The Weather Research and Forecasting (WRF) model contains two dynamic cores: the Non-hydrostatic Mesoscale Model (NMM – Janjic 2003) core (developed at the National Centers for Environmental Prediction (NCEP) and the Advanced Research WRF (ARW – Skamarock et al. 2005) core, developed at the National Center for Atmospheric Research (NCAR). Each dynamic core corresponds to a set of dynamic solvers that operates on a particular grid projection, grid staggering, and vertical coordinate. The WRF model also contains a multitude of physical parameterizations, many of which can be used with both dynamic cores. This paper presents a comparison of temperature and precipitation forecast verification statistics for the ARW and NMM obtained as part of the Developmental Testbed Center (DTC, Bernardet et al. 2008) 2007 13- km Core Test. The main goal of this study is to determine if the inter-core differences increase with forecast lead times. This study is a follow up to the DTC 2006 Core Test (Brown et al. 2007), which compared ARW and NMM for 24-h forecasts and found no remarkable superiority in either core. The ARW and NMM dynamic cores were used to forecast 120 cycles divided into the four seasons. The models were initialized every 36 h, resulting in alternating 00 and 12 UTC cycles. Details of the experiment configuration, results, and conclusions are presented in sections II, III, and IV, respectively.
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