Contact: Dane Konop FOR IMMEDIATE RELEASE
5/30/97A team of government and university scientists and student volunteers has for the first time observed a tornado close-up with dual high-resolution Doppler radars, providing a never-before-seen two-dimensional view of a full-blown tornado, the National Oceanic and Atmospheric Administration announced today.
The team, called "Subvortex" and based at NOAA's National Severe Storms Laboratory in Norman, Okla., intercepted an F1 tornado May 26, southwest of Tulsa. The Subvortex scientists scanned the slow moving twister for 10 minutes with the two Doppler radars mounted on flatbed trucks. The information collected will ultimately help NOAA improve tornado watches and warnings, and reduce false alarms.
The group of about 20 Subvortex scientists and students is led by principal scientists Erik Rasmussen of the NOAA-University of Oklahoma Cooperative Institute for Mesoscale Meteorology, Jerry Straka and Josh Wurman of Oklahoma University, and Robert Davies-Jones of the National Severe Storms Laboratory.
The team also photographed the May 26 tornado and made a variety of meteorology measurements in and near the storm with a mobile mesonet. A mobile mesonet is comprised of cars specially equipped to measure weather conditions, with communications and computer links to the other vehicles in the Subvortex team.
The Subvortex researchers intercepted a second tornado later in the day south of Tulsa, and east of the first tornado.
The twin Dopplers on Wheels, developed by Wurman, are unique truck-mounted research radars that can be positioned within a few kilometers of a tornadic storm to document in fine detail wind speeds and reflectivity. The radar scans the entire mesocyclone region (the area of rotating air) every 90 seconds, producing data that should provide major clues into how tornadoes form and persist.
In a typical operation, the Subvortex team leaders review NOAA satellite data and other NOAA weather information while at their National Severe Storms Laboratory base of operations. The team targets an area within a day or two drive of their Norman, Okla., base where they believe weather patterns will likely produce a mesocyclone, a large rotating body of air that can spawn tornadoes.
The Subvortex team's two flatbed trucks, a field control vehicle, two prove vehicles, and assorted other support vehicles then set off for the target region, all the while fine tuning their approach with the latest weather information, often driving hundreds of miles to be in the right place at exactly the right time. When the team arrives in the target area, they try to position themselves in the path of the approaching mesocyclone. After choosing a likely location, preferably a piece of high ground overlooking flatlands unobstructed by trees and houses, the two DOWs are parked up to a few kilometers apart, at right angles to each other so that they can get a 2-dimensional view of the tornado's movement. With the 8-foot-diameter Doppler radars scanning the approaching storm and with hydraulic stabilizing legs dug in to steady the DOW trucks, the scientists then stand-by to photograph and measure the entire life cycle of the tornado.
Although it takes several minutes to move the DOWS once they have dug in, should the storm system shift, the team can and often will move with the weather system to continue their measurements.
Subvortex is a follow-up to the VORTEX tornado research project in 1994 and 1995, in which scientists intercepted 10 tornadoes and studied them close up using a suite of instruments, including Wurman's prototype Doppler on Wheels in the second year of the project. The new twin Dopplers being used in Subvortex, called "DOWs," are allowing scientists to get high-resolution radar coverage of tornado formation. Subvortex scientists are especially interested in the little understood rear flank downdraft region of a tornadic storm because it may play a key role in transporting rotation to the ground.