Views of the 1999 Bridge Creek F5 Tornado and the World Record DOW Velocity

Aerial view of damage left behind by the Bridge Creek tornado. The tornado’s proximity to the I-44 gave the Doppler On Wheels an excellent opportunity to analyze the storm at close range for an extended period of time.

□ On May 3rd, 1999, all the atmospheric ingredients needed for the creation of large, long-tracked tornadoes came together over the Great Plains. A dry line atop the Oklahoma and Texas Panhandles separated a mass of warm, humid air from dry, cool air slowly encroaching from the west. Weather balloons released across Tornado Alley rose into the air in erratic zigzags, and indication of rapidly shifting winds at different altitudes. The atmosphere was unstable, and by late morning the National Weather Service had upgraded the severe weather risk from slight to moderate.

Around 4pm, weather satellites captured a series of supercell thunderstorms exploding out of the afternoon sky. At 6:20pm, a large funnel descended from the sky near Amber, Oklahoma. The tornado, later dubbed “A9” on survey maps, rapidly intensified as it thundered northeast through Grady County. Within minutes of touchdown, the storm expanded into a massive wedge more than a half mile wide. Storm chasers captured the tornado as it tore past the Chickasha Municipal Airport and entered an unpopulated area to the northeast.

The mesocyclone that spawned the tornado was exceptionally violent. Low hanging clouds or “skud” swirled around the massive tornado at terrific speeds as large satellite vortices rotated around the main funnel, causing additional damage. Local news stations in Oklahoma City quickly focused their attention on the Grady County storm, and regular programming was interrupted by live broadcasts of the approaching tornado.

The tornado struck little for many miles before taking aim on the small, unincorporated town of Bridge Creek. By the time the tornado reached the town’s first cul-de-sacs it had expanded to a mile in width.

View of F5 damage on County Street 2977 in Bridge Creek. The highest concentration of fatalities throughout the tornado’s path occurred in this area, and 75% of them were related to mobile homes.

The tornado was at peak intensity as it approached the I-44 Interchange in Bridge Creek. Unfortunately, many of the households in the area were mobile homes with no underground storm shelters. Some residents sought protection in irrigation ditches and culverts beneath roads, though many were seriously injured by the blizzard of flying debris. One young couple was caught outside while running a short distance to their neighbor’s storm cave (Pam, Brown, Kruger et al., 2001). Their bodies were found wrapped in debris more than 200 yards from their destroyed home.

Damage in the Bridge Creek area was among the most intense ever surveyed. Frame homes were swept completely away and mobile homes in the direct path of the storm disappeared without a trace. Aerial imagery around the I-44 Interchange showed a 200-yard wide core of extreme damage in which vegetation was ripped from the ground and trees were stripped of all bark and branches. Surveyors also documented vehicles thrown up to one mile. In total, 12 people were killed in Bridge Creek. The fatality to injury ratio was seven times higher in Grady County than in the Oklahoma City suburbs, a testament to the storm’s incredible ferocity in the area.

Aerial view of F5 damage in Bridge Creek. One survivor in this area crawled deep into a narrow drainage pipe as the tornado approached from the southwest. He was injured by flying debris and nearly ripped out of from his unconventional hiding space as the storm passed over. (Image by Doug Crowley)

The remains of a frame home in Bridge Creek (the DOC Service Assessment stated this home was in Cleveland County near Moore). Three of the 12 fatalities in Grady County were in frame homes, many of which were swept cleanly away. The vegetation scouring was among the most intense ever surveyed.

Perhaps the most infamous image of the May 3rd outbreak is this picture of a pulverized pick-up truck wrapped around a telephone pole in Grady County. Unlike many other tornadoes that have entered populated areas, there were no fatalities in vehicles during the Bridge Creek tornado. (Image by Curtis Carey)

This well-anchored home in Grady County was struck by the tornado at maximum intensity. Grass was ripped from the ground and low lying vegetation was stripped completely of bark and branches, both indications of extremely intense surface winds. (Image by Jim LaDue)

The Bridge Creek tornado traveled parallel to the I-44 for much of its life. Had the tornado travelled a half mile farther to the south, it would have spent over 20 miles directly over the freeway and likely killed dozens of motorists. Surprisingly, none of the tornado’s fatalities occurred in vehicles. There were four fatalities, however, in which people attempting to flee were killed while running to their vehicles. Additionally, there were two well-documented deaths beneath freeway overpasses. A third overpass death often attributed to the tornado was actually caused by a separate storm north of Oklahoma City near the town of Mulhall.

It is remarkable that only two women were killed seeking shelter beneath overpasses. Both locations were struck by the tornado after it had reached peak intensity, likely allowing more than two dozen others to escape with their lives – though many of the survivors were left with serious injuries. In the image above, a mangled vehicle was found beneath an (unoccupied) overpass after being blown more than half a mile.

The path of the tornado along the I-44 gave the Doppler On Wheels (DOW) an excellent opportunity to stay within close proximity to the tornado for a long period of time. As a result, the DOW was able to thoroughly analyze the storm throughout its mature stage. It is a common misconception that mobile doppler radar “measures” tornadic winds and provides researchers with a single numerical value. Instead, mobile radar analyzes the movement of condensation and debris and calculates a statistical range in which the particle velocity can be estimated.

As the Bridge Creek tornado passed the I-4 interchange, the DOW calculated a velocity that likely fell between 281 and 321mph. The figure, often quoted as 301mph +-20mph, remains the highest radar velocity ever recorded. This is by no means, however, evidence to support that the Bridge Creek tornado was “the strongest tornado ever recorded.” Far less than 1% of all violent tornadoes have been tracked by mobile radar, and of the tornadoes that have been analyzed, only a fraction of their total path lengths were recorded. The Bridge Creek tornado’s unique path adjacent to a freeway gave researchers a rare opportunity, and it is not surprising that the record velocity was calculated given the near perfect circumstances.

Image of the Bridge Creek tornado from the DOW. The time stamp indicates that this picture was taken around the time the record reading was calculated. (cswr.org)

Ground scouring indicates that the tornado remained intense as it entered McClain County. The path width narrowed slightly, and the tornado’s appearance changed into a ‘stovepipe’ formation with a wide debris cloud at its base. After remaining parallel to the I-44 for more than 40 minutes, the tornado reached a bend in the freeway and crossed over it, leading to McClain County’s only fatality. A woman who had taken shelter under an overpass with her son was swept away and killed while others who had taken shelter in the same location were injured by flying debris and found plastered in red dirt.

Vegetation scouring near the Grady/McClain County line. (Image by Doug Crowley)

Three views of the F5 tornado. The first two images show the tornado as it entered Cleveland County. While the tornado often appeared as a massive wedge, the width of the primary damage path through Moore was generally less than 200 yards wide. At right, the appearance of the tornado after it had entered Moore and filled with debris.

The city of Moore was nearly motionless as the tornado entered Cleveland County. Sirens had been sounding for nearly an hour, and on-air meteorologists had advised viewers in the strongest language ever broadcast to seek shelter or “you will not survive this storm.” Entire rows of tightly packed homes were obliterated as the tornado entered town from the southwest, filling the sky with debris. One of the first housing subdivisions directly impacted by the tornado was Eastlake Estates, located to the south of Westmore High School. While the tornado engulfed a wide area, the extreme damage was confined to a streak 100 yards wide in the center of the damage swath.

Aerial view of Eastlake Estates, where the last instances of F5 damage were documented.. (Image by Bob Webster)

Another view of Eastlake Estates. The F5 damage was confined to two clusters of homes. Approximately four homes experienced F5 damage on 131st Terrace (the first row of destroyed homes at top right). Just a block to the northeast on 129th Street, another three homes were swept away in F5 fashion. The close proximity of the homes made determining the exact F-Scale contours difficult. At extreme top right is the Country Place subdivision, where F5 damage also occurred. (Image by Bob Webster)

National Weather Service employees photographed the row of homes that were swept away in F5 fashion in Eastlake Estates. At right, completely debarked trees in a field to the west of Moore.

Near F5 damage in Moore. Heavy vehicles showered down onto neighborhoods outside the corridor of extreme damage (Grazulis, 2001). (Image by Bob Webster)

Pronounced ground scouring marked the tornado’s path through an undeveloped area east of Moore. The tornado made a curve to the north and entered Del City at F4 intensity. (Image by Bob Webster)

The tornado swept through a trucking facility on the I-240, killing two employees. Ground scouring was significant, and damage in the area was “near F5” in intensity. (Image by Bob Webster)

Rows of homes in Midwest City were reduced to piles of rubble as the tornado entered Oklahoma County. (Image by Bob Webster)

Aerial view of high-end F4 damage near Sooner Avenue in Midwest City. The tornado remained intense throughout its entire life and continued causing F4 damage until moments before dissipating. (Bob Webster)

Eleven people were killed in Moore, and a further 12 were killed in Oklahoma County, specifically in Del City and Midwest City. A detailed morbidity report concluded that a third of the documented victims were killed in “recommended places”, meaning in an interior room in a frame home. Excluding the deaths in Grady and McClain County, it is probable that most of the victims in the Oklahoma City area had taken appropriate shelter. The intensity of the tornado made survival, even in some well-built homes, difficult. At least two of the fatalities in Moore occurred when vehicles were hurled atop people huddled in their homes.

The tornado was the deadliest in the United States during the 1990’s and remained the single most damaging tornado in history until 2011. Even so, the death toll of 36 people was surprisingly low. Excellent warning, live television broadcasts, good visibility and the tornado’s fairly slow forward speed reduced the number of fatalities. Had the tornado formed two hours later, after dark, the death toll could have easily been twice as high.

The path of the F5 tornado is still visible years later in satellite images. A trail of deforestation can be seen at bottom left near Bridge Creek, and the northerly turn the tornado made in Del City is visible at top right.

Some falsely believed that the Bridge Creek tornado was ‘proof’ that no single tornado could ever again cause over 100 fatalities. This assumption was shown to be terribly wrong in 2011 when an EF5 tornado killed 158 people in Joplin, Missouri. While the Bridge Creek tornado’s death toll was testament to improved forecasting and technology, the storm was, in a sense, perfect from a forecasting perspective. Tornadoes that intensify rapidly near populated areas and tornadoes obscured by precipitation will continue to pose a major threat to cities across the county. A tornado causing over 1,000 fatalities in United States is not just a possibility but, given enough time, a meteorological certainty.

*Bob Webster’s complete aerial photo gallery of tornado damage in Moore and Oklahoma County can be found here. Used with permission.