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2 Background HYDROLOGY AND METEOROLOGY PRIOR TO TH E MODERN IZATION PROG RAM The two primary operational responsibilities of the NWS are meteorology and hydrology. In the past, the hydrology and meteorology components of the NWS provided differ- ent services and evolved along divergent paths. Meteorolo- gists and River Forecast Center (RFC) hydrologists often were located in separate offices. Moreover, the RFCs were intended to be insulated from demands for special advice. Consequently, meteorologists and hydrologists had a lim- ited first-hand understanding of the needs of the other. The low levels of sophistication in early numerical weather pre- diction models and conceptually based hydrologic models, as well as the lack of computational power and communica- tion systems to receive and process large amounts of data and produce support products, were technological barriers to a more meaningful interaction between the meteorological and hydrologic components. The need to lower the barriers that inhibited working relationships has long been recog- nized, but the requisite technology and resources were un- available. Figure 2-1 describes the flow of products and guid- ance through NWS offices and staff positions before the cur- rent modernization program. Improved computer and communication systems, along with more powerful observational technologies and greater scientific understanding, have begun to reduce some of the technological barriers between hydrologists and meteorolo- gists. Their respective computer forecast models have be- come more sophisticated, and real-time hydrometeorologi- cal data measured over shorter time intervals have become more readily available. As a result, hydrologic forecasting stands on the threshold of attaining major improvements in forecast accuracy. Despite these advances, the interaction between hydrolo- gists and meteorologists is still not optimal. Educational and technological barriers are part of the problem. Also, NWS operations continue to be adversely impacted by RFC and Weather Service Forecast Office traditions established in past decades. HYDROLOGY AN D M ETEOROLOGY UNDER THE CURRENT MODERNIZATION PROGRAM Advances in both the hydrologic and the atmospheric sci- ences have highlighted the interrelationship between the two disciplines (NRC, 1991a). For example, reliable forecasts of precipitation as well as accurate characterization of current precipitation fielder are critical to the preparation of hydro- logic forecasts (see Box 2-1~. For this reason, the processing of radar precipitation estimates, quality control of these and other environmental observations, and discussions of pre- cipitation forecasts and other important activities in the mod- ernized NWS require that meteorologists and hydrologists work side by side in an efficient and integrated manner. The modernized NWS workforce will continue to have person- nel specifically trained and educated in either meteorology or hydrology, but greater emphasis will be placed on rel- evant formal education, especially on continued training in interdisciplinary topics. To that end the modernized NWS also includes hydrometeorologist personnel who have de- grees primarily in either hydrology or meteorology and who will receive additional and substantial education and train- ing in topics related to their secondary specialty. Hydrometeorology represents a blending of the sciences of meteorology and hydrology. The integration of hydrology and meteorology is to ensure maximum collaboration and interaction between the hydrologic and meteorological func- tions and personnel; it also takes optimum advantage of new NWS technologies to ensure the most accurate and timely NWS hydrologic products. Figure 2-2 depicts the revised flow of products and guid- ance through NWS offices and staff positions under the cur- rent modernization and its associated restructuring. The fig- ure highlights the coupling of capabilities at Weather Fore- cast Offices (WFOs), National Centers for Environmental iCurrent precipitation fields characterize precipitation in terms of both space and time. 9
10 To/From NMC River Forecast Center Hydrologic Forecasters · Flash flood guidance · River forecasts Hydrologic Users l r r l Feedback ASSESSMENT OF HYDROLOGIC AND HYDROMETEOROLOGICAL OPERATIONS AND SERVICES Incoming Stream and Rain Gauge Observations To/From RFC Weather Service Forecast Office · Flash flood watches · Flash flood and river flood warnings · Rainfall forecasts (general) · Limited quantitative precipitation forecasts 1 National Meteorological Center · Quantitative precipitation forecasts · Large-scale computer weather forecasts - | Hydrologic Users ~ - ~ · River and weather forecasts · River and weather warnings ~ · Flash flood warnings and watches ~Y ~ level · Flash flood guidance I · Stream gauge observations J FIGURE 2-1 Flow of hydrologic products and guidance through NWS offices prior to modernization. Prediction (NCEP), and RFCs. It also shows the functional joining of hydrology and meteorology that is essential for improving hydrometeorological services. Some benefits of closer cooperation between hydrologists and meteorologists in the NWS already have been demon- strated in spite of the existing limitations. For example, me- teorologists at Weather Forecast Offices2 provide quantita- tive precipitation forecasts (QPFs) to RFCs during signifi- cant rainfall episodes; some of the WFOs provide QPFs to RFCs on a daily basis. RFCs, in turn, provide hydrologic guidance to WFOs in the form of river forecasts and flash flood and headwater guidance. Collocation of RFCs with WFOs to date has demonstrated that direct personal interaction can enhance office opera- tions. However, even at these collocated offices, potential benefits are not being realized because of limited staffing minimal amounts of cross-training, and obsolescence of some existing equipment. The situation undoubtedly will continue to improve as the modernization program proceeds. (These issues, and possible actions to address them, are dis- cussed in later sections of the report.) 2WFOs will be formally identified as such after the Advanced Weather Interactive Processing System is operational and the staff are in place at Weather Service offices and Weather Service Forecast offices that are lo- cated with or near NEXRADs (Next Generation Weather Radars). Impact of New Technology As new technology is implemented in the NWS, the hydrometeorological services provided by the NWS are expected to improve significantly. With the advent of NEXRAD (Next Generation Weather Radar), the Automated Surface Observing System, new geostationary and polar- orbiting satellites, and the AWIPS (Advanced Weather In- teractive Processing System), the establishment of the new WFOs will foster closer cooperation between hydrologists and meteorologists and enable the production of more accu- rate, site-specific, and timely hydrologic forecasts. The NWS modernization will be complemented with new hydrologic software technologies that include: · the NWS River Forecast System the WFO Hydrologic Forecast System a successor to the present Geostationary Operational Environmental Satellite data distribution system, which will be known as the Hydrometeorological Automated Data System the next-generation RFC computer capability the Advanced Hydrologic Prediction System The implementation of these new technologies presents an opportunity to improve significantly NWS weather and hydrology warning and forecast services in the United States,
12 To/From NCEP River Forecast Center Hydrometeorological Analysis and Support I ntegrated, observed, and forecast data for River Forecast Center basin · Assimilation · Integration · Analysis Hydrologic Forecasters · Flash flood guidance · River forecasts 1 All / Feedback ~ ASSESSMENT OF HYDROLOGIC AND HYDROMETEOROLOGICAL OPERATIONS AND SERVICES NEXRAD ~ ~ Scream Gaunes Local Rain I _ I Gauges Weather Forecast Office Weather Forecast Office Forecasters Precipitation analysis Local quantitative precipitation forecasts & quantitative temperature forecasts Flash flood watches Flash flood and river flood warnings Rainfall forecasts (general) Service Hydrologists · Product quality control · Historical database ,1 ~1 1 i · River and weather forecasts ~ · River and weather warnings I · Flash flood warnings and watches ~ County and · Flash flood guidance I subcounty level · Observed data and analysis J 1 ~1 Hydrologic Users To/From RFC ~ National Centers for Environment:`l Predi`!tinn · Quantitative guidance forecasts · Precipitation (quantitative precipitation forecasts) · Temperature (quantitative temperature forecasts) · Large-scale computer weather forecasts .1 The National Meteorological Center has become part of the National Centers for Environmental Prediction. FIGURE 2-2 Flow of hydrologic products and guidance through NWS offices under current modernization and associated restructuring. the use of advanced processing capabilities. In addition, the increased emphasis on hydrometeorology will be facilitated through a hydrometeorological analysis and support (HAS) function, established as a unit at each RFC, and by the collo- cation of each RFC with a WFO. WFOs should receive real- time advice and improved support products from the RFCs. With these products and the expanded hydrometeorological databases and new technologies, the WFO will be equipped to issue more timely and accurate site-specific watches, warnings,3 and follow-up statements for floods and flash floods, as well as provide other hydrologic services. Addi- tional warning lead times of minutes to hours allow emer- gency managers and other users of NWS products and ser- vices to react more effectively to save lives and help miti- gate economic losses, where possible. The hydrometeorological functions of the NCEP, RFCs, and WFOs in the modernized NWS are outlined in Table 2-1. Many of the functions in each office are dependent on support provided by other offices, as shown in the table. River Forecast Centers The great majority of operational hydrologic activities of the NWS are conducted at the 13 River Forecast Centers. Each RFC is responsible for a specific geographic region. The domains of these operational centers are defined along natural watershed divides and basin boundaries. The area covered by each RFC is large, ranging from 87,660 square miles for the Mid-Atlantic region to over 570,000 square miles for Alaska. Figure 2-3 shows the domain and location of the 13 RFCs, some of which are now located in new of fices. In the modernized NWS, there should be greater inte gration of operational hydrologic and meteorological activi ties. Correspondingly, whereas previously less than half of the RFCs were collocated with Weather Service Offices and Weather Service Forecast Offices, now all of the RFCs are collocated with a WFO to foster integrated hydrometeoro logical operations. Approximately 200 people staff RFCs nationwide; each center will have 14 to 19 technical personnel who perform operational duties. RFCs generally will operate 16 hours per day although some HAS functions may extend to 18 hours. 3Flood warnings and watches are worded statements issued to the ' general public (through the news media, emergency managers, National During extreme or unusual hydrologic conditions and as Oceanic and Atmospheric Administration Weather Radio, and a host of needed, the hours of operation may be extended to 24 hours other direct and indirect methods) regarding potential flooding conditions. per day.
14 ASSESSMENT OF HYDROLOGIC AND HYDROMETEOROLOGICAL OPERATIONS AND SERVICES ~'_= / C 1 ~ A/ ~ 1 ~ MU \ ~ \~ \SERFC By WGRFC, ~ ~ RFC Abbrev. RFC Name ABRFC Arkansas-Red Basin River Forecast Center AKRFC Alaska River Forecast Center CBRFC Coloraclo Basin River Forecast Center CNRFC California-Nevada River Forecast Center EMFRC Lower Mississippi River Forecast Center MARFC Miciclle Atlantic River Forecast Center MBRFC Missouri Basin River Forecast Center NCRFC North Central River Forecast Center NERFC Northeast River Forecast Center NWRFC Northwest River Forecast Center OHRFC Ohio River Forecast Center SERFC Southeast River Forecast Center WGRFC West Gulf River Forecast Center FIGURE 2-3 River Forecast Centers. Source: NWS (1996a). RFC Area (sq. ml.) 208,200 570,800 303,450 239,424 209,310 87,660 509,550 325,608 106,020 285,786 178,180 257,850 403,016
BA CKGRO UND River Forecast Center Operational Responsibilities. As the main regional center for hydrology, each RFC will have both real-time and non-real-time operational responsibilities (see Larson et al., 1995~. These activities are mostly in sup- port of flood hazard mitigation through improved flood warnings and water management. They include assimilation of observations, modeling and forecasting, interaction with the user community, and training. The responsibilities of RFCs are summarized as follows: · continuous (storm and interstorm) modeling of stream discharges and water levels for flood warning and water management activities development of guidance products for support of WFOs and communication with these offices through HAS functions · technical support and interaction with relevant agen- cies, promotion of cooperative training, research and internship programs, and operational test and evalua- tion activities . The key organizational feature of operational hydrology in the modernized NWS is the consolidation of most of the hydrologic data assimilation, forecasting, and development activities in RFCs. RFCs serve as the regional centers for the assimilation of real-time hydrologic observations from WFOs and the venous observation networks. They also re- ceive guidance products from national centers. RFC staff assimilate the venous data into useful products that can be integrated into forecast models at RFCs and WFOs. Thus, the hydrologic operations at WFOs are guided by RFCs. Hydrologic Forecaster Functions Perform daily hydro- logic forecast operations Perform extended- range hydrologic forecast operations Conduct hydrologic procedure development activities (model calibration, develop new model components, etc.) Conduct in-depth hydrologic analysis 15 River Forecast Center Staff Roles. There are a number of key technical and managerial positions at RFCs that warrant description. Overall management of RFC operations is supervised by the hydrologist in charge who is responsible for implementing RFC functions. Within the RFC, the hydrologist in charge supports academic liaison activities, media relations, and interagency cooperative projects. The hydrologist in charge is also in charge of training programs that support operational hydrologic activities of both the RFC and WFO. Hydrometeorological analysis and support (HAS) is an important and central new role in RFCs, which is conducted primarily by HAS forecasters. The operational duties of HAS forecasters (see Figure 2-4) are essential to the role of the RFC in the modernized NWS. The range of responsibilities reflects the critical tasks assigned to RFCs to assimilate ob- servations from venous sources and to prepare the data for use in operational models. The assimilation of information from diverse sources and the preparation of data to initialize and update hydrologic forecast models is at the core of mod- ernized hydrologic operations in the NWS. Thus the RFCs generally, and the HAS forecaster in particular, are critical links in blending the necessary expertise, technology, and management so that a primary thrust of NWS modernization can be advanced. HAS analyses are based on forecasts and observations received from the WFO, as well as from national centers (such as NCEP guidance). In turn, they support WFO needs for hydrologic guidance. This two-way interaction between the RFC and WFO in NWS field operations was designed to Basic HAS Functions Assimilate WSR-88D precipitation, other hydrometeorological fields Assimilate QPFs, other hydrometeorological forecasts Produce hydro products Foster interaction and cooperative support between RFC and WFOs . . . meteorological discussion improvement activities Conduct in-depth meteorological analysis ~ . ~ "AO Forecaster Functions Conduct hydrometeorological verification activities Lead hydrometeorological collaboration activities with WFO stabs Conduct hydrometeorological technique development and FIGURE 2-4 Unique and overlapping aspects of hydrologic forecaster and HAS forecaster functions in the modernized NWS. Source: NWS (1996a).
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16 ASSESSMENT OF HYDROLOGIC AND HYDROMETEOROLOGICAL OPERATIONS AND SERVICES overcome the technical, scientific, and interoffice barriers that have prevailed for decades. The success of this interac- tion is a critical component of the modernized NWS. Beyond the production of routine discussion and guid- ance products, HAS personnel are also charged with prepar- ing forecast discussions, leading WFO-RFC interactions, and assisting with user support in each local community. Additional major duties of the HAS in the RFC include veri- fication and evaluation of hydrometeorological products and coordination with other agencies that maintain observation networks. HAS forecasters also support cross-training and other important ancillary interactions between RFC and WFO personnel in collocated offices. Development and operations hydrologist personnel at RFCs are responsible for the implementation and mainte- nance of the integrated technologies in the RFC. At each RFC they guide systems development and software modifi- cation projects. In this capacity, they work with the Hydro- logic Research Laboratory4 to develop and integrate new software applications. Thus, like the science operations of- ficer at a WFO, the development and operations hydrologist personnel are the in-house focal points for research and de- velopment at the RFCs. Daily hydrologic forecast operations at a RFC are per- formed by a team of hydrologic forecasters. They work rou- tinely with others in the RFC to integrate observations and precipitation forecasts into hydrologic models to produce river flow and crest predictions, flash flood guidance, and other products. Hydrologic forecasters use available fore- cast and modeling tools to predict and update continuous flow conditions at river forecast locations as well as to up- date flash flood guidance several times daily for use by WFOs in the development of their own local forecast prod- ucts. Hydrologic forecasters also conduct hydrologic devel- opment activities (e.g., to improve the calibration of hydro- logic models) and perform in-depth hydrologic analyses in support of these developments. Figure 2-4 contrasts the du- ties of the HAS forecasters with those of the hydrologic fore- casters within an RFC. Weather Forecast Offices WFOs are responsible for issuing hydrometeorological forecasts and warnings for the public. Hydrologic forecasts and warnings are part of these services. The 119 WFOs in the modernized NWS represent a doubling of field offices with hydrologic service area (HSA) responsibilities. With the guidance communicated from RFCs and with the hy- drometeorological training and software applications pro- vided to WFO forecasters, WFOs are charged with issuing hydrologic forecasts and warnings for the public and the broad user community. At the core of this new organization 4The laboratory is under the administrative management of the NWS Office of Hydrology. is the WFO Hydrologic Forecast System (WHFS), a computer- based tool that will enable WFO forecasters to communicate with the RFCs and perform key operational hydrology duties for the service area. (For example, responsibility for the zero to six-hour-lead flash flood forecast is assigned to the WFO, which uses guidance provided from the RFC.) See a further discussion of the WHFS in Chapter 3. Eighty of the 119 WFOs will have a service hydrologist on site.5 The service hydrologists are considered to be the leaders of the hydrology program at WFOs. In this capacity, they mainly provide technical and administrative support for the hydrology program. Service hydrologists will continue to be the primary managers of the WFO hydrologic program, but their responsibility in the modernized NWS will take on new dimensions. They will serve as the resident expert in each WFO on certain aspects of the new hydrometeorologi- cal technologies and will provide leadership in the internal and external execution and coordination of the WFO hydrol- ogy program. The service hydrologist in a WFO (along with a warning coordination meteorologist) will also perform liaison activities with the user community and the public. He or she must determine the service requirements for the WFO USA. The boundaries of WFO HSAs and RFC basins do not necessarily coincide; thus some WFOs will regularly com- municate and exchange data with more than one RFC. The WFO provides RFCs with hourly NEXRAD estimates of "ridded precipitation accumulation, "ridded quantitative pre- cipitation and temperature forecasts (QPFs and QTFs), hy- drologic observations, hydrometeorological data reports, and river and precipitation observation summaries. The RFCs assimilate the data and use them in hydrologic models. In turn, the RFCs provide flash flood and headwater guidance to WFOs in support of the flash flood programs. The WFOs produce flood watches, warnings and statements, flood and water supply outlooks, river recreation and ice statements, and area weather updates as part of the hydrology products intended for the public and user community. The WHFS and the training to use the hydrometeorologi- cal application are central to the hydrology program at WFOs. The service hydrologist is also responsible for cali- brating and modifying the WHFS procedures. Maintaining the calibration and verification databases and updating the E-19s6 for the HSA are principal responsibilities of the ser- vice hydrologist. 5That is, 80 WFOs have a service hydrologist assigned specifically to them, but these 80 service hydrologists will manage and support the hydro- logic warning, forecast, and information programs at all ~19 WFOs. 6E-19s are standardized forms that report historical observations on streams and rivers. Information on past flood stages-especially with refer- ence to local landmarks, floodplain inundation patterns, and major land-use changes is noted in E-19s. These and other reports contained in E-19s are important in the generation of worded forecasts that facilitate effective com- munication with the public.
BA CKGRO UND The two-way exchange of data between WFOs and RFCs, reliance on AWIPS hardware and software, and integrated hydrometeorological training for NWS personnel are the foundations of modernized operational hydrology in the NWS. Nonetheless, other components of the system, such as national and regional centers, training centers, and special programs, provide crucial support for the implementation, operation, and maintenance of modernized NWS services. National Centers for Environmental Prediction The NCEP is a network of centers that provide central, national- and regional-level meteorological forecast guid- ance, near-real-time climatic analysis, model and procedure development, and centralized computer support for the NWS. NCEP centers include: · NCEP Central Operations · Environmental Modeling Center · Hydrometeorological Prediction Center · Marine Prediction Center · Climate Prediction Center · Aviation Weather Center · Storm Prediction Center · Tropical Prediction Center NCEP products are distributed to field forecast offices of the NWS, the U.S. Air Force, the Federal Aviation Administra- tion, and other governmental and nongovernmental offices. For the NWS, an important NCEP product is gridded,7 short-term weather forecasts produced by numerical weather prediction models. These models include QPF and QTF fore- casts that are highly valuable in hydrologic prediction. The numerical weather prediction models produce forecasts of evolving weather systems that rely heavily on the daily avail- ability of observation data for the initial conditions used in the models' algorithms. Some of these data are derived from observations that are processed at RFCs and WFOs and sent to the NCEP on a regular basis. WFO forecasters modify the forecast fields and tailor them for regional hydrologic appli- cations. Table 2-1 lists the functions of the NCEP that are relevant to hydrology. Supporting Programs and Activities The improvements in hydrologic and hydrometeorologi- cal products and services in the modernized NWS depend on far more than just streamlining the specialized operations in regional centers. Improved warnings and forecasts, espe- cially short-term (zero to six-hour) events that occur on small regional and local scales, rely on advanced tools (such as the AWIPS, NEXRAD, and various environmental monitoring devices) and the research and development that produces 7Grid refers to evenly spaced points at which numerical models provide temperature, wind, or other weather data for use by forecasters in producing weather forecasts and warnings for the nation. 17 them. Adequate training in the use of new technologies and in the requisite interoffice communication of data and inter- mediate products are also essential ingredients of improved warnings and forecasts. Environmental Monitoring Modernized hydrologic operations in the NWS are built on the availability of high-quality observations and fore- casts of fields of specific variables. These observations, available at frequent time intervals, are used in continuous river-flow modeling and in the production of flash flood guidance at RFCs. Key among these data are QPFs (see Chapter 3) and NEXRAD-derived estimates of precipita- tion. Hydrologic and flood guidance models then partition these precipitation fields between infiltration (soil storage) and rainfall excess (or runoff). The results, when routed over the basin, form the basis for stream-flow forecasts. Clearly the accuracy of the hydrologic forecast is highly dependent on the accuracy and reliability of the observed and fore- casted precipitation fields. NEXRAD precipitation estimates are clearly among the main sources of data for hydrologic forecasts. However, telemetered data from rain gauges also contribute signifi- cantly to NEXRAD's Precipitation Processing System, which provides "calibrated" precipitation estimates to RFC forecasters. Many of the rain gauges are owned and operated by partner agencies that share data with the NWS. These partnerships are vitally important to hydrology and hydro- meteorology operations in the modernized NWS. These di- verse observations are especially important in the continu- ous modeling of soil moisture, snow accumulation, and snow ablation.8 An absolutely critical source of input data for NWS hy- drology derives from river gauges, most of which are oper- ated by the U.S. Geological Survey. (Some of these gauges are managed under partnerships with other local, state, and federal agencies.) Almost all NWS river forecasts are made specifically for sites where river gauges are located. The data from these reporting stream gauges are used for both fore- cast updates and verification. The NWS acquires observations from surface rain and river gauges through a variety of reporting networks. Auto- mated Surface Observing Systems (ASOSs) are being in- stalled at over 850 locations across the United States. This network will nearly double the number of full-time surface weather observing locations and updates observations every minute, 24 hours every day of the year. Unfortunately, the majority of these gauges are still read manually, and thus observations are updated only a few times during each 24- hour period. A smaller but growing subset of these critical gauge observations are acquired on a four to six-hour basis ~Ablation, or loss, occurs in snow by either sublimation (evaporation from solid to vapor) or by melting.
18 ASSESSMENT OF HYDROLOGIC AND HYDROMETEOROLOGICAL OPERATIONS AND SERVICES through satellite interrogation or by remote telephone ac- cess. Some community networks provide their data to the NWS on an hourly basis. This is a continual effort on the part of the NWS which is required to ensure the flow of these critical gauge reports from diverse sources to allow calibra- tion of both the precipitation estimates from NEXRAD and the stream-flow forecasts from hydrologic models. Satellite observations also are used in NWS hydrologic and hydrometeorological operations. The NWS plans to test and use are al coverage of precipitation estimates based on satellite information to correct for anomalous propagation in NEXRAD reflectivity observations. Another important use of satellite observations is in support of snow accumulation and ablation modeling. Snow observations from various sensors and sources are assimilated into comprehensive guidance products for RFCs at the National Operational Hydrologic Remote Sensing Center (NOHRSC) located in Chanhassen, Minnesota. The NOHRSC operates as part of the NWS Office of Hydrology and makes extensive use of satellite data to estimate nationally the are al extent and liquid-water equivalent of snow. This center also relies heavily on observations from two gamma-ray detection sys- tems mounted on low-flying aircraft. Over 1,600 flight routes that cover portions of 25 states and 7 Canadian provinces are maintained by the NOHRSC. The snow coverage products provided by the NOHRSC are vital to hydrologic forecast- ing at RFCs and WFOs, especially during periods of rapid snowmelt. Research and Development Research and development on hydrologic forecast sys- tems, observation systems, and related computer algorithms are primarily the responsibilities of the Hydrologic Research Laboratory, which is part of the NWS Office of Hydrology. Research and development are also performed at RFCs by field personnel. University research has played an important role in the development of models and algorithms for NWS systems. The development and testing of the new Precipita- tion Processing System, for example, has been largely com- pleted by the NWS Office of Hydrology in cooperation with university researchers. Similarly, work on hydrologic mod- eling, which uses the next generation of hydrologic models known as distributed models, and automatic calibration pro- cedures have been performed at both the Hydrologic Re- search Laboratory and research universities. Further discus- sion and conclusions regarding the NWS research and de- velopment program are provided in Chapter 4.