The National Weather Service has consistently refused to deal openly with the health issue raised by siting the radar in a residential area.”
In November 1997, the NWS responded to the Rose Institute report and stated that it was “replete with misinformation concerning weather radars, weakly supported opinions, and several paradoxical conclusions.”
Subsequent to that response, the Rose Institute issued another report in May 1998 that expanded on some of the issues raised in its November report, while also raising additional concerns, including whether the Sulphur Mountain NEXRAD coverage is needed since “ninety percent of the area that the Sulphur Mountain tower was installed to cover is covered by other NEXRAD stations.”

	Objectives, Scope, and Methodology

The objectives of our review were to determine whether the Sulphur Mountain NEXRAD (1) can provide timely and accurate information for warning of flash floods and (2) is intended to provide low-level data necessary to predict wind shear for Los Angeles International Airport. compared the timeliness of the flash flood warning lead times to the requirement specified in Commerce’s 1999 Annual Performance Plan, obtained and reviewed Sulphur Mountain NEXRAD availability data from the Engineering Management Reporting System for the period from October 1995 through March 1998 to determine if the Sulphur Mountain radar was meeting the 96 percent availability requirement, reviewed three flash flood events that occurred on February 3, 6, and 23, 1998, to determine how data from the Sulphur Mountain NEXRAD is used in combination with rain gage information to issue flash flood warnings, and interviewed the following users to obtain their views of the quality, timeliness, and utility of the Sulphur Mountain NEXRAD data: officials from the Flood Control Department of the Ventura County Public Works Agency; the Los Angeles County Department of Public Works; Point Mugu Naval Air Warfare Center; U.S. Army Corps of Engineers, Los Angeles District, Reservoir Regulation Section; Ventura County Sheriff’s Department; the Assistant City Administrator from the Emergency Preparedness Division, City of Los Angeles; weathercasters from KCBS-TV and KCAL-TV; and the director of Fox Weather, a private meteorological service. From January 1992 through December 1994, 18 flash flood events were reported in Ventura and Los Angeles counties. However, from January 1995 through February 1998, advanced warnings were issued for 17 of the 22 reported events; and the average warning lead time for these was just over 2 hours. Although NEXRAD is not the only source of data on which storms are tracked, Los Angeles/Oxnard WFO officials told us that the Sulphur Mountain NEXRAD is the primary reason for the increase in advanced warning lead time because it provides advanced warning of heavy precipitation oftentimes before severe weather hits the California coast. NWS headquarters officials acknowledged the availability shortfalls and stated that they are monitoring the failure rates of parts and are attempting to reduce the failure rates or to more quickly replace the parts that fail most often. FAA uses three different systems, either singly or in tandem, to predict wind shear at airports — Terminal Doppler Weather Radar (TDWR), Weather Systems Processor (WSP), and Low Level Wind Shear Alert System (LLWAS). WSP is a modification to FAA’s air traffic control airport surveillance radar (ASR-9) that is to provide FAA with 80 to 95 percent of the capability of TDWR. WSP is to be installed at high to moderate traffic airports that experience limited severe weather. LLWAS is used to supplement TDWR at nine high-traffic airports at greatest risk of severe weather and it is used at other airports that will not get TDWR or WSP—typically lower traffic airports. Los Angeles International currently has LLWAS and since it is an airport designated as having high to moderate traffic that typically experiences limited severe weather, it is scheduled to get WSP in 2001. Conclusions

The accuracy and timeliness of flash flood warning lead times has improved since the Sulphur Mountain NEXRAD was commissioned in December 1994. However, the Sulphur Mountain NEXRAD is not consistently meeting its availability requirement, thus increasing the risk that NWS and other users will not always have the data needed to accurately and quickly predict flash floods and other severe weather.
Why GAO Did This Study

Pursuant to a legislative requirement, GAO reviewed the Rose Institute of Claremont McKenna College's study on the National Weather Service's (NWS) Next Generation Weather Radar (NEXRAD) located on Sulphur Mountain, California, focusing on whether the Sulphur Mountain NEXRAD: (1) can provide timely and accurate information for warning of flash floods; and (2) is intended to provide low-level data necessary to predict wind shear for Los Angeles International Airport.

What GAO Found

GAO noted that: (1) since the Sulphur Mountain NEXRAD was commissioned in December 1994, the accuracy and timeliness of flash flood warnings has improved for Ventura and Los Angeles counties; (2) from January 1992 through December 1994, 18 flash flood events were reported in Ventura and Los Angeles counties; (3) however, from January 1995 through February 1998, advanced warnings were issued for 17 of the 22 reported events; (3) although the Sulphur Mountain radar is not the only source of data on which flash flood warnings are issued, NWS officials believe that the Sulphur Mountain NEXRAD is the primary reason for the increase in advanced warning lead time because it provides advanced warning of heavy precipitation, often before severe weather hits the California coast; (4) users of the Sulphur Mountain NEXRAD data told GAO that the information it provides is valuable, accurate, and timely; (5) despite the improvements in flash flood warning lead time and user satisfaction, NWS data show that the Sulphur Mountain NEXRAD is not consistently meeting its 96-percent availability requirement; (6) from October 1995 through March 1998, the Sulphur Mountain NEXRAD was available as required for 20 months; for the other 10 months, availability ranged between 79 to 95 percent; (7) if the NEXRAD is not available as required, it increases the risk that NWS will not have the data it needs to accurately and quickly predict flash floods and other severe weather; (8) NWS headquarters officials acknowledged the availability shortfalls and stated that they are monitoring the failure rates of parts and are attempting to reduce the failure rates or to more quickly replace the parts that fail most often; (9) predicting wind shear at Los Angeles International Airport is not part of NEXRAD's mission; (10) the Federal Aviation Administration (FAA) uses three different systems to predict wind shear at airports--Terminal Doppler Weather Radar (TDWR), Weather Systems Processor (WSP), and Low Level Wind Shear Alert System (LLWAS); (11) TDWR is being deployed at high traffic airports that experience severe weather; (12) WSP is an enhancement to an existing air traffic control surveillance radar that is to provide FAA with 80 to 95 percent of the capability of TDWR; (13) WSP is to be installed at high to moderate traffic airports that experience limited severe weather; (14) LLWAS is used to supplement TDWR at nine high traffic airports at greatest risk of severe weather and it is used at other airports that will not get TDWR or WSP; and (15) Los Angeles International Airport currently has LLWAS and is scheduled to get WSP in 2001.