NewsHour correspondent Kwame Holman begins our report.

　　KWAME HOLMAN:The image of the huge twister filled the TV screen, as it bulldozed farmland and subdivisions and flashes from exploding transformers dotted the blue-black horizon.

　　MAN:Oh, there's a huge flash right there. It is just ripping up everything in its path.

　　KWAME HOLMAN:In Oklahoma City, state lawmakers and employees alike quickly made their way to a basement shelter. Some 35 to 40 minutes later, the great cloud finally spent its fury and disintegrated.

　　In its wake, mile after mile of devastation south and southwest of Oklahoma City proper -- scores of homes and other buildings had been leveled, including an elementary school. Cars and trucks were smashed together on highways.

　　MAN:Oh, my gosh. I don't know if people lived in that one.

　　KWAME HOLMAN:And fires burned out of control. Part of a major interstate highway was shut down.

　　The suburb of Moore also was hit hard by a tornado in 1999, and today's storm came less than 24 hours after another tornado struck in the Oklahoma City area.

　　MAN:I had to stop because the winds were pushing my truck, and I had to slow down to about 10 miles an hour. And I was texting actually the lady I work with, and I told her, man, these are the craziest winds I have ever seen.

　　KWAME HOLMAN:Sunday's twister touched down outside Shawnee, killing two elderly men and injuring more than 30 people. Other twisters touched down Sunday in Kansas and Iowa.

　　WOMAN:We jumped up and ran into the shed. And once we got the door shut, we heard the roof take off.

　　KWAME HOLMAN:All of this came less than a week after twisters pummeled Texas, killing six people in the small city of Granbury, southwest of Fort Worth.

　　JEFFREY BROWN:Moments ago, I spoke by phone with Sgt. Gary Knight of the Oklahoma City Police Department.

　　Sgt. Knight, welcome.

　　What can you tell us at this point about the extent of the damage?

　　MASTER SGT. GARY KNIGHT, Oklahoma City Police Department: Well, there's areas of south Oklahoma City and Moore that have suffered total destruction or extreme devastation.

　　Moore sits on the south end of Oklahoma City. They sit adjacent to each other. And the tornado traveled through Moore and then moved northeasterly into southern Oklahoma City. There's a two- or three-mile area where there was just utter devastation. I don't have any numbers on injured people or if there are fatalities involved in this.

　　Our workers are still trying to get to many people who are trapped in those areas. Really, our message for the public is, for anybody in that area, please stay off the roadways. Stay out of the areas to let emergency workers in. I know they're having difficulty getting around everybody, plus getting around all of the debris that's in the roadway.

　　JEFFREY BROWN:I understand you don't have any sense of fatalities or injuries at this point, but do you have a sense of how many people—were there a lot of people in the path of the tornado?

　　GARY KNIGHT:There were numerous neighborhoods in the path of the tornado that were just completely leveled. So that's certainly something that we're trying to address and get into those places, just as the Moore police and all the first-responders in that area are trying to get in there and do everything they can to assist anyone who is trapped or injured.

　　JEFFREY BROWN:Do you know how much warning people had?

　　GARY KNIGHT:There was a good amount of warning. The local television stations here—I mean, obviously, they're very good at tornado forecasting, being in this part of the country.

　　But they were covering the tornado as it came down out of the sky, and were letting people know as soon as possible. I know the tornado sirens were sounding, but it was a very fast-developing storm, a fast-developing tornado. And, unfortunately, it moved through a heavily populated area.

　　JEFFREY BROWN:Well, that's what I was going to ask you, just to describe the area a little bit more, heavily populated. You referred to various neighborhoods. So this is a suburban area where—homes, schools, everything, right?

　　GARY KNIGHT:Well, it would have been a suburban area.

　　There are some businesses that were struck. It crossed I-35 and it's to the areas just east of Interstate 35 that would have been hardest-hit. There are some businesses along I-35 that were struck. And then you move into neighborhoods where there was at least one school, one elementary school that was struck and suffered severe damage to it.

　　I don't have any numbers again on injured, but mostly neighborhoods. There were some businesses, but mostly neighborhoods that were just flat-out leveled.

　　JEFFREY BROWN:All right. So most important for you right now is, as you said, get people—people stay off the street. What else?

　　GARY KNIGHT:Let the emergency workers in to do what they need to do to help get these people—help get these people some help.

　　JEFFREY BROWN:And one more question. Was there a medical center also? There are some reports that a medical center was hit as well.

　　GARY KNIGHT:I don't have any information on a medical center being hit, although there is one very close to that area.

　　JEFFREY BROWN:All right.

　　Sgt. Gary Knight in Oklahoma City, thanks so much.

　　GARY KNIGHT:You bet. Thank you.

　　JEFFREY BROWN:And more now from Bill Bunting of NOAA's National Storm Prediction Center in Norman, Okla. He's a meteorologist and the operations chief there.

　　Well, thanks for joining us.

　　I'm not sure if you could hear that last interview. What can you add to the extent of the damage now? What are you seeing?

　　BILL BUNTING, Storm Prediction Center, National Oceanic and Atmospheric Administration: Well, I haven't seen the most recent damage images, although, just from what I have heard, it sounds absolutely catastrophic.

　　I think the message I would want to get out is for folks that are in the path of storms that are still ongoing, take these warnings extremely seriously. Folks in this part of the country typically know that severe weather season is here and that they need to have a plan. Now is the time to put that plan into action.

　　If you're in the path of these storms, the seconds that you take now to put your tornado readiness plan into action could very well make the difference between life and death.

　　JEFFREY BROWN:What about the enormous size of this tornado? How unusual is that, and what would cause it?

　　BILL BUNTING:Most tornadoes typically are much smaller than this.

　　This is obviously towards the upper end of the enhanced Fujita scale that we use to rate them. When conditions come together just right, the change in wind speed and direction, with height, the amount of instability in the atmosphere, you can get these tremendous concentrations of energy, unfortunately, seeing tornadoes that are the size of what we have seen today. And, unfortunately, our worst fears have become realized, hitting highly populated areas.

　　And we just hope that folks heeded the warnings and were in a safe place when the storms hit.

　　JEFFREY BROWN:And because you have had so many tornadoes in the area in the last couple of days, do you know, in this case, one huge tornado, or do we even know if there were other tornadoes along with it or going along at the same time?

　　BILL BUNTING:We don't know for sure.

　　Typically, the local and National Weather Service offices will go out tomorrow or as soon as they can get into the area. Obviously, rescue and recovery operations takes precedence, but they will be out as soon as they can and do an accurate assessment of just how many storms, the path, length and width and the intensities involved, but, at this point, way soon to speculate.

　　JEFFREY BROWN:And, as to the warning, is it your sense that people did have fair warning, at least for this very large one that came through?

　　BILL BUNTING:Well, the Storm Prediction Center, the National Weather Service offices and the areas affected have been talking about the risk for tornadoes now for several days.

　　We mentioned that it was going to be a multi-day threat. And today, of course, was another one of those days. And it's not over after today. The threat will shift a bit eastward tomorrow. And so I just hope and pray that they heard the warnings and that folks were in the safest place they could be, and they're OK.

　　JEFFREY BROWN:Just give us a sense of how this works, because people there are quite used to tornadoes. How much planning goes into something like this? How much preparation is for an event like this?

　　BILL BUNTING:Well, we have been talking about the threat of tornadoes at the Storm Prediction Center, the local National Weather Service offices that really interface with the communities and the local broadcast media.

　　Everyone knew this was going to be an active weekend and into the first part of this week. The day-after-day threat of severe weather I think has made everyone aware that the danger is high. Most events, often, at least, the tornado threat exists, and then things are quieter the next day. This is not unheard of, but it's a bit unusual that we would have consecutive days of very intense tornadoes in the same metropolitan area.

　　And that is, of course, just going to make it more difficult for the rescue and recovery operations that are now under way in several areas.

　　JEFFREY BROWN:And we're seeing reports of 200-mile-an-hour winds. How about—how unusual is that?

　　BILL BUNTING:Well, that's certainly extremely rare. And, again, the actual assessments will take place in the days ahead.

　　But it's a very small percentage of all tornadoes with wind speeds in that range. So this is a very rare event and, unfortunately, in a very populated area.

　　JEFFREY BROWN:All right, Bill Bunting of NOAA, thank you very much.

　　BILL BUNTING:Thank you.