Doppler on Wheels (DOW) is a fleet of quickly deployable truck-mounted weather radars managed by FARM (Flexible Array of Radars and Mesonets), an American research company affiliated with the University of Alabama in Huntsville. The group, which started under the University of Oklahoma School of Meteorology before becoming an independent nonprofit research facility in 2003, is led by atmospheric scientists Joshua Wurman and Karen Kosiba. FARM is partially funded by the National Science Foundation as part of the "Community Instruments and Facilities" program. The DOW fleet has been used throughout the United States since 1995 and internationally since 1999 to research hazardous and challenging weather phenomena such as tornadoes, hail, and hurricanes. The name refers to the doppler weather radars mounted on the trucks, which are able to determine precipitation intensity, velocity, and direction by analyzing the frequency shifts of radar returns.
History In 1995, the University of Oklahoma's Meteorological Radar Research Laboratory completed construction of the first Doppler on Wheels 1 (DOW 1). The DOW 1 was specifically designed to be deployed rapidly in the field, allowing Wurman's crew to observe severe weather phenomena at close range. Shortly after its completion, DOW 1 was able to shortly successfully scan its first tornado. Its debut came just in time for VORTEX-95 (Verification of the Origins of Rotation in Tornadoes Experiment), where it helped predict multiple tornadoes.
By March 1998, Wurman, then head of the DOW program, submitted an incorporation request to the Oklahoma Secretary of State. The application was approved on March 24, 1998,Colorado Secretary of State. "Business entity filing image (master file ID 20031035622)". https://www.sos.state.co.us/biz/ViewImage.do?masterFileId=20031035622&fileId=20031035622. Retrieved April 15, 2026. and later revised on January 23, 2003, for approval in Colorado. This process formally established the Center for Severe Weather Research (CSWR), Incorporated, allowing it to operate independently from the University of Oklahoma. Later in 2003, Wurman left the university, reportedly citing 'hatred' towards academic politics.Wurman, Joshua. "Riding the Storm Out." Center for Severe Weather Research. http://www.cswr.org/press/Ridingthestormout.pdf. Retrieved April 15, 2026.
By 1997, he had finally finished constructions on the second-generation DOW, named DOW 2. Like DOW 1, it used an MP-61 pedestal derived from the SCR-584 Radar. DOW 2 was deployed during VORTEX-98, where it demonstrated improved performance over DOW 1. Shortly after DOW 2 became operational, DOW 1 was decommissioned and replaced by DOW 3. DOW 1 was returned to the National Severe Storms Laboratory (NSSL) and used as a vertical atmospheric profiling radar.Wurman, Joshua; Alexander, Charles R.; Robinson, Paul; Richardson, Yvette. "A Dual-Polarization Doppler Weather Radar Observations of Tornadoes and Other Phenomena." Weather and Forecasting, 2003. https://journals.ametsoc.org/view/journals/wefo/18/4/1520-0434_2003_018_0585_adotbb_2_0_co_2.pdf. Retrieved April 15, 2026. It remained in use until 2002, after which it was relocated to the NEXRAD Station KOUN.
DOW 2 was active from 1997 to 2002 and first being used for the Coastal Meteorology Research Program 1997 (CMRP) in Florida. In 1997, DOW 2 and DOW 3 were both able to scan tornadic supercells near Kiefer and Glenpool, Oklahoma, on May 27, 1997. By 1998, DOW 2 and DOW 3 were a part of ROTATE-98. One of ROTATE's major intercepts was the Spencer, South Dakota, F4. On the evening of May 30, 1998, a supercell in southeastern South Dakota produced a series of tornadoes that were observed by DOW 3. The DOW 3 observed the tornadoes from before 8:04 through 8:45 pm local time, including the passage of the F4 tornado through Spencer itself. Winds up to 237mph were estimated by DOW 3.
On May 3, 1999, the DOWs achieved one of the most well-known observations. DOW 2 and DOW 3 were both on hand to observe the Bridge Creek–Moore F5 tornado for ROTATE-99, with DOW 3 being able to estimate winds up to 301mph when the tornado was passing through Bridge–Creek. That same year, DOW 2 was deployed to Switzerland for the Mesoscale Alpine Programme (MAP), studying atmospheric and hydrological processes over mountainous terrain with the goal of better understanding how complex topography impacts weather systems making it the first international deployment for CSWR.
In the 2000s, the Center for Severe Weather Research was featured on TLC in the documentary series Awesome Forces. Episode 4, titled "Tornado Chasers," focused on several storm-chasing groups, including the DOW team at the University of Oklahoma. The episode highlighted their observations of the 1998 Spencer, South Dakota tornado and the 1999 Bridge Creek–Moore tornado using DOW 3. DOW3 was also featured in the show Storm Chasers and featured on France 3 and Canal+ shortly after deployments within the Alps.
DOW 4 was completed in 2000, becoming the first Doppler on Wheels to feature dual polarization, allowing it to scan using horizontal and vertical polarizations simultaneously and thereby better differentiate between types of precipitation. Before being transferred to the National Observatory of Athens, DOW 4 participated in several U.S. research efforts, including Iowa Precipitation Experiments, the CAMEX-4 Keys Area Microphysics Project (KAMP) in early September 2001, and the International H2O Project 2002 (IHOP). IHOP ran for approximately six weeks from May 13 to June 25, 2002, over the Southern Great Plains, with scientists from Europe and the United States collaborating to improve the understanding and forecasting of convection. Cswr Following IHOP, DOW 4 was shipped to Europe, where it was transferred to the Institute of Environmental Research and Sustainable Development (IERSD) of the National Observatory of Athens, subsequently being referred to as the XPOL Mobile Weather Radar or NOA XPOL.
Doppler on Wheels 1
The Doppler on Wheels (DOW) radar program began in 1994 with the goal of fielding a mobile, but fully capable, pencil-beam, scanning, pulsed Doppler radar, with the real-time multiparameter displays, and versatile programmable volume scanning ability typical of stationary weather research systems.
It was constructed from November 1994 to April 1995, in preparation for VORTEX-95. DOW 1 was able to be deployed for the project, and able to observe several tornadoes. DOW 1 was also used for several other research projects, including Small Cumulus Mesoscale Study (SCMS) in Florida in 1995, the FLATLAND/LIFT Boundary Layer Experiment in Illinois in 1996, and a microburst study run by MIT/LL and the FAA in 1996. DOW 1 was decommissioned in 1997, with the creation of DOW 2 and DOW 3.
DOW 1 used the transmitter of a CP-2 radar provided by the National Center for Atmospheric Research, along with a surplus antenna, pedestal, and receiver hardware. It was mounted on a modified Chevrolet G30 flatbed truck, costing roughly $50,000. In 1996, the radar was upgraded with the installation of a new 2.44 meter antenna, replacing the previous 1.88 meter antenna. The new antenna allowed for a decreased beamwidth of 0.93°, improving the radar's overall resolution. This upgraded radar would later be used by DOW 3 upon its completion in 1997.
+ DOW 1 Radar Specifications Tx Power (Peak) 40 kW Antenna Dimension 1.88 m Parabolic (increased to 2.44 m in 1996) Beamwidth (3 dB) 1.22° in 1995 (decreased to 0.93° in 1996) Pulsewidth (μs) 0.5 - 2.0 μs Pulselength (μs) 0.5–1.0 μs in 1995 (decreased to 0.25–1 μs in 1996) Gatelength 70 – 300 m (0.5 - 2.0 μs) (decreased to 25 – 300 m in 1996) PRF 500 – 2300 Hz w/stagger (increased to 500 – 4,000 in 1996) Polarization V Processing PIRAQ-1 Products V, Z, NCP, SW, DCZ Antenna Scan Speed 0 - 30°s - 1 Antenna Scan Modes PPI, RHI, SUR
VORTEX-95 deployment In an article published in the Fall/Winter 1995 NSSL Briefing newsletter, Project VORTEX director Erik Rasmussen discussed why the development of a mobile doppler radar was necessary after shortcomings faced during VORTEX-94 operations. While the mobile mesonets provided key insights into pressure, temperature, and humidity near the surface in the lead up to and during tornadogenesis, they failed to provide a detailed view of three dimensional airflow in the storm and its surrounding regions. Without a detailed view of airflow and conditions above the surface, project VORTEX researchers were unable to observe key ingredients and steps that occur during the formation of a tornado. While a NOAA WP-3 equipped with a C-Band doppler radar and the National Center for Atmospheric Research's ELDORA aircraft equipped with a X-Band doppler radar were used for VORTEX operations in both 1994 and 1995, they only provided data every 300 meters and were therefor unable to document the motion of air within small regions of the storm, especially the mesocyclone. This lack of information also meant that researchers were unable to verify several key hypothesis established prior to field operations.
To obtain data on wind variation and movement from altitudes of 100 meters to 10,000 meters, VORTEX scientists and the NSSL collaborated with University of Oklahoma School of Meteorology Assistant Professor Joshua Wurman, who had spent the past several years developing doppler radar technology at the National Center for Atmospheric Research, to develop a truck mounted doppler radar in time for the VORTEX-95 field campaign. The antenna pedestal and dish were taken from old military missile tracking radars, while the transmitter was provided by the NCAR from a CP-2 research radar. The receiver and signal processor were developed by Mitch Randell and Eric Loew, while the system was mostly built by NSSL technicians Paul Griffin and Dennis Nealson. For their work on the Doppler on Wheels, Griffin and Nealson were awarded the NOAA Bronze Medal. Parts for the Doppler on Wheels were ordered in November and December 1994, with testing taking place during March and April 1995. DOW 1 was first deployed on May 12, and scanned its first tornado just 4 days later on May 16 near Hanston, Kansas. DOW 1 was deployed on a ridge to the south of town and scanned as the tornado progressed for 45 minutes.
On June 2, DOW 1 was deployed to the Dimmitt Texas tornado, where it would scan one of the most studied tornadoes in history. The chase initially started in Friona Texas, where DOW 1, along with the rest of VORTEX-95 intercepted a violent F4 tornado. After dissipating, Rasmussen directed DOW 1, driven by Jerry Straka and operated by Wurman, to drive south towards an intensifying mesocyclone near Dimmitt, Texas. DOW 1 deployed south of town, and was able to start scanning before the tornado touched down. This meant that for the first time, meteorologists were able to observe highly detailed reflectivity and velocity radar data throughout the entire tornadogenesis process. After touching down, the tornado followed an arcing path, which kept it at a constant sub 2 miles from DOW 1. This close range radar intercept, combined with other data collected by probe teams, mobile mesonets, and airborne radar aircraft, resulted in the most comprehensive tornado research dataset ever produced, until VORTEX 2 intercepted the Goshen County, Wyoming EF2 in 2009.
Hurricane Fran