Service recorded

Early in the afternoon of the 17th, one supercell tracked across extreme southwest Benson county, down through western Eddy county, and into Griggs county. This cell maintained a very slow southeast movement along its entire track. The supercell fed off an extremely unstable atmosphere, with surface temperatures in the 80s and 90s and dew point readings in the mid to upper 70s. By late afternoon into the early evening, more storms broke out along and south of the Interstate 94 corridor.

This tornado tracked intermittently along the path and knocked down several trees in shelterbelts. Peak winds were estimated at 85 mph.

Trees and limbs were blown down along the tornado path. 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

19 minutes of warning. NWS FGF issued a tornado warning for this county at 19:57 UTC, 19 minutes before the tornado touched down, in force until 20:45 UTC.

The county was under a tornado watch, issued at 17:49 UTC and running to 20:41 UTC.

Issued (UTC)ExpiredProductOffice
15:00 UTC17:49 UTCSevere Thunderstorm WatchFGF
17:49 UTC20:41 UTCTornado WatchFGF
19:24 UTC20:00 UTCTornado WarningFGF
19:57 UTC20:45 UTCTornado WarningFGF
20:34 UTC21:15 UTCTornado WarningFGF
20:41 UTC03:00 UTCTornado WatchFGF

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 Moderate Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 19:57 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

8.3 hours before the tornado, 195 km from the path. July 17, 2011.

Skew-T log-pSkew-T log-p diagram, Bismarck Municip, ND at 12:00Z on 2011-07-17Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 4227 joules per kilogram, CIN -184, lifted condensation level 1037 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 2011-07-17The 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 156 square meters per square second, 0 to 6 km bulk shear 34 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
4227 J/kg
Mixed-layer CIN
-184 J/kg
Surface CAPE
509 J/kg
Mixed-layer LCL
1037 m above ground
0-6 km bulk shear
34 kt
0-1 km bulk shear
20 kt
0-1 km storm-relative helicity
156 m²/s²
0-3 km storm-relative helicity
276 m²/s²
Significant tornado parameter
0.0
Supercell composite
37.4
0-3 km lapse rate
3.0 K/km

Open this sounding in Storm Lab

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

3.7 hours after it, 195 km from the path. July 18, 2011.

Skew-T log-pSkew-T log-p diagram, Bismarck Municip, ND at 00:00Z on 2011-07-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 6851 joules per kilogram, CIN -4, lifted condensation level 1087 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, Bismarck Municip, ND at 00:00Z on 2011-07-18The 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 -33 square meters per square second, 0 to 6 km bulk shear 41 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
6851 J/kg
Mixed-layer CIN
-4 J/kg
Surface CAPE
5806 J/kg
Mixed-layer LCL
1087 m above ground
0-6 km bulk shear
41 kt
0-1 km bulk shear
8 kt
0-1 km storm-relative helicity
-33 m²/s²
0-3 km storm-relative helicity
-90 m²/s²
Significant tornado parameter
-2.6
Supercell composite
-9.1
0-3 km lapse rate
7.4 K/km

Open this sounding in Storm Lab

The radar

The Fargo/Grand Forks radar (KMVX), 73 km away, was scanning. The volume nearest the touchdown began at 20:13 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
18:42 UTCTORNADO2 W JuanitaFoster, NDTORNADO ON THE GROUND FOR 3 TO 4 MINUTES.
19:28 UTCTORNADO10 Ene KensalFoster, NDBRIEF TOUCHDOWN.
19:35 UTCTORNADO 01 Sw SuttonGriggs, NDTHIS TORNADO TRACKED INTERMITTENTLY FOR ABOUT 5 MILES TO AROUND 2 WSW OF REVERE BY 250 PM CDT. SEVERAL TREES WERE KNOCKED DOWN IN SHELTER BELTS ALONG THE ROUTE. MAXIMUM WIDTH ESTIMATED AT 100 YARDS AND PEAK WINDS ESTIMAT
20:16 UTCTORNADO 04 W HannafordGriggs, NDBRIEF TOUCHDOWN FOR APPROXIMATELY 2 MINUTES. TREES AND TREE LIMBS BLOWN DOWN.
20:16 UTCTORNADO4 W HannafordGriggs, NDBRIEF TOUCHDOWN FOR APPROXIMATELY 2 MINUTES.
21:15 UTCHAIL 2.755 S PillsburyBarnes, ND
21:36 UTCHAIL 1.75PageCass, NDPUBLIC REPORT RELAYED VIA MEDIA

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

This ground now

The live radar over the trackEvery 2011 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 17, 2011

8 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
July 1711:48 AM CDTEF0Wells, ND0.020
July 171:09 PM CDTEF1Eddy, ND1.0150$10,000
July 171:42 PM CDTEF0Foster, ND1.530
July 172:28 PM CDTEF0Foster, ND0.020
July 172:35 PM CDTEF0Griggs, ND5.0100
July 175:23 PM CDTEF0Cass, ND0.515
July 175:57 PM CDTEF3LaMoure, ND16.28801$500,000
July 177:06 PM CDTEF0Dickey, ND0.125

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.