National Water Resources Outlook

The National Weather Service (NWS) is moving toward a national Water Resources Outlook (WRO) based on the Ensemble Streamflow Prediction (ESP) system. ESP has been around since the 1970s and has been used in the Western Region of the NWS for many years to assist in water supply forecasts. With the implementation of the Advanced Hydrologic Prediction Service (AHPS), River Forecast Centers (RFC's) have been issuing 30- to 90-day probabilistic hydrologic forecasts for river forecast points using the NWS River Forecast System (NWSRFS) ESP system for almost a decade now. However, there has been no national product of being able to see how streamflows are expected to change in the coming months similar to what the United States Geological Survey (USGS) has for real-time data.

In 2005, the Ohio River Forecast Center (OHRFC) developed a WRO based on USGS observed streamflow categories which is operational now. It uses current soil moisture states from the hydrologic model and short term quantitative precipitation forecasts (QPF) from the National Center for Environmental Prediction's (NCEP) Hydrometeorological Prediction Center (HPC), the Climate Prediction Center's (CPC) 6- to 10-day, 30-day and 90-day temperature and precipitation outlooks, and the day 1 to 7 temperature departures from normal, which are derived from the National Digital Forecast Database (NDFD).

In 2008, the NWS Western Region (WR) began developing a WRO based on percent of normal for the coming months. In late 2008, the OHRFC and WR methods were merged into a national format that is being expanded across RFCs. It is using Google GIS graphics combined with NWS forecast data for one to three months into the future. This merging of methods into a national product is being done based on a growing demand and positive feedback from many customers at the federal, state, local and private sector levels.

The goal of this national WRO is to provide a continuous water watch from past and present into the future months to assist a wide range of customers in decision making processes. It allows the customers to visually see and drill down into climate hydrologic forecasts. Significant upgrades and expansion of this product is expected as we work with our customers in 2010 and beyond. This project has support within the NWS as well as from our customers.