By Chris Francescani
NEW YORK (Reuters) - A dangerous, half mile-wide tornado struck near Oklahoma City Sunday afternoon, part of an extreme weather system moving through the central U.S. and stretching from north Texas to Minnesota.
Earlier, a "large tornado" touched down near Wichita, Kansas at 3:45 Central Standard time, the National Weather Service reported.
Kansas, Missouri, Oklahoma and Nebraska are all in the path of the storm system, which is producing 70 mile per hour winds, baseball-sized hail and violent tornadoes.
The storm is so large and severe it prompted an unusually blunt National Weather Service warning.
"You could be killed if not underground or in a tornado shelter,'' the advisory reads. "Complete destruction of neighborhoods, businesses and vehicles will occur. Flying debris will be deadly to people and animals."
A tornado also touched down in southwest Wichita at 3:45 p.m. Central time, moving northeast at about 35 miles per hour toward Topeka, said Pat Slattery, National Weather Service spokesman for the U.S. Central region, which covers 14 states.
Slattery said the potential severity of the storm prompted the weather service to issue the stark advisory, which is part of a new "impact-based warning system" being tested in the U.S. Central region, in the wake of a violent tornado that struck Joplin, Missouri on May 22, 2011, killing 158 and wounding hundreds more.
Slattery said the new, more urgent advisory is reserved for severe tornadoes with the potential to form into super cell storms, which produce powerful winds and flash flooding. Super cells are considered to be the most dangerous of four categories of storms because of the extreme weather they generate.
A recent National Oceanic and Atmospheric Administration assessment of the Joplin storm found that "when people heard the first tornado warning, they did not immediately seek shelter. They looked for a secondary source to confirm the tornado," Slattery said. "That got some people killed."
(Reporting By Chris Francescani; Editing by Theodore d'Afflisio and David Storey)
(This story is refiled to correct lead of 19th May story to read "tornado," not "hurricane")