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‹‹‹ Contents page for this issue     |     Summer 2012

Meteorology research investigates the skies by coming down to earth

By Holly Kays, College of Natural Resources and Environment

For geography graduate student Kathryn Prociv, April 27, 2011, was a day more suspenseful than any adventure book or action movie. The story began early that morning when a tornado struck northern Alabama, the first in an outbreak that would kill 243 people in the region. A self-proclaimed weather nerd, Prociv took note, and when the radar showed severe weather heading toward Blacksburg, she paid even closer attention.

Prociv expected the storm to weaken as night fell and the daytime heat and humidity that storms thrive on subsided, but that didn't happen. The storm maintained its ferocity, and Prociv sprang into action. "I told my roommates that we needed to start preparing," Prociv recalls. "I started posting National Weather Service warnings online, and my Facebook and phone were blowing up with messages. People were genuinely worried."

But amidst the worry, Prociv was also excited. In addition to the barrage of concerned emails flooding her inbox, she kept up an animated exchange with Dave Carroll, the meteorology instructor who leads the Hokie Storm Chase class on trips to the Great Plains each spring. Prociv had gone storm chasing with Carroll the previous summer and planned to join him on two more trips in the upcoming season. Both Prociv and Carroll knew they were witnessing something that probably wouldn't happen again for decades, and beneath Prociv's concern lay an excited awareness that the supercell storm roiling above her third-floor apartment would be the perfect case study for her research.

A first-year master's student, Prociv had presented her research proposal just four months earlier. The initial reaction to her idea was less than enthusiastic — Prociv wanted to study the influence of terrain on tornado behavior in the Appalachian Mountains, but tornadoes in that region were seen as a fairly rare occurrence and therefore not necessarily vital to understand. After the storm passed Blacksburg with less than 10 miles to spare, Prociv breathed easily for more than one reason — she could sleep safely knowing that the next day everyone would have a much better appreciation for her research.

Six months later, Prociv had finished collecting data from the 14 supercell thunderstorms in her study area, which includes 25 counties in Southwest Virginia and eastern West Virginia, and started her analysis. Supercell thunderstorms, though not always tornadic, have rotating updrafts and, therefore, the capacity to produce a tornado at any time.

Prociv says, "From plotting different storms' intensity on top of a terrain profile to easily visualize intensity fluctuations with changes in topography underneath the storm, I've noticed two patterns: Storm rotational velocity increases with a decrease in elevation and storm rotational velocity increases with shallower slopes. Or, said a different way, lower elevations and decreasing elevation and shallower, flatter slopes relate to an increase in storm intensity."

The point: When a rotating storm crosses a ridge and the ground drops away under it, watch out.

She emphasizes that the patterns mentioned above were not evident in all 14 of the storms, but seem to be recurring patterns across eight of the storms, including the devastating tornado in April 2011.

Prociv's research objectives are also to examine the utility of a geographic information system as a tool for examining the relationship between topography and rotational intensity, and to determine forecasting implications from an improved understanding of the relationship between topography and supercell thunderstorms applicable to the study area and other mountainous regions.

Her results will be important from both scientific and safety standpoints. Prociv hopes that studying the relationship of topographical features — such as elevation, slope, aspect, and land cover — to storm intensity will produce conclusions with direct forecasting applicability. "Right now the National Weather Service feels like it is flying blind because these storms start rotating with very little warning," says Prociv. "I'm hoping that my research can help them."

Her study, which she expects to complete about the time this magazine goes to press, will be among the first to examine the unique behavior of mountain tornadoes. She noticed this knowledge gap immediately during the literature review she did before writing her research proposal. "Right away I found articles on large convective systems crossing the mountains," remembers Prociv, "but every conclusion said that there was no research on supercells or tornadoes in the mountains."

Prociv's joint examination of terrain and atmospheric characteristics is unusual in the field of meteorology at large, but it represents a theme in the geography department's meteorology program. Traditionally, radar and other atmospheric data systems have been the realm of meteorology, while geography focused on the terrain attributes now catalogued by geographic information systems (GIS). But weather is impacted by the terrain over which it occurs, so the geography department is applying its strength in GIS to problems of meteorology. "I see this as very important," says Bill Carstensen, department head. "Meteorology is going to use and incorporate GIS more and more, and that's a really big aspect of the program here."

The program Carstensen refers to is still brand new; the department's undergraduate degree in meteorology was approved in July 2011 and instituted in the spring 2012 semester. Carstensen has encouraged development of a meteorology program unique among those of other universities. "Atmospheric scientists study the air and geographers study the ground, but if a tornado goes across the ground, how will the ground underneath affect it?" Carstensen asks. "By geolocating storms using GIS, we can tie all these things together. Most schools aren't doing that."

The ideas of Andrew Ellis, an associate professor in meteorology newly arrived from Arizona State University, will further shape the program's research focuses. "Severe weather is a natural starting point because of the huge impact it can have on our lives," he says.

Both Carstensen and Ellis agree that GIS will be the most important research tool in the new program. This technology allows geographers to place multiple sets of geographically linked data on top of one another so that they can analyze the layers as a single unit. This function is important for meteorologists because it enables them to layer ground data with weather data, such as radar maps, wind direction and speed, air pressure, and temperature.

That's the technology that Prociv uses to analyze supercell storms and that Carroll, a strong proponent of the burgeoning program, hopes to improve with a tool he's been developing. "One of the biggest limitations in meteorology and weather modeling is the relatively limited number of data points," Carroll explains.

Weather stations are located where people are, true to their traditional purpose of predicting weather in places of high population. But storms don't always pass directly over existing data-collection points, so many important weather events simply are not sampled. This lack of data causes problems for both weather research and day-to-day forecasting.

To address this need, Carroll has developed a series of mobile mesonets — high-grade portable weather stations that feature a wireless plug-and-play design, easy attachment to any after-market car roof rack, and the ability to collect a whole spectrum of weather data after just two clicks on a laptop computer. The mesonet concept itself is not unique, but Carroll's plan for the next generation of his mesonet design is: the capacity to transmit data to the National Weather Service in real time.

By increasing the amount of ground data available, Carroll hopes that meteorologists will be able to better understand the relationship between storm conditions in the atmosphere and the terrain below. Ultimately, this will lead to more accurate and easily verified weather warnings, which will increase public safety; if storm warnings include the actual speeds of local damaging winds, the public will be more apt to take shelter than when warnings are less specific. "The mesonet will give us more insight into storm behavior, and transmitting that information to the National Weather Service will aid public safety," Carroll explains. "This project is part of Virginia Tech's mission statement, 'That I May Serve.'"

That is the core commonality among the work of Prociv, Ellis, and Carroll. Using GIS tools to look at the big picture of terrain-atmosphere interactions, these scientists hope to make a difference in both the world of research and in the lives of ordinary people. In a world controlled by weather, these meteorologists are helping us to better understand and cope with its power.

 

A supercell thunderstorm takes over the wide-open panorama of the Great Plains during the 2010 Hokie Storm Chase.

This radar image shows the rainfall intensity of the Blacksburg storm at 1:30 a.m. on April 28, 2011. At that time, the storm was most intense in the Pearisburg, Va., area, but the storm's center would later move to within 10 miles of Blacksburg. Photo by Will Chong.

Kathryn Prociv tests her arms against the strength of a supercell thunderstorm near Bowdle, S.D. Though declining in strength at the time of the photo, the storm had produced an EF-4 tornado, a designation meaning that it had three-second gusts of 166-200 miles per hour. Photo by Dave Carroll.

Students gain valuable experience as a result of the geography department's partnership with the National Weather Service Forecast Office in Blacksburg.

This prototype mesonet probe automatically records a range of weather data at two-second intervals. The data is then available for real-time assessment as well as later research and analysis. Photo by Dave Carroll.

An hour after intercepting an EF-4 tornado from this storm, the 2010 storm chase crew continues to observe the impressive supercell as it passes over Edmonds County, S.D. Photo by Will Chong.