The Environment
An upper level low was located over South Dakota with winds of 45 kts over Norman, OK (per the 12z (7am CDT) analysis). At the surface, a stationary front was located to the west of Norman during the same time period. Temperatures were already in the lower 70’s with dew points in the middle 60’s. By 18z (1pm CDT), the surface temperatures were in the 80’s with dew points in the 70’s. With the combination of a dryline, a stationary front, CAPE values up to 5000 J/kg and wind shear made the atmosphere ripe for tornadoes. This atmosphere produced the Moore, OK EF-5 tornado.
For our fellow weather geeks, below is the 12z (7am CDT) observed sounding for OUN (Norman, OK):
In case you aren’t aware of what a sounding is, it’s observations throughout the atmosphere. On the left plot, red line is temperature and the green line is dew point. This can get us information such as how much CAPE (energy) is in the atmosphere, how low the cloud base will be, etc. In addition, wind barbs (located on the right side of the plot on the left) tell us wind shear. The hodograph (upper left plot) shows us the wind shear as well, but from a different perspective.
Moore Tornado Touchdown: McClain County
This tornado touched down initially just south of Highway 37 at 2:56pm CDT bringing structural damage to one house and multiple trees. Along this segment the winds were estimated to be consistent with EF-1 damage. As the tornado crossed Highway 37, within about a mile of the initial touchdown point, it moved over a subdivision where multiple homes were destroyed, doing up to EF-4 damage to 2 homes. At 3:01pm CDT, the National Weather Service in Norman, OK issued a rare Tornado Emergency, including parts of Southern OKC and Moore. The tornado maintained intensity as it crossed the river into Cleveland County. It had moved two areas of a highway bridge, over 700 yards in length from their concrete pillars.
Becoming Violent: Moving Toward Moore
The tornado continued to intensify and widen to a width of up to 1 mile wide, over rural sections of Cleveland County. There was little damage done in this segment due to a low number of structures in this area. The tornado continued to move east, and sections of ground scouring was noted. The tornado moved over a oil drill and storage area, where 5 oil tanks were moved; one was thrown over a mile from the original location. Winds here were estimated to be up to EF-4 intensity. An extremely well defined hook was evident on KTLX radar as it was moving into Cleveland County. The large “debris ball” in reflectivity and the low CC clearly indicated that the tornado was doing lofting vast amounts of debris into the air.
EF-5 Damage and Briarwood Elementary School
The violent tornado continued and crossed Western Avenue at 3:12pm CDT. Several buildings were destroyed. Two large fuel tanks, both weighing up to 10 tons, were thrown up to a distance close to 1/2 mile. The tornado continued from here, moving eastward, hitting the Briarwood Elementary school. The two wings of the school were completely destroyed along this segment. Maximum intensity from Western Avenue up to Briarwood Elementary was rated a high-end EF-4. In the Westmoore housing area – which is east of the school, the tornado produced a large swath of EF-4 damage. In addition, a smaller area of EF-5 damage was sustained to two houses. It was in this housing area that the first fatalities occurred.
Plaza Towers Elementary to Warren Theater
Maintaining up to EF-4 intensity, the tornado continued to the ENE leveling multiple homes to their foundations. A swath of EF-4 damage moved through the Santa Fe Plaza neighborhood. Tree debarking, ground scouring and intense debris granulation were evident as well. The tornado hit Plaza Towers Elementary school at EF-4 strength. Sadly, between the Santa Fe Plaza neighborhood, and the Plaza Towers Elementary School the highest concentration of fatalities occurred. Seven occurred in the school and nine in the neighborhood. Shortly after the tornado hit the school, it began to narrow and passed through a pasture. The tornado passed over a neighborhood just to the South of the Moore Medical Center, doing EF-5 damage to four homes. It was here that the tornado made a distinct loop. A convenience store was destroyed with three fatalities. Shortly after looping, the tornado hit the Moore Medical Center at EF-4 intensity. Multiple cars were thrown with one thrown more than a block from its original location. Another landed on top of the two-story medical center. It was here that the radar was showing an extremely large debris signature.
I-35 to Tornado Dissipation
The tornado maintained EF-4 intensity as it moved over I-35, but still continued to narrow. Two homes were rated an EF-5. The tornado also picked up in forward speed to just over 30mph as it moved over the southern end of Highland East Junior High, which was destroyed at EF-4 strength. Lockers were thrown a considerable distance. The tornado moved out of the more populated areas of Moore and hit a few rural homes. One house sustained EF-5 damage on S. Air Depot road. Here, a vehicle was thrown over 100 yards. The tornado weakened, and dissipated near a tree line at 3:35pm CDT.
The Track and Summary
This tornado was on the ground for 40 minutes and had a path length of 14 miles. 24 fatalities, and over 200 injuries were a direct result of this tornado. The maximum width was over 1 mile. Over 4000 structures were damaged or destroyed.
Sources:
https://www.weather.gov/oun/events-20130520
https://journals.ametsoc.org/doi/10.1175/WAF-D-14-00039.1
http://www.spc.noaa.gov/exper/archive/event.php?date=20130520
http://www.wpc.ncep.noaa.gov/html/sfc-zoom.php
Radar snapshots from archived event from Caleb Routt
Caleb Routt was a contributor to this article: 21 year old Caleb Routt is from Kentucky and has had a passion for severe storms, and especially tornadoes and their fluid dynamics since he was 7 years old. The infamous March 2nd 2012 tornado outbreak had a huge impact on him, studying everything there is to know about the tornadoes in the mountains of Eastern Kentucky. Caleb is currently in community college as of now but soon will be going to Western Kentucky University where he plans to get a degree in meteorology to live his dream!
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