The List of the Strongest Tornadoes Ever Recorded: Part II

During the 2008 Super Tuesday outbreak, one of the longest tracked tornadoes in history ripped through primarily rural forestland in central Arkansas. Near the small community of Zion, the tornado hurled a Hummer a quarter mile from an obliterated residence. Another vehicle in the same area was mangled beyond recognition and wrapped around a denuded tree. The tornado does not appear on the

During the 2008 Super Tuesday outbreak, one of the longest tracked tornadoes in history ripped through primarily rural forestland in central Arkansas. Near the small community of Zion, the tornado hurled a Hummer a quarter mile from an obliterated residence. Another vehicle in the same area was mangled beyond recognition and wrapped around a denuded tree. Whether the tornado was capable of causing EF5 damage will never be known since the storm, like most, reached peak intensity in unpopulated areas. (Images by wxmandan)

□ For a tornado to be considered for categorization, it must have caused at least one fatality, and it must have occurred after the conception of the Fujita Scale in 1970. Damage intensity and, to a lesser extent, wind duration are the only variables considered, without regard to total path length, width or monetary loss. Information has only been taken from damage photographs or reliable survey reports, not unverified statements or accounts. While far from definitive, this list is the result of literally hundreds of hours of research, e-mails across the country and conversations with other storm chasers. I believe it is as accurate a list as is available. It is flexible and always open to change.

The indefinitive list of the strongest tornadoes:

1. Jarrell, Texas – May 27, 1997

2. Smithville, Mississippi – April 27, 2011

3. Kemper County (Philadelphia), Mississippi – April 27, 2011 

4. Bridge Creek, Oklahoma – May 3, 1999    

5. Bakersfield Valley, Texas – June 1, 1990 

6. Phil Campbell, Alabama – April 27, 2011

7. El Reno, Oklahoma – May 24th, 2011

8. Smithfield, Alabama – April 4, 1977    

9. Brandenburg, Kentucky – April 3, 1974 

10. Andover, Kansas – April 26, 1991

11. New Hartford (Parkersburg), Iowa – May 25, 2008

12. Joplin, Missouri – May 22, 2011

13. Guin, Alabama – April 3, 1974 

14. Moore, Oklahoma – May 20, 2013

15. Mulhall, Oklahoma – May 3, 1999

16. Wheatland, Pennsylvania – May 31, 1985

17. Rainsville, Alabama – April 27, 2011

18. Barneveld, Wisconsin – June 8, 1984

19. Will County (Plainfield), Illinois – August 28, 1990

20. Xenia, Ohio – April 3, 1974

Various images of tornado damage, with relative intensity increasing from left to right. At left, the 2011 Phil Campbell tornado left most trees partially debarked and stripped of branches. The ground also shows high velocity impact marks but no obvious scouring of grass (Image by John Phillips). At center left, impact marks and partial ground scouring in after the 2011 Smithville tornado. At center right, the near complete debarking of all foliage in Smithville (Images by C. Welch). At right, completely obliterated vegetation and severe ground scouring following the 2011 El Reno tornado. (Image by Jim LaDue).

Various images of tornado damage with relative intensity increasing from left to right. At left, the 2011 Phil Campbell tornado left most trees partially debarked and stripped of branches. The ground also shows high velocity impact marks but no obvious grass scouring (Image by John Phillips). At center left, impact marks and partial ground scouring after the 2011 Smithville tornado. At center right, the near complete debarking of all foliage in Smithville (Images by C. Welch). At right, completely obliterated vegetation and severe ground scouring following the 2011 El Reno tornado. (Image by Jim LaDue).

10. Andover, Kansas – April 26, 1991

From the steps of the Terradyne Country Club, Earl Evans captured the exact moment the F5 tornado entered the Golden Spur mobile home park. Just southwest of the park, large homes (similar to the ones in the foreground) were swept cleanly away.

□ One of the most well-known tornadoes in United States history touched down near Clearwater, Kansas, at the height of a severe weather outbreak on April 26th, 1991. Storm chasers filmed the tornado as it slowly gained strength and took aim on the southern suburbs of Wichita. After ripping through homes in Hayesville, the “elephant trunk” funnel steered towards McConnell Air Force Base, where thousands of post-Gulf War military personnel and their families were being housed. As the tornado entered the southern edge of the base, the power failed and the sirens across the area fell silent. The tornado filled with debris and entered a period of rapid intensification as it crossed the southern edge of the base’s runway. Four people were killed in a residential area east of the base, all of them caught out in the open while running for shelter (Grazulis, 2001).

After exiting Wichita, the tornado reached F5 intensity and expanded to a quarter mile in width. The small town of Andover, which hugs the Kansas Turnpike ten miles east of downtown Wichita, was impacted directly by the tornado at maximum intensity. Large, two-story homes to the east of 159th Street were swept completely away as the tornado approached the Golden Spur mobile home park. Most of the community’s residents were sheltering in a large, underground storm cave when the tornado obliterated the park, but some people failed to make it to shelter on time. More than 80% of the mobile homes in the park were turned to splinters by the F5 tornado and 11 people were killed. Adjacent to the park, a couple and their teenage son stopped their car and sought shelter in a ditch along Andover Road. The man and his son were killed in the unforgivable blizzard of debris from hundreds of disintegrating mobile homes, and the woman was seriously injured (Grazulis, 2001). Aerial damage surveys later documented a trail of empty foundations and scoured grass through the housing developments of Andover. Ground crews photographed mobile home frames wrapped around completely debarked trees in the Golden Spur community.

Video of the Andover tornado shows some of the most violent tornadic rotation ever filmed. Even so, there may have been an even stronger tornado during the outbreak.The longest tracked tornado on April 26th, 1991, roared through the unpopulated Oklahoma countryside and was undoubtably capable of producing F5 damage. The “Red Rock” tornado caused no fatalities, however, so was not considered for the “strongest” list.

Damage from the Andover tornado in the vicinity of the Golden Spur mobile home park (at right). Grass scouring is clearly visible in the swath of extreme damage. As the tornado crossed Andover Road, it left perhaps the most impressive instance of wind rowing ever photographed. The debris originated from a subdivision of large homes that was obliterated. (Image by Fernando Salazar)

Surveyors photographed a vehicle that had been carried almost a mile from the Golden Spur mobile home park. It was so thoroughly mangled that they were unable to determine whether it was a truck or a car. (Grazulis, 1993)

Several views of F5 damage in the vicinity of Chapel Drive, where large two-story homes were swept completely away.[

Several views of F5 damage in the vicinity of Chapel Drive, where large two-story homes were swept completely away.[

The remains of two large, well-built homes that were swept away in F5 fashion near 143rd Street. Circular ground scouring is visible in the lefthand image. Despite the severity of the damage, there were no fatalities in frame homes. Extensive warning and clear visibility gave residents more than 30 minutes to seek shelter underground. Also, the area was much less developed in 1991 than it is today. (Image from TVCII)

9. Brandenburg, Kentucky – April 3, 1974

Before and after views of Brandenburg. Perched on the corner of the ridge overlooking the Ohio River was “one of the nicest modern houses in Brandenburg” (visible in the before image at right center). The home was swept completely away in the tornado, killing the occupants. Green Street (the third street from the edge of the bluff) was the location of more than half of the tornado’s fatalities. (Meade County Heritage)

□ During the 1974 Super Outbreak, a tornado of incredible ferocity touched down in the hills of Northern Kentucky, a region unaccustomed to violent tornadoes. The storm intensified as it passed through unpopulated areas north of Hardinsburg, and began causing F5 damage as it approached the Indiana border. Several well-constructed homes were swept completely away along Highway 1239 as the violent tornado turned to the northeast at 50mph. Witness statements suggest that the tornado took on a “stovepipe” appearance and was fairly difficult to distinguish from the rain falling around it.

Few people were aware of the danger in Brandenburg, a small community on the Ohio River. A local disc jockey on the edge of town saw the tornado approaching and sent out a frantic last-minute warning to the residents of Meade County. For many of those not listening to their radios, the first warning was the roar of the tornado. One survivor later said that she “heard a noise that sounded like the world was coming to an end.” The fast-moving tornado ripped through the tiny town in less than 30 seconds. The worst damage occurred to homes on a bluff just west of Brandenburg’s business district. The nine homes that lined Green Street were obliterated, leading to 18 fatalities (Meade County Heritage). Several large, well-built two-story homes were left as bare concrete slabs, including a recently constructed home where four people were killed. One body was blown several hundred yards and found near the banks of the Ohio River at the base of the bluff. Additionally, trees were debarked and sheared just above ground level, and a news photographer documented extensive grass scouring just west of town (Macy, 1974).

Over the years, some of the more infamous tornadoes during the ’74 Super Outbreak have acquired almost mythical status. Damage photographs and first-hand reports, however, suggest that the lesser known Brandenburg tornado was perhaps the most powerful of the outbreak.

Just west of Brandenburg, a home was swept completely away, leaving nothing but an empty basement plastered in mud. The fatality rate in Brandenburg was the highest of any town affected during the 1974 Super Outbreak. A total of 27 residents were killed in the town of Brandenburg, where basements are commonplace. By contrast, 20 deaths occurred in the town of Guin, Alabama, which had a slightly larger population at the time. Additionally, the Guin tornado moved in excess of 70mph and impacted the town after dark, two variables that dramatically increase the likelihood of fatalities. (Data collected by Scott Koerner)

Two views of severe damage southwest of Brandenburg. At left, the collapsed basement walls of a home that was swept away. At right, view of mangled cars that were thrown long distances into a field that was partially scoured of grass. (Images by Donald Macy)

Close view of the

Close view of the “modern house” that was swept away above Main Street, resulting in two fatalities. Low-lying shrubbery was stripped bare, an indication of extreme surface winds. (NWS Louisville)

8. Smithfield, Alabama – April 4, 1977

Aerial view of F5 damage to large homes on Belmont Lane. The powerful tornado skirted just north of the highly populated core of Birmingham.

□ Birmingham, Alabama, was struck by an exceptionally violent tornado during a stormy spring day in 1977. Like most deadly tornadoes in the South, the Smithfield tornado was fast moving and difficult to see behind a curtain of heavy rain. The storm touched down west of downtown Birmingham and rapidly strengthened as it sped to the northeast. Four died, including a mother and her two children, as the tornado ripped through Smithfield Estates, a small neighborhood just east of North Pratt. Homes in the area were swept completely away and at least one vehicle were thrown more than 200 yards.

The tornado intensified further as it ripped through a forested area and approached Smithfield Manor, an upper middle class street lined with large two-story homes. Some victims in the neighborhood had heeded warnings and taken shelter in basements but others were caught unexpectedly by the F5 tornado. There were multiple fatalities in several families as an entire row of homes on Belmont Lane was obliterated, leaving nothing but clean foundations and empty basements. Photographic evidence indicates that the tornado scoured patches of grass from the ground and stripped trees bare of bark and branches. In total, 22 people were killed by the tornado, and more than 100 homes were completely destroyed. The death toll was remarkably low considering the severity of the building damage, which was some of the most intense ever photographed at the time.

Prof. Fujita, who was in Alabama at the time, gave the tornado an F5 rating. One piece of NWS literature reports that Fujita “toyed with the idea of rating the Smithfield tornado an F6.” Decades later, the 2011 Tuscaloosa/Birmingham tornado passed directly over some of the exact same areas affected by the 1977 event, causing damage to the same properties.

Extreme damage from the Smithfield tornado. At left, the sharp boundary between F5 damage and homes with only minor damage is evident. Most of the well-built homes destroyed in the tornado had basements, likely reducing the death toll. The body of one victim was reportedly carried over half a mile.

The remains of a brick home in Smithfield. Pine trees in the background have been reduced to featureless trunks.

7. El Reno, Oklahoma – May 25, 2011

View of the EF5 tornado minutes after touchdown. The tornado spent approximately 100 minutes on the ground and travelled nearly 70 miles, an exceptional distance for the Great Plains. (Image from JeopardyTempest / Youtube)

□ Twelve years after the Bridge Creek event, a tornado of equal ferocity passed within 20 miles of downtown Oklahoma City. The monster storm was tracked by rapid scanning mobile doppler radar as it touched down near the I-40 and rapidly intensified. Researchers recorded a doppler velocity of 280mph moments before the rain-wrapped tornado fell out of range and plowed to the northeast. As of this writing, the figure has yet to be officially released. Vegetation was ripped from the ground in the EF5 damage swath, and the few trees left standing were completely stripped of bark and branches. Three fatalities occurred in two vehicles as the tornado crossed the I-40. The victims’ bodies were left “unrecognizable” and discovered stripped of clothing a quarter mile from the freeway (AP, 2011). Rescue crews were unable to determine if the victims had exited their vehicles and attempted to take shelter on the ground.  The two cars were mangled so severely that only pieces of their frames were recovered. Additionally, an oil field adjacent to the I-40 was impacted directly by the EF5 tornado, resulting in the movement of a 1.9 million pound drilling derrick (Ortega, 2011). Reporters documented an oil tanker weighing in excess of 20,000lbs that was thrown a mile from the production site (KFOR, 2011). Aerial imagery revealed no visible ground impacts, so the tanker may have travelled the entire distance in one toss.

After passing to the north of El Reno, the tornado barreled eastward through the rural outskirts of Oklahoma City. A small cluster of homes near the town of Piedmont was directly impacted by the storm. Approximately a dozen homes were completely obliterated, and several residents were killed. More than a dozen large vehicles from the neighborhood were hurled several hundred yards into a field that was partially scoured of vegetation. The tornado continued to the east-northeast for an additional 35 miles but failed to impact any populated areas. Most of the damage and all of the fatalities occurred in the first 30 miles of the damage track.

A mesonet station near El Reno recorded a wind gust of 151mph in the outer fringes of the tornado’s circulation. The wind gust, which falls in the EF3 range, provides some indication that the Enhanced Fujita Scale grossly underestimates wind speeds in violent tornadoes. Ground scouring in the El Reno tornado was similar to the Bridge Creek tornado, and its path length was significantly longer. The Bridge Creek tornado paralleled the I-44 and was closely followed by radar for much of its life. The El Reno tornado was analyzed only briefly as it crossed the I-40, so higher winds may have occurred.

The remains of car hurled a half mile in Piedmont. Vegetation and vehicle damage of this severity are indicators of incredible intensity. (Image by Jim LaDue)

Severe vehicle damage and grass scouring near a neighborhood in Piedmont, where several fatalities occurred. (Image by Rebecca Manney)

Aerial views of the oil tanker that was thrown a mile from a production site on the other side of the I-40. Several other tankers were hurled long distances, and machinery in excess of 1 million pounds was moved.

Aerial views of an oil tanker that was thrown a mile from a production site on the other side of the I-40. Several other tankers were hurled long distances, and machinery in excess of 1 million pounds was moved.

View of severe ground scouring southwest of Piedmont.

On the same day as the El Reno tornado, two other tornadoes were likely capable of causing EF5 damage. One tornado in Chickasha scoured grass from the ground, swept away atleast one well-built home and ripped pavement from roads (at left). Nearby, a tornado in Goldsby left several large homes as bare foundations and caused pronounced grass scouring (at right).

On the same day as the El Reno event, two other violent tornadoes developed south of Oklahoma City. One tornado in Chickasha scoured grass from the ground, swept away atleast one well-built home and ripped pavement from roads (visible at left). Nearby, a tornado in Goldsby left several large homes as bare foundations and caused pronounced grass scouring (at right). Both tornadoes were likely capable of causing EF5 damage and may deserve a place on the “strongest” list.

6. Hackleburg/Phil Campbell, Alabama – April 27, 2011

View of the catastrophic tornado near the town of Phil Campbell. The storm maintained peak intensity for an exceptionally long period of time - the swath of EF5 damage was longer than the entire track of all the other EF5 tornadoes on April 27, 2011. (Video still by lookalika maan)

View of the catastrophic tornado near the town of Phil Campbell. The storm maintained peak intensity for an exceptionally long period of time – the swath of EF5 damage was longer than the entire track of all the other EF5 tornadoes on April 27, 2011. (Video link)

□ One of the most notable tornadoes in modern history touched down in a forested area near the town of Detroit, Alabama. After spending 15 minutes tearing through sparsely populated sections of Marion County, the fast moving storm ripped through the tiny town of Hackleburg at EF5 intensity, causing 18 fatalities. Buildings across most of the town were damaged, but the worst destruction was confined to a streak only 200 yards wide. In the worst affected areas, trees were completely debarked, well-constructed homes were swept from their foundations and a large manufacturing plant was reduced to a pile of twisted metal (NWS, 2011).

The tornado’s intensity remained remarkably uniform as it exited town and sped to the northeast at more than 70mph. Five minutes later, the storm reached the town of Phil Campbell, a small community with just over 1,000 residents. The town’s population was well-warned of the approaching storm, but interior rooms provided no protection from the exceptionally violent tornado. Twenty six people were killed in Phil Campbell, including four members of one family. Photographic evidence indicates the tornado scoured grass from exposed hillsides, and surveyors documented a large section of pavement that was peeled from a street on the eastern edge of town. Additionally, aerial imagery suggests that the roof of an underground storm cellar was ripped from the ground near Highway 237.

A post-storm damage survey by the NWS indicated that the most intense damage occurred in the unincorporated community of Oak Grove, about eight miles northeast of Phil Campbell. As the tornado roared through the area, a large, two-story brick home of excellent construction was swept completely away. The bodies of the home’s two occupants were found far from the empty foundation in a field to the east. Surveyors later determined that the EF0 damage contour reached a peak width in excess of one mile in Oak Grove, but the path of extreme damage remained narrow throughout the tornado’s life. In total, the storm travelled 132 miles – one of the longest officially measured damage paths in history. Surveyors documented EF5 and “near EF5” damage from Hackleburg to Tanner, a distance of nearly 70 miles. Despite hitting mostly unpopulated forestland and tiny towns, the tornado killed 72 people, most of whom were killed in a 25 mile swath between Hackleburg and Mount Hope.

The Phil Campbell tornado was one of the most impressive tornadic events of the past century. The storm’s intensity, rapid forward pace, huge size and exceptional path length have led many to consider it the “strongest tornado ever recorded.” Winds in the storm may have easily exceeded the Bridge Creek and El Reno events, but the storm’s fast movement reduced the duration of the most intense winds to less than five seconds. As a result, the tornado caused less pronounced ground and vegetation scouring than some other, slower-moving EF5 storms. A post dedicated specifically to this tornado can be found here.

Hackleburg was the first town directly impacted by the fast moving EF5 tornado. As the tornado entered town, a large church and several homes were reduced to empty concrete slabs. The few remaining bushes and trees in the inner damage swath were stripped bare and left clinging to the ground by only a few roots. High winds within the tornado’s large circulation affected all of the buildings visible in this photograph, including the green-roofed church at extreme upper left, which was destroyed. (Image from HBTV)

Three images of extreme damage in Hackleburg. At top left, view of large trees that were completely debarked near the Wrangler Factory (Image by Patrick Flanagan). At top right, a vehicle that was rendered unrecognizable in the vicinity of Clay Street (Image by John Phillips). At bottom, the tornado was powerful enough to scour concrete from the ground (Image by Niccolò Ubalducci). Considering the speed of the tornado and the width of the EF4 and EF5 damage contour, the most extreme destruction likely occurred in less than five seconds.

At left, extreme vegetation damage and possible ground scouring along a hillside on Pinion Drive in Phil Campbell. At right, a storm cellar 200 yards to the southwest of the left image appears to have lost its ground-level roof in the storm (Image by HGTV). The Hackleburg/Phil Campbell tornado caused some of the most violent wind damage ever documented.

At left, extreme vegetation damage and possible ground scouring on Pinion Drive in Phil Campbell (Image by Robin Conn). At right, a storm cellar (center) at the edge of Phil Campbell appeared to have lost its ground-level roof in the storm (Image from HBTV). Due to its strength and longevity, the Hackleburg/Phil Campbell tornado likely had the most destructive potential of any tornado in recent history.

Damaged grass marks the path of EF5 damage near County Road 81, one mile east of Phil Campbell. In the foreground, large trees that have been debarked and sheared just above ground level are visible. A few hundred yards to the east, a cluster of empty foundations is all that remains of several frame homes along Cornelius Drive, one of which was large and very well-constructed. Three people died in two of the obliterated homes, and a dozen vehicles were thrown more than 150 yards. Just beyond the small lake at top, another three people were killed in the complete destruction of two homes at the edge of a wooded area. (Image from HBTV)

__________

Certain damage indicators are unique to EF5 tornadoes. These include:

1. Pronounced ground and vegetation scouring (perhaps the best indicator of extreme intensity).

2. Completely debarked trees.

3. Well-constructed buildings swept from their foundations.

4. Vehicle’s thrown great distances and mangled beyond recognition.

5. Granulation of debris.

6. Incredible phenomena (eg. an 800lb safe thrown 200 yards in Rainsville, AL) and wind rowing.

7. High above-ground fatality rates in frame homes.

For reasons unknown, some intense tornadoes do not leave behind all seven damage indicators. Ground scouring, while strongly correlated with wind speed, occurs readily in some tornadoes and not others.

Damage in Oak Grove following the 2011 Phil Campbell tornado. Researchers at the NWS believed the tornado reached peak intensity in this area, and at far right a large, two-story brick home of excellent construction was swept completely away. There is no grass scouring near the home, however, whereas the 1999 Bridge Creek tornado scoured grass while at F4 intensity.

__________ Click to see:

Part I

Part III

Part IV

The Highest Winds Ever Measured by Mobile Doppler Radar in Five Violent Tornadoes

“In small, intense tornadoes, and especially in multiple vortices, radar observations of debris may be severely underestimating air motions.” – The Center for Severe Weather Research

Image of the violent Spencer, South Dakota, tornado of 1998. Winds over 260 mph were recorded as the tornado obliterated 100 homes and killed six people. (StormStock)

□ Mobile doppler radar remains the only quantitative and practical technology able to analyze tornadic winds. Direct observations in winds over 200mph are next to impossible, so doppler radar allows scientists the opportunity to – from a safe distance – see behind the curtain of dirt and debris. It is important to understand, however, that doppler devices do not actually “measure” anything. Instead, they analyze the motion of debris particles within tornadoes and provide a statistical range from which tornadic wind speeds can be estimated.

Despite over two decades of active use, only a handful of violent tornadoes have ever been documented at close range. Of the tornadoes that have been tracked, only a fraction of their total path lengths were thoroughly analyzed. So doppler velocities, while useful, are by no means an objective measurement that can be used to compare or categorize individual storms.

Image of the Bridge Creek tornado from the Doppler On Wheels (DOW) right as the record 300 mph+ velocity was recorded. The tornado was in the process of scouring grass and pavement from the ground in Grady County. Higher winds have undoubtedly occurred in other E/F5 tornadoes.

1. The highest reading ever recorded by mobile doppler radar was during the May 3rd, 1999, Great Plains tornado outbreak. The world-record velocity was taken just before 7pm as the F5 Bridge Creek tornado roared towards the Oklahoma City metro area. Originally calibrated at 318 mph, the reading was later reduced to 301 mph +/- 20 mph (135 +/- 10 m/s). A more accurate interpretation of the data is the statistical range the DOW estimated – 280 mph to 322 mph. At two standard deviations (2% likelihood) the measurement would be 369 mph, according to the DOW website. The reading was taken at a fairly low altitude (about 95 ft above the ground) but the surface level winds may have been slightly less – probably in the 260 to 290 mph range. At the same time, recent research in powerful hurricanes has shown that surface winds, which are generally estimated to be 10 to 15% lower than flight level winds, can actually be equal to or even exceed high altitude winds in exceptionally powerful, rapidly intensifying tropical cyclones (Uhlhorn, 2012). While these observations are specific to hurricanes, the same principle may apply to powerful tornadoes undergoing a period of rapid intensification.

The DOW does not directly measure winds but instead the movement of airborn particles. No attempt has ever been made to compare DOW observations with actual ground readings in violent tornadoes for obvious reasons. The DOW team admits that their technology likely fails to account for the many small-scale vortices that exist in strong tornadoes as well as the vertical component of tornadic winds.

The Bridge Creek tornado caused extreme ground scouring across the majority of its path. (Image by Bob Webster)

Image of the F5 tornado as analyzed by the DOW. Note the hurricane-like “eye” at center. Survivor testimony and scientific data indicates tornadoes, particularly large tornadoes, have calm centers with light winds.

2. Besides the Bridge Creek event, only one other E/F5 tornado has been analyzed by mobile doppler radar. The El Reno, Oklahoma, EF5 tornado formed on May 24th, 2011, during a large scale outbreak that also produced the deadly Joplin tornado two days earlier. The tornado killed nine people and left a streak of scoured earth as it thundered through rural areas west and north of Oklahoma City. Though still not officially made public, a rapid scanning mobile radar recorded a radial velocity of  280 mph (125 m/s) about 220 ft above ground level early in the tornado’s life. The tornado was given an EF5 rating based on the doppler measurement, and its intensity is currently quoted in NWS literature as having been “greater than 210mph” at ground level. The mobile radar team was only able to follow the tornado for part of its 65-mile long path, so it is very possible the tornado had higher winds in later stages of its life.

The El Reno tornado had a significantly longer path than the Bridge Creek tornado and may also have been more intense, though such comparison is purely speculation. The tornado became rain wrapped minutes after touching down and was obscured for much of its life. The fatality rate (the number of fatalities divided by the total number of people in the tornado’s path) in the El Reno/Piedmont tornado was significantly higher than the Bridge Creek tornado.

Severe tree and vehicle damage from the EF5 El Reno tornado. During the May 2011 tornado outbreak in Oklahoma, there were several other tornadoes that likely reached EF5 intensity. The Chickasha tornado formed one hour after the El Reno tornado and was well-documented by storm chasers. It scoured grass and pavement from the ground and likely had winds well into the EF5 range. (Image by Jim LaDue)

Video still of the El Reno tornado. For much of its life the EF5 tornado was a mile wide and obscurred by precipitation. (Image by JeopardyTempest)

3. The Red Rock, Oklahoma tornado on April 26th, 1991 was part of a larger outbreak that also caused the infamous Andover, Kansas F5 tornado. Of all the violent tornadoes that day, the Red Rock tornado was likely the most intense. It had the most impressive radar presentation and the longest damage path. The tornado hit very little as it roared through sparsely populated countryside and was only given an F4 rating as a result. A team headed by Howard Bluestein recorded a velocity of 268 mph in the tornado’s mature stage. This was the highest reading ever recorded using mobile doppler technology up until the Bridge Creek tornado eight years later. The Red Rock measurement was taken about 550 ft above the ground. Like most of the tornadoes tracked by mobile doppler radar, only a part of its life cycle was analyzed, and higher winds may have occurred in other stages of its development.

The Red Rock tornado was exceedingly violent, and video from storm chasers show it had some of the most impressive tornadic motion ever recorded.

View of the Red Rock tornado close to the time the 268 mph velocity was recorded.

4. The Spencer, South Dakota F4 tornado was followed by the DOW as it travelled generally to the east-southeast on May 30, 1998. The DOW recorded ground relative wind-speeds as high as 264 mph (118 m/s) close to the time the tornado passed through the small town of Spencer (Wurman, 2005). The measurement was taken at a fairly low altitude – 160 ft – but still well above what the NWS constitues as “ground level.” Only a tiny section of the tornado’s path crossed over man-made structures, so the tornado’s true damage potential was likely not realized. It was given an F4 rating after a damage survey was conducted, but many researchers believe the tornado had F5 potential. Six fatalities occurred in Spencer, five of them in a two story apartment building that was obliterated.

An interesting feature of the Spencer tornado was revealed when the DOW measurements were compared with a ground damage survey. The tornado was shown to have a pronounced eye, and much like a hurricane, the winds on the right side of the tornado were significantly stronger than the winds on the left side due to the addition of the tornado’s forward momentum (Wurman, 2005). The high-end F4 damage was all south of the torndo’s center whereas areas north of the eye had lighter (F1 – F2) damage. According to the DOW analysis, the worst affected areas in Spencer experienced hurricane force winds for two minutes and violent (200mph+) winds for about 20 seconds. The tornado was often obscurred by dust, but video from storm chasers show that the storm had extremely rapid rotation.

Aerial view of F4 damage in Spencer. The large building at right is where five deaths occurred.

5. The Mulhall, Oklahoma tornado occurred on the same day as the Bridge Creek tornado on May 3rd, 1999. Several researchers believe this tornado was more violent than its infamous cousin, and the DOW measurements revealed the Mulhall tornado was significantly larger. The DOW estimated a velocity of 257 mph (115 m/s) and one CSWR article mention readings of 277 mph to 299 mph in regards to this tornado. The veracity and context of the higher readings is unknown (DOW Measurements of Extreme Winds…, 2003). The Mulhall tornado’s extreme winds formed a giant circle one mile across with a large, calm eye at center. The tornado had hurricane force winds extending over an area four miles across, making it the largest tornado ever analyzed by the DOW. The tornado only caused two fatalities as it swept through largely rural areas north of Oklahoma City, but the storm had the potential to produce a huge swath of E/F4 to E/F5 damage had it struck a heavily populated area.

Image of the Mulhall tornado taken from the DOW. The tornado was rated F4, but had it passed over more structures it likely would have received an F5 rating.

Equal area comparison between the Mulhall and Bridge Creek tornadoes from cswr.org. The Mulhall tornado had similar but slightly weaker winds at the time of analysis but the size of the tornado was remarkable. The tornado’s core missed the center of Mulhall by nearly a mile but the broad region of winds caused severe damage across the town.

Measurements from mobile doppler radars taken before 2007 were often in agreement with the now unused Fujita Scale. Even when the estimates are reduced by 10 to 15% to account for possible altitude effects, the velocities were in agreement with the Fujita Scale. The DOW often found winds higher than the tornado’s damage indicated. Popular opinion now emphasizes being as conservative as possible when estimating tornado windspeeds. The new “Enhanced Fujita Scale” is more specific in its description of tornado damage indicators, but the reduced windspeed ranges likely underestimate the surface winds in violent tornadoes.