Tornadoes · United States · Iowa · 2024

EF1 tornado, Bethesda, Iowa, May 21, 2024

This EF1 tornado ran 3.3 miles across Page County on May 21, 2024, touching down at 7:32 AM CDT and reaching 80 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.

  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.

The record

Rating
EF1
Date
May 21, 2024
Touchdown
7:32 AM CDT (12:32 UTC)
Lifted
7:36 AM CDT (12:36 UTC)
On the ground
4 minutes
Path length
3.3 miles (5.3 km)
Path width
80 yards (73 m)
Deaths
0
Injuries
0
County
Page County
Touchdown point
40.799, -95.128
Lift-off point
40.825, -95.076
Record number
2405210632-01

The damage survey

97 damage points were recorded along this path by NWS DMX and NWS OAX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF2. The highest wind the damage implies is 130 mph.

  • Damage to hooped greenhouse, covers partially removed
  • Trunks of large trees snapped, with some shingles removed from old house a short distance away
  • Complete destruction of newly built machine shed.
  • Also damage to roofing of house

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

Troughing over the western CONUS brought southwesterly flow aloft over the central and northern Plains for the duration of this event. In the couple of days leading up to May 21st, the upper-level flow pattern amplified as a trough deepened over the northern Rockies. This trough then ejected out into the central Plains on the 21st. At the surface, a stationary front developed and stretched across central Nebraska and southern Iowa by the evening of the 19th. Elevated convection that morning north of the developing surface boundary resulted in isolated instances of severe hail and wind across southeast Nebraska. Additional scattered strong to severe thunderstorms developed along this frontal boundary as it slowly lifted north, with a 64 miles per hour wind gust measured in Lancaster County and golf ball sized hail falling in Clarinda Iowa.|A weak low-pressure system developed the morning of the 20th in response to a shortwave rounding the base of the main trough out west, resulting in a cold front that pushed southeast across South Dakota and central Nebraska that afternoon. This front, however, stalled out across eastern Nebraska and western Iowa that evening, remaining draped across the region that night and into the morning of the 21st. Numerous rounds of strong and severe thunderstorms that night brought widespread severe weather and flash flooding, primarily across east-central Nebraska and southwest Iowa, though some elevated supercells in northeast Nebraska brought small hail to the area. After 10 UTC, an intense line of severe thunderstorms moved across eastern Nebraska and western Iowa bringing wind gusts ranging from 60 to 95 miles per hour, in addition to several spin-up tornadoes. |As the primary upper level disturbance ejected out over the Great Plains, intense surface cyclogenesis was noted over eastern Nebraska. This resulted in the frontal boundary that had been draped across eastern Nebraska and western Iowa that night prior to be forced northward. By 18 UTC, a strong cold front pushed through southeast Nebraska and into Iowa that afternoon. Scattered supercell thunderstorms developed along this cold front and moved across southeast Nebraska and western Iowa. These supercells became tornadic after crossing the Missouri River into Iowa, with several long-track significant tornadoes being confirmed across the state. In the OAX CWA, the strongest tornado damage confirmed was that consistent of an EF-2 in Montgomery County. This tornado continued into the DMX CWA where it caused EF-3 damage. Another tornado developed in Page County shortly before 3 PM that afternoon. This tornado went on to produce EF-4 damage in the DMX CWA. All in all, over this three-day event, 10 tornadoes were confirmed across the OAX CWA.

A short-lived tornado developed near 1760th Street west of N avenue and moved east northeast. It damage trees and outbuildings, including substantial damage to one large barn. Peak winds in this tornado were estimated to be at 100 miles per hour. The max path width of this tornado was measured at 80 yards, with an average width estimated at 70 yards.

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

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, in the hatched area where significant tornadoes were expected. The outlook in force was issued at 05:54 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.

What forecasters said that day

The local office's own words before the tornado touched down, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Omaha, NE wrote its last area forecast discussion before the tornado touched down at May 21, 5:30 AM CDT, 2 hours 2 minutes earlier. Its key messages:

  • Continuing overnight convection will bring potential for severe weather this morning, primarily damaging winds and flash flooding.
  • Additional strong to severe thunderstorms with all hazards possible will move through the area in the 10 AM to 2 PM timeframe today.
  • There will be additional rain chances beginning Thursday night and lasting through this upcoming weekend.
Area forecast discussion, May 21, 5:30 AM CDT, 2 hours 2 minutes before
Area Forecast Discussion
National Weather Service Omaha/Valley NE
530 AM CDT Tue May 21 2024

.KEY MESSAGES...

- Continuing overnight convection will bring potential for
  severe weather this morning, primarily damaging winds and
  flash flooding.

- Additional strong to severe thunderstorms with all hazards
  possible will move through the area in the 10 AM to 2 PM
  timeframe today.

- There will be additional rain chances beginning Thursday night
  and lasting through this upcoming weekend.

&&

.DISCUSSION...
Issued at 205 AM CDT Tue May 21 2024

Short Range (Today)

A deep upper level trough moving into the central Plains has spun up
a surface low currently sitting in western Kansas. Overnight
convection in the area forced by a leading shortwave continues to
weaken through the overnight hours. This has brought a shift from a
severe weather threat to a hydrologic threat with storm training
along a frontal boundary draped across east central Nebraska
bringing flash flooding potential to the area. Nearly 2 inches of
rainfall has been reported for the Omaha area overnight.

An MCS has developed over southwest Nebraska/northeast CO and will
quickly accelerate eastward overnight. The features is expected to
push through the area in the 5:30 to 7:30 am period. CAM guidance is
suggesting a strong segment of bowing winds pushing through the area
in this timeframe. The strongest winds will likely be north of
Interstate 80 with the HRRR suggesting gusts of 60-70 mph in
portions of northeast Nebraska.

A lull in convection is expected in the 8 am to 11 am timeframe with
a few lingering showers possible. By the mid-morning, the
aforementioned surface low is expected to deepen and track
northeast into eastern Nebraska. Guidance has continued to slow
the progression of this low with consensus gained on the feature
reaching northeast NE by noon. This has prompted to SPC to
expand the moderate risk (level 4 out of 5) for severe weather
westward to include our southwestern Iowa counties. An
associated cold front will drape south of the low with
placement over eastern Nebraska by late morning. The airmass
ahead of the cold front is expected to quickly recover from the
overnight convection. By late morning, MLCAPE values of
2500-2800 J/kg are expected in southeast NE and southwest IA.
Bulk shear values are expected to exceed 70 kts in this area as
a 500-mb jet streak pushes into the region. Hodographs remain
long with increasingly impressive low level features as your
progress eastward into Iowa.

Convection initiation is expected along the front in eastern
Nebraska during the 10 AM to noon timeframe. An initial
supercellular storm mode is expected before storms move northeast
and take on upscale growth. All hazards will be possible including
large hail, strong winds and tornadoes. Flash flood potential is
possible through much of Tuesday, especially for areas that received
increased rainfall overnight. Storms will be quick to exit the area
this afternoon with much of the threat shifting east by 3 to 4 PM.
Additional lingering rain showers may continue into the
early evening.

Long Range (Wednesday through Monday)

By Wednesday, the aforementioned low pressure system is expected to
depart towards the Great Lakes region. Dry conditions are expected
with sunny skies and highs in the upper 70s. A shortwave trough
ejecting through the northern Plains will bring a chance for
rainfall Thursday night into Friday morning (PoPs 50-70%). Severe
weather potential is low with this event. An additional shortwave
feature moving across the Plains this weekend will bring additional
rainfall potential Saturday night through Sunday. PoPs remain low at
this time (20-40%). In this extended time frame, severe weather
potential looks to remain south of the area with this event.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 521 AM CDT Tue May 21 2024

Showers and thunderstorms are ongoing this morning. A round of
strong to severe thunderstorms will move through the terminals
in the 10-13Z timeframe. MVFR ceilings are spreading across
northeast Nebraska, reaching KOFK and KLNK with the possibility
of decreasing to IFR. Winds this morning are split between
southerly at KLNK with a shift to northwesterly as you progress
north towards KOMA and KLNK. Thunderstorm outflow is bringing
strong winds with gusts up to 45 kts possible.

A lull in convective activity will be in the 13-16Z timeframe.
Another round of strong to severe thunderstorms will move
through 16-19Z timeframe with trailing rain showers possible
into the late afternoon. Confidence is highest in these storms
reaching KOMA. Ceilings will begin to return to VFR in the
21-00Z timeframe. Winds will shift clockwise to northwesterly
across the area this afternoon with strong gusts up to 30-35 kts
possible through the afternoon.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Flood Watch through this evening for NEZ015-033-034-042>045-
     050>053-065>068-078.
IA...Flood Watch through this evening for IAZ043-055-056-069-079-
     080-090-091.

&&

DISCUSSION...Wood
AVIATION...Wood
Hazardous weather outlook, May 21, 4:19 AM CDT, 3 hours 13 minutes before
Hazardous Weather Outlook
National Weather Service Omaha/Valley NE
419 AM CDT Tue May 21 2024

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-212330-
Monona-Harrison-Shelby-Pottawattamie-Mills-Montgomery-Fremont-
Page-Knox-Cedar-Thurston-Antelope-Pierce-Wayne-Boone-Madison-
Stanton-Cuming-Burt-Platte-Colfax-Dodge-Washington-Butler-
Saunders-Douglas-Sarpy-Seward-Lancaster-Cass-Otoe-Saline-
Jefferson-Gage-Johnson-Nemaha-Pawnee-Richardson-
419 AM CDT Tue May 21 2024

This Hazardous Weather Outlook is for portions of southwest
Iowa...west central Iowa...east central Nebraska...northeast
Nebraska and southeast Nebraska.

.DAY ONE...Today and Tonight

Severe storms are possible this morning into the early afternoon.
Large hail, damaging wind gusts and flash flooding are the main
hazards. Tornadoes are possible.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation might be required on Tuesday afternoon.

In the hours before

Local storm report, May 21, 6:54 AM CDT, 38 minutes before
Preliminary Local Storm Report
National Weather Service Omaha/Valley NE
654 AM CDT Tue May 21 2024

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

0654 AM     Rain             Bennington              41.36N 96.15W
05/21/2024  M6.17 Inch       Douglas            NE   NWS Employee

&&
Local storm report, May 21, 7:02 AM CDT, 30 minutes before
Preliminary Local Storm Report
National Weather Service Omaha/Valley NE
702 AM CDT Tue May 21 2024

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

0702 AM     Flash Flood      1 NNW Mead              41.25N 96.50W
05/21/2024                   Saunders           NE   NWS Employee

            Water flowing over Highway 77.

&&
Local storm report, May 21, 7:08 AM CDT, 24 minutes before
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The surface observations

Clarinda (ICL), 12 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
00:00 UTC

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

The radar

The Omaha radar (KOAX), 120 km away, was scanning. The volume nearest the touchdown began at 12:32 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.

This ground now

The live radar over the trackEvery 2024 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

The other tornadoes of May 21, 2024

42 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
May 214:54 AM CDTEF0Polk, NE4.175$1.0 million
May 215:14 AM CDTEF0Colfax, NE0.550
May 215:23 AM CDTEF0Butler, NE0.650
May 215:27 AM CDTEF0Butler, NE2.650
May 215:45 AM CDTEF0Saunders, NE0.450
May 217:10 AM CDTEF0Montgomery, IA0.740
May 2112:52 PM CDTEF0Saunders, NE0.250
May 212:30 PM CDTEF1Buena Vista, IA1.675
May 212:35 PM CDTEF1Montgomery, IA2.970
May 212:43 PM CDTEF3Page, IA33.91,300$1.0 million
May 212:57 PM CDTEF1Page, IA1.785
May 212:59 PM CDTEF4Greenfield tornado, IA40.61,600535$32 million
May 213:09 PM CDTEF0Audubon, IA7.2100$10,000
May 213:18 PM CDTEF1Adams, IA12.7200$101,000
May 213:39 PM CDTEF2Adair, IA14.6200$750,000
May 213:48 PM CDTEF0Martin, MN2.375
May 213:50 PM CDTEF0Union, IA4.075$20,000
May 214:25 PM CDTEF0Warren, IA1.040$30,000
May 214:28 PM CDTEF0Warren, IA2.075$10,000
May 214:30 PM CDTEF2Polk, IA40.81,0004$8.4 million
May 215:25 PM CDTEF0Henry, MO0.350
May 215:27 PM CDTEF1Rogers, OK5.3500$100,000
May 215:39 PM CDTEF1Rogers, OK1.0100$10,000
May 215:41 PM CDTEF0Goodhue, MN0.725
May 216:01 PM CDTEF1Winona, MN to WI19.7110$320,000
May 216:14 PM CDTEF1Buffalo, WI3.9100$80,000
May 216:17 PM CDTEF1Buffalo, WI2.745$126,000
May 216:34 PM CDTEF1Trempealeau, WI0.8150$79,000
May 216:56 PM CDTEF1Eau Claire, WI9.5440
May 216:59 PM CDTEF1Jackson, WI3.175
May 217:08 PM CDTEF1Clark, WI7.0300$140,000
May 217:20 PM CDTEF1Clark, WI9.1120$88,000
May 217:27 PM CDTEF1Clark, WI4.0150$270,000
May 217:29 PM CDTEF1Clark, WI2.275$70,000
May 217:33 PM CDTEF0Clark, WI1.475$33,000
May 217:34 PM CDTEF1Clark, WI4.0110$345,000
May 217:47 PM CDTEF1Marathon, WI2.160
May 217:49 PM CDTEF1Dane, WI4.675$1.1 million
May 217:51 PM CDTEF1Marathon, WI2.180
May 217:59 PM CDTEF1Marquette, WI5.360$60,000
May 218:58 PM CDTEF1Outagamie, WI2.780
May 2110:32 PM CDTEF1Door, WI2.350

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.