Tornadoes · United States · North Dakota · 2011

EF1 tornado, Revere to Hannaford, North Dakota, July 16, 2011

Name: EF1 tornado, Revere to Hannaford, North Dakota, July 16, 2011
Start: 2011-07-17T00:20:00.000Z
End: 2011-07-17T00:24:00.000Z
Location: Revere to Hannaford, North Dakota

From Revere to Hannaford, this EF1 tornado ran 1.0 miles across Griggs County on July 16, 2011, touching down at 7:20 PM CDT and reaching 100 yards wide. It killed nobody, and did $10,000 of property damage.

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.

EF065 to 85 mph
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
EF186 to 110 mphthis tornado
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
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.
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.
EF4166 to 200 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
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.
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 16, 2011
Touchdown: 7:20 PM CDT (00:20 UTC)
Lifted: 7:24 PM CDT (00:24 UTC)
On the ground: 4 minutes
Path length: 1.0 miles (1.6 km)
Path width: 100 yards (91 m)
Deaths: 0
Injuries: 0
Property damage: $10,000
Crop damage: $50,000
County: Griggs County
Touchdown point: 47.350, -98.310
Lift-off point: 47.381, -98.271
Record number: 1107161820-01

What the Weather Service recorded

The 16th was hot and humid with late afternoon temperatures topping out in the 80s to around 90 and dew point temperatures well into the 70s. This created a large amount of instability. By early in the evening, thunderstorms began to flare up again aided by a weak low level jet.

This tornado was first reported by an observer located south of Sutton and looking east towards Hannaford. The tornado snapped down several trees in a shelterbelt and flattened part of a corn field before lifting. Peak winds were estimated at 95 mph.

The tornado knocked down several trees in various shelterbelts along its route. At one farmstead several sheets of steel roofing were ripped up and tossed off of a shed and numerous tree branches were scattered about. Peak winds were estimated at 95 mph.

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

What forecasters said that day

The local office's own words before the tornado touched down, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Grand Forks, ND wrote its last area forecast discussion before the tornado touched down at Jul 16, 3:00 PM CDT, 4 hours 20 minutes earlier.

Area forecast discussion, Jul 16, 3:00 PM CDT, 4 hours 20 minutes before

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Hazardous weather outlook, Jul 16, 5:57 AM CDT, 13 hours 23 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GRAND FORKS ND
557 AM CDT SAT JUL 16 2011

MNZ001>009-013>017-022>024-027>032-040-NDZ006>008-014>016-024-
026>030-038-039-049-052>054-171100-
WEST POLK-NORMAN-CLAY-KITTSON-ROSEAU-LAKE OF THE WOODS-
WEST MARSHALL-EAST MARSHALL-NORTH BELTRAMI-PENNINGTON-RED LAKE-
EAST POLK-NORTH CLEARWATER-SOUTH BELTRAMI-MAHNOMEN-
SOUTH CLEARWATER-HUBBARD-WEST BECKER-EAST BECKER-WILKIN-
WEST OTTER TAIL-EAST OTTER TAIL-WADENA-GRANT-TOWNER-CAVALIER-
PEMBINA-BENSON-RAMSEY-EASTERN WALSH-EDDY-NELSON-GRAND FORKS-
GRIGGS-STEELE-TRAILL-BARNES-CASS-RANSOM-SARGENT-RICHLAND-
WESTERN WALSH-
557 AM CDT SAT JUL 16 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EASTERN NORTH
DAKOTA...WEST CENTRAL AND NORTHWEST MINNESOTA.

.DAY ONE...TODAY AND TONIGHT

THERE IS A SLIGHT CHANCE FOR SEVERE THUNDERSTORMS THIS AFTERNOON
AND EVENING...WITH THE HIGHEST PROBABILITIES NEAR THE
INTERNATIONAL BORDER. MOIST...UNSTABLE AIR WILL CONTINUE TO POUR
INTO THE NORTHERN PLAINS. WHILE HOT TEMPERATURES ALOFT WILL KEEP
THUNDERSTORM DEVELOPMENT FROM BECOMING WIDESPREAD...ANY STORMS
THAT DEVELOP COULD BECOME SEVERE DUE TO STRONG WINDS IN THE UPPER
LEVELS OF THE ATMOSPHERE. HAIL AND DAMAGING WINDS WILL BE THE
PRIMARY THREAT...ALTHOUGH AN ISOLATED TORNADO IS NOT OUT OF THE
QUESTION.

THE HUMID CONDITIONS AND TEMPERATURES REACHING THE 90S WILL ALLOW
HEAT INDEX VALUES TO CLIMB ABOVE 100 OR EVEN 105 DEGREES ACROSS A
LARGE PORTION OF THE FORECAST AREA. EXCESSIVE HEAT WARNINGS AND
HEAT ADVISORIES ARE IN EFFECT.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THERE WILL BE A CHANCE FOR THUNDERSTORMS ON SUNDAY AFTERNOON AND
EVENING...WITH SOME HAIL AND DAMAGING WINDS POSSIBLE.

THE HUMID CONDITIONS AND TEMPERATURES REACHING THE 90S WILL ALLOW
HEAT INDEX VALUES TO CLIMB ABOVE 100 OR EVEN DEGREES ACROSS A
LARGE PORTION OF THE FORECAST AREA. EXCESSIVE HEAT WARNINGS AND
HEAT ADVISORIES ARE IN EFFECT THROUGH TUESDAY EVENING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED NORTH OF THE HIGHWAY 200
CORRIDOR.

JR

In the hours before

Special weather statement, Jul 16, 1:28 PM CDT, 5 hours 52 minutes before

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Local storm report, Jul 16, 1:53 PM CDT, 5 hours 27 minutes before

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Local storm report, Jul 16, 5:32 PM CDT, 1 hour 48 minutes before

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Local storm report, Jul 16, 7:14 PM CDT, 6 minutes before

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Local storm report, Jul 16, 7:20 PM CDT, 0 minutes before

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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

0.3 hours before the tornado, 194 km from the path. July 17, 2011.

Skew-T log-p

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.

Hodograph

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: 4274 J/kg
Mixed-layer CIN: -20 J/kg
Surface CAPE: 3735 J/kg
Mixed-layer LCL: 1100 m above ground
0-6 km bulk shear: 38 kt
0-1 km bulk shear: 9 kt
0-1 km storm-relative helicity: 54 m²/s²
0-3 km storm-relative helicity: 205 m²/s²
Significant tornado parameter: 2.4
Supercell composite: 13.9
0-3 km lapse rate: 6.9 K/km

Open this sounding in Storm Lab

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

11.7 hours after it, 194 km from the path. July 17, 2011.

Skew-T log-p

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.

Hodograph

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

The surface observations

Rands (S32), 15 km from the path, in the two hours either side.

Time (UTC)	Temp (°F)	Dew point (°F)	Wind	Gust (kt)	Pressure (mb)	Weather
00:00 UTC

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

The radar

The Fargo/Grand Forks radar (KMVX), 75 km away, was scanning. The volume nearest the touchdown began at 00:21 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.

This ground now

The live radar over the track Every 2011 tornado in North Dakota Every tornado in North Dakota since 1950 Warnings in force in North Dakota now The forecast where you are

The other tornadoes of July 16, 2011

9 more were confirmed in the United States that day.

Date	Time	Rating	Where	Path (mi)	Width (yd)	Damage
July 16	5:35 PM CDT	EF1	Burleigh, ND	6.2	50	$10,000
July 16	7:10 PM CDT	EF1	Griggs, ND	1.2	50
July 16	7:31 PM CDT	EF0	Wells, ND	5.6	30
July 16	7:38 PM CDT	EF0	Wells, ND	1.2	30
July 16	7:51 PM CDT	EF0	Benson, ND	3.0	100
July 16	8:18 PM CDT	EF0	Benson, ND	3.0	50
July 16	8:25 PM CDT	EF0	Marshall, MN	0.1	10
July 16	9:47 PM CDT	EF0	Emmons, ND	1.9	30	$30,000
July 16	9:48 PM CDT	EF0	Ramsey, ND	0.2	10

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.