Oklahoma City's latest deadly tornado roughly followed the path of a killer twister that slammed the region in May 1999.
The National Weather Service estimates the storm that struck Moore, Oklahoma, on Monday had wind speeds of up to 320km/h, and was at least 800 meters wide.
The 1999 storm had winds clocked at 480km/h, according to the weather service website, and it destroyed or damaged more than 8000 homes, killing at least two people.
Kelsey Angle, a weather service meteorologist in Kansas City, Missouri, said it's unusual for two such powerful tornadoes to track roughly the same path.
The 1999 twister was part of a two-day outbreak sweeping mostly across central Oklahoma - similar to the past two days.
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The weather service has tentatively classified the Moore twister's wind speeds as an EF4 on a 5-point scale. Angle said less than one per cent of all tornadoes reach EF4 or EF5.
The thunderstorm developed in an area where warm moist air rose into cooler air. Winds in the area caused the storm to rotate, and that rotation promoted the development of a tornado.
The most destructive and deadly tornadoes develop from rotating thunderstorms.
The biggest known tornado was nearly four kilometres wide at its peak width, which the weather service describes as near the maximum size for a tornado.
It struck Hallam, Nebraska, in May 2004.
The deadliest tornado, which struck March 18, 1925, killed 695 people in Illinois, Missouri and Indiana.
Deaths from twisters have been declining in recent years because of improved forecasts and increased awareness by people living in tornado-prone areas, especially in smaller and rural communities.
