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The May 3, 1999 Tornado Outbreak (1 Viewer)


Messages
399
Location
Niagara Falls, Ontario
Today is the 20 year anniversary of what was probably the closest we'll ever get to the textbook tornado outbreak. There were 71 confirmed tornadoes, including many photogenic and beautiful ones, but also one of the most catastrophic tornadoes in recent history. This outbreak was also important because it was a wake-up call for thousands of people (another reminder that tornadoes can and do hit large cities), and disproved the myth that overpasses are safe places to shelter.

The day had about as classic of a setup as you can get. The weather over most of Oklahoma in the morning was overcast and muggy, with temperatures around 65 to 68 degrees and dew points of 60 and higher. Cloud cover broke ahead of the dry line at about 10:30 am Central Time and sunshine broke through. CAPE values were in the realm of 6,000 J/kg in the late afternoon, and strong directional wind shear was present. The first supercells of the day developed around 3:30 pm over northwest and north-central Texas and soon tracked into Oklahoma.



The first major tornado of the day touched down at 5:20 pm Central Time in Caddo County to the east of Apache and tracked to the north towards Anadarko, where it collapsed the top floor of a house and knocked down first-floor exterior walls. Storm chasers following the Anadarko area tornado captured one of the most famous tornado pictures ever taken (below). The tornado dissipated near Stecker after remaining on the ground for six miles, and was rated F3. The Anadarko tornado was quickly followed by another F3 tornado that touched down to the north of Cement and tracked to the east for around three miles before shifting to a more northeastward path for another six miles, dissipating to the west-northwest of Chickasha. Two houses were mostly demolished by this tornado, with only a couple of interior walls left standing, and wooden power poles were snapped.



At 6:23 pm, the parent supercell of the Anadarko and Verden tornadoes produced one of the most infamous and destructive tornadoes in recent history, which touched down in Grady County to the south-southwest of Amber. The tornado caused light damage over the first several miles of its path, but explosively intensified to F4 strength to the north of Amber, and gradually approached F5 intensity as it closed in on the tiny town of Bridge Creek. Tracking directly through the town, the mile-wide tornado reached peak strength, completely sweeping away well-constructed and anchor-bolted frame homes and reducing mobile homes to splinters. The tornado caused extreme vegetation damage in Bridge Creek, debarking trees and low-growing shrubs, and scouring grass along with up to eight inches of soil from the ground. Additionally, a number of cars and trucks were tossed hundreds of yards and severely mangled, including a pickup truck that was found crumpled like a ball of tissue paper and wrapped around a bent utility pole. As the tornado continued towards the McClain County line, asphalt was scoured from a highway. 12 people were killed in Bridge Creek, by far the highest concentration of fatalities along the tornado's path. It was in this area that the highest wind speeds ever recorded on Earth, 301 ± 20 mph, were recorded by a Doppler on Wheels (DOW) team headed by Joshua Wurman. These winds were tied by peak gusts in the infamous El Reno tornado twelve years later, but have never been surpassed.

1628

The tornado narrowed slightly but remained violent as it tracked through McClain County. Crossing a bend in Interstate 44, the tornado tracked over an overpass at F4 strength, where a woman sheltering underneath with her son was blown out by the force of the tornadic winds and killed. Several others sheltering under the overpass were injured as well. As the tornado moved into Cleveland County, it briefly weakened to F2 strength before quickly re-strengthening to F4 intensity, then reaching F5 strength as it tracked through the city of Moore. Several well-built houses were completely swept away, with debris wind-rowed across city blocks and finely granulated, and a two-story brick apartment building was leveled. Trees were again completely debarked and stripped of their branches, a freight car was bounced for three-quarters of a mile, and an airplane wing originating in Grady County was found in the Country Place Estates subdivision of Moore. The tornado tracked into Oklahoma County, affecting southern Oklahoma City and Del City, but damage was considerably lighter (mainly in the F3 to low-end F4 range). The tornado dissipated outside of Midwest City at 7:48 pm, leaving 36 people dead and nearly 600 injured.

(cont. in next post)
 
Messages
399
Location
Niagara Falls, Ontario
(part 2, cont.)

As the Bridge Creek-Moore tornado weakened and began to dissipate, another supercell produced an intense F3 tornado around 45 miles to the northwest in Kingfisher County to the south of Altona. The tornado intensified extremely rapidly, severely damaging a farmhouse and snapping and partially debarking trees soon after touching down. The tornado then struck a well-built and anchored brick house, tearing away the roof and collapsing most of the walls. Mobile homes to the northeast were demolished as well before the tornado dissipated.

Minutes later, the same supercell produced a violent wedge tornado to the south-southwest of Dover. This tornado tracked directly through the town, rapidly expanding to 880 yards wide and reaching F4 intensity. Mobile homes in town were completely obliterated, with debris scattered for long distances and steel frames found mangled and wrapped around tree trunks, and well-built frame houses were leveled. Perhaps most impressively, a concrete and steel industrial building was almost completely flattened, with only a few interior walls still standing. Trees were snapped and debarked in town as well.

Around three hours after the Bridge Creek—Moore tornado dissipated, another extremely intense tornado developed in Logan County, roughly 50 miles to the north. The multiple-vortex funnel slowly extended to the ground and began a meandering path to the east-northeast, reaching its peak strength as it made its closest approach to the town of Mulhall. The tornado was closely followed by a DOW team, and its winds were recorded for several minutes – a very rare occurrence. While officially rated F4, the Mulhall tornado’s recorded winds were well inside the EF5 range on the Enhanced Fujita Scale, which, coupled with the tornado’s immense size, suggests that it was most likely capable of producing F5 damage.

View attachment 1627

The tornado, which was already very large when it formed, gradually grew in both size and intensity as it tracked to the east. As the tornado passed near the tiny community of Crescent, a frame house on the outer left flank was flattened in typical F4 fashion. Approaching the town of Mulhall, the tornado continued to rapidly expand, reaching a record-breaking width of 4.3 miles (6.9 kilometers). As residents scrambled for shelter, a rain of debris from disintegrating buildings began to fall on the small town. Roughly two-thirds of the buildings in town were severely damaged or destroyed by the tornado’s extreme outer bands, and the Mulhall—Orlando Elementary School was demolished, with only interior walls still standing. The town’s water tower was toppled and burst, creating a surge of water which pushed a house off its foundation. To the east of Mulhall, a car was blown out from beneath an overpass on Interstate 35, killing the driver, and grass at the edge of the overpass was partially uprooted.



As the DOW crew followed the tornado as it passed Mulhall, wind velocities of 246 to 257 mph were recorded within the tornado’s inner core, with the team later mentioning estimated peak winds of 277 to 299 mph in a CWSR-published research paper. Despite the intensity of the damage in and near Mulhall, the town was only affected by the outermost circulation, with the inner core of the tornado passing more than a mile to the south over empty meadows. Had the tornado’s core struck more populated areas, it is almost certain that a wide swath of F5 damage would have been observed. Storm chaser Roger Edwards, who led the team which analyzed the Mulhall tornado’s winds and internal structure, would later state that the tornado may have been as violent (or more violent) as the Bridge Creek—Moore tornado.

As the Mulhall tornado was ongoing, another intense multiple-vortex tornado developed to the south near El Reno and tracked northeast through mostly rural areas, destroying mobile homes, tearing away the top of a transmission tower, and heavily damaging three frame houses. As the tornado tracked near Piedmont towards the end of its path, it ripped a 3,000 lb oil tank from its anchoring and tossed it nearly half a mile. The tornado's radar signature, coupled with the long-distance movement of heavy industrial equipment suggest that it was likely violent, but was officially rated F3 based on structural damage.

Shortly after the El Reno-Piedmont tornado touched down, the final intense tornado of the day touched down in Lincoln County to the northeast of Sparks, slowly gaining strength as it moved past Davenport, and reaching F2 strength as it struck a trucking plant on the west side of Stroud, demolishing the building and scattering girders for hundreds of yards. The Stroud Municipal Hospital had its roof mostly removed, and seven stores at the Tanger Outlet Mall were demolished at F3 strength. The tornado continued for around two miles to the northeast of Stroud before dissipating. It was one of the longest-duration tornadoes of the day, remaining on the ground for 1 hour and 38 minutes.

This tornado outbreak will likely be known as the classic Plains States outbreak for many years to come, and with good reason. In addition to the number and intensity of the tornadoes produced, the tornadoes of the outbreak disproved a number of safety myths, and served as a reminder that for all our technological advances and constantly-improving scientific understanding, humanity is still very much vulnerable when nature's fury is at its worst.
 
Messages
74
Location
Lenexa, KS
This event tends to be associated with the Andover, Kansas tornado outbreak on April 26, 1991. I tend to wonder what kind of DOW reading you would have gotten on the Andover tornado. There was also a tornado in Red Rock, Oklahoma that had a DOW reading of 286 mph.
 
Messages
399
Location
Niagara Falls, Ontario
This event tends to be associated with the Andover, Kansas tornado outbreak on April 26, 1991. I tend to wonder what kind of DOW reading you would have gotten on the Andover tornado. There was also a tornado in Red Rock, Oklahoma that had a DOW reading of 286 mph.
If I had to guess I would say the Andover and Bridge Creek tornadoes were almost identical in strength. The Andover tornado caused slightly more intense wind-rowing and debris granulation, but the Bridge Creek tornado caused more impressive ground scouring, so it's very hard to say which one was stronger.

Great post on how this event unfolded. Almost reads like it should be a long-overdue new post on Stormstalker's blog.

Thanks, that's some pretty high praise!
 
Messages
74
Location
Lenexa, KS
The Greensburg tornado on May 4, 2007, swept away six or seven homes at EF5 intensity, did some very impressive tree debarking, knocked over the towns water tower, and I believe it scoured out one small area of Greensburg. While it was a very intense tornado I don't think it was as strong as the Andover or Bridge Creek/Moore/OKC tornadoes.
 
Messages
399
Location
Niagara Falls, Ontario
The Greensburg tornado on May 4, 2007, swept away six or seven homes at EF5 intensity, did some very impressive tree debarking, knocked over the towns water tower, and I believe it scoured out one small area of Greensburg. While it was a very intense tornado I don't think it was as strong as the Andover or Bridge Creek/Moore/OKC tornadoes.
Yeah, I would say the El Reno tornado was around the same level, while the Greensburg tornado was a little weaker (probably more comparable to the Mulhall tornado). The Greensburg tornado did scour a few patches of grass and topsoil in town, and also tossed a number of freight cars from the railroad tracks, while the El Reno tornado caused ground scouring up to 8 inches deep, tossed a 20,000-pound oil tank a full mile, and an oil derrick that weighed nearly 900 tons was rolled several times.

For what it's worth the El Reno tornado had recorded winds of 284 mph, while the Greensburg tornado had recorded winds of around 260 mph. That being said the Greensburg tornado seemed to be at peak strength just before tracking through the town, and the recording was a couple minutes afterwards, so the peak winds were probably a bit higher than 260 mph. Personally, I would say that the El Reno tornado had to be packing winds near 300 mph when it hit the Cactus-117 oil derrick, but that's really just an educated guess.
 
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warneagle

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El Reno 2011 really gets overlooked because of the Super Outbreak and the Joplin tornado, but it's a candidate for the most violent tornado of that year, imo.
 
Messages
74
Location
Lenexa, KS
Yeah, I would say the El Reno tornado was around the same level, while the Greensburg tornado was a little weaker (probably more comparable to the Mulhall tornado). The Greensburg tornado did scour a few patches of grass and topsoil in town, and also tossed a number of freight cars from the railroad tracks, while the El Reno tornado caused ground scouring up to 8 inches deep, tossed a 20,000-pound oil tank a full mile, and an oil derrick that weighed nearly 900 tons was rolled several times.

For what it's worth the El Reno tornado had recorded winds of 284 mph, while the Greensburg tornado had recorded winds of around 260 mph. That being said the Greensburg tornado seemed to be at peak strength just before tracking through the town, and the recording was a couple minutes afterwards, so the peak winds were probably a bit higher than 260 mph. Personally, I would say that the El Reno tornado had to be packing winds near 300 mph when it hit the Cactus-117 oil derrick, but that's really just an educated guess.
Wasn't the Chickasha and Goldsby tornado possibly of similar strength to the El Reno tornado on May 24, 2011? I am sure both of them tornadoes would have rolled a 900 ton oil derrick a few times had they encountered one at peak intensity. May 24, 2011 also featured a large 45% hatched area for strong to violent tornadoes as that day was very incredible.
 

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