FirstScience: When did your fascination with tornadoes begin?

Josh Wurman: "I have been interested in the weather since I was quite little. I used to cut out the daily weather maps from the local newspapers and make weekly summaries for my elementary school newspaper when I was just 7-9 years old. I like to understand how things work, physics and mathematics, and nature. Meteorology has let me combine my interests in a very interesting new field, which has many important outstanding questions. I became interested in tornadoes when I moved west to Colorado from Massachusetts several years ago. I went chasing with scientist friends. I was amazed by the structure, beauty and power of these storms. I wanted to understand more about how they form and what was going on inside them. So I designed new technology, the Doppler On Wheels radars, in the center of tornado alley and began the serious pursuit of tornadoes."

FS: How do you find tornadoes and how do you chase them?

JW: "We forecast the general area in which tornadoes are likely to form. Then we drive in this region and wait for storms to form. When they do, we target the most interesting thunderstorms, watching for any clues that it may be strengthening or weakening, and try to place our radars near the region where the tornadoes form."

FS: What has been your scariest moment chasing a tornado?

JW: "This may sound boring, but we really do not have many scary moments. We are engaged in an intense scientific mission to try to understand one of the most powerful forces of nature. But we cannot afford to be thrill seekers, or to take unreasonable risks. With an on-board Doppler radar, we can see the precise strength, size and motion of a tornado. So even when we are very close to one, at a range that might be frightening to those without all our information and training, we are mainly focused on the mission, where to go next, routes for targeting and escape etc. We are surprisingly un-excited during intercepts."

FS: What is the most powerful tornado on record?

JW: "Unfortunately, very few tornadoes have had quantitative measurements of their windspeeds. The highest windspeeds ever measured were about 135 m/s in the tornado that went through Oklahoma City on 3 May 1999.

But it is very unlikely that this was the strongest tornado ever. It just happened to be measured by us. These were measured with the Doppler on Wheels radars. The traditional fashion in which tornadoes are categorized is the Fujita scale. But, this only measures the intensity of damage that the tornadoes have actually caused. A very powerful tornado passing over open country (and 99% of the country that tornadoes cover is open country, particularly in the sparsely populated tornado alley) will only cause F0 damage but a weaker tornado passing through a town might cause F4 damage. The Fujita scale does not measure windspeeds. It is often misused by the media and public. We propose that a Potential Fujita scale, similar to the Saffir-Simpson scale used for hurricanes be adopted. The PF scale will represent our best estimate of the actual windspeeds in a tornado, and its potential for doing damage."

FS: How do tornadoes form?

JW: "The glib answer to that is we do not know. That is why we are studying them. We know the basic processes by which rotation is generated in supercellular thunderstorms. But we do not understand how and why and when these rotations, called mesocyclones, produce more intense, smaller-scale rotations called tornadoes. We do not know how to predict when a particular supercell will produce a tornado. We cannot forecast the size, strength, or lifetime of a tornado. In short, even though major strides have been made in the understanding of tornadoes and tornadogenesis in recent years, we have a long way to go."

FS: How many lives do you estimate have been lost to tornadoes and what can be done to give people more advanced warnings?

JW: "Tornadoes kill fewer people than some other weather phenomena. Tornado deaths have been steadily dropping in recent decades due to better warnings and public awareness. This is despite the increasing population in the tornado-prone regions. I do not know the exact numbers, but I think that less than 100 people are killed every year, on average by tornadoes in the USA. Better warnings will require a better understanding of the tornadogenesis process. We need to know how, why and when tornadoes will form in particular storms. More importantly we need to be able to distinguish between the very rare powerful, long track, large tornadoes and the 90% that are far weaker and pose less significant threats. 90% of tornadoes are relatively minor, capable of removing or damaging buildings, but not of the catastrophic damage caused by the few tornadoes that contain winds in excess of 100 m/s. We also need better observations. We propose that a network of adaptable observing systems, like the Doppler On Wheels, be available to provide quick-update, high resolution data to forecasters and computer forecast models so that better predictions can be made. In the coming decade we hope that computer models, based on better understanding and better observations will be developed that will enable predictions of tornadoes an hour or two in advance."

FS: What have you learnt from your research into tornadoes?

JW: "We have learnt about the structure of tornadoes, including 3D windfield, how strong tornado winds actually are, confirmed the existence of multiple-vortices circling around some tornadoes causing extremely high winds near the surface. We are still trying to answer the major questions about the birth of tornadoes, called tornadogenesis".

FS: Will we ever be able to control or stop tornadoes?

JW: "No. It is, of course, possible to stop a tornado. One could drop a nuclear bomb and the heat of the explosion would disrupt the tornado and even the parent thunderstorm. But, even if it were practical to control or stop tornadoes, I believe it would be unwise and immoral to do so. The mathematical and physical equations that govern the atmosphere tell us that altering the weather in one area at one time will cause unpredictable consequences elsewhere at later times. it is morally wrong to purposely alter weather when the consequences may negatively impact other people and regions in unpredictable ways. No one can say whether preventing some tornadoes in Oklahoma will make floods worse in India, or deprive Missouri farmers of needed rain."

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