The Evaluation of Quantitative Precipitation Forecasts at WFO Reno, NV

The Evaluation of Quantitative Precipitation Forecasts at NWSFO Reno, NV

Quantitative Precipitation Forecasts (QPFs) are critical to the National Weather Service (NWS) river flood forecast program. QPFs are used to generate mean areal precipitation (MAP) values, which are fed into River Forecast Center (RFC) streamflow simulation models to produce advanced, short-range river flood forecasts and warnings. These have a tremendous economic impact on the Nation's economy and represent a critical component of the NWS mission.

The NWS QPF program has changed through the years to satisfy public necessity. The Hydrometeorological Prediction Center (HPC) has produced manual QPFs covering the continental United States since 1960. RFCs pioneered the use of QPFs for operational river and flood forecasting. Over the past few years, NWS forecast office (NWSFO) generated QPFs have

been incorporated into the river forecast process. NWSFO produced QPFs utilize a superior knowledge of local meteorologic and hydrologic variables. These are especially important in the Western U.S., where terrain so heavily influences precipitation amounts.

Improving QPF accuracy is one of the top NWS priorities. The NWS would like to develop national, uniform QPF and QPF verification programs (The Modernized End to End Forecast Process for Quantitative Precipitation Information, 1/99) to produce more efficient, accurate and useful QPF products.

NWSFO Reno has been issuing QPFs since the 1980s. Initially, 12 hour QPFs were issued for Truckee, CA and Woodfords, CA. These sites were chosen because of their location close to the headwaters of the Truckee and Carson Rivers. With the implementation of Mountain Mapper software, the number of QPF sites issued by NWSFO Reno increased to five during the 1997-1998 season. For these five sites, six hour QPFs were issued out to 72 hours.

Mountain Mapper software incorporates climatology and high resolution terrain into the QPF process. It is accepted as the standard for generating and verifying QPFs, in addition to data quality control, for all Western Region NWSFO offices. The software provides a medium for an in depth analysis of the performance of NWSFO generated QPFs.

This paper will examine the history of the QPF program at NWSFO Reno, NV. Challenges to QPF accuracy, especially complex terrain and data availability, will be discussed. QPF Verification statistics for the 1998-1999 season will be presented and examined for overall usefulness. Future ambitions of the QPF program at NWSFO Reno will be discussed. The paper will also discuss QPF program modification to meet regional and national goals.