EF1 tornado, Bassett to Alta Vista, Iowa, December 15, 2021

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

December 15, 2021

Touchdown

7:15 PM CST (01:15 UTC)

Lifted

7:18 PM CST (01:18 UTC)

On the ground

3 minutes

Path length

4.0 miles (6.4 km)

Path width

180 yards (165 m)

Deaths

0

Injuries

0

Property damage

$255,000

County

Chickasaw County

Touchdown point

43.097, -92.483

Lift-off point

43.148, -92.446

Record number

2112151915-01

25 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 94 mph.

• Photos by Chickasaw County EMA.
• Photo by Chickasaw County EMA.

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

An intense storm system moved across the Upper Midwest on December 15th and produced a rare severe weather outbreak across northeast Iowa. Eight tornadoes occurred across parts of Floyd, Chickasaw and Howard Counties. Four of these tornadoes were rated EF1 with one moving through Rudd (Floyd County) where the roof was removed from the library and several homes and a church were heavily damaged. The other tornadoes largely moved through rural areas damaging trees, power lines and farm buildings. In addition to the tornadoes, damaging winds occurred that blew over a semi in Floyd (Floyd County) and damaged numerous homes across the region. The Governor of Iowa declared a state of disaster emergency for Allamakee, Chickasaw, Fayette, Floyd, Howard, Mitchell and Winneshiek Counties. A federal disaster was declared for Floyd, Howard and Mitchell Counties.

An EF1 tornado formed west of North Washington and moved to northeast for about 4 miles before dissipating. The tornado damaged trees and some farm outbuilding along its path.

The second tornado of the night in Chickasaw County formed southwest of Alta Vista and moved northeast before crossing into Howard County along County Line Road just east of the Little Wapsipinicon River. This tornado was rated EF0. The tornado damaged a greenhouse facility, otherwise, damage was limited to trees.

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.

The county was under a tornado watch, issued at 23:30 UTC and running to 03:17 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 Moderate 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 00:54 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.

Charles City (CCY), 13 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), 129 km away, was scanning. The volume nearest the touchdown began at 01:14 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 2021 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

124 more were confirmed in the United States that day.

All 125 of them

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.