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Violent tornado devastates Moore, Oklahoma

By: Dr. Jeff Masters, 12:48 AM GMT on May 21, 2013

A massive and violent tornado at least a mile wide smashed through Moore, Oklahoma near 3 pm CDT Monday, causing catastrophic damage along a 20-mile long path. The National Weather Service in Norman, Oklahoma has rated the tornado at least an EF-4 (166 - 200 mph winds), and detailed damage surveys may upgrade this rating to the top-end EF-5 level in the coming days. Damage was extreme and covered a huge area, and many buildings swept away down to their foundations. The tornado was on the ground for 40 minutes, from 2:56 - 3:36 pm CDT, and a tornado warning for the storm was issued at 2:40 pm CDT, sixteen minutes before it touched down. The debris ball from the tornado, as seen on Doppler radar, expanded to over two miles in diameter, and debris was carried over 100 miles from Moore. The National Weather Service office in Tulsa, Oklahoma reported at 4:13 pm CDT that they were "seeing reports of light tornado debris falling in the Tulsa metro area again this evening, likely from the Moore area." Tulsa is 100 miles east-northeast of Moore.

Figure 1. The news helicopter from kfor.com caught this image of the shocking near-total destruction of a huge area of Moore, Oklahoma, on May 20, 2013.

Figure 2. Radar reflectivity image taken at 3:06 pm CDT May 20, 2013 of the supercell thunderstorm that spawned the Moore, Oklahoma tornado. A classic "hook echo" terminates in a sphere of colors with high-reflectivity purple at its core, the signature of a "debris ball" of debris hurled into the air by a violent tornado.

Figure 3. Terminal Doppler Weather Radar velocity image taken at 3:06 pm CDT May 20, 2013 of the supercell thunderstorm that spawned the Moore, Oklahoma tornado. Note the couplet of dark red colors right next to dark blues, showing that the air was moving both towards the radar and away from it within a short distance, indicating a tight rotation of the tornado's parent mesocyclone. The velocity folding inside this couplet is extremely unusual to see in Doppler radar data and shows that the winds were so fast, the radar misidentified their speed. This, along with the extremely low beam height (0.5°), suggests that the radar was scanning the upper parts of the tornado and its immediate environment. Thanks go to wunderground's tornado expert, Dr. Rob Carver, for annotating this image.

Moore tornado likely to be one of the five most damaging tornadoes in history
Moore has the unenviable distinction of having previously experienced the 4th costliest tornado in world history, the notorious May 3, 1999 Bridgecreek-Moore EF-5 tornado. There have been only six billion-dollar (2011 dollars) tornadoes in history:

1) Joplin, Missouri, May 22, 2011, $2.8 billion
2) Topeka, Kansas, June 8, 1966, $1.7 billion
3) Lubbock, Texas, May 11, 19780, $1.5 billion
4) Bridge Creek-Moore, Oklahoma, May 3, 1999, $1.4 billion
5) Xenia, Ohio, April 3, 1974, $1.1 billion
6) Omaha, Nebraska, May 6, 1975, $1 billion

The May 3, 1999 Bridge Creek-Moore tornado killed 36 people and injured 583. It damaged or destroyed 8132 homes, 1041 apartments, 260 businesses, 11 public buildings and seven churches. According to rough estimates of the size of the damaged area made by helicopters operated by news9.com and kfor.com, the damage footprint from the May 20, 2013 tornado is easily twice as large. I expect that after the damage tally from the May 20 tornado is added up, Moore will hold two of the top five spots on the list of most damaging tornadoes in history, and the May 20 tornado may approach the Joplin tornado as the costliest twister of all-time.

Figure 4. Comparison of the tracks of the May 3, 1999 and May 20, 2013 tornadoes in Moore, Oklahoma. Both tornadoes caused near-total destruction along a significant portion of their paths. Image credit: ‪NWS Norman, #Okwx‬ ‪pic.twitter.com/4BmUWIyNbo‬

Video 1. Short storm chaser clip of the May 20, 2013 Moore, Oklahoma tornado. The video is notable for the large amount of flying debris seen swirling around the funnel.

I urge you to give generously to the victims of this tragedy, whether through your monetary donations to disaster relief organizations like redcross.org or portlight.org, or with your prayers to those afflicted.

Jeff Masters


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.