EF1 tornado, Meriden to Havana, Minnesota, September 20, 2018

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

September 20, 2018

Touchdown

6:35 PM CDT (23:35 UTC)

Lifted

6:42 PM CDT (23:42 UTC)

On the ground

7 minutes

Path length

8.1 miles (13.1 km)

Path width

300 yards (274 m)

Deaths

0

Injuries

0

County

Steele County

Touchdown point

44.059, -93.332

Lift-off point

44.093, -93.175

Record number

1809201735-01

124 damage points were recorded along this path by NWS MPX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF2. The highest wind the damage implies is 132 mph.

• Many trees down at residence. Concentrated damage
• round bales tossed into corn field, power lines snapped. Possible EF2
• side door was open. Possible EF2
• Likely 1 long tonrado. originally thought this was the start.

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

A violent outbreak of significant straight line winds, downburst winds, and multiple tornadoes occurred during the afternoon and early evening across southern Minnesota. ||During the afternoon of Thursday, September 20th, a warm front lifted northward across far southern Minnesota. By the late afternoon, the warm front lied from just south of the Minnesota River, northeast to around the city of Wabasha. ||Several thunderstorms developed in southwest Minnesota, and northwest Iowa. These storms moved into far southern Minnesota and quickly intensified and raced off to the east-northeast along, and north of this warm front. ||Damage reports started to come into the office around 4 PM CST in Martin County, with multiple reports of significant damage from south of Mankato, to Waseca, then northeast through Waterville, Morristown, Owatonna, Faribault, Northfield, Cannon Falls, and Red Wing before moving into west central Wisconsin. ||A long, and several day storm survey indicated at least XX confirmed tornadoes occurred in a widespread area of damaging winds from Martin County, northeast into west central Wisconsin. ||The most destruction part of the storm occurred around Waterville, Morristown, Owatonna, Faribault and Cannon Falls. These cities all reported homes, buildings and warehouses either damaged or destroyed. ||Hundreds of large, mature trees were uprooted or snapped along this path of destruction, including numerous trees up to 4 feet in diameter. In addition to the trees, structural damage was widespread including the Faribault airport where 80 planes were either damaged or destroyed as hangers were blown off their foundation. ||The towns of Waterville and Faribault had the most homes damaged which was associated with EF2 tornado damage. ||Two miles west of the Faribault airport, a resort area on Roberds Lake had upwords of 75 percent of the trees uprooted or blown down on the east side of the lake. Some of the trees landed on homes and split them in half.

This is the continued tornado track from the Waseca County tornado that moved an additional 7.2 miles through northwest Steele County. A storm survey, and high resolution satellite imagery indicated the tornado tracked mainly through corn and soy bean fields, and occasionally damaged a few sheds and outbuildings southwest of Medford. The worst damage was to a silo and grain bin which were destroyed by the tornado. This damage was consistent with EF1 damage with maximum wind speeds of 100 mph and a width of 350 yards.

A NWS storm survey, plus areal footage of drone and satellite data, concluded that an EF1 tornado started west of Owatonna, and tracked 6.5 miles across the southern and eastern portions of the town, before lifting east of the Brooktree Golf Course. The damage was consistent with EF1 damage with maximum wind speeds of 90 mph and a width of 300 yards. An outbuilding and silo were damaged near the start of the tornado track, with numerous large trees uprooted or blown down in the city of Owatonna. In addition to the tornado damage, severe straight-line winds from inflow of the tornado caused numerous large blown down trees and power poles on the south side of the track.

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 tornado watch, issued at 20:34 UTC and running to 00:47 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 0.10 chance of a tornado within 25 miles, in the hatched area where significant tornadoes were expected. The outlook in force was issued at 19:49 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.

Owatonna (OWA), 5 km from the path, in the two hours either side.

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

The Minneapolis radar (KMPX), 89 km away, was scanning. The volume nearest the touchdown began at 23:36 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 2018 tornado in MinnesotaEvery tornado in Minnesota since 1950Warnings in force in Minnesota nowThe forecast where you are

28 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.