Fast Facts for the
Great Plains Tornado Outbreak of May 3-4, 1999
- A total of 58 tornadoes occurred in the NWS Norman forecast area in central and southwestern Oklahoma during afternoon and evening hours of May 3, 1999.
- Of the 58 tornadoes that occurred in the NWS Norman area on May 3rd, 1 was rated F5 and 2 were rated F4, giving a total of 3 violent tornadoes for the outbreak. Another 6 tornadoes were rated F3 and 7 were rated F2, making a total of 13 strong tornadoes for this event. A total of 42 tornadoes were in the weak category, with 14 being rated F1 and another 28 tornadoes rated as F0.
- An additional 5 tornadoes occurred in the NWS Tulsa forecast during the late evening hours of May 3rd and the early morning hours of May 4th, making the total of 63 tornadoes the largest outbreak of tornadoes for Oklahoma since official records began in 1950.
- The Tornado Emergency issued by the NWS Norman forecast office for the OKC metro area during the evening of May 3rd was the first warning of its kind. With a large, violent tornado on the ground heading into the most populous center in the state of Oklahoma, the forecast office staff wanted to convey the message that would grab people's attention and let them know that this event was something different than normal.
Severe Weather Safety Information
News Articles, Papers, and Research Related to the May 3-4, 1999 Event
Storm Prediction Center
National Weather Service
Other Research and Data
Tornado Data and Information
- List of F5/EF-5 Tornadoes in the United State Since 1950 (Storm Prediction Center)
- Top Ten Costliest Oklahoma Tornadoes (1950-Present)
- Top Ten Deadliest Oklahoma Tornadoes (1875-Present)
- Quick List of F5/EF-5 Tornadoes in Oklahoma (1905-Present)
- Detailed List of Violent Tornadoes in Oklahoma (1950-Present)
- Detailed List of Killer Tornadoes in Oklahoma (1950-Present)
- Blaine County, OK Tornadoes (1875-Present)
- Caddo County, OK Tornadoes (1875-Present)
- Canadian County, OK Tornadoes (1875-Present)
- Comanche County, OK Tornadoes (1875-Present)
- Cleveland County, OK Tornadoes (1875-Present)
- Grady County, OK Tornadoes (1875-Present)
- Kingfisher County, OK Tornadoes (1875-Present)
- Lincoln County, OK Tornadoes (1875-Present)
- Logan County, OK Tornadoes (1875-Present)
- McClain County, OK Tornadoes (1875-Present)
- Pottawatomie County, OK Tornadoes (1875-Present)
- Comprehensive List of Tornadoes in Oklahoma City since 1890.
- Tornadoes that have occurred in or near Chickasha, OK (1875-Present)
- Tornadoes that have occurred in or near El Reno, OK (1875-Present)
- Tornadoes that have occurred in or near Kingfisher, OK (1875-Present)
- Tornadoes that have occurred in or near Moore, OK (1875-Present)
- Tornadoes that have occurred in or near Shawnee, OK (1875-Present)
- Oklahoma City Area Tornadoes of June 13, 1998 The Oklahoma City metropolitan area had not seen any tornadoes since October 1992 when a supercell thunderstorm dropped three tornadoes in Canadian County and four more tornadoes over the northern Oklahoma City metro area.
- The October 4, 1998 Tornado Outbreak Twenty-eight tornadoes occurred in central and eastern Oklahoma, including an F2 tornado which damaged parts of Moore. It was the largest autumnal outbreak of tornadoes ever recorded in Oklahoma.
- Oklahoma City Area Tornadoes of May 8, 2003 The central United States experienced a record-breaking week of tornadoes from May 4 through May 10, 2003, when nearly 400 tornadoes occurred in 19 states and caused 42 deaths during the seven days. Included in this total were the tornadoes which hit the southern Oklahoma City metropolitan area on May 8, 2003 including an F4 tornado which tore through parts of Moore, Oklahoma City and Choctaw.
- Oklahoma City Area Tornadoes of May 9, 2003 One day after an F4 tornado struck the southern Oklahoma City metropolitan area, a single supercell thunderstorm produced ten tornadoes in central Oklahoma, including one F3 and two F1 tornadoes in the northern Oklahoma City metropolitan area.
- The May 10, 2010 Tornado Outbreak This outbreak produced 35 tornadoes in the NWS Norman forecast area alone, and a total of 55 tornadoes in Oklahoma. Two EF4 tornadoes struck the Oklahoma City metro area including Moore, killing 3 people and injuring over 80 others.
- The May 24, 2011 Tornado Outbreak While this outbreak included only 12 tornadoes in the NWS Norman forecast area, 3 of these were violent (1 EF5 and 2 EF4s). The killer tornado that went through Canadian, Kingfisher and Logan Counties was the first F5/EF5 tornado in Oklahoma since the May 3, 1999 outbreak.
- The May 19, 2013 Tornado Outbreak Two supercells in central Oklahoma also produced a total of 8 tornadoes, including one violent tornado that hit parts of Cleveland and Pottawatomie Counties.
- The May 20, 2013 Tornado Outbreak An outbreak of 15 tornadoes occurred in parts of central and eastern Oklahoma. A violent, EF5 tornado struck parts of McClain and Cleveland Counties, including the cities of Newcastle, south Oklahoma City and Moore and killed a total of 24 people. Damage estimates were $2 billion, making this the most costly tornado to ever occur in Oklahoma.
- The May 31-June 1, 2013 Tornado and Flash Flood Event in Central Oklahoma This was the final event in a two-week period of devastating tornadoes and severe weather in late May 2013 that plagued the region. A cluster of supercell thunderstorms impacted central Oklahoma, including the OKC metro area. A total of 19 tornadoes occurred, including the El Reno tornado, which killed 8 people. In addition to the tornado, heavy rains led to flash flooding in the metro area, and claimed another 13 lives, making it one of the most deadly flash flood events to ever occur in Oklahoma City.
Frequently Asked Questions
Q: Was the Bridge Creek/Moore/OKC area tornado on May 3, 1999, rated F6?
A: No. The tornado has been rated F5 (minimal F5, in fact), and will not be "upgraded" to F6.
There was some speculation in the media of an F6 rating after "Doppler on Wheels" (DOW) researchers announced that their radar measured 318-mph winds in the tornado while it was near Bridge Creek. However, the jump in reasoning to rating this tornado F6 can not be made, for many reasons:
- F-scale ratings are assigned based on the severity of the damage caused, *not* on wind speed. Although some of the damage was incredible (as it is with any F5 tornado), the most severe damage from the May 3 tornado was comparable to, but not worse than, other documented F5 tornadoes.
- Wind speeds used in the F scale have not been scientifically calibrated to the severity of damage that defines each F scale level. They are, essentially, only estimates.
- Even if the F-scale wind speed ranges were reliable estimates, the DOW measurement of 318 mph is still in the F5 range (261-318 mph) as defined by Dr. Fujita.
- The data obtained by the DOW team are still in the process of being reviewed scientifically, and so the validity of the 318-mph wind measurement is still open to some question at this point. Early results of this review process suggest that the maximum speed actually may be less than 318 mph (although it likely will remain above 300 mph).
- In reality, there is no such thing as an F6 tornado. When Dr. Fujita developed the F scale, he created a scale that ranges from F0 to F12, with estimated F12 winds up to mach 1 (the speed of sound). But he added that "tornadoes are not expected to reach F6 wind speeds." This leaves only the F0 to F5 range as the actual tornado F scale. For a tornado to be given an unprecedented F6 rating, it would have to produce damage more severe than has ever been observed. As stated above, there was nothing unusual or unprecedented in the damage from the May 3 tornado as compared with other F5 tornadoes in the past.
Q: Was the May 3 tornado the strongest, most violent tornado ever?:
A: Probably not, but we really have no way of knowing. It is impossible to make direct, objective comparisons between the May 3 tornado and most other violent tornadoes of the past. Factors such as inflation, varying population and property density over time and space, and the lack of direct wind speed measurements from all but a very few other tornadoes, prevent such comparisons.
We do know that other tornadoes have been wider, many have been more deadly, some have been longer lived, and many have produced longer damage tracks. So the May 3 tornado was *not* the "biggest" tornado. Nor was it the widest, the deadliest, the longest lived, or the longest track tornado on record.
The May 3 tornado currently is the most expensive tornado ever recorded. The damage estimate (roughly $1 billion) exceeds that of all other past tornadoes, even when inflation is taken into account. If we adjust our damage figures from other violent tornadoes in the past to account for inflation, we find that several (Lubbock,TX - May 11, 1970; Omaha, NE - May 6, 1975; Wichita Falls, TX - April 10, 1979, to name a few) were very close to the May 3 tornado in terms of dollar amount of damage. But to make such comparisons truly representative, we must also account for population growth, and the fact that people generally own more today than they used to. (So not only is property worth more today, but there also is more of it.) It's impossible to adjust for these factors objectively, and hard to even estimate their impact. But efforts to account for these factors suggest that the May 3 tornado probably was *not* the most damaging, at least in terms of material losses.
The May 3 tornado likely does have the highest recorded tornado wind speeds. But since typical wind measuring equipment does not survive a strong tornado, there are about three dozen tornadoes on record from which wind speeds have been obtained. Those measurements usually have been obtained from special research projects, such as the Doppler on Wheels (DOW) project, and have been obtained from only a dozen or so tornadoes (less than 0.1 percent of all tornadoes). So while the DOW data indicate the highest *recorded* tornado wind speed, there have been tens of thousands of tornadoes throughout history for which no wind speeds were ever obtained. Some of them easily could have had stronger winds than the May 3 tornado.
Without wind measurements, tornado wind speeds can only be estimated by examining the damage that was done. If we compare damage caused by the May 3 tornado with that of other tornadoes in the past, we find that several other F5 tornadoes have produced damage comparable to, or even more severe than, the May 3 tornado. Some famous examples of other F5 tornadoes that produced comparable or worse damage - and therefore may have been stronger than the May 3 tornado - include the "Tri-state" Tornado of March 18, 1925, the Woodward, OK tornado of April 9, 1947, the Xenia, OH tornado of April 3, 1974, and the Andover, KS tornado of April 26, 1991.
It's also important to know that although the tornado was rated F5, very few areas affected by this tornado actually experienced F5 damage. There were only a few small, narrow areas near the center of the damage path where intermittent F5 damage was found: in the Bridge Creek area (Grady County), and in a few parts of south Oklahoma City and Moore (Cleveland County). This is less than 1 percent of the approximately 15 square miles of damage that this tornado produced. The maximum damage in Oklahoma and McClain Counties was rated F4 (which, of course, is still very devastating damage).