Evaluation of the NCEP WRF NMM and ARW models for some recent high-impact weather events

At the last Weather Analysis and Forecasting/Numerical Weather Prediction Conference in Washington, D.C. in the summer of 2005 a number of presentations were made on the Developmental Testbed Center (DTC) Winter Forecast Experiment (DWFE), conducted during the winter of 2005. The goal of that experiment was to run and evaluate two versions of the WRF model at high resolution (5 km horizontal grid resolution) on the CONUS scale, and distribute the output in real-time to National Weather Service (NWS) forecasters. Evaluation of the DWFE models by forecasters was generally quite positive, and the overall success of the effort prompted the National Centers for Environmental Prediction (NCEP) to announce, during the conference, that they would start running the two models again on a daily basis. This has been done now for over a year, with 5-km horizontal grid resolution versions of the WRF NMM and WRF ARW models run in four different sub-CONUS windows, each once per day. A set of graphics is distributed via the NCEP web page at http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/.

In this paper we will examine the performance of these models for several high-impact weather events during the winter season. Our focus will be on precipitation forecasts for the two major storms that plastered Colorado and nearby states either side of the Christmas holiday in late 2006, resulting in major travel delays and other critical impacts. Other high-impact winter storms in areas outside of Colorado during the 2006-2007 winter will also be examined. A companion paper (Wesley et al.) will examine the guidance from the operational models for the Colorado events. For events considered outside of Colorado we will include such comparisons with the conventional NAM and GFS operational forecast models in this paper, specifically to determine whether the high-resolution models provided improved guidance for operational forecasters.