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Home , Doppler radar, NEXRAD, NSSL Doppler

NEXRAD Now An Historical Look at NEXRAD , also known as detection and rang- information for operational purposes. All of these ing, is one of the earlier technological develop- factors really helped to spur the growth of radar ments that had a huge impact on the field of as a science. meteorology. Weather Surveillance Radar-1988, After WWII, the NWS, formally known as the Doppler (WSR-88D) Next Generation Weather Weather Bureau, obtained various aircraft Radar (NEXRAD) has become a staple technology from the Navy. Most of them were AN/APS-2F for the (NWS) to meet radars which stood for Airborne Radar and they the needs of its mission in detecting severe atmo- were modified and put into operation around the spheric features such as tornadoes, hail, and snow U.S. at about 5 per year. These were then renamed squalls. This technology, first used by the military Weather Surveillance Radar (WSR) -1s, -1As, -3s, to detect the movement of objects such as planes and -4s. All of these radars were pretty much the and ships in WWII, is now used in real-time opera- same and differed by some controls and indicators. tions to detect the sorts of atmospheric phenomena The first WSR was installed at , D.C. that could impact public safety and property. Here National Airport on March 12, 1947 and on June 1, we will discuss the historical family line of radars 1947 a second WSR was installed at a NWS office that eventually led to the development of NEXRAD in Wichita, . The radar in Wichita proved its used by the NWS today. worth when it was used to help guide and aircraft The British were actually the first to “develop threatened by into clear skies so it radio-location, direction-finding devices that could could land safely. locate ” through the efforts of Sir WSR radars were all beginning to show their Robert A. Watson-Watt around 1935. Then, in the value in similar circumstances as what became U.S. from 1942-1944, the Institute known as the U.S. Basic Network of Technology’s (MIT) Radiation Laboratory (Rad began to form and expand after 1947. This network Lab) showed that weather could be detected on cer- consisted of the early WSR-series systems, air tain types of radars out to ranges of 150 miles and at force, civil government and cooperative radars. different . Because of this, the Army Eventually radars were being developed specifi- Air Forces Weather Service established a program cally for meteorological use and one of the first was for the use of weather radar. Most U.S radar known as the AN/CPS-9 Detection Radars, research and development was conducted at MIT’s produced by Raytheon Manufacturing Company. Rad Lab during WWII. In addition, because there The CPS-9’s were actually acquired by the Army were air traffic control and harbor defense radars set Continued on Page 32 up on the Atlantic and Pacific sides of Panama, sci- entists from the MIT Rad Lab were able to visit and determine the effects of the atmosphere and useful- ness of radar in observing atmospheric phenom- ena. The early use of this first radar network for weather detection and surveillance led to the recog- nition of many basic features of storm structure and organization and helped to realize the value of this

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Continued from Page 31 Air Forces Weather Service and installed at military about noon. By 2pm on April 5, 1956, the bases all over the world. Studies and research mod- A&M University radar began seeing hook-echoes els of the CPS-9 were also conducted by MIT Rad and University meteorologists were able to call the Lab, as well as by the Signal Laboratory. Bryan Police Department and the College Station As the NWS considered expanding their radar School District to let them know about the impend- network in the 1950s, a few major severe weather ing touchdown of tornadoes. The school district events occurred and lead to the formation of the decided to keep their students in school a bit longer Texas Warning Network and the establish- instead of releasing them at their normal dismissal ment of communications between the NWS offices and this probably saved numerous lives. As one of and local public officials. The NWS agreed to oper- the first known tornado warnings based solely on ate and maintain WSR-1, -1A, -3, or -4s at their radar detection, the value of this technology was offices and to provide warnings to the public when becoming more visible to society as a whole. confirmed sightings were made - establishing vol- Hurricanes became another driver for the instal- unteer spotter networks. Today, a more formal spot- lation of radars. Their design used a ter program called SKYWARN® is run by the NWS known as S-band, which allowed for longer range where volunteers are trained to identify and describe and more power in detection. After some extensive severe local . Since the program formally hurricane-force damage and flooding from 5 started in the 1970s, the information provided by hurricanes in 2 years from 1954-1955, the NWS SKYWARN® spotters, coupled with developed a major budget proposal for Congress to technology, improved satellite and other data, has improve its warning services for hurricanes and enabled NWS to issue more timely and accurate severe weather, which was quickly approved. The warnings for tornadoes, severe thunderstorms and budget included funding for the design, procure- flash floods. ment, installation, and staffing for what became the In 1953, a tornadic feature known as a hook- WSR-57 radar. Raytheon Manufacturing Company shaped echo was first detected by a radar near was selected as the prime contractor; 31 radars were Champaign-Urbana, and a couple of months ordered by the NWS and installed at already exist- later, two additional recordings of these echoes were ing weather service offices beginning in 1959 in made in Waco, Texas and Worcester, Massachusetts. , and ending in the early 1960s. The installation of the WSR radars was a joint While the main purpose was to install these near effort between local, state and the federal govern- coastal areas, eleven of them were installed in the ment, as well as universities. A great example of Midwest to detect severe storms. Fourteen addi- the partnership between the weather service and the tional radars were purchased in the late 60s to local community expand the network east of the . It occurred on April 5, 1956 is also important to note that these newer installa- when a tornado watch tions were placed in locations where weather ser- was issued by a weather vice offices did not already exist. The main focus service office in Kansas was to space the radars out optimally for coverage City for a specific area and continuity with the already existing radars. around Bryan, Texas at Continued on Page 33 page 32

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Continued from Page 32 Some of the major design specifications process radar data and application software for their included an “improved ability to detect storms radars. Eventually more sophisticated algorithms behind intervening rainfall as to observe hurricanes and techniques were developed that were also at great distances.” In 1963 the NWS began to expanded to operational radars and it led to an standardize the performance of the WSR-57s improved knowledge base for the weather forecast- through calibration techniques. The WSR-57 also ers who had come to rely on radar data to do their had a near real-time telephone transmission line for daily jobs. Color monitor technology was also data and eventually a dial-in capability was added introduced, which made it even easier for meteorol- to allow access by military, airline offices and tele- ogists to be able to recognize storm echoes and vision stations, providing radar data remotely. other features. Remote access is still an important part of the radar During this same time, the MIT Rad Lab had network today. been looking at the use of the to As discussed above, the NWS had installed measure target velocities by radar as a potential many conventional, non-Doppler weather radars measurement for wind speeds, but the development around the country but eventually they had to con- of pulse-Doppler technology for operational use sider the technology with which they should replace took a while. In 1971, the first Doppler radar was them due to the aging WSR -1s, -1As, -3s, and -4s. installed at the National Severe Storms Laboratory Spare parts were disappearing and the 1940s tech- (NSSL) in Norman, and in 1973 a sec- nology upon which they were designed was just no ond Doppler radar was installed at Cimarron Air- longer feasible. The Office of the Federal Coordi- port in Oklahoma – both were meant to study the nator for Meteorological Services and Supporting morphology of storms and used S-band frequency. Research began releasing a Federal Plan for By 1976, the Department of Commerce (DOC), Weather Radars and Remote Displays which was Department of Defense (DOD) and the Department used by Congress as a “single source for reviewing of Transportation (DOT) formed the tri-agency the overall Federal program in meteorological ser- Joint Doppler Operational Project (JDOP) to vices and supporting research.” The 1969 edition explore the benefits of Doppler radar observations. indicated that the NWS intended to buy more mod- Doppler radar was considered the next upgrade ern local-warning radars to replace the WSR -1s, - over conventional radar (i.e. WSR-57, -74) because 1As, -3s, and -4s. By fiscal year 1976, the NWS of its ability to “measure the phase difference received funding for 3 years to replace those older between transmitted and received radar signals. radars, and the replacements were manufactured by The rate of change of the phase difference is Enterprise Electronics, which became known as directly proportional to the radial component of tar- WSR-74C. Additionally, Enterprise Electronics get motion relative to radar, which is known as the also manufactured some WSR-74S radars, which Doppler velocity. As Doppler radar scans horizon- were used to fill some remaining gaps for special tally, it measures both reflec- hurricane and heavy detection on the tivity and the component of S-band frequency. target motion along the radar When computer technology began to emerge in beam axis.” This method the 1960s, researchers were able to more efficiently Continued on Page 34 page 33

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Continued from Paged 33 shows a more accurate detection of circulations weather activity to meet their agencies’ missions.” associated with tornadoes and other significant In this report, it was also noted that NEXRAD weather. The JDOP conducted field tests for three would be useful for more than just detecting the years with the NSSL Doppler radars and an Air hazards of severe weather. The JDOP proposed that Force Geophysical Lab Doppler radar in real-time NEXRAD be useful for water resource manage- to test various processing and display capabilities. ment; it would also foster economic value when In 1979, they delivered a final report with recom- used by various industries such as private meteorol- mended specifications for the tri-agencies. ogists, TV stations, and the airlines to name a few. The JDOP reported out seven basic findings for There was also interest internationally for this type the use of Doppler radar. A few of them were: Dop- of data. pler radar is superior to conventional radar and spot- By late 1979, the Federal Committee for Meteo- ters/public reports; Doppler radar can distinguish rological Services and Supporting Research between severe and non-severe thunderstorms at a (FCMSSR) established a Joint Systems Project longer range; the size of a warning area can be Office (JSPO) to run the planning, programming smaller and much more specific due to increased and management of development, procurement and precision by Doppler radar; and average lead time installation of NEXRAD. With the establishment of for detecting storms before occurrence would be the JSPO, key documents such as the joint opera- increased. tional requirements (JOR), NEXRAD technical Finally, the NWS recognized the increased need requirements (NTR) and a research and develop- for standardized training of radar operators since ment plan resulted. All of these fed into the JSPO Doppler radar data was much different from con- Interim Operational Test Facility (IOTF) operations ventional radar data. They specifically noted that set up in Norman, OK to develop many of the con- operators would need an introduction to basic Dop- cepts for what eventually was to become the WSR- pler principles and meteorologists would also need 88D. Beginning in 1982, contracts for concept to be able to interpret velocity data. As a result of development, validation and risk reduction were this, the National Weather Service Training Center awarded and finally, after other various operational (NWSTC) located in Kansas City, MO developed testing and evaluations, Corporation was various foundation courses and intensive short selected as the NEXRAD contractor for full scale courses that eventually became a job requirement production in 1990. for forecasters who were hired by the NWS. The WSR-88D network that exists today is the In mid-1979, the JDOP reported to the House result of a billion-dollar weather service moderniza- Committee on Appropriations proposing that a tion that began in the late 1980s into the early “new weather radar called NEXRAD, which had 1990s. NEXRAD was just one part of the modern- Doppler capability, be ization of observation technologies being incorpo- integrated into a national rated to improve NWS services. In 1995, the system to meet the National Research Council (NRC) stated that requirements concerning “based on an intensive 6-month study, their the location, intensity, and NEXRAD Panel of the National Weather Service movement of hazardous Continued on Page 35 page 34

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Modernization Committee (NWSMC) arrived at a Jenson, C. E. (1975). A Review of Federal Meteo- strong overall conclusion that weather services on a rological Programs for Fiscal Years 1965-1975. national basis will be improved substantially under Bulletin of the American Meteorological Soci- the currently planned NEXRAD network.” It took ety, 208-224. almost eight years from when the first WSR-88D National Weather Service. Skywarn. Retrieved system installation near Norman, Oklahoma in August 2, 2010, from http://www.weather.gov/ 1990 to last operational WSR-88D installment in skywarn/ northern in 1997. It is important to note National Research Council (1995). Assessment of that all agencies (mainly NWS, DOD, and FAA) Nexrad Coverage and Associated Weather Ser- that have weather radar programs are using the vices. Washington, D.C.: National Academy of same radar systems and this has allowed for sub- Sciences. stantial cost savings in sharing new algorithms or NSSL NOAA (1979). Final Report on the Joint other improvements as they are developed. Today, Doppler Project (JDOP) 1976–1978. Norman, there are now 159 operational NEXRAD radar sys- OK: National Severe Storms Laboratory. tems deployed throughout the United States and at Office of the Federal Coordinator for Meteorologi- selected overseas locations. Radar technology and cal Services and Supporting Research (1980). its application to the atmospheric sciences have rev- NEXRAD Next Generation Weather Radar. A olutionized our ability to ‘see’ the weather. By the Report to the House Committee on Appropria- 1990s, the NWS was finally able to provide a sub- tions. Washington. D.C.: WSR-88D Opera- stantial amount of warning time for severe storms tional Support Facility Technical Data Library. to the public in a more consistent manner through- ROC National Weather Service. About the ROC. out the entire United States through the use of Dop- Retrieved August 2, 2010, from http:// pler radar technology. Finally, the current upgrade www.roc.noaa.gov/WSR88D/About.aspx of the WSR-88D weather radars with dual polariza- Whiton, R. C. et al. (1998). History of Operational tion is the next stage of improvements for storm Use of Weather Radar by U.S. Weather Ser- detection and the provision of warnings that will vices. Part I: The Pre-NEXRAD Era. Weather continue to assist our forecasters in the protection and Forecasting, 219-243. of life and property for the citizens of the United Whiton, R. C. et al. (1998). History of Operational States. Use of Weather Radar by U.S. Weather Ser- vices. Part II: Development of Operational References Doppler Weather Radars. Weather and Fore- Best, Jr., Brig. Gen. W., Commander, (1973). casting, 244-252. Radars Over the Hump: Recollections of the First Weather Radar Network. Bulletin of the Andrea J. Bleistein American Meteorological Society, 205-208. NOAA External Affairs Crum, T. and R. Alberty. (1993). The WSR-88D and the WSR-88D Operational Support Facility. Bulletin of the American Meteorological Soci- ety, 1669-1687. page 35