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Remembering the Great Plains tornado outbreak of May 3-4, 1999. : meteorology

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Information via NWS Norman

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📷On May 3, 1999, multiple supercell thunderstorms produced many large and damaging tornadoes in central Oklahoma during the late afternoon and evening hours. Some of these storms were killers, including the twisters which moved through and/or near Dover, Shawnee, Perry and Bridge Creek, and the Moore and southern Oklahoma City metropolitan areas. Additional tornadoes also hit areas in south central Kansas, eastern Oklahoma and northern Texas, with over 70 tornadoes being observed across the region, and some tornadoes occurring the during the morning and early afternoon hours of May 4, 1999. The total tornado count in Oklahoma makes the May 3-4, 1999 tornado outbreak the largest ever recorded in the state.

A total of 40 people in Oklahoma were killed by the tornadoes on May 3-4, 1999 and another 675 persons were injured. Many homes and businesses were damaged or destroyed throughout the affected areas and the total damage estimate was $1.2 billion. Five deaths, 100 injuries and heavy damage were reported from the Wichita, Kansas metro area.

The map below shows the approximate location and paths of the most damaging tornadoes which occurred on May 3-4, 1999. The official storm data report from May 1999 for NWS Norman forecast area can be found here. The official storm data report from May 1999 for NWS Tulsa forecast area can be found here. Frequently asked questions about the F5 tornado that went through Bridge Creek, Moore and the OKC metro area can be found here.

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Meteorological Summary:

As daylight broke on May 3rd of 1999, across Oklahoma, skies were generally cloudy with a deck of low stratus clouds spread over much of the state. The only exception was along and west of a dryline that stretched from near Gage, Oklahoma to near Childress, Texas at dawn. The stratus clouds were the result of significant moisture return that occurred overnight, as morning dewpoints were in the low to mid 60s. Not surprisingly, the air was quite humid at the surface, with temperatures only in the mid to upper 60s.

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Meanwhile, the threat for severe weather was being closely monitored by the Storm Prediction Center and the National Weather Service forecast office in Norman, Oklahoma. The Storm Prediction Center had posted a “slight risk” (image courtesy of SPC publication) on their early morning outlooks for most of Kansas, Oklahoma, and north Texas. The Slight Risk was indicative of the general consensus by forecasters that there was a severe weather threat over the Southern Plains, including the risk of some supercells. However, the precise location of the greatest threat area was a bit uncertain that early in the morning.

The forecasters at the forecast office in Norman agreed about the threat of severe weather, and mentioned the risk in a 6:30 AM CDT Thunderstorm Outlook. It mentioned the increasing low-level moisture, dryline and approaching upper-level low pressure trough would combine to cause a threat of large hail, damaging winds and tornadoes. It also cautioned emergency managers and spotter groups to be prepared for possible activation in the afternoon. In fact, the threat of severe thunderstorms was mentioned in most of the zone forecasts for the counties in Oklahoma at the 4:30 AM CDT issuance.

Through the morning hours, forecasters became progressively more certain of a significant severe weather episode. The low cloud cover began to break up in advance of the dryline as daytime heating commenced. Although high cirrus clouds would overspread the area later, into the afternoon hours, at least some filtered sunshine was observed in most spots for most of the day. The sunshine and heating, combined with abundant low-level moisture, would combine to produce a very unstable air mass. As forecasters modified 12Z (7:00AM CDT) upper air balloon sounding data with expected afternoon conditions, they noticed the potential for a weakening cap and CAPE values potentially exceeding 4000 j/kg. Such instability levels are climatologically favorable for severe supercells and tornadoes when combined with the strong directional shear that was also forecast.

Accordingly, the risk of severe thunderstorms was upgraded to moderate (graphic: courtesy SPC) in a new outlook at 11:15 AM CDT. Here is an excerpt of the text from that outlook: “…will provide sufficient shear for a few strong or violent tornadic supercells given the abundant low level moisture and the high instability.” Forecasters at the NWS forecast office in Norman mentioned the increasing threat of a severe weather outbreak from late in the afternoon and into the evening in a Thunderstorm Outlook at 12:30 PM CDT. The threat for tornadoes was again mentioned.

As the early afternoon wore on, the potential for a significant severe weather outbreak appeared more and more likely. Special weather balloon launches around 1 PM suggested wind profiles highly conducive for tornado development – speeding up with height, and changing directions with height. They also showed a very unstable atmosphere. As this special article on the Norman Weather Partners website points out, “it became more obvious something major was looming.” Therefore, at 3:49 PM CDT, the risk of severe weather was upgraded to a high risk (graphic) for all of the NWS Norman forecast area.

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The first cumulus towers developed, but quickly dissipated between 3:00PM and 3:15PM CDT in northwestern Texas. However, renewed cumulus development occurred between 3:30PM and 4:00PM CDT over southwest Oklahoma. A few of these cumulus towers developed into significant supercells by 5:00PM CDT before moving northeast towards the Oklahoma City metropolitan area. The first Severe Thunderstorm Warning was issued at 4:15PM CDT for Comanche County, and five minutes later quarter sized hail was falling in Lawton.

At 4:47PM CDT, the first Tornado Warning was issued for Comanche, Caddo and Grady Counties. Four minutes later the first tornado report was received at the NWS office in Norman, from a spotter 7 miles east-northeast of Medicine Park. Just beyond the 5 o’clock hour, it became obvious that a significant outbreak was unfolding, and that tornadoes would threaten the Oklahoma City metropolitan area. Forecasters at the NWS office in Norman noticed that the thunderstorms continued to gain strength in a very unstable and moist air mass.

At 5:41PM CDT, the NWS in Norman issued a Short Term Forecast that discussed the potential for tornadic supercells to track northeastward into the Oklahoma City metropolitan area. It cautioned people to remain alert through the evening hours. By 6:30PM CDT, the tornadic supercells were expected to threaten the outer reaches of the Oklahoma City metropolitan area within the next hour. A new Short Term Forecast discussed the ongoing supercells and forecasted that the threat of tornadoes “will continue to be high through the evening”.

The tornadic supercells then continued to move northeast into the Oklahoma City metro area, and across Central Oklahoma. For information about individual storms, click on the links provided at the top of this writeup. Here is a map of the supercell tracks across the NWS Norman county warning area, as adapted from radar data and the SPC publication previously referenced:

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Tornado A9: The May 3, 1999 Bridge Creek-Newcastle-Oklahoma City-Moore F5 Tornado.

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The Parent Supercell Thunderstorm – Storm A

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Storm A produced 14 tornadoes over a period of about 3.5 hours and was eventually responsible for the F5 tornado (A9) that struck Bridge Creek, Oklahoma City, and Moore. The storm began around 3:30 PM CDT (2:30 PM CST) in Tillman County, OK. It moved to the northeast and once it reached parts of Comanche County it produced its first tornado at 4:51 PM CDT, 7 miles east-northeast of Medicine Park, Oklahoma (A1). As the storm crossed from Comanche County into Caddo County, it produced four other tornadoes, one of which was rated an F3 (A3). The F3 tornado struck a rural area just east of Apache. The sixth tornado that the storm produced crossed from Caddo County into Grady County and was rated a strong F3 tornado (A6). This tornado ended shortly after striking the northwest sides of Chickasha.

The storm gained intensity and became better organized as it moved into Grady County. As it moved into the Amber area in Central Grady County, it produced a tornado that would become the most famous tornado of the entire outbreak, and one of the most famous tornadoes in U.S. history (A9). The track of the tornado is detailed below, but in general it tracked from near Amber, to the far northern sections of Newcastle, through the southern sections of Oklahoma City, to the northern sections of Moore, through OKC again, to Del City, and on into Midwest City. It was rated an F5 on the Fujita Scale, the highest rating that a tornado can achieve. Two satellite tornadoes rotated around this main tornado, which was a large, wedge-shaped tornado along portions of its track. The storm produced three more tornadoes in eastern Oklahoma County, and the last tornado produced by Storm A ended at 8:25 PM CDT.

Storm A produced 5 strong or violent tornadoes (rated F2 or higher) during its lifespan. The combined damage path length of all 14 tornadoes that the storm produced is over 70 miles.

Tornado A9

The 9th tornado, A9, was a violent and long-tracked tornado, and eventually produced F5 damage in Bridge Creek, Oklahoma City, and Moore.

Early Stages

This tornado developed in Grady County about two miles south-southwest of Amber, and quickly intensified as it crossed OK State Highway 92. F4 damage was first discovered about 4 miles east-northeast of Amber, and extended for 6½ miles as the tornado continued to move northeast.

Bridge Creek

Two areas of F5 damage were observed in the Bridge Creek area. The first was in the Willow Lake Addition, a rural subdivision of mobile homes and some concrete slab homes in Bridge Creek, in far eastern Grady County. Two homes were completely swept from their concrete slabs, and about one dozen automobiles were carried about ¼ mile. All mobile homes in this area in the direct path of the tornado were obliterated, resulting in a high concentration of fatalities. Asphalt pavement about 1 inch thick was also peeled from a section of rural road EW125. The second area of F5 damage was observed about 1 mile west of the Grady/McClain County line and consisted of a cleanly swept slab home with foundation anchor bolts and another vehicle lofted ¼ mile. The maximum width of damage in Bridge Creek was estimated to be 1 mile.

Approximately 200 mobile homes/houses were destroyed, and hundreds of other structures were damaged. The Ridgecrest Baptist Church in Bridge Creek was also destroyed. Twelve people died in Bridge Creek, nine in mobile homes. All fatalities and the majority of injuries were concentrated in the Willow Lake Addition, Southern Hills Addition, and Bridge Creek Estates, which consisted mostly of mobile homes. Compared to sections of Oklahoma and Cleveland Counties, which were also in the path of this tornado, eastern Grady County, including the Bridge Creek area, was rural and sparsely populated.

Newcastle

The tornado maintained a nearly straight path to the northeast, paralleling Interstate 44 as it entered McClain County. An exception was when it made a slight jog to the right and moved directly over the 16th Street overpass in Newcastle, where a woman was killed when she was blown out from under the overpass. The tornado continued into northern sections of rural Newcastle and crossed the interstate again just north of the US 62 Newcastle interchange.

While this tornado was moving through the northern portion of Newcastle, a weak satellite tornado (A10), touched down in a field in rural north Newcastle. Two areas of F4 damage were observed in McClain County, associated with tornado A9. The first area overlapped the Grady/McClain County line and extended to about 3 miles northwest of Newcastle, ending just west of the 16th St. overpass on Interstate 44, while the other area was observed 2 miles northwest of Newcastle. In McClain County, 38 homes and 2 businesses were destroyed, and 40 homes were damaged.

South Oklahoma City, west of Moore

Damage then diminished to F2 intensity as the tornado crossed the Canadian River into northern Cleveland County. The tornado entered Cleveland County between Portland and May Avenues, and between SW 164th and SW 179th in south Oklahoma City. Damage was rated F2 in this area with a path width averaging ½ mile.

The first major housing development to be struck in Cleveland County was Country Place Estates, located just west of Pennsylvania Ave., where about 50 homes were damaged. One dozen of these homes received F4 damage. One slab home was cleanly swept from its foundation, and several vehicles were picked up from the subdivision and tossed across Pennsylvania Ave., a distance of approximately ¼ mile. One vehicle was found under a bridge just east of the intersection of Pennsylvania and SW 134th. This particular area of damage has been rated high F4/low F5. Oklahoma City Police indicated that part of an airplane wing, believed to have originated from Chickasha Municipal Airport in Grady County, landed in this area.

The tornado then tracked through Eastlake Estates, a densely populated housing development, located north of SW 134th and between Pennsylvania and Western, where 3 fatalities occurred. Entire rows of homes were flattened to piles of rubble. Four adjacent homes on one street were nearly cleaned off their foundations leaving only concrete slabs, which earned an F5 rating. Three other homes in this housing division also received F5 damage, with the remaining destruction rated high F4. Three people also died in the 600-unit Emerald Springs Apartments on Western Ave., across the street from Eastlake Estates. One 2-story apartment building on the north end of the apartment complex was virtually flattened, and received an F5 rating.

Westmoore High School, just north of Eastlake Estates, was also heavily damaged. Although a well-attended awards ceremony was being held at the school during the tornado, no one was injured, however dozens of vehicles in the school parking lot were either damaged or destroyed. F4 damage continued northeast into another residential area east of Western Ave. and south of 119th St.

Moore

The tornado then entered the western city limits of Moore (Cleveland County) along Santa Fe and near NW 12th, and produced damage ½ to ¾ mile wide. Maximum damage, rated high F4/low F5, extended northeast to near Janeway with several large groups of homes flattened. Four people died in this residential area. F4 damage continued to South Shields, just north of the junction with Interstate 35. A woman was also killed when she was blown out from under the Shields overpass of Interstate 35.

The tornado appeared to weaken just slightly after crossing Interstate 35, however it remained a formidable storm with widespread high F3/low F4 damage observed in Highland Park, a residential area south of the First Baptist Church on 27th St. in Moore. Escaping with relatively minor damage, and being located near the halfway point of the tornado path, the First Baptist Church in Moore eventually served as the primary coordination center for most tornado relief efforts.

South Oklahoma City, northeast of Moore

The tornado then continued northeast and entered the southern portion of a sparsely populated industrial district. F4 damage continued through this area to near SE 89th St., the Cleveland/Oklahoma County border. Moving into Oklahoma County, the tornado curved northward, through the remaining industrial district north of Interstate 240, where 2 businesses were destroyed. This damage was rated F4. Two people were also killed at a trucking company near the intersection of S. Bryant Ave. and Interstate 240.

A freight car, with an approximate weight of 18 tons, was picked up intermittently and blown ¾ mile across an open field. The body of the freight car was deposited southeast of the intersection of S. Sunnylane Rd. and SE 59th. Gouge marks were observed in the field every 50 to 100 yards, suggesting the freight car had been airborne for at least a short distance. While tornado A9 was moving through southeast Oklahoma City, another tornado A11) touched down briefly near the intersection of SE 80th and Sooner Rd. (Oklahoma County). Tornado A9 then entered residential neighborhoods between SE 59th and SE 44th, where a woman was killed in her house.

Del City and Tinker AFB

Crossing SE 44th into Del City (Oklahoma County), the tornado moved through the highly populated Del Aire housing addition killing 6 people and damaging or destroying hundreds of homes, many with F3/F4 damage. The tornado then crossed Sooner Rd., where it damaged an entry gate and several costly structures at Tinker Air Force Base.

Midwest City and the Storm’s Demise

Tornado A9 then crossed 29th St. into Midwest City (Oklahoma County), destroying 1 building in the Boeing Complex and damaging 2 others. Widespread F3/F4 damage continued as the tornado moved across Interstate 40, affecting a large business district. Approximately 800 vehicles were damaged at Hudiburg Auto Group, located just south of Interstate 40. Hundreds of the vehicles were moved from their original location, and dozens of vehicles were picked up and tossed northward across Interstate 40 into several motels, a distance of approximately 0.2 miles. Numerous motels and other businesses including Hampton Inn, Comfort Inn, Inn Suites, Clarion Inn, Cracker Barrel, and portions of Rose State College, were destroyed. Some of the damage through this area was rated high F4, however low F5 was considered.

The tornado then continued into another residential area between SE 15th and Reno Ave., where 3 fatalities occurred. High F4 damage was inflicted to 4 homes in this area. Two of these homes were located between SE 12th and SE 11th, near Buena Vista, and the other 2 homes were located on Will Rogers Rd., just south of SE 15th. Damage then diminished rapidly to F0/F1 as the tornado crossed Reno Ave. The tornado dissipated 3 blocks north of Reno Ave., between Sooner Rd. and Air Depot Blvd.

Summary

The Oklahoma State Department of Health in Oklahoma City recorded 36 direct fatalities. In addition, 5 people died of illness or accident during or shortly after the tornado, and were not considered in the direct fatality total. The number of injuries was estimated at 583, based on numbers provided from the Oklahoma Department of Health, which were then adjusted to account for people assumed to be unaccounted for. Injuries which resulted from removing debris, conducting search and rescue efforts, and taking shelter from the tornado, were not considered in the injury total. An estimated 1,800 homes were destroyed, and 2,500 homes were damaged, resulting in approximately $1 billion in damage.

/u/FakeMikeMorgan

2021-05-03 11:29:34

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