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May 2004 Tornado Outbreak Sequence
Radar image of the supercell that spawned the Hallam, Nebraska, tornado.
Date of tornado outbreak: May 21-31, 2004
Duration1: 11 days
Maximum rated tornado2: F4 tornado
Tornadoes caused: 389
Damages: $175 million (USD) (May 22), $65 million (USD) (May 29-31)
Fatalities: 7
Areas affected: Ontariomarker, Midwest & Southern United States
1Time from first tornado to last tornado

2Most severe tornado damage; see

The May 2004 Tornado Outbreak Sequence was a series of tornado outbreaks that affected much of southern Ontariomarker, the Central and Southern United Statesmarker from east of the Rockies to the Mid-Atlantic States from May 21 to May 31, 2004. Particularly hard hit were the central Plains from Missourimarker to Iowamarker and the Ohio Valley. The Central Plains were hit by two significant outbreak on May 22 and May 24, the first outbreak which produced a very large and violent tornado in Hallam, Nebraskamarker. The Ohio Valley was affected by one of the largest tornado outbreaks ever during the Memorial Day weekend on May 29-30.

Seven people were killed in four states during the entire event. In total, 389 tornadoes were confirmed over an 11-day period and is similar in terms of number of tornadoes then the May 2003 tornado outbreak sequence which affected most of the same areas. However, the 2003 Outbreak Sequence produced several more destructive and violent tornadoes and had a much higher death toll than in May 2004.

Hallam Tornado Outbreak

The Hallam, Nebraska Tornado Outbreak was an outbreak of 56 tornadoes in several Midwestern U.S. states on the evening of May 22, 2004 and the first of a series of tornado events. Most of the tornadoes occurred in Nebraskamarker and Iowamarker. On that day, a warm, moist airmass was sitting over Nebraska while an upper level low developed in Colorado, with an attending dryline forming ahead of the advancing cold front. One person was killed in this outbreak, 38 were injured and there was $175 million in damage. The worst tornado was an F4 that struck Hallam, Nebraskamarker. It is this tornado that is thought to be the largest of all time, with the funnel stretching 2.5 miles wide in some places.


Tornado damage in Hallam
first tornado in this outbreak touched down at 1:15 MDT near La Grange, Wyomingmarker. It was an F0 and did not cause any significant damage. After another small tornado touched down in Coloradomarker, several tornadoes began to form in Nebraska and Iowa during the mid–afternoon hours where they continued until around 11:00 p.m CDT.

The most damaging tornado in the outbreak first touched down at 7:30 P.M. CDT in northwestern Jefferson Countymarker. The tornado then moved to the northeast, through southern Saline Countymarker and northwestern Gage Countymarker. By the time it entered Lancaster Countymarker, it measured an F4 on the Fujita scale and the damage was 2.5 miles (4 km) wide. The tornado passed into Otoe Countymarker, disappearing just west of Palmyramarker at 9:10. The tornado had a path length of about 54 miles, and was on the ground for 100 minutes.

Widest tornado ever?

Path of the Hallam tornado.
2.5 miles (4 km) wide as it passed through Hallam (25 miles (40 km) south of Lincolnmarker), there are some claims that this tornado was the widest tornado ever recorded.


More damage in Hallam
The village of Hallam, struck at 8:33 p.m., was the hardest hit. Approximately 95% of the buildings in Hallam were damaged or destroyed. There were 37 people injured and one fatality in the village. The Norris School District 160 high school building was severely damaged; its auditorium was destroyed. Straight-line winds caused damage in Princeton. Several farms and rural homes also suffered extensive damage. This storm not only derailed a freight train, but moved it 20 feet to the east.

Other significant damage occurred from an F2 tornado in Adamsmarker and Claymarker counties, Nebraska. Fifteen homes were damaged and another train was overturned, resulting in $5.5 million in damages.

Memorial Weekend Outbreak

The Memorial Day Weekend 2004 Tornado Outbreak was a significant widespread tornado outbreak lasted for two days from May 2930, 2004 with the final tornadoes occurring during the early morning hours of May 31. This tornado outbreak began in the Great Plainsmarker and continued throughout the Midwest. Activity on the 29th was limited from the Dakotasmarker to Oklahomamarker while activity shifted towards the Mississippi, Ohio and Tennessee Valleys on the 30th before ending across the Southeast early the following day.

The Storm Prediction Center had 199 tornado reports from the two days, but according to Storm Data archives from the NOAA, 168 tornadoes have been confirmed.

The 168 tornadoes occurred in 32 hours of continuous activity, which would not break the record held by the 1974 Super Outbreak, which saw 148 tornadoes in 18 hours. There was also a greater number of large and violent tornadoes in the Super Outbreak event. Most of the tornadoes were produced by supercells, though a few were produced by the following squall line. There were also widespread wind damage reports from a large squall line that moved through after the tornadoes. Damage totals from this outbreak are at $62.321 million.

The tornado outbreak killed at least 5 people across two states including 4 in Missourimarker and 1 in Indianamarker. 3 of the fatalities were caused by an F4 tornado that struck the Weatherbymarker area in DeKalb County, Missourimarker late during the evening of May 29. Another person was killed in the St. Louismarker Metropolitan area while the fifth fatality was northwest of Louisville, Kentuckymarker in the Marengomarker area where 80% of the town was damaged or destroyed.

In addition, an F2 tornado on May 30 affected portions of the Indianapolismarker Metropolitan Area on the same day the Indianapolis 500marker was taking place. The tornado missed the Indianapolis Motor Speedwaymarker by six miles and forced post-racing events to be held indoors. The tornado did however caused extensive damage across southern and eastern Marion Countymarker south of the downtown area. While 26 people were injured, over 700 structures were damaged by the storm.

Other outbreaks

Outbreak death toll
State Total County County

Illinoismarker 1 Scottmarker 1
Indianamarker 1 Crawfordmarker 1
Missourimarker 4 De Kalbmarker 3
St. Louismarker 1
Nebraskamarker 1 Lancastermarker 1
Totals 7
All deaths were tornado-related
Several other smaller tornado outbreaks took place between May 21 to May 31, 2004 and affected many of the regions impacted by the two main outbreaks. On May 21, a series of tornadoes hit Iowa causing major damage to the town of Bradgatemarker where 75% of the buildings were either damaged or destroyed.On this day, several clusters of thunderstorms traveled from the Midwest to the Mid-Atlantic States producing widespread damaging wind and weaker tornadoes across Michiganmarker.

On May 24, several tornadoes touched down across the Great Plains and the Mid-Mississippi Valley. Most tornadoes were weak although one person was killed in Illinois inside a mobile home.

On May 26-27, several tornadoes affected portions of the Ohio Valley. One tornado north of Louisvillemarker producing significant damage in Washingtonmarker and Clark Countiesmarker. An F3 tornado tore through a residential subdivision just north of Lexington, Kentuckymarker causing major damage to about 50 homes.

Confirmed Tornadoes (Entire Outbreak Sequence)

See also


  1. NCDC Storm Events-Select State
  2. Storm Prediction Center Storm Reports

External links

May 22

May 24

May 29-31

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