1999 Oklahoma tornado outbreak

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1999 Oklahoma tornado outbreak
Clockwise from top: Satellite image of supercells developing across central Oklahoma late on May 3; a tornado near Anadarko, Oklahoma; tracks of all the tornadoes spawned by the outbreak in Oklahoma; radar reflectivity image of the the F5 tornado that impacted Bridge Creek and Moore
Meteorological history
DurationMay 2–8, 1999
Tornado outbreak
Tornadoes152
Maximum ratingF5 tornado
Duration6 days, 1 hour and 35 minutes
Highest windsTornadic – 321 mph (517 km/h)
(Southwest Oklahoma City, OK F5 tornado on May 3) [1][2]
Highest gustsNon-tornadic – 115 mph (185 km/h) (Claxton, TN non-tornadic on May 7)[3]
Largest hail4.5 in (11 cm) in diameter (multiple locations on May 3)[4]
Overall effects
Fatalities50 fatalities (+7 non-tornadic)
Injuries895
Damage$1.5 billion (1999 USD)[5]
Areas affectedMidwestern, Southern United States, Great Plains

Part of the Tornado outbreaks of 1999

The 1999 Oklahoma tornado outbreak was a large, historic,[6] and devastating tornado outbreak that took place across much of the Central United States, with most tornadoes occurring from May 2–5, 1999; scattered activity occurred afterwards until May 8 in parts of the Eastern United States, as well as southern Canada. During this week-long event, 152 tornadoes touched down in these areas. The most dramatic events unfolded during the afternoon of May 3 through the early morning hours of May 4 when more than half of these storms occurred. Oklahoma experienced its largest tornado outbreak on record from this event, with 70 confirmed. The most notable of these was the F5 Bridge Creek–Moore tornado which devastated Oklahoma City and suburban communities. The tornado killed 36 people and injured 583 others; losses amounted to $1 billion, making it the first billion-dollar tornado in history.[7] Overall, 50 people lost their lives during the outbreak and damage amounted to $1.4 billion.[8]

On May 2, a strong area of low pressure moved out of the Rocky Mountains and into the High Plains, producing scattered severe weather and ten tornadoes in Nebraska. The following day, atmospheric conditions across Oklahoma became significantly more favorable for an outbreak of severe weather. Wind profiles across the region strongly favored tornadic activity, with the Storm Prediction Center stating, "it became more obvious something major was looming" by the afternoon hours.[9] Numerous supercell thunderstorms developed across the state as well as bordering areas in Kansas and Texas. Over the following 48 hours, May 3–4, 116 tornadoes touched down across the Central United States. Following the extensive outbreak, activity became increasingly scattered from May 5 to 8, with 26 tornadoes touching down across the Eastern United States and Quebec.[9]

In 2023, tornado expert Thomas P. Grazulis published the outbreak intensity score (OIS) as a way to rank outbreaks.[6] The outbreak received 145 OIS points, ranking it as a historic tornado outbreak.[6]

  1. ^ "Flexible Array of Radars and Mesonets (FARM) statement concerning preliminary peak wind speed determinations based on Doppler On Wheels (DOW) data obtained in the Greenfield, Iowa tornado of 21 May 2024 section more detail" (PDF). Flexible Array of Radars and Mesonets facility. June 23, 2024.
  2. ^ "Doppler On Wheels". May 3, 1999. Archived from the original on February 5, 2007. Retrieved June 13, 2013.
  3. ^ "Tennessee Event Report: Thunderstorm Wind". National Climatic Data Center. National Oceanic and Atmospheric Administration. 2013. Retrieved June 9, 2013.
  4. ^ "Storm Events Database: May 2–8, 1999 Hail 4.00 in and Larger". National Climatic Data Center. National Oceanic and Atmospheric Administration. 2013. Archived from the original on March 4, 2016. Retrieved June 9, 2013.
  5. ^ "Storm Events Database: May 2–7, 1999 Tornadoes". National Climatic Data Center. National Oceanic and Atmospheric Administration. 2013. Archived from the original on March 4, 2016. Retrieved June 9, 2013.
  6. ^ a b c Grazulis, Thomas P. (2023). Significant Tornadoes 1974–2022. St. Johnsbury, Vermont: The Tornado Project. p. 637. ISBN 978-1-879362-01-7.
  7. ^ "The Great Plains Tornado Outbreak of May 3–4, 1999". National Weather Service Office in Norman, Oklahoma. National Oceanic and Atmospheric Administration. June 22, 2011. Retrieved June 4, 2013.
  8. ^ "Storm Events Database: May 2–7, 1999 Tornadoes". National Climatic Data Center. National Oceanic and Atmospheric Administration. 2013. Archived from the original on March 4, 2016. Retrieved June 6, 2013.
  9. ^ a b "Meteorological Summary of the Great Plains Tornado Outbreak of May 3–4, 1999". National Weather Service Office in Norman, Oklahoma. National Oceanic and Atmospheric Administration. May 3, 2010. Retrieved June 4, 2013.

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