EF1 tornado, Iowa Falls to Hansell, 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

6:27 PM CST (00:27 UTC)

Lifted

6:43 PM CST (00:43 UTC)

On the ground

16 minutes

Path length

22.2 miles (35.7 km)

Path width

140 yards (128 m)

Deaths

0

Injuries

0

Property damage

$35,000

Counties

Hardin and Franklin counties

Touchdown point

42.482, -93.284

Lift-off point

42.744, -93.033

Record number

2112151827-01

1 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 88 mph.

• Satellite signatures show substantial tree damage on the east side of this farmstead. Tough to gauge the full extent, but given the lack of foliage and fast storm motion, likely saw EF1 damage here.

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

December 15, 2021 was an unprecedented and historic event for the state of Iowa and the central US. It featured the first-ever December derecho observed anywhere in the United States and the first Moderate Risk of severe thunderstorms issued by the NWS Storm Prediction Center in December for Iowa. Unofficially, it set the new single-day Iowa records for the most tornadoes and the most EF-2/F-2 or stronger tornadoes since 1950. Finally, it will break the all-time December record high temperature for Iowa. ||Tornadoes: There were 63 confirmed tornadoes that occurred in Iowa, 21 of which were rated EF-2. Sixty three is unofficially the most tornadoes in Iowa in a single day with the previous being 35 tornadoes on August 31, 2014. Further, 21 EF-2 tornadoes is unofficially the most EF-2/F-2 or stronger tornadoes in a single day with the previous being 16 tornadoes on June 7, 1984. Prior to this event, a total of 5 tornadoes had occurred in Iowa in December since 1950 with all of them in southeastern Iowa. | |Thunderstorm Wind: Numerous straight line wind gusts were also associated with these thunderstorms, some in excess of 80 mph. During the event, nearly the entire state of Iowa was under a Severe Thunderstorm Warning at some point. Audubon reported the highest gust in Iowa at 88 mph. This storm also met the criteria for a ���derecho'', which makes it the first derecho on record in the month of December anywhere in the United States. Finally, we had an unofficial gust of 108 mph recorded by a mesonet station near Sheffield, Iowa associated with one of the tornadic circulations. ||Environmental Wind: After the line of storms had passed, numerous strong, non-thunderstorm wind gusts over 70 mph occurred overnight. The top three non-thunderstorm wind gusts were 83 mph in Decatur City, 81 mph in Marshalltown, and 80 mph in Johnston. The Des Moines International Airport recorded a 74 mph non-thunderstorm wind gust, which is the highest non-thunderstorm wind gust at this location since 1970.| |Temperatures: In addition to the severe weather and strong non-thunderstorm winds, the temperatures were remarkable and record setting. Numerous record daily highs were broken by many degrees. In addition and preliminarily, the all-time December record high temperature for Iowa of 74 degrees that was set in Thurman, IA on December 6, 1939 was broken with four sites reaching 75 degrees (Oskaloosa, Muscatine, Iowa City, and Ottumwa).||For detailed environmental analysis, including soundings, please view the various local NWS office event review pages: NWS Des Moines, NWS Sioux Falls, NWS Omaha, NWS Wichita, NWS Pueblo, NWS Twin Cities, NWS Quad Cities, NWS Hastings, NWS La Crosse, NWS Green Bay, or NWS Milwaukee.

This tornado moved through both Hardin and Franklin Counties. The tornado touched down in Hardin County north of Alden and moved quickly northeast. The tornado exited Hardin County into Franklin County near the intersection of Hardin Road and HH Avenue. The Hardin County segment was found and determined by using high resolution satellite imagery.

This tornado travelled through both Hardin and Franklin Counties. The tornado touched down about two miles south of Iowa Falls and passed on the southeast edges of the town. This produced some EF1 damage to buildings in the area. The tornado continued to the northeast and crossed into Franklin County near the intersection of Hardin Road and county highway S45.

This tornado moved into Franklin County from Hardin County. Much of the path through Franklin County was found using high resolution satellite imagery. However, the emergency manager did supply some damage points on the northeast end of the track to the northeast of Bradford, Iowa. The damage was to trees with tree trunks being snapped along several different roads. The tornado lifted a few miles west southwest of Geneva.

This tornado continued into Franklin County from Hardin County. This path was determined using high resolution satellite imagery. There was damage to trees and some outbuildings as the tornado moved northeast. The tornado lifted just south of Highway 3 near the Handorf Roadside Park.

This tornado produced EF1 damage on the east side of Sheffield nearly destroying a business outbuilding. The track farther to the southwest was found in high resolution satellite imagery and also confirmed through a private weather station which recorded a wind gust to 108 mph as the tornado passed its location.

This tornado began a few miles north of Geneva and moved northeast producing plenty of tree damage as well as extensive outbuilding damage on two farmsteads. Additional damage to a home with missing roofing and siding occurred along 170th Street west of Yarrow Avenue. The tornado continue producing tree and power pole damage to the northeast before lifting on the north side of 190th Street near the West Fork Wildlife Area.

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 19:26 UTC and running to 02:00 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 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.

NWS Des Moines, IA wrote its last area forecast discussion before the tornado touched down at Dec 15, 5:05 PM CST, 1 hour 22 minutes earlier.

Area Forecast Discussion
National Weather Service Des Moines IA
505 PM CST Wed Dec 15 2021

...Updated for the 00z Aviation Discussion...

.DISCUSSION.../Tonight through Wednesday/
Issued at 208 PM CST Wed Dec 15 2021

Key Messages:

An unprecedented, historic event is just getting started across the
area today. There are several facets to this event including extreme
environmental winds, high end severe weather, and (of least
importance) record breaking heat.

Lee cyclogenesis has rapidly increased as the surface cyclone moves
out of Colorado and into Nebraska and Kansas this afternoon. Iowa
has remained within the warm sector today with temperature
soaring into the upper 60s to mid 70s across the area. This
shatters high temperature records for the day across most sites in
Iowa. Additionally, the all-time, statewide December record high
of 74 degrees in Thurman of 74 on Dec. 6, 1939 is broken
(preliminarily, this will need to be officially verified).
Dewpoints at 1pm were in the upper 50s and low 60s statewide.

Significant High Wind...

Warm air advection ongoing today has initially limited mixing
efficiency as was expected, as the lift from waa works in contrast
to deep mixing. Even still, winds by noon had started gusting 40-50+
mph across parts of southern into central Iowa. Convection has begun
across Kansas and Nebraska and is expected to swing across Iowa
between 22z and 02z. Thunderstorms will enhance background wind
gusts, but more on the convective component next. Hi-res models
continue to indicate a brief lull in gusts behind the line of
convection this evening, however this will only last an hour or so
before the synoptic winds ramp up with vigor. As the low pressure
center and associated dryline approaches the area the pressure
gradient will tighten significantly across the area. Strong cold air
advection and subsidence will pull the very strong winds just off
the surface down to the ground. It can be practically guaranteed
that everyone will see 60 mph gust this evening and many will see 70
mph. Strong decent on the back of the low resulting in a sting
jet setup mean that gusts of 80+ mph are possible in pockets
across the state. Gusty winds will begin to subside after
midnight. Widespread wind damage an power outages are a real
possibility.

Severe Thunderstorm Threat...

This is the first time that SPC has ever issued a Moderate risk for
severe storms in the state of Iowa in December, and even in the
typical convective season they are fairly uncommon). Thunderstorms
will enhance the background strong environmental winds as cold
pools drive gusts. Embedded gusts within severe thunderstorms will
easily exceed 80 mph and gusts over 100 mph are certainly
possible. Wind gusts are easily a concern with every storm that
develops. The other concern is the tornado threat. Parameters
within the CAMs include 0- 1km MLCAPE ~800 J/kg, 0-1km helicity
~300m2/s2, LCLs ~500m, Sig Tor Parameter ~1-2, and 0-1km lapse
rates 6-8 C/km, all contributing to a good tornadic environment.
As the previous discussion mentioned, storms will be moving very
fast (current storms in Kansas are moving at 70-80 mph) and
rotational winds within tornadic storms will be enhanced, easily
pushing strength to the significant tornado (EF2+) thresholds.

Beyond today, much cooler air filters in behind the low with highs
in the 30s to low 40s through the end of the week. On saturday
highs in the 20s are likely as a secondary cold front pushes
across the area. The forecast through next week looks to remain
dry with temperatures moderating into the 30s and 40s.

&&

.AVIATION.../For the 00Z TAFS through 00Z Thursday evening/
Issued at 505 PM CST Wed Dec 15 2021

A line of thunderstorms has entered western Iowa with gusts of
80+ mph and a number of embedded tornadoes. This will will pass
across I-35 by 530pm and exit towards eastern Iowa after 7-8pm.
Wind gusts behind the storms will continue to gust 50-60 kts
through 06z. MVFR/IFR cigs will develop overnight.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until midnight CST tonight for IAZ023>025-
033>037-044>049-057>061-070>075-081>086-092>097.

High Wind Warning until 3 AM CST Thursday for IAZ004>007-015>017-
026>028-038-039-050-062.

&&

DISCUSSION...Hagenhoff
AVIATION...Hagenhoff

Hazardous Weather Outlook
National Weather Service Des Moines IA
225 PM CST Wed Dec 15 2021

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-162030-
Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo-
Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun-
Webster-Hamilton-Hardin-Grundy-Black Hawk-Crawford-Carroll-Greene-
Boone-Story-Marshall-Tama-Audubon-Guthrie-Dallas-Polk-Jasper-
Poweshiek-Cass-Adair-Madison-Warren-Marion-Mahaska-Adams-Union-
Clarke-Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne-
Appanoose-Davis-
225 PM CST Wed Dec 15 2021

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

A High Wind Warning is in effect for the area today and tonight.
Please refer to the National Weather Service website at
weather.gov/desmoines for further details.

Strong to severe thunderstorms are likely today and tonight,
including wind gusts in excess of 80 mph and a few tornadoes
possible.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter reports of wind speeds, damage, and other severe weather
would be appreciated.

CURTIS

In the hours before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
619 PM CST WED DEC 15 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0539 PM     TSTM WND DMG     GRAND JUNCTION          42.03N 94.24W
12/15/2021                   GREENE             IA   PUBLIC

            PUBLIC RELAYED SIDING MISSING ON HOUSE ON SE
            SIDE OF GRAND JUNCTION. TIME ESTIMATED FROM
            RADAR.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
620 PM CST WED DEC 15 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0619 PM     TSTM WND GST     2 N WINTERSET           41.36N 94.02W
12/15/2021  M68 MPH          MADISON            IA   MESONET

            MEASURED VIA CWOP.

&&

KLP

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
621 PM CST WED DEC 15 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0615 PM     TSTM WND GST     2 W ALGONA              43.08N 94.27W
12/15/2021  M62 MPH          KOSSUTH            IA   AWOS

&&

KLP

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
622 PM CST WED DEC 15 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0527 PM     TSTM WND GST     2 ENE LAMONI            40.63N 93.90W
12/15/2021  M60 MPH          DECATUR            IA   ASOS

            LAMONI MUNICIPAL AIRPORT RECORDED 52 KT WIND
            GUST.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
624 PM CST WED DEC 15 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0545 PM     TSTM WND DMG     2 ESE RUTHVEN           43.12N 94.86W
12/15/2021                   PALO ALTO          IA   LAW ENFORCEMENT

            HOG BUILDING COMPLETELY DESTROYED.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
626 PM CST WED DEC 15 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0548 PM     TSTM WND DMG     KNIERIM                 42.45N 94.45W
12/15/2021                   CALHOUN            IA   PUBLIC

            MACHINE SHED DAMAGED 1 MILE NORTH OF SOMERS
            AND STOP SIGNS/HIGHWAY SIGNS BLOWN OVER HWY
            20 AT KNIERIM.

&&

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.

Hampton (HPT), 13 km from the path, in the two hours either side.

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

The Des Moines radar (KDMX), 109 km away, was scanning. The volume nearest the touchdown began at 00:25 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.