OHD/HL - National Weather Hydrology Laboratory

The Implementation of an Interactive River Forecast System for the National Weather Service

1. INTRODUCTION

The National Weather Service River Forecast System (NWSRFS) has been used by NWS River Forecast Centers (RFC) since 1985 to provide daily river and flood forecasts for major rivers and streams throughout the United States. In preparation for one part of NWS modernization, the Advanced Weather Interactive Processing System (AWIPS) , the NWS Office of Hydrology (OH) has ported the NWSRFS from the current mainframe environment to a network of UNIX based scientific workstations.

In addition, OH has developed the Interactive Forecast Program (IFP) - a graphical user interface to the operational forecasting portion of NWSRFS. The IFP allows forecasters to control the NWSRFS program flow and to interact with a graphical display of model results to easily make necessary adjustments to help produce more accurate and timely forecasts. The first version of IFP was described by Page (1991) and has undergone major changes and enhancements since then.

The NWSRFS and IFP, along with other RFC hydrometerology applications developed for AWIPS, are currently implemented at most RFCs. This paper discusses their current implementation and the interaction of NWSRFS and IFP with some of these applications developed for AWIPS. Plans for further integration of NWSRFS and IFP into the evolving AWIPS environment are also presented along with their planned interaction with the Weather Forecast Office (WFO) Hydrologic Forecast System (WHFS) currently under development and testing.

2. BACKGROUND

The mission of the NWS includes providing river and flood forecasts and warnings for the protection of life and property and providing basic hydrologic forecast information for environmental and economic well being. The major responsibility for forecasting the Nation's major rivers and streams belongs to the NWS River Forecast Centers whose areas of responsibility cover the coterminous U.S. and Alaska. The RFCs pass their forecast guidance to the local Weather Forecast Offices (WFO). These WFOs are responsible for issuing all public forecasts for weather and hydrology. The areas of responsibility for these offices are shown in Figure 1.

Figure 1. RFC and WFO areas of responsibility.

3. PRE-AWIPS IMPLEMENTATION

The primary tool for producing the river forecasts at RFCs is the NWSRFS. The major components of a river forecast system are represented simply in Figure 2. There is a component to store and retrieve data, one to process the data into a form that can be used by the hydrologic models, one to perform the scientific calculations, and one to handle the output of the Figure 2. Functions of a river forecast system.

Figure 2. Models that represent the current and projected states of the river flow.

These functions have been available in NWSRFS in a mainframe environment at the NOAA Central Computing Facility (NCCF) since 1985. NWSRFS functions are run by sending command input over Remote Job Entry (RJE) lines to the NCCF. Line printer results are sent back to the RFC for display on standard printers or on text display screens. In the pre-AWIPS implementation of NWSRFS now available at most RFCs, a network of UNIX based scientific workstations allows the RFCs to do these functions locally (Figure 3).

Figure 3. Pre-AWIPS workstation network.

3.1 Data

Hydrologic modeling for streamflow and water resources forecasting depends on real-time data of the current and projected conditions. In the pre-AWIPS implementation, data from many different sources are collected and stored in a relational database management system (RDBMS). These sources include the modernized data sources of WSR-88D radar precipitation and the Automated Surface Observing Systems (ASOS) currently being installed. NWSRFS, as ported from the mainframe, has its own database based on flat files. The raw data is transferred from the RDBMS to the NWSRFS database by processes that also do some basic quality control.

3.2 Processing

Once the data is in the NWSRFS database it must be processed into a form that can be used by the hydrologic models. In NWSRFS, all data is passed between hydrologic models in time series format. This requires that all the raw data, which may have missing values and values gathered at different time intervals, be processed into regular time series. There are several preprocessors in the Operational Forecast System (OFS) component of NWSRFS that perform this function. In general, they take the raw data that is unevenly distributed in time and space, make estimates for missing data (where appropriate) based data on from surrounding stations, and time distribute the data. Many of the preprocessors also compute an areal average for the forecast watershed basins. OFS preprocessors include Mean Areal Precipitation based on precipitation gage estimates, Mean Areal Temperature, Mean Areal Potential Evaporation, and one to handle non-areal averaged data such as river, reservoir and snow data.

A recent addition to the preprocessors was one that calculates Mean Areal Precipitation based on WSR-88D radar precipitation estimates. This preprocessor uses the output of the StageIII Precipitation Processing Program, another of the modernized RFC applications, as its input. The use of the WSR-88D data for precipitation processing is described by Shedd and Fulton (1993).

The preprocessors are run automatically throughout the day as new data becomes available to update the input time series used for forecasting. The preprocessors are run as automated jobs requiring no user interaction.

3.3 Modeling

NWSRFS was designed to be a modular system that contains a variety of models and procedures and allows the user to control the selection of models and their order of use in a basin. In NWSRFS, the functions representing one scientific algorithm, such as a snow, soil moisture, or river routing model, are called an operation. An operation is a set of functions that performs actions on a time series. Generally, an operation describes the equations of motion governing the flow of water through a portion of the hydrologic cycle. There are also operations to display results or to perform utility functions such as adding two time series. Details on the design, development, and structure of NWSRFS can be found in Smith and Page (1993) and Page and Smith (1993).

Designers of NWSRFS realized that forecasting was inherently an interactive process because the models did not simulate the water movement perfectly, the calibration parameter values for the models do not produce perfect results, and the input rainfall, temperature, evaporation, and stream condition data were not perfect. Creating an effective interactive environment on the mainframe was a difficult task. Beginning in 1989, the OH began a project to prepare for the AWIPS local processing environment. The computational and graphical capabilities of the scientific workstations led to the development of the Interactive Forecast Program (IFP).

In the operational pre-AWIPS setting, the IFP allows forecasters two major advantages over the mainframe environment. First is the ability to control the forecast run and to view the output much faster and easier than on the mainframe. The model output displays in IFP on the workstation are graphical and color coded rather than text file output which makes it easier for the forecaster to read and analyze.

The second major enhancement IFP brings is the ability to easily create the run-time modifications to correct bad data values, change certain model state variables, etc. to improve the forecast simulations. The mechanism for making these modifications is a feature of OFS. In the mainframe environment, typing in the command input, sending it through RJE, and waiting for the line printer output to see the results often took too long to do many iterations in a forecast cycle. With IFP, modifications are made with mouse interactions on the graphical displays and the hydrologic models are rerun at the click of a button so results of changes can be displayed in seconds. The RFC forecaster can concentrate on the scientific basis of the proposed modifications, not the mechanics of typing in changes. The better the forecaster can identify and correct the sources of error in the simulations, the more model state variables will reflect the current conditions. For well calibrated basins, this translates into better forecasts.

As currently implemented in the pre-AWIPS environment, the forecast program that actually performs the river forecasting computations can be run through a batch run or through IFP. Either way, run-time modifications made through IFP are incorporated into the forecasts.

Other NWSRFS/OFS programs allow forecasters to specify the characteristics of the data stations and to configure the basins, choosing the models to be run and the parameters needed for them. These programs are run in batch mode and all the parametric information is currently stored in the NWSRFS database. All time series that result from the preprocessors and those used in the forecast component of OFS are also stored in the NWSRFS database.

3.4 Output

As mentioned earlier, in the NWS, the responsibility for producing the public forecast products is reserved for the local WFO. Therefore, the RFCs must get their river forecast information to the WFOs in their area of responsibility.

In the mainframe environment, the production of the river guidance products requires that the forecaster pick off the values from the printed output, type in the message, and send it to the current NWS communications network - AFOS (Automated Field Operations and Services).

In the pre-AWIPS workstation implementation, the preparation of river forecast information is automated with the interactive Standard Hydrologic Exchange Format (SHEF) Encoded Time Series program (SETS) which was developed at the Arkansas-Red Basin River Forecast Center . SETS allows the forecaster to choose the forecast points for which to produce the river information. Either daily or flood forecasts can be generated. SETS retrieves the latest observed data from the RDBMS and the forecast time series data from the OFS database. These data are formatted into a SHEF forecast product. The forecaster then has the opportunity to edit the message to add additional information if needed. The forecasts are then sent via AFOS to the WFOs.

4. PLANS FOR AWIPS IMPLEMENTATION

One of the major components of the modernization of the NWS is the Advanced Weather Interactive Processing System (AWIPS). This system will provide a local network of UNIX based scientific workstations to all RFCs and WFOs. It will also provide a state-of-the- art communications network connecting all NWS offices to replace the current overloaded AFOS network. Finally, it will provide (1) a common database structure to hold all observed, forecast, and parametric data needed for forecasting weather and streamflow, (2) tools to assist in the development of local applications, and (3) a common user interface environment consisting of interactive forecasting tools for RFCs and WFOs.

4.1 NWSRFS and IFP Integration into AWIPS

The NWSRFS and IFP are two of the major RFC applications that will be included in AWIPS. In order to fully integrate them into AWIPS, they are undergoing some changes. NWSRFS, in its current implementation, has its own custom database for the observed, processed, and parametric data. The AWIPS database will be designed to store all of these data in a more standard RDBMS. As a result, the NWSRFS database access routines are being rewritten to be able to read and write to the AWIPS database.

The IFP uses the same database access routines as NWSRFS so IFP will also be able to read and write to the AWIPS database. In addition, AWIPS applications are designed to have a similar graphical user interface and be integrated into a common framework. This is to help forecasters easily move between applications needed to produce their forecasts and maintain the system. IFP was written before there was an AWIPS framework, therefore, for full integration into AWIPS, IFP will be ported to the AWIPS structure as it becomes available.

4.2 RFC-WFO Interaction in AWIPS

In the modernized NWS, the hydrologic services program will rely on a much closer coordination between the RFCs and WFOs for hydrologic data and products. NWSRFS has been available to RFCs since 1985 but there has been no similar forecast system available at all WFOs. Several different modeling tools have been in use at different WFOs. The OH is currently developing and testing a WFO Hydrologic Forecast System (WHFS) (Shelton and May, 1996) that is designed for use by all WFOs in AWIPS.

WHFS currently includes an integrated environment which provides a database maintenance tool, a data viewer application, a system for modeling flash flood areas, and an application for automatically generating the public hydrologic forecast products. The system is currently being tested at a several sites.

Two of the applications in the WHFS are designed so that they can also be used at an RFC. The first is the database maintenance tool, Hydrobase, which allows forecasters to easily look at and update the static data stored in the RDBMS such as station, flood stage, and rating curve information. The second is the HydroView application which allows forecasters to graphically display observed and forecast data fore all stations and forecast points in the area of responsibility. Since the same information is needed at both the WFO and RFC it makes sense that they both utilize the same applications to view and update data. The major difference will be that the RFC database will contain information from all the WFOs in their area. Also, the RFC and WFO will have a common database structure so an update to information in one database can trigger an update in the other. An example of this would be adding a new station to the database. The service hydrologist at the WFO would enter the information in the WFO database and it would automatically be added to the RFC database and available for use. This reduces the effort required at the two sites to keep their data updated and eliminate the possibility of different sites using different data.

The ability to update other databases is important when considering the close coordination needed for the forecast modeling system in WHFS. In addition to disseminating the normal RFC river and flood forecasts to the public, WFO s have the responsibility for producing hydrologic forecasts for flash flood areas.

The modeling system in WHFS is based on NWSRFS. It will be the responsibility of the RFC to make runs for these areas at least once a day and to transfer the values of the state variables of the models to the WFO database so model runs at the WFO will have the most current conditions. In addition, the RFCs will assist in model calibration for these areas and transfer the parameter values to the WFO. This cooperation is possible because the RFC and WFO will be able to use the same hydrologic models.

Finally, the river forecast guidance products will be generated at the RFC in a manner similar to the pre-AWIPS implementation, using SETS. These will be sent to the WFOs where the river product formatter component of WHFS, RiverPro, will use the time series information to produce and disseminate the final public river or flood forecast.

5. CONCLUSIONS

AWIPS is scheduled to begin installations in late 1996 and be fully deployed to all NWS offices by early 1999. Until then, the pre- AWIPS implementations of NWSRFS and IFP and other RFC applications will be used at the RFCs. In addition, work will continue to port these applications into the evolving AWIPS environment and to integrate them with the WHFS. The AWIPS environment will allow all current and future hydrologic forecasting applications to be more consistent and better coordinated and improve the hydrologic services provided by the NWS.

6. REFERENCES

Page, D., 1991: The interactive NWS river forecast program. Seventh International Conf. on Interactive Information and Processing Systems for Meteorology, Oceanography, and Hydrology, New Orleans, LA, Amer. Meteor. Soc., Jan. 14- 18, 1991, 306-312.

Page, D., and G.F. Smith, 1993: National Weather Service operational river forecasting in a UNIX environment. Engineering Hydrology: Edited by Kuo, C.Y., ASCE, 838-843. Shedd, R.C. and R.A. Fulton, 1993: WSR-88D Precipitation processing and its use in National Weather Service hydrologic forecasting. Proceedings of the International Symposium on Engineering Hydrology, San Francisco, CA, ASCE, July 25-30, 1993.

Shelton, D.R. and E.L. May, 1996: Modernized hydrologic forecast operations at National Weather Service Weather Forecast Offices . Twelfth International Conference on Interactive information and Processing Systems for Meteorology, Oceanography, and Hydrology, Atlanta, GA, Amer. Meteor. Soc., 28 Jan.-2 Feb. 1996.

Smith, G.F. and D. Page, 1993: Interactive forecasting with the National Weather Service River Forecast System. Conf. Proceedings of the Third National Technology Transfer Conference, Baltimore, MD, Dec 1-3, 1992, NASA Conference Publication 3189, Vol. 1, 527-536.

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