Tornadoes can form in minutes, making early and accurate warnings crucial to saving lives. Howard Bluestein at the University of Oklahoma and Adam Houston at the University of Nebraska are trying to understand why some storms produce tornadoes and others don't. "When Nature Strikes" is produced by NBC Learn in partnership with the National Science Foundation and The Weather Channel. For a classroom activity related to this video, please click the Links section below.
When Nature Strikes -- Tornadoes
MARSHALL SHEPHERD reporting:
With wind speeds ranging from 65 to 300 mph, tornadoes can rip through communities, causing numerous deaths and billions of dollars in damage. Two atmospheric scientists funded by the National Science Foundation are determined to learn more about the life-cycle of tornadoes, hoping it leads to better forecasting and fewer casualties.
Just after 5:30 pm on May 22, 2011, a powerful tornado nearly a mile wide cut a path through Joplin, Missouri, leaving a trail of devastation, including 158 people killed. On average, more than a thousand twisters are reported each year in the United States. Although forecasters recognize the storm conditions in which tornadoes can form, they don't know for certain when and where a tornado will strike.
HOWARD BLUESTEIN (University of Oklahoma): Tornadoes are very difficult to predict because the conditions that are necessary to produce tornadoes are very, very specific and very exacting.
SHEPHERD: Howard Bluestein is an atmospheric scientist at the University of Oklahoma and one of the world's leading tornado experts, well-known for radar research on severe storms.
BLUESTEIN: When you take a radar and look at a storm, you get a full three-dimensional picture of what the storm looks like. Ultimately this research will help us understand why some storms produce tornadoes and others don't so that warnings can be improved.
SHEPHERD: Better tornado forecasting could be a tremendous help to people across the central and southeast United States, where more tornadoes are recorded each year than anywhere else in the world-- an area often referred to as Tornado Alley. Commonly, the largest and most intense tornadoes develop in severe thunderstorms known as supercells.
BLUESTEIN: Supercell is a thunderstorm on steroids. And because it's rotating, it lasts for a lot longer period of time than an ordinary thunderstorm does.
SHEPHERD: Supercells develop when cool, dry winds of a jet stream blow in from the west above warm, moist winds from the Gulf of Mexico. The winds, moving in different directions and at different speeds, begin to rotate, and with a strong updraft, the rotation can become vertical. This rotation is called a mesocyclone and is characteristic of a supercell. The upward-rotating column of air spins faster and faster as air converges into the storm, like a figure skater accelerates when tucking in her arms. At this stage, and in the right conditions, a tornado could form and extend below the supercell.
Only a small percentage of supercells actually produce tornadoes. So, what has happened within those particular supercells to cause the sudden appearance of a tornado? What are the right conditions? Scientists don't really know.
BLUESTEIN: But we know that tornadoes can change in the order of ten seconds and a tornado can form in just a minute or two. So if you want to learn why a tornado is forming, you want measurements every ten seconds or even less than that.
SHEPHERD: Radar can measure some parts of a storm, but it can't reach the storm's lowest levels just above the ground, an area that could hold valuable information. Adam Houston, at the University of Nebraska-Lincoln, is taking a closer look at tornadoes in these lower levels.
ADAM HOUSTON (University of Nebraska-Lincoln): New technology gives us the opportunity to see the atmosphere in a way that we were unable to see before.
SHEPHERD: Houston and his research team are trailblazing a new approach to studying tornado formation. They're using unmanned aircraft systems, commonly called drones, to measure the air masses surrounding a storm. The aircraft are lightweight, mobile, and easily deployed from a field or roadside. They carry instrumentation and can record measurements wherever they're directed, horizontally and vertically.
HOUSTON: We deploy these aircraft into the path of the storm, we fly the aircraft within the storm and ahead of the storm, and collect these temperature and moisture data, not just at the surface but throughout a layer above the surface.
SHEPHERD: It's a groundbreaking effort in tornado research that could help scientists better understand what generates a tornado.
HOUSTON: I think this may be one of the new instruments for the future, because of its great potential to collect data where we cannot otherwise collect data and to potentially significantly impact our ability to accurately forecast on the storm scale.
SHEPHERD: The research of scientists like Bluestein and Houston aims to increase understanding that could improve forecasting, give more accuracy to tornado watches and warnings, and even influence building codes and construction practices-- all helping to better prepare and protect communities that could be in the path of the next devastating twister.
A tornado is a narrow, violently rotating column of air that extends from the base of a thunderstorm to the ground. Because wind is invisible, it is hard to see a tornado unless it forms a condensation funnel made up of water droplets, dust and debris. Tornadoes are the most violent of all atmospheric storms.
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