The powerful tornado that tore apart suburban Oklahoma City Monday loosely followed the path of a killer twister that slammed the region in May 1999.
The National Weather Service estimated that the storm that struck Moore, Okla., on Monday had wind speeds of up to 200 mph and was at least a half-mile wide.
The 1999 storm had winds clocked at 300 mph, according to the weather service website, and it destroyed or damaged more than 8,000 homes. It killed 42 people in Moore and central Oklahoma.
The 1999 twister was part of a two-day outbreak sweeping mostly across central Oklahoma -- similar to the past two days.
The weather service has tentatively classified the Moore twister's wind speed as an EF-4 on a 5-point scale. Angle said less than 1 percent of all tornadoes reach EF-4 or EF-5, the highest.
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 21/2 miles wide at its peak width, which the weather service describes as near the maximum size for a tornado. It struck Hallam, Neb., in May 2004.
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.