Analysis of the 2013 Moore Tornado

View of the Moore tornado less than two minutes before it entered the city. (Video stills by David Demko and Heidi Farrar)

View of the Moore tornado moments before it impacted Briarwood Elementary School at EF5 intensity. (Video stills by David Demko and Heidi Farrar)

□ The most catastrophic tornado in recent Oklahoma history touched down in the midst of a large scale severe weather outbreak on May 20th, 2013. The tornado devastated southern sections of Moore, a large suburb to the southwest of Oklahoma City. Moore was the focus of international media following a similar F5 tornado that swept through neighborhoods only one mile to the north in May of 1999.

Aerial view of extreme tornado damage. While initially reported as being in excess of two miles wide, the tornado's primary damage path was approximately 500 yards wide. (Image by Steve Gooch)

Aerial view of extreme tornado damage in Moore (Santa Fe Avenue is the large street at right). A damage survey later concluded that several homes on SW 147th Street (left center) were swept away in EF5 fashion (Ortega, Burgess et al., 2014). While initially reported as being in excess of two miles wide, the tornado’s primary damage path was approximately 100 to 300 yards in width. (Image by Steve Gooch)

Still frames of the catastrophic Moore tornado. At top left, view of the tornado several miles east of Bridge Creek as it rapidly intensifies. The tornado widened to over a half mile in width as it thundered to the east-northeast at approximately 35mph. At bottom left, the tornado became rain wrapped as it crossed the Canadian River into Cleveland County. At bottom right, the appearance of the tornado as it entered the western edge of Moore.

At top left, view of the tornado as it rapidly intensified in Grady County. At bottom left, the tornado became partially rain wrapped as it crossed the Canadian River into Cleveland County. At bottom right, the tornado as it entered Moore. (Video by KWTV)

The tornado touched down at 2:55pm near the town of Bridge Creek, the same community that was nearly wiped off the map following the 1999 Moore tornado. Video of the tornado suggests it initially appeared as a large “stovepipe” before entering a period of rapid intensification, at which point it expanded and became partially shrouded in a column of rain. The swirling mass reached high-end EF4 intensity as it thundered through rural areas east of the Canadian River. Several large homes on SW 155th Street were swept completely away and grass was scoured from the ground as the tornado approached peak intensity just west of Moore. The Wallace Horse Park on Western Avenue was impacted directly by the tornado, killing all but one of the horses being held at the facility (“Oklahoma Officials…”, 2013). The bodies of several horses were recovered a quarter mile away near Sylena Way. Trees along Western Avenue were stripped of bark and branches and left pointing towards the east. The tornado reached the edge of Moore at approximately 3:15pm. Witnesses described the tornado as a “black wall” surrounded by a continuous rain of debris.

Ground scouring and empty foundations near Country Edge Drive, a half mile west of Moore. (Image by Steve Gooch)

Ground scouring and empty foundations near SW 155th Street, a half mile west of Moore. The tornado was likely at EF5 intensity in this area, though building construction only permitted a high-end EF4 rating. The Wallace Horse Park was located at the intersection at top left. (Image by Steve Gooch)

Briarwood Elementary School (bottom) was impacted directly by the tornado as it entered a densely populated section of Moore. (Image by Steve Gooch)

Briarwood Elementary School (bottom) was impacted directly by the tornado as it entered a densely populated section of Moore. The damage to the school was deemed to be of EF5 intensity (NWS, 2013). One woman was killed just east of the school in a home on SW 147th Street. (Image by Steve Gooch)

Extreme home damage in western Moore. The width and extent of the home damage in areas west of the I-35 was more intense than the damage caused by the 1999 storm. (Image by David McNeese)

Extreme home damage in western Moore. (Image by David McNeese)

The tornado entered Moore near the intersection of 149th and Western Avenue, where hundreds of large one and two-story brick homes were obliterated. Briarwood Elementary School was impacted directly by the tornado at EF5 intensity, resulting in the near complete destruction of the school’s classroom buildings and gym. The tornado roared eastward towards Santa Fe Avenue, where at least one fatality occurred in the destruction of a two-story home. After roaring over Penn Lane, the tornado passed directly over Plaza Towers Elementary School at probable EF5 intensity. The large, brick school was nearly leveled while more than 70 students and teachers huddled in the bathrooms. Seven students were crushed to death as the building collapsed – initial reports that the students “drowned” in a puddle or swimming pool were erroneous (Kelly, 2013). Homes just south of the school on SW 14th Street were swept completely away and grass in a nearby field was scoured from the ground. One survivor in the area said the tornado shook the ground like an earthquake and was “louder than anything he had ever heard before” (Lawrence, 2013). While the survey analysis is ongoing, aerial imagery suggests that some of the most intense damage in Moore likely occurred in the vicinity of Plaza Towers Elementary.

Satellite view of the tornado's devastating path through Moore. The tornado's most intense damage may have occurred just southwest of Briarwood Elementary School (far left).

Satellite view of the tornado’s devastating path through Moore. The storm caused EF5 damage at Briarwood Elementary and areas to the west. Another patch of EF5 damage occurred at the northern crest of the damage path immediately west of the Moore Medical Center (Ortega, Burgess at al., 2013).

The Plaza Tower Elementary School before the tornado. (Image courtesy of Google Earth)

Plaza Towers Elementary School before the tornado. (Image courtesy of Google Earth)

Probable EF5 damage to Plaza Towers Elementary School and homes to the south, which were swept from their foundations. Wind rowing and ground scouring were evident throughout the damage path in Moore.

Extreme damage to Plaza Towers Elementary School and homes to the south, which were swept from their foundations. Wind rowing and ground scouring were evident throughout the damage path in Moore. A damage survey concluded that the construction standards in this area only permitted an EF4 rating, though EF5 damage likely would have occurred had a home of “superior construction” been struck.

As the tornado continued on, it curved to the north and momentarily paused just west of Telephone Road. Four people, including a mother and her infant son, were killed after taking shelter in a walk-in freezer at a 7-Eleven convenience store on the northern margin of the damage swath (a similar tragedy occurred at a Pizza Hut in Joplin, Missouri, following an EF5 tornado in 2011). On SW 6th Street, a row of well-built homes was obliterated in EF5 fashion. Across the street, the massive tornado engulfed the Moore Medical Center. The complex was severely damaged and vehicles in the parking lot were mangled beyond recognition and piled against the building’s remaining walls. Due to extensive warning and the strong construction of the building, no fatalities occurred at the medical center. A large movie theater that had been directly in the storm’s path suffered only modest damage as the tornado’s inner core made a brief curve to the north.

The Moore Medical Center was impacted directly by the probable EF5 tornado. Dozens of cars in the adjoining parking lot were piled against the structure's western wing. (Image by Steve Gooch)

The Moore Medical Center was impacted directly by the massive tornado. Dozens of cars in the adjoining parking lot were hurled against the structure’s western wing. Some vehicles nearby were damaged but largely unmoved, an indication the tornado had a violent multiple vortex structure. (Image by Steve Gooch)

At left, a tree stripped completely of bark and branches, an indication of probable EF5 winds. At right, extreme damage to the well-constructed Moore Medical Center. (Images by Brett Deering)

At left, a tree stripped completely of bark and branches. At right, extreme damage to the well-constructed Moore Medical Center. (Images by Brett Deering)

Just east of the Moore Medical Center, the tornado crossed the I-35. More than a dozen abandoned vehicles were swept off the freeway, some of which were left in a tangled mass atop the freeway divider. The tornado began to reorganize in this area and the damage path briefly widened and became more erratic in nature. Video footage and aerial imagery indicate that a narrow core of EF4 winds developed as the tornado’s path made a slight turn to the east. Homes within a streak less than 50 yards wide were obliterated as the tornado roared through subdivisions just south of 4th street.

The remains of vehicles on the I-35. (Video still by KWTV)

The remains of vehicles on the I-35. (Video still by KWTV)

In eastern Moore, the tornado narrowed and left a streak of borderline EF5 damage. (Image by Steve Gooch)

In eastern Moore, the tornado narrowed and left a streak of extreme damage less than one block wide. A damage survey later concluded that three homes were swept away in EF5 fashion east of the freeway (Ortega, Burgess et al., 2014). Pictured above is damage to homes on East Moore Court. A total of 23 people were killed directly by the tornado. (Image by Steve Gooch)

The 2013 Moore tornado caused more fatalities in Cleveland County than the 1999 Bridge Creek tornado, which killed 11 in Moore and adjacent areas. Due to the severity of the damage, the 2013 tornado was upgraded to an EF5 less than 30 hours after impacting Moore.

In terms of damage intensity, the 2013 Moore tornado was comparable to the 1999 Bridge Creek tornado. Both tornadoes left multiple instances EF5 damage in the city, but the 1999 tornado reached an even greater level of intensity in rural areas to the southwest. Mobile doppler radar was not present to analyze the 2013 tornado but it is undoubtable that velocities in excess of 250mph would have been recorded during the storm’s passage through Moore.

Graphic depicting the tracks of the 1999 and 2013 tornadoes, with red denoting areas of EF5 damage (intensity estimates for the 2013 storm are subjectively based on my experience and may differ slightly from the final NWS report). The Bridge Creek tornado was nearing the end of its intensity maxima when it reached the edge of Moore but continued causing high-end EF4 damage all the way to Midwest City (out of frame at top). The 2013 tornado, by contrast, fluctuated in strength but may have left an intermittent trail of EF5 damage up until just northeast of Plaza Towers Elementary School. The storm changed direction and narrowed significantly after crossing the I-35 but continued leaving a thin streak of extreme damage until finally weakening in eastern Moore.

Graphic depicting the tracks of the 1999 and 2013 tornadoes with red denoting areas of surveyed or probable EF5 damage (intensity estimates for the 2013 storm are subjective and may differ slightly from the final NWS report). The Bridge Creek tornado was nearing the end of its intensity maxima when it reached the edge of Moore but continued causing high-end EF4 damage all the way to Midwest City (out of frame at top). The 2013 tornado, by contrast, fluctuated in strength but left an intermittent trail of EF5 damage all the way across the city of Moore. The storm changed direction and narrowed significantly after crossing the I-35 but continued leaving a thin streak of extreme damage until finally weakening outside Moore.

Extreme damage following the 2013 Moore tornado. (Image by 1984 Studios)

Extreme damage following the 2013 Moore tornado near Westmoor. Due to extensive warning, few of Moore’s residences were above ground in the destroyed homes. The death toll of 23 was remarkably low considering the scope of the devastation. (Image by 1984 Studios)

Detailed Analysis of Videos Taken Inside the EF5 Joplin Tornado

The Joplin tornado was powerful enough to scour pavement from parking lots and rip 300lb steel-anchored parking stops from the ground. Without a doubt, the Joplin tornado caused the most intense tornado damage ever surveyed in a heavily urbanized area. In this image, empty foundations are flanked by debarked trees and lawns that have been partially scoured of grass.

□ The power of the EF5 Joplin tornado is sometimes muted against the fury of the 2011 season. While not as photogenic as the Tuscaloosa tornado three weeks before, the Joplin storm left some of the most extreme tornado damage ever documented. Engineers concluded that the winds had to be in excess of 205 mph to tear out the parking stops by St. Johns Hospital (Joplin Globe, 2011). Winds of that intensity only a few inches above the ground easily indicate winds over 250mph several feet above the ground.

The fact that the Joplin tornado spent the duration of its EF5 intensity atop a grid of homes and businesses gave meteorologists a fascinating look at the structure of an EF5 tornado. Never before had such a violent tornado destroyed so many homes. In fact, the Joplin tornado killed more people and destroyed equally as many buildings as all other EF5 tornadoes since the year 2000 combined.

The Joplin tornado maintained EF5 intensity from an area just north of St. Johns Hospital all the way to Rangeline Road. Aerial imagery indicates the tornado reached peak intensity in neighborhoods west of Joplin High School. Dozens of likely well-built homes were swept away between Pennsylvania and Iowa Avenue. The damage was remarkable considering the urban density of the area.

The tornado maintained EF5 intensity all the way to east Joplin. On Rangeline Road, there were 18 fatalities in six businesses, eight of which occurred at a Home Depot (lower left). The tornado was powerful enough to scour grass from the ground, visible here in the worst streak of damage just north of Home Depot.

The tornado was wrapped in rain and not clearly visible to those in its path, and the mesocyclone that spawned it was so immense it blackened the afternoon sky. Despite the less than perfect filming conditions, more than a dozen movies were taken in the vicinity of the tornado. The storm’s massive circulation brought hurricane force wind gusts over a wide swath of Joplin, so most of the films were recorded in the storm’s outer fringes. Only a few videos were taken inside the EF2 damage contour.

Map showing where the two

Map showing where the two “first person” Joplin films were taken. Point “A” is where the Minnesota Avenue footage was recorded. Point “B” is the location of the famous Fastrip gas station video

B. Fastrip, South Duquesne Road

“Then I heard a noise that sounded like the world was coming to an end.”

-Linda Ledford (4/3/74)

The most well-known video of the Joplin tornado was taken at a Fastrip gas station. Filmed at the intersection of 20th and Duquesne Road, the tornado was 3/4 of a mile wide and at EF4 intensity when it passed over the area. When listening to the video’s audio, it is clear the distribution of winds within the tornado was very uneven. Almost all of the damage occurred during a brief period on the backside of the storm. This may have been the result of a suction vortex imbedded within the tornado or, as some people have suggested, it may have been the back “eyewall” of the tornado after the calm center had passed.

It takes a good set of headphones to really appreciate the roar of the approaching winds, which were likely well over 200mph just above ground level. The wind feature, be it a suction vortex or the tornado’s eyewall, was deafeningly loud, yet only audible for a few seconds before impacting the Fastrip. Therefore, it was moving significantly faster than the forward motion of the tornado, which was about 20 to 25mph. This gives credence to the theory that it was a powerful suction vortex rotating within the tornado.

Using Logic Pro, I was able to sort out much of the interfering noise and focus specifically on the base sounds which constitute the “roar” of the tornado. Each point on the graph is the average base volume around each point (e.g.. the graph’s highest reading at 3″:05″ is the average of :04 – :06 and the point “:10” is the average of :09 – :11). The data indicates the winds dropped significantly inside the tornado right before the spike of highest winds. The roar of nearby winds was audible in the calm center and caused some interference, so the drop was likely even more pronounced than shown here.

The Fastrip was near the geographic center of the damage path and likely experienced the tornado’s eye. It is plausible that the winds decreased significantly, if not completely, right before the most violent winds struck. In the video, a friend of the man filming can he heard saying “We’re good, we’re good” as the audible winds dramatically decrease in the center of the tornado. Also, it appears that the extremely high winds lasted only a few seconds. Even though the overall volume increases when the roof is torn off (as the camera is directly exposed to the outside) around 3:05, the base volume, which may be indicative of the most violent winds, dramatically decreases by 3:10.

If the speed and size of the Joplin tornado were the only variables considered, it would be assumed that the Fastrip experienced peak winds for nearly two minutes. But video evidence clearly indicates otherwise. This may provide an interesting perspective on other large or slow-moving tornadoes, such as the F5 tornado that struck Jarrell, Texas on May 27, 1997.

The destroyed Fastrip is highlighted in yellow. A swath of partial vegetation scouring and wind rowing to the south of the store indicates the storm's strongest winds may have just missed the area.

The destroyed Fastrip is highlighted in yellow. A swath of partial vegetation scouring and wind rowing to the south of the store indicates the storm’s strongest winds may have just missed the area.

The people who hid in the Fastrip were incredibly lucky. A similar series of events took place at a Pizza Hut on Rangeline Road with tragic results. Approximately 15 people sought shelter in a walk-in freezer, much like at the Fastrip. The tornado was still at EF5 intensity when it crossed Range Line Road, however, and the winds ripped into the freezer and killed a third of the people inside. From survivor accounts, it appears the Pizza Hut was also struck by a brief but powerful wind feature. The store’s manager, Christopher Lucas, tied a cord around his waist in an effort to keep the freezer door closed. One survivor, who held onto Lucas’s leg, later told reporters that “everything blew away. He was gone, the door was gone, everything.” Other survivors reported watching people who were “ripped out the front and back” of the freezer. Lucas was found dead in the parking lot of a nearby business. Four other people pulled from the freezer were also killed. Some of the survivors experienced severe blunt force trauma from high velocity debris. The Pizza Hut just happened to be directly in the streak of worst damage, which was made visible by ground scouring in an area between Home Depot and Walmart.

A. 2500 Block, South Minnesota Avenue

A similar, primarily-audio film was taken with a cellphone near the Joplin High School on Minnesota Avenue. The tornado was at maximum strength as it passed by this area, and numerous instances of possible EF5 damage occurred only a few blocks to the north. The home where the footage was shot was just outside the core of extreme destruction near the F2/F3 damage contour. An audio analysis of this video was difficult due to the interference of other sounds, particularly the clatter of debris striking the home.

Even without an analysis of the base volumes, the video still provides useful information about the composition of the tornado. Damaging winds (75mph+) appear to affect the home for approximately 100 seconds, beginning at 1:30 and ending abruptly around 3:10. Most of the damage, however, occurs during two distinct bursts, each lasting less than 10 seconds. During the first burst (at 2:12), flying debris can be heard impacting the home and several loud thuds indicate the home’s roof had begun to fail. Loud clinking sounds are audible as the entire home shakes as if struck by an earthquake. Around 2:35 a second, stronger rush of winds strike the home, likely causing most of the structural damage. Near the end of the storm, the window in the bathroom shatters, an indication winds had shifted as the tornado’s center moved to the east. A third pocket of intense winds roars above the home for a few moments before the storm subsides.

The home where the Minnesota Avenue film was taken was right at the EF2/EF3 damage contour, near the edge of the tornado's path. Most, if not all of the approximately 80 fatalities that occurred in frame homes were in the EF4 and EF5 damage zones.

The home where the Minnesota Avenue film was taken was right at the EF2/EF3 damage contour, near the edge of the tornado’s path. Most, if not all of the approximately 70 fatalities that occurred in frame homes were in the EF4 and EF5 damage zones.

The Minnesota Avenue videographer was just outside the area where the tornado’s most extreme wind features were causing EF4 and EF5 damage. The evenly spaced periods of wind acceleration may have been related to the home’s proximity to intense multiple vortices that passed only a few hundred feet to the north. The exact make-up of the tornado may never be known, but the videographer in the Fastrip on Duquesne Road encountered a brief, violent wind feature that the filmmakers on Minnesota Avenue did not experience.

The film taken on Minnesota Avenue was just south of Joplin High School’s athletic fields (one block out of frame). The tornado’s most intense damage occurred only a few hundred feet to the north. Dozens of homes to the west of the high school were swept completely away.

Both videos provide evidence that supports the notion that many violent tornadoes have small, extremely powerful wind features that cause the most intense damage. The Joplin videos indicate that the tornado had a wide swath of powerful winds capable of causing EF1 to EF3 damage, and small-scale vortices that caused EF4 and EF5 damage. While the exact winds will never be known, they were likely significantly more powerful than 210mph cap the Enhanced Fujita Scale appears to utilize.