National Weather Service River Forecast System (NWSRFS)

The National Weather Service (NWS) River Forecast Centers (RFC) provide water resource and hydrologic forecast guidance to NWS Weather Forecast Offices (WFO) at important points along the rivers and streams in their area of forecast responsibility. The main hydrologic forecast tool used by the RFCs is the NWS River Forecast System (NWSRFS).

Figure 1. RFC and WFO areas of responsibility

The RFC Forecast Systems Group in the Hydrologic Research Laboratory (HRL) supports the RFCs through the design, development, testing, enhancement, implementation, and support of the NWSRFS. NWSRFS has 3 main components. They are:

Calibration System

The Calibration System (CS) is designed to allow the forecaster to determine model parameters for one forecast point. It runs the hydrologic models using historical data for many years for the forecast point. The user can then compare the historical observed and simulated streamflow and make adjustments to the model parameters to get the simulation to match the observed as best as possible.

Operational Forecast System

The Operational Forecast System (OFS) is used to provide short term (up to 30 days) streamflow forecasts. It uses the model parameters determined with the CS and real-time precipitation, temperature, snow, river gage, and reservoir data to produce short term forecasts.

Ensemble Streamflow Prediction System

Ensemble Streamflow Prediction (ESP) uses an ensemble technique to create probabilistic river stage forecasts for the mid-long term time frame. It uses the current state variables of the models determined by OFS and the historical time series for model inputs (precipitation, temperature, potential evaporation) to simulate streamflow for multiple forecast points.

Modernized Applications

In preparation for a part of the NWS modernization, the Advanced Weather Interactive Processing System (AWIPS), HRL has developed two applications to take advantage of the scientific workstation graphical environment. They are:

Interactive Forecast Program

The Interactive Forecast Program (IFP) is a graphical user interface for the OFS. It allows the user to select the area and dates to use in an OFS run and produces a graphical display of the model outputs. The user can use the run-time modification capabilities of OFS through the IFP to make adjustments and quickly rerun the models and display the results.

Interactive Calibration Program

The Interactive Calibration Program (ICP) is a graphical interface and display program that works with the CS. The ICP displays the observed and simulated streamflow values. In addition, it can display the detailed information about the state variables for the SNOW-17 and the Sacramento Soil Moisture Accounting models. The extra detailed output allows the user to better visualize what is happening in the models over time and determine reasonable parameter changes to be made. The parameters can then be easily changed, the calibration rerun, and results displayed.