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Science

Tornado-Chasing Truck Now Chasing Winter Storms

Storm chasers are usually depicted as high-octane meteorologists chasing tornadoes across tornado valley in the United States, but a truck-mounted radar dish that is often used to chase these tornadoes is doing duty in Utah, providing meteorologists from the University of Utah an opportunity to get inside snow and rain storms over the Salt Lake Valley and the surrounding Wasatch and Oquirrh mountains.

“For students who love snow, it’s every bit as thrilling as chasing tornadoes,” says atmospheric sciences Professor Jim Steenburgh. “That’s why we call it storm chasing, Utah style.”

The tornado-chasing Doppler on Wheels radar truck is set up at Lake Point on Interstate-80 west of Salt Lake City to measure an approaching cold front. With National Science Foundation funding, University of Utah meteorologists are using the advanced radar technology to study winter storms.

“We have never been able to examine the ‘guts’ of Wasatch winter storms like we can with the Doppler on Wheels radar that is presently here in Salt Lake City,” Steenburgh wrote recently in his Wasatch Weather Weenies blog. “In particular, we can take a meteorological CAT scan of winter storms to see their inner workings.”

The Storm Chasing Utah Style Study, also known as SCHUSS which, when not acronymised is also the name for a straight, downhill ski run, is using the Doppler on Wheels, or DOW, radar truck operated by the Center for Sever Weather Research in Boulder, Colorado for the National Science Foundation.

Originally developed for studying tornadoes, the Doppler on Wheels truck arrived in Salt Lake City on October 21 and will remain there until November 21. Already a dozen of University of Utah graduate students have been trained to drive the vehicle, which uses “X-band polarimetric Doppler radar” and was used to measure “the strongest wind ever recorded during the Moore, Oklahoma tornado” in 1999, clocking speeds at 318 miles per hour.

Steenburgh says the DOW radar can distinguish the size and shape of snowflakes and raindrops in a storm, can collect data on lower-elevation valley locations and can park closer to storms and thus get more detail.

This Doppler on Wheels radar image shows an orange band of "lake effect" snow over the southeast corner of the Great Salt Lake, moving toward the Wasatch Range (red on right). University of Utah scientists are using the high-tech radar truck for a month in the Salt Lake City area for studies related to improving forecasts of rain and snow.

“Despite improvements in weather forecasting over the past few decades, winter storms in Utah remain a challenge to predict,” Steenburgh says. “Unlike radars used for weather forecasting, the Doppler on Wheels can be placed anywhere during a storm, enabling us to peer into storms and uncover their secrets. The information we collect can be used to better understand lake-effect, mountain and other Utah storms, and improve computer models used for weather prediction.”

When the truck is used to chase tornadoes, “you are constantly driving,” he says. “We don’t move it around a lot. We let the storm come to us. … But in a long-lived, multiday storm, we would probably move it as the storm characteristics change.”

During a Nov. 1 snowstorm in Utah, this Doppler and Wheels radar truck was parked on the west side of the Salt Lake Valley, capturing unprecedented images of the "transition zone" where snowflakes melt into raindrops. The truck, normally used to chase Midwest tornadoes, is in Salt Lake City Oct. 21-Nov. 21 so University of Utah meteorologists can study the structure and detail of winter storms.

Steenburgh is hoping to use the track’s radar to measure between eight and ten storms while it is in residence in Utah. The truck has already captured five weather events;

  • The radar truck was parked at Lake Point on Interstate-80 and used to look at the structure of a dry, cold front that moved across the Great Salt Lake Oct. 24-25.
  • From an observation point on State Route 111 on the west side of the Salt Lake Valley, the radar observed puffy cumulus clouds over the Wasatch Range on Oct. 26.
  • On Oct. 30, the radar was deployed to observe breezes blowing southward off the Great Salt Lake and into Rush Valley.
  • Parked again on SR-111, the radar truck watched as a cold front with rain and snow moved over the Salt Lake Valley on Nov. 1. The radar captured a burst of heavy snow over Twin Peaks in the Wasatch Range, and got unprecedented images of the “transition zone” where falling snowflakes turn to raindrops. The exact elevation of the transition zone is critical to forecasting if a city like Salt Lake will experience weather of 32 degrees Fahrenheit with heavy snow or 35 degrees with rain.

“The truck is teaching our students with a new kind of radar to better determine where the snow level is and where precipitation is transitioning from rain to snow, which is a big piece of figuring out how much snow is going to fall at any particular location,” Steenburgh says.

  • A big snowstorm, with some snow enhanced by the Great Salt Lake’s “lake effect,” was captured by the radar truck on Nov. 4 and 5 as it dumped several inches of snow on Salt Lake City and other Wasatch Front cities. University of Utah students pulled an all-nighter in the truck making measurements of the storm.

“We got an unprecedented data set on the lake effect snow that fell Saturday morning,” Steenburgh says. “It was phenomenal.”

You can read more by Steenburgh on his Wasatch Weather Weenies blog.

Source: University of Utah
Image Source: Jim Steenburgh, University of Utah




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