Tornadoes · United States · Iowa · 2021
EF1 tornado, Henderson, Iowa, December 15, 2021
This EF1 tornado ran 0.6 miles across Mills County on December 15, 2021, touching down at 4:31 PM CST 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 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
- December 15, 2021
- Touchdown
- 4:31 PM CST (22:31 UTC)
- Lifted
- 4:32 PM CST (22:32 UTC)
- On the ground
- 1 minutes
- Path length
- 0.6 miles (1.0 km)
- Path width
- 50 yards (46 m)
- Deaths
- 0
- Injuries
- 0
- County
- Mills County
- Touchdown point
- 41.080, -95.440
- Lift-off point
- 41.080, -95.440
- Record number
- 2112151631-01
The damage survey
42 damage points were recorded along this path by NWS OAX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 110 mph.
- Several large wood poles snapped
- Large debris blown ene while blow in insulation coated the southeast side of trees
- Shed with south facing doors destroyed.
- Many large wooden poles broken
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
A low pressure system brought strong (both thunderstorm, and non-thunderstorm) winds, tornadoes, dust, snow, and record temperatures into eastern Nebraska and western Iowa. The event was determined to be a derecho meeting the criteria of wind damage.
A short-lived tornado developed on a farm where it quickly destroyed a metal building structure, flipping two trucks that were parked inside the building. The roof was flipped off of the structure and debris was distributed to the northeast. The tornado then impacted and snapped several wood power poles but did not cause any additional significant or highly focused damage.
From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.
The warnings
19 minutes of warning. NWS OAX issued a tornado warning for this county at 22:12 UTC, 19 minutes before the tornado touched down, in force until 22:45 UTC.
The county was under a tornado watch, issued at 19:23 UTC and running to 23:19 UTC.
| Issued (UTC) | Expired | Product | Office |
|---|---|---|---|
| 15:00 UTC | 08:20 UTC | High Wind Watch | OAX |
| 18:00 UTC | 00:25 UTC | Red Flag Warning | OAX |
| 18:00 UTC | 03:00 UTC | High Wind Warning | OAX |
| 18:00 UTC | 20:21 UTC | Fire Weather Watch | OAX |
| 19:23 UTC | 23:19 UTC | Tornado Watch | OAX |
| 21:35 UTC | 22:45 UTC | Severe Thunderstorm Warning | OAX |
| 21:55 UTC | 22:55 UTC | Severe Thunderstorm Warning | OAX |
| 22:01 UTC | 22:15 UTC | Tornado Warning | OAX |
| 22:12 UTC | 22:45 UTC | Tornado Warning | OAX |
| 22:30 UTC | 22:42 UTC | Tornado Warning | OAX |
| 03:00 UTC | 06:00 UTC | Wind Advisory | OAX |
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 forecast that day
The Storm Prediction Center had this point in a Moderate Risk, with a 0.10 chance of a tornado within 25 miles. The outlook in force was issued at 19:28 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 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.
Omaha, NE (KOAX), 12:00Z
10.5 hours before the tornado, 82 km from the path. December 15, 2021.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- -103670 J/kg
- Surface CAPE
- 0 J/kg
- Mixed-layer LCL
- 2165 m above ground
- 0-6 km bulk shear
- 42 kt
- 0-1 km bulk shear
- 38 kt
- 0-1 km storm-relative helicity
- 346 m²/s²
- 0-3 km storm-relative helicity
- 384 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
- 0-3 km lapse rate
- 3.2 K/km
Omaha, NE (KOAX), 00:00Z
1.5 hours after it, 82 km from the path. December 16, 2021.
- Mixed-layer CAPE
- 4 J/kg
- Mixed-layer CIN
- -66 J/kg
- Surface CAPE
- 69 J/kg
- Mixed-layer LCL
- 1685 m above ground
- 0-6 km bulk shear
- 103 kt
- 0-1 km bulk shear
- 47 kt
- 0-1 km storm-relative helicity
- -450 m²/s²
- 0-3 km storm-relative helicity
- -705 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
- 0-3 km lapse rate
- 6.4 K/km
The radar
The Omaha radar (KOAX), 82 km away, was scanning. The volume nearest the touchdown began at 22:29 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.
What was reported nearby
Local storm reports within 60 km of the path, in the three hours either side.
| Time (UTC) | Report | Where | County | Remark |
|---|---|---|---|---|
| 20:00 UTC | NON-TSTM WND DMG | 6 Ese Coburg | Montgomery, IA | 2-3 POWER POLES SHEARED OFF. TIME UNKNOWN. |
| 20:03 UTC | NON-TSTM WND GST 60 | 3 N Hastings | Mills, IA | |
| 22:14 UTC | TORNADO | 5 Wnw Tabor | Mills, IA | CORRECTS PREVIOUS TORNADO REPORT FROM 5 WNW TABOR. THE TORNADO BEGAN IN THE HILLS AND ROUGH TERRAIN NEAR PEASE RD AND QUIGG AVE, AND TRAVELLED QUICKLY NORTHEAST ALONG THE 10 MILE TRACK, LASTING APPROXIMATELY 9 MINUTES. T |
| 22:16 UTC | TORNADO | 4 Ssw Council Bluffs | Pottawattamie, IA | SHORT TRACK TORNADO STARTED NEAR THE MISSOURI RIVER AND TRAVEL 0.90 MILES TO THE NORTH NORTHEAST. LARGE BRANCHES WERE BLOWN DOWN BY THE TORNADO. |
| 22:16 UTC | TORNADO | 4 Ssw Council Bluffs | Pottawattamie, IA | UPDATE TO PREVIOUS REPORT. SHORT TRACK TORNADO STARTED NEAR THE MISSOURI RIVER AND TRAVEL 0.90 MILES TO THE NORTH NORTHEAST. LARGE BRANCHES WERE BLOWN DOWN BY THE TORNADO IN AN OTHERWISE UNPOPULATED PORTION OF THE MISSOU |
| 22:20 UTC | TSTM WND GST 62 | 1 Sw Council Bluffs | Pottawattamie, IA | MESONET STATION RCBI4 COUNCIL BLUFFS (I-80). |
| 22:21 UTC | TSTM WND DMG | 1 Ene Council Bluffs | Pottawattamie, IA | NINE LOADED COAL CARS ROLLED OFF TRACKS. |
| 22:22 UTC | TSTM WND DMG | 2 N Malvern | Mills, IA | POWER LINES ACROSS HIGHWAY 34. |
| 22:22 UTC | TSTM WND GST 83 | 8 Wsw Sidney | Fremont, IA | MESONET STATION NEAR SIDNEY AT I29/HWY 2. |
| 22:24 UTC | TSTM WND DMG | 5 W Mcclelland | Pottawattamie, IA | FIRE CHIEF REPORTED POWER LINES AND POLES DOWN FOR ABOUT A 1/4 MILE FROM HOMESTEAD AVE TO L-34 ALONG RAILROAD HIGHWAY. |
| 22:24 UTC | TORNADO | 4 Wsw Mcclelland | Pottawattamie, IA | A NARROW BUT STRONG TORNADO TRACKED ALONG ROAD L34 THROUGH SHERWOOD COUNTRY ESTATES BEFORE ENDING NEAR JUNIPER ROAD. THE MAXIMUM DAMAGE WAS SUSTAINED TO A HOME IN SHERWOOD COUNTRY ESTATES WHERE THE NARROW TORNADO REMOVED |
| 22:25 UTC | TSTM WND DMG | 3 Wnw Mcclelland | Pottawattamie, IA | MAJOR HOME DAMAGE IN WESTON. |
| 22:27 UTC | TSTM WND DMG | 1 Nw Treynor | Pottawattamie, IA | POWERLINES DOWN. |
| 22:29 UTC | TSTM WND DMG | 4 E Treynor | Pottawattamie, IA | LARGE TREE ON HOUSE. |
| 22:29 UTC | TSTM WND DMG | 4 W Underwood | Pottawattamie, IA | ROOF BLOWN OFF A HOUSE ON L-34 WEST OF UNDERWOOD. |
| 22:30 UTC | TSTM WND GST 92 | 2 Wsw Hastings | Mills, IA | DELAYED REPORT. 92 MPH FROM ESE. 2 OTHER WEATHER STATIONS IN THE SAME AREA RECORDED 66 MPH FROM THE SOUTH AND 81 MPH FROM THE SSW. |
| 22:31 UTC | TORNADO | 2 E Underwood | Pottawattamie, IA | A NARROW EF-2 TORNADO BEGAN PRODUCING DAMAGE NEAR MAHOGANY ROAD AND 290TH ST AND TRACKED NORTH NORTHEAST INTO THE SOUTHEAST EDGE OF NEOLA AND THEN CAUSED INTERMITTENT DAMAGE NEAR RAILROAD HIGHWAY NORTH OF NEOLA. THE MOST |
| 22:31 UTC | TORNADO | 4 S Henderson | Mills, IA | A SHORT-LIVED TORNADO DEVELOPED ON A FARM WHERE IT QUICKLY DESTROYED A METAL BUILDING STRUCTURE, FLIPPING TWO TRUCKS THAT WERE PARKED INSIDE THE BUILDING. THE ROOF WAS FLIPPED OFF OF THE STRUCTURE AND DEBRIS WAS DISTRIBU |
| 22:32 UTC | TORNADO | 2 Sw Neola | Pottawattamie, IA | FROM VIDEO AND TDS. TORNADO ON THE GROUND FOR AT LEAST 2 MINUTES. DAMAGE REPORTED IN NEOLA. |
| 22:34 UTC | TORNADO | 3 E Macedonia | Pottawattamie, IA | A TORNADO TRACKED FROM EAST OF MACEDONIA TO EAST OF OAKLAND, CROSSING APPROXIMATELY 9.5 MILES IN APPROXIMATELY 8 MINUTES WITH A MAXIMUM WIDTH OF APPROXIMATELY 50 YARDS. THE TORNADO CAUSED INTERMITTENT DAMAGE TO TREES, OU |
| 22:35 UTC | NON-TSTM WND GST 79 | 5 Ene Council Bluffs | Pottawattamie, IA | AWOS STATION KCBF COUNCIL BLUFFS AIRPORT. |
| 22:36 UTC | TSTM WND GST 79 | 5 Ene Council Bluffs | Pottawattamie, IA | |
| 22:38 UTC | TSTM WND DMG | 1 Ne Underwood | Pottawattamie, IA | LARGE GARAGE DOORS ON CITY BUILDING BLOWN IN. |
| 22:38 UTC | TSTM WND GST 80 | 2 Se Underwood | Pottawattamie, IA | |
| 22:40 UTC | TSTM WND DMG | 5 Ese Carson | Pottawattamie, IA | MACHINE SHED DESTROYED. |
| 22:41 UTC | TSTM WND DMG | Tennant | Shelby, IA | LARGE TREE FELL ON HOME. |
| 22:50 UTC | TSTM WND GST 67 | 3 Ene Avoca | Pottawattamie, IA | MESONET STATION RAVI4 AVOCA (I-80). |
| 22:53 UTC | TSTM WND DMG | 1 Se Shelby | Pottawattamie, IA | SEMI ROLLED OVER ON I-80W PER TWITTER PHOTO. |
| 22:55 UTC | NON-TSTM WND GST 72 | 5 S Harlan | Shelby, IA | AWOS STATION KHNR HARLAN AIRPORT. |
| 23:00 UTC | TSTM WND DMG | 1 Nw Treynor | Pottawattamie, IA | POWERLINES DOWN. |
| 23:00 UTC | TSTM WND DMG | 2 N Malvern | Mills, IA | POWER LINES ACROSS HIGHWAY 34. |
| 23:02 UTC | TORNADO | 1 Nw Atlantic | Cass, IA | STORM CHASER REPORTED TORNADO ON THE WEST SIDE OF ATLANTIC. |
| 23:02 UTC | TSTM WND DMG | 3 W Mcclelland | Pottawattamie, IA | SEMI ROLLED OVER. I-80W 13 MM NEAR MCCLELLAND, IA. |
| 23:15 UTC | TSTM WND GST 61 | 1 Sse Clarinda | Page, IA | |
| 23:15 UTC | NON-TSTM WND GST 61 | 2 Sse Clarinda | Page, IA | AWOS STATION KICL CLARINDA AIRPORT. |
| 23:22 UTC | TSTM WND DMG | 8 E Oakland | Pottawattamie, IA | TREE ON ROADWAY. US-6 38 MM. |
| 23:24 UTC | TSTM WND DMG | 5 E Council Bluffs | Pottawattamie, IA | TREE ON ROAD IA-92 AT 8 MM & EASTERN HILLS DRIVE. |
| 23:34 UTC | TSTM WND DMG | 2 Nnw Pacific Junction | Mills, IA | SEMI ROLLOVER. I-29N AT 35 MM. |
| 23:34 UTC | TSTM WND DMG | Neola | Pottawattamie, IA | OUT BUILDINGS BLOWN OVER, HOUSES DAMAGED, POWER LINES DOWN, GAS LEAK - TDS NOTED IN THE AREA ON RADAR. |
| 00:55 UTC | NON-TSTM WND GST 69 | 1 Sse Clarinda | Page, IA | RECORDED BY KICL AWOS. |
From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.
This ground now
The live radar over the trackEvery 2021 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are
The other tornadoes of December 15, 2021
124 more were confirmed in the United States that day.
| Date | Time | Rating | Where | Path (mi) | Width (yd) | Deaths | Injuries | Damage |
|---|---|---|---|---|---|---|---|---|
| December 15 | 1:27 PM CST | EF0 | Kearney, NE | 11.0 | 150 | $700,000 | ||
| December 15 | 1:29 PM CST | EF0 | Franklin, NE | 13.4 | 100 | $700,000 | ||
| December 15 | 1:33 PM CST | EF0 | Kearney, NE | 7.1 | 120 | $350,000 | ||
| December 15 | 1:44 PM CST | EF1 | Webster, NE | 14.8 | 180 | $400,000 | ||
| December 15 | 1:53 PM CST | EF1 | Adams, NE | 8.6 | 150 | $400,000 | ||
| December 15 | 2:03 PM CST | EF0 | Adams, NE | 7.2 | 60 | $302,000 | ||
| December 15 | 2:11 PM CST | EF1 | Hamilton, NE | 12.9 | 400 | $500,000 | ||
| December 15 | 2:26 PM CST | EF1 | Hamilton, NE | 12.0 | 400 | $500,000 | ||
| December 15 | 2:35 PM CST | EF1 | Polk, NE | 7.5 | 350 | $400,000 | ||
| December 15 | 3:03 PM CST | EF1 | Platte, NE | 0.8 | 30 | |||
| December 15 | 3:04 PM CST | EF2 | Platte, NE | 2.7 | 50 | 2 | ||
| December 15 | 3:11 PM CST | EF2 | Saline, NE | 23.7 | 70 | |||
| December 15 | 3:27 PM CST | EF1 | Colfax, NE | 1.5 | 30 | |||
| December 15 | 3:31 PM CST | EF2 | Cuming, NE | 6.3 | 100 | |||
| December 15 | 3:37 PM CST | EF1 | Cuming, NE | 4.8 | 50 | |||
| December 15 | 3:37 PM CST | EF1 | Cuming, NE | 1.8 | 50 | |||
| December 15 | 3:41 PM CST | EF1 | Cuming, NE | 0.4 | 50 | |||
| December 15 | 3:41 PM CST | EF1 | Saunders, NE | 16.6 | 100 | |||
| December 15 | 3:44 PM CST | EF2 | Cuming, NE | 11.2 | 200 | |||
| December 15 | 3:46 PM CST | EF1 | Saunders, NE | 0.7 | 100 | |||
| December 15 | 3:51 PM CST | EF1 | Cuming, NE | 11.2 | 20 | |||
| December 15 | 3:55 PM CST | EF2 | Cass, NE | 3.3 | 20 | |||
| December 15 | 4:05 PM CST | EF1 | Otoe, NE | 0.1 | 200 | |||
| December 15 | 4:05 PM CST | EF1 | Pawnee, NE | 0.2 | 20 | |||
| December 15 | 4:06 PM CST | EF0 | Pawnee, NE | 2.2 | 20 | |||
| December 15 | 4:06 PM CST | EF2 | Cass, NE | 3.6 | 150 | |||
| December 15 | 4:07 PM CST | EF1 | Pawnee, NE | 0.8 | 100 | |||
| December 15 | 4:09 PM CST | EF2 | Cass, NE | 2.6 | 200 | |||
| December 15 | 4:14 PM CST | EF1 | Mills, IA | 10.0 | 100 | |||
| December 15 | 4:15 PM CST | Unrated | Woodbury, IA | 0.8 | 20 | |||
| December 15 | 4:16 PM CST | EF0 | Pottawattamie, IA | 0.9 | 30 | |||
| December 15 | 4:20 PM CST | EF1 | Woodbury, IA | 4.6 | 75 | $250,000 | ||
| December 15 | 4:24 PM CST | EF2 | Pottawattamie, IA | 2.3 | 50 | |||
| December 15 | 4:25 PM CST | EF2 | Woodbury, IA | 8.4 | 100 | $500,000 | ||
| December 15 | 4:31 PM CST | EF2 | Pottawattamie, IA | 6.7 | 75 | |||
| December 15 | 4:34 PM CST | EF1 | Pottawattamie, IA | 9.6 | 50 | |||
| December 15 | 4:35 PM CST | EF1 | Woodbury, IA | 4.3 | 75 | $200,000 | ||
| December 15 | 4:39 PM CST | EF1 | Plymouth, IA | 3.7 | 75 | $50,000 | ||
| December 15 | 4:42 PM CST | EF1 | Ida, IA | 13.0 | 75 | $200,000 | ||
| December 15 | 4:48 PM CST | Unrated | Crawford, IA | 4.4 | 50 | |||
| December 15 | 4:49 PM CST | EF2 | Cass, IA | 27.1 | 100 | $350,000 | ||
| December 15 | 4:58 PM CST | EF0 | Ida, IA | 2.9 | 50 | $75,000 | ||
| December 15 | 4:59 PM CST | EF1 | Cherokee, IA | 11.2 | 250 | $1.0 million | ||
| December 15 | 5:00 PM CST | Unrated | Cherokee, IA | 1.8 | 50 | |||
| December 15 | 5:00 PM CST | EF1 | Cass, IA | 11.4 | 80 | $100,000 | ||
| December 15 | 5:01 PM CST | EF1 | Buena Vista, IA | 6.4 | 75 | $200,000 | ||
| December 15 | 5:05 PM CST | EF1 | Cherokee, IA | 3.8 | 75 | $250,000 | ||
| December 15 | 5:07 PM CST | EF1 | Buena Vista, IA | 6.9 | 150 | $100,000 | ||
| December 15 | 5:08 PM CST | EF1 | O'Brien, IA | 3.9 | 100 | $50,000 | ||
| December 15 | 5:10 PM CST | EF1 | Guthrie, IA | 11.4 | 70 | $100,000 | ||
| December 15 | 5:13 PM CST | EF2 | Sac, IA | 17.6 | 100 | $150,000 | ||
| December 15 | 5:14 PM CST | EF2 | Guthrie, IA | 19.7 | 100 | $450,000 | ||
| December 15 | 5:18 PM CST | EF2 | Buena Vista, IA | 4.8 | 100 | $250,000 | ||
| December 15 | 5:19 PM CST | EF1 | Carroll, IA | 9.7 | 80 | $80,000 | ||
| December 15 | 5:21 PM CST | EF2 | Guthrie, IA | 30.0 | 300 | $470,000 | ||
| December 15 | 5:27 PM CST | EF2 | Guthrie, IA | 23.4 | 150 | $801,000 | ||
| December 15 | 5:29 PM CST | EF2 | Greene, IA | 5.5 | 100 | $1.2 million | ||
| December 15 | 5:32 PM CST | EF2 | Greene, IA | 5.8 | 100 | $500,000 | ||
| December 15 | 5:34 PM CST | Unrated | Calhoun, IA | 1.3 | 40 | |||
| December 15 | 5:34 PM CST | EF2 | Greene, IA | 2.7 | 70 | $20,000 |
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.