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OCR for page 9
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
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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,
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BA CKGRO UND
11
not only through the technologies themselves, but also
through an increased emphasis on hydrometeorology. These
services will benefit from changes in hydrologic and meteo-
rological operations to make better use of improved hydro-
meteorological data and forecasts, processing and commu-
nications capabilities, and hydrologic modeling procedures.
Hydrometeorological Service Operations
The accuracy and usefulness of river forecasts derived
from RFC operations are expected to improve substantially
through more frequent updating of guidance products, de-
velopment and calibration of new forecast procedures, and
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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.
OCR for page 13
BA CKGRO UND
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OCR for page 14
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
OCR for page 15
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.
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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.
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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.
Representative terms from entire chapter:
forecast center
