ABRFC Implementation of
Advanced Hydrologic Prediction Service (AHPS)

The National Weather Service (NWS) is currently enhancing the existing suite of hydrologic products and services with the implementation of the Advanced Hydrologic Prediction Service (AHPS). AHPS is a national initiative that will provide users with many new services, such as short term to long term probabilistic forecasts, flood inundation mapping, and numerous graphical products that will be available via the Internet.

The Arkansas Red Basin River Forecast Center (ABRFC) has begun AHPS implementation in the headwaters of the Arkansas River in Colorado, with the intent of providing long range probabilistic forecasts. The project area includes the drainage area of the Arkansas River above Pueblo Reservoir. This area has many water management issues and with the use of probabilistic forecasts the users will be able to make more informed water management decisions.

To implement probabilistic forecasts, the River Forecast Centers (RFC) must calibrate and implement the Ensemble Streamflow Prediction (ESP) model. This model utilizes historical precipitation, temperature, and streamflow; forecasted precipitation and temperature from the Climate Prediction Center (CPC); and current conditions based on the National Weather Service River Forecast System (NWSRFS) model states. These data types are utilized within the ESP model to produce the probabilistic forecasts. The results from the ESP model are then utilized to create various graphics depicting the forecasts.

The ABRFC is currently in the historical data collection phase of this implementation. This phase is nearing completion and the next phase will be to recalibrate the NWSRFS model in Colorado to support the updating of our current ESP model. After obtaining reasonable calibration results, the ESP model will be reconstructed around the results of all the above steps.

ABRFC issues two types of probability plots: a weekly exceedance plot and a long-range exceedance plot. Each type of plot has three different graphics, one depicting stage, one for flow, and one for volume. Below are examples of both the weekly exceedance plot for flow and the long-range exceedance plot for flow at Cañon City, CO.

Figure 1. Weekly Exceedance Plot for Flow at Cañon City, CO	Figure 2. Long Range Exceedance Plot for Flow at Cañon City, CO

The ABRFC began implementing AHPS graphics for the project area in June 2002. The future AHPS implementation dates for the remainder of the ABRFC area are illustrated in the following graphic.

Figure 3. ABRFC AHPS Implementation Schedule