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Executive Summary
Floods are by far the most devastating of all weather-
related hazards in the United States. The National Weather
Service (NWS) is charged by Congress to provide river and
flood forecasts and warnings to the public to protect life and
property and to promote the nation' s economic and environ-
mental well-being (such as through support for water re-
sources management). As part of a modernization of its tech-
nologies and organizational structure, the NWS is undertak-
ing a thorough updating of its hydrologic products and ser-
vices and the activities that produce them.
The role of the 13 River Forecast Centers (RFCs) is be-
coming more central in the provision of hydrologic services,
and the interaction of the RFCs with 119 newly restructured
Weather Forecast Offices (WFOs) will be much closer and
more complex. All RFCs will now be collocated with a
WFO. New technologies such as the Next Generation
Weather Radar (NEXRAD) and the Advanced Weather In-
teractive Processing System (AWIPS) will provide more
detailed and timely data and facilitate the processing of data
into products.
A key feature of the modernization program is the inte-
gration of hydrology and meteorology in a new hydrometeo-
rological focus, which is expected to enable the provision of
more efficient operations and more effective services. As
part of this integration, the NWS has established a hydro-
meteorological analysis and support unit at each RFC to fa-
cilitate the increased emphasis on hydrometeorology and the
interaction with WFOs. The roles and responsibilities of ex-
isting meteorological forecasters and service hydrologists at
WFOs will change in accordance with this enhanced focus
on hydrometeorology.
The National Weather Service Modernization Committee
of the National Research Council undertook a comprehen-
sive assessment of the NWS' plans and progress for the
modernization of hydrologic and hydrometeorological op-
erations and services. The committee's conclusions and rec-
ommendations and their related analysis and rationale are
presented in this report.
The committee commends the NWS for the strides it has
made in modernizing the NWS hydrology program. The ef-
fort has been well planned and diligently pursued. The imple-
mentation of major new hydrologic and meteorological tech-
nologies presents an opportunity to integrate and signifi-
cantly improve NWS weather and hydrology warning and
forecast services (e.g., through an increased focus on hydro-
meteorology).
Although the committee has identified a number of as-
pects of the modernization of the NWS hydrology program
in which improvements are needed, the overall results of its
assessment are quite positive. The modernization is incorpo-
rating recent technological advances into field offices and
thereby laying the groundwork for major benefits to be real-
ized from improved hydrologic products and services. The
availability of new tools and techniques is also having a strong,
positive effect on the spirit and outlook of NWS personnel.
Chapters 1 and 2 of this report provide an introduction
and background information on hydrology and hydrometeo-
rological programs in the NWS. Chapters 3 and 4 contain the
evaluation of the NWS program as well as its management
and operational support and present all of the conclusions
and recommendations. The 40 recommendations in this re-
port cover a wide variety of topics. The committee has placed
a relatively higher priority on 14 of these recommendations,
which are presented consecutively in this summary as found
in Chapters 3 and 4 along with supporting discussion. How-
ever, each of the recommendations in the report is important,
and the reader is urged to review them all. It is important that
each recommendation be understood in the context of the
committee's analysis; therefore, this summary provides the
section heading, and the chapter and recommendation num-
ber where it can be found. It should be noted that the order of
presentation does not imply any ranking or prioritization
among the recommendations. Again, the reader is encour-
aged to review the entire report, especially the conclusions,
recommendations, and supporting information in Chapters 3
and4.
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2
ASSESSMENT OF HYDROLOGIC AND HYDROMETEOROLOGICAL OPERATIONS AND SERVICES
PRECIPITATION PROCESSING SYSTEM
Recommendation 3-1. The NWS should continue its efforts
to incorporate additional real-time precipitation data (both
ground-based and remotely sensed) into hydrologic prod-
ucts and services. The methods used for multisensor detec-
tion and estimation of precipitation should enable accurate
characterization of precipitation patterns that span seasonal,
geographic, and range diversity. A capability to distinguish
reliably between rain and snow must be developed. The Pre-
cipitation Processing System (PPS) methodology should be
upgraded to a more scientifically sound and dynamic meth-
odology to improve seasonal and geographic performance,
especially during light rain and snow events and in moun-
tainous areas.
One of the most important inputs to NWS hydrologic
models is the spatial and temporal distribution of precipita-
tion, derived from a three-stage PPS. Weather radars, along
with rain gauges, have long been used to estimate the amount
of precipitation that falls to the Earth's surface. Although
radar technology and the associated computer processing
have improved immensely in recent years, our knowledge
about the amount of precipitation that actually reaches the
surface remains primitive. As a result, the PPS provides in-
consistent results for certain types of rainfall in different
geographical areas and has seasonal variations as well.
Successful modernization of NWS hydrologic services
depends on the ability of the NEXRAD network to provide
accurate estimates of precipitation that benefit from im-
proved spatial and temporal resolution. Furthermore, the
current approach for analyzing precipitation patterns is
flawed and based on outdated research. It lacks the scientifi-
cally sound and dynamic methodology needed to improve
the seasonal performance of the PPS in light rain or snow
and in mountainous areas.
PRECIPITATION FORECASTS
Recommendation 3-4. The NWS should accelerate its
fledgling efforts to redesign, develop, evaluate, and verify
quantitative precipitation forecasts (QPFs) and probabilistic
QPFs (pQPFs) and assess their use in hydrologic forecast
models across a range of geographic and seasonal condi-
tions. The Office of Hydrology should determine the time
and space resolution of QPFs that hydrologic models require.
Users of products that incorporate QPF data should be kept
informed about these developments and their potential im-
pact on user operations.
QPFs and pQPFs represent, along with NEXRAD, an
opportunity to improve significantly both flash flood pre-
diction and regional runoff estimates that, in turn, impact
hydrologic forecasts for larger basins. Thus they are of great
value for the development of improved hydrologic services
that have longer forecast lead times. However, the produc-
tion of an accurate QPF is considered to be among the most
difficult challenges in operational meteorology. The chal-
lenge increases substantially when hydrologists attempt to
use the QPF as part of the precipitation input to their hydro-
logic models, which require forecasts of spatial coverage and
amount of precipitation.
Significant efforts are required to coordinate the possible
redesign, production, and use of QPFs and pQPFs. In addi-
tion, the current QPF focus to forecast the are al coverage of
precipitation needs to be reevaluated. The impact of a mod-
ernized QPF and pQPF on hydrologic models in various geo-
graphic and seasonal conditions needs to be assessed. These
sets of forecasts need to undergo extensive verification stud-
ies to determine their proper design for a modern-day QPF
(e.g., required time projections and spatial resolution for
hydrologic models of the twenty-first century before QPF
input becomes routine).
FLASH FLOOD GUIDANCE
Recommendation 3-12. The NWS should improve the sci-
entific basis that underpins the forecasting of floods that occur
in the zero to six-hour time frame. WFO and RFC staff should
be enabled to contribute to this effort by facilitating their
access to adequate training, continuing education, and univer-
sity cooperative programs. Furthermore, they should be able to
access state-of-the-art geographic information systems, digi-
tal elevation models, and drainage and land-use data.
The scientific foundations of both flash flood guidance
and threshold runoff (another type of guidance product) are
derived from decades-old techniques that need significant
revisions. Yet few of the existing NWS research programs
are related to operational flood forecasting. In addition,
threshold runoff is currently estimated based on limited data.
The Weather Forecast Office Hydrologic Forecasting Sys-
tem (WHFS), with its capabilities for both site-specific and
area-wide modeling of the flash flood hazard, has great po-
tential for dealing with the zero to six-hour flood problem if
technical and scientific, training, and operational procedures
problems are resolved.
WEATHER FORECAST OFFICE HYDROLOGIC
FORECASTING SYSTEM
Recommendation 3-14. The NWS should reevaluate the
staffing needs of WFOs with regard to their hydrologic re-
sponsibilities. The number of service hydrologists should be
increased so that each WFO has a program leader for WFO
hydrologic operations, at least for the first year or two fol-
lowing implementation of the AWIPS at each field office.
(A related recommendation is provided in the Qualifications
section of this summary.)
Overall, the NWS has done an excellent job of defining
the requirements and planning the staffing needed in the hy-
drology and hydrometeorology functions of the modernized
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EXECUTIVE SUMMARY
NWS. However, although service hydrologists will manage
the hydrology programs at all future WFOs, only 80 of the
planned 1 19 WFOs will have a service hydrologist assigned
full time; these 80 service hydrologists will cover all 119
WFOs. WFO service hydrologists are program leaders within
their offices, not operational forecasters. But most WFO
weather forecasters currently do not perceive hydrology as part
of their operational duties. Furthermore, during severe weather
conditions, hydrometeorological forecasting at WFOs may at
times produce an excessive workload for the planned staffing;
as a result, the use of interactive hydrologic forecast programs
might receive less attention than is warranted. Sufficient staff
must be in place who have the appropriate training to take
advantage of these modernized capabilities.
The committee remains concerned about the vital and in-
creasingly important role that the service hydrologist will play
in the modernized NWS. It is possible that most, if not all,
WFOs may require a full-time position. At offices where
operational tests and evaluations are conducted, additional
hydrologic expertise will be needed to ensure a thorough,
effective test of the new systems and techniques.
Recommendation 3-15. Guidelines and procedures should
be in place to ensure that the hydrologic and hydrometeoro-
logical forecasts meet NWS requirements (e.g., for accuracy
and timeliness) even under the most challenging of opera-
tional circumstances. Operational tests should be performed
to confirm that these requirements are met.
A suite of powerful new software tools has been devel-
oped to assist in the development of guidance and forecast
products. However, during severe weather conditions, WFO
forecasters are concerned primarily with generating severe
weather warning products, which result in the new interac-
tive hydrologic forecast programs receiving less attention
than is warranted. There is a risk that RFC guidance prod-
ucts on flooding potential might sometimes be released to
the user community with little modification or enhancement
by WFO forecasters. The potential is even greater when fac-
tors such as hydraulic structures (e.g., dams), small-scale
land-use patterns, and urban surfaces complicate the local
hydrologic picture.
The full capability of an application such as the WHFS
can be realized only when WFO forecasters are prepared
adequately to deal with hydrologic forecasting during flood
water crises and concurrent severe weather conditions. The
WHFS in particular needs to be tested in the most challeng-
ing of operational environments, for example, during com-
plex, severe weather situations when forecast and warning
workloads are heavy.
DATA ARCH IVING, VERIFICATION,
AND QUALITY ASSURANCE
Recommendation 3-22. The suite of precipitation prod-
ucts produced by the NEXRAD network, along with
3
accompanying surface rain and stream gauge information,
should be archived by the NWS for future use when new
hydrologic models require calibration before they can be
implemented. The NWS should ensure that appropriate ac-
cess, storage, and visualization methods, such as those
planned in the National Oceanic and Atmospheric Adminis-
tration (NOAA) Hydrologic Data System, are developed or
adapted for use with the entire spectrum of hydrologic data.
An essential element of the foundation for future improve-
ments in the NWS hydrologic forecast system is the avail-
ability of a comprehensive data archiving and retrieval sys-
tem. Although the NOAA Hydrologic Data System, now
under development, is expected to meet the data archiving
needs of some NWS operational activities, nevertheless the
current system fails to archive and efficiently retrieve most
of the data that will be needed for twenty-first century im-
provements in NWS hydrology.
A lengthy archive of all basin data is essential to calibrate
hydrologic models (old and new) and improve model perfor-
mance during critical high-water and low-water situations.
For example, hydrologic models can be improved using data
on the distribution in space and time of precipitation that
produced floods or led to drought conditions. Yet NEXRAD
precipitation estimates provide a unique opportunity to pro-
duce hydrologic guidance and forecasts with an unprec-
edented level of detail.
With increasing demands for hydrometeorological data
n an interactive forecast environment, efficient methods for
accessing, storing, and viewing these data are required.
i]
Recommendation 3-23. The NWS should implement and
provide the sustained support that is needed to continue the
development and operation of the National Hydrologic Fore-
cast Verification Program.
An essential ingredient to improve hydrologic services is
an adequate forecast verification system. Such a system must
provide a baseline that documents previous forecast skill lev-
els and also detects small improvements in forecast skills
that result from new models being developed, calibrated, and
implemented.
Currently the verification of hydrologic forecast products
is inadequate. Hydrologic model development and the incor-
poration of new scientific tools into a modernized work en-
vironment should be accompanied by a rigorous verification
program to document what progress has been achieved. The
National Hydrologic Forecast Verification Program is a re-
cent initiative in the NWS and represents an important set of
plans for overcoming verification deficiencies in the hydrol-
ogy program of the NWS.
DATA SOURCE RELIABILITY
Recommendation 3-25. The NWS, along with other federal
agencies and local and state governments, should coordinate
hydrologic and hydrometeorological data requirements, data
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4
ASSESSMENT OF HYDROLOGIC AND HYDROMETEOROLOGICAL OPERATIONS AND SERVICES
collection, and processing. Priorities among these data
should be set and appropriate funding allocated by the par-
ties involved to maintain a consistent, reliable set of data for
national and local flood forecasting programs. The NWS
should exert leadership to forge an explicit partnership for
sharing these data collection resources.
Data for use in hydrologic and hydrometeorological
analyses and models are the lifeblood of NWS river fore-
casts and flash flood guidance and warning products.
Sources of these data include stream gauges, precipitation
gauges, cooperative observers, flood warning systems,
satellite-relayed data, telemetered data and, most impor-
tantly, data from the NEXRAD network. But ownership of
these data sources is distributed across various federal, state,
and local government or private networks. Abrupt funding
changes and uncertainties cause some data sources to be
unstable, unreliable, or subject to short-notice curtailment
or elimination, sometimes with no apparent coordination or
consideration for the impact of their loss on NWS opera-
tions. It is essential that a shared ownership exist for the
nation's water management and flood warning infrastruc-
ture, lest this infrastructure lose its ability to meet growing
operational demands.
Strengthening the vitality of the surface-observing net-
works is also essential; the modernization of NWS hydrology
will be hindered without the real-time availability of stream
and rain gauge data from a larger number of locations.
PRODUCTS AND SERVICES
Recommendation 3-26. The NWS should continue to work
with the user community to determine community needs. In
particular, the NWS should focus on user concerns that may
develop in regions where political boundaries and basin
boundaries do not coincide. In addition, improved commu-
nication technologies should be employed to share data and
to disseminate warnings.
A service agency such as the NWS is known by the qual-
ity, relevance, and ease of access and use of its products.
Nowhere are these traits more critical than in river and flash
flood situations where lives and property are threatened
situations that often arise late at night and in rural areas. In
these situations, a forecast and warning system provides an
unacceptable level of service when the forecasts and warn-
ings are inaccurate or difficult to decipher or when they fail
to reach the population at risk. To achieve the dividends of
modernization requires that the NWS and its myriad of users
understand each other's needs, capabilities and responsibili-
ties, establish highly efficient telecommunication linkages,
and support or advocate mutually beneficial programs. The
NWS forecast and warning system can be fully effective only
if local communities accept responsibility to acquire and act
on the information.
PROG RAM RES PONS I Bl LITI ES AN D
PERCEPTIONS
Recommendation 4-1. The NWS must communicate the
objectives of the hydrologic and hydrometeorological as-
pects of the modernization program and progress that has
been made in the program more effectively to its employees
as well as to users of its services. In particular, the NWS
should ensure that responsibilities for the integrated hydrol-
ogy and hydrometeorology programs are clearly assigned
and understood at all levels of the NWS. Interdisciplinary
advisory or working groups such as the Service Hydrologist
Working Group could be essential intermediaries in this
communication process.
In its contacts with field office personnel, the committee
found considerable misunderstanding or distrust of modern-
ization activities relating to hydrologic and hydrometeoro-
logical functions, products, and services. In particular, the
benefits of the integration of certain hydrologic and meteo-
rological duties and responsibilities are neither clearly
understood nor readily accepted in many field offices.
These misunderstandings about roles and responsibilities-
particularly with respect to hydrometeorological duties-
need to be resolved at all levels of the organization.
AVAILABILITY OF ADVANCED WEATHER
INTERACTIVE PROCESSING SYSTEM
Recommendation 4-2. The AWIPS implementation pro-
gram should be expedited to enable NWS offices to exploit the
use of data from new technologies and to realize improve-
meets in the river and flash flood forecasts and warnings.
The AWIPS (Advanced Weather Interactive Processing
System) is essential for data collection, quality control, and
processing and telecommunication of hydrologic and hy-
drometeorological data. The AWIPS is essential to the inte-
gration of data, analyses, and models that enable improve-
ments in river and flash flood forecasting programs. De-
spite consistent efforts by the NWS, a variety of technical,
funding, and political setbacks have slowed the AWIPS de-
velopment and implementation program. At this point in
the modernization and restructuring, the absence of an
AWIPS is preventing full realization of the benefits of the
modernization program. As data from other new technol-
ogy systems have become available, the lack of AWIPS
workstation capabilities presents a bottleneck in data pro-
cessing and data integration that will result in less accurate
and timely warnings than would otherwise be possible with
the new work-station technologies.
RES EARC H AN D D EVEL0 PM ENT
Recommendation 4-5. The NOAA and the NWS should
develop a formal, long-term plan for hydrologic science
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EXECUTIVE SUMMARY
research that includes establishing priorities and is relevant
to flood and flash flood forecasting. The NOAA and the
NWS should request sufficient funding to implement and
sustain the research. The plan should be communicated to
field personnel so as to improve the overall NWS vision for
hydrologic services in the twenty-first century. In addition,
NWS headquarters should disseminate regularly to its field
offices updates on research and development activities, their
specific objectives, and timetables.
Considering its relatively small size, the NWS supports a
significant research and development program that has pro-
duced very useful results. For example, interactive hydrol-
ogy forecast applications such as the WHFS and the NWS
River Forecast System are quite innovative. However, rela-
tively little effort is under way on research issues related to
the scientific underpinning of hydrologic procedures and
models used in day-to-day operations.
The committee concludes that although a modest amount
of hydrology research is in progress or planned within the
Office of Hydrology, the overall objectives are unclear. Fur-
thermore, the priorities, relevance, and cohesiveness of those
research activities are lacking to some extent. In addition,
information on NWS research and development activities is
not received at field offices in a timely manner and often is
not considered credible by field office staff.
ADVISORY GROUPS
Recommendation 4-8. The NWS should use internal advi-
sory groups consistently throughout major planning, devel-
opment, test, and implementation phases of the hydrology
modernization program. These groups should include field
office members and be encouraged to advise NWS head-
quarters on matters relating to research and development,
operational test and evaluation, and overall modernization
implementation.
Early in the modernization planning, the NWS established
various working groups, consisting of field office and head-
quarters personnel, to review requirements and to develop
s
plans to improve products and services in hydrology and
hydrometeorology. The contributions of these groups are
seen almost universally as having been beneficial and effec-
tive in the establishment of a sound modernization program.
One or more similar advisory or working groups need to be
reestablished with respect to the hydrometeorological as-
pects of the modernization and restructuring. Such a group
could provide important feedback on data quality control,
forecast verification, hydrologic modeling, and precipitation
processing techniques.
QUALIFICATIONS
Recommendation 4-11. The NWS should review and, if
warranted, modify its qualification standards for hydrology
positions. The NWS should require a degree or extensive
formal education in hydrology for positions that involve a
hydrology emphasis.
Hydrometeorological personnel with duties that have a
meteorological emphasis are required to have an extensive
education in meteorology. However, those personnel that
have duties with a hydrology emphasis are not required to
have a comparable level of education in hydrology. NWS
forecasters with a degree or extensive formal education in
meteorology but no comparable training in hydrology usu-
ally are not qualified for hydrologist positions. A more sub-
stantial educational background in hydrology is necessary
for personnel working in such positions.
OUTL00K
Overall, the NWS hydrology program has taken a posi-
tive leadership role in the use of new observation networks
and in developing state-of-the-art interactive forecasting sys-
tems. To be sure, there are barriers that must be overcome-
financial, technological, operational, and organizational.
However, the committee is confident that if the changes rec-
ommended in this report are made, there is a high likelihood
that the hydrologic and hydrometeorological goals of the
modernization program will be achieved.
Representative terms from entire chapter:
hydrologic models
