Chasing down the mysteries of tornadoes

by John D. Cox | May 08, 2009

A small army of scientists and support people are taking to the road next week to launch an ambitious new two-year offensive in one of the most daunting and hardest fought campaigns in meteorology -- capturing the fine atmospheric details that lead to the formation of tornadoes.  For all of the destructive power they hold for life and property, for all the resources poured into warnings and shelters and public information campaigns, some basic information about these terribly violent winds simply is not known.  Why do they form?  What causes a tornado to come roaring out of one supercell thunderstorm, but not another?

Operating out of the National Weather Center in Norman, Oklahoma, researchers from a variety of agencies and universities will be deploying high-precision mobile radars, balloons and more than three dozen portable surface weather stations in the paths of target storms up and down a 900-mile swath of the Great Plains.  Between May 10 and June 13, phase one of VORTEX2, followed by a similar campaign next spring, will begin to fill in critical details needed to allow forecasters to better predict tornadoes and give citizens more time to take cover.

(Click on the image of a project leader, Roger Wakimoto of the National Center for Atmospheric Research, to see him discuss the goals of the VORTEX2.  And click on the image of the supercell storm to see how instruments will be positioned in the path of a storm.)

A smaller field experiment in the mid-1990s advanced the science and improved the false-alarm ratio by 5 to 10 percent, according to research meteorologist Don Burgess, a veteran of that campaign, known as VORTEX.  "We know it's still high, we have a better-safe-than-sorry philosophy, as we should, but there was a measurable improvement," he told a news conference Friday.

Still, because they lack fundamental details by the origin of tornadoes, forecasters issue warnings that are based on radar detection of tornadoes and their own instincts -- circumstances that have limited lead times of average warnings to roughly 13 minutes.  With more hard work, these efforts might extend that lead time a minute or so, but the thinking behind VORTEX2 is to do more.

"What we envision in the future is being able to take high resolution numerical models and actually do a predicting of tornadoes, so that we can make a real dent in the current warning times," said Kevin Kelleher, deputy director of the National Severe Storms Laboratory.  "We think that the next step is to create a forecast component with numerical models.  And to do that we have to better understand what's happening in the storm.  And that's what VORTEX 2, we hope, will provide for us."

- John D. Cox
images/videos: Courtesy University Corporation for Atmospheric Research