Q. What is VORTEX?
A. VORTEX (Verification of the Origins of Rotation in Tornadoes EXperiment) is a field project, with the primary purpose to investigate tornadoes. The field phase was held in the central and southern Plains of the U.S. from 1 April-15 June of 1994 and 1995. The area of primary focus was bounded approximately by latitude 32-38 N and longitude 95-102 W. Analysis of data will take many years.
Q. Who was involved?
A. VORTEX was hosted by the National Oceanic and Atmospheric Administration's (NOAA) National Severe Storms Laboratory (NSSL) and involved the collaboration of NSSL and scientists from a number of universities (including the University of Oklahoma, Texas A&M University, the University of Illinois, Texas Tech University, the University of California at Los Angeles, West Virginia University, the South Dakota School of Mines and Technology (SDSMT) the New Mexico Institute of Technology, the University of Mississippi, and Southwest Missouri State University), the National Center for Atmospheric Research (NCAR), the National Science Foundation (NSF), NOAA's National Weather Service (NWS), and the Atmospheric Environment Service of Environment Canada (AES). More than 75 scientists took part. Funding was provided primarily by NOAA and the NSF.
Q. What are the objectives?
A. Perhaps one of the most unique features of VORTEX, in comparison with other recent meteorological field projects, was that the objectives were cast in terms of testable, refutable hypotheses. A total of 17 hypotheses were developed by the principal investigators. As a result of this approach, the project was more narrowly focused than other recent projects.
The primary objectives of the field portion of the exercise can be grouped as follows:
*hypotheses related to the role of the environment
*hypotheses related to tornadogenesis
*hypotheses related to tornado dynamics
*hypotheses related to tornado debris depositionIn addition, there are adjunct experiments, many dealing with atmospheric electricity, which were carried out only when they did not interfere with the primary objectives.
Forecasting for the experiment was led by a small group of forecasters focusing only on the development of tornadic storms. The forecasters tested various new operational techniques with a view to improving forecasting and warning operations. Forecasters came from NSSL, NWS local offices, the Severe Local Storms Branch of the National Severe Storms Forecast Center (SELS) (now the Storm Prediction Center Operational Guidance Branch), and AES.
Q. What field operations were carried out?
A. Up to 20 ground-based vehicles and 3 aircraft operated on any given day. Primary tasks involved mobile ballooning, mobile vehicle observations of standard meteorological variables in the storm and environment, radar observations, and the rapid deployment of portable surface observing instruments known as "turtles."
There were two primary kinds of ground-based vehicles: Five vans capable of launching weather balloons in the field and twelve sedans. In addition, a field coordinator's van equipped with a computer monitored the location of all the other vehicles and interesting weather phenomena.
All of the vehicles were equipped with sensors to measure the temperature, humidity, winds, and pressure in the atmosphere every six seconds. These observations form the mobile mesonet. For the second half of the 1995 field operations, a mobile Doppler radar "Doppler on Wheels" was used. Designed primarily by Josh Wurman of the University of Oklahoma and built by engineers from NSSL with support from NCAR, it was mounted on the back of a truck and allowed scientists to drive to within a few miles of storms and collect detailed information on storm reflectivity and velocity. The Doppler on Wheels collected some of the most spectacular data gathered in VORTEX.
The aircraft for 1995 included a NOAA P-3 (also used for hurricane reconnaissance) and the NCAR Electra. Both had belly radars, scanning horizontally to gather information on the reflectivity structure of storms, and tail radars, scanning vertically with Doppler radar to get reflectivity and wind information on storms. These aircraft were flown in such a way that dual Doppler analysis of the wind data is possible. A third aircraft, an armor-plated T-43 from the SDSMT, could penetrate storms when they were within viewing distance of the NSSL Cimmaron research radar west of Oklahoma City to gather information on microphysics within storms.
The goal of the project was to focus all of the resources on one storm each operational day, trying to capture its entire life cycle from initiation to dissipation. Thus, scientists remained on a storm even after it had "tornadoed," even if there were other storms in the vicinity that still had the potential to produce tornadoes. It is very important to collect complete data sets, even on 'null' cases. Because of safety considerations, storm intercept operations ceased at sunset.
Field operations were carried out with a field coordinator, Erik Rasmussen, in one of the vehicles. He was ultimately responsible for all decisions (other than safety) in the field.
Q. How did operations go?
A. 1994 was a near record year for fewest number of tornadoes in the VORTEX area. Nevertheless, VORTEX collected data on several supercell thunderstorms, although no tornadoes were intercepted that logistically allowed scientists to deploy the mobile mesonet. VORTEX operated on 18 days in 1994, collecting data on storms on 9 days. An operations summary is available on the World Wide Web at ( http://www.ofps.ucar.edu/data/vortex/html/vtx_summary.html).
In 1995, VORTEX operated on 18 days, collecting data on 13 of those days. A total of 9 tornadoes were intercepted (17 April near Temple, Oklahoma, 3 on 16 May in southwestern Kansas, 2 on 2 June at Friona and Dimmitt, Texas, and 3 on 8 June at Wheeler, Allison, and southeast of Allison, Texas). The two tornadoes on 2 June and two of the tornadoes on 8 June were large, violent tornadoes. An operations summary is available on the World Wide Web at ( http://www.ofps.ucar.edu/data/vortex_95/html/vtx_summary.html )
Q. What has been learned?
A. Analysis of VORTEX data will take many years. The "easy" part of the project, collecting the data, is over. Results are beginning to appear in the scientific literature (one paper on the 29 May 1994 Newcastle, Texas, tornadic storm has appeared in Monthly Weather Review) and at conferences. Some of these papers are available on the Web. In general, for the 1995 events, the scientists plan to "pair" a tornadic and non-tornadic storm and put efforts into understanding them. The first pair is the 2 June Dimmitt tornadic storm and the 22 May Shamrock, Texas, non-tornadic storm. The second pair is the 8 June Kellerville/Allison tornadic storm and the Elmwood, Oklahoma, non-tornadic storm. Some individual aspects of the Dimmitt analysis have been completed, notably the upper air balloon observations, the mobile mesonet surface observations, the Doppler on Wheels, and airborne radar components. Components of other days have also been completed. Scientists still need to put all the information into a single 4-dimensional package.
The researchers found some surprising results. The Dimmitt tornado formed without a substantial temperature gradient at the ground, as had been hypothesized. The Dimmitt and Newcastle tornadoes also formed extremely rapidly from the beginning of the storm (~30-40 minutes). Examples were also found (e.g., 2 June 1995) of extremely large gradients in the low level moisture field, not associated with a dry line, but which might have significant impact on the environment a storm "sees."
The researchers collected data that will address many of the hypotheses proposed in VORTEX. Putting everything together is not a fast process, particularly since the researchers are dealing with new data sources (the mobile mesonet and Doppler on Wheels). However, they are confident that over the next few years, our understanding of tornadic storms will be improved as the result of VORTEX. Already, some new explanations of aspects of tornadic behavior have been proposed. They await testing with theoretical understanding and more VORTEX cases.
File: vortex.faq
NSSL (5/96)