WSR-74

WSR-74C radar from Central Illinois WFO

WSR-74 radars were Weather Surveillance Radars designed in 1974 for the National Weather Service. They were added to the existing network of the WSR-57 model to improve forecasts and severe weather warnings. Some have been sold to other countries like Australia, Greece, and Pakistan.

Radar properties

There are two types in the WSR-74 series, which are almost identical except for operating frequency.^[1] The WSR-74C (used for local warnings) operates in the C band, and the WSR-74S (used in the national network) operates in the S band (like the WSR-57 and the current WSR-88D). S band frequencies are better suited because they are not attenuated significantly in heavy rain while the C Band is strongly attenuated.

The WSR-74C uses a wavelength of 5.4 cm.^[2] It also has a dish diameter of 8 feet, and a maximum range of 579 km (313 nm) as it was used only for reflectivities (see Doppler dilemma).

History

WSR-74C Radar in Darwin, Northern Territory Australia

The WSR-57 network was very spread out, with 66 radars to cover the entire country. There was little to no overlap in case one of these vacuum-tube radars went down for maintenance. The WSR-74 was introduced as a "gap filler", as well as an updated radar that, among other things, was transistor-based.^[3] In the early 1970s, Enterprise Electronics Corporation (EEC), based out of Enterprise, Alabama won the contract to design, manufacture, test, and deliver the entire WSR-74 radar network (both C and S-Band versions).

WSR-74C radars were generally local-use radars that didn't operate unless severe weather was expected, while WSR-74S radars were generally used to replace WSR-57 radars in the national weather surveillance network. When a network radar went down, a nearby local radar might have to supply updates like a network radar.^[4] NWS Lubbock received the first WSR-74C in August 1973 following widespread attention from the Lubbock F5 tornado of 1970.^[5]

128^[6] of the WSR-57 and WSR-74 model radars were spread across the country as the National Weather Service's radar network until the 1990s. They were gradually replaced by the WSR-88D model (Weather Surveillance Radar - 1988, Doppler), constituting the NEXRAD network. The WSR-74 had served the NWS for two decades.

Twelve WSR-74Cs still have not been decommissioned and, of those, seven remain in active use today. The last WSR-74C used by the NWS was located in Williston, ND, before being decommissioned at the end of 2012.^[7] No WSR-74Ss are in the NWS inventory today, having been replaced by the WSR-88D. Some of these radars are in commercial use.

Radar sites in the US

Circles showing the coverage of the WSR-57 and WSR-74 radars. Note the large gap over the western United States.

WSR-74 sites include the following two categories:^[8][9]

See also

References

1. ↑ "Advanced Search - ITS" (PDF). bldrdoc.gov. Retrieved 19 March 2015. 
2. ↑ Paul Sirvatka. "WSR - Weather Surveillance Radar." Radar. College of DuPage. 4 Apr. 2006 <http://weather.cod.edu/sirvatka/radar.html>.
3. ↑ Roger C. Whiton, et al. "History of Operational Use of Weather Radar by U.S. Weather Services. Part I: The Pre-NEXRAD Era." Weather and Forecasting: Vol. 13, No. 2, pp. 219–243. 19 Feb. 1998. American Meteorological Society. 5 Apr. 2006 <http://ams.allenpress.com/amsonline/?request=get-document&doi=10.1175%2F1520-0434(1998)013%3C0219:HOOUOW%3E2.0.CO%3B2>.
4. ↑ Stormtrack.org Forum 9498
5. ↑ "NWS Lubbock, TX Office History". noaa.gov. Retrieved 19 March 2015. 
6. ↑ http://sysu1.wsicorp.com/unidata/intro.html Archived April 20, 2008, at the Wayback Machine.
7. ↑ "Weather radar shutdown imminent". Williston Herald. Retrieved 19 March 2015. 
8. ↑ "Assessment of Nexrad Coverage and Associated Weather Services". nap.edu. Retrieved 19 March 2015. 
9. ↑ Stormtrack.org Forum 10344