VORTEX involves university, NCAR, UCAR, and government 
scientists in intensive tornado study

by Robert Henson
UCAR Outreach

The largest field program for tornado research in over a decade is using 
instrumented vehicles, balloons, airborne radar, and a variety of 
ground-based sensors to study developing tornadoes in the southern 
Great Plains.  

Much knowledge has been gained to date on the general weather 
patterns that produce tornadic storms.  However, the exact process by 
which a supercell--a long-lived, highly organized severe 
thunderstorm--produces tornadoes is not yet clear.  VORTEX (the 
Verification of the Origins of Rotation in Tornadoes Experiment) is 
designed to document this process through measurements taken by an 
array of instruments much denser than any previously operating in 
and near tornadic thunderstorms.  New forecast techniques for 
tornadoes and severe thunderstorms are also part of VORTEX. The 
experiment is testing 17 specific hypotheses on the formation and 
evolution of tornadoes, each with criteria for confirmation or 
refutation.  This year's field phase (the first of two consecutive spring 
field programs) is being conducted from 1 April to 15 June.

Based at the National Severe Storms Laboratory (NSSL) in Norman, 
Oklahoma, VORTEX field operations will take place over Oklahoma, 
northern Texas, and southern Kansas.  VORTEX is jointly sponsored by 
the National Oceanic and Atmospheric Administration (NOAA) and 
the National Science Foundation (NSF) and is a component of the U.S. 
Weather Research Program (USWRP), an interagency program with 
the objective of improving short-term weather forecasts.  Institutions 
participating in VORTEX include the University of Oklahoma (OU) 
and its Center for the Analysis and Prediction of Storms; NCAR; the 
UCAR Office of Field Project Support (OFPS); NSSL; the University of 
California, Los Angeles; the Universities of Illinois, Massachusetts, and 
Mississippi; the New Mexico Institute of Mining and Technology; 
Texas A&M and Texas Tech Universities; NOAA's National Weather 
Service (NWS); and Canada's Atmosphere Environment Service 
(AES). 

All 15 VORTEX vehicles are equipped with top-mounted weather 
stations that report wind speed and direction, humidity, temperature, 
and air pressure every six seconds.  The vehicles' locations are 
determined by Global Positioning System satellites and reported to a 
mobile field coordination center that directs the vehicles' movement.  
Reports of wind speed and direction are automatically corrected for the 
moving vehicles using the satellite data.  A number of scenarios for 
placing and moving the vehicles are related to the stage of 
thunderstorm or tornado development as well as the type of storm.  
All vehicles will be in and near the same storm at the same time.

An airborne Doppler radar aboard a NOAA P-3 aircraft will also gather 
weather data, and one mobile weather-balloon unit and two fixed units 
from NCAR's Atmospheric Technology Division will launch 
radiosondes and collect data using the cross-chain Loran atmospheric 
sounding system (CLASS).  Four other mobile CLASS systems will be 
operated by NSSL.  From 20 to 30 small metallic domes containing 
weather instruments and electric field mills will be placed near 
roadsides ahead of tornadoes to measure their minimum air pressure.

Winds will be measured using two mobile Doppler radars operated by 
Howard Bluestein (OU), who in 1991 detected winds close to 300 miles 
(480 kilometers) per hour in an Oklahoma tornado.  Three 
photography teams will take high-quality movie images of tornadoes 
for later analysis of the three-dimensional wind field using stereo 
photogrammetry.  Other meteorological data will come from existing 
measurement systems, including the state-sponsored Oklahoma 
Mesonet, one of the world's densest surface networks with over 100 
weather stations reporting every 15 minutes.  NWS observational data 
will be combined with the special VORTEX research data and 
catalogued by UCAR's OFPS for on-line access by researchers.	

Forecasters from NSSL, the National Severe Storms Forecast Center, 
other NOAA sites, and AES, will issue one- and two-day outlooks from 
an experimental forecast facility at NSSL and the Norman NWS 
forecast office. 
 
For further information on VORTEX, contact Robert Davies-Jones of 
NSSL (phone: 405-366-0419; Internet: jones@nssl.nssl.uoknor.edu); for 
information on USWRP, contact the head of the program office, 
William Hooke (301-713-0460).