Archive of Spotlight Feature Articles

Have radar -- will travel

By Susan Cobb, NSSL

The rhythmic clanking sound of the mobile radar dish moving from "stow" to "operate" is strangely comforting to researchers with NOAA's National Severe Storms Laboratory in Norman, Okla. A team in a minivan has already scoured the countryside for a place to set up the radar.

"Municipal airports can make for good sites for long deployments, but a high or flat space with open fields works great for catching a storm," says NSSL researcher Ted Mansell.

All that is required is a place that can hold the weight of a 16-ton truck , a solid place to turn around, and an unobstructed view.

Once it's parked, the mobile radar can deploy in a matter of minutes. The team rushes to place the leveling plates under the truck's stabilizers. The pedestal holding the radar dish groans to life and begins to sweep back and forth. From a workstation in the back of the truck cab, a scientist leans out the window to study the sky and choose the best scan strategy.

It doesn't get the best gas mileage, but the value of mobile radar data to weather science has been immeasurable. NSSL, the National Center for Atmospheric Research and University of Oklahoma (OU) researchers teamed up to build the first mobile radar in 1995. The radar was ready just in time for the final year of the 1994-95 Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX). Improvements in National Weather Service warning statistics since then have been attributed, in part, to the secrets uncovered by VORTEX data collected near supercell thunderstorms.

More recently, teams drove up to ten mobile radars more than 25,000 miles each across the Great Plains during VORTEX 2009-2010 (VORTEX2). Lumbering from state to state for weeks at a time in search of supercell thunderstorms can wear on a radar team, but the potential to find answers to important vital tornado questions kept them going. More than a dozen tornadoes were captured with these radars during VORTEX2 and researchers are excited about what the data may reveal.

Use of mobile radars has expanded beyond the Great Plains. Scientists endure some shaky moments when they use the mobile radars to scan tropical storms and hurricanes during landfall. For example, Tropical storm Gabrielle passed directly overhead of one research team and the radar captured unprecedented data on its eye wall. Hurricane Ike rocked the mobile radar team with 84 mph wind gusts as it made landfall nearby.

Scientists are putting together other weather puzzles using dual-polarized mobile radar. Dual-polarized radar technology provides new information on what type of precipitation is falling and how much moisture it contains. Is it a dry snow, heavy wet snow or a mix? The difference is crucial to forecasters watching for disabling snowstorms or spring flash floods.

Stationary weather radars that are placed far apart have data gaps between them created by the earth's curvature. In certain locations mountains or other terrain can block radar beams. These blockages and gaps can be thought of as "black holes" in the radar data, and NSSL's mobile radar teams have been called in to help. Southwest Colorado, central Arizona, southern California, the 2010 Winter Olympic Games in Vancouver and even Switzerland have all asked for the extra pair of "radar eyes" provided by these radars on wheels. Heavy snowfall, torrential rain and damaging microbursts cannot escape the roving eye of the radar.

Whenever and wherever they're deployed, the mobile radars don't get much of a break and neither do the researchers. Though they pore over the data by day, at night when they close their eyes they can still hear the creaks and groans of the radar scanning the skies. There are still more secrets for these radars to reveal. They are mobile radars after all!

March 14, 2011

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