EF1 tornado, Chester, Minnesota, July 19, 2017

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.

Rating

EF1

Date

July 19, 2017

Touchdown

5:07 PM CDT (22:07 UTC)

Lifted

5:08 PM CDT (22:08 UTC)

On the ground

1 minutes

Path length

0.8 miles (1.2 km)

Path width

25 yards (23 m)

Deaths

0

Injuries

0

Property damage

$40,000

County

Olmsted County

Touchdown point

43.993, -92.320

Lift-off point

43.992, -92.305

Record number

1707191607-01

12 damage points were recorded along this path by NWS ARX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 90 mph.

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

A line of severe thunderstorms moved across southeast Minnesota during the late afternoon of July 19th. These storms produced two EF-1 tornadoes. The first touched down in the Chester Woods Park near Chester (Olmsted County) and did extensive tree damage in the park. The second tornado touched down southeast of Wykoff (Fillmore County) damaging trees, crops and a barn. The damaging winds did extensive damage to a turkey farm near Claremont (Dodge County) and blew down trees south of Altura (Winona County). During the late evening of the 19th into the early morning hours of the 20th, thunderstorms with heavy rain produced some mudslides near Minneiska (Winona County), Homer (Winona County) and northwest of La Crescent (Houston County).

An EF-1 tornado touched down southeast of Rochester and produced intermittent damage as it moved east through Chester Woods Park. Extensive tree damage occurred along parts of the short path in the wooded areas of the park. The park superintendent estimated between 4 and 10 acres of trees were flattened in the park. Near the park's beach, downed trees landed on the beach house and a fence.

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

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 20:29 UTC and running to 00:46 UTC.

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 Storm Prediction Center had this point in a Enhanced Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 20:01 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 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.

Rochester / St Mary (9MN), 14 km from the path, in the two hours either side.

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

The La Crosse radar (KARX), 92 km away, was scanning. The volume nearest the touchdown began at 22:06 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.

Local storm reports within 60 km of the path, in the three hours either side.

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

The live radar over the trackEvery 2017 tornado in MinnesotaEvery tornado in Minnesota since 1950Warnings in force in Minnesota nowThe forecast where you are

9 more were confirmed in the United States that day.

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.

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.