Lots of people chase tornadoes, usually for the thrill. But Howard Bluestein is “the tornado chaser.” He has spent 25 years getting up-close-and-personal with twisters, not for excitement, but in an attempt to learn more about them. His fascination with these violent weather events has brought him to the attention of meteorological researchers and even Hollywood producers. (The film Twister was based in part on Bluestein’s research, although he doesn’t think that the movie was a very accurate portrayal.) He is a Samuel Roberts Noble Presidential Professor of Meteorology at the University of Oklahoma, and recently authored the popular book Tornado Alley: Monster Storms of the Great Plains. He talked with ODYSSEY from his summer research position at the National Center for Atmospheric Research (NCAR) in Boulder, CO. Each spring you gather your crew for the tornado season. Why is spring the best time for tornado formation? It’s the best time in the Plains area of the United States. During spring you get a return of moisture from the Gulf of Mexico to the south, and moderately strong winds from the west with the jet stream. 1So, at that time of year, disturbances move from west to east and all the factors come together: moisture from the Gulf of Mexico, warm surface temperature that decreases rapidly with height, a strong change of direction and wind speed with height, and a jet stream far enough south that you can get the strong vertical wind shear 2that you need to make supercells—huge rotating storm clouds. What conditions indicate that there’s a good chance of tornadoes on any given day? First, I look to see if there’s enough Gulf moisture. If there isn’t enough moisture, then forget it. Then I look to see whether the temperature decreases with height relatively rapidly—and whether there is a high enough surface temperature so that a parcel of air can go up very, very high into the atmosphere. That tells me that thunderstorms are possible. Then I look at the vertical wind shear—whether the winds will be changing direction or speed enough for a supercell thunderstorm. Those conditions are necessary for a tornado, but they aren’t enough. Finally, I look for some triggering mechanism—an upper-level disturbance that will enhance the probability that storms will form. What is a typical storm chase like? We look at the weather in the morning—surface observations, satellite observations, computer forecasts, radar—and I decide whether there’s a significant chance of tornadoes somewhere in an area that we can get to, which means roughly within 200 to 250 miles. We try to choose a target area and go. We may stop, plug the laptop in and get computer data from back home, or I might get on the cell phone. We get information any way we can—and we also depend on our visual observations and past experience. If more than one storm comes up, we decide which is the more likely to produce a tornado. We have two mobile radars, so we can see if a storm has rotation, and we can see where it might be going and we can try to get in its path—not directly, but within one or two miles. But typically, we don’t see anything. Tornadoes don’t last long and their paths change, and the road system doesn’t always allow you to get exactly where you need to go. ODYSSEY readers would love to hear about one of the most dramatic moments you’ve had as a storm chaser ... Oh, there have been many of them—seeing my first F5 tornado in 1991 was one. We were up in north-central Oklahoma and we heard reports of a tornado to our south. There was rain and hail between us and the tornado, as we moved east and then south. We could see the tornado—it was getting larger and larger because we were getting closer and closer. We were right in its path. We set up right in front of the tornado... my students told me that it was coming right at us. We dropped south, and they took measurements and I just watched in awe as the tornado churned and crossed the road just to our north. It destroyed a house and then the wind shifted to the southwest. We were in the downdraft 3 and it started raining heavily and the tornado disappeared into the rain. We were just about a mile from where telephone poles were lying in the road. I remember thinking as I watched it, “This is something I’m not going to see very often in my life.”Based on the many amateur videos we see of tornadoes, the general public also seems to be fascinated with seeing and photographing twisters in action. Are you concerned for their safety? I would say so. People think that it’s easy to go out and take video and that they’re always going to be safe, but that’s not the case. If they are less than two miles from a tornado they could be injured, even if they are not in the direct path. The greatest risk is getting hit by flying debris. Do you see any increase in violent weather patterns? Absolutely not! I’ve been doing this for 25 years, and I can think of times when all hell breaks loose and then there are years when very little happens. The spring of 2003 happened to have been a time with a lot of activity—an unusually large amount of activity—but the year before was relatively quiet. You’d have to go back to 1999 before I could say that it was a relatively active year. Before that, I’d have to go back to 1995, then 1991. I think it’s normal fluctuation. What do you see as the ultimate goal of tornado research? We don’t yet understand why it is that some supercells produce tornadoes and some do not. We need to understand this if we are ever going to be able to make a forecast that says, “This thunderstorm here—don’t worry about it. However, this thunderstorm over here is more of an issue and you had better seek shelter.” That’s the ultimate goal, and to do that you need to understand how the tornado forms. Right now, the National Weather Service looks for evidence of rotation in a storm. If they see the rotation, they go ahead and put out a tornado warning. We now know that the number of such storms that actually produce tornadoes is only 5 to 10 percent. So you issue a lot of false warnings, and if you cry “Wolf!” too often, the public may not get excited about future warnings. You say in your book, “In order to study a meteorological phenomenon properly, you must actually experience and appreciate it aesthetically.” Those words usually are used when discussing a form of art. Nature is an art show. Watching the weather is watching theater. I enjoy what I do. I see things each year that I’ve never seen before, and I’m still fascinated. I’m the sort of person who says, “Look, tornadoes might be an interesting scientific problem, but I’m not going to study a tornado by looking at someone else’s data or by making a computer simulation 4without ever having actually seen one. I want to see the tornado itself.

Question

Lots of people chase tornadoes, usually for the thrill. But Howard Bluestein is “the tornado chaser.” He has spent 25 years getting up-close-and-personal with twisters, not for excitement, but in an attempt to learn more about them. His fascination with these violent weather events has brought him to the attention of meteorological researchers and even Hollywood producers. (The film Twister was based in part on Bluestein’s research, although he doesn’t think that the movie was a very accurate portrayal.) He is a Samuel Roberts Noble Presidential Professor of Meteorology at the University of Oklahoma, and recently authored the popular book Tornado Alley: Monster Storms of the Great Plains. He talked with ODYSSEY from his summer research position at the National Center for Atmospheric Research (NCAR) in Boulder, CO. Each spring you gather your crew for the tornado season. Why is spring the best time for tornado formation? It’s the best time in the Plains area of the United States. During spring you get a return of moisture from the Gulf of Mexico to the south, and moderately strong winds from the west with the jet stream. 1So, at that time of year, disturbances move from west to east and all the factors come together: moisture from the Gulf of Mexico, warm surface temperature that decreases rapidly with height, a strong change of direction and wind speed with height, and a jet stream far enough south that you can get the strong vertical wind shear 2that you need to make supercells—huge rotating storm clouds. What conditions indicate that there’s a good chance of tornadoes on any given day? First, I look to see if there’s enough Gulf moisture. If there isn’t enough moisture, then forget it. Then I look to see whether the temperature decreases with height relatively rapidly—and whether there is a high enough surface temperature so that a parcel of air can go up very, very high into the atmosphere. That tells me that thunderstorms are possible. Then I look at the vertical wind shear—whether the winds will be changing direction or speed enough for a supercell thunderstorm. Those conditions are necessary for a tornado, but they aren’t enough. Finally, I look for some triggering mechanism—an upper-level disturbance that will enhance the probability that storms will form. What is a typical storm chase like? We look at the weather in the morning—surface observations, satellite observations, computer forecasts, radar—and I decide whether there’s a significant chance of tornadoes somewhere in an area that we can get to, which means roughly within 200 to 250 miles. We try to choose a target area and go. We may stop, plug the laptop in and get computer data from back home, or I might get on the cell phone. We get information any way we can—and we also depend on our visual observations and past experience. If more than one storm comes up, we decide which is the more likely to produce a tornado. We have two mobile radars, so we can see if a storm has rotation, and we can see where it might be going and we can try to get in its path—not directly, but within one or two miles. But typically, we don’t see anything. Tornadoes don’t last long and their paths change, and the road system doesn’t always allow you to get exactly where you need to go. ODYSSEY readers would love to hear about one of the most dramatic moments you’ve had as a storm chaser ... Oh, there have been many of them—seeing my first F5 tornado in 1991 was one. We were up in north-central Oklahoma and we heard reports of a tornado to our south. There was rain and hail between us and the tornado, as we moved east and then south. We could see the tornado—it was getting larger and larger because we were getting closer and closer. We were right in its path. We set up right in front of the tornado... my students told me that it was coming right at us. We dropped south, and they took measurements and I just watched in awe as the tornado churned and crossed the road just to our north. It destroyed a house and then the wind shifted to the southwest. We were in the downdraft 3 and it started raining heavily and the tornado disappeared into the rain. We were just about a mile from where telephone poles were lying in the road. I remember thinking as I watched it, “This is something I’m not going to see very often in my life.”Based on the many amateur videos we see of tornadoes, the general public also seems to be fascinated with seeing and photographing twisters in action. Are you concerned for their safety? I would say so. People think that it’s easy to go out and take video and that they’re always going to be safe, but that’s not the case. If they are less than two miles from a tornado they could be injured, even if they are not in the direct path. The greatest risk is getting hit by flying debris. Do you see any increase in violent weather patterns? Absolutely not! I’ve been doing this for 25 years, and I can think of times when all hell breaks loose and then there are years when very little happens. The spring of 2003 happened to have been a time with a lot of activity—an unusually large amount of activity—but the year before was relatively quiet. You’d have to go back to 1999 before I could say that it was a relatively active year. Before that, I’d have to go back to 1995, then 1991. I think it’s normal fluctuation. What do you see as the ultimate goal of tornado research? We don’t yet understand why it is that some supercells produce tornadoes and some do not. We need to understand this if we are ever going to be able to make a forecast that says, “This thunderstorm here—don’t worry about it. However, this thunderstorm over here is more of an issue and you had better seek shelter.” That’s the ultimate goal, and to do that you need to understand how the tornado forms. Right now, the National Weather Service looks for evidence of rotation in a storm. If they see the rotation, they go ahead and put out a tornado warning. We now know that the number of such storms that actually produce tornadoes is only 5 to 10 percent. So you issue a lot of false warnings, and if you cry “Wolf!” too often, the public may not get excited about future warnings. You say in your book, “In order to study a meteorological phenomenon properly, you must actually experience and appreciate it aesthetically.” Those words usually are used when discussing a form of art. Nature is an art show. Watching the weather is watching theater. I enjoy what I do. I see things each year that I’ve never seen before, and I’m still fascinated. I’m the sort of person who says, “Look, tornadoes might be an interesting scientific problem, but I’m not going to study a tornado by looking at someone else’s data or by making a computer simulation 4without ever having actually seen one. I want to see the tornado itself.

using this context

Based on the interview, what conditions make spring an ideal season for tornado formation in the Plains area? A the rotation of wind and sea currents B the movement and height of thunderclouds C the merging of warm moisture and strong winds D the interaction of wind disturbances from the north and south

Answer 1