The National Weather Service (NWS) is a component of the National Oceanic and Atmospheric Administration (NOAA), within the Department of Commerce. NWS’ basic mission is to provide weather and flood warnings, public forecasts, and advisories primarily for the protection of life and property. NWS’ operations also support other agencies’ missions and the nation’s commercial interests. For example, NWS provides specialized forecasts to support aviation safety and the agricultural and marine industries. To carry out its mission, NWS uses a variety of systems and manual processes to collect, process, and disseminate weather data to and among its network of field offices and regional and national centers. Many of these systems and processes are outdated. For example, some radar equipment currently in use dates back to 1957. These radars experience frequent and long-lasting outages, and some replacement parts are no longer available. During the 1980s, NWS initiated a program to modernize its systems and restructure its field offices. The goals of this modernization program are to achieve more uniform weather services across the nation, improve forecasts, provide more reliable detection and prediction of severe weather and flooding, permit more cost-effective operations, and achieve higher productivity. The modernization program includes four new major system developments: the Next Generation Weather Radar (NEXRAD), the Next Generation Geostationary Operational Environmental Satellite (GOES-Next), the Advanced Weather Interactive Processing System (AWIPS), and the Automated Surface Observing System (ASOS). It also includes upgrades to existing systems and several smaller new system development projects. The total cost of the modernization is estimated to exceed $4.5 billion. We have previously reported on NWS’ modernization.Additionally, we designated NWS’ modernization as a high-risk information technology initiative in our 1995 report series on high-risk programs. NWS plans to restructure its field offices in association with the modernization program. This restructuring will consolidate the current field structure of 52 Weather Service Forecast Offices, 204 smaller Weather Service Offices, 13 River Forecast Centers, and 3 National Centers into 118 Weather Forecast Offices, 13 River Forecast Offices, 13 Data Collection Offices, and 9 National Centers. Three other agencies are participating with NWS in the modernization. The Federal Aviation Administration (FAA) and the Department of Defense (DOD) are major users of weather data and have formed tri-agency programs with NWS to manage and fund the development and deployment of both NEXRAD and ASOS. Similarly, the National Aeronautics and Space Administration (NASA) is managing the development and procurement of GOES-Next. Because of the importance of timely and accurate weather forecasts and warnings to our nation’s commerce and its citizens’ safety, the Congress has been keenly interested in the modernization, particularly in preserving the existing quality of weather service. As a result, the Congress passed Public Law 100-685 in 1988, and Public Law 102-567, Title VII, in 1992. This legislation states that the Secretary of Commerce shall not close, consolidate, automate, or relocate any field office until the Secretary certifies to the Congress that such action will not result in any degradation of weather service to the public. ASOS is a system of sensors, computers, display units, and communications equipment intended to automate the ground-based observation and dissemination of weather information nationwide. This weather information includes data on temperature and dew point, visibility, wind speed and direction, pressure, cloud height and amount, and types and amounts of precipitation. Figure 1.1 depicts the specified configuration of ASOS sensors and describes their functions. According to NWS, ASOS offers considerable advantages over the current manual surface observation practices, including uniform measurements across all sites and times, continuous observation and reporting, and more observing sites nationwide. ASOS is also intended to eventually replace human observers at weather service offices and at airports. However, ASOS is not designed to detect all weather conditions that human observers have historically provided. Weather conditions that ASOS does not observe include thunderstorms, tornadoes, volcanic ash, hail, virga, snow amount and depth, cloud layers above 12,000 feet, ice pellets, drizzle, blowing snow, blowing dust, and blowing sand. NWS plans to continue to provide this information to its users through a combination of remote sensing systems (e.g., radar, satellite, and lightning detection system), additional ASOS sensors, and manual observation by non weather service observers, such as volunteers, on-call cooperators, and/or FAA personnel. NOAA, as the lead agency on the ASOS program, has contracted with AAI Corporation to purchase a minimum of 868 units, with an option to buy an additional 832 units. Through the base contract, NWS, FAA, and DOD plan to procure 245, 537, and 86 ASOS units, respectively. As of December 1994, NWS had purchased 617 units for the three agencies. Of these, 491 have been accepted, and 47 have been commissioned. NWS commissions a system when it provides the official weather observation. However, human observers still augment ASOS observations at those sites that have historically used human observers. In these cases, the human observers continue to deliver some of the information ASOS cannot provide (such as thunderstorms and tornadoes), and provide correct observations should ASOS err or fail. (Table 1.1 provides more information on the status and number of ASOS units for each agency). NWS plans to purchase and install all 868 units by fiscal year 1997. In June 1993, NOAA estimated that developing and deploying the base ASOS program through fiscal year 1996 for all three agencies would cost about $340 million. NWS now estimates that the base program will cost $351 million through fiscal year 1997 due to FAA changes to the program. The three agencies spent roughly $235 million to develop and deploy ASOS through fiscal year 1994, and plan to spend about $116 million to procure and deploy the remaining ASOS units in the base program through fiscal year 1997. Until an ASOS site is commissioned, human observers are responsible for providing official NWS surface weather observations. These observations are used by meteorologists, hydrologists, climatologists, and the aviation community to provide weather forecasts, research climate changes, and conduct aviation operations. Within the aviation community, these observations are necessary for aircraft to take off, land, or be dispatched to an airport. As part of its modernization and associated restructuring, NWS expects that ASOS will assume most surface observing responsibilities and replace human observers at about 175 weather offices and airports. In addition, according to the FAA manager responsible for defining air traffic requirements for weather sensors, FAA intends for ASOS to replace its contract observers at about 194 sites. To date, neither FAA nor NWS has replaced any of their human weather observers. Three organizations play key roles in the ASOS program. NOAA’s System Acquisition Office is responsible for the ASOS acquisition. NWS’ ASOS program office manages the overall program. Its responsibilities include overseeing system development and deployment, coordinating the program with FAA and the Navy, and investigating system enhancements. Finally, NWS’ Office of Systems Operations (OSO) is responsible for operating and maintaining ASOS systems. Within OSO, ASOS Operations and Monitoring Center (AOMC) is responsible for on-line monitoring of the quality of ASOS observations and dispatching maintenance technicians for operational ASOS units. The objectives of our review were to determine (1) what ASOS problems exist and how effectively NWS is resolving them, (2) the cost of resolving these problems, and (3) whether NWS’ plans for implementing ASOS make sense in light of these problems. To determine what ASOS problems exist, we obtained and analyzed (1) the ASOS program office’s problem report database, (2) summaries of issues compiled by an NWS task team charged with resolving ASOS problems, (3) action plans on problematic sensors developed by this NWS task team, (4) NWS’ system performance reports, (5) relevant FAA Unsatisfactory Condition Reports, (6) relevant NASA Aviation Safety Reporting System reports, (7) ASOS discrepancy reports from two weather service offices and three air traffic control towers that representatives from the National Air Traffic Controllers Association (NATCA) and the National Weather Service Employees Organization (NWSEO) recommended we contact, and (8) ad hoc problem reports and letters from weather observers, air traffic controllers, and air dispatchers; discussed meteorologists’ requirements and system performance with and obtained related documentation from NWS’ Test and Evaluation Branch in Sterling, Virginia; NWS’ Office of Meteorology; 14 NWS weather service offices across the country; and the NWSEO; discussed climatologists’ requirements and system performance with and obtained related documentation from NOAA’s National Climate Data Center, NWS’ Climate Data Continuity Project, the Colorado State University Department of Atmospheric Science, and the ASOS Climate Working Group; and discussed aviation requirements and system performance with and/or obtained related documentation from the National Research Council, FAA’s Air Traffic Plans and Requirements Service, NATCA, the Air Transport Association, the Airline Dispatchers Federation, and 13 individual air traffic controllers from airport towers referred to us by NATCA. To determine the effectiveness of NWS’ problem resolution efforts, we reviewed policies and procedures and interviewed program officials to document NWS’ processes for identifying and resolving ASOS problems, obtained and assessed documentation on problem resolution efforts and discussed these efforts with NWS and FAA program officials, and assessed a random sample of NWS’ database of 499 problem reports to identify (1) how these reports were tracked and their resolution efforts documented and (2) how satisfied the originators of the problem reports were with NWS’ resolution efforts.