The Hydrometeorological Prediction Center—Restructuring Its Products and Services for the 21st Century

The HPC (Hydrometeorological Prediction Center), a service center of NCEP (the National Centers for Environmental Prediction), has been providing quantitative precipitation forecasts, excessive rainfall outlooks, and heavy snow guidance to National Weather Service (NWS) Weather Forecast Offices (WFOs), other federal and state agencies, the media, and the general public for over 25 years. Throughout this period the HPC has strived to be a "Center of Excellence" in those areas.

Recent events within the National Weather Service have focused attention on the HPC and the products and services it provides. One such event was to transfer from the WFOs to the HPC the responsibility of issuing Quantitative Precipitation Forecasts (QPFs) to support the NWS River Forecast System (NWSRFS), operated by the 12 River Forecast Centers (RFCs) in the conterminous U.S. To implement this decision, the HPC has made major changes to its QPF product suite. Not only has the HPC extended its 24-h QPFs out through Day 3, it also now generates 6-h forecasts through Day 3. Forecasts transmitted directly to the RFCs indicate forecaster confidence. Confidence is indicated as above or below average for amounts greater than one-half inch in 6 h to help the RFCs decide whether to use the forecasted amounts or not.

All QPFs issued by the HPC are verified and have been for many years. This provides an unparalleled set of statistics to monitor the progress made in precipitation forecasting over the past 25 years. Examples of HPC QPF products and a brief review of its QPF verification scores with respect to the operational numerical models will be presented. These results indicate that to capture better the inherent uncertainty in the QPFs, probabilistic QPFs are needed in tandem with probabilistic stream flow predictions.

With the decision to have HPC be the primary unit in the NWS providing QPFs to the RFCs, HPC is responsible for the QPFs for land-falling hurricanes. The HPC participates in twice daily briefings to FEMA during those times when hurricanes or tropical storms threaten U.S. land-fall.

In 1999 the HPC began issuing a probabilistic heavy snow and icing outlook through 24 h four times daily and out through 48 h twice daily. The product depicts areas of low, moderate, or high confidence of greater than 4 inches of snow accumulation and/or one-quarter inch of ice accretion in 12 h or 6 inches of snow/quarter-inch ice in 24 h. HPC forecasters specify confidence factors based upon a combination of forecaster experience, NWP guidance, and application of five independent algorithms using derived model soundings that indicate precipitation type. Verification results from this first year's effort will be presented.

With the new streamlined NWS QPF process, the HPC can now be considered a point of entry for transferring technology into operations. Thus the HPC is looking forward to working with the research community to improve the science of QPF, and hopes that research results can be quickly adapted to operations.