Rapid-Scanning Doppler on Wheels Keeps Pace with Twisters

Jun 01, 2005
Rapid-Scanning Doppler on Wheels Keeps Pace with Twisters

A new Doppler radar instrument that can scan tornadoes every five to 10 seconds is prowling the Great Plains this spring in search of its first close-up twister. Newly enhanced for season-long thunderstorm tracking, the radar promises the most complete picture to date of tornado evolution, allowing for better tornado prediction in the future.

Image: Doppler on Wheels caught dozens of tornadoes in 2004, including this one on May 12 near Attica, Kan. Credit: Center for Severe Weather Research

Known as the Rapid-Scan Doppler on Wheels (DOW), the instrument was deployed from a temporary base in Hays, Kan., by scientist Joshua Wurman of the Center for Severe Weather Research. Engineers at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., helped build the DOW, which is funded by the National Science Foundation (NSF).

Most Doppler radars transmit only a single beam, which takes about five minutes to make the vertical and horizontal scans needed for a three-dimensional storm portrait. But tornadoes can develop or dissipate in a minute or less. With its five- to 10-second resolution, the Rapid-Scan DOW can detail these critical steps in tornado behavior at close range.

"The development of the multi-beam mobile Doppler radar is an important advance in meteorological research," says Steve Nelson, director of NSF's physical and dynamic meteorology program, which funded the research. "This new radar will collect higher resolution data than were possible in the past, giving us unique measurements of rapidly evolving meteorological phenomena like tornadoes."

The first DOW was deployed in 1995. Since then, Wurman and his colleagues have collected data on more than 100 tornadoes. On May 3, 1999, a DOW measured a world-record wind speed of 301 miles per hour just above ground level in an Okla. tornado.

As part of a $1.6 million NSF grant, Wurman and Curtis Alexander of the University of Oklahoma are analyzing the entire DOW data set on tornadoes to uncover new information, such as how closely tornado diameters are correlated with top wind speeds.

"We can't answer basic questions about 'typical' tornadoes right now, such as how strong their winds are," says Wurman. "By looking at these cases, we hope to better understand the features of many types of tornadoes." These findings could be compared to storm types to produce improved warnings, Wurman adds.

Wurman and NCAR scientists plan to select a few tornadoes for more in-depth study. They'll use a technique called velocity track display (VTD), originally developed for hurricane studies, that allows scientists to extract three-dimensional wind information from a single Doppler radar.

The scientists have already used VTD with DOW data to analyze a large and intense tornado that struck Mulhall, Okla., in 1999. They discovered a central downdraft, similar to the eye of a hurricane, surrounded by a ring of updrafts blowing at near-hurricane force, with multiple small vortices rotating around this ring. The structure found in the Mulhall tornado had been observed for many years in lab experiments and computer models, but it had never before been verified by radar data.

Dubbed ROTATE-05, this spring's field work is supported by the National Geographic Society.

Source: National Science Foundation

Explore further: NASA missions may re-elevate Pluto and Ceres from dwarf planets to full-on planet status

add to favorites email to friend print save as pdf

Related Stories

Recommended for you

Stars found forming at Milky Way's outer edge

5 hours ago

Brazilian astronomers said Friday they had found two star clusters forming in a remote part of our Milky Way galaxy where such a thing was previously thought impossible.

'Bright spot' on Ceres has dimmer companion

14 hours ago

Dwarf planet Ceres continues to puzzle scientists as NASA's Dawn spacecraft gets closer to being captured into orbit around the object. The latest images from Dawn, taken nearly 29,000 miles (46,000 kilometers) ...

New insight found in black hole collisions

20 hours ago

New research by an astrophysicist at The University of Texas at Dallas provides revelations about the most energetic event in the universe—the merging of two spinning, orbiting black holes into a much larger ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.