By Chris Francescani
NEW YORK, May 19 (Reuters) - A tornado half a mile wide struck near Oklahoma City on Sunday, part of a massive storm front that hammered the central United States. News reports said at least one person had died.
By early Sunday evening, 19 tornados had touched down in parts of Iowa, Oklahoma and Kansas, according to the National Weather Service and local news reports.
Fox News reported that one person was killed in Shawnee, Oklahoma, east of Oklahoma City.
Police in Shawnee could not immediately be reached to confirm the report.
Officials of the National Weather Service in Oklahoma issued a series of increasingly urgent warnings in the late afternoon and evening, including an alert on Twitter about a tornado striking Pink, a town on the edge of Oklahoma City.
"Large tornado west of Pink!" the post read. "Take cover RIGHT NOW in Pink! DO NOT WAIT!"
An extreme weather system stretching from north Texas to Minnesota had been building for hours on Sunday when a "large tornado" touched down near Wichita, Kansas at 3:45 pm Central Standard time, according to a weather service alert.
Another alert warned of the likelihood of "exceptionally powerful, severe thunderstorms capable of destructive hail as large as baseballs," especially over southeast Kansas in the evening.
Kansas, Missouri, Oklahoma, Nebraska and Iowa are all in the path of the storm system capable of producing winds of up to 80 miles per hour, large hail stones and violent tornadoes.
The storm prompted an unusually blunt warning from the central region of the National Weather Service, which covers 14 states.
"You could be killed if not underground or in a tornado shelter," it said. "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, spokesman for the National Weather Service for the U.S. Central region.
In northeast Oklahoma, the Lincoln County sheriff's office reported three tornado touchdowns in that region, NBC News said reported early on Sunday evening.
Slattery said the potential severity of the storm prompted the weather service to issue the stark advisory, which is part of a new warning system being tested in the U.S. Central region after a violent tornado that struck Joplin, Missouri on May 22, 2011, killing 158 people and injuring hundreds.
Slattery said the new advisory was reserved for severe tornadoes with the potential to form into "supercell" storms, which produce powerful winds and flash flooding. Supercells 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, Richard Chang and David Brunnstrom)