- Yesterday's powerful tornado in suburban Oklahoma City loosely followed the path of a killer twister that slammed the region in May 1999.
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, killing at least two people.
Kelsey Angle, a National Weather Service meteorologist in Kansas City, Mo., 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.
The weather service has tentatively classified the Moore twister's wind speeds as an EF4 on a 5-point scale. Angle said less than 1 percent 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 2 1/2 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.
The deadliest tornado, which struck in 1925, killed 695 people in Missouri, Illinois 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.
Historically, the 10 deadliest tornadoes in the United States since 1900 are:
* 695 deaths. March 18, 1925, in Missouri, Illinois and Indiana.
* 216 deaths. April 5, 1936, in Tupelo, Miss.
* 203 deaths. April 6, 1936, in Gainesville, Ga.
* 181 deaths. April 9, 1947, in Woodward, Okla.
* 158 deaths. May 22, 2011, in Joplin, Mo.
* 143 deaths. April 24, 1908, in Amite, La., and Purvis, Miss.
* 116 deaths. June 8, 1953, in Flint, Mich., and surrounding areas.
* 114 deaths. May 11, 1953, in Waco, Texas.
* 114 deaths. May 18, 1902, in Goliad, Texas.
* 103 deaths. March 23, 1913, in Omaha, Neb.