Tornadoes · United States · Minnesota · 2017

EF0 tornado, Courtland, Minnesota, July 9, 2017

Name: EF0 tornado, Courtland, Minnesota, July 9, 2017
Start: 2017-07-10T02:37:00.000Z
End: 2017-07-10T02:41:00.000Z
Location: Courtland, Minnesota

This EF0 tornado ran 1.3 miles across Nicollet County on July 9, 2017, touching down at 9:37 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.

EF065 to 85 mphthis tornado
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
EF186 to 110 mph
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: EF0
Date: July 9, 2017
Touchdown: 9:37 PM CDT (02:37 UTC)
Lifted: 9:41 PM CDT (02:41 UTC)
On the ground: 4 minutes
Path length: 1.3 miles (2.1 km)
Path width: 50 yards (46 m)
Deaths: 0
Injuries: 0
County: Nicollet County
Touchdown point: 44.315, -94.352
Lift-off point: 44.315, -94.325
Record number: 1707092037-01

The damage survey

24 damage points were recorded along this path by NWS MPX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 100 mph.

insulation and debris northeast of barn that was damaged
wood piece northeast of damaged barn
roof torn off and lifted up, insulation blown northeast.
corn leaning toward the southeast

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

There were two tornadoes and many reports of very large hail. ||Storms brought strong winds, heavy rain, hail and tornadoes to south central Minnesota, damaging buildings and crops in Blue Earth, Nicollet and Sibley Counties.||The July 9 tornadoes, thunderstorms and hail hit south central Minnesota hard, with softball-sized hail reported in the Sibley County towns of Gibbon and Winthrop. The National Weather Service confirmed two tornadoes, one which did severe damage to a Courtland farm site.||That large hail and major thunderstorm surfaced quickly near the McLeod-Sibley county line, then continued south toward the Iowa border. Crops in Blue Earth, Nicollet and Sibley counties sustained severe damage, with the Blue Earth County Sheriff��s Office reporting over 600 acres hit there.||Still, the worst hail damage seemed to focus in rural Nicollet County, where corn fields were stripped and soybeans badly damaged. The University of Minnesota Extension Service, which conducted a Thursday clinic for regional farmers at the United Farmers Cooperative headquarters in Winthrop, said corn has the ability to come back somewhat from the damage, but the soybean crop for some farmers might be gone.

The tornado hit two farms, damaging sheds and other outbuildings. It also moved across fields, damaging crops. Some trees were also knocked down.

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.

In the hours before

Local storm report, Jul 9, 9:27 PM CDT, 10 minutes before

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Local storm report, Jul 9, 9:29 PM CDT, 8 minutes before

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Local storm report, Jul 9, 9:32 PM CDT, 5 minutes before

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Local storm report, Jul 9, 9:33 PM CDT, 4 minutes before

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Local storm report, Jul 9, 9:36 PM CDT, 1 minute before

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Local storm report, Jul 9, 9:37 PM CDT, 0 minutes before

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The surface observations

New Ulm Municipal (ULM), 13 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 Minneapolis radar (KMPX), 85 km away, was scanning. The volume nearest the touchdown began at 02:39 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 2017 tornado in Minnesota Every tornado in Minnesota since 1950 Warnings in force in Minnesota now The forecast where you are

The other tornadoes of July 9, 2017

1 more were confirmed in the United States that day.

Date	Time	Rating	Where	Path (mi)	Width (yd)	Deaths	Injuries	Damage
July 9	10:30 PM CDT	EF1	Blue Earth, MN	2.7	100

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.